Project Cases Detail
Georg Fischer Automotive AG implements a nonlinear spring in Code-Aster
A nonlinear elastic spring does not exist in Code-Aster. Johannes Ackva, Ingenieurbüro für Mechanik (www.code-aster.de) suggested the following approach for an implementation: Several line elements are superposed
connecting the same couple of nodes. Each line element is a linear spring in series with a gap. Such an element with a spring stiffness and a gap is realized using these Code-Aster commands:
MatElm1 = DEFI_MATERIAU(DIS_CONTACT=_F( RIGI_NOR=stiffn1, DIST_1=gap1,),)
MatElm2 = DEFI_MATERIAU(DIS_CONTACT=_F( RIGI_NOR=stiffn2, DIST_1=gap2,),)
Model=AFFE_MODELE(.. AFFE=(_F(GROUP_MA='AllSpringElms', PHENOMENE='MECANIQUE', MODELISATION='DIS_T',),),)
Res=STAT_NON_LINE(.. COMPORTEMENT=_F(GROUP_MA='AllSpringElms', RELATION='DIS_CHOC',),)
The spring stiffnesses and gap widths are adapted such that a force-displacement curve is approximated (as a polygon) which shows a progressing stiffness in compression. The practical point of this approach: no additional meshing in a PreProcessor is necessary for doubling the line elements because this can be done automatically with the Code-Aster command CREA_MAILLAGE(CREA_GROUP_MA...) So everything is codable in the command-file and runs automatically. This idea was refined using Python to represent all 3 translational and 3 angular spring directions. The figure above shows the comparision of a Code-Aster analysis using this element and results of Abaqus, both representing the same spring characteristics of a rubber element.
GF Automotive is a recognized development and serial production partner of the automotive industry and industrial applications with 10 production sites in three countries (Germany, Austria, China). The core business is the development and production of high performance castings in iron, aluminum and magnesium. GF Automotive has focused the research& development for years on weight reduction and the reduction of CO2 emissions and efficient fuel consumption.