Assignment 4-RADIOSS Material Laws Challenge

AIM:

To run crash analysis on the given model by applying different materials laws available in Radioss and post-process the results

Objective: To simulate the startup files provided and compare the outcomes. Based on the specified settings, there will be seven examples, which will mostly be contrasted via charts and animations. The files that require attention are the FAILURE_JOHNSON_0000.rad file and the LAW27_0000.rad file. The cases are as follows:

1. Law 2 (file: FAILURE_JOHNSON_0000.rad) - base simulation.

2. Law 2 (file: FAILURE_JOHNSON_0000.rad) with Ifail_sh = 1, Dadv = 1, and Ix fem = 1.

3. Law 2 (file: starter file for case 2) with fail/JOHNSON card deleted.

4. Law 2 (file: starter file for case 3) with EPS_p_max value deleted

5. Law 1 (file: FAILURE_JOHNSON_0000.rad) with fail/JOHNSON card deleted and values for density, E, nu assigned

6. Law 27 (file: LAW27_0000.rad) with recommended shell properties

7. Law 36 (file: LAW27_0000.rad) with recommended shell properties and given reference curve.

   Hypothesis:

   • The selection of the material affects how accurate the simulation is.

   • When running a simulation, it's critical to select the appropriate material and supply accurate material data.

   • Among the many material qualities and libraries available in RADIOSS are concrete, foam, rubber, composites, and more.

   • Among the material laws that are utilized in commerce are:

   • Law 1: Elastic (Isotropic Elasticity)

   • Law 2: Johnson-cook (Isotropic Elasto-plastic)

   • Law 27: Elastic-plastic brittle

   • Law 36: Elastic-plastic tabulated

   • Law 42: Ogden (visco hyperelastic)

   • Law 70: Foam

   Law 1 of Isotropic Elasticity

   1. A substance is said to be isotropic if its qualities are constant in all three directions. RADIOSS offers two different kinds of elasticity under isotropic elasticity. Elastic that is linear LAW1 supple

   2. LAW69 is hyperelastic. Hyperelastic tabular data, LAW82 Ogden

   3. The RADIOSS elasticity law is a linear connection between stress and strain, similar to Hook's law of elasticity.

   4. For shell, solid, truss, and beam elements, it is accessible. As previously stated, it is only applicable to elastic materials.

   5. Poisson's ratio (n) and Young's modulus of elasticity (E) are used to calculate the stiffness of the material. G = E 2 (1 + V) is the formula for calculating the shear modulus.

      Restrictions:It is not possible to employ elastic materials in heavy deformation scenarios like blow molding, etc. Law 2 Johnson-Cook material with high yield can be employed in the situation of large deformation.

      Isotropic Elastic Polymer: Different kinds of elasto-plastic material laws are offered by RADIOSS. It contains all of the material models based on the following: visco-plastic flow, ductile damage, and von mises hardening without damage. Johnson-cook/JOHNS and tabulated piecewise linear/PLAS_TAB will be examined in this section.

      Johnson-cook material (PLAS_JOHNS) - Law 2

      1. This law uses the Johnson-Cook material model to depict an isotropic elasto-plastic material.

      2. Material stress is expressed by the model as a function of temperature, strain, and strain rate.

      3. Plastic strain at failure is all that is indicated by the EPS_max option on the material card. When one integration point surpasses EPS_max, the element fails.

      4. Now, there may be situations in which the EPS_max produces erroneous results if failure is only determined by EPS_max.

      5. The /FAILS/JOHN card gives the user more control over the failure of the Johnson-Cook strain, thus we have that option to prevent this.

      Piecewise linear elastic plastic material LAW36-PLAS_TAB

      1. The LAW36 material law facilitates the modeling of isotropic elasto-plastic materials at varying strain rates by utilizing user-defined functions for the work hardening segment of the stress-strain curve.

      2. The stress-strain curve following the yield point is all that is specified by the curve. There is no yield point set.

      3. It is possible to use this material rule for shell and brick elements alike.

      4. The elastic component of the work hardening section is derived from the inputted Young's modulus and Poisson's ratio if the user defines it.

      5. One can define an infinite number of stress-strain curves. It's crucial that the strain rate curves don't cross over one another.

      6. The plastic strain curve needs to begin at zero.

      7. Using fct_Idp, the user may additionally enter yield stress in relation to pressure.