Uniform drying causes a quasi-two-dimensional cellular crack pattern in a thin layer of paste. In our previous research, we found that such cracks are created in a capillary state, and that the growth speed is determined by the rate of increase in tension in the layer, rather than by the magnitude of the tension itself. In this paper, we present a theoretical investigation of the effects of inc...

Although fatigue damage in bone induced by cyclic loading has been recognized as a problem of clinical significance, few fracture mechanics based studies have investigated how incipient cracks grow by fatigue in this material. In the present study, in vitro cyclic fatigue experiments were performed in order to quantify fatigue-crack growth behavior in human cortical bone. Crack-growth rates spa...

In this paper, we’ll answer several abstract, formal questions about the nature of crack growth and nucleation. Bringing a field theory point of view to fracture illuminates things in what I hope will be an entertaining way. Formally, what is the crack nucleation rate? Fracture is an instability of elastic theory under tension. For thermally nucleated cracks, there is an analogy with supercoole...

In the present study, plasticity induced crack closure (PICC) concept and three dimensional (3D) finite element methods (FEM) are used to study the effect of compressive residual stress field on the fatigue crack growth from a hole. To investigate the effect of compressive residual stress on crack opening levels and crack shape evolution, Carlson’s experiments were simulated. Crack shape evolut...

Due to cost and time limitations, experiments for fatigue crack growth are only feasible below certain cycle numbers. In this paper, it is investigated whether or not fatigue crack growth laws allow for an extrapolation of the statistics of the cycle number to reach a certain crack length from limited experimental data, and hence reduce costs.

The effects of anisotropy during mixed mode fatigue crack growth were studied in single crystal 316L stainless steel. An anisotropic least-squares regression algorithm using displacements from digital image correlation was developed to find the effective stress intensity factors, KI and KII, and the T-stress. Crack tip plastic zones were determined using an anisotropic yield criterion. Strains ...

The mechanisms of fatigue-crack propagation are examined with particular emphasis on the similarities and differences between cyclic crack growth in ductile materials, such as metals, and corresponding behavior in brittle materials, such as intermetallics and ceramics. This is achieved by considering the process of fatiguecrack growth as a mutual competition between intrinsic mechanisms of crac...

ÐTransient cyclic fatigue-crack growth behavior following variable-amplitude loading sequences has been investigated in a hot-pressed, monolithic Si3N4 ceramic (NTK EC-141), for which fracture toughness (resistance-curve) and cyclic fatigue properties are well characterized. Following rapid changes in the applied stress-intensity range, DK, during both low-high and high-low block-loading sequen...

Fatigue-crack-growth tests were conducted on compact, C(T), specimens made of D16Cz (clad) aluminum alloy under constant-amplitude loading, a single spike overload, and simulated aircraft spectrum loading. Constant-amplitude tests were conducted to generate crack-growth-rate data from threshold to near fracture over a wide range of stress ratios (R = Pmin/Pmax = 0.1–0.75) using the new compress...

Crack-growth experiments in human dentin have been performed in situ in an environmental scanning electron microscope to measure, for the first time, the crack-growth resistance curve (R-curve) for clinically relevant (<250 microm) crack extensions and to simultaneously identify the salient toughening mechanisms. "Young" dentin from donors 19-30 years in age and "aged" dentin from donors 40-70 ...