高能连续激光与外力载荷联合作用于铝合金的理论和实验研究

发布时间：2018-06-29 02:01

本文选题：激光辐照 + 预加载荷　；参考：《南京理工大学》2016年硕士论文

【摘要】：自激光被发现以来,由于其具有普通电磁波所不具备优点,被广泛的用于工业加工、医疗教育、国防军事领域。一方面当试件局部受到强激光辐照时,激光辐照区域温度迅速上升,造成材料的热-力学性质发生剧烈的变化,使得材料发生热软化、熔融乃至气化喷溅；另一方面由于材料弹性模量、屈服强度随温度升高逐渐降低,激光辐照区域进入塑性屈服阶段,并且随着辐照时间增大,屈服区域逐渐向试件内部扩大,对材料造成应力损伤。当工件被夹紧或飞机导弹在高速飞行时,试件会时刻处于外载荷预加载的情况,为了实际应用情况相符合,本文对高能激光与外加拉力联合作用铝合金靶材的问题进行了理论和实验研究。(1)基于热传导理论、热-力耦合理论和弹塑性理论建立二维物理模型,应用有限元方法对受单向拉伸载荷作用的铝合金板材在高斯分布的连续激光辐照下的温度场、应力场和出现等效应力极小值的时间进行研究。在数值计算中考虑材料性质的非线性和相变情况,本文首先研究了有／无外加载荷对塑性屈服时间、材料破坏机制的影响,接着研究了联合加载时激光功率密度、外加拉力和试件厚度与塑性屈服开始时间和出现等效应力极小值的时间的关系。(2)对1060和6061铝合金进行无激光辐照的单向拉伸实验,得到材料厚度、宽度对单轴拉伸时试件的断裂过程、断裂位移、断裂形貌、塑性屈服点和最大断裂载荷的影响。选取6061铝合金进行联合加载实验,记录了从外力加载到激光辐照直至试件完全断裂的外力载荷随位移的变化曲线,研究了联合加载时材料破坏的机制、激光辐照中心区域的温升情况、试件断裂所需激光辐照时间、试件断裂部位的形貌,研究了激光功率密度、外加载荷的大小以及试件厚度的变化对试件断口形貌、中心区域温升、试件断裂破坏所需的时间的影响。
[Abstract]:Laser has been widely used in the fields of industrial processing, medical education, national defense and military since it was discovered because it has the advantages of ordinary electromagnetic wave. On the one hand, the temperature of the laser irradiated region rises rapidly when the specimen is irradiated by a strong laser, which results in a drastic change in the thermal-mechanical properties of the material, resulting in thermal softening, melting and even vaporization spatter. On the other hand, due to the elastic modulus of the material, the yield strength decreases gradually with the increase of temperature, the laser irradiation region enters the plastic yield stage, and with the irradiation time, the yield region gradually expands to the inside of the specimen, causing stress damage to the material. When the workpiece is clamped or the aircraft missile is flying at high speed, the specimen will always be in the condition of external load preloading, in order to match the actual application, In this paper, the theoretical and experimental study on the effect of high energy laser and applied tension on aluminum alloy targets is carried out. (1) based on the heat conduction theory, the thermal-mechanical coupling theory and the elastic-plastic theory, a two-dimensional physical model is established. The temperature field, stress field and the time of minimum equivalent stress of aluminum alloy sheet subjected to uniaxial tensile loading under continuous laser irradiation with Gao Si distribution were studied by finite element method. The nonlinear properties and phase transition of materials are considered in the numerical calculation. Firstly, the effect of loading on plastic yield time and material failure mechanism is studied, and then the laser power density under combined loading is studied. The relationship between the applied tensile force and the thickness of the specimen is related to the beginning time of plastic yield and the time when the equivalent stress minimum appears. (2) the uniaxial tensile test of 1060 and 6061 aluminum alloys without laser irradiation is carried out and the thickness of the material is obtained. The influence of width on the fracture process, fracture displacement, fracture morphology, plastic yield point and maximum fracture load of the specimen during uniaxial tension. 6061 aluminum alloy was selected for combined loading experiment. The curves of external force load changing with displacement from external force loading to laser irradiation to complete fracture of specimen were recorded, and the mechanism of material failure under combined loading was studied. The temperature rise in the central region of laser irradiation, the time required for laser irradiation of the specimen, the morphology of the fracture site of the specimen, the laser power density, the magnitude of the applied load and the variation of the thickness of the specimen on the fracture surface of the specimen were studied. The effect of temperature rise in the central region and the time required for fracture failure of the specimen.
【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG146.21;TN249

【相似文献】