Engine release notes

Changes in 8.1.603 (2023-09-28)

• *PRESTRESS_BOLT: Added support for headless bolts (pin merged to a plate).
• *MERGE: Various updates and improvements to penalty based method. Added merge projection displacements to the file "_node_merge_project.k". The information in this file can be used to adjust the mesh and close gaps in the merge interface.
• *MERGE_DUPLICATED_NODES: Added output to "impetus.info" and fixed an *INCLUDE offset bug.
• *REFINE: Pentahedron element bug fix.
• *PROP_DAMAGE_CL_0_45_90: Modified implementation to account for full stress tensor (not only membrane stresses).
• *MAT_POWDER_BURN: Added coupling to CFD solver.
• *PROP_DAMAGE_[TYPE]: Added (optional) user defined damage increment for secondary cracking when using node splitting. By default, a second crack is formed at damage D=2.
• *CFD_DOMAIN: Added support for CFD/SPH coupling.
• *CFD_HE: Added several built-in calibrations and added support for afterburn effects in USER defined explosives.
• *CONNECTOR_SPRING: Added spring data to state file "impetus_state_springX.k".
• *CFD_DOMAIN: Improved implementation and reduced mesh bias effects near the detonation point.
• *CFD_DOMAIN: Support for complex detonation paths and deactivation time option.
• *TIME: Added function (fcn) support for dt_max.
• *OUTPUT_SENSOR: Lagrangian CFD option (makes sensors behave like tracer particles).
• *PARTICLE_DOMAIN: Restart (state file) bug fix.
• *CONTACT: Wear calculation bug fix.
• *OUTPUT_DEBUG: New command to help the debugging of command files.
• *EROSION_CRITERION: Added effective plastic strain as erosion criterion.
• *INITIAL_MATERIAL_DIRECTION_[TYPE]: Updates for a better handling of components that are meshed with multiple elements in thickness direction.
• Updated the embedded Python library to version 3.10 (Linux).
• *MERGE: Node splitting bug fix.
• *OUTPUT_SECTION: Bug fix; "ALL" option did not work.
• *MAT_MMC_OST: Implemented for SPH.
• *FUNCTION: Added intrinsic function for sensor surface pressure "sps(ID)".
• *PARTICLE_SPH: Bug fix in elastic energy calculation (bookkeeping).
• *CFD_DOMAIN: Improved implementation of non-reflective BC.
• *PARTICLE_DOMAIN: Bug fix in state file output (impetus_state_particleX.bin). SPH pressure was corrupted when having both SPH and discrete particles in the state file.
• *PARTICLE_SPH: Implemented algorithm for SPH surface calculation, allowing for improved visualization in GUI and for CFD-SPH coupling.
• *PARTICLE_SPH_JET: Significantly improved jet correction algorithm.
• *CFD_SOURCE: New command for modeling gas sources.
• *CFD_HE: Improved accuracy of explosive mass in coarse CFD grids.
• *CFD_DETONATION: Added support for non-radial detonation paths.
• *COMPONENT_REBAR: Connectivity bug fix (related to combination of *COMPONENT_REBAR and *ELEMENT_REBAR).
• *INITIAL_STATE_HAZ: New option, allowing the weld line to be defined as a *PATH.
• *BC_SYMMETRY: Added support for rebar elements.
• *BOLT_FAILURE: New command for specifying bolt failure. The command also keeps track of bolt shear and tensile forces.
• Minor updates to impetus.info.

Changes in 8.0.374 (2023-03-15)

• *CFD_HE: Bug fix (user defined explosives in unit systems other than SI were handled incorrectly).
• *PARTICLE_SPH_JET: Bug fix (parts of the jet could suddenly disappear).
• *FREQUENCY_CUTOFF: Bug fix in handling of rigid bodies.
• *VAA: Improved edge detection algorithm.
• *PARTICLE_DOMAIN: Bug fix in initial particle distribution (some regions were not always properly filled with particles).

Changes in 8.0.368 (2023-02-27)

• *GEOMETRY_ELLIPSOID: New geometry type.
• Bug fix in intrinsic function for maximum part damage (dmgp).
• *LOAD_AIR_BLAST: Improved calculation of blast wave arrival time.
• *OUTPUT_DAMAGE_MAP: Bug fix. Mapping domain coordinates were sometimes mixed up.
• *PARTICLE_SPH: Improved SPH particle filling scheme.
• *PARTICLE_SPH_JET: Improved calculation of jet data.
• *LOAD_AIR_BLAST: Blast wave arrival time bug fix.
• *MERGE: Improved ability to handle complex geometries with symmetric and cyclic dependencies.
• *VULNERABLE_AREA_ASSESSMENT: Bug fix in handling of angle dependency and multiple layers.
• *PARTICLE_DOMAIN: Improved restart functionality. It is now possible to import multiple state files (impetus_state_particleX.bin). We also output more restart sub-domain data to impetus.info.
• *GEOMETRY_PIPE: Added support for pipe sectors.
• *PARTICLE_SPH: Internal energies for each individual sub-domain are now calculated and output to particle_sub_domain.out.
• *CONNECTOR_SPRING: Added variables (to be used in *FUNCTION) for min/max elongation (dnorm_min/dnorm_max).
• *MAT_FABRIC_ISOTROPIC: A new, easy-to-use, model for fabric materials.
• A new CFD solver for blast loading (included in Impetus DEFENSE). The corresponding commands are *CFD_DOMAIN, *CFD_GAS, *CFD_HE and *CFD_DETONATION.
• *PARTICLE_DOMAIN: Improved particle filling algorithm. Bug fix in GPU based particle-structure contact algorithm.
• *PARTICLE_SPH: General improvement of accuracy and ability to handle the interaction between materials with significantly different density and stiffness.
• *VAA: Reworked vulnerable area assessment tool, with more robust and efficient treatment of edge effects.

Changes in 7.0.280 (2022-11-25)

• *VELOCITY_CAP: Bug fix in treatment of discrete particles.
• *CONTACT: Bug fix in contact area calculation (CPU-version).
• *MAT_MM_CONCRETE: New concrete material model.
• *PART: Allow for unlimited number of parts (old limit 10,000).
• *VULNERABLE_AREA_ASSESSMENT: Added 3D hit point coordinates to .imp database (new visualization functionality in GUI).
• *FREQUENCY_CUTOFF: Added flag to deactivate regular mass scaling of affected parts.
• Updated the embedded Python library to version 3.10 (Windows only).
• GPU: if enabled, ECC information is now written to gpu.info.
• *PARTICLE_DOMAIN_CLEANUP: Added more cleanup criteria (mass, kinetic energy and velocity).
• *MERGE: Bug fix in treatment of SPH nodes that are merged to FE surfaces.
• *BC_PERIODIC: New command for periodic boundary conditions.
• *MERGE: Critical bug fix (combination of node splitting and symmetric merge).
• *OUTPUT_DAMAGE_MAP and *INITIAL_DAMAGE_MAP: Commands to facilitate simulations of multiple fragment impacts and their effect on large targets.
• *MAT_POWDER_BURN: Bug fixes and general improvements.
• *MAT_MM_CONCRETE: A new material model for concrete.
• *PARTICLE_HE: Reduced time step during detonation phase for increased accuracy.
• *PARTICLE_SPH: Improved accuracy of sliding contact (SPH to SPH).

Changes in 7.0.121 (2022-08-12)

• *VULNERABLE_AREA_ASSESSMENT: Accuracy improvement.
• *PARTICLE_SPH: Added support for fragment list generation.
• *FREQUENCY_CUTOFF: Critical bug fix.
• *PARTICLE_SPH_JET_LSC: New command for linear shaped charge (LSC) jet stabilization.
• *MERGE: Added support for SPH-FE merging.
• *MAT_JC: Restart initialization bug fix.
• *CONTACT: Bug fix in handling of pressure dependent friction coefficient.
• *PARTICLE_DOMAIN: Bug fixes to new GPU based particle-structure contact algorithm (ctype=1).
• *LOAD_DAMPING: Added optional parameter for more efficient relaxation.
• *MERGE: Bug fix in treatment of SPH-FE interfaces.
• *LOAD_GRAVITY: Added optional scale factor.
• *MAT_HOT_FORMING: New temperature and rate dependent constitutive model that accounts for recrystallization, precipitation hardening and recovery.
• Added support for GPU accelerated node acceleration and time integration calculations.
• *EROSION_CRITERION: New command, that is used to specify element erosion criteria for one or multiple parts (P, PS, ALL).
• *LOAD_DAMPING: Added support for discrete particles and SPH (DP).
• *RANDOM_NUMBER_GENERATOR_SEED: New command that can use the system clock to set the seed.
• *MERGE_FAILURE_BOLT: New merge failure criterion.
• *PROP_DAMAGE_JC_REGULARIZE: New damage model (Johnson-Cook with regularization).
• *VULNERABLE_AREA_ASSESSMENT: Extended output to .imp database.
• *EOS_GRUNEISEN: Fixed time step issue related to elements with bad aspect ratio.

Changes in 7.0.1 (2022-03-07)

• *MAT_RIGID: Fixed issue with initial spin calculation for rigid bodies connected to deformable parts.
• *MERGE_FAILURE_COHESIVE: Improved energy balance during unloading (post failure forces).
• *LOAD_AIR_BLAST: Tuned implementation for better treatment of reflected waves.
• *MAT_REBAR: Added option to reduce element size dependency.
• *VULNERABLE_AREA_ASSESSMENT: Modified gap effect implementation.
• *REFINE: Added support for element sets (ES).
• *MAT_FLUID: Material model can now be used with Finite Elements (not only SPH).
• *OUTPUT_SECTION: Improved accuracy.
• *LOAD_UNDEX: Minor accuracy improvement.
• *MAT_JH_CERAMIC: Fixed bug in SPH implementation.
• *OUTPUT: Added more fragment output options.
• Moved contact state information from impetus_stateX.k to impetus_state_contactX.k
• *PARTICLE_DETONATION: Improved tracking of the detonation front near small objects and sharp corners.
• *VULNERABLE_AREA_ASSESSMENT: Improved accuracy.
• *PARTICLE_SPH_JET: Bug fix in jet tip displacement calculation.
• *CHANGE_PART_ID: New command.
• *MAT_YEOH: New model for rubber materials.
• *MAT_BB: Orthodox implementation of the Bergstrom-Boyce model (*MAT_BERGSTROM_BOYCE will eventually be phased out).
• *PROP_DAMAGE_HC: Added fracture energy parameter GI (J/m^2) for better handling of crack propagation.
• *INITIAL_DAMAGE_RANDOM: Added option to choose which damage variable to initialize (some damage models distiguish between ductile/brittle or tensile/compressive failure).
• *PARTICLE_DOMAIN: Added optional particle-structure contact algorithm, accounting for the particle radius.
• *VULNERABLE_AREA_ASSESSMENT: Added detailed hit spot information (impact angles and armour layer thicknesses).
• *CONTACT: New option that converts friction work to heat.
• *MAT_POWDER_BURN: Minor bug fixes.
• *PARTICLE_SPH: Critical particle filling bug fix.
• *VULNERABLE_AREA_ASSESSMENT: Improved accuracy and speed.

Changes in 6.0.846 (2021-10-15)

• *VULNERABLE_AREA_ASSESSMENT: Significant accuracy and performance improvement.
• *TRIM_SLAB: Bug fix in treatment of linear hexahedra elements.
• *CONNECTOR_SPOT_WELD_NODE: Memory bug fix and improved output to impetus.info.
• *PARTICLE_HE: Updated calibrations in built-in explosive library.
• *PARTICLE_AIR/HE/SOIL: Added particle mass scale factor.
• *MAT_BERGSTROM_BOYCE: Added tensile failure criterion (limit stretch).
• *MAT_CABLE: Added yield stress and damage criterion.
• *COORDINATE_SYSTEM_FUNCTION: Function ID offset bug fix, when reading coordinate system data from an *INCLUDE file.
• *OUTPUT_SENSOR_THICKNESS: Bug fix in thickness calculation.
• *PARTICLE_SPH: Updated binary state file format and improved temperature calculation when using *EOS_GRUNEISEN.
• Node splitting bug fix. At rare occasions, some nodes were not separated at full damage.
• *PROP_DAMAGE_CL_REGULARIZE: Unit system conversion bug fix.
• GPU: CUDA Context is now properly reset for devices that are not in use.
• *MERGE: Minor bug fix related to node splitting.
• *LOAD_THERMAL_RADIATION: New command for thermal radiation.
• *LOAD_UNDEX: New command for underwater explosion pressure loading.
• *CONTACT: Contact pressure visualization bug fix.
• *ADD_MASS: New directional mass option for bodies submerged in water.
• *PARTICLE_SPH_JET: Memory bug fix.
• *CONNECTOR_RIGID: Bug fix.
• *CONTACT: Added contact penetration contour plot attribute (to .imp database).
• *MERGE: Improved accuracy when using geometry option (gid).
• *CONTACT: Friction function bug fix.
• *FUNCTION: Added vmax_dp, an intrinsic function returning maximum velocity in a particle sub-domain.
• *COUPLING_REBAR: A new command for user controlled rebar-solid coupling and for rebar element trimming.
• *MAT_BERGSTROM_BOYCE: Added support for node splitting at failure.
• *TIME: Added optional initial time variable (to be used when splitting a simulation into multiple stages).
• *OUTPUT_SECTION: Added temperature to section.out.
• *PARTICLE_DOMAIN: Improved soil-structure and SPH-structure contact.
• *MAT_REBAR: Fixed stability issue in rebar-concrete shear slip implementation.
• *VULNERABLE_AREA_ASSESSMENT: Various small bug fixes.
• Python: Added a built-in module which allows users to extract curve, table and path data directly from the python script.
• *VULNERABLE_AREA_ASSESSMENT: Bug fix in handling of user defined impact angle dependency.
• *MERGE: Added support for node sets.
• *LOAD_AIR_BLAST: Bug fix in blast wave diffraction calculations.
• *INITIAL_VELOCITY: Bug fix in handling of local coordinate system.
• *TRIM_HOLE: Bug fix, multiple commands was not handled properly.

Changes in 6.0.728 (2021-04-13)

• *INITIAL_MATERIAL_DIRECTION_PATH: A new command to define initial material directions.
• *GEOMETRY_COMPOSITE: A new command that combines multiple sub-geometries into one, more complex, geometry.
• *OUTPUT_CONTACT_FORCE: A new command that act as a contact force sensor. It samples forces and outputs the data in ASCII format (contact_force.out).
• *VULNERABLE_AREA_ASSESSMENT: Improved geometrical accuracy.
• *PARTICLE_DOMAIN: Speed-up of particle filling process (faster initialization).
• *CONTACT_ACCURACY: New command for local control of contact accuracy parameters.
• *INITIAL_VELOCITY: Added support for velocity definition in local coordinate system.
• *PARTICLE_SPH: Improved treatment of the interaction between different SPH objects.
• *ELEMENT_REBAR: Added coupling between rebar truss elements and SPH (concrete).
• *PARTICLE_DETONATION: Added an optional parameter that limits the detonation process to one specific sub-domain ID.
• *RIGID_BODY_JOINT: Fixed bug related to large joint rotations.
• *PETRIFY: New command for deformable-to-rigid switching.
• *GEOMETRY_SEED_COORDINATE: Added part ID option.
• *REMAP: Improved interpolation scheme.
• Fixed issue with nested ~if statements.
• *PARAMETER: Improved unit system conversion capabilities.
• *REFINE: Improved capabilited for pentahedra elements.
• *PARTICLE_SPH: Bux fix in interaction between different SPH materials. Default setting was incorrectly "no tension", which had a negative impact on shaped charge penetration capacity simulations.
• *GEOMETRY_PART: Bug fix in SPH and discrete particle filling algorithm.

Changes in 6.0.630 (2021-01-22)

• This version uses CUDA 11.1 and may require updated graphics driver.
• *PARTICLE_SPH_JET: A new command for stabilization of shaped charge jets.
• *BC_TELEPORT: A new command for instantaneous part translations and rotations.
• *OUTPUT_SENSOR: Moved sensors (in state file output) from impetus_stateX.k to impetus_state_sensorX.k.
• *PARTICLE_DOMAIN: Minor initialization bug fix (improved accuracy in particle filling).
• *MAT_LEE_TARVER: Bug fix in JWL EOS implementation.
• *PARAMETER: Variable name bug fix. Some character combinations were altered by the program.
• *BC_TELEPORT: Added a velocity option.
• *CONNECTOR_SPOT_WELD_NODE: An alternative input format for spot welds.
• *PROP_SPOT_WELD: A new spot weld property command.
• *PARTICLE_AIR/HE/SOIL/SPH: Added *FUNCTION based deactivation option.
• *OUTPUT_ERROR: A new command for user defined error messages in complex command files.
• *MAT_MOONEY_RIVLIN: Implemented a less conservative critical time step size estimate.
• *ACTIVATE_ELEMENTS: Extended command to allow for repeating on/off switching.
• *PARTICLE_SPH: Binary state file bug fix (artificial viscosity was not handled properly).
• *PROP_DAMAGE_CL_REGULARIZE: Bug fix in component wall thickness calculation.
• *BC_SYMMETRY: Bug fix related to tetrahedra elements.
• *PARTICLE_DETONATION: Bug fix related to multiple detonation points.
• *TRIM_SLAB: Automatic repositioning of sensors after trimming.
• *PARTICLE_SPH_JET: Added fragment counter and general accuracy improvement.
• *PARTICLE_SOIL: Added grain overlap check during initialization phase (neighboring sub-domains).
• Bug fix in resume functionality. Models using python scripts were not handled properly in the past.
• *PARTICLE_HE: Added particle overlay option for larger time steps during the detonation phase.

Changes in 5.0.538 (2020-10-12)

• *INITIAL_VELOCITY: Include offset bug fix.
• *MAT_GRANULAR_CAP: Added optional adhesion damage parameter.
• Big fix in pinned memory deallocation (GPU).
• *PARTICLE_SPH: Added support for initial stresses through the command *INITIAL_STRESS_FUNCTION.
• *MAT_POWDER_BURN: New material and functionality for propellant combustion. Unburned propellant is modelled as rigid grains and its combustion products as discrete particles.
• *UNIT_SYSTEM: Added unit system [mm, mg, ms].
• *PROP_DAMAGE_HC: Added optional strain rate sensitivity.
• *OUTPUT_SENSOR: Added plastic strain rate to sensor.out.
• *PARTICLE_DOMAIN: Added initial contact penetration parameter.
• *VULNERABLE_AREA_ASSESSMENT: A new simplified tool for ballistic protection evaluation.
• *PARTICLE_HE: Added explosive type LX-14-0.
• *ELEMENT_LTET/QTET/CTET: Bug fix in handling of data in impetus_stateX.bin file.
• *INITIAL_PLASTIC_STRAIN_FUNCTION: A command that allows the user to initialize parts with effective plastic strain fields.
• Moved *MERGE data from impetus_stateX.k to a separate file impetus_state_mergeX.k.
• *PARTICLE_DOMAIN_CLEANUP: A command that is used to deactivate discrete particles.
• General bug fixes.
• *MERGE: Include offset bug fix.
• Bug fix: User defined seed to random number generator was not working.
• Unit system conversion bug fix.

Changes in 5.0.464 (2020-07-03)

• *COORDINATE_SYSTEM: New Lagrangian cartesian coordinate system type.
• *PARTICLE_SPH: Improved formulation for reduced tensile instabilty effects.
• *PARTICLE_SPH: Added temperature output to imp database.
• *PARAMETER: Information about command file line, where the parameter value is set, has been added to impetus.info.
• *INCLUDE_BINARY: Improved error handling.
• Corrected errors in imp database (material damage output).
• *MAT_BERGSTROM_BOYCE: Unit system conversion bug fix.
• *MERGE: Improved penalty based formulation (stiffness definition that accounts for mass scaling).
• *CONTACT: Bug fix in thermal contact (related to triangular element faces).
• *INCLUDE_BINARY: Added error message if included binary file is not used.
• *GEOMETRY_SPHERE: Added optional inner radius (hollow sphere).
• *MAT_METAL: Added support for temperature dependent heat capacity.
• *PARTICLE_SPH: Added optional scale factor for particle density (particles per unit volume).

Changes in 5.0.394 (2020-05-12)

• *PARTICLE_AIR: Added support for USER defined air properties.
• *PARTICLE_HE: Added afterburn physics, where uncombusted detonation products are allowed to react with oxygen in the surrounding air.
• *COORDINATE_SYSTEM_NODE: Initialization bug fix.
• *CONTACT: Memory bug fix. A node could not be connected to more than 1000 elements.
• *PARTICLE_DOMAIN: GPU memory is now released if particle deactivation time is reached before the simulation ends.
• *COORDINATE_SYSTEM_FUNCTION: New flexible command for moving coordinate systems.
• Fixed issue with heat conduction across *REFINE interfaces.
• *MAT_CONCRETE and *MAT_CONCRETE_2018: Added associated plastic flow option on pressure cap.
• *CONNECTOR_DAMPER: A new command for resultant based rubber dampers.
• *PARTICLE_SPH: Restart bug fix.
• *SMOOTH_MESH: Improved smoothing for quadratic HEX elements.

Changes in 5.0.329 (2020-03-19)

• *LOAD_AIR_BLAST: Unit system bug fix.
• *SUBDIVIDE_PART_THICKESS: Memory bug fix.
• *LOAD_THERMAL_SURFACE: Fixed issue related to symmetry planes.
• *MAT_MMC: General updates.
• *PARTICLE_DOMAIN: Improved particle-structure contact algorithm.
• *MAT_GRANULAR_CAP: Added support for density dependent elastic properties.
• *CONTACT: Added option for better treatment of sharp edges.
• *FUNCTION: Added optional tolerance to control volume calculation vol_geo(ID, tol) and vol_geo0(ID, tol). The functions return a zero if the relative error is larger than tol.
• *PARAMETER: New functionality to allow for local parameters.
• *MAT_MMC: Added default strength cap.
• *ELEMENT_REBAR: Added support for mass scaling.
• *ELEMENT_REBAR: Mesh can now be refined with the command *REFINE.
• *ELEMENT_REBAR: Stresses, strains and damage is now written to impetus_state_rebarX.k.
• *OUTPUT: Extended fragment output (removed node splitting requirement).
• *LOAD_AIR_BLAST: Tuned implementation for higher accuracy of hemispherical charges on ground.
• *PARTICLE_SPH: Resume including material state (stresses, history variables).
• Fragment output bug fix.
• *SUBDIVIDE_PART_THICKNESS: Bug fix. Multiple commands were not handled correctly.
• *OUTPUT_USER: Bug fix. Incorrect handling of *INCLUDE offset.

Changes in 5.0.264 (2020-01-21)

• *MAT_HSS: Added strain rate hardening option.
• *MAT_LEE_TARVER: Added reference pressure for convenient conversion between unit systems.
• *MAT_MOONEY_RIVLIN: Added support for thermal properties.
• *PARTICLE_DOMAIN: New ASCII file particle_sub_domain.out.
• *SUBDIVIDE_PART_THICKNESS: A new mesh command for subdividing structures into multiple layers.
• General bug fixes.
• Updated SPH-module with new and improved functionality.
• *COMPONENT_CYLINDER: Added symmetry options and improved mesh.
• *TRIM_HOLE: New mesh command for hole cutting.
• General bug fixes.
• Fixed crash bug in Performance benchmark under Linux.
• *PARAMETER/*FUNCTION: Added modular function (mod(a,b)).
• *CONNECTOR_GLUE_LINE/*CONNECTOR_GLUE_SURFACE: Bug fix in energy book keeping.
• *MAT_HSS: Bug fix to Hosford yield criterion.
• *MAT_CREEP: Improved numerical accuracy in handling of creep flow.
• *OUTPUT_SENSOR: Added creep strain for *MAT_CREEP.
• *CONTACT: Bug fix in eroding contact.
• *LOAD_FORCE: Improved force distribution for higher order elements.
• *VELOCITY_CAP: Added option for velocity cap on HE/AIR particles.
• *PARTICLE_DOMAIN: Improved restart functionality.
• Gamma-SPH: General improvements.
• Fixed GPU compatibility problem.
• *EOS_JWL: Fixed card reading error.
• *MAT_CERAMIC: Bug fix in handling of initial damage distribution.
• *UNIT_SYSTEM: Bug fix in unit system converter (~convert_from).
• *FUNCTION: Added built-in function for maximum plastic strain in part (epsp_part).
• *PARTICLE_DETONATION: Added support for functions in detonation point definition.
• *BC_TEMPERATURE: Added support for prescribed temperature in geometry (entype=G).
• *INITIAL_TEMPERATURE: Added support for initial temperatures at nodes (entype=N).
• *BC_MOTION: Improved implementation to prevent unwanted nodes from being constrained to the symmetry plane.
• *OUTPUT_SECTION: Bug fix related to materials using node splitting.
• *MERGE: Improved handling of cohesive failure when using penalty based formulation.
• Node splitting bug fix (type 4 crack direction calculation).

Changes in 5.0.169 (2019-09-23)

• *MAT_METAL: Added Hosford yield criterion.
• *CONTACT: Improved treatment of sharp edges and added heat flux to contact.out.
• *INITIAL_STATE_HAZ: Automatic assignment of sigy0 to weld seam part.
• *FUNCTION: Added access to sensor data depsps, sig1s and dmgs.
• *LOAD_THERMAL_SURFACE: Created ASCII file load_thermal_surface.out (energy and heat flux data).
• *CONTACT: Added contact area to contact.out.
• *OUTPUT_SENSOR_THICKNESS: New sensor for thickness measurement.
• *PARTICLE_DOMAIN: Added soil/SPH forces to particle_contact.out.
• Added support for variables in command titles.
• General bug fixes.
• *MERGE: Output maximum stress levels to merge.out.
• *RIGID_BODY_UPDATE: New command to control time integraton of rigid bodies.
• General bug fixes.
• General bug fixes.
• *MERGE: Added optional parallelism tolerance.
• *MAT_FABRIC: Added C-L damage to matrix material and improved transition between compression and tension for woven fabrics.
• *OUTPUT: Added option for dump and state file output.
• General bug fixes.
• General bug fixes.

Changes in 5.0.55 (2019-05-07)

• *MERGE: Improved handling of distorted meshes.
• General bug fixes.

Changes in 5.0.52 (2019-05-02)

• *FUNCTION: Added intrinsic functions for joint spin (sxj, syj, szj).
• *SECTION_OUTPUT: New command for cross section output (force, bending moment and area).
• General bug fixes.
• *FUNCTION: Added support for custom Python functions.
• Updated to CUDA version 10.1 which requires display driver 418.96 or newer.
• *CONTACT: Added accuracy option.
• *OUTPUT_USER_COLLECTION: New command for ASCII time history output for collections of nodes or elements.
• *MAT_VISCO_PLASTIC: Added parameter to control stiffness of non-linear elastic network.
• *PROP_DAMAGE_CL_REGULARIZE: New damage model with regularization feature for coarse element grids.
• *OUTPUT_J_INTEGRAL: New command for fracture mechanics.
• *BC_MOTION: Added feature for complex activation/deactivation criteria.
• *FUNCTION: Added built-in Kronecker delta function.
• *FUNCTION: Fixed bug where normal expressions were interpreted as python calls.
• Fixed bug when Engine didn't crash properly after getting CUDA error.
• *MAT_BERGSTROM_BOYCE: Optional updates that make the implementation equivalent to Bergströms original model.
• General bug fixes.
• Critical bug fix in function parser.
• General bug fixes.
• *CONNECTOR_GLUE_LINE: Output more information to impetus.info.

Changes in 4.0.2601 (2019-01-29)

• General bug fixes.
• *RIGID_BODY_JOINT: Allow for analytical torque functions.
• New node splitting type (erode=4).
• *MAT_METAL and *MAT_HSS: Added support for temperature dependent heat expansion coefficient.
• General bug fixes.

Changes in 4.0.2569 (2018-12-10)

• Bug fix in node splitting algorithm.

Changes in 4.0.2567 (2018-11-29)

• Minor bug fixes.

Changes in 4.0.2566 (2018-11-23)

• General bug fixes.

Changes in 4.0.2452 (2018-11-01)

• Fixed GPU error in performance benchmark.

Changes in 4.0.2557 (2018-10-26)

• General bug fixes.
• *COMPONENT_BOX_IRREGULAR: New mesh command.
• *PROP_DAMAGE_CL and *PROP_DAMAGE_BRITTLE: Added optional pressure dependency.
• *MAT_LEE_TARVER: Material model for "deflagraton to detonation" simulations.
• *MAT_TRIP: Material model that accounts for transformation induced plasticity (austenite and martensite).
• *OUTPUT_SENSOR: Added pressure over yield stress and first principal stress to sensor.out.
• *MAT_HSS: Material model for high strength steels in ballistic applications.
• *PROP_DAMAGE_HC: Hosford-Coulomb damage model.
• *UNIT_SYSTEM: Added MMGMS [mm,g,ms].
• License check is now integrated with impserver.
• *PBLAST: This command is no longer supported. Users should use *PARTICLE_DOMAIN instead.

Changes in 4.0.2452 (2018-08-28)

• *SMOOTH_MESH: Added support for smoothing inside geometry.
• *PROP_DAMAGE_BRITTLE: Added parameter to control pressure dependence in tensile fracture.
• *PARTICLE_SPH: Added support for *MAT_METAL, *MAT_HJC_CONCRETE, *MAT_JH_CERAMIC and *MAT_FLUID.
• *MAT_CONCRETE: Improved treatment of viscous effects for larger critical time step size.
• *UNIT_SYSTEM: Added [g, cm, s, K].
• *MAT_CERAMIC: Added tensile cut-off for crushed material.
• *RIGID_BODY_JOINT: Added critical time step calculation.

Changes in 4.0.2452 (2018-04-25)

• GPU updates for Volta architecture.
• *MAT_FABRIC: Improved shear stiffness formulation.
• *LOAD_AIR_BLAST: Improved description of negative pressure phase.
• General bug fixes.

Changes in 4.0.2441 (2018-04-08)

• *MAT_VISCOUS_FOAM: Added hysteresis parameter.
• General bug fixes.
• Faster license check.
• Multi-GPU bug fixes.
• *CONTACT: General improvements and bug fix in contact wear calculation.
• *PARTICLE_DOMAIN: Improved flow velocity and pressure output from discrete particles.
• *PROP_THERMAL: Added support for temperature dependent heat capacity.

Changes in 4.0.2394 (2018-03-06)

• *CONTACT: Improved the algorithm with better face and edge treatment.
• *PARAMETER: Added support for vectors.
• *TABLE: Added access to *TABLE data in parameter expressions.
• General bug fixes

Changes in 4.0.2308 (2017-12-18)

• *MAT_FABRIC: Added material viscosity parameter.

Changes in 4.0.2318 (2017-12-04)

• *INITIAL_VELOCITY: Added discrete particle (DP) as viable entity type.
• *PARTICLE_SPH: Improved SPH formulation for materials with strength.
• *PARTICLE_DOMAIN: Bug fix (reflective boundary condition was not correct).
• *PARTICLE_DOMAIN: Improved handling of delayed detonation (programmed burn path is now computed at detonation time).
• *PARTICLE_DOMAIN: Improved spatial impulse smoothing formulation (parameter xsmooth).
• *GEOMETRY_EFP: Added one more parameter in the geometry definition.
• *MAT_VISCOUS_FOAM: New foam material model.
• *PRESTRESS_BLIND_HOLE_BOLT: Added automatically generated *MERGE command to impetus_state_boltX.k.
• Added material direction output to imp-database.

Changes in 4.0.2302 (2017-10-26)

• More accurate report of used GPU memory
• *MAT_CREEP: Critical bug fix in GPU-implementation.
• *PARTICLE_DOMAIN: Speed up of initialization process.
• *MAT_FABRIC: Modified evolution of damage softening.
• Added momentum of eroded mass to ASCII file part.out.
• *MERGE: Bug fix in combination self-merge and node splitting.

Changes in 4.0.2279 (2017-10-15)

• Added support for element sets (ES) in *ACTIVATE_ELEMENTS and for geometries (G) in *MERGE.
• *FUNCTION: Added intrinsic function for maximum damage in element set (dmg_es).

Changes in 4.0.2279 (2017-09-01)

• *MAT_FABRIC: new material model for fabrics.
• *PARTICLE_DOMAIN: Added thermal velocity for complex burn laws.
• Added state file for *PARTICLE_DOMAIN.
• *CONNECTOR_GLUE_LINE: Improved interpolation between normal and shear loading.
• *CONNECTOR_SPOT_WELD: Bug fix - ductility was not correct in mixed mode loading.
• *CONTACT: More calculations done on GPU with new broad search algorithm.
• *CURVE: Using (optional) title as abscissa name in curve_X.out.
• *ELEMENT_REBAR/COMPONENT_REBAR: Bug fix in rebar diameter (could not read the data from the *PART command).
• *LOAD_AIR_BLAST: Tuned diffraction algorithm.
• *MAT_CERAMIC: Modified implementation for more flexibility in describing tensile fracture.
• *MAT_FABRIC: Added GPU support.
• *MERGE: Improved automatic conversion to penatly formulation whenever constraint based method fails.
• *PART: Added user defined particle radius in element-to-particle conversion.
• *PARTICLE_DOMAIN: Fixed issue in particle-structure contact (face normal problem - extremely distorted elements).
• *PARTICLE_DOMAIN: Modified element to particle conversion (look for overlap between particles and elements to prevent leakage).
• *PRESTRESS_BOLT: Improved algorithm to identify bolts/nuts.
• *REFINE: Improved algorithm for detection of through thickness direction.
• *RIGID_BODY_JOINT: Added user defined stiffness.
• Initialization: Better and faster memory handling.
• Multi-GPU: Better memory handling. If Element processing cannot be split into equal parts (per GPU), fill mode will be used instead.

Changes in 4.0.2216 (2017-05-29)

• *LOAD_AIR_BLAST: a new command for air blast loading of structures.

Changes in 4.0.2157 (2017-04-26)

• Fixed critical bug in multi-GPU implementation of node-splitting.
• Added support for faster memory communication between multiple GPUs if hardware allows it.
• *TABLE: a new command for tabulated data.
• *PATH: a new command for definition of path in space.
• *CONNECTOR_SPOT_WELD: a new command for spot welds.
• *CONNECTOR_GLUE_LINE: a new command for definition of adhesive bonds between surfaces.
• Fixed bug in GPU scheduler.
• Improved error message handling.
• Fixed bug in unit conversion.
• Fixed bug in GPU memory transfer.
• This is the last release using CUDA 6. Future updates will be utilizing CUDA 8.

Changes in 4.0.2093 (2017-02-28)

• Fixed critical contact bugs.
• *VELOCITY_CAP: a new command that defines an upper limit to node and discrete particle velocities.

Changes in 4.0.2081 (2017-02-03)

• *CONTACT: improved treatment of facets in contact that are nearly orthogonal.
• More efficient GPU memory handling.
• Added GPU support for Mie-Gruneisen equation-of-state.
• *PARTICLE_DOMAIN: GPU speedup.
• Added resultants to "prescribed.out" for more convenient plotting.
• *PRESTRESS_BLIND_HOLE_BOLT: a command for prestressing blind hole bolts.
• Fixed bug in automatic GPU selection for devices in WDDM mode.
• Fixed bug in GPU selection where the solver didn't choose the specified device.
• Added GPU boost functionality for Tesla GPUs (K40, K80, P100, etc)
• *FUNCTION: added intrinsic functions for access to joint and sensor data.
• *OUTPUT_USER: a new command for user defined ASCII output.
• *OUTPUT_SENSOR: sensors are now written to impetus_stateX.k.
• *INCLUDE: added material ID offset and a general command ID offset.
• *RIGID_BODY_JOINT: added user defined damping.
• General bug fixes.

Changes in 3.0.1996 (2016-11-15)

• *PBLAST: extended library of built in high explosives + added functionality to model water.
• *CONTACT: optimized and improved search algorithm.
• *RIGID_BODY_JOINT: improved output to impetus_stateX.k file.
• General optimizations and bug fixes.
• *MAT_BERGSTROM_BOYCE: added alternative viscous damping law.
• *PARTICLE_DOMAIN: more flexible input structure for discrete particles/SPH (currently no GPU support).
• Additional parts of acceleration is now GPU supported.
• *MAT_FORMING_R: added damage softening option.
• Fixed bug in Materials library where the solver couldn't find the DLL file.
• *PARTICLE_DOMAIN: GPU implementation added.
• Various fixes in both impetus.info and ASCII output files.
• *PARTICLE_DOMAIN: opened up for user defined HE and SOIL.
• *OUTPUT_SENSOR: option for displacement output relative local/global coordinate system.
• *MAT_HOEK_BROWN: new material model for rock masses.
• *MAT_JC: extended thermal softening law.
• Performance benchmark feature added.
• General optimizations and bug fixes.

Changes in 3.0.1867 (2016-06-14)

• *RIGID_BODY_JOINT: extended functionality.
• *MAT_BERGDTROM_BOYCE: new material model for polymers and rubbers.
• *MAT_REBAR: added flag to activate/inactivate bending stiffness.
• Improved input error handling.
• Various bug fixes.