Johnson-Cook Damage Model

 In the design engineering stages, one must consider thoroughly the behavior of materials under intricate loading conditions. Von mises stress is a common approach to assess behavior of materials and it provides information regarding the initial deformation in the plastic region of the material. However, in the real application occasionally an object is experienced more complicated loading conditions like chronic damages caused by the change of temperature, strain rates, and combination of several stresses.

Figure 1. A ball under impact [1]

 Suppose a ball used in a football match, then this ball would experience different level of impacts throughout the game, notably when the game is played under a harsh condition which inevitably impacts the damage of the ball as can be seen in Figure 1. Hence, to understand the behavior of the material another sophisticated approach is immensely required, presumably engineers are able to alter the materials and invigorate the designs of this ball. Johnson Cook Damage (JCD) is often used to evaluate the behavior of materials under different strain rates. There are 3 salient factors of this model, including strain rates, temperature, and combinations of stresses. In which, JCD simultaneously accounts all these factors during the analysis. JCD is classified as a dimensionless parameter, where 1 signifies a damage condition and conversely 0 construes a non-damage condition. Herein, simple analysis of a concrete beam was analyzed by using ABAQUS, and the example result of JCD is depicted in Figure 2.

Figure 2. Finite Element Analysis of a Concrete Beam with JCD model.

Invariably, JCD is applied in objects which experience impacts or penetration issues during the application. In a piping system, for instance, JCD can be applied to assess the integrity of the piping geometry, notably to evaluate whether the piping system will fail when it will be impacted to an object, such as a gouge in the piping/pipeline which emerges due to mechanical damage. For example, Zhang created simulation of X70 pipeline with a simplified john cook model [2], herein, the author was capable to appraise how the stress-strain of the material when the steel pipeline was subjected to a projectile which could cause damage to the pipeline surface, as can be seen in Figure 3. This high-speed impact condition was imperative to be assessed, thus, this simulation could provide information regarding the dynamic behavior of this metal material and how the shape transformation would look like under this condition.

Figure 3. Stress-Strain Material of the Steel Pipeline [2].

REFERENCES

1. Ishii et al. 2014. Effect of Soccer Shoe Upper on Ball Behaviour in Curve Kicks. 
2. Zhang et al. 2010. Study on the Dynamic Behaviours of X70 Pipeline Steel by Numerical Simulation