Posts Tagged "abaqus 2020 release"

This is a relatively bigger blog compared to previous ones because of an obvious reason; it covers a broad spectrum of non-linear enhancements which is Abaqus core technology. The blog covers four sections: additive manufacturing, element technology, material enhancements and fracture mechanics along with few other minor enhancements

Additive manufacturing:

  • Pattern based thermo-mechanical analysis: While in many cases laser scan paths are available to simulation users it is not always true. For those situations in which machine users do not wish to share their machine IP’s, a pattern based approach has been introduced which uses a raster scan path instead of a trajectory scan path. Material orientation and Anisotropic behavior are supported but not suitable for detailed microstructure simulation. This application is different from eigen strain simulation.
  • Event series enhancement: 2GB data size limit of event series was removed in 2019xGA and now event series can include up-to 420 million events.
  • Free surface evolution enhancements: In case of tie constraints, algorithm has been enhanced to include ties that are not activated until the underlying element becomes active.
  • Output enhancements: MAXPSCRT has been introduced to include maximum principal stress crack initiation criterion. It is available for both field and history outputs. BLADEINTERFERER has been introduced to predict clash between recoater and printed part. This will be available in 2020xFD01.

Element Technology:

  • Shear panel element update: SHEAR4 was introduced in 209xFD01 to model thin reinforced plates. It supports buckling. Equivalent shear flow output called SQEQ is supported.
  • Pyramid heat transfer element: DC3D5 has been introduced to manage transition between tetrahedral and hexahedral elements in thermal analysis.
  • Fluid pipe element enhancements: These elements now support following Non Newtonian flows as well:

Material enhancements:

  • VUMAT enhancement: A parameter has been added to define alternate bulk and shear modulus that can be used by explicit to find suitable time increment. It is called EFFMOD and visible in viewer. Abaqus CAE support is available from 2020xFD01.
  • Kinematic hardening enhancement: The material model has been enhanced to model stress relaxation behavior for metals subjected to step strain input. Suitable for metals that show viscoelastic like behavior during step inputs.

Creep Laws enhancement: Current creep models have A with dimensionality that creates ambiguity. The strain and time laws have been enhanced as follows to make A dimensionless. These enhancements are applicable to all the creep models.

Viscoelastic material enhancement: The prony series has now been enhanced to include frequency domain as well. Earlier prony series was valid in time domain only.

Yield surface enhancement: The non quadratic yield surface has been introduced in 2019xFD04. It is referred to as Barlat Plasticity. The stress component requires 18 coefficients and 1 exponent.

  • Metallurgical phase enhancement: In prior releases, the effect of additive manufacturing and other heat treatment processes on material properties at microstructural level required USDFLD subroutine. Effective 2020xFD01, this routine has been included on the material definition itself. Inservice performance of printed parts can now be more accurately simulated.

Injection Molding:

  • 3DX injection molding compatibility: The fiber orientation and residual stresses from third party simulation such as Moldflow can now be converted to a SIM file format. That means the 3DX structural simulation apps can now read moldflow results to predict in-service loads and warpage from third party plastic injection results.

Pre-tension enhancements

  • Non linear enhancement: In earlier releases, the direction of pre-tension section normal was not updated even in general step. Effective 2020xGA, the cut section normal direction can be updated in large displacement or large rotation analysis. It is activated as follows in the input file

*PRE-TENSION SECTION, FOLLOWER = (YES/NO)

Fracture Mechanics enhancements

  • Linear elastic fatigue enhancements: Linear elastic fatigue crack model was introduced recently in collaboration with NASA ACC team to model crack propagation for cyclic fatigue cycles. It allows for change in contact conditions as well as non-linear geometry effects. Several enhancements have been made in this model in recent FD’s. In 2019x FD03, an alternative method to smoothening of crack front was introduced. In 2019x FD04, mode dependent stiffness degradation was introduced.
  • Cohesive elements for Multiphysics: Couples temperature-displacement cohesive elements have been introduced to simulate debonding due to thermal expansion as well as hydraulic fracture. These elements are COH2D4T, COHAX4T, COH3D6T, COH3D8T. Coupled temperature-displacement-pore pressure elements available as well to include gap conductance effect. There is no change in the structural response of these elements.

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While few of the Abaqus explicit enhancements in 2020x have been discussed in previous blogs on contact, this particular blog article specifically focuses on many more enhancements in explicit, with or without contact.

  • DT based element deletion: While explicit jobs never exit with fatal errors due to lack of convergence, they can still give fatal errors because of severe element distortion. An element deletion criterion has been introduced that allows user to set a trigger for element deletions based on element area, element volume, stable time increment and characteristic length. These triggers can be defined either as absolute or as ratios.
  • Linear Kinematic conversion: This is yet another approach to avoid fatal errors because of severe element distortion. In this approach, the elements are transformed to linear elements based on certain trigger threshold on distortion. It is applicable to most of continuum tetrahedral and hexahedral elements.

Enhanced CEL approach: Conventional CEL approach is good for solids only. When applied to liquids and gases, it may cause leakage especially when fluids create high pressure gradient, when fluids have large tangential velocity or at the location of sharp corners. The enhanced CEL contact formulation fixes this problem and is applicable to both solid and shell meshes. However, this enhanced formulation is more expensive in memory and computation.

Hybrid message parsing (HMP): This is an enhancement in parallel processing that can combine MPI (DMP) based parallelization and Threads (SMP) based parallelization. The solution can utilize thread based parallelism within a node as well as MPI to communicate between the nodes. It results in fine grained dynamic load balancing because when a thread completes its own elements computation work, it helps other threads within the same MPI rank.

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Subsequent to the blog article on few functionalities in Abaqus CAE 20202x, this particular blog article mentions enhancements in Abaqus solver 2020x contacts and constraints. The enhancements would be mentioned in reverse chronological order and few of these have been introduced in FP’s of 2019x as well.

  • Interference fit in Abaqus explicit: This feature has been in waiting list since long by users and its finally available now. Earlier releases of explicit had an option of strain free adjustment only for overclosures. From 2020x, if initial overclosure is “x” and interference is defined as “y”, then strain free adjustment is performed till “x-y” and rest is treated as interference being resolved through a smooth amplitude curve. That means a “two in one advantage” for explicit. Moreover, it is supported in Abaqus CAE.

Change in contact status legend: To make output more meaningful for the users, the contact status has been changed to bonded and “not in contact” as shown below. This is applicable to both standard and explicit.

Rate dependent cohesive damage: The damage initiation and damage evolution laws now have parameters to include rate dependency in cohesive contact for explicit. Earlier this feature was available in cohesive elements approach only. Effective since 2019xFD04.

  • Material based general contact property assignment: The conventional process of property assignment in general contact is a three-step process. First, define sets of elements. Second, use sets to define surfaces. Third, use surfaces in property definition. From 2020x, material can be directly called for surface assignment if that approach helps. This is true for both standard and explicit.

Thermal expansion of rigid bodies: The analytical and discrete rigid bodies have been existing in Abaqus since long. However, when it comes to combined structural and thermal steps, a body very rigid from structural perspective may expand well when heated. To incorporate this effect, thermal expansion of rigid bodies feature is now included in Abaqus standard. This is applicable to kinematic couplings as well as for bodies are not explicitly defined through a CAD geometry.

  • Small sliding in general contact: This is again a BIG enhancement based in users request. Small sliding substantially reduces the contact search time because it is based on flat surface approximation. When used correctly, it results in convergence improvement and less overall solution time. However, its absence in general contact was a bit bothersome. From 2020x, small sliding exists in general contact for standard.

General contact enhancement for Multiphysics: Beam elements have been introduced in general contact for thermal and thermal electrical procedures. This may be helpful in approximating some large size applications such as heat exchangers by modeling pipes as beam elements.

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