Stressing, repeated

Elastic Properties. The abiUty of a fiber to deform under below-mpture loads and to return to its original configuration or dimension upon load removal is an important performance criterion. Permanent deformation may be as detrimental as actual breakage, rendering a product inadequate for further use. Thus, the repeated stress or strain characteristics are of significance in predicting or evaluating functional properties. 

Under cyclic or repeated stress conditions, rupture of protective oxide films that prevent corrosion takes place at a greater rate than that at which new protec tive films can be formed. Such a situation frequently resiilts in formation of anodic areas at the points of rupture these produce pits that serve as stress-concentration points for the origin or cracks that cause ultimate failure. 

More formally if a component or structure is subjected to repeated stress cycles, like the loading on the connecting rod of a petrol engine or on the wings of an aircraft - it may... 

Effects of Water Hammer. Water hammer has a tremendous and dangerous force that can collapse floats and thermostatic elements, overstress gauges, bend mechanisms, crack trap bodies, rupture fittings and heat exchange equipment, and even expand piping. Over a period of time, this repeated stress on the pipe will weaken it to the point of rupture. 

There is one further point that is worth mentioning in connection with the random variable concept. We have repeatedly stressed the fact that the theory of random processes is primarily concerned with averages of time functions and not with their detailed structure. The same comment applies to random variables. The distribution function of a random variable (or perhaps some other less complete information about averages) is the quantity of interest not its functional form. The functional form of the random variable is only of interest insofar as it enables us to derive its distribution function from the known distribution function of the underlying time function X(t). It is the relationship between averages of various time functions that is of interest and not the detailed relationship between the time functions themselves. 

Corrosion Fatigue Corrosion fatigue is a reduction by corrosion of the abihty of a metal to withstand cyclic or repeated stresses. The surface of the metal plays an important role in this form of damage, as it will be the most highly stressed and at the same time subject to attack by the corrosive media. Corrosion of the metal surface will lower fatigue resistance, and stressing of the surface will tend to accelerate corrosion. 

Yet, the effect of repeated stress on the hippocampus is reversible if the stress is terminated after 3 weeks in rats, and it is best referred to as adaptive plasticity) since other brain areas, such as the amygdala, show a growth response to repeated stress [38]. 

The service life of a product can be governed by many factors. These include fatigue failure under repeated stressing, excessive creep or stress relaxation, excessive change in stiffness due to thermal ageing, and excessive change in a physical property due to the action of chemicals. 

As has been repeatedly stressed in this review, all solid surfaces are rough. Let the irregular line in Fig. 26 represent the profile of a vapor — solid interface, greatly enlarged. An atom in position A is almost surrounded by the gas phase consequently,... 

As repeatedly stressed, the doping processes imply the diffusion of electrolyte counterions to compensate for the electric charge assumed by the polymeric chain and thus polymers are expected to experience changes of mass upon doping. Consequently, by monitoring these changes it is possible to control the nature and the extent of the doping processes. 

Stress results in alterations in behavior and physiology that can be either adaptive or maladaptive. Although mice deficient in the calcium-stimulated adenylyl cyclase type VIII (ACS) exhibit indices of anxiety comparable with that of wildtype mice at baseline, ACS KO mice do not show normal increases in behavioral features of anxiety when subjected to repeated stress such as repetitive or post-restraint stress testing in the elevated plus maze test (Schaefer et al. 2000). Although these findings suggest a role for ACS in the modulation of anxiety, the mechanism by which ACS deficiency results in impaired stress-... 

Dhabhar, F.S., McFwen, B.S., and Spencer, R.L. (1997) Adaptation to prolonged or repeated stress—comparison between rat strains showing intrinsic differences in reactivity to acute stress. Neuroendocrinology 65 360—368. 

Imperato A, Cabib S, Pughsi-Allegra S Repeated stressful experiences differently affect the time-dependent responses of the mesolimbic dopamine system to the stressor. Brain Res 601 333-336, 1993... 

Figure 5.40 Variation of stress with time that accounts for fatigue failure by (a) a reversed stress cycle and (b) a repeated stress cycle. Reprinted, by permission, from W. Callister, Materials Science and Engineering An Introduction, 5th ed., p. 210. Copyright 2000 by John WUey Sons, Inc.

Imperato, Assunta, Luciano Angelucci, Paola Casolini, Alessandro Zocchi, and Stefano Puglisi-AHegra. 1992a. "Repeated Stressful Experiences Differently Affect Limbic Dopamine Release During and Following Stress," Brain Research 577 194-99. 

Tyres are very definitely fatigued during use and, as mentioned for fabric/rubber adhesion above, it is very important to carry out dynamic tests to assess bond efficiency. Methods have not apparently been standardised but a variety of procedures have been reported71 79 Some workers have used the same or a similar test piece as in static tests and applied a cyclic tensile stress or strain, whilst others have used some form of fatigue tester operating in compression/shear to repeatedly stress or strain cord/rubber composite, or even to flex samples in the form of a belt. Khromov and Lazareva80 describe a method using test pieces cut from tyres. 

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