What is kinematic hardening model?

What is kinematic hardening model?

In the theory of plasticity, kinematic hardening is modeled by the motion of the yield surface in the stress space. This is implemented mathematically by the evolution of the shift or backstress tensor β. The backstress tensor β denotes the position of the center of the yield surface in the stress space.

What is Drucker Prager plasticity model?

Existing research works have established that Drucker–Prager (DP) plasticity model is capable of modeling stress–strain behavior of confined concrete. However, accuracy of the model largely depends on adequate evaluation of its parameters that determine the yield criterion, hardening/softening rule and flow rule.

What is the difference between isotropic and kinematic hardening?

As I see,kinematic hardening can model reversible nbehaviour of metals (Bauschinger effect). In isotropic hardening, the yield surface increase in size, but remain the same shape, as a result of plastic straining.

What is isotropic hardening model?

Kinematic Hardening The isotropic model implies that, if the yield strength in tension and compression are. initially the same, i.e. the yield surface is symmetric about the stress axes, they remain. equal as the yield surface develops with plastic strain.

What are the effects of kinematic hardening on yield locus?

It appears that kinematic hardening has an influence on the apparent non- normality of plastic strain-rate direction with respect to the stress path. It is also obvious that kinematic hardening plays a significant role in the shape of the subsequent yield surface and the loss of normality.

What is back stress in kinematic hardening?

In the case of kinematic hardening the size of the initial yield surface remains the same, but the center of the ellipse is shifted, see Figure (11.5. 1). The coordinates of the center of the ellipse is called the back stress. The concept of the kinematic hardening is important for reverse and cyclic loading.

What is J2 plasticity?

The von Mises theory is often called “J2 plasticity” because it is usually described in terms of the so- called second mechanics invariant of the stress, 1 When used to mean “tutorial,” the word “primer” is supposed to rhyme with “glimmer” not “timer.”

What is meant by yield criterion?

A yield criterion is a hypothesis defining the limit of elasticity in a material and the onset of plastic deformation under any possible combination of stresses.

Why is isotropic hardening?

Isotropic hardening means that the yield surface expands (or shrinks) in a uniform way about the hydrostatic axis.

What is hardening in plasticity?

The hardening law, also known as hardening rules, describes how the yield surface changes under the plastic deformation. The hardening rule governs the change in material strength as the plastic material deformation.

What is hardening parameter?

where p′ is the effective hydrostatic pressure, q is the deviatoric stress, H is defined as a hardening parameter which depends upon the plastic volumetric strains, k and r are the shape parameters of the yield function. The geometric representation of the yield function is shown in Figure 3.

What is multilinear isotropic hardening?

Isotropic Hardening. Multi-linear Isotropic Hardening: (Default) The multi-linear hardening is defined by a series of plastic strain/yield stress points. Figure 1 The multi-linear point definitions. The points must have ascending values.

What is Deviatoric stress?

Deviatoric stress is the difference between the stress tensor σ and hydrostatic pressure tensor p acting on the rock or soil mass.

What is von Mises and Tresca criteria?

Both Tresca and von Mises criteria are essentially yielding criteria that are typically used to predict an onset of yielding in homogeneous or isotropic ductile metals (Dieter, 1976; Dowling, 1993). Brazed joints, however, are quite far from isotropic.

What is von Mises failure criterion?

The von Mises criterion states that failure occurs when the energy of distortion reaches the same energy for yield/failure in uniaxial tension. Mathematically, this is expressed as, In the cases of plane stress, s3 = 0.

What is linear hardening?

Hardening and Softening As implied by the name “Linear Hardening”, the law normally models a response where the yield strength increases with plastic strain . In other words, E p ≥ 0 and K ≥ 0 .

What is von Mises formula?

Mathematically, the von Mises yield criterion is expressed as: J2 = K² Here, K is the yield stress of the material in pure shear. Yield stress is the point at which the material behavior transforms from elastic to plastic. It is often said that the material yields if the stress is greater than the yield strength.

How do you calculate hardening factor?

Measure of increase in hardness and strength caused by plastic deformation. It is related to true stress and true strain by the equation: s = s0d h where s is true stress, s0 is true stress at unit strain, d is true strain and h is strain hardening exponent.