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In the present paper, the investigation results on the strain dependence of the Rayleigh wave velocity are presented. Plane dog-bone metal specimens were deformed by tension at a constant strain rate. The specimens were made of low-carbon steel with a carbon content of 0.1% (C10) and 0.2% (C22), martensitic stainless steel X40Cr13, and commercially pure titanium (CP Ti). Discontinuity points in the stress dependences of ultrasonic velocity and damping were found. These points are considered to be ultrasonic criteria for the stage change in the deformation process. [ABSTRACT FROM AUTHOR]

This paper deals with an ultrasonic technique based on the measurement of acoustic birefringence of shear elastic waves for the evaluation of plasticity margin of an aluminum alloy operating in the conditions of Far North and the Arctic. We tested flat samples under uniaxial static tension at room and subzero temperatures. Besides, we performed ultrasonic measurements. We have found that acoustic birefringence monotonically changes during plastic deformation. The effect of plastic strain on the acoustic birefringence is associated with damage accumulation and texture change. As a result of the study, we have obtained a correlation equation allowing us to estimate the plasticity margin of the aluminum alloy at a subzero temperature, as well as at room temperature, using the measurement results of acoustic birefringence. [ABSTRACT FROM AUTHOR]

The paper is concerned with the skin effect of plastic deformation, which was discovered circa ninety years ago. The study is carried out with the help of the hydrogen diagnostics. Accumulation of hydrogen is shown to occur due to the dissociation of atmospheric moisture under the process of plastic deformation of metals in a thin surface layer comparable to the grain size. Hydrogen is accumulated in pores and microcracks, whose volume in the surface layer increases hundred-fold. The zones of localization of plastic deformation coincide with the local surface zones of hydrogen storage. The obtained experimental data lead to the conclusion that the surface layer cannot be considered as a continuous medium. [ABSTRACT FROM AUTHOR]

In this paper, we propose a multi-time scale modeling technique for analyzing cyclic plastic deformation in crystalline solids subject to periodic loading. An asymptotic expansion of the variables in the time domain, together with homogenization forms the basis of multi-time scaling. In the macroscopic scale analysis, the oscillatory behavior of the load is averaged out and neglected, and the rate of averaged material behavior is quite slow in cyclic deformation. Implicitly, this means that the periodicity of some variables may be assumed for the oscillatory potion of the material behavior may be approximated. In this formulation, the governing equations are divided into two initial-boundary value problems with two different time scale: one is long time scale problem for describing the smooth averaged solution (global problem) and the other is for the remaining oscillatory potion (local problem). For the global problem, long time increments, which are longer than one cycle period, can be used and this multi-time scaling becomes an effective integrator. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]