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The aim of this work was to texturize surfaces of steel engine components to reduce the coefficient of dynamic friction and wear between two surfaces. The elements of the texture had the shape of a spherical half-shell and were produced by the overlap of femtosecond laser pulses with donut shape. The incubation effect was estimated using the D-scan method to relate the ablation threshold to the number of overlapping pulses. Thus, the control of the focal position of the laser beam and the number of overlapped pulses, taking into account the effects of incubation, made it possible to obtain this type of dimple with controlled shape and size. A distribution of dimples with density of 11% caused an 18% reduction in the coefficient of friction in a tribological pair DIN 16MnCr5 and SAE 52100 steel sphere. [ABSTRACT FROM AUTHOR]

Light scattering of a radially inhomogeneous droplet, which is modeled by a multilayered sphere, is investigated within the framework of Generalized Lorenz-Mie Theory (GLMT), with particular efforts devoted to the analysis of the internal field distribution in the cases of shaped beam illumination. To circumvent numerical difficulties in the computation of internal field for an absorbing/non-absorbing droplet with pretty large size parameter, a recursive algorithm is proposed by reformulation of the equations for the expansion coefficients. Two approaches are proposed for the prediction of the internal field distribution, namely a rigorous method and an approximation method. The developed computer code is tested to be stable in a wide range of size parameters. Numerical computations are implemented to simulate the internal field distributions of a radially inhomogeneous droplet illuminated by a focused Gaussian beam. [ABSTRACT FROM AUTHOR]

In thermal fatigue test, the key point is whether the temperature field on the top surface of cylinder head induced by the heat source can well match it in real service. In order to produce the target temperature field in service which is measured by thermocouples, shaped laser beam generated by diffractive optics element (DOE) is chosen as the heat source to irradiate on the top surface of cylinder head. The DOE is designed based on the Gerchberg-Saxton (GS) algorithm and the simulated temperature field is calculated by finite element model (FEM). The results show that the simulated and experimental temperature field can well match the target one which demonstrates that this method is feasible to produce the target temperature field and can be used in thermal fatigue test.