Tài liệu Guide Block – 3-D Stress Analysis Pro/ENGINEER and Pro/MECHANICA docx

If your analysis does not reach convergence during a design study, the results may not have the desired accuracy.. Select one of these convergence methods for Mechanica to use when it ru

Guide Block – 3-D Stress Analysis Pro/ENGINEER and Pro/MECHANICA

By: Dr Herli Surjanhata

PREPARING THE MODEL

Before beginning this problem, create a separate folder on your computer for this job Download the file and put it in this directory Set Pro/E working directory to this folder

Open the guide block

Click to open guide_block.prt

Make sure the units is millimeter Newton Second by selecting

Edit -> Setup -> Units

Click Close in the Units Manager dialog box

Done

The part to be analyzed is shown below:

Select Material The Materials dialog box appears

Pick steel.mtl on the left column, and click to move it

to Materials in Model box

Double STEEL or click to edit the current material

Be sure the Units are in Newton-second (mmNs) as shown in the dialog box located on the left Click OK

millimeter-Click on Thermal tab, and the units are in mmNs as shown in the figure on the left

OK

OK to close the

Materials

dialog box

ENTER Pro/MECHANICA STRUCTURE AND ASSIGN

MATERIAL PROPERTIES, DEFINE LOADS, AND APPLY

CONSTRAINTS

Applications -> Mechanica

Make sure the units are correct

Click Continue

Click OK to accept Structure Mode

Select to assign the selected material to the plate model

The Material Assignment dialog box appears

Be sure that STEEL is display under

Enter -890 N force for Z-component Click Preview

Click OK on the Select box to accept the

Click OK to close the

Constraint dialog box

DEFINE AND RUN THE ANALYSIS

Mechanica's automated process for generating geometric elements on a model AutoGEM generates elements that comply with all element creation rules and that provide accurate results when Mechanica analyzes your model

To see how the geometric elements on a guide block,

Close the AutoGEM Summary dialog box

Close the AutoGEM dialog box

Yes to save the mesh

Create a static analysis and give it a name Choose the default options when defining the analysis

Click

File -> New Static

Convergence Method

Convergence gives you an idea of how accurate your results are If your analysis does not reach convergence during a design study, the results may not have the desired accuracy In this case, you need to modify your model

Select one of these convergence methods for Mechanica to use when it runs your analysis:

• Multi-Pass Adaptive — Mechanica calculates results at increasing polynomial

orders until convergence criteria are satisfied

• Single-Pass Adaptive — Mechanica runs a first pass at a polynomial order of

3 and determines a local estimate of stress error Using this error estimate, Mechanica determines a new p-order distribution and performs a final pass

• Quick Check (No Convergence) — Mechanica performs a single pass at a

uniform polynomial order of 3 You can use this method to verify that you have defined your analysis correctly

Multi-Pass Adaptive Convergence Method

When you run a design study, the Structure engine performs calculations and

increases the polynomial order for each element edge until the convergence criteria are satisfied (The polynomial level for edges on which beams and 2D shells lie begins with either the third order or the order you enter on the analysis definition dialog box, whichever is higher)

An analysis converges when the difference in the results of the current pass and the

previous pass is within the percentage you specify under Convergence

Single-Pass Adaptive Convergence Method

Single-pass adaptive convergence applies to static, modal, buckling, and contact analyses of all element types Models may consist of isotropic and/or orthotropic materials While the single-pass adaptive option is available for contact analysis, we

do not normally recommend its use because it can increase run time

Mechanica runs a first pass at p=3 and determines a local estimate of stress error Using this error estimate, Mechanica determines a new p-order distribution and performs a final pass

If you use the iterative solver, Mechanica runs a first pass using the block solver at p=2, followed by a second pass (p=3) using the iterative solver Using the stress

With single-pass adaptive analysis, you do not control the convergence tolerance, but you do need to examine the stress error estimates reported in the run summary

If these error estimates are acceptable, then continue to use single-pass adaptive convergence for efficiency

If the error estimates from the single-pass adaptive convergence tolerance are not acceptable—for example, the stress error estimates are too large—then switch to the multi-pass adaptive convergence strategy for subsequent design studies

Quick Check

Define and run an analysis using the quick check convergence option With this option, the engine runs the analysis at a polynomial order of 3 You can then check stress and deformation results for structural analyses, or temperature gradient and flux results for thermal analyses These results can reveal problems in the model, such as cracks or missing loads and constraints

Convergence Percentage Calculation

Mechanica calculates the convergence percentage in the following ways:

• When you run a design study, the engine performs calculations at increasingly higher polynomial orders for each element edge An analysis converges when the difference in the results of the last two calculations is within the

percentage you specify here

• The engine finishes calculating results when the analysis converges, or when it has reached the maximum polynomial order that you specified

• Lower convergence percentages yield more accurate results, but Mechanica may take longer to reach convergence You should balance the level of

accuracy you need with the amount of time it will take to run a design study containing this analysis

Be sure the Convergence tab is selected, form the list select Multi-Pass Adaptive

Increase the Polynomial Order to 9

Set the Percentage Convergence to 5 percent Click OK

Click

convergence was NOT reached

It might caused by the stress

concentration

at the entrance corners in the part

re-This must be fixed by introducing fillets – see assignment

When the run is completed, click

Close

REVIEW THE RESULTS

Click

Enter the name vm Type Von Mises

Stress Fringe Plot

under Title Click Display Options tab

Check Continuous Tone, Deformed Keep Show Loads

and Show Constraints checked Click OK and Show

Change the background color to white

Format -> Result Window…

From the list, select White Show the location of the max von Mises stress

Info -> Model Max

Spin the model to investigate the location of max von Mises stress

As predicted, there is high stress concentration at the sharp corner

Create the displacement result window

Click to copy the existing

Enter the name displ Type Displacement

Fringe Plot under

Title Click Quantity tab

Change to

Displacement as

Quantity to be displayed

Click OK

Create max von Mises stress convergence plot

Click to copy the existing

Fill the information for Name and

Title as shown

Click Quantity tab

Under Display type, change it to Graph

For Quantity, select Measure

Click to select Measure to

be plotted

The Measures

dialog box appears

Select the

max_stress_vm

OK

Be sure to change the background color to white

Edit the displacement result window by selecting , and animate the displacement When done, uncheck the animate option

Click

Select conv results to be displayed

Exit the Result Windows

Save the model

ASSIGNMENT

Introduce 3 mm radius fillets at sharp corners as shown below

Run the analysis of model with the same material, load, and constraints

Be sure to submit the following information with your report:

• Model with Elements, Loads, and Constraints

• Capture the Result Status window showing the solution is converged

• Von Mises Stress Distribution Fringe Plot – show Model Max What is the magnitude of max von Mises stress? Is the part is going to fail if AISI 1020 Hot-rolled steel to be used – see Table below?

• Displacement Distribution Fringe Plot - show Model Max What is the

magnitude of max displacement and where it is occurred?

• Convergence of Max von Mises Stress Plot

Use colors for figures of model, stress and displacement Change the background color to white