The general contact pre-process commands, GCGEN and GCDEF, have been enhanced to offer improved accuracy and reduced operation speed. Improvements target the main functions of these commands: generating the general contact surface, assigning contact properties, and listing or detailing the properties. These enhancements lead to faster pre-processing times and more reliable contact definitions, particularly useful when working with large assembly models.

Moment convergence is now checked at the pilot node of TARGE170 when target elements have rotational degrees of freedom (DOFs). Previously, this check at the pilot nodes was ignored if there were no structural elements with rotational DOFs in the model. This improvement improves accuracy.

The new CNCHECK, MERGE,,,,MPC pre-processing command addresses the issue of overconstraint in MPC bonded contact by automatically merging all possible overlapping contact pairs. Key benefits are improved convergence behavior and a reduction in solution time and memory usage. This new functionality is especially useful for large, complex models with many interconnected parts using MPC bonded contact definitions.

If a nonlinear analysis fails in the very first iteration due to pivoting errors (usually for under-constrained problems), use the new WKSP command to improve stability and convergence. The WKSP command automatically adds weak springs (COMBIN14 elements) at the nodes and DOFs exhibiting near-zero pivots and reattempts the solution.

The CNTGEN (contact generation) and SFCGEN (surface generation) commands have been updated to support nodal components in addition to the previously supported EFACE (element face) components. Nodal components are supported for both the 2D and 3D contact elements to setup contact and MPC (multi-point constraint) surface constraints.

If nodal components are provided for the contact and target surfaces, issuing CNTGEN generates contact and target elements based on the dimensionality of the underlying mesh elements:

The SFCGEN command now creates MPC surface-based constraints over the surfaces formed by the nodal components based on the user-defined contact element type (ICTY).

Overall performance has been improved for the generation of multiple spot welds with node-to-surface configuration. Modeling large assemblies for the automotive industry requires generating several layered spot welds at multiple locations. Issuing several spot weld generation (SWGEN) commands to simulate this process can be computationally expensive.

To reduce spot weld generation time of large assemblies, memory optimization and the definition of element attributes like real constants, are now done once at SWGEN,START. The program automatically assigns the next available real constant for subsequent spot welds, speeding up the overall process.

The 2D-to-3D bonded multi-point constratint (MPC) contact feature for solid assemblies now supports thermal and coupled structural-thermal analyses. You can combine multiphysics 2D elements (PLANE222, PLANE223, PLANE292, PLANE293) elements with 3D elements (SOLID278, SOLID279, SOLID226, SOLID227) to simulate heat transfer and deformation due to temperature change across their bonded contact interfaces. For more information, see Modeling a 2D/2.5D-3D Solid Assembly in the Contact Technology Guide.

To boost the performance of large-scale distributed-memory parallel (DMP) contact models, the solver now separates the underlying elements of CONTA175 into different processing domains. Previously the CONTA175 elements and their underlying elements were grouped into the same DMP domain. This change activates when the CONTA175 elements do not need underlying element information (KEYOPT(5) = 0, KEYOPT(11) = 0, KEYOPT(4) = 0 or 3, target element TARGE170 KEYOPT(7) is not equal to 0, and the contact pair does not include geometry correction). This performance improvement results in a lower load balance ratio and better scalability for high-core DMP models involving contact.

The initial contact stiffness for the contact element on top of a gasket element has been updated to improve convergence behavior for nonlinear structural analysis.

You can now control the displacement increment based on the pinball region of open contact pairs. Issue CUTCONTROL, DSPLIMIT, CONT to limit the substep incremental displacement to a factor times the minimum pinball radius of all open contact pairs. This helps prevent missing the contact when a displacement increment causes a contact pair to transition from no-contact to far-field. See the CUTCONTROL command description for details.

An optional stop tolerance (STOP_TOL) argument is available for the NLHIST command's smart stop feature. The STOP_VALUE, STOP_COND and STOP_TOL arguments automatically tailor a nonlinear solution to stop when the value of a tracked variable reaches the specified range, using bisection followed by time increment prediction.

A new algorithm is used for updating the user-defined thickness of 3D gasket elements (INTER194 and INTER195) with the thin-solid option (KEYOPT(2) = 2 or 3) in geometric non-linear analyses (NLGEOM ,ON). The new algorithm improves the non-linear solution robustness and the accuracy of element results.

The SHELL229 coupled-field shell elements are now supported as embedded elements, and 3D coupled-field solid elements (SOLID225, SOLID226 and SOLID227) are now supported as base elements in the direct-embedding workflow. For more information, see Direct-Embedding Workflow.

The general axisymmetric elements SOLID272 and SOLID273 now support the mono harmonic option (KEYOPT(2) = 1 and MODE) in linear perturbation modal analyses, enabling the analysis of higher-frequency modes. Furthermore, by changing the MODE number, multiple load steps are supported in subsequent modal analyses. The out-of-plane contact behavior for SOLID272 and SOLID273 (KEYOPT(2) = 1) is supported using a 3D contact pair: CONTA175 and TARGE170.

The 3D structural shell elements (SHELL181 and SHELL281) now support selected solution output locations using the EMSEL command. This feature provides flexibility in selecting output locations.

PLANE183 now supports the nonlocal damage formulation. SOLID186 and SOLID187 elements have been updated to support nonlocal damage when using the mixed u–p formulation. These enhancements enable use of generalized fatigue damage (implicit gradient regularization) to better capture the distributed nature of damage in real materials by averaging variables over a finite neighborhood using a characteristic length scale. This leads to more objective and reliable simulation results and improved convergence stability. Also, results no longer spuriously depend on mesh size, especially when material softening or strain localization occurs.

Multiple voids per substep can be created based on a criterion selection, and these voids are non-overlapping. The damaged element with the maximum error indicator value is selected as the element for single void insertion, using the NLADAPTIVE,,,REMMAT command with VAL3 = 1. For the multiple voids per substep approach, you can include loaded boundary elements by issuing the NLMESH,VBND command with VAL1 = 1. With this new variant, you can now create more than one void per substep based on the criterion value and all damaged elements are considered for void creation.

Automatic detection and deletion of orphaned element patches after the element removal process (NLADAPTIVE,,,REMELM) are now supported using the NLMESH command with Control = ISLD. This leads to a more stable solution process and convergence when many elements are deleted.

The Arruda-Boyce, Bergstrom-Boyce and the TNM material models are now supported in a nonlinear adaptivity analysis and rezoning analysis. For more information, see Nonlinear Mesh Adaptivity Requirements and Limitations and Rezoning Requirements and Limitations.

Finite-strain material models now support swelling effects that can act independently of or in combination with thermal deformation. The total deformation gradient is multiplicatively split into mechanical, thermal, and swelling parts, with stresses driven by the mechanical component.

AI-based automatic initialization of material parameters is now supported for more plasticity models, including both rate-independent and rate-dependent plasticity. For more details, see Plasticity Models in Step 4. Initialize the Coefficients.

You can now fix selected coefficients prior to automatic initialization, so that only unfixed coefficients are initialized. This feature is supported for hyperelasticity and plasticity.

You can also now use automatic fitting in hyperelasticity to generate material parameters directly from experimental data, skipping the curve fitting process. This is done with the TBFT command. For details, refer to Automatic Fitting.

The program can now optionally consider anisothermal derivative terms in stiffness and damping matrices for temperature dependent material properties in a thermal analysis with and without nonlocal damage. This can help with convergence when material parameters are strongly temperature dependent.

A damage cap can now optionally be applied to restrict further damage evolution beyond a specified limit for Regularized Generalized Damage and Ductile Damage. This can prevent elements from reaching unrealistically low stiffness values, which could lead to convergence difficulties.

The extended Drucker-Prager Cap Creep model can now be used with custom creep models (TB,CREEP,,,,100) implemented using the UserCreep subroutine. You can now use the get_ElmData subroutine with the ‘ECCR’ option in UserCreep to identify if the creep model for the compaction cap region or the shear region is requested.

A new general power law model for grain-growth kinetics is now available, enabling more accurate simulation of normal grain growth during sintering. Unlike the previous parabolic model, this approach supports variable growth exponents, making it suitable for diverse materials such as ceramics and metals used in powder metallurgy.

Three new stress evolution models are available for accurate modeling of sintering stress. This enhancement builds upon existing stress calculation by adjusting the calculated stress. The new models are based on work by McMeeking & Kuhn, Ashby, and Shinagawa.

For SMART crack-growth analysis, you can now change the mesh-independent initial-stress data at any loadstep for conversion to an equivalent crack-surface traction load. The existing data must be cleared from the solution database before reading the new data. By default, the initial-stress data specified at the first loadstep is carried over to subsequent loadsteps.

When this load method is used with crack-initiation, the traction load is applied only after the crack begins to form and its surfaces become available for load application.

The fracture parameter SIF calculation can now provide accurate results for both 2D problems (PLANE182 and PLANE183) and 3D problems (SOLID185 and SOLID186) undergoing large deflection and/or rotation.

When a model includes any superelement (MATRIX50), SMART crack growth can now be analyzed in the nonsuperelement mesh. The superelement must not be in the crack growth remeshing region. The superelement should be connected to the nonsuperelements via shared nodes or constraint equations (CE or CEINTF) or contact surface elements (CONTA174).

The following benchmark problem has been added at this release:

SMART crack-growth analysis now supports tetrahedral-to-hexahedral models. This feature now allows you to use SOLID185 and SOLID186 elements mixed with SOLID187 elements. SOLID185 and SOLID186 elements can be in wedge, hex, or pyramid shapes. After crack growth occurs, the remeshing domain mainly consists of SOLID187 elements. If a high-order element is connected to a low-order element, the remesher will use a special connection by dropping the mid-side nodes in the element.

In previous versions, restarting a Harmonic Balance Method (HBM) analysis required manually extracting the initial guess from a results file (.rst) using a custom macro. This approach often led to discontinuities in the generated results files and added complexity to the workflow.

You can now restart an HBM analysis using the standard command ANTYPE,HARMIC,RESTART, which includes the option to select the desired substep. The results files are rewritten to maintain solution continuity in the selected frequency range. For details, see Restarting an HBM Analysis in the Harmonic Balance Method Analysis Guide.

Transient (ANTYPE, TRANS) thermal multistage cyclic symmetry analysis is now supported in addition to the already supported multistage steady-state (ANTYPE, STATIC) thermal analyses. Models supported for these analyses have only temperature degrees of freedom (DOFs) active during the solution. See Multistage Thermal Analysis in the Multistage Cyclic Symmetry Analysis Guide.

Cyclic symmetry linear perturbation harmonic analysis now supports the use of MPC184 joint elements in the model.