Analysis On Damage And Fatigue Of Functionally Graded Material

With the advancement of technology, the functionally graded materials havedrawn more and more attention for its combining the advantages of two or morematerials. In the practice, the functionally graded materials are mainly used as thethermal-proof coating material; however, its structure is facing problems of loadin gin the complicated working circumstance, and the duty-cycle loading caused by thevibration of the machine makes the material fatigue become the main damage.Currently, since there are few specific studies on the damage problem of thefunctionally graded materials caused by transverse load and the duration problemout of the cyclic transverse load, the author will analyze the fatigue and damage offunctionally graded materials according to the damage theory in this essay.Finite element analysis software is commonly used to imitate the functionallygraded materials to analyze the different load problems. An UMAT subroutine hasbeen edited to set up a damage constitutive model which is right for this paper.When the author defines the property of the graded materials, the materialparameter S relative to the temperature is added in a damage evolution equation. Bystudying the reference books, it’s found that with the same temperature theparameter S would change according to different materials, but it has been usuallysimplified as a stable data. In this paper, considering of practical significance, theparameter is defined as a function similar to the form of the modulus of elasticity.By using the UMAT subroutine to compare the result of analyzing theelasticity of the unit metal material with the one of the Finite element host program,the paper proves its feasibility and effectiveness. With the definition of the integralmodel of the functionally graded materials, the parameter S is able to be expressedat the same mixing rate with modulus of elasticity, then its elasticity is studied inthe finite element subroutine to compare with the constant of the parameter S. Atthe end of the essay, different index gradients of material mixing rate are chosen forthe analysis of damage extent and main damage area of materials in order to providethe reference when it comes to the practical operation of the project as well as thedesign of graded materials.