A critical analysis on weld s distortion

INTRODUCTION

Weld distortion refers to the warping of components caused by the expansion and contraction of the weld material and surrounding base metal during the heating and cooling phases of welding There are six distinct types of weld distortions, each characterized by unique deformation shapes, as illustrated in Figure 1.1 The mechanisms behind these distortions will be discussed in the following sections.

When a material is heated, it undergoes thermal expansion, which is directly related to the temperature change (∆𝑇) and the coefficient of thermal expansion (𝛼) During welding, the heat used to melt the weld metal or generated from friction in Friction Stir Welding (FSW) is unevenly distributed, creating non-linear temperature fields throughout the heating and cooling phases This results in temperature gradients between the top and bottom surfaces of the plate, leading to non-uniform thermal expansions and subsequent deformation in the weld zone (FZ) and heat-affected zone (HAZ) The residual plastic strains that persist after the thermal cycle result in permanent deformation, commonly known as weld distortion.

The six types of distortions displayed in Figure 1.1, are all related to the weld shrinkage stresses The transverse and longitudinal shrinkage types occur when the

Figure 1.1 - Different types of weld distortions Arrows indicate the weld metal’s shrinkage direction which causes the corresponding distortion (Soul & Hamdy 2012)

A Critical Analysis of Weld’s Distortion

Shrinkage forces during welding can be categorized as perpendicular and parallel to the weld bead, leading to various types of distortions Angular distortion arises from non-uniform shrinkage forces through the thickness, creating a resultant force at the weld metal’s centroid, which, if misaligned with the base metal’s centroid, results in a bending moment that warps the plate Bending distortion shares similar causes with angular distortion but is defined by longitudinal shrinkages in relation to the base metal’s longitudinal cross-section Additionally, rotational distortion is characterized by in-plane angular distortions caused by localized thermal expansion and shrinkage Lastly, buckling, unlike other distortion types, lacks a specific shape and is primarily caused by compressive residual stresses, typically found around the fusion zone.

The magnitude of buckling distortion in structures is influenced by bending stiffness, which diminishes under compressive stresses, leading to various buckling modes, each exhibiting distinct shapes (Bhide et al 2006) Figure 1.3 illustrates four different buckling modes of flat plates Numerous studies highlight the existence of a critical buckling stress in structural components (Michaleris and Debiccari 1997, Tsai et al 1999, Deo et al 2003, Bhide et al 2006, Conrardy et al 2006, Deng and Murakawa).

The critical buckling stress of a flat plate can be calculated using a specific formula, where k represents a constant, E denotes Young’s Modulus, v is the Poisson’s ratio, b indicates the plate's width, and t signifies the plate's thickness (Narayanan et al., 1999).

Figure 1.2 – Development of angular distortion in butt welding of a single “V” Groove A – Centroid of the weld metal; B – Centroid of the transversal cross-section; F – Transverse shrinkage forces (in blue); RF –

Resultant shrinkage force (in gray)

Weld stresses that lead to distortion can be categorized based on three characteristics: lifetime, direction, and origins Regarding lifetime, these stresses are classified as either temporary or residual Temporary weld stresses occur during specific moments of the welding thermal cycle, whereas residual stresses persist in a material or structure after manufacturing and processing, even in the absence of external forces or thermal gradients (Soul and Hamdy 2012).

Weld stresses can be categorized based on direction and origin By direction, they are classified as longitudinal or transversal, referring to stresses that are parallel or perpendicular to the welding direction By origin, weld stresses can be thermal, arising from plastic deformation due to temperature changes, or phase transformation stresses, which occur from an increase in the metal's volume resulting from phase transformation.

The magnitude of residual stresses in welding is influenced by welding constraints and plate geometry, while weld shrinkage is primarily affected by the heat input during welding Both weld stresses and shrinkage are contingent on welding parameters When thermal expansion of the heated material is restricted by cooler metal areas or restraints, weld distortion decreases but thermal stresses increase, remaining in the material post-cooling During the welding process, as the filler material is deposited, the fusion zone (FZ) forms, initially exhibiting zero longitudinal stresses due to low yield strength at high temperatures Surrounding regions experience temporary compressive stresses, while areas further from the arc show tensile stresses due to thermal restraint As the temperature decreases, shrinkage stresses develop in the weld and nearby areas, leading to high tensile stresses that are balanced by compressive stresses in distant regions Although friction stir welding (FSW) does not create a fusion zone, the distribution of residual stresses remains similar to that in arc welding, with tensile residual stresses present in the weld.

4 2015 the TMAZ, while the areas surrounding it exhibit compressive residual stresses (Bhide et al 2006)

This article analyzes the factors influencing weld distortion by reviewing various sources, including articles, books, websites, and theses The examined documents contain both numerical simulation data and experimental results While experimental data provides clear outcomes, numerical simulations have demonstrated accuracy and can be utilized in scenarios where experiments are impractical or challenging to conduct.

Figure 1.3 – Image displaying the four smallest buckling modes, obtained via buckling analysis of four flat plates ("Linear Buckling" 2011)

WELD DISTORTION FACTORS

Structural Parameters

This article examines the structural parameters that affect weld distortion, focusing on the plate's geometry, weld groove design, and joint type The study analyzes how each of these factors influences weld distortion in both steel and aluminum alloys.

Plate thickness remains a primary concern in weld distortion, making it a focal point in distortion-related studies However, other significant geometric factors, including plate width, length, and the presence of stiffeners, also play a crucial role As illustrated in Figure 2.1, seven articles examine the effects of both plate thickness and width on two different types of joints.

Figure 2.1 – Diagram containing the articles read for subchapter 2.1.1 arranged by analysed factors and joint type

Research indicates that for a specific plate thickness, weld shrinkage force is primarily influenced by welding conditions rather than panel width Wider panels enhance structural rigidity and reduce residual compressive stresses around the fusion zone post-cooling, leading to lower distortion levels (Tsai et al 1999, Deo et al 2003) While critical buckling stress remains unaffected by weld shrinkage, it decreases with increasing plate width and length, as noted by Deo et al 2003 Conversely, Tsai et al 1999 found that bending distortion rises with plate length Both studies agree that critical buckling stress increases with plate thickness, a finding also supported by Deng and Murakawa 2008 Additionally, there exists a "buckling critical thickness," below which buckling distortion is likely to occur, depending on joint type and plate width.

The influence of plate thickness on weld distortion remains a topic of debate among researchers, with no clear consensus Some studies indicate that thicker plates create a greater through-thickness temperature gradient, while also enhancing structural rigidity, which ultimately helps to minimize final weld distortion (Tsai et al.).

Research indicates that thicker plates can reduce the transverse shrinkage of weld metal, following the principle that shrinkage is inversely proportional to the square of the thickness While Deng and Murakawa (2008) argue that increased thickness results in greater angular distortions due to elevated thermal gradients, Masubushi (1980) offers a nuanced perspective, identifying an optimal thickness at which angular distortion peaks for both Butt and T-fillet joints Below this peak thickness, a more uniform temperature distribution occurs, minimizing thermal gradients and angular distortion Conversely, above the peak thickness, although thermal gradients increase, enhanced structural rigidity leads to a reduction in angular distortion.

Regarding residual stresses, Teng et al 2001 concluded that thicker plates provide stronger internal restraints and increase the residual stresses

2.1.2 Weld groove geometry and Joint type

Weld groove geometry significantly impacts weld distortion, as variations in joint type, groove angle, and depth alter the amount of weld metal used Additionally, the centroid distance of the weld metal from the cross-section neutral axis changes with different groove geometries, further influencing final distortion Consequently, distinct shrinkage values arise from varying groove shapes Figure 2.2 presents eight articles that explore the relationship between weld groove shape and distortion, with most focusing on steel, while only Cheng’s research investigates aluminium alloys.

Numerical simulations indicate that the shape of the weld groove significantly affects the distribution of residual stresses in thicker plates Specifically, plates welded with an "X" groove exhibit higher tensile residual stresses in the fusion zone and greater compressive residual stresses in the heat-affected zone, resulting in less distortion compared to those welded with a "V" groove Additionally, while "U" shaped groove welds require more weld metal than "V" shaped grooves, they also influence the stress distribution differently.

“U” shaped groove approaches the centroid of the weld from the neutral axis of the plate,

Figure 2.2 - Diagram containing the articles read for subchapter 2.1.2 arranged by analysed weld groove shape

Research indicates that the groove shape in aluminum alloy welding significantly affects weld distortion and residual stresses A study by Cheng et al (2005) illustrates the angular distortion of three non-restrained aluminum alloys across four different weld groove angles Veiga et al (2002) and Sattari-Far and Farahani (2009) found that both “V” and “U” shaped grooves yield similar residual stress outcomes However, Akbari Mousavi and Miresmaeili (2008) demonstrated that welding with a “U” shaped groove results in lower residual stresses compared to a “V” shaped groove.

The preparation angle of a weld groove significantly influences angular distortion, with wider weld pools resulting in increased shrinkage forces during welding Research by Cheng et al (2005) and Vasantharaja et al (2012) indicates that welding an unrestrained plate without a groove shape leads to reduced angular distortions Specifically, Cheng et al found that a 60º "V" shaped groove angle results in the lowest angular distortion among various groove shapes Similarly, Bachorski et al (1999) demonstrated that a 50º "V" groove angle also exhibits lower angular distortions compared to other angles Additionally, experiments by Akbari Mousavi and Miresmaeili (2008) concluded that a 50º "V" groove minimizes residual stresses Figure 2.3 illustrates the weld distortion results from Cheng et al while welding three different aluminum plates with varying "V" groove angles and a control without any groove.

The last hereby analysed weld groove characteristic is the weld groove depth

Adjusting the weld groove depth can yield various weld bead profiles while maintaining a constant laser power Research indicates that although angular distortion typically rises with increased groove depth, there exists an optimal depth that minimizes this distortion Deviations from this optimal value, whether higher or lower, lead to increased angular distortions due to the balance between shrinkage force and bending momentum lever-arm (Bhargava et al 2014) Figure 2.4 illustrates the angular distortions observed by Bhargava using three different chamfer depths alongside a flat edge.

Figure 2.4 - Graphic portraying different angular distortions obtained with various chamfer depths (Bhargava et al 2014)

Material Properties

The mechanical and thermal properties of base metals play a crucial role in weld distortion, with key factors including yield strength, Young’s Modulus, thermal expansion coefficient, thermal conductivity, and specific heat, collectively termed as thermo-mechanical properties Research highlighted in eleven articles, as shown in Figure 2.5, examines how these properties affect weld distortion in both steel and aluminum alloys, particularly focusing on the influence of base metal phase transitions.

2.2.1 Base Metal Thermo-mechanical properties

Young's Modulus is a key indicator of a material's rigidity, which diminishes with rising temperatures It plays a crucial role in determining the buckling critical stress (Masubushi 1980) Various analyses suggest that utilizing the Young's Modulus value at room temperature is essential for accurate numerical simulations in welding applications.

Figure 2.5 - Diagram containing the articles analysed in subchapter 2.2, arranged by type of analysis performed regarding material properties

Filipe David Santos Cordeiro 11 distortion, yields good results when compared to experimental data, for both steel and aluminium alloys (Masubushi 1980, Zhu and Chao 2002, Bhatti et al 2015)

The yield strength of materials decreases with increasing temperature, and using a constant value for this property in numerical simulations of steel and aluminum can lead to discrepancies with experimental data At elevated temperatures, excessively high yield strength prevents thermal strains from causing plastic deformations, resulting only in elastic strains Furthermore, yield strength plays a more critical role in weld distortion for high-strength steels compared to mild steels, as high-strength steels exhibit greater distortion resistance Experiments with three aluminum alloys revealed that weld metal shrinkage stresses and distortions rise with the base metal's yield strength at high temperatures Similar findings were noted in studies of angular distortion across different steel grades.

The thermal expansion coefficient measures how much a material expands when heated, with higher coefficients leading to increased shrinkage stresses during cooling (Masubushi 1980) This coefficient varies significantly between steel and aluminum alloys but remains relatively consistent across different steel grades Numerical simulations indicate that both temperature-dependent and room temperature thermal expansion coefficients yield results closely aligned with experimental data for both steels and aluminum alloys (Zhu and Chao 2002, Bhatti et al 2015).

This article examines the thermal properties of materials, focusing on thermal conductivity and specific heat, both of which slightly increase with temperature Thermal conductivity measures a material's ability to conduct heat, and higher values lead to more uniform heat distribution across the plate's thickness and width, thereby reducing thermal gradients that cause shrinkage.

Reducing stresses can significantly decrease weld distortion, as noted by Masubushi (1980) and Liu et al (2011) Heinze et al (2012) found that weld distortions are highly sensitive to thermal conductivity, with numerical simulations of steel and aluminum showing that room temperature thermal conductivity values align closely with experimental data Therefore, thermal conductivity is regarded as the most critical material property in the thermal analysis of aluminum alloys (Zhu and Chao 2002; Bhatti et al 2015).

Specific heat is defined as the heat capacity per unit mass of a material, indicating the amount of heat required to change its temperature by 1ºC A higher specific heat value means more heat must be transferred to increase the material's temperature, which in turn reduces the peak temperature during welding (Masubushi 1980) According to Bhatti et al (2015), shrinkage forces are directly proportional to the peak temperature of the plate In thermal analysis of steels, specific heat is a crucial material property, and using temperature-dependent specific heat values is essential for achieving numerical simulation results that align closely with experimental data (Bhatti et al 2015).

The phase transition effect significantly influences residual stresses and distortions in various steel grades, as the peak temperature attained and the cooling rate of the metal lead to varying martensitic fractions across different steel types.

Numerical simulation studies indicate that phase transformation has minimal impact on distortion in low carbon steels, while it significantly affects distortion in mid and high carbon steels When the cooling rate is rapid, the face-centered cubic structured Austenite transforms into body-centered tetragonal structured Martensite, resulting in an increase in total material volume This volume increase partially counteracts transverse shrinkage, thereby reducing weld distortion in mid and high carbon steels and generating compressive stresses in the material.

FZ, reducing the residual stresses for mid and high carbon steels The authors mention that

Filipe David Santos Cordeiro (2013) notes that an increase in volume leads to plastic strain on the plate, a factor overlooked by several authors (Deng 2009, Kala et al 2014) Research indicates that completing phase transformation at lower temperatures results in reduced angular distortion (Howes et al 2002, Bhadeshia 2004, Deng 2009).

Research by Zain-ul-abdein et al (2011) indicates that in aluminum alloys, the extent of distortions during solid-state phase transformations remains consistent regardless of precipitation or dissolution events However, the nature of these distortions varies Additionally, phase transformations in aluminum alloys play a significant role in alleviating residual stresses.

Weld metal phase transformation significantly impacts distortion, with studies indicating that using wires with lower martensitic transformation starting temperatures reduces angular distortion compared to standard wires This is attributed to an increased formation of martensite early in the welding process Once the transformation finish temperature is reached, the distortion stabilizes, demonstrating a clear correlation between the onset of weld metal expansion and the reduction of angular distortion As the transformation ceases, so does the angular distortion (Mikami et al 2009).

Wires containing a higher percentage of nickel have been shown to enhance Martensite formation without significantly affecting angular distortion values Additionally, these wires effectively minimize bending distortions by reducing longitudinal shrinkage stresses.

Manufacturing Parameters

The significance of manufacturing parameters on weld distortion can be categorized into Welding Parameters and Welding Procedures Welding Parameters encompass factors such as electric current intensity, electric voltage, welding speed, and shielding gas flow, all of which influence weld distortion Meanwhile, Welding Procedures consider constraints, welding sequence, and the type of heat source, which also play a crucial role in affecting weld distortion.

The longitudinal shrinkage, transverse shrinkage and weld distortion increase with the heat input Furthermore, buckling propensity also increases with heat input (Deng

2013).However,Venkatesan et al 2013 states the following:

“It is observed that, the process parameters have strong influence over bead profile and bowing distortion rather than heat input.”

Where the mentioned process parameters correspond to the aforementioned welding parameters

Experiments performed by Venkatesan et al 2013; 2014 and Narang et al

Increasing electric current intensity leads to higher bending distortions, but when paired with increased welding speed, it enhances joint penetration, counteracting shrinkage effects and reducing distortion Tian et al (2014) support Venkatesan et al (2013) only at high welding speeds, noting that lower speeds result in decreased angular distortion with increased current intensity Both studies agree that higher electric current raises heat input and bead width, consequently increasing shrinkage Additionally, Venkatesan et al (2013) confirm that increased penetration is supported by Mostafa and Khajavi (2006), who observed melting of a larger base metal volume and reduced droplet size.

Filipe David Santos Cordeiro 15 increased momentum, along with the enhanced arc force have a strong influence on penetration

Increasing voltage significantly raises the heat input to the base metal, resulting in wider beads and increased taper, which leads to greater shrinkage and higher bending distortion (McGlone, 1978; Venkatesan et al., 2013; 2014) Venkatesan et al also conducted an interaction experiment between voltage and welding speed, confirming that their findings are applicable at high welding speeds Similarly, Tian et al (2014) supports this conclusion for high welding speeds, while noting that at slower welding speeds, higher voltage reduces bending distortion.

Research by Tian et al (2013, 2014) indicates that weld shrinkage increases with higher electric voltage Their studies reveal a significant relationship between electric voltage and current effects on distortion, highlighting that low electric current intensities result in considerable angular distortion when voltage is increased Conversely, at high electric current intensities, low voltage values can lead to significant angular distortions, while increasing the voltage in this scenario helps to reduce the distortion.

Research by Mostafa and Khajavi (2006), Deng (2013), Venkatesan et al (2013; 2014), and Narang et al (2014) indicates that lower welding speeds lead to increased distortion and shallow weld beads with reduced penetration due to the cushion effect of the molten pool, which supports the weld metal droplets on the surface (Rausch, 2015) Conversely, increasing the welding speed initially reduces bending distortion until a minimum point is reached, after which further increases in speed result in greater bending distortions This relationship is supported by the angular distortion equations provided by Pilipencko (2001) and Watanabe and Satoh (1961), which incorporate variables such as electric current intensity (I), electric voltage (U), welding speed (v), plate thickness (h), and constants (m, C1, and C2).

Increasing the shielding gas flow rate has been shown to reduce bending distortion in welding, as evidenced by Venkatesan et al (2013), who noted that higher CO2 flow rates enhance welding penetration Similarly, Banarjee (2005) found that a greater flow of shielding gas increases the number of CO2 molecules, leading to higher heat input from the recombination of CO with monoatomic oxygen at the arc temperature, resulting in larger weld beads Kurihara et al (2004) confirmed that heat input consistently rises with increased shielding gas flow rate, regardless of the gas type Additionally, Lancaster (1984) highlighted that the shape of the weld pool is influenced by both the type and flow rate of the gas used in the arc column.

Venkatesan et al (2013; 2014) investigated the interaction effects of gas flow rate with electric voltage and current intensity, revealing that increasing voltage reduces bending distortion at high gas flow rates due to enhanced weld penetration This effect mitigates the wider bead and higher heat input typically associated with elevated voltage and gas flow Conversely, they found that increasing electric current intensity leads to greater bending distortion across all gas flow rates, although this distortion is less pronounced at higher gas flow rates Experimental results are illustrated in Figure 2.6, which presents the relationship between bending distortion and various factors, including electric current intensity, voltage, welding speed, and shield gas flow rate.

In what concerns to arc length, Mostafa and Khajavi 2006 and Narang et al

2014 concluded that by increasing the arc length, the welding penetration increases and weld distortion decreases However, Narang et al 2014 results show increased distortion

Filipe David Santos Cordeiro 17 highlights that for longer arc lengths, an increase in the electrode to plate angle from 90º to 120º enhances welding penetration in Flux Cored Arc Welding using the backhand method, as noted by Mostafa and Khajavi (2006) However, there is a lack of supporting evidence in other literature to validate this finding across different welding techniques.

Murugan and Gunaraj (2005) demonstrated that increasing the wire feed rate reduces angular distortion until a minimum threshold is achieved Additionally, it is essential to adjust the welding speed in tandem with the wire feed rate, as a higher welding speed is recognized to further decrease distortion.

Figure 2.6 – Direct effect on bending distortion of the 4 manufacturing parameters analysed in

Murugan and Gunaraj (2005) investigated the relationship between the number of runs and the time intervals between them, finding that longer intervals lead to increased heat loss from the plate This implies that extended time between welding passes allows some of the heat from the previous pass to preheat the plate, resulting in a reduced net heat input Consequently, this reduction in heat input minimizes angular distortion during the welding process.

As the number of runs increases, both the net heat input to the plate and weld distortion rise However, with a greater number of runs, the deposited weld metal begins to restrain the newly added pass, resulting in a decrease in angular distortion per pass as the weld accumulates.

In a series of three interaction studies conducted by Murugan and Gunaraj in 2005, it was found that the time between runs has a more significant impact on angular distortion than the number of runs Additionally, the number of passes plays a more crucial role in influencing angular distortion compared to the wire feed rate Notably, increasing the time between passes effectively reduces angular distortion, particularly when the wire feed rate is low; however, this reduction effect diminishes at higher wire feed rates.

Colegrove et al (2009) conducted a comparative study on the heat input and weld distortions associated with six welding processes, including SAW, DC and Pulsed GMAW, CMT, Autogenous Laser, and Hybrid Laser, while welding butt-joint A131 DH36 steel grade plates The findings revealed that the SAW and DC GMAW methods resulted in the highest heat input and weld distortion, whereas the Hybrid Laser method exhibited the lowest levels of both Additionally, the study concluded that the Pulsed GMAW and Hybrid Laser methods yield the highest quality welds with minimal distortion Furthermore, a linear relationship was identified between the Fusion Zone area and heat input.

Clamping is a widely used technique in welding, essential for preventing significant distortions and securely holding plates during the welding process This study examines the effects of clamping methods, the number of clamps employed, the timing of their release, and the impact of pre-heating the clamps on the overall welding outcome.

Research by Cronje (2005), Kastelic et al (2010), Mousavi and Miresmaeili (2008), and Fu et al (2014) indicates that unrestrained weldings lead to higher distortions but lower residual stresses Figure 2.7 illustrates that increasing the degree of clamping reduces weld distortions while simultaneously increasing residual stresses Cheng et al (2005) and Schenk et al (2009) noted that significant clamping restraints impede shrinkage, resulting in plastic strains in the weld zone that help relieve residual stresses Additionally, Schenk et al (2009) and Biswas et al (2011) observed variations in weld distortion types based on the number of clamps used However, all these studies, including findings by Mahapatra et al (2006), agree that restraining a weldment consistently minimizes distortions Figure 2.8 presents images depicting the expansion and shrinkage of a restrained welded plate alongside the development of plastic strains in the weld bead area.

Figure 2.7 – Version of the graphic representing the degree of clamping effect on residual stresses and on distortion made by (Cronje 2005)

“The degree of restraint is a function of the type of joint, the rigidity of the structure, the amount of gap between the abutting edges and the plates’ thickness.”

MANUFACTURING METHODOLOGIES DEVELOPED TO AVOID WELD

Conventional Methodologies

Effective weld distortion control techniques must be suitable for the specific type of distortion present in the welded structure Over the years, numerous distortion-control methods have been developed and refined, with significant advancements made as recently as 2002 by Northrop.

Grumman Ship Systems initiated a program focused on investigating and developing distortion-control techniques for lightweight structures, particularly thin plates This sub-chapter outlines several conventional methodologies, and a set of four tables by Conrardy et al (2006) detailing various distortion-control techniques, along with their advantages and disadvantages, can be found in Appendix A of this work.

Overwelding involves excessive weld metal in a joint, leading to increased shrinkage stresses To prevent overwelding, proper joint preparation is essential, and avoiding highly convex beads is recommended For thicker plates, reducing the preparation angle and increasing the root opening can help mitigate this issue Additionally, utilizing "X" or "U" weld groove shapes is a viable alternative Examples of overwelded plates illustrate these concepts, highlighting the importance of adhering to theoretical throat dimensions and employing effective joint preparations to avoid overwelding (Feng 2005, Conrardy et al 2006, Lee and Beardsley 2009, “The Lincoln Electric” 2015).

Intermittent welding, illustrated in Figure 3.2, is an effective technique that minimizes both the volume of weld metal and the occurrence of weld distortions, making it a preferred choice for certain applications However, it is important to note that this method is not suitable for all types of welds and is frequently utilized for attaching stiffeners to plates (Conrardy et al.).

2006, Lee and Beardsley 2009, “The Lincoln Electric” 2015)

Figure 3.1 – a) Overwelded plates; b) Common joint preparation and weld groove shapes known to avoid overwelding (“The Lincoln Electric” 2015)

Figure 3.2 – Example of intermittent weldings in a T-fillet joint (“The Lincoln Electric” 2015)

MANUFACTURING METHODOLOGIES DEVELOPED TO AVOID WELD DISTORTION

3.1.3 Reduce the number of passes

Minimizing the number of welding passes and opting for larger electrodes or wires can significantly reduce shrinkage stresses and angular distortion compared to using smaller electrodes or wires with multiple passes (Conrardy et al 2006, Lee and Beardsley 2009, “The Lincoln Electric” 2015).

3.1.4 Welding near the neutral axis

This welding technique focuses on positioning the weld metal's centroid near the neutral axis of the cross-section, effectively minimizing the lever-arm of the bending moment As a result, this alignment significantly reduces both bending and angular distortions Figure 3.3 illustrates this concept, with the upper images depicting welds positioned away from the neutral axis, while the lower images show welds that are aligned with it (Feng 2005, Conrardy et al 2006, Lee and Beardsley 2009, “The Lincoln Electric” 2015).

3.1.5 Balancing the welds around the neutral axis

When welding symmetrical structures, it is essential to balance the welds around the neutral axis to minimize distortions This technique involves applying welds symmetrically, which allows the shrinkage stresses from one weld to counteract those from another across the neutral axis As a result, the overall weld distortions are significantly reduced, as supported by various studies (Feng 2005, Conrardy et al 2006, Lee and Beardsley 2009, “The Lincoln Electric” 2015).

3.3 shows two similar structures welded in different ways The top image does not have the welds balanced around the neutral axis, while the bottom image has the welds balanced around the neutral axis

Figure 3.3 – a) Example of weldings near the neutral axis in the bottom image; b) Example of balance of the welds around the neutral axis in the bottom image (“The Lincoln Electric” 2015)

Figure 3.4 illustrates backstep welding applied to a butt joint plate, a technique that segments the weld bead and alters the welding direction for each segment For instance, when welding from left to right, individual bead segments are deposited from right to left However, this method may not be suitable for all applications, particularly in automatic welding, where it may lack economic viability (Conrardy et al 2006, Lee and Beardsley 2009, “The Lincoln Electric” 2015).

Welding preset parts effectively utilizes shrinkage stresses to align plates, resulting in reduced weld distortion This technique is applicable when the magnitude and shape of weld distortion are known or predictable Adjustments to preset parts can include pre-bending, altering joint preparation, or modifying clamping positions For instance, parts can be designed with changed joint preparations to counteract shrinkage stresses post-weld, or a convex pre-bent plate can be employed to mitigate concave bending distortion.

(Feng 2005, Conrardy et al 2006, Lee and Beardsley 2009, “The Lincoln Electric” 2015)

Figure 3.4 – Example of a backstep welding The welding direction is from point A to point B Each weld bead segment is welded in the direction from B to A (“The Lincoln Electric” 2015)

Effective planning of the weld sequence is essential to minimize weld distortion By strategically placing the weld metal at alternating points within an assembly, shrinkage stresses can counterbalance each other For instance, in one example, the top and bottom surfaces of an "X" weld groove shape in a butt-joint plate are welded alternately, while in another, the left and right sides of a T-fillet joint are welded alternately These methods significantly reduce weld distortions.

To minimize distortions and ensure effective heat dissipation, it is crucial to complete welding quickly Prolonged welding times result in the expansion of a greater volume of metal, leading to increased distortions Utilizing automatic equipment can significantly reduce welding time, enhancing overall efficiency.

Figure 3.5 – Presetting parts a) Parts with joint preparation changed, before and after welding; b) Pre-bent plate after welding The removal of the clamps will align the plate (“The Lincoln

To reduce weld distortion caused by shrinkage stresses during cooling, techniques such as peening are employed Peening involves manipulating the surface of the metal through methods like hammer blows or shot blasts, effectively stretching and thinning the weld bead This process induces plastic strains that alleviate the tensile stresses formed in the weld bead as it cools, while also increasing its hardness However, it's important to note that this method is often not recognized by many welding standards, specifications, or codes.

“Peening” 2005, Lee and Beardsley 2009, “The Lincoln Electric” 2015)

Thermal stress relieving is an effective method for eliminating shrinkage stresses in weldments This technique involves carefully heating the weldments to a high temperature and then controlling the cooling process According to FENG (2005), both heating and cooling are crucial for achieving optimal results.

Figure 3.6 – Examples of weld sequences that minimize weld distortion a) Butt-joint weld sequence; b) Two T-fillet joint weld sequences (“The Lincoln Electric” 2015)

T RAILING HEAT S INK

The trailing heat sink technique consists in welding with a cooling nozzle attached behind the welding torch, or behind the welding tool in the case of Friction Stir

Welding involves the use of a cooling nozzle that dispenses a liquid to cool the weld bead effectively As illustrated in Figure 3.7, the trailing heat sink setup is integral to the welding process The primary goal of this technique is to minimize residual stresses, thereby preventing buckling distortion in the welded structure.

(Gabzdyl et al 2003, Feng 2005, Soul and Zhang 2006, Han et al 2011, Okano et al 2012,

Soul and Hamdy 2012) Some of the liquids available to use in the cooling nozzle include liquid nitrogen (Kala et al 2014) and liquid CO2 (Richards et al 2010)

Figure 3.8 presents eight studies examining the impact of trailing heat sinks on weld distortion and residual stresses in titanium alloys, aluminum alloys, and various steel grades, utilizing a range of welding methods.

Figure 3.8 - Articles that analysed the effect of trailing heat sink, organized by type of weld performed

Figure 3.7 – Schematic drawing of a trailing heat sink setup during the welding process

Research indicates that using a trailing heat sink significantly reduces weld distortions Key adjustable parameters in this technique include the cooling nozzle distance from the weld bead and the cooling intensity Studies by Richards et al (2010) and Kala et al (2014) demonstrate that decreasing the cooling nozzle distance lowers both residual stresses and weld distortions, while a greater distance reduces residual stresses but increases distortions Additionally, Guo et al (2014) found that increasing cooling intensity leads to a decrease in both residual compressive stresses and weld distortions, with compressive stresses primarily forming in the weld bead area.

Thermal Tensioning

The thermal tensioning technique, utilized in welding, can be categorized into static and transient methods Static thermal tensioning involves prestretching the weld bead area through a thermal gradient by heating either side of the weld while quenching it simultaneously In contrast, transient thermal tensioning employs heating bands that move with the welding torch, as illustrated in Figure 3.9 This method does not require quenching and effectively heats a broader area of the plate, creating additional tensile zones The primary goal of thermal tensioning is to mitigate compressive residual stresses, thereby preventing buckling distortion in thin plates.

In 2001, it was determined that thermal tensioning can create structures with almost zero residual stresses, effectively eliminating buckling distortion Additionally, Michaleris et al (1999) noted that the shrinkage values associated with thermal tensioning are minimal Shaoqing et al also contributed to this understanding.

Research from 2001 demonstrated that transient thermal tensioning significantly minimizes bending distortion in butt-joint plates Similarly, findings by Deo and Michaleris in 2003 confirmed that this technique is also effective in reducing distortion in stiffeners during the welding of T-fillet joints.

Figure 3.9 – Drawing of a Transient Thermal Tensioning setup during the welding process (Conrardy et al 2006)

METHODS TO QUANTIFY THE WELD DISTORTION

Profile Tracer

The profile tracer method involves tracing the plate's profile onto a sheet of paper, allowing for the measurement of weld distortions through the lines drawn This technique effectively measures both angular and bending distortions and is regarded as simple and reliable (Venkatesan et al 2013; 2014) A schematic diagram illustrating the profile tracer measuring bending distortion is presented in Figure 4.1.

Figure 4.1 – Schematic diagram of a profile tracer to measure Bending distortion

Dial Indicator

A dial indicator is a precision instrument designed for measuring small distances or angles, featuring a probe and a dial display Specifically, a dial test indicator includes a probe that swings rather than retracts, allowing for accurate measurements of angular distortions An example of this is shown in Figure 4.2, which depicts a dial test indicator commercialized by Starrett©.

Vernier Instruments

A bevel protractor features a circular protractor with a dial, main scale, and beam, with a graduated circular protractor connected to a blade The Vernier Bevel Protractor, which includes a Vernier scale for enhanced accuracy, is depicted in Figure 4.3 This tool is commonly utilized to measure angular distortions, recognized for its simplicity and reliability (Parmar 2003, Venkatesan and Murugan 2014, "Vernier Bevel Protractor" 2015).

Figure 4.2 - Starrett © B708AZ Dial Test Indicator

A height gauge is an essential tool for measuring the height of objects, with the Vernier height gauge offering enhanced precision through its Vernier scale This device is particularly effective in assessing bending distortions, as highlighted in various studies (Parmar 2003, "Height Gauge" 2004, Murugan and Gunaraj 2005, Price et al 2007) An example of a Vernier height gauge can be seen in Figure 4.3, showcasing a model commercialized by Mitutoyo©.

Linear Variable Differential Transformer

The Linear Variable Differential Transformer (LVDT) is a precise device that measures linear displacements by detecting variations in internal induced voltage, with sensitivities ranging from 0.003 to 0.25V/mm It effectively measures displacement ranges between 0.125mm and 0.64mm, making it suitable for assessing weld distortion during welding and cooling processes Numerous studies, including those by Tsirkas et al (2003), Camilleri et al (2005), Colegrove et al (2009), Zain-ul-abdein et al (2010), and Narang et al (2014), have utilized LVDTs to quantify weld distortion.

Figure 4.3 – Left: Vernier Bevel Protractor and its constituent parts ("Vernier Bevel Protractor" 2015);

Right: Vernier Heigh gauge S514 commercialized by Matutoyo ©

Coordinate Measuring Machines

Coordinate Measuring Machines (CMMs) are essential tools for measuring the geometric characteristics of objects, providing precise coordinates for any given point These machines feature a structure with a probe that operates in at least three dimensions Depending on the probe type, CMMs can be classified as either contact scanning, using mechanical probes, or contactless scanning, utilizing optical, laser, or white light probes Typically controlled via CNC, CMMs can be either fixed or portable, making them versatile for various applications They are particularly useful for measuring weld distortion and creating 3D models of plates when using contactless scanning systems An example of a commercial CMM is shown in Figure 4.4, featuring a model by Nikon©.

Figure 4.4 – Nikon Altera ©, a coordinate measuring machine with a optical probe

Digital Image Correlation

Digital Image Correlation (DIC) is an optical, contactless, full-field analysis method that utilizes grey value digital images to determine the surfaces and contours of objects By employing two cameras, image registration techniques, and a correlation algorithm, DIC enables the comparison of surface profiles before and after welding, effectively measuring 3D deformation Proper camera calibration is essential for accurate results, allowing DIC to assess both transient and post-weld distortions Notably, ARAMIS®, developed by GOM©, is a prominent software used in conjunction with DIC hardware Research studies, such as those by Zain-ul-abdein et al (2010) and Perić et al (2014), have successfully applied DIC to measure weld distortion, illustrating its effectiveness in this field.

Figure 4.5 - Schematic image of a DIC setup with the working principle ("Measurement

Laser Scanning

Laser scanning utilizes Laser Displacement Sensors to accurately measure weld distortion, employing either static or moving sensors that emit laser beams These beams reflect off the object and are collected by the sensors, with the data transmitted to a computer to determine displacement values This technique effectively measures angular, bending, and buckling distortions during the welding process ("Laser Scanning" 2006) A schematic diagram illustrating a laser scanning setup for measuring weld distortion is presented in Figure 4.6 Notably, Conrardy et al (2006) applied LIDAR technology for distortion measurement, while other studies by Camilleri et al (2005), Mikami et al (2009), Matsuoka et al (2013), Guo et al (2014), and Islam et al (2014) also utilized laser sensors for this purpose.

Figure 4.6 – Schematic diagram of a laser scanning setup to measure weld distortion (Matsuoka et al 2013)

Photogrammetry

Photogrammetry is a remote sensing technique that utilizes photographs to accurately determine the position of points or surfaces through multiple point triangulation The most common application for measuring weld distortion is close range photogrammetry, where the camera is positioned near the object This method shares a similar setup with Digital Image Correlation but employs photographic cameras instead Photogrammetry is effective for creating 3D models of photographed objects (Walford, 2007) Notable experiments by Conrardy et al (2006) and Lightfoot et al (2007) demonstrated the use of photogrammetry in measuring weld distortion.

ECONOMIC IMPACT OF WELD DISTORTION IN WELDED CONSTRUCTION

Weld distortion in structures leads to two significant issues: it causes dimensional inaccuracies that complicate the alignment of sub-assemblies and increases manufacturing costs due to the need for time-consuming rectifying and straightening processes, as highlighted by various studies (Camilleri et al 2005; Deng et al 2007; Bachorski et al 1999; Ghosh et al 2010; Seyyedian Choobi et al 2012; Wang et al 2010).

Industries such as automobile, aerospace, and shipbuilding face significant rectification costs associated with thin plate structures, with weld distortions accounting for up to 30% of total fabrication expenses (Deng et al 2012; Tian et al 2014; Holder et al 2011; Shen 2013) Despite the high costs, correcting these distortions is more economical than replacing the affected components (Camilleri et al 2005; Soul and Hamdy 2012).

“Severe distortions have emerged as a major obstacle to the cost- effective fabrication of such lightweight structures”

Industrial control of weld distortions typically relies on empirical formulas derived from historical data; however, these formulas are often inadequate for large, complex structures (Bachorski et al 1999) An effective alternative is the application of numerical methods through finite element analysis (FEM), despite their high hardware demands and time-consuming nature (Deng and Murakawa 2008) Notably, correcting weld distortions is generally more costly than implementing preventive measures FEM simulations not only enable accurate predictions of weld distortion but also enhance the understanding of the underlying phenomena, leading to the development of effective mitigation strategies (Seyyedian Choobi et al.).

2012) Some of the techniques applied to correct the weld distortions are the Flame

Various methods for straightening materials include Cold Bending, Press Straightening, and Laser Shock Processing (Feng 2005; Gannon et al 2010) Additionally, thermal techniques such as Spot Heating, Line Heating, and Wedge Shaped Heating are effective for correcting distortions (Lucas et al.) However, the flame straightening method is noted to be time-consuming and costly, requiring skilled labor for execution (Feng 2005) Furthermore, straightening machines represent a significant investment, particularly for large structures (Feng 2005).

CONCLUSIONS

In this thesis, an analysis of the existing types of weld distortions and the weld distortions mechanisms is performed, based on an extensive literature survey

The following aspects were covered:

 The distortion mechanisms and their relation to the heat sources used in welding

 The methods used to quantify weldings distortion

 The developed manufacturing methodologies to avoid weld distortion

 The weld distortion impact in the economy of welded construction industries

From the literature review, it was concluded that:

 There is a clear relation between the analysed geometrical parameters such as the plate width and the plate length, and weld distortion

 The “V” and “X” shaped weld grooves effect on weld distortion are well established, however there is a lack of information regarding the other weld groove shapes and joint types

 There is a clear relation between the phase transition of both base and weld metal and the weld distortion

 There is a clear relationship between the variable welding parameters, such as the current intensity, the electric voltage and the weldings speed, and weld distortion

 The effect of the use of constraints on weld distortion is well defined

 There is no consensus in the published literature regarding the plate thickness effect on weld distortion

 Although there is extensive literature regarding the base metal properties effect in FEM simulations, there is few articles regarding its direct effect on weld distortion

 There is few literature regarding the heat source effect on weld distortion, namely, the welding methods used

This article outlines various methodologies for preventing weld distortion and quantifying its effects It evaluates the effectiveness and applicability of these techniques, providing a comprehensive discussion Additionally, a table is included that details different distortion-control methods, highlighting their advantages and disadvantages.

Various methods used to quantify the weld distortion were presented and described It was mentioned the type of distortion that each method can efficiently measure

A study has been conducted to assess the economic impact of weld distortion, highlighting the limited existing literature on this topic There are few articles that quantify the financial effects of weld distortion, and information on methods for correcting weld distortion remains scarce.

Adak, M., Guedes Soares, C., 2014 Effects of different restraints on the weld-induced residual deformations and stresses in a steel plate International Journal of Advanced

Akbari Mousavi, S A A., Miresmaeili, R., 2008 Experimental and numerical analyses of residual stress distributions in TIG welding process for 304L stainless steel Journal of Materials Processing Technology, 208(1-3), pp.383–394 DOI: 10.1016/j.jmatprotec.2008.01.015

Bachorski, A., Painter, M.J., Smailes, A.J., Wahab, M.A., 1999 Finite-element prediction of distortion during gas metal arc welding using the shrinkage volume approach

Journal of Materials Processing Technology, 92-93, pp.405–409 DOI:

Banarjee, R., 2005 The Role of Gases in Welding and Cutting Processes Indian Welding

Bhadeshia, H.K.D.H., 2004 Developments in martensitic and bainitic steels: Role of the shape deformation Materials Science and Engineering A, 378(1-2 SPEC ISS.), pp.34–39 DOI: 10.1016/j.msea.2003.10.328

Bhargava, P., Paul, C.P., Mundra, G., Premsingh, C.H., Mishra, S.K., Nagpure, D., Kumar, A., Kukreja, L.M., 2014 Study on weld bead surface profile and angular distortion in

6 mm thick butt weld joints of SS304 using fiber laser Optics and Lasers in Engineering, 53, pp.152–157 DOI: 10.1016/j.optlaseng.2013.08.022

Bhatti, A.A., Barsoum, Z., Murakawa, H., Barsoum, I., 2015 Influence of thermo- mechanical material properties of different steel grades on welding residual stresses and angular distortion Materials & Design, 65, pp.878–889 DOI: 10.1016/j.matdes.2014.10.019

Bhide, S.R., Michaleris, P., Posada, M., DeLoach, J., 2006 Comparison of buckling distortion propensity for SAW, GMAW, and FSW Welding Journal, 85(September), p.189s–195s

Biswas, P., Mandal, N.R., Vasu, P., Padasalag, S.B 2011 A study on port plug distortion caused by narrow gap combined GTAW & SMAW and Electron Beam Welding

Fusion Engineering and Design, 86(1), pp.99–105 DOI: 10.1016/j.fusengdes.2010.08.040

Camilleri, D., Comlekci, T., Gray, T.G.F., 2005 Computational prediction of out-of-plane welding distortion and experimental investigation - Awarded Central Electricity Generating Board Prize , 40(2), pp.161–176 DOI: 10.1243/030932405X7809

Camilleri, D., McPherson, N., Gray, T.G.F., 2013 The applicability of using low transformation temperature welding wire to minimize unwanted residual stresses and distortions International Journal of Pressure Vessels and Piping, 110, pp.2–8 DOI:

Chao, Y.J., 2005 Measuring weld-induced distortion In Z Feng, ed Processes and mechanisms of welding residual stress and distortion Woodhead Publishing and

Cheng, C.M., Chou, C.P., Lee, I.K., Lin, H.Y., 2005 Distortion Analysis of Single V- groove Butt Welding on Heat Treatable Aluminum Alloys , 21(5), pp.738–742 Available at: http://front.cc.nctu.edu.tw/Richfiles/15544-2005069.pdf

Colegrove, P.A., Ikeagu, C., Thistlethwait, A., Williams, S., Nagy, T., Suder, W., Steuwer, A., Pirling, T., 2009 Welding process impact on residual stress and distortion , 14(8), pp.717–726 DOI: 10.1179/136217109X406938

Conrardy, C., Huang, T.D., Harwig, D., Dong, P., Kvidahl, L., Evans, N., Treaster, A.,

2006 Practical Welding Techniques to Minimize Distortion in Lightweight Ship Structures Journal of Ship Production, 22(4), pp.239–247

"Coordinate-measuring machine"., 2005 Wikipedia Available at: https://en.wikipedia.org/wiki/Coordinate-measuring_machine#Specific_parts

Cronje, M., 2005 Finite Element Modelling of Shielded Metal Arc Welding Master of Science in Mechanical Engineering thesis Stellenbosch University

Deng, D., 2009 FEM prediction of welding residual stress and distortion in carbon steel considering phase transformation effects Materials and Design, 30, pp.359–366

Deng, D., 2013 Influence of deposition sequence on welding residual stress and deformation in an austenitic stainless steel J-groove welded joint Materials and Design, 49, pp.1022–1033 DOI: 10.1016/j.matdes.2013.02.065

Deng, D., Murakawa, H., 2008 FEM prediction of buckling distortion induced by welding in thin plate panel structures Computational Materials Science, 43, pp.591–607 DOI: 10.1016/j.commatsci.2008.01.003

Deng, D., Murakawa, H., Liang, W., 2007 Numerical simulation of welding distortion in large structures Computer Methods in Applied Mechanics and Engineering, 196, pp.4613–4627 DOI: 10.1016/j.cma.2007.05.023

Deng, D., Zhou, Y., Bi, T Liu, X., 2013 Experimental and numerical investigations of welding distortion induced by CO2 gas arc welding in thin-plate bead-on joints

Materials and Design, 52, pp.720–729 DOI: 10.1016/j.matdes.2013.06.013

Deo, M.V., Michaleris, P., 2003 Elimination of Bowing Distortion in Welded Stiffeners , 19(2), pp.76–83

Deo, M.V., Michaleris, P., Sun, J., 2003 Prediction of buckling distortion of welded structures Science and Technology of Welding and Joining, 8, pp.55–61 DOI:

"Digital Image Correlation"., 2007 Wikipedia Available at: https://en.wikipedia.org/wiki/Digital_image_correlation [Accessed July 2, 2015]

Dye, D., Hunziker, O., Roberts, S.M., Reed, R.C., 2001 Modeling of the mechanical effects induced by the tungsten inert-gas welding of the IN718 superalloy

Metallurgical and Materials Transactions A, 32(7), pp.1713–1725 DOI:

Feng, Z., 2005 Processes and mechanisms of welding residual stress and distortion

Woodhead Publishing and Maney Publishing

Fu, G., Lourenco, M.I., Duan, M., Estefan, S.F., 2014 Effect of boundary conditions on residual stress and distortion in T-joint welds 3D Finite Element Model a b JCSR,

Gabzdyl, J., Johnson, A., Williams, S., Price, D., 2003 Laser weld distortion control by cryogenic cooling First International Symposium on High-Power Laser Macroprocessing, pp.269–274 DOI: 10.1117/12.486497

In their 2014 study published in Procedia Engineering, Ganesh et al focused on modeling, predicting, and validating thermal cycles, residual stresses, and distortion in Type 316 LN stainless steel weld joints created through the TIG welding process The research provides valuable insights into the factors affecting weld quality and performance, contributing to improved welding techniques and material integrity.

Gannon, L., Liu, Y., Pegg, N., Smith, M., 2010 Effect of welding sequence on residual stress and distortion in flat-bar stiffened plates Marine Structures, 23(3), pp.385–404 DOI: 10.1016/j.marstruc.2010.05.002

Ghosh, B.P.K., Devakumaran, K., Pramanick, A.K., 2010 Effect of Pulse Current on Shrinkage Stress and Distortion in Multipass GMA Welds of Different Groove Sizes

Guo, Y., Wu, D., Ma, G., Guo, D., 2014 Trailing heat sink effects on residual stress and distortion of pulsed laser welded Hastelloy C-276 thin sheets Journal of Materials Processing Technology, 214(12), pp.2891–2899 DOI: 10.1016/j.jmatprotec.2014.06.012

The study by Han et al (2011) investigates the influence of trailing heat sinks on residual stresses and welding distortion in friction stir welding of aluminum sheets The findings, published in the journal Science and Technology of Welding & Joining, demonstrate that the implementation of trailing heat sinks can effectively mitigate residual stresses and reduce welding distortion, thereby enhancing the quality of the welded joints This research provides valuable insights for improving the friction stir welding process in aluminum applications.

"Height Gauge"., 2004 Wikipedia Available at: https://en.wikipedia.org/wiki/Height_gauge [Accessed July 1, 2015]

Heinze, C., Schwenk, C., Rethmeier, M., 2012 Effect of heat source configuration on the result quality of numerical calculation of welding-induced distortion Simulation Modelling Practice and Theory, 20(1), pp.112–123 DOI: 10.1016/j.simpat.2011.09.004

Holder, R., Larkin, N., Kuzmikova, L., Huijun, L., Pan, Z., Norrish, J., 2011 Development of a DC-LSND welding process for GMAW on DH-36 Steel 56th WTIA Annual Conference, 2011, pp.1–13

Howes, M., Inoue, T., Park, M., 2002 Handbook of Residual Stress and Deformation of Steel Edited by,

Huang, H.Y., 2010 Argon-hydrogen shielding gas mixtures for activating flux-assisted gas tungsten arc welding Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, 41(11), pp.2829–2835 DOI: 10.1007/s11661-010-

Huang, T.D., Dong, P., DeCan, L.A., Harwig, D.D., 2003 Residual stresses and distortions in lightweight ship panel structures Technology Review Journal, 11(1), pp.1–26

"Indicator"., 2005 Wikipedia Available at: https://en.wikipedia.org/wiki/Indicator_(distance_amplifying_instrument) [Accessed July 1, 2015]

Islam, M., Bujik, A., Rais-Rohani, M., Motoyama, K., 2014 Simulation-based numerical optimization of arc welding process for reduced distortion in welded structures Finite

Elements in Analysis and Design, 84, pp.54–64 DOI: 10.1016/j.finel.2014.02.003

Kala, S.R., Siva Prasad, N., Phanikumar, G., 2014 Studies on multipass welding with trailing heat sink considering phase transformation Journal of Materials Processing Technology, 214(6), pp.1228–1235 DOI: 10.1016/j.jmatprotec.2014.01.008

Kastelic, S., Medved, J., Mrvar, P., 2010 Prediction of Numerical Distortion after Welding with Various Welding Sequences and Clampings , 49(4), pp.301–305

Kurihara, N., Tomida, S., Takeshita, K., 2004 Effect of Shielding Gas on Welding Distortion of Laser Welded Aluminum Alloy Sheet Memoirs of the Faculty of Engineering, 52(2), pp.217–222

Lancaster, J.F., 1984 The physics of welding Physics in Technology, 15(2), pp.73–79

"Laser Scanning"., 2006 Wikipedia Available at: https://en.wikipedia.org/wiki/Laser_scanning [Accessed July 2, 2015]

Lightfoot, M.P., Bruce, G.J., Barber., D.M., 2007 The Measurement of Welding Distortion in Ship Building Using Close Range Photogrammetry In Annual Conference of the Remote Sensing and Photogrammetry Society UK: Newcastle

"Linear Buckling"., 2011 Carat ++ wiki Available at: http://carat.st.bv.tum.de/caratuserswiki/index.php/Users:Structural_Optimization/Res ponse_Functions/Linear_Buckling [Accessed June 24, 2015]

"Linear Variable Differential Transformer"., 2004 Wikipedia Available at: https://en.wikipedia.org/wiki/Linear_variable_differential_transformer [Accessed July

The study by Liu et al (2011) investigates the impact of the heat-affected zone on the mechanical properties of copper bonding wire Presented at the 2011 IEEE 61st Electronic Components and Technology Conference (ECTC), the research highlights how thermal effects during bonding processes can alter the performance characteristics of copper wires, which are critical for electronic applications The findings underscore the importance of understanding these effects to enhance the reliability and efficiency of electronic components.

Lucas, B., Leggatt, R & Mathers, G., Distortion - Corrective Techniques The Welding Institute Available at: http://www.twi-global.com/technical-knowledge/job- knowledge/distortion-corrective-techniques-037/ [Accessed July 1, 2015]

Mahapatra et al (2006) conducted a three-dimensional finite element analysis to investigate how various submerged arc welding (SAW) process parameters influence temperature distribution and angular distortions in single-pass butt joints with reinforcements on both the top and bottom Their findings were published in the International Journal of Pressure Vessels and Piping, highlighting the significance of understanding these effects for improving welding techniques and outcomes The study can be accessed through DOI: 10.1016/j.ijpvp.2006.07.011.

Masubushi, K., 1980 Analysis of Welded Structures First Edit., Pergamon Press

Matsuoka, S., Okamoto, Y., Okada, A., 2013 Influence of weld bead geometry on thermal deformation in laser micro-welding Procedia CIRP, 6, pp.492–497 Available at: http://dx.doi.org/10.1016/j.procir.2013.03.054 DOI: 10.1016/j.procir.2013.03.054

McGlone, J.C., 1978 The submerged arc butt welding of mild steel Part1 The influence of procedure parameters on weld bead geometry,

"Measurement Principles of DIC"., 2013 Dantec Dynamics Available at: http://www.dantecdynamics.com/measurement-principles-of-dic [Accessed July 2,

Michaleris, P., Debiccari, A, 1997 Prediction of welding distortion Welding Journal Miami Fla, 76, p.172–s DOI: 10.1016/j.jmatprotec.2007.10.009

Michaleris, P., Dantzig, J., Tortorelli, D., 1999 Minimization of welding residual stress and distortion in large structures Welding Journal Research Supplement,

Mikami, Y., Morikage, Y., Mochizuki, M., Toyoda, M., 2009 Angular distortion of fillet welded T joint using low transformation temperature welding wire Science and Technology of Welding and Joining, 14(2), pp.97–105 DOI: 10.1179/136217108X382972

Mostafa, N.B., Khajavi, M.N., 2006 Optimisation of welding parameters for weld penetration in FCAW Journal of Achievements in Materials and Manufactruring Engineering, 16(1), pp.13–17

Murugan, V.V., Gunaraj, V., 2005 Effects of Process Parameters on Angular Distortion of Gas Metal Arc Welded Structural Steel Plates Welding Journal, Research Supplement, (November), p.165s–171s

Narang, H.K., Mahapatra, M.M., Jha, P.K., Biswas, P., 2014 Optimization and Prediction of Angular Distortion and Weldment Characteristics of TIG Square Butt Joints

Journal of Materials Engineering and Performance, 23(May), pp.1750–1758 DOI:

Narayanan, R., Kalyanaraman, V., Santhakumar, A.R., Seetharaman, S., Kumar, S.R.S., Jayachandran, S.A., Senthil, R., 1999 Introduction to Plate Buckling Institute for Steel Development and Growth, pp.7–3 Available at: http://www.steel- insdag.org/TeachingMaterial/Chapter7.pdf [Accessed July 3, 2015]

Negahban, M., 2000 Thermal Strains Available at: http://emweb.unl.edu/NEGAHBAN/Em325/05-Thermal-strain/Thermal strain.htm [Accessed June 15, 2015]

Okano, S., Mochizuki, M, Toyoda, M, Ueyama, T, 2012 Effect of welding conditions on reduction in angular distortion by welding with trailing heat sink Science and Technology of Welding & Joining, 17(4), pp.264–268 DOI: 10.1179/1362171811Y.0000000103

Pal, S., Malviya, S.K., Pal, S.K., Samantaray, A.K., 2009 Optimization of quality characteristics parameters in a pulsed metal inert gas welding process using grey- based Taguchi method International Journal of Advanced Manufacturing Technology, 44(11-12), pp.1250–1260 DOI: 10.1007/s00170-009-1931-0

Pal, K., Bhattacharya, S., Pal, S.K., 2010 Multisensor-based monitoring of weld deposition and plate distortion for various torch angles in pulsed MIG welding

International Journal of Advanced Manufacturing Technology, 50(5-8), pp.543–556

Parmar, R.S., 2003 Welding Processes and Technology, New Delhi: Khanna Publishers

"Peening"., 2005 Wikipedia Available at: https://en.wikipedia.org/wiki/Peening [Accessed July 1, 2015]

Perić, M., Tonković, Z., Rodić, A., Surjak, M., Garašić, I., Boras, I., Švaić, S., 2014 Numerical analysis and experimental investigation of welding residual stresses and distortions in a T-joint fillet weld Materials and Design, 53, pp.1052–1063 DOI:

Pilipcncko, A., 2001 Computer simulation of residual stress and distortion of thick plates in multi-electrode submerged are welding - Their mitigation techniques Master of

Science in Mechanical Engineering thesis Norwegian University of Science and Technology

Price, D.A., Williams, S.W., Wescott, A., Harrison, C.J.C., Rezai, A., Steuwer, A., Peel, M., Staron, P., Koỗak, M., 2007 Distortion control in welding by mechanical tensioning Science and Technology of Welding and Joining, 12(7), pp.620–633 DOI: 10.1179/174329307X213864

Rausch, J., 2015 Gas Metal Arc Welding Basics: Travel Speed and Contact to Work Distance EWI Available at: http://ewi.org/gas-metal-arc-welding-basics-travel- speed-and-contact-to-work-distance-ctwd/ [Accessed June 1, 2015]

Richards, D.G, Prangnell, P.B., Withers, P.J., Williams, S.W., Nagy, T., Morgan, S., 2010 Efficacy of active cooling for controlling residual stresses in friction stir welds

Science and Technology of Welding and Joining, 15(2), pp.156–165 DOI:

Sattari-Far, I., Farahani, M.R., 2009 Effect of the weld groove shape and pass number on residual stresses in butt-welded pipes International Journal of Pressure Vessels and

Schenk, T., Richardson, I.M., Kraska, M., Ohnimus, S., 2009 A study on the influence of clamping on welding distortion Computational Materials Science, 45(4), pp.999–

Seyyedian Choobi, M., Haghpanahi, M., Sedighi, M., 2012 Prediction of welding-induced angular distortions in thin butt-welded plates using artificial neural networks

Computational Materials Science, 62, pp.152–159 DOI: 10.1016/j.commatsci.2012.05.032

Shaoqing, G., Xiaohong, L., Wenli, X., Xuesong, L., Xin, W., Xitang, T., 2001 Welding Distortion Control of Thin Al Alloy Plate by Static Thermal Tensioning Journal of Materials Science & Technology, 17(1), pp.163–164

Shen, C., 2013 Low distortion welding for shipbuilding industry Master of Engineering thesis School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong

Soul, F., Hamdy, N., 2012 Numerical Simulation of Residual Stress and Strain Behavior After Temperature Modification

Soul, F.A., Zhang, Y.H., 2006 Numerical study on stress induced cambering distortion and its mitigation in welded titanium alloy sheet Science and Technology of Welding and Joining, 11(6), pp.688–693 10.1179/174329306X147715

Teng, T., Fung, C., Chang, P., Yang W., 2001 Analysis of residual stresses and distortions in T-joint fillet welds International Journal of Pressure Vessels and Piping, 78, pp.523–538

"The Lincoln Electric" Weld distortion The Lincoln Electric Company Available at: http://www.lincolnelectric.com/en-us/support/welding-how-to/pages/weld-distortion- detail.aspx [Accessed July 1, 2015]

"Thermal Stresses" The Engineering ToolBox Available at: http://www.engineeringtoolbox.com/stress-restricting-thermal-expansion- d_1756.html [Accessed June 24, 2015]

Tian, L., Luo, Y., Wang, Y., Wu, X., 2014 Prediction of transverse and angular distortions of gas tungsten arc bead-on-plate welding using artificial neural network Materials and Design, 54, pp.458–472 DOI: 10.1016/j.matdes.2013.08.082

Tsai, C.L., Park, S.C., Cheng, W.T., 1999 Welding Distortion of a Thin-Plate Panel Structure Aws, (May), pp.156–165

Tsirkas, S.A., Papanikos, P., Kermanidis, T., 2003 Numerical simulation of the laser welding process in butt-joint specimens Journal of Materials Processing Technology,

Vasantharaja, P., Maduarimuthu, V., Vasudevan, M., Palanichamy, P., 2012 Assessment of Residual Stresses and Distortion in Stainless Steel Weld Joints Materials and Manufacturing Processes, 27, pp.1376–1381 DOI: 10.1080/10426914.2012.663135

Vasantharaja, P., Vasudevan, M., Palanichamy, P., 2014 Effect of welding processes on the residual stress and distortion in type 316LN stainless steel weld joints Journal of

Veiga, C., Loureiro, A., Pina, J.C.P., Batista, A.C., 2002 Residual Stress Distribution in Butt Welded Joints – Effect of the Weld Groove Shape Materials Science Forum,

404-407, pp.387–392 DOI: 10.4028/www.scientific.net/MSF.404-407.387

Venkatesan, M.V., Murugan, N., Prasad, B.M., Manickavasagam, A., 2013 Influence of FCA welding process parameters on distortion of 409M stainless steel for rail coach building Journal of Iron and Steel Research International, 20(1), pp.71–78 DOI:

Venkatesan, M V., Murugan, N., 2014 Role of FCA welding process parameters on bead profile, angular and bowing distortion of ferritic stainless steel sheets Journal of Engineering Science and Technology, 9(1), pp.106–121

"Vernier Bevel Protractor"., 2015 Craftsmanspace Available at: http://www.craftsmanspace.com/knowledge/vernier-bevel-protractor.html [Accessed July 1, 2015]

Walford, A., 2007 Photogrammetry Available at: http://www.photogrammetry.com/ [Accessed July 2, 2015]

Wang, J., Shibahara, M., Zhang, X., Murakawa, H., 2012 Investigation on twisting distortion of thin plate stiffened structure under welding Journal of Materials Processing Technology, 212(8), pp.1705–1715 DOI: 10.1016/j.jmatprotec.2012.03.015

Watanabe, M., Satoh, K., 1961 Effect of welding conditions on the shrinkage and distortion in welded structures Welding Journal, 40(8), p.377s–384s

Xu, J.J., Chen, L., Ni, C., 2007 Effect of vibratory weld conditioning on the residual stresses and distortion in multipass girth-butt welded pipes International Journal of

Pressure Vessels and Piping, 84(5), pp.298–303 DOI: 10.1016/j.ijpvp.2006.11.004

Yu, H., 2008 Welding Parameters, Distortion and Mechanical Properties of AA7075 Lap

Joints in SSFSW Master of Science in Mechanical Engineering thesis North China

In their 2010 study, Zain-ul-abdein et al conducted an experimental investigation and finite element simulation to analyze the residual stresses and distortions induced by laser beam welding in thin sheets of AA 6056-T4 The research, published in Materials Science and Engineering A, provides valuable insights into the effects of laser welding on material integrity, highlighting the importance of understanding these factors for improved welding processes The findings, documented in volume 527, pages 3025-3039, contribute to the advancement of welding techniques and the optimization of aluminum alloy applications.

The study by Zain-ul-abdein et al (2011) employs finite element analysis to investigate metallurgical phase transformations in AA 6056-T4 aluminum alloy It examines how these transformations influence the residual stress and distortion in laser-welded T-joints, providing valuable insights into the welding process and material behavior.

International Journal of Pressure Vessels and Piping, 88(1), pp.45–56 DOI:

Zhu, X.K., Chao, Y.J., 2002 Effects of temperature-dependent material properties on welding simulation Computers and Structures, 80, pp.967–976 DOI: 10.1016/S0045-7949(02)00040-8

Tiêu đề	A Critical Analysis on Weld’s Distortion
Tác giả	Filipe David Santos Cordeiro
Người hướng dẫn	Dulce Maria Esteves Rodrigues, Carlos Miguel Almeida Leitóo
Trường học	Universidade de Coimbra
Chuyên ngành	Mechanical Engineering
Thể loại	Master's Thesis
Năm xuất bản	2015
Thành phố	Coimbra

Định dạng
Số trang	72
Dung lượng	1,77 MB