【作者】 陈健；

【导师】 陈锋；

【作者基本信息】 湖南大学 ， 机械工程， 2023， 硕士

【摘要】 在骨外科手术中,传统的手术器械如骨凿、咬骨钳和骨钻等需施加较大的外部压力来实现有效截骨,操作不易控制,无法对骨头进行精确切割,另一方面容易造成周围软组织损伤,导致术中出血多以及术后并发症。因此,开发一种精确、安全和高效的骨外科手术设备具有十分重要的意义。超声骨刀作为一种新型骨科手术器械具有切削力小,手柄轻巧且易控制、截骨精度高和良好的组织选择性等优点,在骨外科手术中得到广泛应用。当前,对于超声骨刀的设计主要是采用传统解析法,计算过程繁琐,不适合复合结构的设计;另一方面,在工作过程中,由于损耗因素的存在,超声骨刀将不可避免产生热量,引起手柄温度升高和过热现象,进而降低骨刀的振动和切削性能。针对上述问题,本文基于夹心式压电换能器结构,提出了一种纵振频率为22.5k Hz的1/2波长超声骨刀的设计方案。为简化理论计算,首先通过传输矩阵法,将超声骨刀各组件视为一个等效四端网络,由参数矩阵表示两端力与速度关系,根据初始条件及边界连续条件计算出了超声骨刀各组件的初始尺寸参数。之后,以此为基础,构建了超声骨刀的有限元仿真模型,并用模态分析来对其进行了初步的验证,对于产生的误差采用响应面方法进行了尺寸参数优化,并由谐响应分析对优化后超声骨刀谐振时的刀尖振幅、阻抗和应力分布分别进行了计算。另外,分析了螺栓预紧力对超声骨刀振动特性的影响,当螺栓预紧力在50-90MPa时,超声骨刀的振动性能最为稳定且刀尖振幅较大。基于上述优化后的结构和尺寸参数,加工制造出了超声骨刀原型机,通过阻抗分析仪对超声骨刀的阻抗特性进行了分析,测量得到的超声骨刀谐振频率与有限元仿真结果基本保持一致。同时,根据测量得到的等效电学参数对超声骨刀进行了阻抗匹配设计,以减少功率损耗,进而减小能量损失。然后,采用激光位移传感器对超声骨刀的刀尖振幅进行了测量,单峰振幅值为35.5um,满足骨组织切削要求。为确保骨刀切削的稳定性,对影响超声骨刀实际工作特性的因素进行了分析,包括工作温度、驱动电压等。研究发现将超声骨刀的工作温度控制在55℃以下可保持超声骨刀的高效和稳定。当强迫风冷措施的对流换热系数超过10W/(m~2·K)时,最高温度可以有效降低到55℃以下,进而限制过热现象。最后,由牛皮质骨切削实验表明超声骨刀能够精确有效地切割骨组织,由鸡蛋蛋壳切削实验表明超声骨刀能够在切削硬组织(蛋壳)的情况下,有效地保护软组织(壳膜),具有良好的组织选择性切割能力。更多还原

【Abstract】 In orthopedic surgery,traditional surgical instruments,such as bone chisel,rongeur and bone drill,need to exert large external pressure to achieve effective osteotomy,the operation is not easy to control,and cannot accurately cut the bone.On the other hand,it is easy to cause damage to the surrounding soft tissue,resulting in more intraoperative bleeding and postoperative complications.Therefore,it is of great significance to develop an accurate,safe,and efficient surgical equipment for orthopedic surgery.As a new type of orthopedic surgical instrument,ultrasonic bone scalpel has the advantages of small cutting force,light handle and easy control,high accuracy of osteotomy and good tissue selectivity,and has been widely used in orthopedic surgery.At present,the traditional analytical method is mainly used in the design of ultrasonic bone scalpel,the calculation process is complicated,and is not suitable for the design of composite structure.On the other hand,in the working process,due to the existence of loss factors,ultrasonic bone scalpel will inevitably generate heat,resulting in handle temperature rise and overheating phenomenon,and then reduce the vibration and cutting performance of the bone scalpel.To solve the above problems,based on the structure of sandwich piezoelectric transducer,a design scheme of 1/2-wavelength ultrasonic bone scalpel with longitudinal vibration frequency of 22.5k Hz is proposed in this paper.To simplify the theoretical calculation,firstly,each component of the ultrasonic bone scalpel was regarded as an equivalent four-terminal network by the transfer matrix method,and the relationship between force and velocity at both ends was represented by the parameter matrix.The initial size parameters of the ultrasonic bone scalpel components were calculated according to the initial conditions and boundary continuity conditions.Then,on this basis,the finite element simulation model of ultrasonic bone scalpel is established,and the initial design is verified by modal analysis.The response surface method is used to optimize the size parameters for the resulting error.And the tip amplitude,impedance and stress distribution of the optimized ultrasonic bone scalpel are calculated by harmonic response analysis.In addition,the influence of bolt pre-tightening force on the vibration characteristics of the ultrasonic bone scalpel is analyzed.When the bolt pre-tightening force is 50-90MPa,the vibration performance of ultrasonic bone scalpel is the most stable and the tip amplitude is larger.Based on the optimized structure and size parameters,the prototype machine of the ultrasonic bone scalpel is manufactured,and the impedance characteristics of the ultrasonic bone scalpel are analyzed by impedance analyzer.The measured resonant frequency of ultrasonic bone scalpel is basically consistent with the results of finite element simulation.At the same time,the impedance matching design of ultrasonic bone scalpel is carried out according to the measured equivalent electrical parameters to reduce the power loss and energy loss.Then the tip amplitude of ultrasonic bone scalpel is measured by the laser displacement sensor,and the single peak amplitude is35.5um,which meets the requirements of bone cutting.To ensure the cutting stability of the bone scalpel,the factors affecting the actual working characteristics of ultrasonic bone scalpel are analyzed,including working temperature,driving voltage and so on.It is found that the efficiency and stability of ultrasonic bone scalpel can be maintained by controlling the working temperature below 55℃.When the convective heat transfer coefficient of forced air cooling measures exceeds 10W/(m~2·K),the maximum temperature can be effectively reduced to below 55℃,thus limiting overheating.Finally,the experiment of bovine cortical bone cutting showed that ultrasonic bone scalpel could cut bone accurately and effectively,and the experiment of eggshell cutting shows that ultrasonic bone scalpel can effectively protect soft tissue(shell membrane)when cutting hard tissue(eggshell),and has good tissue selective cutting ability.更多还原