钛合金超声振动滚压装置研制及实验研究

发布时间：2018-04-07 15:09

本文选题：超声滚压　切入点：PZFlex　出处：《南昌航空大学》2017年硕士论文

【摘要】：钛合金因其高的比强度和优良的抗腐蚀性能,是理想的航空结构材料。但是,与不锈钢和高温合金相比,钛合金零件对表面损伤和缺陷具有更大的敏感性。据统计,钛合金工件发生的事故大约25%是由于表面质量引起的。而滚压加工通过适当的压力使得被加工件表面金属产生弹塑性变形进而形成塑形流动,将工件材料微观轮廓凸峰填入凹谷,从而可以提高表面质量。但传统滚压加工易在工件表层形成加工硬化层,与内部基体材料有明显分层现象,易造成表层脱落。将超声加工技术与普通滚压相结合既能增强滚压强化效果,又能解决工件表面的分层现象。本文首先使用PZFlex有限元软件设计并制作了超声振动滚压装置,然后利用该滚压装置,通过设置不同实验工艺参数研究了超声滚压对TC4钛合金金相组织及其力学性能的影响规律。本文主要完成了以下工作:1.首先根据机械振动学基本理论,在谐振条件下基于一维纵振波动方程对超声振子结构尺寸及节面位置进行理论计算,分析了相应的应力及振速分布。然后,利用声传播专业领域有限元软件PZFlex,采用时域瞬态分析方法对所设计的超声振子进行瞬态动力学分析和仿真。仿真分析了超声振子的不同阶次振型,发现第一阶谐振频率符合设计需要,且与理论设计符合较好。并分析了其稳态响应、振动位移及截面位置。根据理论计算及仿真结果制造了相应的压电超声振子,并采用频率特性分析仪测量得到其实际谐振频率,采用多普勒测振仪测量得到其端面位移振动情况,结果表明仿真结果与实际测量值符合较好。2.设计制造了与数控车床刀架相匹配的夹具,利用所开发的超声振子,在车床上搭建了超声滚压实验系统。采用不同的工艺参数,对TC4钛合金轴外圆表面分别进行了传统滚压及超声滚压。并对滚压后的工件进行制样,采用XJ P-3A型金相显微镜及Agilent Technologies Inc G200型纳米压痕测试仪分别进行了金相组织观察和工件表层材料力学性能测试。3.金相观察结果显示滚压后试样表层晶粒明显细化,6遍滚压较3遍滚压对零件表层金属材料作用更明显,超声滚压较传统滚压变形层深度更大且分层现象有一定改善。纳米压痕测试结果表明,弹性模量随着试样表层到内部距离增加而逐渐减小以至趋于平稳,且随着加工遍数的增加弹性模量显著增大。同时超声滚压相较于普通滚压,增大了试样材料弹性模量值,且对于表层材料深度增加同样更为显著。
[Abstract]:Titanium alloy is an ideal aeronautical structure material because of its high specific strength and excellent corrosion resistance.However, titanium alloy parts are more sensitive to surface damage and defects than stainless steel and superalloy.According to statistics, about 25% of the accidents of titanium alloy workpieces are caused by surface quality.However, due to the proper pressure, the metal on the surface of the workpiece is subjected to elastoplastic deformation and the plastic flow is formed. The surface quality of the workpiece can be improved by filling the cam peak of the material into the concave valley.However, the traditional rolling process is easy to form a workpiece surface layer, which has obvious delamination with the internal matrix material, which can easily cause the surface layer to fall off.The combination of ultrasonic machining and common rolling can not only enhance the rolling strengthening effect, but also solve the delamination phenomenon of workpiece surface.In this paper, the ultrasonic vibration rolling device is designed and fabricated by using PZFlex finite element software, and then the influence of ultrasonic rolling on the metallographic structure and mechanical properties of TC4 titanium alloy is studied by setting different experimental technological parameters.This paper mainly completed the following work: 1.Based on the basic theory of mechanical vibration and the one-dimensional longitudinal vibration wave equation, the structure size and node position of ultrasonic oscillator are calculated theoretically, and the corresponding stress and vibration velocity distribution are analyzed.Then, using the finite element software PZFlex in the field of acoustic propagation, the transient dynamic analysis and simulation of the designed ultrasonic oscillator are carried out by using the time-domain transient analysis method.The simulation results show that the first order resonance frequency meets the design needs and is in good agreement with the theoretical design.The steady-state response, vibration displacement and section position are analyzed.Based on the theoretical calculation and simulation results, the corresponding piezoelectric ultrasonic vibrators are fabricated. The actual resonant frequencies are measured by frequency characteristic analyzer, and the displacement vibration of the end face is measured by Doppler vibration measuring instrument.The results show that the simulation results are in good agreement with the measured values.The fixture matching with the tool holder of NC lathe is designed and manufactured. The ultrasonic rolling experiment system is built on the lathe by using the developed ultrasonic vibrator.Traditional rolling and ultrasonic rolling on the outer surface of TC4 titanium alloy shaft were carried out with different process parameters.After the workpiece was rolled, the microstructure of the workpiece and the mechanical properties of the surface layer of the workpiece were observed by using XJ P-3A metallographic microscope and Agilent Technologies Inc G200 nano-indentation tester respectively.The results of nano-indentation test show that the elastic modulus decreases gradually and becomes stable with the increase of the distance from the surface to the inside of the sample, and increases significantly with the increase of the processing times.At the same time, ultrasonic rolling increases the elastic modulus of the specimen, and increases the depth of the surface material more significantly than that of the ordinary rolling.
【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG663;TG305

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