VARIABILITY OF MECHANICAL PROPERTIES AND RELIABILITY OF THERMO MECHANICALLY TREATED REINFORCEMENTS IN NIGERIA

Ubani Obinna Uzodimma, Okonkwo Victor Odinaka, Osayanmon Osarenkhoe

Abstract

Thermo Mechanically Treated (TMT) reinforcements from different manufacturers in Nigeria were subjected to tensile strength tests to determine the variability of their yield strength, ultimate tensile strength, and ductility. For the 70 samples tested, 91.5% met the required characteristic strength of 500 MPa, and the percentage elongation at fracture satisfied all the requirements of BS 4449:2005. The probability distribution of the yield strength of the TMT reinforcements were found to conform better to normal distribution with a Chi-Square value (X2 ) of 4.342 against lognormal and Weibull distribution, with Chi-Square values of 4.80 and 6.536 respectively. The mean yield strength of the samples was found to be 532.8 MPa with a standard deviation of 24.926 MPa, and coefficient of variation of 4.678%. The probability of the samples tested falling below the yield strength of 500 MPa was found to be 9.4% with a reliability index of 1.316. The ultimate tensile strength to yield strength ratio (Rm/Re) was found to be averagely high (with a mean of 1.356 and a standard deviation of 0.095) when compared to the requirements of BS 4449:2005 and test results from other parts of the world. This was the major source of non-conformity to the requirements of BS 4449:2005. Read full PDF

Keywords: Thermo Mechanically Treated Steel, Yield strength, Ductility, Ultimate tensile strength

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