Paris' law

About: Paris' law is a research topic. Over the lifetime, 13815 publications have been published within this topic receiving 224818 citations. The topic is also known as: Paris-Erdogan law.

On the theoretical modeling of fatigue crack growth

Abstract: Although fatigue is by far the most common mode of failure of structural materials, mechanistic understanding is still lacking. For example, the fundamental Paris law which relates the crack growth rate to stress-intensity factor range is still phenomenological and no reliable mechanistic model has been established for a given material or class of materials despite numerous investigations over a half a century. This work is an attempt to theoretically model fatigue crack propagation induced by alternating crack-tip plastic blunting and re-sharpening in the mid-range of growth rates on the basis of inputs from experiments that measure macroscopic material behavior, e.g., response to uniaxial cycling loading. In particular, we attempt to predict Paris law behavior by accounting for the material constitutive behavior in response to cyclic loading by modeling crack advance solely in terms of the underlying plastic dissipation. We obtain the steady-state condition for crack growth based on plastic dissipation, numerically using finite element analysis, which involves a methodology to address plastic closure upon unloading. For a given stress-intensity range, we calculate the crack propagation rate from the steady-state condition through each cycle of loading and unloading of a cracked compact-tension specimen, without resorting to any specific criterion for crack advance.

Fatigue Life Prediction of Structures

Abstract: Fatigue life prediction problems are discussed from the viewpoint of probabilistic mechanics of solids and structures. A survey of random factors in damage and fracture is presented with a special emphasis on the statistical scatter of mechanical properties of materials and/or structural components. A model of fatigue crack initiation is discussed based on the concepts of continuum damage mechanics as well as the assumption that fatigue crack nuclei form Poissonian sets distributed in a body. To describe macroscopic fatigue crack propagation, the theory proposed by author that takes into account the interaction between the microdamage accumulation along the crack trajectories and the global balance of forces, energy, etc. in the cracked body under loading is used. Various approaches to the modeling of material property fields are considered, and the influence of random factors from different sources on fatigue life is studied by means of numerical simulation. Discussion of alternative probabilistic approaches to modeling of fatigue damage is presented.

Fatigue failure characteristics of lead zirconate titanate piezoelectric ceramics

Abstract: Mechanical properties and fatigue failure characteristics of lead zirconate titanate piezoelectric ceramic (PZT) have been investigated. Bending and fatigue strengths of PZT ceramic are directly attributed to the electrode status. Material hardening occurs in the PZT ceramic during the cyclic loading, which is influenced by domain switching occurring anywhere in the grains. The domain structure is clearly detected by electron back scatter diffraction analysis and etching techniques. It also appears that the poling direction causes the change of failure characteristics due to different domain and domain wall orientation. The domain orientation changes alternately from domain to domain by 90°. Moreover, the domain wall orientation is well regulated in the grains perpendicular to the poling direction. An acceleration of fatigue crack growth occurs as the crack propagates along the domain wall.