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2 International Journal of Applied Mechanics and Engineering

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Determination of constant parameters of copper as power-law hardening material at different test conditions

Kowser M. A., Mahiuddin M.

International Journal of Applied Mechanics and Engineering

2014

Vol. 19, no. 4

687--698

In this paper a technique has been developed to determine constant parameters of copper as a power-law hardening material by tensile test approach. A work-hardening process is used to describe the increase of the stress level necessary to continue plastic deformation. A computer program is used to show the variation of the stress-strain relation for different values of stress hardening exponent, n and power-law hardening constant, α . Due to its close tolerances, excellent corrosion resistance and high material strength, in this analysis copper (Cu) has been selected as the material. As a power-law hardening material, Cu has been used to compute stress hardening exponent, n and power-law hardening constant, α from tensile test experiment without heat treatment and after heat treatment. A wealth of information about mechanical behavior of a material can be determined by conducting a simple tensile test in which a cylindrical specimen of a uniform cross-section is pulled until it ruptures or fractures into separate pieces. The original cross sectional area and gauge length are measured prior to conducting the test and the applied load and gauge deformation are continuously measured throughout the test. Based on the initial geometry of the sample, the engineering stress-strain behavior (stress-strain curve) can be easily generated from which numerous mechanical properties, such as the yield strength and elastic modulus, can be determined. A universal testing machine is utilized to apply the load in a continuously increasing (ramp) manner according to ASTM specifications. Finally, theoretical results are compared with these obtained from experiments where the nature of curves is found similar to each other. It is observed that there is a significant change of the value of n obtained with and without heat treatment it means the value of n should be determined for the heat treated condition of copper material for their applications in engineering fields.

Effect of end-shortening on the response of a steel cantilever beam with an opening

Rahman M. A., Kowser M. A., Siddiqui M. T.

International Journal of Applied Mechanics and Engineering

2008

Vol. 13, no 3

735-751

This study is a continuation of our previous study that comprehensively dealt with the response of a slender cantilever beam with an opening of different geometry (circular, elliptical and square, respectively), having the same cross-sectional area, placed at different positions of the beam's span. The effect of end-shortening that becomes important at a high load is included in the present analysis. Obviously, stresses in these beams increase significantly due to the opening. Based on numerical calculations considering geometric nonlinearity and the effect of end shortening, it is found however, that the maximum values of the stresses are actually much smaller than their predictions are by linear theory without considering end-shortening. These stresses remain well below the proportional limit of highly elastic steel. Further, a similar analysis was performed for the case of a cantilever beam of a constant cross-section. It is found that the nonlinear analysis with end-shortening is much more important for a beam with an opening than it is for a beam of a constant cross-section. Though the topic chosen for this paper corresponds to a highly nonlinear boundary value problem, the numerical simulation scheme devised is sound enough to predict the response of the variable cross-section beams with high accuracy. Experimental results obtained by another research group have been compared by simulation; a very good agreement proves the soundness of the present numerical simulation scheme.