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Materials 2012, 5(1), 12-26; doi:10.3390/ma5010012

Statistical and Graphical Assessment of Circumferential and Radial Hardness Variation of AISI 4140, AISI 1020 and AA 6082 Aluminum Alloy

Department of Mechanical Production Technology, College of Technological Studies, The Public Authority of Applied Education and Training (PAAET), P.O. Box 38322, Dhaya Abdalla Alsalim 72254, Kuwait
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Received: 17 October 2011 / Revised: 6 December 2011 / Accepted: 15 December 2011 / Published: 23 December 2011
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Abstract

Hardness homogeneity of the commonly used structural ferrous and nonferrous engineering materials is of vital importance in the design stage, therefore, reliable information regarding material properties homogeneity should be validated and any deviation should be addressed. In the current study the hardness variation, over wide spectrum radial locations of some ferrous and nonferrous structural engineering materials, was investigated. Measurements were performed over both faces (cross-section) of each stock bar according to a pre-specified stratified design, ensuring the coverage of the entire area both in radial and circumferential directions. Additionally the credibility of the apparatus and measuring procedures were examined through a statistically based calibration process of the hardness reference block. Statistical and response surface graphical analysis are used to examine the nature, adequacy and significance of the measured hardness values. Calibration of the apparatus reference block proved the reliability of the measuring system, where no strong evidence was found against the stochastic nature of hardness measures over the various stratified locations. Also, outlier elimination procedures were proved to be beneficial only at fewer measured points. Hardness measurements showed a dispersion domain that is within the acceptable confidence interval. For AISI 4140 and AISI 1020 steels, hardness is found to have a slight decrease trend as the diameter is reduced, while an opposite behavior is observed for AA 6082 aluminum alloy. However, no definite significant behavior was noticed regarding the effect of the sector sequence (circumferential direction).
Keywords: hardness variation; AISI 4140; AISI 1020; AA 6082; reference block calibration; statistical analysis; response surface hardness variation; AISI 4140; AISI 1020; AA 6082; reference block calibration; statistical analysis; response surface
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This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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MDPI and ACS Style

Al-Khalid, H.; Alaskari, A.; Oraby, S. Statistical and Graphical Assessment of Circumferential and Radial Hardness Variation of AISI 4140, AISI 1020 and AA 6082 Aluminum Alloy. Materials 2012, 5, 12-26.

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