Two UserRoutines for. Online Stress and Damage Calculation


 Harvey Francis
 3 months ago
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1 SIMPACK User Meeting 2011, May 19 th, Salzburg, Austria Two UserRoutines for Online Stress and Damage Calculation Christoph Tobias and Peter Eberhard 1/26
2 Outline 1. motivation and example model part I: 2. online stress calculation background in an EMBS implementation and usage verification 3. online damage calculation in an EMBS some notes part II: 4. application examples structural optimization pseudo damage calculations 5. conclusions 2/26
3 Motivation and example node 609 3/26
4 displacement stress u σ R t Φ R q t, fem R, t H D u u R,t Theoretical background FEM projection q σ fem t V q red t R t H D Φ R V q t, u red MOR stress modes Φ σ,red (R) equation of motion y M q II red k h EMBS stress calculation σ(r,t) during EMBSruntime 4/26
5 process chain Implementation and usage FEM FE model system matrices MOR order reduction SID data EMBS equation of motion V q red (t) evaluation stress modes Φ σ,red (R) processing SID data (stress) user routine σ(r,t) 5/26
6 SID data for nodal stresses Implementation and usage class taylor class node object sigma... class node contains an additional object sigma, which is of class taylor 6/26
7 SIMPACK preprocessorgui Implementation and usage SID file with nodal stress modes Φ σ,red (R) body holding elastic coordinates q red (t) 7/26
8 SIMPACK postprocessorgui Implementation and usage 8/26
9 Verification node 609 reference solution calculated by SIMPACK/Loads (and NASTRAN) 9/26
10 1. usage of advanced model reduction techniques (e.g. Krylovsubspace techniques) ensure small errors and/or error bounds for the calculated stress Some notes 2. online stress calculation is necessary for some control problems, e.g. deformable lenses 3. online stress calculation is necessary for online damage calculation [Zeiss08] 10/26
11 rainflow counting Theoretical background 4 S tt S to move through turning points in the load signal little by little with a socalled 4pointstack σ ε 1 S matrix of RFC Sfrom S fill / move 4pointstack residue of rainflow counting are points 2 and 3 inside the range spanned by 1 and 4? yes identification of alternation from 2 to 3 as closed hysteresis loop fill matrix of rainflow cycles (RFC) delete points 2 and 3 signal no from load t 11/26
12 damage accumulation Theoretical background l S to matrix of RFC S from S S l,to S l S l,from t further calculations:  mean stress influence  yielding? ... D l log(s) N l 1 N l 1 N SN Kurve A log(n) S S l A b damage accumulation D i D i damage value 12/26
13 Implementation and usage process chain SID data equation of motion EMBS q red (t) SID data (stress) user routine σ(r,t) user routine D(R) parameter file 13/26
14 SIMPACK preprocessorgui Implementation and usage load channel σ(r,t) parameter file 14/26
15 Implementation and usage SIMPACK postprocessorgui 15/26
16 Verification damage wafo damage simpack reference solution calculated by MATLAB/Wafo 16/26
17 Some notes 1. by using an EMBSadapted 4pointalgorithm, the storage of load data (e.g. forces, elastic coordinates, stresses, ) is not necessary 2. online damage calculation provides a scalar performance criterion for load channels in terms of durability 3. regarding calculation times, the online damage calculation is (usually) not very costly 17/26
18 process chain Structural optimization geometry modifications FEM FE model evaluation stress modes system matrices V Φ σ,red (R) MOR order reduction processing OPT (by using TOSCA) SID data SID data (stress) EMBS equation of motion q red (t) user routines D(R) 18/26
19 Structural optimization 19/26
20 Structural optimization iteration 000 iteration 001 iteration 002 iteration 003 iteration 004 iteration 005 iteration 006 iteration 007 iteration 008 iteration 009 iteration 010 iteration... 20/26
21 Idea: apply rainflow counting and damage accumulation directly on femindependent load channels (e.g. applied forces) Pseudo damage calculations 1. do rainflow counting for load channels 2. compare load hysteresis loops with a virtual SNcurve 3. do damage accumulation 4. a scalar performance criterion for a femindependent load channel in terms of durability results 21/26
22 possible questions: how many modes are necessary? how do the load channels interact? does an extrapolation make sense? load cha. 1 load cha. 2 Pseudo damage calculations load cha. 5 load cha. 4 load cha. 3 22/26
23 possible questions: how many modes are necessary? how do the load channels interact? does an extrapolation make sense? Pseudo damage calculations l * t P l t where and rows of P: n l * nl P R n * n l l p i : n l j 1 p 2 ij 1 23/26
24 possible questions: how many modes are necessary? how do the load channels interact? does an extrapolation make sense? Pseudo damage calculations 24/26
25 Conclusions 1. implementation of two SIMPACK userroutines for online stress and damage calculation 2. results verified by reference calculations 3. the proposed method has some advantages, e.g. small errors in stress small result files a scalar performance criterion for loads is directly outputted from the EMBS 4. some applications structural optimization including EMBS as main tool evaluation of nonfemdependent load results with pseudo damage calculations thank you very much! 25/26
26 References [TobiasEberhard11] Tobias, C.; Eberhard, P.: Stress Recovery with Krylov Subspaces in Reduced Elastic Multibody Systems. Multibody System Dynamics, 25(4), , [Wafo05] The Wafo Group: Wafo A Matlab Toolbox for Analysis of Random Waves and Loads, Version Lund: University, Centre for Mathematical Sciences and Mathematical Statistics, Online available: [TobiasFehrEberhard10] Tobias, C.; Fehr, J.; Eberhard, P.: Durabilitybased Structural Optimization with Reduced Elastic Multibody Systems. In Proceedings of the 2nd International Conference on Engineering Optimization, Lisbon, Portugal, September 69, [FehrTobiasEberhard10] Fehr, J.; Tobias, C.; Eberhard, P.: Automated and Error Controlled Model Reduction for Durabilitybased Structural Optimization of Mechanical Systems. In Proceedings of the 5th Asian Conference on Multibody Dynamics, Kyoto, Japan, August 2326, [MatMorembs10] [Dietz99] Dietz, S.: Vibration and Fatigue analysis of Vehicle Systems using Component Modes. Fortschritt Berichte VDI, Reihe 12, Nr VDIVerlag, Düsseldorf, [Simpack10] Simpack GmbH: Simpack Reference Guide, Simpack Version Gilching, [Wallrapp94] Wallrapp, O.: Standardization of flexible body modeling in multibody system codes. Part I: Definition of Standard Input Data. Mech. Struct. Mach 22(3), , [Zeiss08] Carl Zeiss GmbH: Optische Einrichtung mit einem deformierbaren optischen Element (in German). Prioritätsbescheinigung DE Deutsches Patentamt, München, /26