Residual clamping stress

Fig 3.8 shows the interface shear bond strength, tb, determined from Eq. (3.7), which is not a material constant but varies substantially with embedded fiber length, L. However, to evaluate all the relevant interface properties properly, which include the interface fracture toughness, Gic, the coefficient of friction, p, and the residual clamping stress, qo, it is necessary to obtain experimental results for a full range of L and plot these characteristic fiber stresses as a function of L. More details of the... 

The normalized FAS and IFSS are shown in Fig. 4.17. Both the FAS and IFSS distributions are higher for larger values of residual clamping stress, go, (in absolute terms) for a given fiber length. Varying the coefficient of friction, p, would have similar effects on the stress distributions. The predominant effect of differential Poisson contraction between the fiber and matrix is obvious, particularly in Fig. 4.17(b), where the IFSS values at the fiber ends are several-fold the values obtained in the center. 

Fig. 4.17. Distribution of (a) normalized fiber axial stress, crf/o, and (b) normalized interface shear stress, T /(7, along the fiber axis, z/a, at a given applied stress for different residual clamping stresses 90 =-7,-10 and-13 MPa, After Kim et al. (1993b).

The small diameter of the incident beam from a stress camera or a Fastress unit is an advantage when one wishes to measure stress variations from point to point on a surface, as in the region near a weld. The stress distribution shown in Fig. 16-16, determined by a photographic method, simulates the residual stresses due to spot welding. The specimen was a steel strip 10 x 3 x inch (25 x 8 x 0.6 cm). A circular area of about I inch (1 cm) diameter, whose size is indicated on the graph, was heated locally to about 700°C for a few seconds by clamping the strip at its center between the two electrodes... 

Most stress corrosion service failures occur from the influence of residual stresses. These arise during component manufacture, and plant assembly, including welding. In laboratory work the stress is usually applied externally since it is then much easier to control and measure. The oldest and simplest test is to measure how long a specimen takes to break — the time-to-failure, tf. Typical specimens might be loaded in tension and surrounded by the corrodent or bent into a U, clamped and then immersed. Typically, the value t varies as shown in Figure 1. Two points can be made. First, the tf changes less markedly at stresses above the 0.1X proof stress than below it. Secondly, it is not always clear whether a threshold stress exists below which stress corrosion failures will not occur. This is of obvious importcuice but it has proved a... 

This also includes the elimination of unknown residual stresses (and internal stresses) by a plate extensor. A plate extensor consists of units of movable and stationary clamping devices. Both clamping devices are equipped with gripping devices for holding the ends of the plates. 

Wan KT, Mai YW (1995) Fracture mechanics of a shaft-loaded blister of thin flexible membrane on rigid substrate. Int J Fract 74(2) 181 Wan KT, Guo S, Dillard DA (2003) A theoretical and numerical study of a thin clamped circular film under an external load in the presence of a tensile residual stress. Thin Solid Films 425(1-2) 150... 

More uniform shrinkage, lower residual stresses, significantly less distortion Reduced clamping force Implementation of long flow paths Better surface in comparison to foamed parts Simpler mould construction possible in some cases Possibility of integrating thick and thin areas... 

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