Pressure-shear loading

In most flat-plate impact experiments, the direction of motion of the impacting plate is normal to its surface, such that only a planar compressive shock is introduced into the specimen. Within the last fifteen years, however, techniques have been developed for dynamic pressure-shear loading of specimens (Abou-Sayed et al., 1976 Chhabildas and Swegle, 1980). These involve an oblique impact, as illustrated in Fig. 3.6, in which the impact surface on the... 

Samples are most frequently shock deformed under laboratory conditions utilizing either explosive or gun-launched flyer (driver) plates. Given sufficient lateral extent and assembly thickness, a sample may be shocked in a onedimensional strain manner such that the sample experiences concurrently uniaxial-strain loading and unloading. Based on the reproducibility of projectile launch velocity and impact planarity, convenience of use, and ability to perform controlled oblique impact (such as for pressure-shear studies) guns have become the method of choice for many material equation-of-state and shock-recovery studies [21], [22]. 

Radial pressure is therefore controlled by the effective angle of powder friction be- Typical values range from 40 to 60°, with increases in powder friction leading to a decrease in radial pressure for a given loading. Further, note the contrast with typical fluids that develop an isotropic pressure under load. The radial pressure Or in turn produces a wall shear stress which acts to oppose the applied load Oo, given by ... 

With re-entry vehicles and spaceplanes, the material resistance to extremes of temperature becomes a matter of major concern. When spacecraft dive into the Earth s atmosphere, aerodynamic surfaces are exposed to high thermal and mechanical loads maximum heat fluxes of the order of MW/nr, dynamic pressure, shear stress, acoustic vibrations and material degradation put the vehicles structures to a hard test. Payload and passenger survival is committed to the efficiency of the thermal protection system (TPS) which has to maintain the internal temperature within appropriate limits through various energy dissipating mechanisms. 

Wall stress (1) In a filament-wound pressure vessel, the stress calculated from the pressure or load divided by the entire cross-sectional area of the wall (not just that of the reinforcement). (2) In a fluid flowing through a channel (such as a die, tube, or extruder-screw channel), the shear stress at any channel surface. In the simplest case of a fluid in steady flow through a circular tube of radius R and length L, the wall stress is given by AP-R/2L, where AP is the pressure drop from inlet to outlet. Munson BR, Young DF, Okiishi TH (2005) Fundamentals of fluid mechanics, John Wiley and Sons, New York. 

The load required to deflect the bellows through the 3.5 mm is calculated to be 20 kN, while a pressure differential of 0.4 MPa (4 bar) across the bellows contributes an additional load of 25 kN on the adhesive. This gives a working shear load on the adhesive joints of 45 kN, equivalent to 21 kN/m of joint length of 0.28 MPa of bonded area. 

Shear Adhesion (Creep). The most significant example of creep is a tape gliding down under shearing load. Therefore, most commonly creep is characterized by the time a tape holds under defined shear load (Fig. 13). This often is called holding power or shear adhesion. Further examples of creep are the telescoping of rolls of stretchable pressure-sensitive tapes and the greasy spots occurring on a paper sheet mended by a transparent adhesive tape. 

Condition Temp. CQ Load piston + weigjht (kg) Approximate pressure Shear stress (X 10 ( cn ... 

Besides pressure, shear was also noted to be a major contributor to the problem of pressure ulcer. The purpose of this plenary lecture is to review our current understanding on how epidermal loadings affect the tissues internally, and on the biomechanics of pressure ulcers formation. 

Empirical factor to correlate the undrained shear strength to the cone resistance Bearing capacity factors Mean effective stress Atmospheric pressure Allowable load Measured cone resistance... 

Since creep is considered as a key weaknesses of pressure sensitive adhesives, various specific test methods and standards have been developed to evaluate the creep resistance of pressure sensitive adhesives like, for example, in the European Standard EN 1943 ( Self adhesive tapes-Measurement of static shear adhesion ), FINAT (Federation Internationale des Fabricants et Transformateurs d Adhesives et ThermocoUants sur Papier et autres Supports), test method FTM 8 (Resistance to shear from a standard surface), or the Pressure Sensitive Tape Councils test method PSTC 107 (International Standard for Shear Adhesion of Pressure Sensitive Tape) by either monitoring the time- and load-dependent displacement of an adhesive specimen under shear load or simply recording the time to failure. The result of the so called SAFT-test ( Shear Adhesion Failure Temperature ) indicates the temperature at which a sample that has been subjected to an environment with steadily rising temperature under static shear load has failed. 

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