Effect of low-temperature rolling on the propensity to adiabatic shear banding of commercial purity tungsten

ABSTRACTA model is presented for computing the temperature increase associated with the formation of an adiabatic shear band. The hypothesis is that the heating is supplied by the difference in energy of a pile-up of n dislocations and the energy of n individual dislocations. The heating is assumed to occur within a volume determined by the grain size (i.e. slip band length) and an effective thermal length determined by the dislocation velocity. The model predicts increases in temperature with increasing shear modulus (G), increasing numbers of piled up dislocations (n), increasing Burgers vector (b), increased grain size (d), and increased dislocation velocity (vd). Increasing temperature is also predicted with decreasing heat capacity (c*) and thermal diffusivity (α) as would be expected. The model was applied to low carbon steel for which considerable data are available. Application to low carbon steel gives a temperature increase of about 1400K. The implied result that untempered martensite should be observed after adiabatic shear banding is in agreement with examples cited in the literature. Further investigation into the dynamics of pile-up release and the associated heat transfer mechanisms is discussed.

Download Full-text

Dependence of the Coefficient of Friction on the Sliding Conditions in the High Velocity Range

Journal of Tribology ◽

10.1115/1.2833808 ◽

1999 ◽

Vol 121 (1) ◽

pp. 35-41 ◽

Cited By ~ 49

Author(s):

A. Molinari ◽

Y. Estrin ◽

S. Mercier

Keyword(s):

Coefficient Of Friction ◽

High Velocity ◽

Numerical Solutions ◽

Constitutive Relations ◽

Shear Banding ◽

Normal Pressure ◽

Adiabatic Shear ◽

Velocity Range ◽

Adiabatic Shear Banding ◽

The Coefficient Of Friction

The velocity, normal pressure, and slider size dependence of the coefficient of dry friction of metals in the range of high sliding velocities (V ≥ 1 m/s) is investigated theoretically. Failure of the adhesive junctions by adiabatic shear banding is considered as the underlying process. The concept of asperity shearing by the adiabatic shear banding mechanism represents a new approach to unlubricated high velocity friction. Analytical solutions of a coupled thermomechanical problem are given for two constitutive relations. Numerical solutions for steel-on-steel friction showing a decrease of the coefficient of friction with the sliding velocity for different normal pressures are presented. The model is considered to be adequate in the velocity range of 1–10 m/s where friction enhanced oxidation or surface melting are believed not to interfere with the asperity shearing process.

Download Full-text

Numerical Study of Impact Penetration Shearing Employing Finite Strain Viscoplasticity Model Incorporating Adiabatic Shear Banding

Journal of Engineering Materials and Technology ◽

10.1115/1.3030880 ◽

2008 ◽

Vol 131 (1) ◽

Cited By ~ 18

Author(s):

Patrice Longère ◽

André Dragon ◽

Xavier Deprince

Keyword(s):

Damage Mechanics ◽

Numerical Study ◽

Shear Banding ◽

Three Dimensional ◽

Adiabatic Shear ◽

Deformation Model ◽

Viscoplastic Material ◽

Predictive Tool ◽

Adiabatic Shear Banding ◽

Wide Range

This work brings forward a twofold contribution relevant to the adiabatic shear banding (ASB) process as a part of dynamic plasticity of high-strength metallic materials. The first contribution is a reassessment of a three-dimensional finite deformation model starting from a specific scale postulate and devoted to cover a wide range of dissipative phenomena, including ASB-related material instabilities (strong softening prefailure stage). The model, particularly destined to deal with impacted structures was first detailed by (Longère et al. 2003, “Modelling Adiabatic Shear Banding Via Damage Mechanics Approach,” Arch. Mech., 55, pp. 3–38; 2005, “Adiabatic Shear Banding Induced Degradation in a Thermo-Elastic/Viscoplastic Material Under Dynamic Loading,” Int. J. Impact Eng., 32, pp. 285–320). The second novel contribution concerns numerical solution of a genuine ballistic penetration problem employing the above model for a target plate material. The ASB trajectories are shown to follow a multistage history and complex distribution pattern leading finally to plugging failure mechanism. The corresponding analysis and related parametric study are intended to put to the test the pertinency of the model as an advanced predictive tool for complex shock related problems.

Download Full-text