【作者】 解妙霞；

【导师】 李全禄；

【作者基本信息】 陕西师范大学 ， 声学， 2006， 硕士

【摘要】 压电材料在医学超声诊断中扮演着至关重要的角色,它们构成了换能器的核心。把电激励脉冲转换成发射到人体软组织的声束。检测由器官表面和内部结构反射回来的微弱的回声信号。压电材料必须具备以下几个要求:区分激励和接收的电信号,完成电能和机械能之间的相互转换,将强脉冲声波发射进组织,搜集微弱的回声信号,对每个角色,都需要设备工程师们来调整材料的特性,调节电阻抗,提高机电耦合系数,调节声阻抗使之接近人体组织,做适当形状的换能器以聚焦声束。单个材料设计不能同时优化所有的材料属性,材料工程师们面临着具有挑战性的工作:对每一个特殊的设备确定特定的材料。 由压电陶瓷和高分子聚合物构成的复合材料,由于其声阻抗低,横向耦合弱,机电耦合强等优点,已应用于医学超声探头,且其应用日益广泛。按照压电陶瓷和聚合物的连接方式,可将压电复合材料分为10种类型。其中,1-3型压电复合材料是指将一维自连的陶瓷相埋置于三维自连的聚合物基体中。目前,1-3型压电复合材料主要采用切割填充工艺制备。由于这种工艺制备的1-3型压电复合材料易于批量生产,因此目前广为采用。 由于1-3型压电复合材料由两相组成,所以它的性能参量不仅取决于两种组分的参量,还依赖于其几何结构,材料的优化设计远较单一组分宏观均匀的压电陶瓷复杂。影响1-3型压电复合材料性能的主要因素有:压电陶瓷相的体积百分比,压电陶瓷柱的性能及空间尺寸,基体相的性能和复合材料的加工工艺及极化工艺等。分析上述因素对1-3型压电复合材料压电特性的影响规律对制作高灵敏度的压电(复合材料)换能器有着非常重要的意义。进行1-3型压电复合材料的性能分析,一般有三种方法:解析法、有限元法和实验法。解析法一般是建立在大量的假设之上,跟实际结果有较大出入;而由于材料本身特性的限制以及实验条件的局限性,应用实验方法进行压电复合材料分析在实际应用中受到很大的限制。 有限元作为一种广泛应用于解决实际问题的数值方法,将其引入压电复合材料研究中具有重要意义。本文的主要研究内容为: 一、概述了医用超声换能器材料的发展史及压电复合材料的发展简史、1-3型压电复合材料的原料和该材料的制备方法以及1-3型压电复合材料的分析方法。 二、介绍了有限元法及其软件ANSYS在压电复合材料分析中的理论和应用,更多还原

【Abstract】 Piezoelectric materials play a crucial role in medical diagnoses. They are the heart of the transducer, converting the electrical driving pulse into an acoustics beam that is projected into the soft tissues of the human body, and then detecting the weak echos reflected by organ boundaries and internal structures. The piezoelectric materials must meet following demands: interfacing with the drive/receive electronics, performing the electromechanical energy conversion, projecting the strong acoustic pulse into tissue, and gathering the weak echos. In each of these roles, the piezoelectric materials allow the device engineer to tailor the material properties: adjusting the electrical impedance to that of the electronic chain, enhancing the electromechanical coupling, moving the acoustic impedance close to that of tissue, and shaping the transducer to focus the beam. Specially, in designing piezocomposites, a single material design does not optimize all material properties simultaneously. The material engineer has a challenging task in designing a piezocomposite for each particular device.Piezocomposites which consist of piezoelectric ceramic and large molecules polymer, are well suited for ultrasonic transducers in medical imaging application due to their advantages over conventional piezoelectric materials, such as low acoustics impendence, low transverse electromechanical coupling coefficient and high electromechanical coupling coefficient. Due to these advantages, piezocomposites have become increasingly attractive for various applications. The piezocomposites are classified as ten types by combinations of piezoelectric ceramic and polymer. Among these ten types, 1-3 piezocomposite is that one dimension connective ceramic pillars place in the three connective dimension polymers. The dice and fill technique is the most widespread fabrication method for materials used in medical ultrasonic applications due to easy batch production.Because 1-3 piezocomposites is composed of two phases, it’s properties depend on not only the properties of these two components but also their geometry structure. So the material design is far more complicate than unitary ceramic design.The key factors that influence the properties of 1-3 piezocomposites are theceramic volume fraction, properties and geometry dimension of ceramic, properties of polymer, processing technology and polarization technology of piezocomposites. Studying how these factors influence the properties of 1-3 piezocomposites are of great significant in fabricating high sensitivity piezocomposites transducers. Generally, there are three methods to analysis the properties of 1-3 piezocomposites: analytic computation > finite element method and experiment. Analytic computation is based on a lot of hypotheses, so the results from which are very different from the actual results. Experiment study can produce more accurate results. However, it is impossible to study every case experimentally, which is both expensive and time consuming.Finite element method has become a proven and reliable numerical simulation method and had been widely applied to engineering structures design and mechanics analysis as a tool, so it would be signality to apply finite element method topiezocomposites analysis.The main content is following as:At first, materials and piezocomposites used for medical ultrasonic transducers are briefly reviewed. The fabrication and study method of 1-3 piezocomposites are summarized.Give a brief introduction of the finite element method and the finite element method software ANSYS applications in piezocomposites analysis. And presents some commonly process and attentions in applying the finite element method software ANSYS to piezocomposites analysis. Some factors that influence of the properties of 1-3 piezocomposites are studied utilizing ANSYS.A new program used in ANSYS was developed. We can set the factor influcing the properties of 1-3 piezocomposites as parameters. When this program is performed, the parameters are needed. You can easily change these parameters’ value, in order to study every case. So, it made the design of 1-3 piezocomposites very convenient. Furthermore, it is very significant to develop new 1-3 piezocomposites.Piezoelectric characters of 1-3 piezocomposites were measured using impedance analyzer and d33 meter. The results obtained through finite element analysis, analytic computation and experiment are compared and it is found that the finite element method is utilizable and produces more precise results than analytic computation.更多还原