Compression and shear

The viscoelastic behaviour of rubbers is not linear stress is not proportional to strain, particularly at high strains. The non-linearity is more pronounced in tension or compression than in shear. The result in practice is that dynamic stiffness and moduli are strain dependent and the hysteresis loop will not be a perfect ellipse. If the strain in the test piece is not uniform, it is necessary to apply a shape factor in the same manner as for static tests. This is usually the case in compression and even in shear there may be bending in addition to pure shear. Relationships for shear, compression and tension taking these factors into account have been given by Payne3 and Davey and Payne4 but, because the relationships between dynamic stiffness and the basic moduli may be complex and only approximate, it may be preferable for many engineering applications to work in stiffness, particularly if products are tested. 

Friedrich, A.J. Size reduction overview Shear, compression, and impact. Powder and Bulk Engineering, June 2001, 19-25. 

Lukkarinen and Kaski [316] have studied the mechanical properties of ER fluids by simulating perfectly ordered structures (single chains, columns of flve chains and bet crystal) under shearing, compression and elongation. They show that ER systems under compressive loading transfer a much larger force from one plane to the other than by shearing. 

Continuous fiber Gr/Al MMCs (Fig. 1) are known to have high specific tensile strength and stiffoess in the direction of the fiber axis. Limitations of shear, compression, and transverse strengths of the MMCs, however, have restricted their use [3]. Particulate Gr/Al MMCs have also been developed for potential use in tribological applications due to good resistance to wear and seizure [23,24]. 

Hounsfield Tensometer. A compact device, manual or motor driven, which will perform tensile, shear, compression and bend strength tests on ceramics and other materials at forces up to 20kN. (Monsanto pic, Swindon). 

An elastomer is ideal in the vessel environment because it will not corrode. Metal components are protected by being totally encapsulated in an elastomer and then bonded to all-metal surfaces. In examining the load-deflection characteristics of shear, compression, and buckling systems, the one that results in the lowest reaction force generally also produces the lowest-cost structure. Figs 2.13 to 2.15 show six results... 

Additional flexural cracks have appeared in the top cap. It seems that the influence of cracks due to shear compression and plug failure has been minimised. At the equator (marks 115 and 116) a larger plastic zone has been... 

Water absorption will change the mechanical and physical properties of a composite laminate. Matrix-dominated shear, compression and bending modulii, and strength may be reduced, and coefficient of expansion may be increased. Account for these changes in design. 

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