Residual stress, definition

Fig. 1. (a) Schematic diagram showing definition of case hardening and of case depth where (—) is the diameter (b) residual stress across the radius of a... 

Figure 2.27 Definition of the reference axes and the direction of measurement in XRD residual-stress analysis...

This is the equation for the maximum reversible work of adhesion for two solids in contact and is the counterpart of Equation 4 for the case of a liquid in contact with a solid. Our definition of the final solid-solid state as an equilibrium state implies that there are no residual stresses in either solid produced by the solidification of L2. 

Another model, which has been derived from end milling of aluminum, explains the typical gradient as a result of pure mechanical influence, as in the investigated process, the temperature development could be neglected (de Le6n 2009). This model allows a parametrization of the curve and a definition of typical values, e.g., surface residual stress (7surf, maximum residual stress ffmax, depth of maximum residual stress (Tmax, or depth of stress absence (Fig. 11) (de Le6n 2009). 

Hardness has been generally defined by Martens in about 1900 as the resistance of a material able to counter the penetration of another harder material. Sometimes, also in polymer testing, the older definition of hardness as a scratch resistance first introduced by Mohs in 1820 is used. The scratch resistance to be determined in the form of the scratch hardness applying depth-sensing approaches or the Buchholz hardness, for example, is used for characterising (1) elastic and plastic deformations, (2) adhesive failure and crack formation, (3) abrasion and (4) recovery of strains and residual stresses of paintings, coatings or surface modification etc. 

The die is rrsrrally between 0.5 m and 1.5 m long. The polymeric matrix is cured at temperatures that mostly range from 90"C to 180°C, and depend on the resin system used (among other factors). The proper definition of temperatures at different locations along the die helps to optimise curing conditions and prevents thermal residual stresses from developing. 

The total strain in the system is not compatible, which is the feature that gives rise to residual stress. The incompatibihty is readily handled explicitly, however, so that a compatible difference strain can be defined. Without loss of generality, the midplane of the substrate is chosen as the reference plane for definition of the mismatch distribution em(2). Any strain of the material in either the film or the substrate with respect to the reference plane at the reference temperature is included in em( )- The equi-biaxial difference strain eaif(-2) is simply... 

Stress Stress definition Sources of stress Mean stress, maximum stress, minimum stress, constant load/constant strain, strain rate, plane stress/plane strain, modes 1, II, III, biaxial, cyclic frequency, wave shape Intentional, residual, produced by reacted products, thermal cycling... 

There are spedal considerations to define the test pressure for prestressed pressure vessels. The normal reason of a pressure test is to demonstrate the integrity of the vessel and to induce compression residual stresses in the area of notches. Prestressed high-pressure vessels have mostly a simple design without notches. The test pressure should be limited, in order not to change the prestressed status of the pressure vessel. The determinations in /3/ for test pressure definition are practicable. Additional nondestructive test procedure should be avoided. 

The uncertainty in the definition of the system. Parameters such as the initial material conditions (e.g., thermally induced grain boundary sensitization, coolant purity, corrosion potential) are important, but the most significant uncertainty rests with the definition of the weld residual stress. 

The concentration of thiosulfate in the electrolyte was shown to be the primary factor determining the sulfur content of deposits and consequently their residual stress and mechanical properties [57]. The addition of thallium as a grain reflner was shown to reduce the deposits residual stress to almost zero, at least for a definite set of operative conditions a temperature of 50°C and c.d. within the range 0.4-0.6 A dm [30]. This electrolyte was found to be adequate for interconnection purposes even in the absence of additives [95]. 

The second and preferred method is to apply appropriate statistical analysis to the dataset, based on linear regression. Both EU and USFDA authorities assume log-linear decline of residue concentrations and apply least-squares regression to derive the fitted depletion line. Then the one-sided upper tolerance limit (95% in EU and 99% in USA) with a 95% confidence level is computed. The WhT is the time when this upper one-sided 95% tolerance limit for the residue is below the MRL with 95% confidence. In other words, this definition of the WhT says that at least 95% of the population in EU (or 99% in USA) is covered in an average of 95% of cases. It should be stressed that the nominal statistical risk that is fixed by regulatory authorities should be viewed as a statistical protection of farmers who actually observe the WhT and not a supplementary safety factor to protect the consumer even if consumers indirectly benefit from this rather conservative statistical approach. 

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