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Quasi-Static Fatigue

1. T Project Library I E Tutorials E Fatigue ni F Fracture T Importing me Parametric Import into Current Project Directory Material Library Import into Other Directory E Project Post Buckling Export to Project AIP FH nnt Delete Replace this figure 4 Navigate to the 42ksi directory under Fatigue node under Quasi Static node in the tree Note The FE Model will load in the Mesh view window Quasi Static Fatigue Section 4 2 3 Step by Step Tutorials Boundary Conditions 5 Click on the Boundary Conditions IB icon on the left of the Mesh Setup window to invoke the Boundary Conditions panel 6 To view the applied boundary conditions simultaneously highlight the items Boundary X Boundary Y and Boundary Z from the list by holding the Ctrl key as you click the left mouse button see Figure below Boundary Conditions Loading conditions 7 Click on the Force icon on the left of the Mesh Setup window to invoke the Force panel 8 Select Force X Figure below shows that the tensile forces are applied to the model at the right edge Caution The forces that are applied to the coupon are for fatigue loading is obtained from maximum stress loading Tensile load acting on the coupon Analysis Mode Parameters 9 Change the Analysis Mode to Quasi Static Fatigue 10 Be sure and verify that No is selected for Enable field under Spectrum Loading node A a Input ich A
2. Description Value Number of Nodes Elements Allowed to Damage 500 Number of Nodes Elements Allowed to Fracture Number of Iterations to Run 000 l Incremental Step for Material Non Linearity 10 Quasi Static Fatigue Parameters C Starting Cyde Stress Ratio ct T Use 5 4 Curves In Materials Analysis Settings 16 Double click on Advanced Settings node 17 Make sure that under the Post Damage Degradation section the Damage Force Locations and Damage Boundary Locations parameters are set to true Note Enabling the Damage Force Locations and Damage Boundary Locations to true will enable GENOA to remove those elements where either load or boundary conditions may be defined and where the stresses exceed the failure loads Viewing amp Editing the Materials 18 Expand DION node under Matrix node under Material node in the tree Quasi Static Fatigue Section 4 2 5 Step by Step Tutorials eB Matrix 1 5 9 DION Description None Temperature EEV Density RHO 4 430E 02 Ibm in 3 iE 4 65660E 05 lbf n 2 NU 4 200E 01 ST 1 108E 04 Ibf in 2 SC 3 500E 04 Ibf in 2 S5 1 300E 04 Ibfiine2 BQ Coefficient of Thermal Expansion 2 L ALFHA 4 980 05 perF a Stress Strain Curve A Stress Cycle Curve 19 Double click on Stress Strain Curve node to view the matrix nonlinear stress strain curve Stress Strain Curve L011300E 01 1 014500E 03 2 028500E 03 6 jp a 3 019200E 03 e 1
3. 5 019000E 03 _ 6 00 1500E 03 6 502100E 03 STRESS Ibf in 2 s 7 0 13200E 03 7 49 7000E 05 8 000 100E 03 8 490 500E 03 0 000 0 005 0 010 0 015 0 020 0 045 0 030 0 035 0 0 STRAIN inin Stress Strain Curve SMOOTH 20 Double click on Stress Cycle Curve node to view matrix degradation curve SN curve Note Stress ratio value of 0 1 is specified under Stress Cycle Curve node in the tree Quasi Static Fatigue Section 4 2 6 Step by Step Tutorials 21 Stress Ibf in stress Cycle Curve Results a 8 200000E 03 11 000 4 980000E 03 10 000 we Joy LOOOOGE 03 9 000 2 100000E 03 ae _ 1 B00000E 03 q 8 000 7 000 6 000 5 000 z 4 000 3 000 2 000 1 000 0 1 2345 10200 10000 1000 10000 100000 1000000 10000000 Cycle Stress Cycle Curve Results The S N data in the databank is entered from lower number of cycles to higher number of cycles In fatigue simulations materials performance is commonly characterized by a S N curve Wohler curve The S N curve is a graph of the magnitude of a cyclical stress S against the number of cycles to failure N It shows how many cycles are required to cause a fatigue failure for a given nominal stress The S N relationship is determined for a specified value of stress ratio R Omin Omax The S N curve is relevant for fatigue failure at high number of cycles N gt 105 cycles If the experimental S N c
4. er ie edralGonm cue JN 511C Longitudinal Compressive true Feb aS EE andeis as 6337 Normal Tensile false R11C Fiber Crush true 5235 Transverse Normal Shear false 011C Delaminations false 5135 Longitudinal Normal Shear false Matrix Failure Criteria RROT Relative Rotation false S227 Transverse Tensile true Maximum Strain Based Failure Criteria false 522C Transverse Compressive true Fiber Failure Criteria 533C Normal Compressi EPS 117 Longitudinal Tension Strain false 5 125 In irs EPS11C Longitudinal Compression Strain false Pine Sre Matrix Failure Criteria Delamination Failure Criteria EPS22T Transverse Tension Strain false 33T Normal Tensile true EPS22C Transverse Compression Strain false S235 Transverse Normal Shear true Delamination Failure Criteria 5135 Longitudinal Normal Shear true EPS33T Normal Tension Strain false RROT Relative Rotation true EPS533C Normal Compression Strain false Maximum Strain Based Failure Criteria false aan eee eS i z 5135 Long Out of plain Strain Se E EPS238 Trans Out of plain Shear Strain false a i tudinal hy Ki Int th F il C it Matrix Failure Criteria TSAI Tsai Wu false EPS227 Transverse Tension Strain false HILL Tsai Hill false EPS22C Transverse Compression Strain false HOFF Hoffman false Delamination Failure Criteria HASH Hashin false EPS33T Normal Tension Strain false ee F EPS33C Normal Compression Strain false z SiE l oleh R
5. Equiibri 224 261 _ 8 37500 0 00000 0 00000 0 00000 00000 0 00000 0 00000 2 73437 261 0 Equiibri 224 261 _ 8 37500 0 00000 0 00000 0 00000 0 00000 0 00000 0 00000 2 92968 261 0 Equibri 224 261 _ 8 37500 0 00000 0 00000 0 00000 0 00000 0 00000 0 00000 3 02734 261 o Equiibri 224 251 _ 8 37500 0 00000 0 00000 0 00000 0 00000 0 00000 0 00000 3 05175 261 0 Equiibri 261 8 37500 0 00000 0 00000 0 00000 0 00000 0 00000 0 00000 3 07617 261 4 Damage ta ho MO s in b Ga a ee Complete Results Log table The log indicates that the last equilibrium iteration before fracture corresponds to 305 cycles which is the fatigue life of the composite coupon for the stress ratio R 0 7 and the load amplitude 838 lbs nominal stress amplitude 42 ksi Results Mesh 33 Double click on Mesh node in the tree under Analysis Results node Note You will see more nodes under Mesh node in the tree as shown below Quasi Static Fatigue Section 4 2 10 Step by Step Tutorials oe Mesh AG Stress Strain ee Ply Stress E Ply Strain Node Damage 34 Double click on Damage node under Mesh node in the tree 35 Drag the slider to iteration 5 or enter 5 in the iteration text box 36 Select Cycles in the drop down list in the player next to iteration text box as shown in the following Figure p I
6. Quasi Static Fatigue Section 4 2 1 Step by Step Tutorials 4 2 Quasi Static Fatigue Case Description Example Location Model Description Material Description Objective of Analysis ASTM Number Control Type Analysis Type Solution Input Requirements FEA Solver Output from Analysis Summary of Results Composite coupon subject to tensile cyclic loading Tutorials gt Fatigue gt Quasi Static Fatigue Nodes 261 Elements 224 Length 1 0 1 013091 Width 0 1964 0 196248 and Thickness 0 10198 Fiber Matrix FVR 55 with nonlinear matrix stress strain response Layup 0 90 0 90 0 90 0 woven Predict the fatigue life of the coupon Load Control Quasi Static Fatigue Fatigue 10 See Section 5 of User Manual GENOA data bank including experimental stress strain and S N curves GENOA model files MHOST Use the keyword SOLVER as described in Section 5 of User Manual to invoke other FEA solver options such as NASTRAN ANSYS and ABAQUS Fatigue life number of cycles to failure for three constant load stress levels ply stresses and strains failure modes at various amounts of cycles a At the load level of 30 of the ultimate load the fatigue life is 12 500 cycles b At the load level of 50 of the ultimate load the fatigue life is 3 900 cycles c At the load level of 70 of the ultimate load the fatigue life is 373 5 cycles Quasi Static Fatigue Secti
7. SE IDA s EP5125 In plain Shear Strain false 7 oe Sa Haniel false EPS13S Long Out of plain Shear Strain false CRMP Crimping for Honeycomb false EPS235 Trans Out of plain Shear Strain false DIMP Dimpling for Honeycomb false Interactive Failure Criteria Miscellaneous MDE Modified Distortion Energy true CFC Customized Failure Criteria true TSAI Tsai Wt false UDFC User Defined Failure false 28 Select Save under Project menu or press Ctrl and S on the keyboard Progressive Failure Analysis 29 Right click on Analysis node and select Progressive Failure Analysis option in the Add popup menu VJ Progressive Failure Analysis Filament Winding Analysis Parametric Carpet Plot se A amp B Basis Allowables Simulation 30 Right click on Progressive Failure Analysis node and select Run Analysis Progressive Failure Analysis Results Note After the analysis is completed the program will automatically switch to the Results Log screen But if you wish to load the current results during the analysis then you may choose the Quasi Static Fatigue Section 4 2 9 Step by Step Tutorials Reload Results menu item under the popup menu for the Analysis Results node You may reload the results at any time if you believe that the results are not current or updated correctly a ve Results Log Reload Results p E Mesh y sais El Energy Graph AF Element Graph When there are results to be loaded there will be additi
8. aterials 4 node in the tree You will see the vectors defined for up and down going fibers see Figure below Note the vectors are used to define the out of plane orientation of fibers along the x axis of the ply Please consult Braid and Woven step by step exercise under Static directory for more explanation Braid Entry Setup Fiber Fiber Volume Ratio X Angle Vector Y Angle Vector zZ Angle Vector DOQOO0E 0 1 QOOO00E 00 2 660 250E 01 Similarly double click on Braid_1 node under Braid 2 node in the tree Note the vectors are used to define the out of plane orientation of fibers along the y axis of the ply see Figure below Braid Entry Setup Fiber Fiber Volume Ratio X Angle Vector Y Angle Vector Z Angle Vector EGKG 5 OO0000E 0 1 0 000000E 00 5 OOO000E 0 1 8 060 250E 01 5 QOOOOOE 0 1 0 Q00000E 00 5 000000E 01 8 660 250E 01 Click on the Boundary Conditions icon to invoke the Boundary Conditions panel Failure Criteria 26 27 Under the Failure node double click on FailCrit_1 node to review the damage and failure criteria assigned to the laminates Click on Composite Default button underneath the Damage Criteria and Critical Failure Criteria tabs Note For this exercise will not modify the Failure Criteria Quasi Static Fatigue Section 4 2 8 Step by Step Tutorials Name Value Maximum Stress Based Failure Criteria true Fiber Failure Criteria Critical Fracture Criteria
9. e composite coupon Repeat above steps to predict the fatigue life of the coupon for the load amplitudes 600 Ibs nominal stress amplitude 30 ksi and 345 lbs nominal stress amplitude 17 ksi D ul Oo O O O Stress ksi U9 O Testi N O m Test2 GENOA 100 1 000 10 000 100 000 Cycles to Failure Nf Fatigue life of the woven composite coupon subject to cyclic tensile loading Quasi Static Fatigue Section 4 2 12 Step by Step Tutorials You have finished the example demonstrating how to use GENOA to predict the fatigue life of a composite structure
10. nalysis Mode Parameters E Advanced Settings Ea Spectrum Loading Enable 11 Double click on Analysis Mode Parameters node under Analysis Mode node in the tree 12 Enter 10 for Incremental Step for Material Non Linearity Note This parameter increases the accuracy The higher the value the lower the load increment becomes however it is time consuming and should be used when nonlinearity of the material is to be considered In case of linear elastic assumption set this parameter to 1 13 Set Starting Cycle value to 10000 Quasi Static Fatigue Section 4 2 4 Step by Step Tutorials Note If you expect your model to initiate damage at much higher cycles then you can enter higher starting cycle value The analysis will attempt to skip the analysis for specified cycles unless there is damage in the FE model If you are not sure of the starting cycle number then you are advised to start with Starting Cycle value of 1 The analysis will take longer to run in this condition 14 Enter 0 1 for Stress Ratio Note If the material databank contains multiple S N curves for different Stress Ratios the user can specify which S N to be used for this analysis If the Stress Ratio value is different from that available in the databank and is in between the range in the databank then GENOA will interpolate between the two S N curves We have only 0 1 available in the databank 15 Switch Use S N Curves in Materials to true see Figure below
11. on 4 2 2 Step by Step Tutorials Introduction This tutorial demonstrates how to use GENOA PFA to estimate the fatigue life of a composite coupon Subject to cyclic tension For details on the technical approach and general features of the code please refer to the GENOA PFA Quick Reference and Theoretical Manuals In the example herein a 0 90 0 90 0 90 0 cross ply coupon which is made of the 96 0z 3TEX 3Weave E glass Dion 9800 composite system is used The coupon is 1 0 inch long by 0 1964 inch wide by 0 102 inch thick The analysis is based on the fiber matrix properties of the composite system These properties together with the composite matrix nonlinear stress strain curve and the S N degradation curves for the fibers and matrix were obtained from experiments The fatigue life is predicted for the three load stress levels with the amplitudes corresponding to approximately 30 50 and 75 percents of the ultimate static load which can be determined by running static GENOA PFA analysis The simulated results are compared with experimental data Launching GENOA 1 Start GENOA by executing it from the desktop or typing genoa in the command prompt Importing GENOA Model File The geometry has already been created in GENOA format as a dat input file 2 Make sure the Unit System in the upper right corner is set to Inch Second Pound Right click on Quasi Static node under the Fatigue node and select Open Project see Figure below
12. onal nodes under the Analysis Results node as shown below 2 Analysis Results p JE Results Log E Mesh a Ee Energy Graph wis e Element Graph Results Log 31 Double click on Results Log node to view the iteration log if not already there after the simulation is complete Note The Results Log table provides information about the amplitude of the applied cyclic load and the number of damaged and fractured nodes corresponding to the number of fatigue cycles The fatigue cycles corresponding to stable equilibrium are highlighted in green 32 Click on View All Iterations button The log will show all the iteration rows default Iteration Elements Modes ForceX Force Force Mome Mome Mome Pressure Cyde Damag Fractu Status 224 261 8 37900 0 00000 0 00000 0 00000 0 00000 0 00000 0 00000 1 95312 261 0 ee 224 261 3750 0000 O000 0 0000 0 0000 0000 0000 88322 261 0 Damagen 324 21 8 37500 o 00000 0 00000 0 00000 0 00000 0 00000 0 00000 1 95312 261 0 Equal 224 251 _ 8 37500 0 00000 0 00000 0 00000 0 00000 0 00000 9 00000 3 90625 261 0 Equiibri 224 261 6 3750 0 0000 0 000 0 0000 0 0000 2 00000 0 00000 7 8120 261 0 Ear Ca ast on 00 00000 0 00000 0 00000 0 00000 1 56250 261 o Equllbr 224 251 _ 8 37500 0 00000 0 00000 00000 0 00000 0 00000 0 00000 2 34375 261 O
13. teration 5 GE Ti 7812500601 EHHE All Iterations Note You will see the following damage modes Node Damage Fiber Damage Only Matrix Damage Onhy Delamination Damage Only 100 0 5117 Longitudinal Tensile 100 0 511C Longitudinal Compressive 100 0 F11C Fiber Micro Buckling 100 0 522T Transverse Tensile 100 0 INTR Interactive Failure Criteria Fractured Nodes T Show All Damage List Damage results mesh at Iteration 5 78 cycles Note The element switches to red color even if one ply out of 14 plies is damaged 37 Advance the iterations further until you reach the last iteration Quasi Static Fatigue Section 4 2 11 Step by Step Tutorials Node Damage T Fiber Damage Only Matrix Damage Only Delamination Damage Only 100 0 5117 Longitudinal Tensile 100 0 511C Longitudinal Compressive 100 0 F11C Fiber Micro Buckling 100 0 5221 Transverse Tensile 100 0 INTR Interactive Failure Criteria Fractured Nodes E Show All Damage List Damage results mesh at Iteration 13 308 cycles Note The damage panel shows Longitudinal Tension failure that corresponds to fiber failure for O degree plies in the coupon The Longitudinal Compression appears because the fibers in the 90 degree plies are assumed to have buckled during the analysis after matrix failure Note Figures above show that after 308 cycles of cyclic tensile loading crack propagation initiation takes place in th
14. urve is not available the bilinear degradation curve can be used instead In this case the value of the Use S N Curves In Databank parameter will be set to false and the user will be required to input two pairs of coefficients a and b for the expression S a blogN 5 g 0 Repeat the above steps for EGKG glass fiber material Note usually carbon graphite ceramic aramid fibers show linear behavior therefore the SS and S N curve tabs are left empty You can create a SN curve if you see degradation in S N curve for 0 degree ply data subjected to tension tension axial loading The S N curve in this case will represent the reduction in fiber tensile strength due to breakage in the fiber tows Laminate Editor 22 Right click on Laminate_1 node under Laminate node in the tree and select Edit in the popup menu Note For this exercise will not modify the laminate Quasi Static Fatigue Section 4 2 7 23 24 20 Step by Step Tutorials espera an maca an Angle at Void Volume Jaana Degrees Fraction Fraction ae EGKG NONE 7 c00000E 01 1 204600E 02 Se 5 500000E 01 Laminate Editor Note The laminate Editor shows that the coupon lay up consists of 14 composite EGKGDION different thickness plies with E glass fibers arranged in the cross ply pattern Also braid cards are defined which is explained in detail in another tutorial example Double click on Braid node under Braid 2 node under M

Quasi-Static Fatigue

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