solidworks simulation tutorial REVISED.pdf

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solidworks simulation tutorial REVISED.pdf

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    SolidWorks Simulation 14 June 2011

    Sam Ettinger, HMC 2012

    Objectives

    By completing this tutorial, you will learn to conduct finite-element analysis (FEA) tests on

    SolidWorks models using the Simulation add-on.

    Introduction

    Finite-element analysis (FEA) is useful in predicting a models response to various influences such as forces, torques, periodic excitations, and heat. FEA is used to analyze large or

    complicated models where analytical solutions are not possible. FEA software breaks the model

    into thousands of small tetrahedral elements and solves numerically for each one individually.

    Some of the leading commercial FEA tools include COMSOL, Ansys, and SolidWorks

    Simulation. This tutorial covers SolidWorks Simulation because it is a comfortable environment

    for those who already know 3D modeling with SolidWorks. SolidWorks Simulation is primarily

    applicable to mechanical and thermal models. COMSOL specializes in multiphysics problems

    involving interaction between mechanical, thermal, and electrical behavior. Ansys also addresses

    mechanical and thermal simulations and has advanced capabilities required in certain fields.

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    This tutorial will cover three of the simulation studies available in SolidWorks Simulation:

    Static analysis, for identifying stresses caused by static loading

    Frequency analysis, for identifying resonant frequencies and associated mode shapes

    Thermal analysis, for identifying heat flow through a model Mastering these three gives you the tools and experience necessary to make use of any of the

    remaining simulation studies. We will use the same model, a wine glass, for each study.

    Before you begin

    On two occasions I have been asked, Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?...I am not able rightly to apprehend the kind of confusion of ideas that could provoke

    such a question.

    - Charles Babbage, Passages from the Life of a Philosopher, 1864

    Since the very beginning of computing, users have been plagued by bad outputs as a

    result of bad inputs. FEA is particularly prone to such problems, generating pretty

    pictures that often have no bearing on reality. As a general rule, if you dont know

    what to expect, the results you get are probably incorrect and certainly unusable.

    Some common reasons for error include making invalid assumptions, setting incorrect

    boundary conditions, setting incorrect material properties, and general numerical

    errors. As an example, lets consider the stress analysis of a typical model. One can assume a linear stress-strain relationship before the yield strength of the material is

    reached. The model produces incorrect results as stress or strain increase to the point

    of nonlinearity on the stress-strain curve.

    Setting appropriate boundary conditions can be more difficult than one might first

    expect, and it is easy to overlook boundaries (such as the initial temperature of an

    object). This can result in nonsensical default values being used for the simulation.

    Obtaining accurate physical parameters for your materials can also be difficult,

    especially if you are using nonstandard or unusual materials.

    FEA inherently discretizes the object being studied. The number of elements used

    presents a tradeoff between runtime and accuracy.

    Before you trust your FEA results, you should plan for a significant validation process.

    If possible, the best place to begin the validation process is with a simple model that

    can be solved analytically. Check that the FEA simulation produces comparable

    results. For example, before looking at bending in an array of bolted-together I-beams,

    compare the FEA results for bending in a single I-beam to analytical results. Be sure

    you are using the appropriate material parameters. Another important model validation

    technique is to compare the FEA results to an actual physical prototype using simple

    stimulus, such as an impulse. Beware of making claims about the FEA model results

    that you cannot independently support with other analysis or measurement.

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    Getting the model, defining the material

    SolidWorks is, first and foremost, a 3-D modeling tool. Look in the tutorials folder for a

    SolidWorks model named glass.SLDPRT. When you open it, it should show a wine glass, as in Figure 1. This is the model we are going to study in this tutorial. Save a copy to your Charlie

    account.

    If you wish to practice your modeling, part of a technical drawing of this wine glass is included

    in Appendix A. Units are in millimeters. This should be enough information to draw your own.

    Figure 1. The wine glass model.

    To use the model of the glass in Simulation, we must specify the material that the model is made

    of. Can you guess what material we want the model to be? Thats right, glass! You can specify a material in the Feature Manager design tree on the left-side panel. There should be an icon

    named Material , as in Figure 2. Right-click this and choose Edit material to be brought to the Materials window, shown in Figure 3. Glass is found in the folder SolidWorks

    Materials > Other Non-metals. Click Glass, then click Apply and Close. Your model should change from opaque grey to transparent grey, as in Figure 4.

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    Figure 2. How to change a model's material.

    Figure 3. Materials window.

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    Figure 4. The glass, now shown as glass.

    Opening Simulation for the first time

    By default, SolidWorks Simulation does not open when SolidWorks does. We can change this by

    going to Tools > Add-Ins, shown in Figure 5.

    Figure 5. How to start Simulation.

    The Add-Ins window, replicated in Figure 6, pops up. Check the box to the left of SolidWorks Simulation to enable Simulation in this instance of SolidWorks. If you want Simulation to be enabled every time you start SolidWorks, check the box to the right of SolidWorks Simulation as well. If this is your first time using Simulation, you may be asked to agree to an end-user

    license agreement.

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    Figure 6. The add-ins window.

    If all goes right, there should be a new tab named Simulation in the upper-left, next to Features, Sketch, Evaluate and the like. Now we can begin our first study!

    Static analysis

    As mentioned above, static analysis computes the effects of static loading on a model. It can

    display stresses, strains, displacement, and the factor of safety at each segment of a model. In

    Simulation, one has to specify the location and magnitude of each load, as well as to specify

    where and how the model is supported. Identifying where stresses are highest/lowest quickly

    shows the designer where a model can be improved by adding support or by removing excess

    material.

    We are going to investigate what happens when a 5 kg load is placed on the lip of a glass set

    upright on a table. Lets assume that placing the glass on a table can be best approximated by a perfectly fixed support on the entire bottom face of the wine glass base. Furthermore, lets assume the 5 kg load is best approximated by a 50 N force pushing against the lip of the glass

    with uniform distribution. In models of large objects, it is often advisable to include gravity in

    the simulation, but that is not necessary for our 10-cm-tall wine glass.

    To create a static study, click the Simulation tab in the upper-left. There should be a button

    labeled Study Advisor. Click the arrow just beneath it and choose New Study, as in Figure 7. Here you can see all the types of studies available in Simulation. Click Static, name the study something memorable, and click the green check mark.

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    Figure 7. Starting a new study.

    Below the normal display pane on the left, a static study pane should open. We can use this or

    the Simulation tab along the top of the screen to specify our fixtures and loads.

    To set up the fixtures on the model, either right-click Fixtures in the static study pane or click the arrow beneath Fixtures Advisor in the Simulation tab. Choose Fixed Geometry as the fixture type for this study. This is shown in Figure 8. You can also have supports such as pins,

    rollers, or hinges, if your model requires it. For now, though, the fixed geometry suffices. When

    you click Fixed Geometry, the Fixture pane opens on the left. Select the bottom face of the base of the glass and press the green check mark. You can select multiple faces at a time, if you

    wish, but for this example only one face is fixed.

    Figure 8. Adding a fixture.

    To specify our 50 N load, right-click External Loads in the static study pane or click the arrow beneath External Loads Advisor in the Simulation tab. As you can see, there are lots of

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    possible options for loading, but we just care about the simplest one, Force. Click that to be taken to the Force/Torque pane. Click the lip of the glass (you may have to zoom in a ways to

    make sure you are selecting the whole face, not just one edge) to select it as the face being

    loaded. Rather than having the load normal to the lip, lets specify the load as directly down (as it would be in reality). To do this: in the Force/Torque pane, change the direction of the force from

    Normal to Selected direction, then choose the Top Plane in the design tree just to the right of the Force/Torque pane.