ANSYS Tutorial Design Optimization

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ANSYS Tutorial: Design Optimization in DX ANSYS Workbench Tutorial: Want to know more about you model? Run a What if scenario? How sensitive are you results for changes in the input variables? Maybe optimize your model in terms of weight? Then DesignXplorer is the tool for you. This article will first give you a short summation of what DesignXplorer is and then show how to set up a simple optimization.

What is DesignXplorer? Design Explorer is based on a method called Design of Experiments (DOE). This together with various optimization methods helps the program to develop an optimized structure based on selected input and output parameters. Input parameters can either come from DesignModeler or from various CAD systems. These parameters can be in terms of thickness, length, etc. They can also come from Mechanical in terms of forces, material properties, etc. The output parameters are calculated in Mechanical and can for example be in terms of total mass, stress or frequency response. After setting up an analysis with a number of input parameters and out parameters there are the steps that can be run within DesignXplorer:    

Design of Experiments Response surface Optimization Six Sigma Analysis

Design of Experiments Design of experiments is the foundation that everything within DesignXplorer is built on. What this technique is about is to determine how many and for what input values the analysis shall be run. There are various techniques for this but the same goal for all is to get as good response surface as possible with as few input combinations as possible. So basically this step defines is how many analysis that will be run. Each combination that ANSYS solves for is referred to as a Design Points.

Response Surface When the Design of Experiments is run the next step is to create a response surface based on these results. A response surface will be created for each output parameter. The response surface is basically created via curve fit through the Design Points. From this response surface you can then investigate output results for input variable combinations that hasn´t been solved for.

Goal Driven Optimization To help you to select the combination of input variables that satisfies your goals best, you can run a Goal Driven Optimization. Here you have the possibility to give all you parameters different objective functions on which you also can give different importance. ANSYS will then give you a number of candidates that satisfies your goals in the best way.

Six Sigma Analysis The Six Sigma Analysis is a method that includes both a Design of Experiment and a Response Analysis. What resides is that you also have the possibility to set the input parameters as uncertainties parameters. This means that you can see how uncertainties in the input variables will affect the results for the output parameters.

How H to rrun an Optimiz O zation in n DesiggnXplorrer. In the t tutorial below it wiill be shownn how to sett up an optim mization an nalysis in DeesignXploreer. We will use two o input variiables, a thicckness and a radius, annd two outpuut variables, total masss and Princippal Stress. The T goaal is to find the best com mbination between b thickness and radius to minimize m thee mass of the structure and a to ensure e that the stress will w be below w a defined value.

Steep 1: Paraametric model m The first step is i to create a parametriic model. In n this case ANSYS A DessignModeler has been used, u but there aree a number oof different CAD systeems that alsoo can be useed.

Wiithin DesignnModeler th he parameteers are simply defined bby checkingg the box beetween the desired d parrameter. In this case wee have two parameters.. A thicknesss and a raddius.

Steep 2: Set u up the anaalysis to be b run. The next step is to transfeer the param metric modeel from DesiignModelerr to Mechannical and sett up the anaalysis. In this case we will w run a sttatic analysiis which is simply s drag gged and droopped onto the definedd geo ometry. Notte that theree now is a Parameter P Seet associated with the geometry g annd the Staticc Structural pro oject.

No ow you will have to deffine your materials, loaads, boundarry conditionns, mesh setttings etc. as a usual in Meechanical. W What residess from an orrdinary analysis is thatt you also will w have to define d you output o parrameters. Inn this case we w will use total t mass and a Maximuum Principaal Stress as output o parameters. Firrst define loads,

theen define ouutput parameeters.

Steep 3: Add d a Goal Driven D Opttimization n to you project. The next step is to add a Goal G Drivenn Optimizattion to the ccurrent projeect. To do thhis, simply drag it from m thee toolbox annd drop it on nto the curreent analysiss.

On ne could alsoo check the parameterss set to see that t all yourr parameterss are properrly defined.

Steep 4: Defiine Design n of Experriments. To define Dessign of Expeeriments, doouble click Design D of Experiments E s in the Projject Schemaatic. The gooal u an approppriate numbber of analy ysis to get ass accurate reesponse surrface as possible. (And of herre is to set up cou urse, the few wer parametter combinaations the beetter when it i comes to calculation time.) For each input parrameter youu will have to t define booundaries inn between w which they are a allowed to vary. In tthis case thee rad dius are alloowed to varyy between 2 and 3 mm. The thicknness is allow wed to vary between 8 and 10 mm m. The picture beelow shows how the booundaries arre defined for fo the radiu us together with w the seleected designn poiints to be ruun.

Steep 5: Run n the Desiggn of Expeeriments. This part of thhe analysis is i usually thhe most timee consuming part. Wheen pressing the button Update U Dessign of Experimentts ANSYS will w sequenttially run ann analysis foor each sugg gested desig gn point. Inn this case, here we have two input parameterss, ANSYS suggested s 100 design points to be ru un. If we haave more inpput wh parrameters wee need moree design poiints to be abble to createe an accuratee response surface s whiich will leadd to eveen more anaalyses to be run. If that is the case,, ANSYS luuckily has a solution to speed up thhis process. If you u have a com mputer or cluster c with several CPU U’s available and you combine c thaat with a paarallel licensse forr ANSYS yoou can run the t analysess in parallell instead. Thhis will drasstically speeed up the caalculation tim me com mpared to ddoing a sequ uential run. The figure bellow shows the t results of o the Desiggn of Experiiments afterr all design points p havee been run.

Steep 6: Calcculate Ressponse Surrface. Wh hen we havee a solution n for all desiign points we w can calcuulate a respoonse surfacee. As mentiooned beforee this is a curve fit through the results for each design point so s this is a quite q fast opperation.

Besides the caapability to plot p the respponse surfaace itself, there are heree a lot of cappabilities too plot the nnection bettween inputt and outputt variables. Among othher things we w have the possibility p t plot how to con sen nsitive outpuut results arre based on changes in the input vaariables.

Steep 7: Run n Optimizaation. No ow when wee have a resp ponse surfaace we can use u this to find fi an optim mal design. When you opened Op ptimization yyou have th he possibilitty to set diffferent objecctives for yo ou parameteers and also the possibillity to weight w thosse in regard to importannce. In this case we havve an objecttive for the Principal Sttress and thhe Geeometry Mass. For the stress s we’vee set a criterria where we w want to have h a structture that donn’t experiennce any y stresses abbove a targeet value of 180 1 MPa. This T is set too high imporrtance. For the mass we’ve set an objjective to minimize m thee mass with importancee low. The input i variabbles are left with no objjective sincee theere we are oonly interestted in that thhey are insidde the bounndaries that we defined from the sttart. Any vaalue in between b thoose boundarries are ok.

Wh hen we’ve ddefined objeectives it is just j to run the t optimizaation and raate the different candiddates that AN NSYS givess us. In this case ANSY YS gives us the followinng candidattes to choose between.

No ow we can sselect the caandidate thaat suites us thhe best. Bassed on the rates r (stars) given by ANSYS, A is seaams like Canndidate B iss the best soolution for us. u When seelected the appropriate a candidate itt could alwaays be a good pracctise to inseert this as a design d poinnt and run thhe analysis again a to maake sure thatt there is no o r solutionn and that taaken from th he responsee surface. subbstanially diifference beetween the real The result from m the final run r can be seen s in the figure f below w.


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