# Dynamic Analysis Contact Parameter Problem in UDEC **URL:** \ **Category:** UDEC\ **Created:** [April 30, 2024, 6:21pm UTC](https://forum.itascainternational.com/t/dynamic-analysis-contact-parameter-problem-in-udec/1432 "2024-04-30T18:21:46Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![SamVarun10](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@SamVarun10](https://forum.itascainternational.com/u/SamVarun10)\ **Post date:** [April 30, 2024, 6:21pm UTC](https://forum.itascainternational.com/t/dynamic-analysis-contact-parameter-problem-in-udec/1432/1 "2024-04-30T18:21:46Z")
Hello everyone, I am performing a dynamic analysis test on SHPB Test Sample. I have attached a sample code for the same: model new block tolerance corner-round-length 3.4E-7 block tolerance minimum-edge-length 6.8E-4 block contact tolerance overlap 0.010 block create polygon 0 0 0 0.050 5.016 0.050 5.016 0 block cut crack 2.975 0 2.975 0.050 block cut crack 3.009 0 3.009 0.050 block hide block seek id-list 1,2 block zone gen quad 0.010 block zone cmodel assign elastic density 8000 bulk 166.7e9 shear 76.92e9 range pos-x 0 2.975 block zone cmodel assign elastic density 8000 bulk 166.7e9 shear 76.92e9 range pos-x 3.009 5.016 block seek block hide id-list 1,2 block cut crack 2.975 0.008 3.009 0.008 block cut crack 2.975 0.042 3.009 0.042 block delete id-list 3,5 block cut voronoi edge-maximum 0.004 iterations 100 round 1E-4 block zone gen edge 0.004 block hide id-list 1,2 block zone cmodel assign elastic density 1900 bulk 5.397E9 shear 2.636E9 ;Model Material from Journal block seek ;Contact Properties block contact cmodel assign residual st-s 2.5e13 st-n 5E13 friction 55 … cohesion 80E6 tension 350e6 … friction-residual 55 cohesion-residual 80E6 tension-residual 350e6 fish define wave if block.mechanical.time.total \> 1.0 / freq wave = 0.0 else wave = 1_math.sin(1.0_math.pi_freq_block.mechanical.time.total) endif end fish set @freq=5000 @wave block gridpoint apply bulk 166.7E9 shear 76.92E9 density 8000 block gridpoint apply visc-x range pos-x 5.016 tolerance 0.00001 block gridpoint apply visc-x range pos-x 0 tolerance 0.00001 block gridpoint apply visc-y range pos-x 5.016 tolerance 0.00001 block gridpoint apply visc-y range pos-x 0 tolerance 0.00001 block edge apply stress 382E6 0.0 0.0 history @wave range pos-x -0.001 0.001 pos-y 0.000 0.050 block mechanical history time-total block mechanical damping 0.0 0.0 block zone history stress-xx 1.4875 0.050 block zone history stress-xx 4.0125 0.050 block cycle time 2E-3 Here the contact microparameter - Contact tensile strength for a value of 350E6 gives desirable result i.e. Incident+Reflected Stress Pulse should be equal to Reflected Pulse But isn’t this value not realistic? ![image](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/2X/3/3e6b3646b17ccdf2f6ab8f694c8a788a140f6e44.png) Top figure is the stress pulse for incident bar Bottom figure is the stress pulse for transmission bar Can somebody please convey what is the issue here? What should be done so that this contact tensile strength value becomes realistic. General UCS value of sample is 60 MPa and Tensile Strength is 6MPa ---
**Author:** ![udecsupport](https://avatars.discourse-cdn.com/v4/letter/u/e9c0ed/32.png) [@udecsupport](https://forum.itascainternational.com/u/udecsupport)\ **Post date:** [May 2, 2024, 3:00pm UTC](https://forum.itascainternational.com/t/dynamic-analysis-contact-parameter-problem-in-udec/1432/2 "2024-05-02T15:00:56Z")
The strength of the joint will affect the amount of energy that is transmitted, reflected or absorbed. There is an example of this for a shear wave in the UDEC 7.0 manual (Special features volume page 4-60). For a pressure pulse, I assume the tensile strength of the joint would be critical.