A fractal and computer graphical simulation to characterise surface roughness by hardened steel turning
A machines surface appears irregular and is recognised as a non stationary random system. Therefore, conventional methods fail to give a precise assessment of the surface profile of a machined component. Very recently fractal methods have been introduced for the surface characterisation of a machines component. Among these methods, the Weierstrass-Mandelbrot (W-M) function is used as an analytical tool to characterise the surface profile due to the fact that it satisfies the mathematical properties of the surface. The successful characterisation depends on a simulation process in which fractal parameters are determined. This work extends fractal conceptual research into an application in the surface characterisation of hardened steel turned components and introduces an iterative algorithmic method of simulation for parametric determination. The method generates an artificial spectrum with fractal features on a computer screen to simulate the real surface obtained from experiment. If the simulated spectrum is statistically similar to that of the experiment, it can represent the real surface profile and the parameters of the W-M function could be used to characterise the surface profile. The work has also investigated the estimation of fractal parameters and how they effect the spectrum. An interactive software package has been developed to implement the simulation which provides both industry and academics with a means of more accurate assessment of surface measurement. Besides the investigation of surface roughness, the residual stress distribution in the superficial layers of a hard-turned component is also investigated using finite element method (FEM). The result shows that the residual stress distribution depends mainly on the initial stress release rather than new stress induction.