过度弯曲和校正弯曲在弯曲成形上的应用

对弯曲半径大的零件在弯曲成形中出现的回弹进行了工艺分析，并结合实例，较为详细地介绍了利用过度弯曲和校正弯曲的方法，设计了可控制和抵消弯曲件回弹的系列弯曲模具．     

线圈弯曲模设计

零件工艺分析图１是线圈零件，材料为１Ｃｒ１２Ａｌ４，料厚ｔ＝２ｍｍ，由于弯曲部分ａ、ｂ不等高，一般用２次弯曲成形。为了保证尺寸，第２次弯曲ｂ部要以第１次弯曲的ａ部作定位，实行不对称单角弯曲，工艺性不佳。鉴于上述情况，设计了１副斜楔式弯曲模，将２个部分的弯曲１次成形。图１线圈零件如图１所示，结构简单，尺寸精度不高，只需要用落料、弯曲工序即可完成。该零件落料工艺性尚好，只是弯曲部分有２个不———————————————————收稿日期：１９９８年１２月３０日等高的弯曲面，用普通弯曲模很难１次成形。为…     

侧向弯曲模设计

介绍一种利用斜楔进行侧向弯曲的模具结构,分析比较了现用弯曲模的不足、讨论了其有关尺寸和参数的设计和计算,对弯曲部圆弧状的零件有一定参考价值。     

槽板弯曲工艺及模具设计

对槽板零件及其工艺性进行了分析,详细计算了该零件的毛坯长度、弯曲回弹量、弯曲力等工艺,参数,根据弯曲工艺的分析及其参数的计算结果,叙述了该零件弯曲模具的设计结构,说明了模具的工作过程,最后阐述了该弯曲模具的设计经过。     

圆管拉伸弯曲模

<正> 在圆管弯曲时,由于加工方法和加工设备的不同,而导致最小弯曲半径也不相同。所以对各种圆管零件弯曲时,为保证弯曲件的使用需要,对管件强度,外观的加工要求,须采用相应的加工措施来完成。其零件如图1所示。     

弯曲机专用模具设计

弯曲机专用模具设计陕西蔡家坡西北机器厂（７２２４０５）徐领延１引言图１所示零件为彩色电视机所用管座上的零件──放电柱，材料为Ｈ６２丝料，直径该零件需求量很大，每年约５００万只。原工艺路线为：丝料校直切断→一次弯曲→二次弯曲。这样效率低，远不能满足生产...     

上窄下宽弹簧片零件弯曲成形工艺

介绍了上窄下宽弹簧片零件的弯曲成形工艺，并介绍了成形该零件的两副关键模具的结构设计和工作过程。     

零件上小于90°角的弯曲

介绍了具有小于90°角(锐角)零件的弯曲方法及卸料方法,通过特殊的模具结构或适当调整零件的弯曲工艺,使零件在成形小于90°角时既可以用单工序模具成形,也可以用级进模成形。从模具结构、模具工作原理以及零件成形工艺上分析了它们各自的成形特点以及适用场合。     

旋转弯曲

模具设计者和金属材料冲压者都知道,金属材料弯曲尚存在各种问题,特别是在大批量生产和把零件的一致性作为关键因素时,则更是如此。从加工出合适的弯曲角度和减少零件的变形到减轻所需的弯曲载荷和在弯曲过程中夹紧零件出发,传统的 V 型和消除回弹弯曲方法都不能令人满意。然而,旋转弯曲却是解决问题的一种可行方法。     

托架弯曲成形模设计中摩擦的避免和利用

经过对零件工艺性能的分析，确定了零件托架的成形工艺方案，在弯曲成形模具设计中采用了独特的1／4圆柱机构。在下压弯曲过程中利用滚动摩擦代替滑动摩擦，减小弯曲过程中摩擦的有害作用，在脱模过程中又利用了摩擦力进行无滑动摩擦脱模，保证了零件表面精度要求，关键是减小了模具磨损，提高了模具寿命。     

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.     

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.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。