This lab uses the following skills: Fixtures on page 34. External Loads on page 38. Meshing on page 43. Multiple Studies on page 60.

Transcription

1 Exercise 1 Exercise 1: n this first exercise, you will analyze a simple part with a single restraint and one external force. This lab uses the following skills: Fixtures on page 34. External Loads on page 38. Meshing on page 43. Multiple Studies on page 60. Problem Statement The aluminum part of an assembly will be analyzed for its maximum stresses and displacements. The part is bolted to the rest of the assembly through the two bolt holes, as indicated in the figure. The part is then subjected to a normal force of 500 N, applied to the counter bored face. 1 Open a part file. Open part from the LessonOl \Exercises folder. 2 Specify SolidWorks Simulation options. Select Options in the Simulation menu. Oefautt Options- Units ; load/fixture!--mesh!--results 8--Piot r Color Chart f ti} D hult Plots L... User information Unit 51 [MKS] 0 Engim{PS] ejmoi< {G] u,;,, Length/Displacement Temperature: Pressure/Sbess: ' ""' Ko v l adlrec Tl Tl TJ N1mm4M TJ Select the Default Options tab, specify 51 (MKS) as a default Units for this analysis. n the Units dialog, set the Length/Displacement and Pressure/Stress fields to mm and N/mm 2 (MPa), respectively. 71

2 i Exercise 1 The following default results plots are generated after each static study is completed : nodal von Mises stress and resultant displacement. D fault Options - Plot- Static Plot r Units load/fixture 1--Mesh Results type: Nodal Stress... /, Plot Results component i Color Chart Er Dt!fault Plots! P1: lst Principal Stress j '!:!:! PloU Add N.w ot!--- Plotl Add N Folder it!:aplot3 - i $ Static StudyR ur-,..':::,-'"-'----==.:.;_ --' Right-click on the Static Study Results folder and select Add New Plot. Add an additional result plot for the nodal P1: 1st principle stress be generated as a default result plot. Default Options- Results SystemOptions Default Options 1'---!"" Units!... Load/Fixture. ;... Mesh id 8 Plot!!.. Color Chart, ii Default Plots L User information L. Report Defauh solver { Automatic 0Directsparse ej FFEPius Results Solid'V!Ofks document folder fll Under sub folder results User defined!: : pdata_\lo:_ - 1 [] Keep temporary database files To change the results folder for an e)(isting study. modify the option l.m'def the properties of the stu. Specify the subfolder results in the SolidWorks document directory as a location to store the result files. 3 Number format. Select Color chart. Select Scientific and 2 decimal places. 4 Define a static study. Number format (!)Scientific[e) OFtoatinolfl 0Genera g) No. of decimal places: Create a new static study named stress analysis. 72

3 Exercise 1 5 Apply material properties. Right-click on the Part folder in the FeatureManager and select Apply/Edit Material. Specify Aluminum 1060 Alloy solidworks materials ctt" stress analysis (-Def ult-) E)- l=. U co d Fix Treat as Remote Mass... llj Ext Qefirle Shell By Selected Faces.,, Me! 1: Exclude from Analysis from the Make Rigid library. Fix Details.. Add to New Eolder bopy Material $ Aloys t: El!l!mlll 1::!060-1<12 J:: 1060-H12Rod {SS)!::!060-1<14 J:: <16!:: 1060-H!B J:: 1060-H!BRod {SS) J;: 1060-<J {SS) J:: 1100-HilRod {SS) J::!100-!<16 Rod {SS) J:: OO-H26Rod {SS) J:: 1100-<J Rod {SS)!:: 1345 Aloy!:: 1350 Aloy ;: T43mUatl!dMoidC..tinQ(SS) J;: T61mulatl!d Mold C..tinQ {SS) J:: T71nsulatl!d Mold C.StinQ {SS)!:: 2014Aioy!:: 2014-<J J:: 2014-T4!:: 2014-T6 1:: 2018Aioy!:: 2024Aioy J:: 2024 Aloy {SN)!:: 2024-<J!:: 2024-TJ!:: 2024-T361!:: 2024-T4!:: 2219-<J. Properties To!llbles &. Oxves Appe:ar Y Ce CJoooHakh Cu.tom Application Data,2EJ prope'ties Ma in the defaultlibrarycm notbt: edited. Youmustfirstcopy the material to a rustom b'ary to edit it. Material tlodel Type: Units Category: Name: Default failure cnterion: Description: Source: 5ustainabi!ity: Property E\a$ticModulus. --- UneMElasticlsoOopic [51- N/m'2 (Pa)...,.,.., Aloys Aloy x Mlses Stress [o.m.d von i _; _:j --=:J Value 6.9e Z Units -2 NA _,. -3 Oensly -2 T... S1renglh _,..,_... Slrenglh.. X 2757.QOO _,. YieldStrength _._,Coo_ 2.- "' ConcOociMiy Wl(m-K)... Jl(tg-K) -- --NA. t Apply ' - lconfio... l 73

4 Exercise 1 6 Apply Fixtures. Apply Fixed Geometry to the two bolt holes, as shown in the figure below. This restraint simulates the way this part is attached to the rest of the assembly. Fixed Geometry fixtures are used in this exercise to model the bolted connections mounting the bracket to the other parts of the larger assembly. Also, the presence of the other parts to which this bracket is attached is ignored in this exercise. You will learn in the later lessons that more accurate and elegant methods and features, such as bolt connectors and virtual wall, exist to simulate these conditions. 7 Apply external load. Apply normal force on the face indicated in the figure. Specify a magnitude of 500 N. 74

5 Exercise 1 8 Mesh. Mesh the model using High quality elements with the default element sizes. 9 Run the study. 10 Plot stress results. We observe that the maximum von Mises stress in the model is approximately 35.1 MPa, which is above the yield strength of the 1060 Aluminum Alloy (27.5 MPa). 3.51e+001 3_22e e e e e e e e e+COO 5.87e+OOO 2.9Se+OOO 2.77e Yield strength: 2.76e

6 Exercise 1 The distribution of the P1: 1st principle stress indicates a maximum value of approximately 32.6 MPa. This value corresponds to the maximum tensile stress in the part (maximum compressive stress where the value is negative). P1 (N!nm"2(MPa)) 3.26e Probe stress on the fillet. Later in the course you will learn that the fixtures may result in stress intensifications which are not real. For this reason, we will focus our attention to the filleted region between the horizontal and vertical bosses on the part. Right-click the Stressl folder and click Probe. Select On selected entities, then pick the seven faces of the fillet between the two bosses. Click Update. 76

7 Exercise 1 Options (} At location From sensors On selected entities Results "' rn are<6> ift#+ : [] Flp edge prot r L.l>da"' l 1 <1</rrm '2 >lj.>, S.O'le-1000 [} e e e e+OOO e Se e+OOO. ' ' - SUmmary Value N/rrm'2(M N/rrm'2(M N/rrm'2(M Min N/rrm'2(M N/rrm'2(M "' Probing the results on selected faces we see that the maximum stress at this stress concentration region is 31.4 MPa [4,547 psi], which is slightly above the yield strength of27.5 MPa [3,989 psi]. 12 Plot displacement results. We observe the maximum resultant displacement of approximately mm [ in]. URES(mm) 6_78e e e e e e e e Se e

8 Exercise 1 Coarse Mesh and Element Stress Are our current results accurate enough? Visual inspection of our finite element mesh suggests that it may be rather coarse, especially in the regions where the fillets are present. Furthermore, inspection of the distribution of the elemental values of the von Mises stress indicates considerable stress jumps from element-to-element in the higher stress concentration areas. von Mises (NAnm"2 (Mf'a)) 2.58e e e e e e e e e+OOO 6.49e+OOO 4.34e+OOO 2.19e+OOO 4.01e Yiek:ls1rength: 2.76e+001 We will repeat the analysis with finer mesh. 13 Create new static study. Duplicate the study Static analysis as a new study named stress analysis - refined. The folders Fixtures, External Loads, Parts, Mesh, and Results will be copied into the new study as well. 14 Create fine mesh. Create High quality mesh. Slide the Mesh Density slider all the way to the right which will result in an Maximum element size of mm and a Minimum element size of0.733 mm. 78

9 Exercise 1 The resulting mesh shows significantly improved mapping of the model geometry. 15 Run the study. 16 Plot stress results. We now observe that the maximum von Mises stress increased from 35.1 MPa to 39.1 MPa, which is above the material yield strength of the 27.5 MPa. This translates to a difference of nearly 11%. However, if we examine the plot, we will see that the maximum stress is at the sharp corner of the bolt holes. We will discuss this further in the next lesson. von S (Nimm"2 (MP11)) 3.91e e e e e e e e e e-t e+OOO 3.28e+OOO 2.02e il> YJeki strength: 2.76e Probe stress on the fillet. Using the identical procedure described in step 11 probe the stress results on the filleted geometries. We can observe the maximum von Mises stress on these entities dropped from 31.4 MPa to 30.8 MPa, which is slightly above the yield strength. This represents a difference of about 2% which may or may not be acceptable depending on the design criteria. t should be noted that in other situations the difference in the stress results may be significant. n general, requirements on the good stress results translates into a necessity to generate finer meshes. n our present case further refinement does not produce further improvement in the stress results and we will thus conclude that they are converged. 79

10 Exercise 1 18 Plot displacement results. The above plot shows that the maximum displacement resultant increased from mm to mm; a difference of less than 1 %. l.jres(mm) 6.78e e e e e e e e Se ]Oe e e e Save and Close the file. Summary n this exercise, we practiced the basic setup of the linear static study as well as the post processing features available in SolidWorks Simulation. We observed that the mesh quality has a significant impact on the results (especially the stress results). While the deviation in the resultant displacements obtained from the two studies was 1 %, the deviation for maximum von Mises stresses was nearly 11 % (often the difference in stresses is much greater). The greater difference in the maximum stresses is attributed to the following two phenomena: Displacements are the primary unknown in the finite element analysis and, as such, will always be significantly more accurate than strains and stresses. A relatively coarse mesh is sufficient for satisfactory displacement results, while significantly finer mesh is generally required for satisfactory stress results. The extreme values of the stresses occur in the vicinity of the fixture where the stresses often assume unrealistically high values. This is a subject studied in the next lesson. The stresses at the filleted regions reported in both studies were closer in their magnitudes with a relative difference of only 2 %. Finer meshes are required in filleted regions as stress results are of importance to us. 80