Search results
Results from the WOW.Com Content Network
An idealized uniaxial stress-strain curve showing elastic and plastic deformation regimes for the deformation theory of plasticity There are several mathematical descriptions of plasticity. [ 12 ] One is deformation theory (see e.g. Hooke's law ) where the Cauchy stress tensor (of order d-1 in d dimensions) is a function of the strain tensor.
The yield function is often expressed as an equation consisting of some invariant of stress and a model for the yield stress (or plastic flow stress). An example is von Mises or plasticity. In those situations the plastic strain rate is calculated in the same manner as in rate-independent plasticity.
The strain can be decomposed into a recoverable elastic strain (ε e) and an inelastic strain (ε p). The stress at initial yield is σ 0 . Work hardening , also known as strain hardening , is the process by which a material's load-bearing capacity (strength) increases during plastic (permanent) deformation.
An oscillating force is applied to a polymer sample and the sample’s response is recorded. DMA documents the lag between force applied and deformation recovery in the sample. Viscoelastic samples exhibit a sinusoidal modulus called the dynamic modulus. Both energy recovered and lost are considered during each deformation and described ...
Dynamic mechanical analysis (abbreviated DMA) is a technique used to study and characterize materials.It is most useful for studying the viscoelastic behavior of polymers.A sinusoidal stress is applied and the strain in the material is measured, allowing one to determine the complex modulus.
Experimentally, stress relaxation is determined by step strain experiments, i.e. by applying a sudden one-time strain and measuring the build-up and subsequent relaxation of stress in the material (see figure), in either extensional or shear rheology. a) Applied step strain and b) induced stress as functions of time for a viscoelastic material.
The Drucker–Prager yield criterion [1] is a pressure-dependent model for determining whether a material has failed or undergone plastic yielding. The criterion was introduced to deal with the plastic deformation of soils. It and its many variants have been applied to rock, concrete, polymers, foams, and other pressure-dependent materials.
An example of a material with a large plastic deformation range is wet chewing gum, which can be stretched to dozens of times its original length. Under tensile stress, plastic deformation is characterized by a strain hardening region and a necking region and finally, fracture (also called rupture).