Effect of Stress Triaxiality on Yielding of Anisotropic Materials under Plane Stress Condition

The triaxiality of the stress state is known to greatly influence the amount of plastic strain which amaterial may undergo before ductile failure occurs. it is defined as the ratio of hydrostaticpressure, or mean stress, to the von mises equivalent stress. this paper discusses the effects ofstress triaxiality on yielding behavior of anisotropic materials. hill-von mises’s criteria foranisotropic material have been used with triaxiality factor (tf). mathematical model thatcombines the yield stress and anisotropic ratio r (ratio of width strain to thickness strain) alongwith triaxiality have been formulated. this model is considered as an objective function subjectedto inequality constraint. constrained optimization is solved using genetic algorithm. the resultsobtained give the set of principal stresses along with corresponding critical triaxiality which is themaximum value at which the material can sustain without failure. if triaxiality extends furthermore the material will go to plastic deformation and may prone to failure. in this way, the criticaltriaxiality of materials can be determined to avoid fracture and failure of materials. this article isimportant from the industrial application point of view by considering triaxiality as a designparameter while designing the component.