Tổng quan về dập thủy tĩnh

Tài liệu mô tả tổng quan về Công nghệ dập thủy tĩnh, cụ thể hơn ở đây là tạo hình phôi ống dưới áp suất cao bằng máy ép thủy lực. Tài liệu gồm 150 trang Slide mô tả tương đối chi tiết về công nghệ này, để tìm hiểu sâu thêm cũng như nghiên cứu chi tiết hơn các bạn nên nghiên cứu song hành trên các phần mềm mô phỏng tạo hình phổ biến như: Autoform, Dynaform, Deform...

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Sheet & Tube Metal-Hydroforming

INSTITUTE OF METAL FORMING

Address:

C5 – 303 ; C10 - 301

Hanoi University of Technology

No 1 Dai Co Viet Road – Hanoi – Vietnam

Tel. 04 - 8692430

E-mail contact@giacongapluc.com

Web: giacongapluc.com

PhD Nguyen Dac Trung

Vice Director / Assistant Professor

Address:

C5 – 303 ; C10 - 301

Tel. 04 - 8692430

Address:

C5 – 303 ; C10 - 301

Tel. 04 - 8692430

Address:

C5 – 303 ; C10 - 301

Tel. 04 - 8692430

Address:

C5 – 303 ; C10 - 301

Tel. 04 - 8692430

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1 Preamble, Introduction

2.1 (Tube) Hydroforming (IHF)

2.2 High-Pressure-Sheet-Metal-Forming (HSF)

2.3 Hydromechanical Deep Drawing

2.4 Fluid-Cell- and Rubberpresses

Highspeed Forming Processes: Explosive-Forming, Electrohydraulic Forming

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Hydroforming consists of two divisions, tube and sheet metal forming

Hydroforming

The two divisions are processed using similar techniques that are

developed to manufacture the different products

The basic principals for the different techniques are to use fluid pressure to

form a part

INTRODUCTION

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Products of Sheet Hydroforming

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Sheet Metal Parts I

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Tube products

Numerous applications of hydroforming can be seen in

exhaust manifolds

(duong ong khi thai) ) made of

stainless steel tubes

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Lightweight Constructions

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Sheet Metal Parts II

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Sheet metal hydroforming

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Tube hydroforming

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Hydroforming, (fluid forming or rubber diaphragm forming), was developed during the late 1940s and early 1950s in response (c©u tr¶ lêi) to a need for a lower cost method of producing relatively small quantities of deep drawn parts

History

The Verson Allsteel Press Company, Chicago, acquired (obtained) the

Hydroform press line in 1975 and embarked (b¾t tay vµo viÖc) on an aggressive program of equipment modernization The speed and forming capabilities have

been greatly improved

What is Hydroforming?

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Today, Hydroform technology provides an attractive alternative to conventional matched die forming, especially for cost-sensitive, lower volume production,

and for parts with asymmetrical or irregular contours

Based on the success found using a hydrostatic pressure to delay the onset (appear) of fracture, the idea of stamp hydroforming was investigated both experimentally and numerically as a possible method for shaping aluminum and ferrous sheet metals The process of stamp hydroforming, unlike conventional stamping, involves supporting the bottom of the sheet with a bed

of viscous fluid during the stamping process This external support provides a through-thickness compressive stress that delays the onset of tensile

McClintock (1968), Rice and Tracey (1969) embarked the studies on sheet metal blanks that demonstrated rapidly decreasing fracture ductility as a hydrostatic pressure, applied across the material, was increased Clift, Hartley, Sturgess and Rowe (1990), Hartley, Pillinger, and Sturgess (1992) demonstrated that for sheet metal draw blanks, the use of a hydrostatic pressure prevented the initiation and spreading of microcracks within the metallic material

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Benefit, Advantages of Hydroforming

The first, and probably most obvious (clearly), only a male die and a blank holder will be needed There is no need to fit a female die to the punch

(không cần điều chỉnh cối vừa khít vào chày), which means that more complex shapes can be easily formed Set-ups are quick and simple The tooling is self-centered and self-aligning

Since the pressure is adjusted on a continuous basis, parts which might take two or three conventional deep draws, now can be done in one hydroforming operation This reduces costs that are related to the finishing

of the final part

Due to the fact that the metal is not bent (uốn) or stretched (kéo căng) but formed around the punch, the material thin out in the walls of the part is usually less than 10% Thus, thinner blanks can be used to form the parts desired (required) This is good, when using expensive materials or when weight is of ciritcal concern, as it is in the aerospace industry At the same time, the material is not work-hardened as it would be for a normal drawing process, so the end part usually does not have to be annealed

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Benefit, Advantages of Hydroforming

Inexpensive Tooling: Only a male die (punch) and a draw ring (blank holder) as

tools are generally required Hydroforming tools normally cost at least 50% less

than conventional press tooling

Versatility (flexibility) in Forming Complex Shapes and Contours: Irregularly

contoured shapes are easily formed using the Hydroform process because

matching dies are not required

Savings in Finishing Costs: Matched die methods of forming can cause scuff

(chay xuoc) marks (dau hieu), shock and stretch lines In the Hydroform method,

the wrapping action of the flexible diaphragm virtually eliminates these faults

Savings of up to 90% in finishing costs have been realized

Materials Versatility: Practically all sheet metals capable of being cold formed

carbon steel, aluminum, stainless steel, copper, brass, precious metals, high

strength alloys, and others can be Hydroformed Thickness of materials can

vary (thay doi) within the limits of the machine without need for tool revisions

(reparation)

Precision: The Hydroform method forms parts with extremely difficult

configurations while at the same time working to precise tolerances

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Ease (sự thoải mái) of Design Change: With Hydroforming, material or metal

thicknes can be altered usually without any tooling change being necessary

Hydroforming can also eliminate or minimize the number of multiple draw

operations required, with a corresponding (tuong ung) reduction in tryout

costs

Low Work-Hardening: Hydroforming does not cause work-hardening of

material at the same rate as conventional drawing operations Consequently,

annealing between draw operations is rarely required The need for multiple

draw operations can often be eliminated, too

Benefit, Advantage of Hydroforming

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Summary:

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Some of the difficulties surrounding this process are the pressures involved in forming the piece Because the pressures involved are usually three to four times those normally associated with deep drawing, careful attention should be paid to the pressure vessel

(chamber) , so that none of the fluid leaks (rò rỉ, thoát ra) If too little pressure is applied, the part will wrinkle, resulting in poor quality If too much pressure is applied, the blank will sheer and the part will have to be scraped

With every process there are risks Hydroforming is no exception

Hydroforming does not lend itself to low volume runs, there needs

to be a high volume of parts to spread the tooling costs There are also a couple of specific drawbacks which relate directly to the process Pierced holes have small deflections around the area of impact (influence) For tube forming the tube has to take a shape that is workable by the tube bender The risks show that

hydroforming is not the cure (solution) all but has great potential in

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2 Quasistatic Workingmedia based Forming Processes

2.1 (Tube) Hydroforming (IHU)

2.2 High-Pressure-Sheet-Metal-Forming (HBU)

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Calibrating with Fluid Pressure (Patent 1900)

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Overview of the Forming Procedure

Deep drawing with working media with force-bounded effect

Deep drawing

with rigid tool

Deep drawing with working media with working energyDeep drawingDeep drawing

with tool

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Working Media Based Forming Processes

Semifinished

material

( sheet )

Plane or open

( tubes, double-sheets )

Partly closed ( sheet )

Plane or open

Direct Indirect Direct Indirect Direct Indirect Direct Indirect

Tool movement Working media pressure

Working media

contact

Initiation of

forming

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2.1 (Tube) Hydroforming (IHU)

2.2 High-Pressure-Sheet-Metal-Forming (HBU)

2.5 Pneumomechanical Deep Drawing (PMT)

3.1 Mechanical Processes

3.2 Explosive-Forming

3.3 Electrohydraulic Forming

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1 Overview - Basis of the internal high pressure forming of tubes

Content for 2.1

2 Punching, piercing, trimming by Internal high-pressure forming

3 Joining by Internal high-pressure forming

4 Determination and assessment of finished part properties

5 Simulation of IHF process

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1.1 Process definition

1.2 Basic principle

1.3 Process characteristics

1.4 Scope of using of IHF

1.5 Input parts for internal high pressure forming

1.6 Production means for the internal high pressure forming

1.7 Process design

1.8 Failure cases in the internal high-pressure forming

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1.1 Process definition

IHF is shaping with high pressure of medium, where the input hollow parts with

simple geometry (example pipes) under fluid high pressure will be formed follow

cavity tool and transformed to the hollow parts with complex geometry

Tube hydroforming has been well-known since the 1950s

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Hydroforming of Tube

Now a day, with recent advancements in computer controls and high-pressure hydraulic systems, the tube hydroforming process has become a viable (feasible)

method for mass production, especially with using of internal pressures of up to 6,000 pounds per square inch (PSI).

Modern machines have independent control

of axial feeding (ong dan) , internal pressure, and counter pressure, which increases the material-shaping capability of the process more than traditional forming methods.

Fluid pressure within the tube is increased after the die closes to force the material into the deformation zone During this process, axial feeding and internal pressure are controlled simultaneously to improve the process's material-shaping capabilities

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1.2 Basic principle

Principle of IHF and IHF-punching

Mediums: water, oil, emulsion…

The applied internal pressures is from pi = 1000 to 10000 bar and maybe greater

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0 20 40 60 80 100

Axial distance in mm

Active fluid medium

insertion of a work piece

Fixing of the work piece and closing of the mould

Fp = Conterholding force

Flow Chart (flow diagram) of Forming Process for the Production of T-Pieces

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1.3 Process characteristics

Forming under tensile and compressive conditions

Internal high pressure forming

of tubes

Expansion-upsetting

in a closed tool

upsetting

Expansion-in an open tool

Forming under tensile conditions

Forming under bending conditions

Forming under shearing conditions

Expanding Calibrating Bending Shifting

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Advantages and Disadvantages of Hydroforming

Hydroforming tubular components offers several advantages, including:

1 Part consolidation

2 Weight reduction through more efficient section design and tailoring of

the wall thickness

3 Improved structural strength and stiffness

4 Lower tooling cost as a result of fewer parts

5 Fewer secondary operations

6 Tight dimensional tolerances and low springback

7 Reduced scrap

Hydroforming also has some drawbacks ( restriction) , including:

1 Slow cycle time

2 Expensive equipment

3 Lack (need) of extensive knowledge base for process and tool design

Tube hydroforming allows engineers to optimize their designs through cross

sectional reshaping and perimeter (chu vi) expansion Combined with the

ability to inexpensively create the holes that are required for vehicle

subsystem interfaces, hydroforming has become a critical technology for

structural components in mass-produced vehicles

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1 Preparation of tubes, which involves material selection and quality of the

incoming tube

2 Preform design and production method

3 Part design for hydroforming

4 Welding and assembly of hydroformed components - - that is, fixturing and

joining

5 Crush performance and joint stiffness

6 Selection of a lubricant that does not break down at high pressures

7 Rapid process development

Some attentions

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IHF with only internal high pressure

IHF with more external forces

Fa = Fa min = pi*Ai

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IHF in an open die

Combination of IHF and bending

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Process steps by IHF

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Warm IHF Technology

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1.4 Products of IHF

Collecting tube

Camshaft

Integral beam of trucks

Applications in : taps, body part of car, chassis of car, Spaceframe

Manifold Variants

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1.5 Input parts for internal high pressure forming

The properties of finished part are depend on:

- material and geometry of initial tube,

- hydroforming processing,

- technological parameters.

In these aspects, the initial parts of the following requirements:

- as same as possible the finished parts

- simple geometric shapes,

- low-cost production,

- appropriate material holdings (cung cap vat lieu phu hop)

The initial parts can be:

- Hollow, in particular pipes with / without welding line (extrusion, rolled bending, tailored tubes, etc.),

- Seal joined of flat sheet,

- Shaped bottle

- Special shapes

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The geometry and material properties of initial tubes play very important role by

IFH

The initial parts should be similar form in compare to form of finished part,

manufacture easy and inexpensive, and have a large enough formability

At the same time, in the area of main form zone there is enough material available

For the high pressure forming can be applied the following tube:

- Tube, hollow profile with / without welding line

- Double sheets

1.5 Input parts for internal high pressure forming

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Production means for internal high pressure forming

Close, keep closing,

open the dies

Geometry of tube

Additional functions

Internal pressure Medium and sealing

Control / Adjust

The manufacturing with fluid medium (forming, punching, piercing, joining with

internal high pressure) needs special equipments, that can produce the finished

parts with required properties, with minimum technical and economic efforts

- Machine for closing tool

- Axial-Cylinder for creating axial forces

1.6 Production means for the internal high pressure forming

Necessary equipments:

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