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ANSYS Explicit DynamicsUpdate

Mai [email protected]

+1 512‐687‐9523


• Introduction • Solve Problems that were Difficult or Impossible in the Past

– Structural Dynamics and Explicit Dynamics– Complex Interactions (Contact)

• Enhanced Productivity with Release 14– Speed Improvements – 2D Problems in Workbench– Easier Meshing – New TET element– Better Insight Into Results– Automation– New Physics

ANSYS Explicit Dynamics Update ‐ Outline


Damage to products from impact

Consumer or commercial product drop

Manufacturing process with large plastic deformation

High speed fragment or object impact

High speed collision of large objects

Cracking of brittle materials in products

Explosion near structures

Problems Addressed by Explicit Dynamics

Complex reality made easy through simulation


• Short duration localized phenomena• Transient dynamic wave propagation

o Gases, Liquids, Solids and their Interaction (FSI)• Nonlinear

o Material behavioro Contact/Interaction

• Large deformationso Large strains & strain rates

• Material failure

Nature of Explicit Dynamics Problems


Explicit Dynamics, (like Structural Dynamics) models the response of structures: from quasi static to severe loadings

Applications in: Manufacturing, Consumer Products, Aerospace, Defense, Heavy Equipment, Oil and Gas, Turbo‐machinery, …

ANSYS Edge: User Productivity, Ease of Use, Seamless CAD to Solution Environment (ANSYS Workbench)

Used by small and large organization world wide, over 800 ANSYS Explicit Dynamics customers.

Used to design products, protect products, improve processes

What is ANSYS Explicit Dynamics


Explicit Solution (Explicit Dynamics)• Time is an independent variable that is "explicitly" advanced according to a stability criteria limited by the speed of shock waves in the smallest element– Local Response

• From shock waves created by impact or other loadings• Resulting in deformation and material failure

Implicit Solution (Structural Dynamics, aka Mechanical)• Time is not an independent variable and is "implicitly" advanced according to convergence criteria– State variables being computed are not time dependent

• Collection of equations represent the relationship of all elements in the problem

• Equations solved “implicitly” with advanced matrix solutions– Global Response

• From loads applied mostly uniformly to the whole system.

Solution Methods Compared


For Implicit Solutions

• model size (number of DOF)

• size respectively grade of nonlinearity

• number of time steps to simulate

For Explicit Solution

• size of the critical time step

‐ characteristic element length

‐ sound of speed in materials (Young’s moduli & density)

• model size (number of elements)

• Length of the physical time to be simulated

Factors Influencing Calculation Times


• No convergence problems in highly nonlinear problems

• No equilibrium iteration needed

• Material failure and erosion easy to model

• High frequencies are naturally resolved because of small time steps

• Implicit‐explicit switching capability for efficiency

• Suited to a wide range of complex nonlinear problems

New Uses of Explicit Solver


Explicit GUI is the Same as Structural


• Drop test simulations – (short time dynamic range, high frequencies)

• Problems including complex contact situations – (large geometrical nonlinearities)

• Problems including sophisticated material damage and failure – (large nonlinearities, element erosion)

• Load limit analyses – (large deformations, large nonlinearities)

• Manufacturing simulations – (large deformations, large nonlinearities)

• High‐speed Dynamic analyses– (failure, fragmentation, blast wave‐structure interaction)

Extend the Range of Structural Problems


Complex Contact Example – Crimping

Equivalent Stress

Effective Plastic StrainCrimping process of seven wires. Changing contact surfacesSelf contactSevere deformation


Complex Contact – Failing Window Crank

Equivalent Stress

Effective Plastic Strain

Window Crank Mechanism


Non‐linear Material Response

Hyper‐elastic CV Boot


Material Failure and Complex Contact


• Painless problem setup– Complex geometries easier to mesh with TET elements

• New NBS TET avoids shear locking

• Fast solutions using 2‐D• Insight into part interactions

– Reaction force trackers implemented

• Generalized Shell– Discrete element, variable thickness shells– Import Polyflow and other forming simulation results

• Direct Access to results for convenient analysis and processing• Composites

– Layered composites (shells)

Productivity Further Enhanced with R14


New Tetrahedral Element

Nodal Based Strain (NBS) formulation• Overcomes both volume and shear locking• Particularly valuable in low velocity applications involving complex geometry (consumer drops like mobile phones, nuclear equipment drops)– Low deformations and bending dominates problems– Isotropic elasticity, plasticity including failure– Testing has shown that an Hourglass coefficient (Puso factor) of 0.1 should be used

• No longer Beta in Release 14

Painless problem setup


NBS TET Accuracy – Beam Bending

Case Average End Deflection

%

ANP Tet ‐0.178 ‐21.1%NBS Tet ‐0.146 0.7%MAPDL ‐0.147 0.0%


NBS TET Example – Self Piercing Rivet


NBS TET Example – Drop Test, Tablet PC

Stress Contours Front View

Stress Contours Rear View, Cover Invisible


2D Plain Strain and Axisymmetric solid analyses supported for Explicit Dynamics

• 2D pre‐ and post‐processing exposed• Plain Strain• Axisymmetric axis of symmetry now in y‐direction to be consistent with other ANSYS analysis types

Fast solutions using 2‐D


Fast solutions using 2‐D – Bullet Example


Direct and quick results of reaction forces

• Allows capture of high frequency content in response

• Scoped to Boundary Condition– Fixed, Displacement, Velocity, Remote Displacement

• Scoped to Geometry Selection– Reaction Forces, Contact Forces, Euler/Lagrange Coupling forces

• Results can be filtered

Insight into part interactions


Example – Boundary Reaction Tracker

Force reaction at each of 4 supports of component subject to impact loading


Example – FSI Force Tracker

External force time history due to fluid jet impinging on deformable surface (filtered at 10,000Hz)


Import Shell Thickness from External Data

Example – Import from ANSYS Polyflow• Polyflow is a Finite Element based CFD tool used for simulating the processing of materials such as polymers, glass, metals and concrete

• Processes modeled include extrusion, blow molding, thermoforming, fibre drawing

• Polyflow results (of predicted thickness) can now be exported to Mechanical and Explicit Dynamics

Generalized Shell – Discrete Thickness

Blow Molding with Polyflow• Initial polymer J shape (above)• Final thickness (below)


Import from Polyflow

Complete Virtual Prototyping and Testing capability in ANSYS Workbench for packaging manufacturing:

• Simulate blow molding or thermal forming process to get final thickness distribution

• Perform stress and deformation analysis with the variable thickness map (top load, crush, drop etc.)

Discrete Thickness Example


Complete Virtual Prototyping in ANSYS Workbench• Simulate blow molding or thermal forming process to get final thickness distribution with POLYFLOW

• Perform drop test of product filled with water

Discrete Thickness Shell Example


Design Assessment• Introduced in Workbench to enable customized post‐processing of Mechanical systems

• Programmable/scriptable means to access results• Explicit Dynamics can now be an upstream system for Design Assessment

Direct Access to Results


Design Assessment – Display Fragments

Fragment Volume

Equivalent plastic strain


Data Integration with ACP

ACP: Built upon a documented Workbench SDK, EVEN has developed addins to introduce ACP as a component system inside Workbench

Typical Workbench system: file management and standard actions like Update, Duplicate

Consume materials from Engineering Data

Composites


ACP Workflow Example

Implicit (MAPDL)

Explicit * (Autodyn)

Parameter Support

Allows for inclusion as part of Design Exploration

Insertion into schematic flow


Composite ExampleCFRP Baseball bat with spiral CRFP reinforcement


ANSYS Explicit Dynamics • Extends the power of Structural Dynamics for Problems that were Difficult or Impossible in the Past

• Release 14 Provides Further Productivity Enhancements– Speed Improvements – Easier Problem Setup– Better Insight Into Simulated Results– Improved Automated Use– Convenient Composite Modeling

Summary

1/32 Inc. February - Ansys © 2011 ANSYS, Inc. February 24, 2012 ... small time steps ... NBS TET...

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