骨材料切削加工及一种新型刀具研究

发布时间：2018-01-08 01:09

本文关键词：骨材料切削加工及一种新型刀具研究　出处：《哈尔滨工业大学》2017年博士论文　论文类型：学位论文

【摘要】：随着电气化技术及机器人技术的突飞猛进,近年来越来越多的自动化手术系统及医疗手术机器人开始在临床上应用。而骨切削手术作为外科手术中的一项重要操作,得益于电气化和自动化技术的发展,其切削方法也越来越多样化,例如钻削、磨削、铣削等传统的机械加工方法在骨外科手术中也得到广泛应用。然而,骨头材料的切削本质上是一种破坏式去材加工,需要破坏骨组织的原貌而利用其再生长功能来达到医学目的。其切削过程中过高的切削力、切削温度及异常的切削状态会造成骨组织及其周围组织的严重损伤并制约病人术后的康复。此外,骨头材料作为一种各向异性材料,其密质骨层结构类似纤维增强复合材料结构,且呈现出一定脆性,在切削过程中易产生裂纹并扩展至骨结构内部。因此,研究骨头材料切削的相关机理及切削手段,在切削过程中保持骨材料组织结构的完整性,对骨科手术技术发展及相关设备的开发具有重要意义。本文围绕骨头材料的切削加工技术,先从其切削机理入手,通过观察密质骨正交切削过程中切屑形成的物理过程,提出骨材料正交切削包括剪切变形切削、剪切裂纹切削和断裂切削的三种切削模式。通过采用断裂力学对其切削变形进行建模,并结合骨材料各向异性特性对骨材料切削过程不同切屑形态的去除机理提出了统一解释。基于该模型对骨材料切削过程切屑形态进行了预测,得到不同切削模式间转变的临界切削厚度,并通过实验观察其切削力及切削表面微观形貌分析了不同切削模式下骨材料的切削加工性能及对骨材料的表面破坏。根据骨材料密质骨层的纤维增强复合结构特性,建立了与骨单位纤维方向相关的切削剪切强度各向异性模型。在该材料模型的基础上,结合骨材料切削过程中的纤维切削角度、材料切削变形模式、犁沟效应等相关效应建立骨材料动态铣削力模型。通过骨材料铣削实验证明该模型可以准确预测骨材料铣削过程动态切削力,为骨材料铣削过程切削参数的选择提供了指导意义。在骨材料切削区域优化布置热电偶以测量真实的切削温度,观察骨材料铣削过程中温度分布及随切削参数的变化。分析了骨材料铣削温度的分布特性,结合切削理论建立骨材料铣削过程的温度场分布解析模型,并通过实验验证了模型的有效性。通过对骨材料铣削温度场分布和切削温度穿透深度分析骨材料铣削过程中对骨材料产生热效应的主要影响因素。针对骨材料切削过程中易发生断裂切削及过高切削力和温度的情况,根据骨材料切削机理设计一种断裂-剪切复合铣削刀具以实现骨材料的高效低温切削。通过特殊的螺旋面结构设计使得刀具在较小进给速度时可以工作在剪切变形或剪切裂纹切削模式,而在较大进给速度时工作在断裂-剪切复合切削模式,从而达到减小骨材料切削表面损伤的目的。采用PCD聚晶金刚石作为刀具材料制造刀具,并通过与相同尺寸的普通铣削刀具进行骨材料切削加工试验对比,实验证明该刀具可以在相同切削参数下改善骨材料切削表面质量,降低切削力和切削温度,从而有效提高切削效率,缩短手术切削时间。针对骨材料切削过程伴随剪切裂纹及断裂变形的特点,研究了声发射信号对骨材料切削过程状态监测的有效性。采用小波包分解提取了声发射信号的小波能比特征实现骨材料切削层深度的监测。建立了小波系数时域轴及频域轴的多尺度混合隐马尔科夫模型的监测策略,对骨材料切削过程的刀具磨损状态进行监测。通过实验分析证明声发射信号可以有效表征骨材料切削过程的切削层深度及刀具磨损的状态特征。
[Abstract]:With the rapid development of electrical technology and robot technology, automatic operation system and medical surgical robot is more and more widely used in clinic in recent years. And the operation of bone cutting is an important operation in surgery, thanks to the development of electrical and automation technology, the cutting method is becoming more and more diversified, such as drilling. Grinding, milling and other traditional machining methods have been widely used in bone surgery. However, the nature of the material cutting head is a kind of damage to material processing, requires the destruction of bone tissue and the use of the original growth function to achieve medical purpose. The cutting force cutting temperature is too high, the cutting and abnormal state will cause bone tissue and its surrounding tissue damage and restrict patient rehabilitation after surgery. In addition, the bone material as an anisotropic material, the Cancellous bone layer structure similar to fiber reinforced composite structure, and showed certain brittleness, easy to crack and extended to the bone structure in the cutting process. Therefore, the research on its mechanism of bone material cutting and cutting tools, maintain the integrity of tissue bone structure in the cutting process, is of great significance to the development of the development of Department of orthopedics operation technology and related equipment. This paper cutting technology on bone material, first from the cutting mechanism of chip formation process through physical observation of cancellous bone in orthogonal cutting process, the bone material including shear deformation orthogonal cutting cutting, three kinds of cutting shear crack and fracture mode of cutting cutting through. By using the fracture mechanics on the cutting deformation model, and combined with the characteristics of anisotropic bone material removal mechanism of bone material cutting process of different chip forms a unified solution Release. The model of the process of bone chip morphology is predicted based on the obtained critical cutting thickness between different cutting patterns change, and through the experimental observation of the cutting force and surface morphology analysis of the cutting performance of bone material and surface material for bone destruction under different cutting patterns according to the structural characteristics of composite. Bone cancellous bone layer reinforced, a cutting shear strength anisotropy model related to bone unit fiber direction. Based on the material model, combined with the fiber cutting angle of bone material in the cutting process, the deformation mode of material cutting, ploughing and other related effects to establish the dynamic model of milling force. The bone material the bone material milling experiments show that the model can accurately predict the bone material milling process of dynamic cutting force, cutting parameters of bone material milling process can provide the guidance Meaning. In bone material cutting area layout optimization of thermocouple cutting temperature measurement real temperature distribution, observation of bone material in the milling process and changes with the cutting parameters. Analysis of the distribution characteristics of bone material milling temperature, combined with cutting theory to establish the bone material milling process temperature field analytical model, and verified the validity of the model through the experiment. Based on the milling temperature field distribution of bone material and cutting temperature penetration depth analysis on the main factors influencing the thermal effect of bone material milling process. The bone material is easy to break and crack cutting and high cutting force and temperature of the bone material cutting process, according to the high low temperature cutting cutting mechanism design of a bone material fracture shear composite milling tool to achieve bone materials. Through the design of the special spiral surface of the cutter can work in shear in smaller feed speed Shear deformation or shear crack cutting mode, and in the larger feed speed in fracture shear composite cutting mode, it can reduce the damage of bone material cutting surface. Using PCD as tool materials made of polycrystalline diamond tool, and bone material cutting test by comparing the ordinary milling cutter with the same size, experimental results show that the the tool can improve the bone cutting surface quality at the same cutting parameters, cutting force and cutting temperature, thus effectively improve the cutting efficiency, shorten the operation time. According to the cutting process of cutting bone material with characteristics of shear deformation and crack fracture, the research of acoustic emission signal on the effectiveness of bone material cutting process monitoring using wavelet. The ratio of packet decomposition to extract feature monitoring bone material cutting depth of the acoustic emission signal. Wavelet can establish wavelet coefficients in time domain The monitoring strategy of multiscale mixed hidden Markov model and frequency axis axis, to monitor tool wear cutting process of bone material. The experiment result shows that the acoustic emission signal can be effectively characterized by bone material cutting process of cutting depth and tool wear state characteristic.

【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TH777

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