Accuracy Matters – Simulation with Rupture and Failure Models

Today virtual testing is quickly reducing the need for physical product testing and is fast becoming a required component in the early stages of the design process. While simulation is having a great impact in improving product quality and time to market it also highlights the challenges related to accurately predicting and simulating model and material behavior for dynamic loading events such as a vehicle crash or impact.  Precisely modeling and simulating complex events such as material rupture, fatigue and crack propagation requires a rich simulation solution with extendable material and failure models.

While the need has never been greater, companies and engineers are actively looking for existing solvers that provide the right combination of features, capabilities and options necessary to handle today’s demanding requirements.  Advanced solver solutions would ideally enable engineers to leverage and extend both material models and failure criterion to accurately simulate and analyze these problems.

rivet

The HyperWorks & RADIOSS Difference

In RADIOSS solver a specific effort is applied to accurate predictive solutions thru the development of two dedicated libraries:

  • Material law library
  • Rupture criterion library

Both libraries are fully compatible and the user has the capability to mix the material laws and the rupture criteria.

While many commercial solver codes lack the complete yet extendable material and failure models needed to accurately simulate reality RADIOSS is different and brings together the required libraries, extendibility and customization. With RADIOSS users can mix the elements of the two libraries, creating more options to accurately model the material of the structure that is to be analyzed. If needed, users can also take into account the rupture with respect to any material laws and RADIOSS is unique in that damage or rupture criteria are embedded in some material laws. It is also possible to apply any of the criteria available in the rupture library with any material laws including those with damage.  Lastly any material law can be associated with several rupture criteria.

Rupture & Failure Models in RADIOSS

The standard rupture and failure models available in RADIOSS are:

Tuler Butcher Tsai Wu
Normal & tangent failure (connect) Chang & Chang
Johnson-Cook Hashin
Johnson-Cook with spalling effect Puck
Wilkins Ladeveze/Allix (delamination)
Tension Strain FLD
Specific Energy Bao Xue Wierzbicki (MIT)

List of the material laws with damage and/or rupture criteria embedded.

  • Von Mises elasto-plastic material with brittle damage
    • Brittle damage for Johnson-Cook model
    • Brittle damage for Reinforced concrete
    • Brittle damage for the tabulated elasto-plastic material law
    • Spotweld material law with rupture (maximum strain or energy)
  • Von Mises elasto-plastic material with ductile damage
    • Semi-analytical plastic model with plastic strain damage
    • Ductile damage for Johnson-Cook model
    • Gurson (porous material) with visco-plastic flow
  • Composite and anisotropic materials
    • Hill with the Modified Mohr-Coulomb rupture criterion (MIT)
    • Chang-Chang
    • Tsai-Wu

Click HERE to read a short explanation and example of tensile tests with steel

Applications

  • Airbus (Toulouse France): rivet rupture analysis based on the Johnson-Cook criteria.

Rivet Rupture Analysis

  •  Rupture of windshield

The forming limit diagram is based on a failure zone in the plane of principal stress. This model is well known in stamping to predicted rupture. It’s an interesting rupture model for glass.

Forming Limit Diagram - Failure Zone

Example of a windshield rupture under impact:

WIndshield Rupture Under Impact

Composites

When discussing the need for accurate material models many solver codes tend to omit composites but this is an important and necessary solver capability.  Without a composites model the virtual testing of many situations is simply not possible.  RADIOSS contains a comprehensive solution for modeling composites and also includes the failure and rupture criterion.

Click HERE to read more on the composite formulations within RADIOSS

Composite Applications

  • Quasi-static crush simulation from CMH-17

CMH-17 - Half Circle Specimen

CMH-17 - Simulation

CMH-17 - Plot

Crash of a sinus beam. The material is  Torayca composite :T700/2510. The thickness of the composite plate is equal to 1.82150 mm

 The test and simulation results are in good agreement.

  • Helicopter floor structure

 The floor structure is made of a sinus beam which must absorb the energy in case of emergency landing.  The study has been made by Eurocopter (France) for the NH90 using the Crasurv model.  The numerical model calibrated for this specific material is able  to absorb the right amount of energy thru rupture.

Helicopter Floor

  • Impact on composite.

Study made by CEDREM – Team of experts in material research and design using dynamic simulation. The impactor reaches the target at a high velocity.

For the resin matrix the Ladeveze criteria is used and for the fibers the Hashin one.

Resin rupture:

Impact on Composite

Fibers rupture:

Fiber Rupture

HyperWorks provides a full simulation solution to the CAE industry including a powerful, accurate and robust solver, RADIOSS, as well as complete modeling and visualization solutions enabling engineers to manage the entire workflow from one integrated environment.

The examples present the effectiveness of RADIOSS solutions in terms of rupture prediction associated to non linear material behaviors.  RADIOSS has been developed for different kinds of structures and materials; the main ones used in the industries today.

Development efforts ate continuing to bring innovative solutions to predict rupture and to follow the cracks propagation (XFEM method) of delamination predictions (K1 mode using XFEM too).

► Learn more about RADIOSS on the Altair HyperWorks website

Jean-Michel Terrier
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