【作者】 禹东赫；

【导师】 张国顺；

【作者基本信息】 天津大学 ， 精密仪器及机械， 2007， 博士

【摘要】 激光加工技术是涉及光学、机械学、电子学、计算机等多种学科的高新技术,激光打孔是较早达到实用化的激光加工技术,但是目前还有许多问题需要进一步深入研究。由于激光打孔时激光焦点和打孔对象的相对位置、材料反射率的变化,激光峰值功率调节都影响到打孔速度和质量。因此,为了对不同材料进行有效地打孔,需要对激光束的能量、脉冲宽度和激光焦点相对位置等打孔参数进行综合控制。本课题的任务是在对激光打孔过程物理机理研究分析的基础上,研发用于金刚石拉丝模激光自动打孔的数控加工系统。本文主要研究了在激光与材料相互作用下声波信号随时间变化关系,高频超声波Q调制方法,以及配合计算机研究出声控激光打孔系统。一、首先论述了激光打孔技术目前国内外的发展状况,并结合激光与物质相互作用的原理,在理论上深入分析了激光打孔过程的物理机理,研究了在激光脉冲作用时材料升温、熔化、气化以及产生冲击波的条件。本文提出了一种具有创新性的用于对金刚石拉丝模打孔的方案。二、为获得快速打孔的效果,在激光器上也做了创新性的改进,采用高频超声技术控制压电陶瓷换能器,把谐振腔Q值的调制频率提高到150kHz,在200W以上的高功率激光器上获得了高峰值功率的激光脉冲。三、通过打孔过程伴生声波现象的研究,分析了大量的实验数据和曲线,发现了打孔产生的声波信号能反映打孔过程的状态,证明用声波能够控制打孔过程,同时还证明了打孔过程产生的红外光不适合控制打孔,并提出了按照材料的特性改变打孔速度的加工方法。四、综合上述研究成果,结合计算机技术,研究出了激光打孔专用的声控打孔控制系统,这套系统是通过声波传感器在线测量,按照打孔工艺要求,控制工作台的移动,激光束焦点始终处于最佳正确位置,使打孔过程精确而快捷。这种方法在国内外均未见报道。大量的实验表明,对金刚石拉丝模打孔有很好效果。文章最后也提出了今后研究方向,以及需要进一步解决的技术问题,对于完善这项新方法指出了方向。更多还原

【Abstract】 Laser machining processing is a high technology related to lots of branches of sciences and technologies, such as optics, machinery, electronics and computer, laser drilling is one of the old applications of laser machining processes. Yet many issues remain to be solved when high quality holes are to be drilled in various materials today. Because of laser drilling speed and quality is effected by the changing in laser’s focus position, reflectivity and laser peak value power. Therefore, laser power, pulse width, laser focus position and some other parameters should be set differently to drill different materials with high quality and speed.The objective of this Dissertation was to study digitally controlled laser machining system for diamond drilling for wire drawing dies, on the basis of study and theoretical analysis of physical mechanism for laser drilling process.The investigations performed in this Dissertation were focused on the time dependence of audible sound signals under laser beam and material interaction, developments of a high frequency Q-modulation method using ultrasound and a acoustically controlled laser drilling system in combination of computer.1. We introduced the development situation of laser drilling technology at home and abroad. And we analyzed theoretically the laser drilling physical process, in which detailed considerations of the material temperature increase, formation of melt, vaporization and introduction of recoil pressure under the condition when materials are exposed to the laser beam. An innovative solution was proposed in diamond drilling for wire drawing dies.2. To improve further the drilling speed, an innovative improvement was performed at laser resonator, the use of a high frequency of ultrasonic vibration in total reflection mirror enables Q-modulation frequency in laser resonator up to 150 kHz, high laser peak power pulses were obtained at 200 W and it meets the requirements of laser drilling process.3, We found this sound signals represented drilling process and concluded that drilling process could be controlled using sound signals, whereas infrared signals met control requirement of the process, through the study of phenomena of sound produced in laser drilling and analysis of massive data of experiments and graphs, and methods to improve drilling speed were proposed according to material properties.4, Bringing together all our research data, an acoustically controlled laser drilling system for special purpose was developed in combination of computer. On the basis of on-line detection of acoustic transducer and process schedule, this system controlled the worktable movement so that the laser focus can be put on a so correct position, this method makes laser drilling process precise and quickly. The method has not reported yet. Lots of experiments showed good results at diamond drilling for wire drawing dies.A future improvement of this method was proposed in the end of this dissertation.更多还原