Method of identifying critical elements in fatigue analysis with von mises stress bounding and filtering modal displacement history using dynamic windowing

A computer implemented method of dynamic durability analysis and fatigue area identification for a structure comprising:

• simulating a finite element model of a structure to determine modal stresses and modal displacements for an element of the structure;
• performing a modal transient analysis using the modal displacements;
• determining a stress bound for the element from the modal stresses and modal transient analysis;
• determining if the stress bound for the element is greater than a predetermined value, wherein the stress bound is the upper bound of a Von Mises stress;
• identifying the element as a critical element if the stress bound for the element is greater than the predetermined value;
• determining a stress time history for the critical element;
• using the stress time history to perform a fatigue analysis to identify an area of fatigue within the structure;
• and
• filtering the modal displacement time history using a dynamic window, prior to said step of determining a stress time history.

A computer implemented method of dynamic durability analysis and fatigue area identification for a structure comprising:

• simulating a finite element model of a structure;
• determining a modal stress for each element of the finite element model;
• determining a modal displacement time history for each element of the finite element model;
• determining a minimum modal displacement value and a maximum modal displacement value for each mode from the modal displacement time history;
• determining an upper bound and lower bound of a normal stress and a shear stress for each element;
• determining a stress bound for each element from the upper bound and the lower bound of the normal stress and the shear stress;
• determining if the stress bound for each element is less than a predetermined value, wherein the stress bound is the upper bound of a Von Mises stress;
• identifying the element as a non-critical element if the stress bound is less than the predetermined value;
• identifying the element as a critical element if the stress bound is greater than the predetermined value;
• determining a dynamic stress time history of the critical element;
• using the dynamic stress time history to perform a fatigue analysis on the critical element to identify an area of fatigue within the structure;
• and
• filtering the modal displacement time history using a dynamic window, prior to said step of determining a dynamic stress time history.

A computer implemented method of dynamic durability analysis and fatigue area identification for a structure, said method comprising the steps of:

• simulating a finite element model of a structure;
• determining a modal stress for each element of the finite element model;
• determining a modal displacement time history for each element of the finite element model by a modal transient analysis;
• determining a minimum modal displacement value and a maximum modal displacement value for each mode from the modal displacement time history;
• determining an upper bound and lower bound of a normal stress and a shear stress for each element;
• determining a stress bound for each element from the upper bound and the lower bound of the normal stress and the shear stress;
• determining if the stress bound for each element is less than a predetermined material value;
• identifying the element as a non-critical element if the stress bound is less than the predetermined value;
• identifying the element as a critical element if the stress bound is greater than the predetermined value;
• filtering the modal displacement time history using a dynamic window, wherein the dynamic window is a maximum modal displacement less a minimum modal displacement multiplied by a predetermined percentage;
• determining a dynamic stress time history of the critical element;
• and
• using the dynamic stress time history to perform a fatigue analysis on the critical element to identify an area of fatigue within the structure;
• and
• wherein the stress bound is the upper bound of a Von Mises stress.

A computer implemented method of dynamic durability analysis and fatigue area identification for a vehicle comprising:

• simulating a finite element model of a structure for a vehicle;
• determining a modal stress for each element of the finite element model;
• determining a modal displacement time history for each mode of the finite element model;
• determining a minimum modal displacement value and a maximum modal displacement value for each mode from the modal displacement time history;
• determining an upper bound and lower bound of a normal stress and a shear stress for each element;
• determining a stress bound for each element, wherein the stress bound is a Von Mises stress determined from the upper bound and the lower bound of the normal stress and the shear stress;
• determining if the stress bound for each element is less than a predetermined material yield strength;
• identifying the element as a non-critical element if the stress bound is less than said predetermined yield strength;
• identifying the element as a critical element if the stress bound is greater than said predetermined yield strengths;
• filtering the modal displacement time history using a dynamic window;
• determining a dynamic stress time history of the critical element;
• and
• using the dynamic stress time history to perform a fatigue analysis on the critical element to identify an area of fatigue within the structure.