1-dimensional transient heat transfer axi-symmetric mathematical modelling to determine lowest hardness point of quenched steel bar

Elmaryami, Abdlmanam S. A. (2014) 1-dimensional transient heat transfer axi-symmetric mathematical modelling to determine lowest hardness point of quenched steel bar. PhD thesis, Universiti Tun Hussein Onn Malaysia.

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Abstract

One-dimensional (ID) model of any axisymmetric industrial quenched steel bar based on finite element method (FEM) has been applied to investigate the influence of process history on its material properties of seventy-five (75) cases on ten (1 0) different samples of steel. The lowest hardness point (LHP) and the effect of the radius of any steel bar on its temperature history and on LHP is determined. In this research hardness in specimen points was obtained by calculating characteristic cooling time for phase transformation (tsIs) to hardness. The model can be employed as a guideline to design cooling approach to achieve desired microstructure and mechanical properties such as hardness. A computer program of the model is developed, which can be used independently or incorporated into a temperature history software named LHP-software to continuously calculate and display temperature history of the industrial quenched steel bar and thereby calculate LHP and to study the effect of radius on temperature history and on LHP. Also the effect of different austenitizing temperatures and the effect of different quenching medium are studied. This technique (LHP-software) is more effective as compared to the conventional methods (Rockwell, Brinell, Vickers Hardness Tester, . . .etc) because they only used haidness calculated at the surface that is higher than LHP, which has negative consequence and can result in bending, deformation and failure of the component, as example it was found that the hardness on the surface of alloy steel 50B46H [R=12.5rnm, 850 O C , water quenched] = 52.808, while LHP = 44.953. LHPSoftware can be used instead of a number of real tools in steel industrial applications and is useful in a wide range of steel industrial field. The developed sofware based on (1-D) FEM model has been verified by comparing its hardness results with commercial finite element software results and also validated by experimental results. The comparison indicates its validity and reliability.

Item Type:Thesis (PhD)
Subjects:T Technology > TA Engineering (General). Civil engineering (General) > TA630-695 Structural engineering (General)
ID Code:5457
Deposited By:Normajihan Abd. Rahman
Deposited On:25 May 2014 08:43
Last Modified:25 May 2014 08:43

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