Necking (engineering)
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In engineering and materials science, necking is a mode of tensile deformation where relatively large amounts of strain localize disproportionately in a small region of the material. The name originat
The Considère construction for prediction of the onset of necking, expressed as the gradient of the (true) stress-strain curve falling to the true stress, for a material conforming to the Ludwik-Hollomon relationship, with the parameter values shown.
The Considère construction for prediction of the onset of necking, expressed as the point where the gradient of the true stress – nominal strain curve extrapolates back to a nominal strain of -1 at zero stress, for a material conforming to the Ludwik-Hollomon relationship, with the parameter values shown.
A polyethylene sample that has necked under tension
Ultimate tensile strength
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Ultimate tensile strength is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials, the ultimate tensile strength is close to the yield
Necking (engineering)
…identified by visual inspection, it is in many ways the easiest criterion to use to establish the onset of necking. It also corresponds to the “strength” (ultimate tensile stress), at least for metals that do neck (which covers the majority of “engineering” metals). On the other hand, the peak in a nominal stress-strain curve…
Two vises apply tension to a specimen by pulling at it, stretching the specimen until it fractures. The maximum stress it withstands before fracturing is its ultimate tensile strength.
Round bar specimen after tensile stress testing
The "cup" side of the "cup–cone" characteristic failure pattern
Some parts showing the "cup" shape and some showing the "cone" shape