Patent ID: 11958137
Assignee: THE REGENTS OF THE UNIVERSITY OF MICHIGAN
Field: Computer technology (Electrical engineering)
Classification: CPC B  G | IPC B  G

Claim 0:
1. A unified method for estimating fatigue for a welded structure under load, comprising:
generating a finite element model for a given structure;
calculating a distribution of structural stress within the given structure using the finite element model and while the given structure is under a given load, where the distribution of stress is determined in relation to a plane intersecting the given structure;
determining whether stress exceeds yield strength of material comprising the given structure;
calculating a distribution of structural strain experienced within the given structure using Hooks law in response to a determination that the stress is less than yield strength of material;
calculating a distribution of structural strain experienced within the given structure using an analytic method in response to a determination that the stress exceeds yield strength of material, where the distribution of structural strain is calculated in part from the calculated distribution of structural stress and the distribution of structural strain is defined in relation to the plane by at least two closed-form expressions which account for stress that exceeds yield strength of material; and
calculating a fatigue life for the given structure when placed under the given load using the calculated distribution of structural strain using a master E-N curve, wherein, for a spot weld, the distribution of structural stress within the given structure is calculated by
modeling a spot weld as a beam coupled between two or more plates;
defining a square area that encapsulates the spot weld;
extracting nodal forces and moments along the edges of the square area from the finite element model;
calculating structural stresses for the spot weld from the computed nodal forces and moments using a superposition method; and
welding the given structure in accordance with the calculated fatigue life for the given structure.