Defect, stress-related

The average wall stress and the local stress near defects are related through the linear elastic stress intensity factor (K). The magnitude of the local stress is proportional to the stress intensity factor, K, according to the following relationship ... 

The maximum line speed of drying and operating conditions of dryer are often restricted by the onset of defects. The drying related defects could be classified according to the cause of defects - stress induced defects, surface tension driven defects, defects caused by air motion. 

The slip approach defines the onset of surface defects as related to a slippage of the polymer at the die wall. Accordingly, the zero-wall velocity concept, as used in the constitutive approach, does not apply. Many attempts have been made to experimentally measure the velocity at the wall, however, with mixed success. Still, theories have been developed which support a shear-dependent slippage at a polymer/ solid interface. Slippage may be understood as the buildup of a layer of polymer molecules bonded to the die surface, which undergo a coil-stretch transition under the shear stress. In light of this understanding, the microscopic shp layer development may be in line with the possible formation of a macroscopic surface layer as a consequence of a many... 

The two most widely accepted mechanisms for this phenomenon are defect inclusion in the crystalline phase and surface stresses related to reduced lamellar thickness [13,31,33]. In the second mechanism, defects are mostly rejected from the crystals, but preferentially reside in the interfacial layer, thereby exerting stress on the crystal surface [31,34,35]. As the counit concentration increases, the lamellar crystal becomes thinner. This leads to an increase in the crystal s surface-to-volume ratio, which in turn amplifies the magnitude of this stress-induced unit cell deformation. 

Aziz M J (1997), Thermodynamics of diffusion under pressure and stress relation to point defect mechanisms , Appl Phys Lett, 70(21), 2810-2812. 

The failure rate changes over the lifetime of a population of devices. An example of a failure-rate vs product-life curve is shown in Figure 9 where only three basic causes of failure are present. The quaUty-, stress-, and wearout-related failure rates sum to produce the overall failure rate over product life. The initial decreasing failure rate is termed infant mortaUty and is due to the early failure of substandard products. Latent material defects, poor assembly methods, and poor quaUty control can contribute to an initial high failure rate. A short period of in-plant product testing, termed bum-in, is used by manufacturers to eliminate these early failures from the consumer market. 

Numerous resistance measurements have been carried out under high-pressure shock compression [79D01]. Most of the work has been motivated by the desire to develop stress gauges to measure pressures in shock-compressed materials. Other measurements were undertaken to determine critical pressures to induce phase transformations. Although most of the work is not carried out in sufficient detail to relate resistance observations to defect characterizations, excess resistance at given shock pressures is observed in every case compared to comparably loaded static pressure observations. The presence of residual resistance for times after the loading is removed provides explicit evidence for irreversible changes in resistance due to defects. 

Inglis extended this idea of stress concentrations at defects and derived an equation relating the maximum stress to the size and shape of the defect ... 

IR absorption and Raman spectroscopy are also well suited to the application of uniaxial stress techniques. Stress-induced splittings of the vibrational bands give information about the symmetry of the defect. In favorable cases, it has been possible to determine the kinetics of the H motion between equivalent sites around an impurity from a study of the alignment of the H-related complexes that can be induced by stress. 

Here, the vibrational spectroscopy of H-related complexes in Si, with and without stress, will be reviewed. We will find that in spite of the recent progress made toward understanding defect-H local modes in semiconductors, there is still much work to be done. 

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