Tension damage

In the case of the fibrous laminate not much work has been done, but it has been observed that a significant loss of stiffness in boron—aluminum laminate occurs when cycled in tension—tension (43,44). Also, in a manner similar to that in the laminated PMCs, the ply stacking sequence affects the fatigue behavior. For example, 90° surface pHes in a 90°/0° sequence develop damage more rapidly than 0° pHes. In the case of laminates made out of metallic sheets, eg, stainless steel and aluminum, further enhanced resistance against fatigue crack propagation than either one of the components in isolation has been observed (45). 

It is critical that surface treatment conditions be optimized to composite properties since overtreatment as well as undertreatment will degrade composite properties. Typically composite interlaminar shear strength (ILSS), in-plane shear, and transverse tension ate used to assess the effectiveness of surface treatment. More recently damage tolerance properties such as edge delamination strength, open hole compression, and compression after impact have become more important in evaluating the toughness of composite parts. 

Compare the deflection force applied with the values in the detection Tables 58.4 and 58.5. A force between the value shown and 1.5 times (1.5x) the value shown should be satisfactory. A force below this value indicates an under-tensioned drive, which may result in slippage. A force above the tension value indicates an over-tensioned drive, which may result in belt and drive damage. 

These changes occur during what is referred to as the run-in period. Once run-in, the slack on the new belts must be taken up to eliminate slippage, burning, or other irreparable damage. The following are common sense rules of V-belt tensioning ... 

The drying protoplast will be subjected to tension as the result of volume contraction and its adherence to the cell wall. Early observations (Steinbrick, 1900) on desiccation tolerant species showed that the protoplasm does not separate from the wall, but rather that it folds and cavities develop in the wall. Where there are thick-walled cells, localised separation of the plasmalemma from the wall may occur. It seems unlikely, however, that rupture of the plasmalemma normally occurs during desiccation. A more subtle form of membrane damage may arise from dehydration-induced conformational changes. Certainly it is relatively easy to demonstrate that dehydrated membranes exhibit a loss of functional integrity... 

It is known that the endothelial cells lining the capillary bed are markedly damaged during hyperoxic exposure. However, it is not at present known whether this damage is due to free-radical-induced injury of the endothelial cells or whether endothelial cells are simply responding to the diminished blood flow produced by the severe vasoconstriction. The theoretical basis for free-radical involvement is sound and it has been proposed that low oxygen tensions (hypoxia) followed by periods of reoxygenation are the most likely explanation for the disorder (Kelly, 1993). 

Neuropathic and functional pain is often described in terms of chronic pain. Neuropathic pain (e.g., postherpetic neuralgia, diabetic neuropathy) is a result of nerve damage, but functional pain (e.g., fibromyalgia, irritable bowel syndrome, tension-type headache) refers to abnormal operation of the nervous system. Pain circuits may rewire themselves and produce spontaneous nerve stimulation. 

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