Fracture fatigue

Measurement of the fatigue fractures depth during bench tests for crack resistance. 

Stress or fatigue fractures are very painful. Most often symptoms occur after athletic activity or physical exertion. Gradually pain worsens and becomes more constant. Stress fractures do not show up on standard x-rays. A bone scan maybe used to confirm the diagnosis. Stress fractures usually occur in the weight-bearing bones of the lower leg and foot. Stress fractures of the tibia account for half of all stress fractures, resulting mostly from athletic activity. These stress fractures are often mistaken for shin splints. In addition to the tibia, the fibula and other small bones of the foot are prone to stress fractures. 

Elastic ar plastic deflectian Elastic ar plastic deflection Fracture Fatigue fracture Creep... 

Slides Fatigue fracture surfaces components failed by fatigue, e.g. gear teeth, half-... 

Moulded plastics will also have crack initiation sites created by moulding defects such as weld lines, gates, etc and by filler particles such as pigments, stabilisers, etc. And, of course, stress concentrations caused by sharp geometrical discontinuities will be a major source of fatigue cracks. Fig. 2.72 shows a typical fatigue fracture in which the crack has propagated from a surface flaw. 

Figure 4-71. Fatigue fractures in outer wires caused by the formation of martensite [11].

The mechanisms by which polymers undergo degradation in the human body are not yet completely understood. Examples of breakdown of these materials are illustrated by the embrittlement and excessive wear of polyester sockets exposed to the mechanical, biochemical and thermal stresses of the physiological milieu, as well as by the fatigue fractures, excessive wear and additional cross-linking (embrittlement) that have been observed in polyethylene sockets. 

Figure 13.10 Schematic representation of the most general type of fatigue fracture of a nylon 6,6 fiber [26], From The fatigue of synthetic polymeric fibers, Brunsell, A. R. and Hearle, J. W. S., J. Appl. Polym. Sci., 18, 267 (1974), copyright (1974 John Wiley Sons, Inc.). Reprinted by permission of John Wiley Sons, Inc.

Russell, A.J. and Street, K.N. (1987). The effect of matrix toughness on delamination static and fatigue fracture under mode I and II shear loading of graphite fiber composites. In Toughened Composites. ASTM STP 937 (N.J. Johnston ed.). ASTM, Philadelphia, PA, pp. 257-294. 

Mechanical Properties Stress-strain, Elasticity, DuctiUty Fatigue, Fracture, Creep Viscoelasticity, Elastomers Laminates Sutures, Bone, Teeth... 

It was shown that, after cyclic tensile fatigue fracture at room temperature in a narrow region within a couple of micrometers of each side of the fractured surfaces, the morphology of grain elongation appeared to be general. Viewed... 

In a shear field, a particle experiences rotation because of velocity differences in addition to the load created by the shear forces. This produces cyclical loading. The cyclical application of a load promotes dispersion, since solid particles often undergo fatigue fracture [1],... 

The fatigue fracture surface of a failed crankshaft and failed rod bolt in a diesel engine are shown in Figures 2.18 and 2.19, respectively. 

Figure 2.18 Fatigue fracture surface appearance of a failed crankshaft, showing beach marks on the lower part. The origin of the primary fracture is indicated by the arrow. (Reprinted with permission from ASM International. All rights reserved www.asminternational.org)...

Percussion is a repetitive solid body impact, such as experienced by print hammers in high-speed electromechanical applications and high asperities of the surfaces in a gas bearing. Repeated impacts result in progressive loss of solid material. Percussive wear occurs by hybrid wear mechanisms, which combine several of the following mechanisms adhesive, abrasive, surface fatigue, fracture, and tribochemical wear.75... 

Speidel, M.O., Stress Corrosion Cracking and Corrosion Fatigue - Fracture Mechanics, in Corrosion in Power Generating Equipment, M.O. Speidel, A. Atrens (eds.), Plenum Press, NY, pp. 85-132, 1984. 

Figure 7.43 Fatigue fracture face, showing crack growth direction. (Reproduced from COM 1999 and 2005 with permission from the Metallurgy Society of CIM)...

Figure 7.46 Drive shaft fatigue fracture face, showing initiation point (arrow) and foreign keyway material (K)...

Approaches to characterizing the creep-fatigue fracture of ceramic composites. 

Differences in the macroscopic and microscopic fatigue fracture behavior of ceramic composites under static and cyclic loading at high temperatures. 

In this case, crack growth is essentially a time-dependent process and there is no unique method available for characterizing fatigue fracture under extensive... 

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