Ultimate tensile strength, definition

By definition, a brittle material does not fail in shear failure oeeurs when the largest prineipal stress reaehes the ultimate tensile strength, Su. Where the ultimate eompressive strength, Su, and Su of brittle material are approximately the same, the Maximum Normal Stress Theory applies (Edwards and MeKee, 1991 Norton, 1996). The probabilistie failure eriterion is essentially the same as equation 4.55. 

Tensile properties of the HDPE/RET blend are shown in Table 8.2. The HDPE 100/0 carbon-fibre composite showed complete linear stress-strain behaviour up to its ultimate tensile strength and fracture at 10.3% strain. No definitive fracture was seen in the HDPE blends. This is due to the interfacial de-bonding between the constituents within the polymer. The apparent loss of cohesive strength of the matrix material resulted in fibre pull-out and interlaminar slip between the carbon-fibre plies. 

The maximum in the curve denotes the stress at yield av and the elongation at yield v. The end of the curve denotes the failure of the material, which is characterized by the tensile strength a and the ultimate strain or elon gation to break. These values are determined from a stress-strain curve while the actual experimental values are generally reported as load-deformation curves. Thus (he experimental curves require a transformation of scales to obtain the desired stress-strain curves. This is accomplished by the following definitions. For tensile tests ... 

The static failure theory for brittle materials has historically been the Coulomb-Mohr failure theory. A simple definition of a brittle material is that the ultimate compressive strength is greater than the tensile strength, >5 and the yield strengths are approximately eqnal to the nltimate strengths in tension and compression, = S and Cast iron, rock, and concrete are typical materials that are analyzed by... 

Ultimate strength n. The maximum nominal stress a material can withstand when subjected to an applied tensile, compressive, or shear load. If the mode of loading is not specified, it is assumed to be tensile. In materials that exhibit a definite yield strength, ultimate strength will usually mean the nominal stress at break, which can be less than the maximum. Shah V (1998) Handbook of plastics testing technology. John Wiley and Sons, New York. 

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