大功率激光器功率密度分布在热处理中的模拟研究

【作者】 吴钟壮；

【导师】 伏云昌；

【作者基本信息】 昆明理工大学 ， 光学， 2012， 硕士

【摘要】 自1960年激光问世之后,随着大功率激光技术的不断发展,激光热处理技术走出了实验室,并广泛应用于实际当中。在激光表面硬化处理中,激光照射在金属表面,加热区域的温度经历了迅速的上升和下降,奥氏体变为马氏体,从而提高了材料的硬度和强度。激光表面硬化处理是许多物理现象和处理条件的耦合,影响处理结果的主要因素是激光输出功率、扫描速度和光斑半径,而激光输出功率和光斑半径又决定了激光功率密度分布。由于不同激光器的功率密度分布是不一样的,同一台激光器在不同高度的功率密度分布也是不一样的。因此,在使用一台激光器之前,知道激光器的功率密度分布是非常重要的,这是实验研究的理论基础。在2009年昆明理工大学引进了一台大功率CO2激光器,为了获得该激光器功率密度分布的解析表达式,采用热敏纸测量大功率CO2激光器在不同功率和高度的激光光斑分布,用MATLAB软件对实验光斑进行图像处理,建立数学模型模拟激光功率密度分布,并与采集光斑进行比较。通过激光表面硬化处理实验及温度场计算验证激光功率密度分布解析表达式。取得的实验结果和理论计算相符合,结果表明采用热敏纸测量大功率CO2激光器功率密度分布的方法是可行的,得到功率密度分布的解析表达式可作为理论计算的条件,具有一定意义。更多还原

【Abstract】 Since the laser was invented in1960, the technique of laser heat treatment broke out of the laboratory and was put into practice widely, along with the development of high-power laser. In the process of surface hardening treatment with laser, the temperature of the heating zone on the workpiece irradiated by laser goes through rapid rise and fall, and the austenite is transformed into the martensite. Hence, the hardness and strength of materials are improved. Kinds of physical phenomena and processing conditions are related to surface hardening treatment with laser. The main factors influencing the treatment are laser output power, scanning speed and the size of laser spot. Meanwhile, the power density distribution of the laser is determined by laser output power and the size of laser spot. The power density distribution varies from the different lasers, and even the same laser does not share the same power density at the different heights. Therefore, it is much important to know the power density distribution of the laser before use, which is theoretical basis for the experimental and study.In2009, a high-power CO2laser was bought by the Kunming University of Science and Technology. In order to obtain the analytic expression of power density distribution of the CO2laser, the laser spot distributions are measured under different power outputs and heights by using thermal paper. And then, experimental images of the laser spot are analyzed through the software MATLAB and a numerical model of laser power distribution is developed to be compared with the experimental spot. The laser surface hardening treatment experiments and calculations of temperature fields are done to verify the obtained analytic expression. The experimental results are in good agreement with the theoretical calculation. This demonstrates that it is feasible to measure the laser power distribution using thermal paper, and the analytic expressions of power distribution can be used as the condition of the theoretical calculation, and is of practical significant.更多还原