基于ABAQUS多频率超声变幅杆稳态及谐响应分析

超声加工技术已经涉及到了多个领域,超声变幅杆是超声加工处理设备中超声振动系统的重要组成部分之一。为了对多频率超声变幅杆进行对比分析,以圆锥形变幅杆为例,选取25、30、35 kHz振动频率的变幅杆,运用ABAQUS大型非线性有限元仿真软件,对多频率变幅杆进行稳态及谐响应分析研究。对多频率变幅杆进行稳态对比分析,在圆锥形变幅杆添加力载荷,对比分析不同频率变幅杆的位移及应力变化曲线,得出多频率变幅杆在稳态分析及谐响应过程中的变化规律。     

超声变幅杆的动力学分析

超声变幅杆是功率超声振动系统的重要组成部分,它的主要功能是把机械振动位移放大并把能量集中在较小的辐射面上,变幅杆的放大系数是超声振动系统中的重要参数。用微元法建立圆锥形超声变幅杆纵向振动的波动方程,用分离变量法和连续振动体的边界条件求解超越波动方程,得到圆锥形超声变幅杆放大系数与变幅杆的大小端直径之比、长度以及外激频率3个变量之间的数学表达式。为研究变幅杆的放大系数与变幅杆的大小端直径之比、长度以及外激频率的关系,依次把3个变量中的2个变量设为常量,对另外一个变量进行抽样,计算变幅杆的放大系数。通过Matlab对超声变幅杆放大系数的样本计算数据进行曲线拟合,定性分析了圆锥形超声变幅杆放大系数随变幅杆大小端直径之比、长度、外激振动频率变化的关系。     

超声加工振动系统设计的若干问题

本文讨论应用于超声加工的压电换能器的设计问题,简介几种常用的超声变幅杆,并提出两种新型变幅杆的设计方法。一、引言超声加工是功率超声应用中比较早用于生产的技术之一,国内外已有广泛的应用。超声加工设备中的关键部件是超声换能器及变幅杆(包括传振杆),加上加工工具一般统称为超声振动系统(见图1),其主要作用是把电能转换为声能并依特定要求传送到加工区域。     

超声变幅杆的动力学分析（英文）

超声变幅杆是功率超声振动系统的重要组成部分,它的主要功能是把机械振动位移放大并把能量集中在较小的辐射面上,变幅杆的放大系数是超声振动系统中的重要参数。用微元法建立圆锥形超声变幅杆纵向振动的波动方程,用分离变量法和连续振动体的边界条件求解超越波动方程,得到圆锥形超声变幅杆放大系数与变幅杆的大小端直径之比、长度以及外激频率3个变量之间的数学表达式。为研究变幅杆的放大系数与变幅杆的大小端直径之比、长度以及外激频率的关系,依次把3个变量中的2个变量设为常量,对另外一个变量进行抽样,计算变幅杆的放大系数。通过Matlab对超声变幅杆放大系数的样本计算数据进行曲线拟合,定性分析了圆锥形超声变幅杆放大系数随变幅杆大小端直径之比、长度、外激振动频率变化的关系。     

超声辅助微细磨料水射流加工装置的研制及实验研究

为了提高磨料水射流的加工性能,设计了超声辅助微细磨料水射流加工系统,磨料供给采用前混合方式。超声喷嘴装置是该系统的关键,并研究了其加工机理,利用超声振动产生具有空化效应的脉冲水射流,通过脉冲射流的高强度动压力作用和空化作用以提高磨料水射流的加工能力。变幅杆是超声装置的核心部件,通过有限元分析验证变幅杆的性能,确保变幅杆能够有效且准确地工作。冲蚀实验证明:超声振动作用可以提高冲击力及材料去除率。然而,随着振幅的增加,表面质量下降。     

超声辅助微细磨料水射流加工装置的研制及实验研究（英文）

为了提高磨料水射流的加工性能,设计了超声辅助微细磨料水射流加工系统,磨料供给采用前混合方式。超声喷嘴装置是该系统的关键,并研究了其加工机理,利用超声振动产生具有空化效应的脉冲水射流,通过脉冲射流的高强度动压力作用和空化作用以提高磨料水射流的加工能力。变幅杆是超声装置的核心部件,通过有限元分析验证变幅杆的性能,确保变幅杆能够有效且准确地工作。冲蚀实验证明:超声振动作用可以提高冲击力及材料去除率。然而,随着振幅的增加,表面质量下降。     

基于Mindlin理论的新型模式转换超声振动系统设计与研究

基于波的纵振动理论和Mindlin厚板弯曲振动理论,设计研究了由三段复合变幅杆、中厚圆盘、大尺寸圆筒组成的新型模式转换超声振动系统.对所设计的振动系统进行数值计算和有限元模态和谐响应分析,同时研究各几何参量对振动系统谐振频率的影响规律,并通过实验进行测试.结果表明:设计结果和有限元分析及测试结果之间的误差较小;系统谐振频率随着圆盘厚度的增加而增大,随着变幅杆大小端半径的增加而增加;随着变幅杆各段长度、圆管段高、内径的增大而减小.研究结果验证了所建立的新型超声振动系统谐振频率方程的正确性,所设计系统的结构合理、振动效果良好,为谐振频率的修正提供了依据,也为超声辅助加工技术特别是硬脆材料曲面的高精度加工提供了一种新型超声振动系统.     

基于旋转超声加工的GFRP罐体侧壁开孔系统设计

针对传统的玻璃钢罐体人工开孔方式存在开孔效率低、定位精度低差、开孔质量低等问题,设计一种针对GFRP罐体侧壁开孔的旋转超声加工系统。系统包含工件的输送、装夹、旋转超声主轴、进给驱动和刀具位置调整等部分,重点介绍旋转超声主轴和进给系统。运用有限元法设计带有开孔器的变幅杆,获得满足谐振频率的变幅杆结构,并通过有限元软件对带有开孔器的变幅杆进行谐响应分析,发现刀具振动方向以轴向为主且振动幅度满足要求。     

超声振动钻削声学系统的设计研究

通过对超声振动钻削系统的理论分析，给出了不同的纵向振动圆锥形变幅杆设计公式，分析了面积系数与谐振长度、位移节点、极大值点、放大系数和形状因素之间的关系。用实例分析了几种变幅杆的不同点，并指出设计超声振动钻削声学系统时推荐采用复合变幅杆。     

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。     

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.