单边缺口拉伸试样的断裂韧性计算方法对比

在工程临界评估（engineering critical assessment）中,裂纹尖端张开位移（CTOD值）的精确性将极大影响设计安全裕度与服役寿命.单边缺口拉伸（SENT）试样裂纹尖端的应力应变场与管道在实际服役状况下相似,被认为比较适用于测量管道CTOD值.目前有几种针对SENT断裂韧性的计算方法,但是并没有统一的标准.文中采用API X70管线钢,进行SENT试样断裂韧性试验并对比各计算方法与双刀口法之间的区别.采用Crackwise 4.0评估了不同计算方法得到韧性值对裂纹极限尺寸的影响.结果表明,几种CTOD计算方法相较于双引伸计法都有较大误差,断裂韧性的精确度对于ECA评估极限裂纹尺寸有极大影响.     

基于网格分析技术的汽车板选材应用

利用网格分析技术测量了右后侧围后连接板的应变分布,并将所测的应变值与试验测量的材料成形极限曲线和相应的安全裕度成形曲线相对比,分析板材的成形性能,确定零件生产的稳定性和安全裕度。试验结果表明,网格分析技术可直接反映出测量区域的变形行为,为设计选材提供定量的判定依据。     

石油产品碱性氮测定结果不确定度的评定

试验依据SH/T0162-92(2006)《石油产品中碱性氮测定法》测定了蜡油试样中的碱性氮,对测量过程重复性、所使用的计量器具、标准溶液的浓度等影响测量结果的不确定度分量进行分析,通过对其进行分析、计算及合成,得知重复性测定及滴定过程消耗标准溶液体积对不确定度影响最大。     

DZ125定向凝固涡轮叶片不同部位力学性能研究

从DZ125定向凝固空心涡轮叶片割取小尺寸试样,并进行两种温度(980℃和1050℃)下单轴拉伸试验以及980℃、219 MPa下的蠕变持久试验。作为对比,同时从DZ125板材上割取小尺寸试样并进行试验。结果表明,相比于标准试件,从叶片上取得的试件的拉伸极限强度明显降低,持久寿命时间也大为缩短;与板材试件相比,从叶片上取得的试件拉伸极限强度和持久寿命也较低,表明涡轮叶片存在局部力学性能弱化。采用标准试件试验数据设计定向凝固涡轮叶片并不能准确表征叶片局部力学性能。小试样试验可作为研究涡轮叶片不同部位力学性能差异的可行方法。     

试样的质量检验

试样质量直接影响着试验数据的准确性和可靠性。因此,对于加工的试样必须进行严格的质量检验,以保证成品试样的尺寸、状态、粗糙度等符合标准规定及试验的要求。 (1)几何尺寸检验:几何尺寸包括长度、直径、弧度、平面度、不直度、不平度、不圆度及椭圆度、不圆柱度、锥形度、鞍形度鼓形度、弯曲度,以及表面形位公差等。测量试样尺寸应选用适宜的计量工具,对于特殊的尺寸需配备专用的工具,如投影仪、偏摆仪、工具显微镜、精密平板、刀口平尺、半径样板等。各种量具都应经过计量检定。测量时应仔细认真的读取读数,必要时要重复测量。为保证成品尺寸测最应在每道工序后逐项进行检验。     

基于网格应变技术的后轮罩冲压开裂原因分析及改进措施

利用网格应变技术,对热镀锌高强IF钢H220YD+Z材料的成形极限性能和对后轮罩危险区域的成形极限图进行分析,确定4个高应变危险区域的应变分布和成形安全裕度。通过改善材料的应变硬化指数n值和优化后轮罩危险部位的模具零件圆角,提升了成形极限曲线FLC和降低了后轮罩的应变大小,危险区域成形安全裕度都增大到10%以上,满足了冲压企业对安全裕度的要求,保证了后轮罩零件的冲压质量和生产稳定性。     

AM50A压铸件孔洞与力学性能关系的研究

针对压铸过程中气体卷入形成的孔洞与压铸件力学性能之间的定量关系进行了研究.在压铸件不同厚度的部位取样,测试了所取试样的力学性能,采用阿基米德方法和图像定量系统分别测量了取样的孔洞体积分数和最大尺寸,探讨了它们和力学性能之间的关系.并利用多元线性回归的数学统计方法,提出了AM50A压铸件中孔洞体积分数和最大尺寸与力学性能的定量关系.     

国产轿车用冷轧薄钢板的成形性能评价

就评价国产轿车用冷轧薄钢板成形性力学性能参数做了详细的分析；并就轿车零件冲压成 的特点，将材料的ＦＬＤ图和冲压件应变图合成为零件应变极限图，从而对零件的冲压安全裕度进行评价，用于指导国产轿车用冷轧薄钢板的冲压生产。     

GH4169高温合金圆棒试样室温拉伸试验的测量不确定度评定

根据金属材料拉伸试验的原理和方法以及计算力学性能指标的公式建立数学模型。随后按相关标准和测量不确定度评定程序确定GH4169高温合金圆棒试样室温拉伸试验的测量不确定度来源及相应的不确定度分量。采用A类和B类不确定度评定方法评定拉伸性能的合成不确定度。以95%的置信度评定了GH4169高温合金圆棒试样拉伸试验的测量不确定度。     

时效制度对7055铝合金弯曲蠕变时效成形的影响

采用自制的单曲率弯曲蠕变成形装置,针对7055铝合金板材进行系列蠕变时效成形试验。测得不同时效制度下试样的回弹量、力学性能与微观组织,并与人工时效试样进行了对比分析。结果表明,回弹量随着时效时间的延长和时效温度的升高而降低,但回弹极限基本不受影响;弯曲蠕变时效试样较人工时效试样具有较高的强化效果和电导率;弯曲蠕变时效后试样的晶粒尺寸和形状与人工时效试样无明显区别,但其析出相则比人工时效试样细小和密集。     

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。