Intensity Field Design for Pistons and Cylinder Heads in the Laser Induced Thermal Loading System

Recently we built up a novel thermal loading system for pistons and cylinder heads, with the aid of shaped high power laser[1]. The incident Gaussian beam was transformed into a concentric multi-circular pattern with the aid of a diffractive optical element (DOE) [2]. In this paper, a reverse method based on finite element analysis was proposed to design the intensity field of transformed laser beam, in order to simulate temperature field and thermal stress on pistons and cylinder heads in the real working condition. A transient three-dimensional heat conduction model [3] with convective boundary conditions was built to obtain the temperature field. Then, the numerical results were verified by experiments. With the validated model, spatial intensity field of the transformed laser beam was optimized to approach the target temperature field. From the numerical model, thermal stress and can be computed by adding loading condition and mechanical properties. Thermal fatigue life-span was calculated with the classic theory. Pistons and cylinder heads are large structures with complex configuration. The analysis shows that the reverse method incorporated with numerical simulation can reduce design cycle and design expense efficiently.