【作者】 张宇；

【导师】 侯荣国； 吕哲；

【作者基本信息】 山东理工大学 ， 工程硕士（专业学位）， 2020， 硕士

【摘要】 微细水射流(医用水刀)技术可以作为一种手术分离器械用于对人体组织进行切割、分离等,它具有高度灵活性、切除组织选择性和保护性,无热损伤,术中出血量少,手术时间短等优点。因此,该技术被广泛应用于骨科、眼科、创伤外科等外科手术中。目前,微细水射流技术仍存在一些难题,例如射流集束性较差,压力不稳定等;另外,微细水射流对加工具有较高的韧性和弹体的人体组织材料去除方面还没有相对成熟的理论体系,并缺乏相应的实验研究。为此,本文以与人体肝脏组织最为接近的猪肝脏为研究对象,优化设计微细水射流喷嘴结构尺寸,建立猪肝脏应力-应变本构模型;并用于微细水射流冲击猪肝脏材料过程中,获得猪肝脏组织材料破坏阈值;实验验证射流参数对猪肝脏组织及血管破坏情况。本文主要研究工作如下:一、微细水射流喷嘴内外流场数值模拟及其内部结构尺寸优化设计。理论分析微细水射流流体流动状态,确定流体性质,得出流体流动控制方程;利用计算流体动力学软件Fluent对微细水射流在喷嘴内外流场分布进行数值模拟,获得了喷嘴内外射流压力场、速度场等的分布规律,并分析锥直型喷嘴内部结构如收缩角、直线段长度和喷嘴长度对射流速度的影响规律,获得喷嘴内部结构尺寸参数的最佳组合为:收缩角α=13°,直线段长度I=0.2 mm,喷嘴长度L=2.0 mm;通过引入过渡圆角来提高射流束的集束性,增强射流稳定性,研究表明:过渡圆角的最佳的过渡比为0.3。二、建立猪肝脏应力-应变本构模型。通过对猪肝实质的准静态单轴拉伸实验,开展猪肝脏组织在准静态力作用下力学和动态响应性能研究获得应变率和加载方向对猪肝脏组织力学性能的影响规律,获得猪肝脏组织的弹性模量均值为0.27 MPa,破坏应变发生在55-65%;利用改进的SHPB装置测量猪肝脏组织的动态压缩力学响应,建立基于指数和三阶Yeoh的高应变率作用下的不可压缩黏超弹性本构方程。三、数值模拟微细水射流冲蚀猪肝脏组织过程。利用Ansys/Ls-Dyna软件通过将不可压缩黏超弹性本构模型引入猪肝脏组织切割过程数值模拟,分析猪肝脏组织材料在水射流加工时的变形与损伤过程,并获得材料分离破坏的破坏临界射流压力值。四、实验研究微细水射流加工猪肝脏组织材料去除机理。将前述优化设计的喷嘴安装在自制的微细水射流加工设备上,开展微细水射流加工猪肝脏实验以验证数值模拟结果。实验结果表明:模拟结果与实验结果变化趋势相同,数值接近,因此所建立本构模型和模拟方法合理、可行。通过分析射流压力对猪肝脏组织材料去除机理的影响规律,发现猪肝脏表面在微细水射流冲击下存在应变值较大的的区域,冲击压力越高,冲击区域材料隆起量也越大;当冲击压力达到3.39 MPa时,冲击区域最高应力超过屈服极限,猪肝脏材料发生破坏。实验研究微细水射流切割猪肝脏时组织内部血管的损伤情况,结果表明:当射流压力超过5 MPa时能够保留直径0.8 mm血管;当射流压力超过6 MPa时能够保留直径1.0 mm血管;当射流压力超过7 MPa时对直径1.2 mm的血管具有一定的损伤。上述研究结果为微细水射流技术在医学中的技术推广提供了理论参考和数据支持。更多还原

【Abstract】 Micro-water jet(medical water jet)technology can be used as a surgical separation instrument for cutting and separating human tissues,etc.It has high flexibility,selective and protective resection of tissues,no thermal damage,and low intraoperative blood loss,short operation time and other advantages.Therefore,this technique is widely used in orthopedics,ophthalmology,trauma surgery and other surgical operations.At present,there are still some problems with the micro-water jet technology,such as poor jet bunching and unstable pressure.In addition,the micro-water jet has no relatively mature theoretical system for the processing of human tissue materials with high toughness and elastic body,and lacks corresponding experimental research.So,this article takes the pig liver closest to human liver tissue as the research object,and optimizes the structure size of the micro-water jet nozzle to establish a stress-strain constitutive model.And used in the process of micro-water jet impact on pig liver material,to obtain the pig liver tissue material destruction threshold.The experimental verification of the jet parameters on pig liver tissue and vascular disruption.It provides theoretical data for the application of micro-water jet technology in medicine.The main research work of this paper is as follows:Firstly,numerical simulation of the internal and external flow field of the micro-water jet nozzle and optimization of its internal structure size.Theoretical analysis of the flow state of micro-water jet fluid,determination of fluid properties,determination of fluid flow governing equation.The computational fluid dynamics software Fluent is used to numerically simulate the distribution of mico-water jets inside and outside the nozzle.The distribution of pressure field and velocity field of jet flow inside and outside the nozzle was obtained.The influence of the internal structure of the cone-shaped nozzle,such as the shrinkage angle,the length of the straight segment and the nozzle length,on the jet velocity was analyzed.The best combination to obtain the internal structure size parameters of the nozzle is: shrink angle α=13 °,straight line length I=0.2 mm,nozzle length L=2.0 mm.By introducing transition fillets to improve the jet beam concentrating and enhance the jet stability,the research shows that the optimal transition ratio for transition fillets is 0.3.Secondly,establish a stress-strain constitutive model of pig liver.The effects of strain rate and loading direction on the mechanical properties of pig liver tissues were studied through quasi-static uniaxial tensile experiments on porcine liver parenchyma.It is obtained that the average elastic modulus of pig liver tissue was 0.27 MPa,and the failure strain occurred at 55-65%.An improved SHPB device is used to measure the dynamic compression mechanical response of pig liver tissue,and an incompressible visco-hyperelastic constitutive equation based on exponential and third-order Yeoh’s high strain rate is established.Thirdly,numerical simulation of the process of erosion of pig liver tissue by micro-water jet.The Ansys/Ls-Dyna software is used to numerically simulate the cutting process of porcine liver tissue by introducing an incompressible visco-hyperelastic constitutive model to analyze the deformation and damage process of porcine liver tissue material during water jet processing,and obtain the failure threshold of material separation and destruction Jet pressure value.Fourthly,experimental study on the mechanism of removing liver tissue material from micro-water jet processing.The above-mentioned optimized design nozzle is installed on a self-made micro water jet processing equipment,and a micro water jet processing pig liver experiment is carried out to verify the numerical simulation results.The experimental results show that the simulation results have the same trend as the experimental results and the values are close.Therefore,the constitutive model and simulation method established are reasonable and feasible.By analyzing the influence of jet pressure on the mechanism of pig liver tissue removal,it is found that there is a region with a large strain value under the impact of micro-water jets on the surface of pig liver.The higher the impact pressure,the greater the amount of material bulging in the impact area.When it reaches 3.39 MPa,the highest stress in the impact area exceeds the yield limit,and the pig liver material is damaged.Experimental studies on the damage of blood vessels in tissues when micro-water jets cut pig livers,the results show that: when the jet pressure is 4 MPa,0.8 mm diameter vessels can be retained;when the jet pressure is 5 MPa,1.0 mm diameter vessels can be retained;When the pressure exceeds 6 MPa,there is a certain damage to blood vessels with a diameter of 1.2 mm.The above research results provide theoretical references and data support for the technical promotion of micro-water jet technology in medicine.更多还原