Studies on Rheological Relation of Materials by Taking into Account the Rate-dependent Evolution of Internal Defects at High Strain Rates

Abstract

It was experimentally observed that a rheological process of material is usually accompanied with an evolution of internal defects or micro-damage. Based on the micro-observation of the twinning evolution for Zircaloy-4, the adiabatic shear banding evolution for titanium alloy TB2 and the micro-cracks evolution for cast magnesium alloy ZM5-T4, thermoplastics PMMA and cement mortar, a rate-dependent defect/damage evolution law is suggested on the basis of thermo-activated mechanism. Correspondingly, a damage-modified rate-dependent rheological relation, taking into account the damage-weakening effect, is proposed and discussed.

A Method of Combined SHPB Technique and BP Neural Network to Study Impact Response of Materials

“…Such transverse inertia noises may be negligible in the experiments for most high‐strength alloys but become un‐negligible for low wave‐impedance materials such as porous materials. One possible way to overcome this difficulty is to use the pulse‐shaping technique [3], although the test strain rate may decrease correspondingly. The evolution of internal damage, which will display more significant influence on the apparent constitutive response of materials with increase of both strain and strain rates [4]. In fact, it has been observed that, if the strain is large enough and the strain rate is high enough, the deformation process of any material is usually accompanied with an evolution of internal damage, the accumulation of which will lead to the final failure of polymer.…”

“…The evolution of internal damage, which will display more significant influence on the apparent constitutive response of materials with increase of both strain and strain rates [4]. In fact, it has been observed that, if the strain is large enough and the strain rate is high enough, the deformation process of any material is usually accompanied with an evolution of internal damage, the accumulation of which will lead to the final failure of polymer.…”

A constitutive model for frozen soil based on rate-dependent damage evolution

“…For frozen soil, referring to some relevant research on metals and concrete, we shall establish a damage evolution equation by using the thermal activation theory to explain the damage evolution law of frozen soil (Arsenault, 1978). Wang et al (1999) conducted several dynamic tests and showed that the damage evolution process is a rate process that is similar to the rate process of viscoplatic deformation. Thus, from equation 3, the following function can be determined by analogy (Wang et al, 1999)…”

“…Wang et al (1999) conducted several dynamic tests and showed that the damage evolution process is a rate process that is similar to the rate process of viscoplatic deformation. Thus, from equation 3, the following function can be determined by analogy (Wang et al, 1999)…”

“…During the process of loading, damage evolution in materials will take place, time and other factors making the process considerably complex. Wang et al (1999) conducted a large number of experiments and pointed out the following: (a) From the combined macroscopic and microscopic view point, a macro-flow/deformation process of a material is microscopically accompanied with an evolution process of internal defects in different forms; and (b) the defect/damage evolution is dependent on both strain and strain rates, regardless of whether the form of defect/damage is a twin, adiabatic band or microcrack.…”