Adhesion stress effects

When reduced wear is associated with the addition of molybdenum disulphide to a lubricating oil, the type of wear is always likely to be adhesive. The effects of molybdenum disulphide in such a case would be a direct reduction in the degree of adhesion by the interpolation of a molybdenum disulphide film, as well as a reduction in the overall stress levels due to lowering of friction. 

Earlier work in this laboratory and others demonstrated in vitro dysfunction of both platelets and leukocytes following application of low-level shear stress (1 4). The effects of mechanical trauma can be attributed to bulk shear stress effects rather than surface-mediated ones, since changing the surface-to-volume ratio by a factor of three did not alter the leukocyte or platelet response to a given shear stress intensity and exposure duration (2). Platelet microaggregate formation and adhesion alterations occurred following shear stress exposure in the range of 150 dyn/cm2 for 2 min, while... 

Lastly, adhesives are used to dissipate stresses that may be generated from thermal excursions, mechanical shock, vibration, or moisture. Specially formulated adhesives are effectively used as underfills for flip-chip devices and ball-grid-array packages to compensate for mismatches of expansion coefficients among the solder, the silicon chip, and the ceramic or plastic-laminate substrate. Low-stress adhesives are also used to attach fragile devices such glass diodes and to dampen stresses due to vibration. 

Swanson DW, Enlow LR. Stress Effects of Epoxy Adhesives on Ceramic Substrates and Magnetics. Proc. IMAPS Conf. Oct. 1999. 

Table 6.1 Effect of modulus, expansion coefficient, and temperature on adhesive stress ... 

Table 6.1. Effect of Modulus, Expansion Coefficient, and Temperature on Adhesive Stress ... 

This chapter assesses the effect of miniaturizing on adhesion issues. First, it is demonstrated that adhesion stress improves as bodies get smaller. But there is a limit of elasticity which has a strong influence. The ultimate adhesion experiment is with a single atom. This experiment is on the point of being carried out. It has important implications for the future of adhesion science. 

It is evident that a large number of parameters are involved in the fabrication and testing of bulk adhesive specimens and adhesive joints these must be controlled if meaningful experimental data are to be obtained. Joint tests evaluate not only the mechanical properties of the adhesive, but also the degree of adhesion and the effectiveness of surface treatments. The standard test procedures listed by ASTM, BSI, DIN and other official bodies are essentially for testing adhesives and surface treatments rather than joints (e.g. Table 4.3). Unfortunately, most of these tests consist of joints in which the adhesive stresses are far from uniform. The designer and the researcher therefore have to select appropriate tests, and to know what the results mean in terms of their own particular investigations and applications. 

Adams and Wake (reference 5.17) considered the adhesive stresses and adherend direct stresses acting across the width of an adhesive joint. They included the adherend shear stresses but neglected the effects of bending, thus excluding peel stresses. They used a... 

Tsai M Y and Morton J (1995), The effect of a spew fillet on adhesive stress distributions in laminated composite single-lap joints . Compos Struct, 32(1 ), 123-131. 

An analysis of adhesive stresses in bonded joints which included the effects of load eccentricity was first performed by Goland and Reissner(3) in 1944 under the following assumptions ... 

To demonstrate the T-stress effect and to understand other factors affecting crack path selection, the authors and their coworkers [13,25,31,32] carried out a series of experimental studies with adhesively bonded joints to determine the effects of T-stress, specimen geometry, external loading conditions, surface pretreatment. 

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