Research On Static And Dynamic Fracture Mechanical Parameters Of Functionally Graded Materials And Finite Element Program Design

Functionally Graded Materials (FGM) is a kind of nonhomogeneous materials, which is being widely used in many fields. The study on the mechanical properties of FGM is becoming a focus in mechanics research, expecially about it’s fracture problems. Stress intensity factor is a important parameter during the fracture process of FGM, it represents the crack tip stress field intensity, therefore, many scholars have launched the research in this area.The main content of this paper is to study the change regularity of stress intensity factor of the crack tip of FGM with the condition of load. As we all know, the material parameter of FGM varies continuously in space, it is very difficult by theoretical analysis; however, the numerical analysis is an effective method. Based on the linear elastic fracture mechanics theory, the author has developed a finite element program for the calculation of the fracture behavior of FGM and checked it by some examples. The first chapter introduces the research history of fracture problems of functionally graded materials and the finite element method; the second chapter introduces the crack tip singular finite element and the formulation of programming process; according to the static and dynamic sequence, the next two chapters introduce some examples; the last chapter is the conclusion and program statements are listed in the appendix. The third chapter is the static calculation, and computing model is a plate and cylinder, the author studied two cases:elastic modulus is exponential function of coordinate and linear function of coordinate, the conclusions are obtained:the stress intensity factor increases with the crack growth in the same load conditions; the stress intensity factor is greater for the crack tip in the stiffer side; when the inclination angle is in the range of 0～90°, the value of KI decreases with the increasing of the angle, and the KII first increased and then decreased. In the fourth chapter, the research object is Al2O3-Ti FGM. By using the same computational model and with the condition of impact load, the author obtains some conclusions as follow:the vibration period of stress intensity factor increases with the increasing of crack length; when the crack parallels to the gradient direction, the peak of the Kdyn/Ksta is at around 2; the greater of the crack angle, the larger of Kdyn/Ksta.