Patent ID: 8027819

Claim:
A fracture prediction device for use with a spot welded portion, comprising: an input arrangement configured to input at least one of a tensile strength (TS) of a material, a plate thickness t, a nugget diameter d of a spot welding, a plate width w of a particular joint, or a rotation angle θ of the joint plates in a tension testing procedure which is at least one of a cross tension testing procedure or a shear tension test procedure at a spot welded joint; a first calculation arrangement configured to determine a fracture limit load (Fcts) as a fracture strength parameter of the spot welded portion in a cross tension using a formula (a) and a fracture limit load (Ftss) as a fracture strength parameter of the spot welded portion in a shear tension using a formula (b), based on a stress concentration factor α and at least one of the inputted tensile strength TS of the material, the plate thickness t, the nugget diameter d of the spot welding, the plate width w of the joint, or the rotation angle θ of the particular joint in the tension testing procedure, wherein the stress concentration factor α is at least one of (i) defined by a formula of (TS)/(mean tensile stress σo) or (ii) calculated using a stress concentration factor calculation formula, and wherein Fcts= 2 TSWt sin θ/α ( a ) Ftss=TSW t/α ( b ); a parameter storage arrangement configured to store the fracture strength parameter by each steel type; and a second calculation arrangement configured to analyze a fracture of the spot welded portion by providing the fracture strength parameter stored in the parameter storage arrangement into a fracture prediction formula in which a deformation at a periphery of the spot welding portion is modeled by a finite element procedure, wherein the fracture prediction formula is based on a shear force and a vertical force with respect to the spot welded portion.