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

Claim 8:
9. 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 curvilinear plane of the given structure, such that the curvilinear plane is modeled with multiple elements of the finite element model and each element is modeled with three nodes along each element edge 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;
determining whether the given structure is subject to non-proportional multiaxial load condition;
in response to a determination that the given structure is not subject to non-proportional multiaxial load condition, calculating a structural strain range using Rainflow cycle counting;
in response to a determination that the given structure is subject to non-proportional multiaxial load condition, calculating a structural strain range as a function of the non-proportional damage parameter which accounts for non-proportional loading effects between normal and in-plane shear stresses; and
calculating a fatigue life for the given structure when placed under the given load using the structural strain range using a master E-N curve; and
welding the given structure in accordance with the calculated fatigue life for the given structure.