Week-6 Calculate the Stretch Ratio by comparing the ELFORM (-2,-1,1,2) with Ogden_Material Model.

Introduction

the given material is ogden rubber, it is hyper elastic material. hyperelastic material are modeling rubber -like material in which deformation is large.hyperelastic material use strain energy to derive the relation between stress and strain

the given material properties are of ogden material.

Aim: to create block of volume 10*10*10 and compare stress vs stretch with element formulation of 1,-1,2,-2 by giving appropriate boundary conditions

this is considered as quasi-static method so we use implicit analysis because, implicit is used for slow process in this simulation is solved for static equilibrium where sum of forces is zero. so it can besolved by inverting matrix and activating IMPLICIT_GENERAL

Procedure-

- a cube is created by shape mesher in mesh tools by 10*10*10

-boundary spc set is given to one face of cube or block

-boundary prescribed motion is given to opposite face of spc set.

- load curve is created by define load curve

- IMPLICIT_GENERAL is actiavted(IMFLAG=1) and DT is given as 0.05

-IMPLICIT_AUTO keyword is given

-IMPLICIT_SOLUTION is given by nsolver=12 (explicit to implcit)

-implicit solver is activated (LSOLVR=4)

-SECTION_SOLID is defined by using various element formulations(1,-1,2,-2)

-Control termination is given as 5

-DATABASE_D3PLOT is given as 0.1

file is saved and solved

RESULTS-

the file is solved

by the given results true stress and strains are given by ls dyna, th graphs below are are solved manually by excel

true strain=ln(1+engstress)

true stress = eng stress(1+eng strain)

1+eng strain= stretch

animation

el-1

el-2

el-(-1)

el-(-2)

conclusion-

the above graphs are for different element(128,140). the graphs for 128(el1,el-2), 140(el2,el-1) are same except for use of comptational power for caluclating using element formulation