本文選題：超聲滾壓　切入點(diǎn)：PZFlex　出處：《南昌航空大學(xué)》2017年碩士論文

【摘要】：鈦合金因其高的比強(qiáng)度和優(yōu)良的抗腐蝕性能,是理想的航空結(jié)構(gòu)材料。但是,與不銹鋼和高溫合金相比,鈦合金零件對表面損傷和缺陷具有更大的敏感性。據(jù)統(tǒng)計,鈦合金工件發(fā)生的事故大約25%是由于表面質(zhì)量引起的。而滾壓加工通過適當(dāng)?shù)膲毫κ沟帽患庸ぜ砻娼饘佼a(chǎn)生彈塑性變形進(jìn)而形成塑形流動,將工件材料微觀輪廓凸峰填入凹谷,從而可以提高表面質(zhì)量。但傳統(tǒng)滾壓加工易在工件表層形成加工硬化層,與內(nèi)部基體材料有明顯分層現(xiàn)象,易造成表層脫落。將超聲加工技術(shù)與普通滾壓相結(jié)合既能增強(qiáng)滾壓強(qiáng)化效果,又能解決工件表面的分層現(xiàn)象。本文首先使用PZFlex有限元軟件設(shè)計并制作了超聲振動滾壓裝置,然后利用該滾壓裝置,通過設(shè)置不同實(shí)驗工藝參數(shù)研究了超聲滾壓對TC4鈦合金金相組織及其力學(xué)性能的影響規(guī)律。本文主要完成了以下工作:1.首先根據(jù)機(jī)械振動學(xué)基本理論,在諧振條件下基于一維縱振波動方程對超聲振子結(jié)構(gòu)尺寸及節(jié)面位置進(jìn)行理論計算,分析了相應(yīng)的應(yīng)力及振速分布。然后,利用聲傳播專業(yè)領(lǐng)域有限元軟件PZFlex,采用時域瞬態(tài)分析方法對所設(shè)計的超聲振子進(jìn)行瞬態(tài)動力學(xué)分析和仿真。仿真分析了超聲振子的不同階次振型,發(fā)現(xiàn)第一階諧振頻率符合設(shè)計需要,且與理論設(shè)計符合較好。并分析了其穩(wěn)態(tài)響應(yīng)、振動位移及截面位置。根據(jù)理論計算及仿真結(jié)果制造了相應(yīng)的壓電超聲振子,并采用頻率特性分析儀測量得到其實(shí)際諧振頻率,采用多普勒測振儀測量得到其端面位移振動情況,結(jié)果表明仿真結(jié)果與實(shí)際測量值符合較好。2.設(shè)計制造了與數(shù)控車床刀架相匹配的夾具,利用所開發(fā)的超聲振子,在車床上搭建了超聲滾壓實(shí)驗系統(tǒng)。采用不同的工藝參數(shù),對TC4鈦合金軸外圓表面分別進(jìn)行了傳統(tǒng)滾壓及超聲滾壓。并對滾壓后的工件進(jìn)行制樣,采用XJ P-3A型金相顯微鏡及Agilent Technologies Inc G200型納米壓痕測試儀分別進(jìn)行了金相組織觀察和工件表層材料力學(xué)性能測試。3.金相觀察結(jié)果顯示滾壓后試樣表層晶粒明顯細(xì)化,6遍滾壓較3遍滾壓對零件表層金屬材料作用更明顯,超聲滾壓較傳統(tǒng)滾壓變形層深度更大且分層現(xiàn)象有一定改善。納米壓痕測試結(jié)果表明,彈性模量隨著試樣表層到內(nèi)部距離增加而逐漸減小以至趨于平穩(wěn),且隨著加工遍數(shù)的增加彈性模量顯著增大。同時超聲滾壓相較于普通滾壓,增大了試樣材料彈性模量值,且對于表層材料深度增加同樣更為顯著。
[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.
【學(xué)位授予單位】：南昌航空大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG663;TG305

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