开斜槽纵－扭复合振动阶梯形变幅杆设计

基于声波传播基本理论,探讨了单激励下斜槽传振杆实现纵-扭复合振动的机制。采用有限元分析方法研究了阶梯形复合变幅杆结构尺寸对其固有频率的影响规律,设计出了谐振频率在20 k Hz左右的纵-扭复合振动变幅杆。研究结果表明:谐振频率为20 498 Hz时该变幅杆能在纵向振动单激励下实现纵-扭复合振动,且振幅呈周期性变化。此研究结果可应用于超声纵-扭复合振动加工声学系统的设计。     

6061-T6铝合金纵-扭复合振动超声深滚加工试验研究

基于纵-扭复合振动超声加工和超声深滚加工提出了纵-扭复合振动超声深滚加工工艺。采用普通深滚与纵-扭复合振动超声深滚2种加工方法对供应态6061-T6铝合金轴件进行表面强化处理,研究深滚工艺参数对加工表面质量的影响。结果表明:引入纵-扭复合振动后,超声深滚工艺参数对表面质量的影响规律与普通深滚不同,且在相同的工艺参数下,超声深滚所获得的表面粗糙度Ra值要小于普通深滚,最高降低约50%,而表面显微硬度和硬化率则有大幅提高,硬化率最高约为普通深滚的3倍,经纵-扭复合振动超声深滚处理后的表面更光滑,从而证明了纵-扭复合振动超声深滚加工工艺能更有效地实现6061-T6铝合金的强化处理。     

纵-扭复合振动超声深滚加工表面强化研究

目的基于纵-扭复合振动超声加工和超声深滚加工提出了纵-扭复合振动超声深滚加工工艺,研究各深滚工艺参数对工件表面强度的影响,以验证二维超声振动加工技术在表面强化技术领域的应用效果。方法采用单因素试验法对6061-T651铝合金轴件分别进行纵-扭复合振动超声深滚与常规深滚加工试验,然后用MH-5数显硬度计测试每组参数下的表面显微硬度,研究静压力、工件转速和进给量对工件表面显微硬度的影响,并将两种试验结果进行对比。结果在设定工艺参数内,纵-扭复合振动超声深滚工艺所获得的表面显微硬度均高于同等加工条件下常规深滚工艺。纵-扭复合振动超声深滚加工时,表面显微硬度随静压力和工件转速的增大先增大后减小,随进给量的增大先减小后增大再减小;常规深滚加工时,表面显微硬度与静压力近似呈线性关系,且随工件转速的增大先增大后减小,随进给量的增大一直减小。结论纵-扭复合振动超声深滚加工工艺能更有效地实现6061-T651铝合金的表面强化处理。     

纵扭复合超声端面铣削表面微结构建模与试验研究

目的 对纵扭复合超声端面铣削加工表面微结构进行预测,以优化加工参数。方法 对纵扭复合超声端面铣削进行运动学分析,并在其基础上建立三维运动轨迹方程。对刀尖轨迹仿真,且研究该运动方式下的加工特性。通过对切削刃和工件离散化建立纵扭复合超声端面铣削表面微结构理论模型,并利用MATLAB进行三维表面仿真。对TC4钛合金进行超声振动切削试验。结果 理论仿真和切削试验结果均表明超声纵扭端面铣削时,随振幅的增加,由振动引起的表面微观结构特征愈加明显。扭纵幅值比增大时,加工表面微观结构凹坑效应弱化,At/Al=0.55时,加工表面呈条形片状微观结构。振动频率和主轴转速会影响表面微观结构单元的疏密程度。结论 加工表面微结构的生成与振动频率、振幅、扭纵复制比、切削速度等加工参数相关,铣削实验得到的加工表面变化趋势与表面理论模型吻合,该表面模型能够优化超声加工参数。     

超声椭圆振动切削技术及装置应用研究现状及进展

首先,阐述了超声椭圆振动切削技术、原理及其装置特点,着重论述了装置各构成部分的特点及其主要应用类型与材料。其次,分析了国内外学者在双激励、单激励方式下实现纵弯、纵扭、双弯曲和弯扭等复合超声振动装置结构设计及其优化方面的研究成果与进展,并且比较了超声椭圆振动切削与传统加工在加工性能、工件表面质量和加工精度等方面的加工优势与适用范围,以及不同超声振动装置在各切削加工中所能获得的加工效果。最后,对超声椭圆振动切削装置的发展趋势进行了总结和展望,指出该装置发展将朝着结合能场的方向发展。     

纵扭复合超声椭圆振动振子的设计与实验研究

基于纵振波动方程和扭振波动方程设计一种纵振振子和一种扭振振子,利用有限元分析方法 (FEM),提出一种对纵振振子和扭振振子结构振动曲线进行简并设计新型纵扭复合超声椭圆振动振子的方法,对简并的超声椭圆振动振子进行了结构动力学仿真分析,并对纵扭复合超声椭圆振动振子样机进行阻抗特性和振动特性实验研究。结构动力学仿真、样机阻抗特性和振动特性实验得到的参数和曲线对纵扭复合超声椭圆振动振子的制造、装配、电路阻抗匹配和生产应用具有一定指导意义和参考价值。     

超声纵-扭复合铣削钛合金刀具磨损特性研究

目的采用超声纵-扭复合振动加工方法,获得较长的刀具使用寿命。方法采用理论建模与不同铣削振动方式,研究刀具磨损特性。通过超景深电子显微镜和粗糙度测试仪,分别对刀具微观形貌、工件表面粗糙度进行了分析;通过不同铣削方式加工钛合金材料,对刀具磨损特性进行了系统分析。结果与普通铣削和超声纵振铣削相比,超声纵-扭铣削方式下,刀具后刀面磨损减小,工件表面粗糙度降低。经测试,当去除面积为6356mm~2时,超声纵-扭复合加工刀具后刀面磨损量VB为103μm,分别比普通和超声纵振加工时降低了38μm和36μm。当去除面积为4530 mm~2时,Ra为1.2μm,普通铣削和超声纵振铣削的Ra则分别为1.62μm和1.38μm。由于超声纵振加工仅仅是在轴向方向实现了分离,后刀面时刻冲击着已加工表面,当去除面积为6356 mm~2时,刀具后刀面磨损量反有超出普通铣削的趋势。结论超声纵-扭复合加工从旋转方向内实现了刀-屑分离,在铣削过程中,极大地减少了刀具后刀面对已加工表面的冲击,从而使得刀具寿命有所延长,为高效加工、难加工材料提供了一种加工方法。     

超声波镗削复合振型变幅杆的设计与分析

超声振动加工在难加工材料方面的应用越来越广,而在镗削中应用的不多。大量的实验证明复合振动加工效果优于普通振动加工效果,而如何在超声镗削加工中实现"复合"是一个棘手的问题。针对复合超声镗削,设计一种实现纵扭复合振动的变幅杆。阐述振型转换原理,进行结构计算,借助有限元软件ANSYS分析结构各项参数对性能的影响并总结规律,为复合超声镗削变幅杆的设计和优化提供了参考。     

新型超声振动结构的研究进展

对近几年超声加工技术在硬脆材料加工方面的研究进展进行综述,阐述不同超声振动形式的加工特点和国内外的研究现状,如超声纵向振动、扭转振动、纵扭复合、椭圆振动等,最后对我国超声加工技术今后的发展提出一些建议.     

纵扭复合振动超声加工运动特性研究

外加超声电源激励产生的复合振动输出模态作用于加工刀具上,从而改变实际超声加工过程中刀具相对于工件之间的运动状态,出现不同于传统磨削加工的运动特性,由运动合成原理,在分析纵扭复合振动作用下刀具切削运动轨迹特征及由此产生的加工特性下对普通磨削加工和复合振动超声加工进行磨削工程氧化锆陶瓷材料表面试验,提出了超声加工运动形式的不同所体现出的工艺优势,理论与试验结果表明超声振动下独特的运动形式体现出的加工特性会促进切屑排除,使得刀痕沟槽均匀,改善加工表面质量,突出超声加工工艺方法应用于精密及超精密加工的重要意义。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.