Fracture determination device, fracture determination program, and method thereof

A fracture determination method comprising:

• extracting an element included in the heat affected zone formed around a spot weld portion of a steel material;
• generating a reference forming limit value in accordance with material property and the sheet thickness of the heat affected zone on the basis of reference forming limit value information indicating the reference forming limit value used as a forming limit value in a reference element size which is an element size used as a reference;
• using the element size and tensile strength of the steel material to change the reference forming limit value, predict a forming limit value in an element size of an element included in the heat affected zone, and generate a forming limit value in the heat affected zone;
• running a deformation analysis by using input information for the deformation analysis of the steel material by a finite element method including material property and sheet thickness of the steel material and outputting deformation information including strain of each element included in the heat affected zone;
• determining maximum principal strain and minimum principal strain of each element included in the heat affected unit;
• and
• determining whether each element in the analysis model will fracture on the basis of maximum principal strain and minimum principal strain of each element for which the principal strain is determined and a heat affected zone forming limit line specified by the heat affected forming limit value.

A non-transitory computer readable medium having stored therein a fracture determination program for causing a computer to perform processing to:

• extract an element included in the heat affected zone formed around a spot weld portion of a steel material;
• generate a reference forming limit value in accordance with material property and the sheet thickness of the heat affected zone on the basis of reference forming limit value information indicating the reference forming limit value used as a forming limit value in a reference element size which is an element size used as a reference;
• use the element size and tensile strength of the steel material to change the reference forming limit value, predict a forming limit value in an element size of an element included in the heat affected zone, and generate a forming limit value in the heat affected zone;
• run a deformation analysis by using input information for the deformation analysis of the steel material by a finite element method including material property and sheet thickness of the steel material and output deformation information including strain of each element included in the heat affected zone;
• determine maximum principal strain and minimum principal strain of each element included in the heat affected unit;
• and
• determine whether each element in the analysis model will fracture on the basis of maximum principal strain and minimum principal strain of each element for which the principal strain is determined and a heat affected zone forming limit line specified by the heat affected forming limit value.