特种车排气消声器多场研究及结构性能分析

针对某型危险品运输车的排气消声器壳体温度分布情况和外激励是否会引起消声器共振而致使其开裂的问题,运用FLUENT软件对某消声器进行内流场及温度场数值分析,用AR320+非接触式红外线测温仪对消声器壳体温度进行测量,最后基于ANSYS Workbench以数值分析结果作为预应力对消声器进行模态分析。研究表明:消声器壳体温度仿真值与试验值的误差在5.92%内,间接验证了数值分析的精确性;当尾气流速为6.24 m/s时,消声器内部存在涡流,会导致噪声产生;路面激励27.8 Hz和发动机激励106.67 Hz均低于消声器的1阶固有频率111.01 Hz,不会引起共振,但消声器筒体左侧面变形量较大,为18.06 mm,为该消声器的薄弱位置。研究结果可为特种车辆消声器的改进设计提供了参考。     

旁入穿孔管消声器压力损失研究

针对旁入穿孔管消声结构的应用问题,利用Fluent软件分析了不同入口流速、穿孔直径和穿孔率下,该类消声单元压力损失的变化规律。通过对仿真结果的分析,将旁入穿孔管消声单元衍生为双旁入穿孔管和三旁入穿孔管消声器,研究衍生结构与原结构在相同穿孔直径和穿孔率这两种情形下的压力损失变化关系,结果表明,双旁入穿孔管的性能优于其他两者。通过实验测试了带有旁入穿孔管消声结构的复杂消声器,仿真和试验结果发现,在相同条件下,压力损失的仿真结果为5.75 kPa,实验结果为6.1 kPa,误差为5.73%,验证了CFD仿真的计算精度。     

90°竖直弯管的液固两相流冲刷腐蚀模拟

以液固两相流条件下的90°竖直弯管为研究对象,建立冲蚀模型,利用ANSYS-Fluent软件对A、B、C、D四种流向的弯管进行冲刷腐蚀数值模拟。同时建立室内冲蚀试验平台,分析了颗粒入口流速、粒径和质量流量三个参数对四种流向条件下弯管的冲蚀破坏规律并与模拟结果进行对比。结果表明:试验结果与模拟结果基本吻合,入口流速和粒径对弯管的冲蚀影响最大;且随着颗粒入口流速的增大,流场中开始出现二次流。当颗粒入口流速较小时,A型流向条件下弯管的冲蚀破坏最严重;而当颗粒入口流速较大时,由于二次流加剧冲刷,B型流向条件下弯管的冲蚀破坏最严重,A型、C型流向条件下的次之,D型流向条件下的弯管冲蚀破坏最小。     

插入管结构要素对消声器性能的影响研究

针对某型消声器，通过仿真软件GT-Power，分析插入管消声器排气入口直径(43~63 mm)和进气管直径(38~58 mm)的耦合作用对消声器压阻损失的等效分布规律和等效压阻损失下的传递损失变化规律。研究结果显示：插入管单元耦合下的压阻损失变化率在压阻损失较高和较低的区域较大。在插入管单元耦合对消声器压阻损失影响中，等效压阻损失越大，曲线在中高频上的传递损失变化范围也越大；在等效压阻损失较小的区域，基本结构单元对等效压阻损失影响更为敏感；等效压阻越大，其传递损失变化范围也越大，在中频段620~850 Hz更为明显。最后建立综合声学性能和空气动力性能的评价体系，得到了基于边界条件较原消声器性能更优的结构参数组合区域。     

贵金属催化剂应用之一

为减少环境污染,保护大气清净,消除汽车排放出来的一氧化碳,碳氢化合物,氮氧化物等有害气体,在汽车发动机排气管消声器中装入蜂窝型催化剂,可以使一氧化碳与碳氢化合物氧化成无毒的二氧化碳和水,氮氧化物分解成氮和氧,而且能减少噪声.     

宽展挤压模具正交试验研究

宽展模具的结构参数(入口宽度、出口长度、宽展模的高度、工作带的基准长度、模孔的位置)对SDV值(流速均方差值,该值越小,挤压过程越稳定)存在影响,在模具设计中,更重要的是确定这些参数对流速均方差的影响。针对上述问题,本文在数值模拟的基础上,采用正交试验法,对铝型材产品FD-Awdd-7生产中所用的宽展模具进行了研究,在这些模具结构参数中,对挤压流速均方差有显著的影响的参数包括：宽展模的入口长度、模孔位置以及宽展模入口长度与宽展模出口长度的交互作用。     

非规则腔体消声器的CFD仿真研究

异形腔体消声器的空气动力性能是其关键技术指标之一。以一类具有内插隔板的消声器为研究对象,利用计算流体力学(CFD),仿真研究了隔板位置、隔板孔位、隔板孔位面积以及隔板数量对压力损失的影响规律,发现隔板位置和隔板孔位对消声器压力损失的影响与其结构存在密切的关系:孔位面积越大,消声器压力损失越小;孔位相对的情况下,每增加一隔板,消声器压力损失增加2~3 kPa。最后结合速度分布云图,对其压力损失成因进行了分析。研究结果为不规则腔体消声器的设计提供了参考依据。     

新型钢卷运输车

工业钢卷运输中,有常见的连续轨道运输车,也有非连续轨道运输车,轨道断开时,运输车的方案较为复杂。通过对非连续轨道运输车技术方案的调查研究,归纳了其技术特点和利弊,分析了非连续轨道运输车的运动特点,开发了一种新型运输车,有效解决了四轮运输车无法在非连续轨道上行驶的问题,并且克服了现有技术方案的弊端。在结构分析和方案设计中,采用模块设计的方法,把功能和结构进行模块化细分,实现了方案的多样化,可以满足不同工况的生产需求。     

起落架缓冲器阻尼孔特性分析

当飞机着陆下沉速度较快时,油-气式缓冲器因快速压缩会引起缓冲器内部压力剧增和阻尼孔处产生射流现象。为减小缓冲器内部压力和油液流经阻尼孔的流速,以油液入口速度、阻尼孔的孔长、孔径和倒直角为研究对象,通过单因素法对各因素变化引起的缓冲器内压力和流速的变化特性进行分析。通过Fluent软件进行仿真计算,结果表明:油液入口速度越大,缓冲器内部压力和油液流速也越大;孔长对缓冲器内部压力影响较小,对阻尼孔中油液流速影响较大;随孔径减小,缓冲器内压力和阻尼孔中油液流速不断增大;倒直角对缓冲器内压力影响较小,但可降低阻尼孔中的油液流速。研究结果可为缓冲器的优化设计提供参考。     

凸轮精密冷锻成形连皮结构尺寸参数的优化

针对高精度装配式凸轮轴中的凸轮件,本文研究了锻造工艺中的连皮结构尺寸对锻造质量的影响。根据凸轮的结构及尺寸拟定了4种连皮结构,并以双面平底型(Ⅰ型)连皮结构为基础,研究了连皮尺寸对锻造成形载荷的影响,确定了双面平底型连皮结构的最佳尺寸。同时,对比了不同连皮结构的金属流速。结果表明,双球面型连皮结构适合凸轮成形。     

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.     

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.