P92钢焊接接头的组织和性能研究

通过硬度试验、冲击试验、断口扫描和金相组织观察,研究了P92钢焊接接头的性能、组织特点及关系。结果表明,焊缝的硬度比HAZ的大,冲击功比HAZ的小;二者在断裂形态上的差异导致了两个部位对冲击吸收功的不同;焊缝金属组织中形成的奥氏体枝晶是造成焊缝金属的韧性明显低于HAZ的主要因素之一。     

42CrMo钢磨煤机撑杆断裂原因分析

采用金相试验、化学成分分析、力学性能试验和断口扫描电镜试验等方法,对某电厂磨煤机撑杆断裂原因进行分析。结果表明：母材金相显微组织含有较粗大马氏体,拉伸性能劣化与冲击韧性差,导致磨煤机撑杆在运行时发生准解理脆性断裂。     

34CrNiMo6材料低温韧性研究

近年来34CrNiMo6材料作为1.5MW以上风力发电机组主轴材料之一在欧洲广泛应用,国内尚未给予其在低温环境的韧性性能表现充分的研究和证实。本文通过测试在-100～25℃区间34CrNiMo6材料的强度、塑性、冲击韧性、断裂韧性性能数据,并对数据结果分析和讨论。得出：在-100～25℃范围,34CrNiMo6的光滑和缺口拉伸强度增加,塑性变化不明显,缺口敏感系数无明显变化。韧-脆转变温度为-45℃左右,上平台功为153 J左右,下平台功为27 J左右。断裂韧性对应的韧脆转变温度为-97℃。当测试温度高于-80℃时,断裂韧度数据分布在断裂韧度-温度关系曲线的上平台,断口为韧性断裂形貌。     

高强结构钢Q420低温断裂韧性研究

针对不同板厚的高强结构钢Q420角钢进行了不同温度下的断裂韧性试验,计算得出了试样的裂纹尖端张开位移指标。试验结果表明,温度对结构钢材的断裂韧性具有明显的作用,钢材的断裂韧性随着温度的降低显著减小,断裂方式也由延性断裂转变为脆性断裂。总体趋势上来讲,试样厚度的增大也引起钢材断裂韧性的降低。因此,在重要工程设计、选材及安全分析时,应充分考虑温度和厚度对结构断裂行为告白影响。     

9%～12%Cr马氏体耐热钢母材及焊缝的硬度控制

对P91钢母材及焊缝硬度与强度、冲击功及断裂韧度的关系进行的试验研究表明,当硬度低于180 HB时,P91钢母材及焊缝的强度不满足相关标准要求;当硬度高于270 HB时,焊缝的冲击功不满足相关标准的要求。试验结果与9%～12%Cr马氏体耐热钢的硬度控制判据相吻合。     

P91主蒸汽管道焊缝断裂韧度与其它力学性能的关系

文中对P91钢两类焊缝的拉伸、冲击、硬度，特别是断裂韧性进行了试验研究。结果表明：强度、硬度高，冲击韧性低的R焊缝具有低的断裂韧度，强度、硬度低，冲击韧性高的D焊缝具有高的断裂韧度；R焊缝的低韧性主要与其晶粒粗大、网状晶界及焊接过程中焊接线能量和电流偏大有关，而D焊缝的低强度与高的断裂韧度则与焊后二次回火时温度过高有关。对于R焊缝，用厚度12mm的三点弯曲(SEB)试样测得的条件Kic(kq)与厚度25mm的紧凑拉伸(CT)试样测得的有效Kic基本一致。     

稀土对60si_2Mn钢韧化机理的影响

本文研究稀土对60Si_2Mn钢韧化机理的影响并确定了稀土加入工艺。发现稀土对提高60Si_2Mn汽车钢板弹簧钢的断裂韧性有显著效果;对于提高冲击韧性特别是低温下的冲击韧性亦有明显效果;研究结果还表明:稀土加入60Si_2Mn钢中不仅能脱硫还可以有效地控制和改变硫化物夹杂的类型、形态与分布。文中“稀土”,在钢锭中加的为混合稀土金属,炉中及包内加入的是稀土1#合金。     

金属旋压加工工艺的研究

根据金属灯罩旋压加工工艺的特点,建立金属旋压工艺参数的数学模型,通过对减薄率、旋压力、旋压轨迹切点等关键数据的计算,得到旋压加工工艺参数,并经过多次试验,对金属灯罩加工旋压刀路轨迹进行对比分析。结果表明:通过调整减薄率、旋压力、旋压轨迹切点等参数,可以建立优化的旋压加工工艺和加工轨迹路线。     

Optimization of process parameters with Taguchi method for nano machining CaF2 crystal

ABSTRACT

Owing to the outstanding optical characteristics of calcium fluoride (CaF₂) crystal, this material is a great choice for ultraviolet lenses and windows. Due to its softness and brittleness, it is difficult to nano machining CaF₂ crystal. Fixed abrasive polishing technology, one of nano machining directions, was adopted to process CaF₂ crystal. Experiments were designed using Taguchi method to explore the effect of pressure, plate speed, slurry flux and slurry pH on material removal rate and surface roughness in fixed abrasive polishing of CaF₂ crystal. The optimum polishing parameters for material removal rate are discovered to be pressure 10 kPa, slurry pH 11, plate speed 50 rpm and slurry flux 40 ml/min. And they are pressure 6.7 kPa, slurry pH 9, plate speed 40 rpm and slurry flux 60 ml/min for surface roughness. The analysis of variance shows that pressure 52.6% and plate speed 25.4% are the most significant parameters that affect material removal rate, while plate speed 51.3% and slurry flux 32.0% are the two main factors for surface roughness. The most significant factor and the contribution of each parameter for MRR and surface roughness were obtained in nano machining process, respectively.     

Research on Process Optimization of Ag-IPMC

Abstract

In this paper, Ag-IPMC with special fabrication technology feature were investigated to clarify the effects of secondary electroless plating process with different times on the micro-morphology and electromechanical response characteristics of IPMC. This experiment explores the relationship between the preparation process and performance characterization of Ag-IPMC. Ag-IPMC with specific morphology were prepared according to the principle and method of electroless plating. The relationship between preparation process, micro-electrode morphology and output force performance was observed and discussed, and the ultimate displacement and output of Ag-IPMC under direct current at different voltages were investigated. The process parameters of Ag-IPMC were optimized, supplying a foundation for the practicability of Ag-IPMC.     

Influence of Turning Parameters on Turning Performance of Ultra-High Strength Steel

Abstract

In order to improve the turning process performance of ultra-high strength steel in aircraft landing gear, the effects of different cutting parameters on cutting force and surface roughness of A100 steel and 300M steel were studied by orthogonal test. Multivariate linear regression analysis of cutting parameters was carried out, and empirical formulas of three-dimensional cutting force and surface roughness were established. The results show that when cutting A100 steel, feed has the greatest impact on cutting force. When turning 300M steel, back cutting depth has the greatest impact on cutting force. For surface roughness, back cutting depth has the greatest impact on the two materials, and spindle speed has the smallest.     

Experimental Research on Turning of Superalloy GH4169 under High Pressure Cooling Condition

Abstract

Superalloy GH4169 possesses excellent high temperature strength, thermal stability, and thermal fatigue, and is widely used in aerospace and other fields. However, it is a typical difficult-to-cut material owing to its poor thermal conductivity, high plastic toughness, severe workpiece hardening, and difficult chip breaking. In this study, high pressure cooling was used for GH4169 cutting test. The effects of high pressure cooling on the cutting force, chip morphology, and tool wear were analyzed, which can provide technical support to achieve high efficiency turning of GH4169.     

混凝土起裂韧度与断裂韧度的关系

本文首先简单地介绍了混凝土双Ｋ断裂准则,通过对不同试件形式、不同试尺寸、不同厚度、不同体积、不同初始裂缝长度下起裂荷载、起裂韧度与最大荷载、断裂韧度关系的统计分析发现;起裂韧度与断裂韧并不是两个独立的材料参数。在混凝土软化模式一定的前提下,由其中的一个可以方便地推出另一个。     

Patterning of noble metal electrodes and oxygen barriers by CMP

Abstract

In this study the chemical mechanical polishing (CMP) of Iridium and Iridium Oxide has been investigated. The results show that it is possible to polish this highly inert noble metal and its oxide with removal rates and selectivities that are satisfactory for damascene processes in semiconductor manufacturing. All slurries are based on commercially available abrasives and chemicals. Using blanket wafers, two slurry systems have been systematically studied. Concentration variations of abrasive as well as oxidizer and base have been investigated for Iridium and Iridium oxide, respectively. The dependence of the removal rate on polishing parameters such as time, pressure and rotational speeds have been investigated. Iridium and Iridium oxide removal rates up to 50 and 260 nm /min with selectivities to SiO₂ up to 30:1 and 50:1 could be reached, respectively. The polishing processes presented here allow for the first time the implementation of noble metal damascene processes in semiconductor manufacturing.     

Effects of SiC Particle Volume Fraction on Microstructure and Mechancial Properties of SiCp/6061Al Composites

Abstract

The SiCp/6061Al composites with volume fractions of 10%, 20%, 30% and 40% were prepared by power metallurgy method. The effects of the volume fraction of SiCp on microstructure and mechanical properties were studied by means of phase analysis, microstructure observation, hardness test, friction test, wear and tensile test. The results show that the SiC particles distribute uniformly in the matrix and the interface bonding between the matrix and the reinforcement was exceptional. With the increase of the volume fracture of SiC particles, the distribution uniformity decreases, the hardness increases, the elongation decreases, with the tensile strength and wear resistance were increasing before slowly decrease. If the volume fracture of SiC particles is 30%, the comprehensive mechanical property is best that the hardness is 97.9 HV, the tensile strength 243?MPa, the elongation is 2.9% and wear rate is 1.21?×?10^–5?g/m.     

Ferroelectric electrode interactions in BaTiO3 and PZT thin films

Abstract

We have studied ferroelectric thin films deposited by sol-gel processing onto non-noble metal substrates. The results obtained indicate that by careful control of processing conditions, ferroelectric materials can be deposited onto these substrates, although interdiffusion between the metal and the ferroelectric can significantly degrade the ferroelectric properties of the materials. The effects of this interdiffusion are demonstrated and possible implications of ferroelectric-electrode interactions for fatigue in ferroelectric materials are discussed.     

P91主蒸汽管道高硬度和低硬度焊缝性能研究

对P91钢的高硬度和低硬度焊缝的冲击功、硬度、断裂韧度和持久强度进行了试验研究,结果表明:硬度高、韧性低的R焊缝具有高的持久强度;硬度低、韧性高的D焊缝具有低的持久强度。材料持久强度的高低与部件的蠕变寿命密切相关。     

粗骨料含量对环氧树脂修复混凝土断裂性能的影响

通过开展环氧树脂修复混凝土梁的三点弯曲断裂试验,对比研究了混凝土修复前后的断裂性能,分析了粗骨料含量对双K断裂韧度和断裂能的影响.结果表明:环氧树脂修复可大幅提升试件的最大承载力,且临界裂缝口张开位移几乎不受影响.修复后混凝土的断裂性能可得到有效恢复和提升.其中,粗骨料含量为0(砂浆)、18％、36％和54％时,起裂韧...     

Water treeing in binary linear polyethylene blends: the mechanicalaspect

Water treeing tests were performed on low density polyethylene (LDPE) and four different binary blends of sharp linear polyethylene (LPE) fractions (M_w=2500 and 76000), which were either quenched in air from the melt or isothermally crystallised at 123°C. Although the morphology and initial mechanical properties of the materials tested were significantly different, the vented tree growth characteristics were similar for all of them. This is in disagreement with the electromechanical models of water treeing, which correlate water tree growth with the fracture toughness of the material. Time to breakdown distributions were also similar for both LDPE and the binary LPE blends, which indicates that, regardless of the initial material morphology and the actual structure of water trees, the length of water trees is one of the controlling factors in insulation failure. The visible light image of water trees in LPE blends did not disappear upon drying as it usually does in LDPE and crosslinked polyethylene insulation     

不同含水率混凝土断裂韧度试验研究

混凝土结构常处于不同湿度状态,而不同湿度(含水率)对混凝土断裂特性有显著影响。采用电热恒温鼓风干燥箱对C15、C20、C30混凝土三点弯曲梁试件进行干燥,将干燥后试件分别浸泡3、10、24、48、72、120、240 h,使试件达到不同含水率状态后,进行三点弯曲梁断裂试验,并建立不同强度等级混凝土断裂韧度关于含水率的预测公式。研究结果表明:含水率对混凝土断裂韧度影响明显,随含水率增大而降低,饱和混凝土较干燥状态最大降幅达57%;实测P–CMOD关系曲线明显存在起裂前的线弹性阶段、裂缝稳定扩展的非线性阶段、裂缝失稳扩展阶段,随含水率的增大,线弹性阶段逐渐变短、稳定扩展阶段加长、失稳扩展阶段曲线下降趋势变缓,且临界荷载对应的切口张开位移和加载点位移均减小,表现为试件变形能力降低、韧性减弱。