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Weld,Bolt, BearingandShrinkFitSimulation 10.1WeldingSimulation Welded Joint Spot Welding (point connection) Arc Welding (line connection) Mostofthe real lifefailures are reported at either stress concentration points or at bolted, welded joints.Failureof bolted welded joints is due to fatigue (dynamic loading). In our house or office, there are many components which are bolted or welded but since the nature of loading is static, veryrarelywe notice failure of these components. Forexample please consider following bracket at ouroffice. '. Ithasbeen there for last 12years and probably it would remain as it isfor next 100 years, because the nature of loading is static {wallremains stationary as well as applied load}.Now if the same bracketis mounted on gear box or clutch housing or chassis of a moving vehicle, it will fail in shorttime at either bolted or welded joint. Someimportantpoints to be rememberedwhilecarryingout the weldjoint analysis ) Staticstrength of weld ~ Static strength of parent material ) Fatiguestrength of weld «< Fatigue strength of parent material 143Iteration 3: Single central stiffener (bracket as well stiffener thickness =3 mm) -----..---.-----.-_.---.--..-.-_-..--.----. '_1 a= 126N/mm1 Iteration 4:Two side stiffeners (thickness =3 mm) Single central stiffener Two sideways stiffeners Stress =131 N/mm1 Stress I N/mm' Mass ; kg 126 131 II 0.874 1.051 Singlecentral stiffener is more effective from stress as well cost (mass) point of view. There is furtherscope to reduce the cost by reducing the thickness (such that stress magnitude will be aprox.200 N/mm2) Iteration 5: Reduction of thickness Single central stiffener (bracket as well stiffener thickness =3 mm) Single central stiffener (bracket as well stiffener thickness =2.3 mm) Stress N/mm' Mass kg 126 0.670 0.874 192 181Common Mistakes and Errors In the following pages we are sharing mistakes made by us and observed by CAE engineers working in different organisations. Common CAEmistakes CAE Engineers Marketing Engineers Managers System Administrators HR CAEEngineers: 1) Submission of job without proper checking (should be cross checked by minimum 2 CAE engineers) : Checking work of someone else is a rather boring & not willingly accepted job. But it is very important and ajob of high responsibility. Checking and rechecking all the details, ensures good quality and minimum mistakes. A CAE service providing company, submitted meshing job to their regular overseas client, everything was perfect except material properties. The analyst at the customer end was quite satisfied about error free models submitted by this CAEteam over the years. He blindly started analysis without checkingmaterial properties. At the later stage big difference was noticed in the results of current analysis and the previous one carried out for similar model. After checking both the models carefully, analyst realized difference in material properties. "Please be careful before submitting your work and check it several times and then askyour colleague for the same".Also always request your client to check the model in every aspect before starting the analysis. 2) Import I Export errors: Some ofthe preprocessors do not export all the elements & boundary conditions as it is unless special options are turned on or special translators are used. One CAE group exported a big mesh model with template setting for a specific external solver. Some special elements (RBE3 elements) were not exported due to translator problem. These were extra rigid connection & were not resulting in rigid body modes during free-free check. Analysis was carried out as it is by an analyst in other country. Based on CAEresults, CADengineers released the drawings & prototype was prepared. Test results were not satisfactory and further modifications were suggested. Updated CADdata was provided again to the same meshing group.Changeswere local and it was to be carried out on earlier submitted model. Bythis time the CAEgroup had upgraded version of pre-processing software and export operation was 100% successful i.e. all the elements including earlier missed were exported properly. Results for modified model showed drastic difference in comparison to original. After careful checking and comparing number of elements analyst realized that few rigid elements were missing in the first model. Hundreds of engineers had worked on the job in the meantime (CAD,prototype, testing, planning etc.), now who is responsible for this delay & cost, whether the analyst or service provider or the pre-processing software. "It's strongly recommended to import the mesh 407Preparation for CAEInterview CAEinterview Short written test Meshing /Analysis test Interview What is expected from meshing I analysis test? Software skill: Experienced CAEengineer can evaluate the performance and efficiency just by observing hand movement and the way your are operating keyboard and mouse, even from a distant place. Submitted meshing job is checked for 1. Howmuchworkcompletedwithinallotted time 2. Methodologyfollowed 3. Meshflowpattern 4. Patternaround holes,geometricaldiscontinuitiesand joints 5. Meshquality,freeedges /faces,shellnormaletc. 6. Whetherfree-freerun or dummylinearstaticanalysiscarriedout Analysis job (ready-made mesh model is provided to the candidate) is checked for 1. Whether mesh model was checked properly before starting analysis 2. How the specified boundary conditions were applied 3. Analysiserrors and warning message, and how you tackled it 4. Aftercompletion of run whether numerical accuracy checks applied (residuals, convergence test etc.) 5. Conclusions from the analysis and suggestions for design modification Commonly asked questions (written test paper or during the interview) FEAtheory: 1. What is Finite Element Analysis. 2. What is degree of freedom (dof)? Drawfollowing elements with their dof. a. Quad 4 411123456789 10 11 12 13 14 15 16 17 18 19 20 21 22 23