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My LS Prepost keeps on crashing when I hit on apply after setting  ua a boundary condition, is there any other way to do it ao maybe I am making a mistake, please help.

<p>I am working on implementing a user defined hyperelastic material which needs a push forward operation. I saw the push_forward_2s(), I'm using the scalar version for now, in Manual 1 Appendix A. However, it does not describe in sufficient detail for me to understand what this function does. </p><p>Detailed questions:</p>What stress is this function expecting as input? First Piola-Kirchhoff? Second Piola-Kirchoff? Something else? Does it account for the change in volume from the reference to the current configuration with 1/detF or do I need to handle that outside of this subroutine? What stress is the ouptut from this function? I am assuming Cauchy but I would like confirmation.<p>I have implemented my own push forward code in the user-defined material to go from the second PK stress to Cauchy stress using the well known equation sig = 1/detF * F * 2PK * F^T. However, the results do not match. It is also possible I have made a mistake in my code but the push forward is relatively straight-forward. </p><p>Thanks in advance.</p>

<p>Hello there,</p><p class="PDq2pG_selectionAnchorContainer" data-start="113" data-end="180">I have a question regarding the outputs when using LS-DYNA/MPP. I would like to obtain the displacement of the rigid body, so I requested this output in the input file. In the output, I loaded the binout0000 file and selected rbdout> rigid_body> global_dz from the main branches in the binout file (the result is shown below).</p><p></p><p data-start="444" data-end="582">However, I noticed that there is another rigid body displacement output available under matsum> SPHnode> z_rbdisplacement (shown below).</p><p></p><p data-start="587" data-end="758">Since both outputs appear to represent rigid body displacement but give different values, could you please let me know which one is the correct displacement output to use?</p><p data-start="763" data-end="773">Thank you,</p>

<p><p>I am working on implementing a user defined material model that requires access to the displacement field directly to include some atypical components like the hessian of the displacement field. </p><p>How can I pass the element nodal displacement field into the user defined material subroutine? I looked through all the documentation and a lot of the code in the object file version of LS-DYNA. However, many of the variables are not defined, e.g. in commented code sections, and the naming convention doesn't not provide a sufficient description to make an educated guess. </p><p>I know it seems a little odd but the deformation gradient is right there which is one step removed from the data I need. I would think the displacements are nearby I just don't know where to find them.</p><p>Thanks in advance for any assistance you can offer. </p></p><p> </p><p><p> Edit 7/28/2026 12:15p </p></p><p><p> After some further digging it seems like it might be possible to define my own solid element type which has a call to the usrmat() subroutine. The user defined element subroutine has access to the nodal displacement field which I could then pass to the main user defined material subroutine usrmat() and on into the individual umatxx() subroutines where the material behavior is actually defined. Seems like a long and tedious work around. </p></p><p><p> I am also wondering if the nodal displacements are more directly accessible to the user defined material subroutine through a common block data structure. That would be very straightforward and simple to use. More digging on this required. I was hoping that's how the displacement field was referenced in the user defined element subroutine and I could just copy it but alas tis not the case. </p></p><p><p> Thinking about it more here I am going to assume that the usrmat() function called from the standard solid element subroutine does not pass the nodal displacements to the usrmat() subroutine, and I would need access to that code to make that modification. Which makes me think that the user defined element is the way to go. However, if I update the subroutine call format are other parts of the code like the standard solid element function call going complain; I'm going to try this first because it is the simplest solution. If that doesn't work then, I think one could define a custom usrmat_custom() which would be called by the user defined element and could be passed the displacement field. </p> </p><p><p> Here's to chasing little white rabbits and jabberwockies. </p></p>

Hello everyone. I'm modeling a huge beam mesh model.It's a 100x50 meter mesh made of 6mm wire, using a beam model with a 100x100 mm mesh size. I created a Workbench-Share  to combine all the beams into one piece and connect all the nodes. This resulted in a gigantic beam mesh model.When I open Workbenches Dyna, it takes a very long time to load. I've waited three days, but it still hasn't loaded. How do I load it? Are there any ways to speed it up? Thanks.

<p>I just downloaded 2026R1 ansys student license and the lsdyna split input file feature seems to have stopped working?  Does anyone else also see this?</p><p>literally just did this on 2025R1 and it works. </p><p></p>

<div>Hello,</div><div> </div><div>I am simulating twist extrusion (helical/ECAP-type die) of Ti powder using SPG</div><div>(ELFORM 47) with LS-DYNA R16.1.1 MPP double precision, 12 cores.</div><div> </div><div>MODEL</div><div>- Billet: SPG solid, MAT_CSCM (cap model), relative density 0.70,</div><div>  rate effects disabled, softening disabled.</div><div>- Die: rigid shells; contact via *DEFINE_SPG_TO_SURFACE_COUPLING (SPGP=powder,</div><div>  SURF=die segment set).</div><div>- Helical section: cross-section rotates ~64 deg over 18 mm of channel length.</div><div>- Loading (both tried): (a) pressure on null-shell skins on the billet end faces,</div><div>  (b) prescribed velocity through a soft elastic spacer merged to the SPG nodes.</div><div>- Back pressure 200 MPa on the exit face in both cases.</div><div> </div><div>PROBLEM</div><div>The run is perfectly healthy for a long time: time step stays constant</div><div>(~1.2e-7 s), KE/IE ~ 0, internal energy grows smoothly, no erosion at all.</div><div>Then, within less than 1 ms, an entire transverse layer of background elements</div><div>inverts (negative volume), and the job dies with either</div><div> </div><div>    "gt ispgnumextn"</div><div> </div><div>or a hard crash:</div><div> </div><div>    forrtl: severe (157): Program Exception - access violation</div><div>    SPGBSORT (spgbsort.f) / SPGMGBUCKET_SMP / SPGFINOD3 / SPGFINOD / SPGSMOOTH</div><div> </div><div>Checking the deleted nodes, the first failures are all from one original element</div><div>row, located at the EXIT of the helical section (where the cross-section stops</div><div>rotating and the material "unwinds"), and they are spread across the whole</div><div>cross-section (r = 2...11 mm, channel radius 14.7 mm) - i.e. in the core, NOT at</div><div>the die wall.</div><div> </div><div>SETTINGS ALREADY TRIED (none of them removes the failure, they only delay it)</div><div>- DX = DY = DZ: 1.5 / 1.6 / 1.8 / 2.0</div><div>- KERNEL = 1 (Eulerian); ISPLINE = 0</div><div>- SMSTEP: 15 / 5 / 3</div><div>- MSC = 1 together with ITB = 3</div><div>- IDAM = 1, STRETCH = 1e10 and 6</div><div>- PDAMP = -0.005 / -0.01, BOXID active</div><div>- Coupling SFP = 0.5 / 0.7, THK = 0.25 / 0.5, friction = 0 / 0.05 / 0.1</div><div>- CONTROL_TIMESTEP: TSSFAC 0.5, DT2MS = 0, ERODE = 1; DTMIN = 0.1</div><div>- Mesh size of the billet: 2.8 mm / 1.24 mm / 1.0 mm</div><div>- Drive speed 100 mm/s and 50 mm/s</div><div> </div><div>QUESTIONS</div><div>1. Are there recommended SPG settings for large TORSIONAL/shear deformation of</div><div>   this kind (background mesh must follow a ~64 deg rotation)? Any guidance on</div><div>   DX and SMSTEP for this class of problem?</div><div>2. What controls the internal array dimension behind "gt ispgnumextn", and can</div><div>   it be increased (keyword/parameter/memory)?</div><div>3. For a helical rigid wall, is *DEFINE_SPG_TO_SURFACE_COUPLING the recommended</div><div>   approach, or is *CONTACT_AUTOMATIC_NODES_TO_SURFACE preferred?</div><div>4. Is *CONTROL_SPG required or recommended here? I have not used it so far.</div><div>5. For powder consolidation I do NOT want material separation. What are the</div><div>   recommended IDAM / STRETCH / FS settings for a "no bond failure" setup?</div><div> </div><div>Any advice would be greatly appreciated.</div><div></div><div></div><div></div>

<p>Hello,</p><p>How should the load segment and segment set be defined for 2D plane stress geometry modeled using Q8 elements elform = 23? Each edge has 3 nodes. </p><p>Thanks.</p>

<h3 class="PDq2pG_selectionAnchorContainer" data-section-id="ww3lfh" data-start="227" data-end="241">Forum post</h3><p data-start="243" data-end="258">Hello everyone,</p><p data-start="260" data-end="560">I am developing an LS-DYNA model for <strong data-start="297" data-end="372">shearing a rectangular Cu-ETP copper wire with two rigid cutting blades. The purpose of the model is to simulate separation of the copper wire by shear deformation, similar to a shearing or blanking process. It is not a machining or chip-formation simulation.</p><p data-start="562" data-end="864">The copper wire is modeled with solid elements and a Johnson–Cook material model. Material failure is currently defined using Johnson–Cook damage and/or <code data-start="715" data-end="733">*MAT_ADD_EROSION. The blades are modeled as rigid bodies, and <code data-start="779" data-end="816">*CONTACT_ERODING_SURFACE_TO_SURFACE is used between the blades and the copper wire.</p><p data-start="866" data-end="1160">The calculation runs successfully, but I do not know whether the predicted separation is physically reasonable or whether it is mainly caused by numerical settings. I would therefore like to understand how the keyword parameters should be selected and improved based on post-processing results.</p><p data-start="1162" data-end="1270">My main problem is that I cannot find clear recommendations for the reasonable ranges of parameters such as:</p><ul data-start="1272" data-end="1688"><li data-section-id="9tub6x" data-start="1272" data-end="1323">failure strain or <code data-start="1292" data-end="1300">EFFEPS in <code data-start="1304" data-end="1322">*MAT_ADD_EROSION;<li data-section-id="q6a4nz" data-start="1324" data-end="1373">Johnson–Cook damage parameters <span class="katex"><span class="katex-mathml">D1D_1</span><span class="mord"><span class="mord mathnormal">D</span><span class="vlist-r"><span class="mord mtight">1</span><span class="vlist-s">​</span></span></span></span>–<span class="katex"><span class="katex-mathml">D5D_5</span><span class="mord"><span class="mord mathnormal">D</span><span class="vlist-r"><span class="mord mtight">5</span><span class="vlist-s">​</span></span></span></span>;<li data-section-id="b5o2ju" data-start="1374" data-end="1429">contact penalty stiffness scaling, especially <code data-start="1422" data-end="1428">SFSA;<li data-section-id="py57fx" data-start="1430" data-end="1487">static and dynamic friction coefficients <code data-start="1473" data-end="1477">FS and <code data-start="1482" data-end="1486">FD;<li data-section-id="1xxp1r8" data-start="1488" data-end="1519">hourglass control parameters;<li data-section-id="1a4nobf" data-start="1520" data-end="1562">element size in the expected shear zone;<li data-section-id="1bl6tf7" data-start="1563" data-end="1585">cutting-edge radius;<li data-section-id="1zs3i9" data-start="1586" data-end="1621">clearance between the two blades;<li data-section-id="1b0xmru" data-start="1622" data-end="1639">blade velocity;<li data-section-id="x6mtrn" data-start="1640" data-end="1688">workpiece constraints and clamping conditions.<p data-start="1690" data-end="1959">When I change these parameters, I obtain very different results. In some cases, the copper wire does not separate. In other cases, elements are deleted too early, the blades penetrate the copper wire, or the fracture surface appears to be controlled mainly by the mesh.</p><p data-start="1961" data-end="2063">I am therefore unsure which results represent real shearing and which results are numerical artifacts.</p><p data-start="2065" data-end="2131">At present, I am evaluating the following post-processing results:</p><ul data-start="2133" data-end="2432"><li data-section-id="1kajx3x" data-start="2133" data-end="2176">blade force versus time and displacement;<li data-section-id="59yzj4" data-start="2177" data-end="2246">internal energy, kinetic energy, hourglass energy and total energy;<li data-section-id="13bdu2e" data-start="2247" data-end="2269">contact penetration;<li data-section-id="1511y5" data-start="2270" data-end="2297">effective plastic strain;<li data-section-id="1avm5im" data-start="2298" data-end="2317">effective stress;<li data-section-id="1b5dn1b" data-start="2318" data-end="2357">damage variable and element deletion;<li data-section-id="oqswxv" data-start="2358" data-end="2390">development of the shear zone;<li data-section-id="3cq22b" data-start="2391" data-end="2432">final fracture and separation geometry.<p data-start="2434" data-end="2492">I would be grateful for advice on the following questions:</p><li data-section-id="1gsrlxe" data-start="2494" data-end="2588"><strong data-start="2497" data-end="2588">Which post-processing results are essential for validating a metal shearing simulation?<li data-section-id="1qdla3i" data-start="2590" data-end="2709"><strong data-start="2593" data-end="2709">What should physically reasonable force–displacement and energy curves look like during shearing and separation?<li data-section-id="pe9qr9" data-start="2711" data-end="2785"><strong data-start="2714" data-end="2785">How can excessive contact penetration be identified quantitatively?<li data-section-id="4gm6x2" data-start="2787" data-end="2902"><strong data-start="2790" data-end="2902">How can I distinguish physical shear failure from artificial separation caused by premature element erosion?<li data-section-id="1620pok" data-start="2904" data-end="3102"><strong data-start="2907" data-end="2962">How should I determine a reasonable <code data-start="2945" data-end="2953">EFFEPS value?<br data-start="2962" data-end="2965">Should it be obtained from tensile-test data, shear-test data, fracture tests or calibration against an experimental shearing process?<li data-section-id="9f5rgc" data-start="3104" data-end="3256"><strong data-start="3107" data-end="3256">If Johnson–Cook damage is used, should <code data-start="3148" data-end="3156">EFFEPS in <code data-start="3160" data-end="3178">*MAT_ADD_EROSION still be active, or should it only be used as a numerical backup criterion?<li data-section-id="12tl3u7" data-start="3258" data-end="3521"><strong data-start="3261" data-end="3349">Which parameters are physical process parameters and which are numerical parameters?<br data-start="3349" data-end="3352">For example, blade clearance, edge radius and friction are physical parameters, whereas contact penalty scaling and hourglass control are mainly numerical parameters.<li data-section-id="1xhs70i" data-start="3523" data-end="3693"><strong data-start="3526" data-end="3608">How should a mesh-convergence study be performed when element erosion is used?<br data-start="3608" data-end="3611">The fracture path and separation time change when the element size is modified.<li data-section-id="ixiusu" data-start="3695" data-end="3892"><strong data-start="3698" data-end="3763">How can I determine whether <code data-start="3728" data-end="3734">SFSA is too small or too large?<br data-start="3763" data-end="3766">In my model, changing <code data-start="3791" data-end="3797">SFSA significantly affects penetration, local plastic strain and whether the copper wire separates.<li data-section-id="1r9y7tc" data-start="3894" data-end="4018"><strong data-start="3898" data-end="4018">What is a reasonable relationship between hourglass energy and internal energy for this type of shearing simulation?<li data-section-id="1hj35fo" data-start="4020" data-end="4234"><strong data-start="4024" data-end="4111">Should the blade velocity be low enough to obtain a quasi-static shearing response?<br data-start="4111" data-end="4114">If so, which energy ratio or other criterion should be used to confirm that inertial effects are sufficiently small?<li data-section-id="zo9dgj" data-start="4236" data-end="4363"><strong data-start="4240" data-end="4363">Are there any LS-DYNA example models for wire shearing, sheet-metal shearing, blanking, punching or guillotine cutting?<p data-start="4365" data-end="4466">I am especially looking for an example that explains the complete modelling and validation procedure:</p><p data-start="4468" data-end="4657"><strong data-start="4468" data-end="4657">mesh generation → material model → damage and failure definition → blade motion → contact definition → workpiece constraints → post-processing → parameter sensitivity study → validation</p><p data-start="4659" data-end="4885">My goal is not to find one universal value for every parameter. I would like to establish a systematic method to determine whether the baseline model is reliable and then decide which keywords or parameters should be modified.</p><p data-start="4887" data-end="5046">Any example keyword files, papers, tutorials or recommendations for <strong data-start="4955" data-end="5023">copper-wire shearing, sheet-metal shearing would be very helpful.</p><p data-start="5048" data-end="5082" data-is-last-node="" data-is-only-node="">Thank you very much for your help</p>

<p>Below is what I see when I export from LSPP ICFD parts after converting mesh to MS Mesh in LSPP 4.13:  Also, the newer version of LSPP animation bar won't update correctly (like the bar wouldn't move),  also if I try to click on the animation bar from the bar on the bottom toolbar, it won't pop up.   None of these issues occurd in 4.10. </p><p>can Ansys employee provide some detail as to why LSPP is doing these things in the newer version?  Should I just stick wtih the older versions? </p><p></p>