What is Johnson-Cook damage model?
The Johnson-Cook damage initiation criterion is a special case of the ductile damage criterion model for predicting the onset of damage due to nucleation, growth, and coalescence of voids in ductile metals.
What is Johnson-Cook equation?
Johnson-Cook strain rate dependence is the ratio of the yield stress at nonzero strain rate to the static yield stress (so that R(˙ε0)=1.0 ( ε ˙ 0 ) = 1.0 ). The yield stress is, therefore, expressed as. ¯σ=[A+B(¯εpl)n][1+Cln(˙¯εpl˙ε0)](1−ˆθm).
What is Johnson-Cook parameters?
Johnson–Cook Flow Stress Model These parameters are defined as: A-initial yield of the material, B-strain hardening coefficient, n-strain hardening exponent, C-strain rate sensitivity and m-thermal softening parameter.
What is Johnson-Cook strength?
The Johnson-Cook. strength model (Johnson and Cook 1983) is one of several strength models available in CTH. It. is an empirical model that computes material flow stress as a function of strain (work) hardening, strain-rate hardening, and thermal softening.
What is strain rate material?
Strain rate is the rate of deformation caused by strain in a material within a corresponding time. This gauges the rate where distances of materials change within a respective period of time.
Why is Johnson Cook model used?
Johnson–Cook (JC) constitutive model is a phenomenological flow stress model based on working conditions sheet temperature, strain induced, and punch strain-rate. The JC model is widely used for various varieties of materials over different ranges of strain-rate and temperatures.
Does higher strain mean stronger material?
As the speed increases, the yield strength and modulus also increase. The material appears to be stronger and stiffer simply due to the increase in strain rate, an effect that can also be achieved by keeping the strain rate constant and incrementally reducing the test temperature.
What are the effects of strain rate?
Strain rate effect is the basic property of solid materials while strain rate effect of nonuniform materials is more obvious than that of uniform materials. Concrete strength is highly sensitive to the process of loading.
What happens when you increase strain rate?
Thus, the yield strength, the ultimate strength and the tensile toughness are all observed to increase with increasing strain rate, which indicates both higher strength and higher toughness under tension at higher strain rates.
Does strain rate affect modulus?
As the strain rate increases we measure a higher yield stress and tensile modulus.
What is the most important problem with the Johnson-Cook fracture model?
The most important problem for implementing the Johnson-Cook fracture model into metal cutting simulation or other finite element analysis is to calibrate fracture constants for any proposed material. Johnson and Cook [1985] calibrated the material constants for three kinds of materials: OFHC copper, Armco iron, and 4340 steel.
What is the material constant in the Johnson Cook model?
Material constant (-) Δε : Increment of the equivalent plastic strain (-) ε : (When used in the Johnson-Cook constrictive model) equivalent plastic strain (-) εf: Equivalent strain to fracture (-) exp H fs
Which stress triaxialities are required for the Johnson-Cook failure model?
of the Johnson-Cook failure model, both of the stress triaxialities for the original specimens, η 0 , and the specimens fracture after tension tests, η f , are required. All these stress triaxialities are computed depending on the measurements by
Is there an enhanced Johnson–Cook strength model for splitting?
An enhanced Johnson–Cook strength model for splitting strain rate and temperature effects on lower yield stress and plastic flow. Comput. Mater. Sci. 2016;113:231–265. doi: 10.1016/j.commatsci.2015.11.034. [CrossRef] [Google Scholar] 5.