Failure Under Multiaxial Stresses

The simplified failure envelopes differ little from the concept of yield surfaces in the theory of plasticity. Both the failure envelopes (or surfaces) and the yield surfaces (or envelopes) represent the end of linear elastic behavior under a multiaxial stress state. The limits of linear elastic... 

Some materials might produce a unique failure surface providing measurements could be conducted under first stretch conditions in a state of equilibrium. Tschoegl (110), at this writing, is attempting to produce experimental surfaces by subjecting swollen rubbers to various multiaxial stress states. The swollen condition permits failure measurements at much reduced stress levels, and the time dependence of the material is essentially eliminated. Studies of this type will be extremely useful in establishing the foundations for extended efforts into failure of composite materials. 

ESC is mostly a surface-initiated failure of multiaxially stressed polymers in contact with surface-active substances. These surface-active substances do not cause chemical degradation of the polymer, but rather accelerate the process of macroscopic brittle-crack failure. Crazing and cracking may occur when a polymer under multiaxial stresses is in contact with a medium. A combination of external and/or internal stresses in a component may be involved. 

Braiden,P,M,Failure criteria for WC-Co materials under multiaxial stress states or long term static stresses,In Conf.on Recent Advances in Hardmetal Production,Loughborough, 17-19 Sept.1979, 28-1. 

In a recent attempt to bring an engineering approach to multiaxial failure in solid propellants, Siron and Duerr (92) tested two composite double-base formulations under nine distinct states of stress. The tests included triaxial poker chip, biaxial strip, uniaxial extension, shear, diametral compression, uniaxial compression, and pressurized uniaxial extension at several temperatures and strain rates. The data were reduced in terms of an empirically defined constraint parameter which ranged from —1.0 (hydrostatic compression) to +1.0 (hydrostatic tension). The parameter () is defined in terms of principal stresses and indicates the tensile or compressive nature of the stress field at any point in a structure —i.e.,... 

Qi D, Cheng G. Failure analysis of fiber-reinforced composites under multiaxial cychc stress. Polym Compos 2008 29(8) 922—31. 

This term is normally associated with shorter deeper beams. Failure takes place when the compression zone, after its reduetion in size due to cracking, fails under combined aetion of triaxial eompression and shear stresses. This failure type can happen at principal tensile eraeks. The limitation to this shear compression is that the average compressive stress in the concrete has only been found at failure in pure flexure. As it is based on extreme concrete fibre reaching its limiting strain it is possible that shear failure ean oecur on an inclined plane near the centre of a eompression zone. In the vessel the haunch hinge is under a multiaxial state of stress due to prestressing bonded steel, liner and penetrations. This zone will in that case resist shear compression failure. 

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