机器结构焊缝强度设计的若干经验法则

机器结构焊缝设计的特点焊缝强度通常是相对于母材强度而言。当焊件的两块钢板厚度不相等时,以其中薄件的板厚作为焊缝强度计算的依据。所谓焊缝设计中的等强度原则,是指焊缝强度等于其中薄板的强度。焊缝的等强度设计原则,适用于桥梁、建筑等按强度条件设计的工程结构。机器结构(指机体、底座、床身和立柱等基础大件)的设计不同于桥梁、容器等工程结构设计,它不是按强度条件,而是按刚度条件设计的。所以,机器结构的形状不仅复杂,而     

S30MnH活塞杆化学成分对力学性能的影响分析

活塞杆一直存在两端强度差异大、强度超标等问题,为此随机抽取近年来试样进行化学分析,分析C含量、C偏差、C当量对强度的影响。通过分析可知,强度随C含量的变化而变化,但是在C含量、C当量相同的情况下,强度差异仍然较大,因此C含量不是影响强度的唯一因素。     

涂层结合强度研究现状与发展

综述了近年来国内外针对不同性质涂层所采用的结合强度测定方法,发现涂层结合强度测定方法应根据涂层厚度、涂层硬度、涂层功能等特征来选定。从弹性断裂力学角度分析了相关的结合强度理论模型,得出了结合强度的计算公式,总结了提高涂层结合强度的各种途径,阐明了涂层结合强度的研究现状和发展趋势。     

热变形参数对316L/Q370qE复合板结合强度的影响

通过Gleeble-3800热压缩试验模拟316L/Q370qE复合板轧制,并借助拉伸试验、硬度试验、组织分析等手段,研究了变形量、变形温度、变形前保温时间等参数对界面结合强度的影响规律。结果表明:随着变形量的增加,结合强度逐渐升高,变形量大于20%时,结合强度升高趋势变缓;随着变形温度的升高,结合强度先升高后降低,1100 ℃与1250 ℃时结合强度相差不大;随着保温时间的延长,结合强度逐渐降低。     

等强匹配焊接接头的特征及界定方法

运用蒙特卡洛方法对10Ni5CrMoV钢焊接接头强度匹配系数分布进行了研究,提出等强匹配焊接接头的界定方法.计算结果表明,10Ni5CrMoV钢焊接接头的等强匹配特征明显,等强匹配概率为48.11%,低强失配和超强失配概率分别为47.55%和4.34%;强度匹配系数均值偏下限,为0.955;由于母材强度数据的标准差比焊缝要大,约为1.54倍,从而使得强度匹配系数离散度较大;此外,焊接接头强度匹配系数小于0.86的概率为2.96%,可能会导致焊接接头产生冷裂纹.     

旋压技术在等强度钢制车轮制造中的应用

介绍了等强度钢制车轮旋压成形对旋压机和工艺的要求及两种等强度钢制车轮旋压机.等强度钢制车轮是一种通过优化车轮截面几何尺寸,用变截面代替等截面结构,使应力大的部位截面厚,应力小的部位截面薄的无内胎车轮,具有质量轻、强度高、安全性好等优点,是具有广阔市场前景的新型车轮.变截面结构是通过旋压工艺实现的.旋压技术的进步为这种新型车轮的大量生产提供了可靠的装备和工艺保障.     

保护渣空心颗粒微观结构对其常温强度的影响

由于保护渣空心颗粒常温强度不足等原因,在储存、运输过程中会发生部分粉化,对其生产使用造成了一定的影响。为了研究空心保护渣颗粒的微观结构对其常温强度的影响,采用扫描电镜、保护渣颗粒强度检测仪等设备对不同粒径的保护渣进行了微观结构和常温强度检测对比分析。结果表明,粒径在0.3～0.6 mm间的保护渣颗粒强度比其他粒径的常温强度好,提高空心颗粒保护渣中0.3～0.6 mm粒径的比例可有效防止保护渣在运输储存过程中的粉化,对保护渣的生产使用具有指导意义。     

齿形组合凹模等强度分析及优化

文章介绍了运用统一强度理论、等强度分析和有限元模拟对齿形冷挤压凹模进行优化设计的过程。齿形凹模不能直接应用Lamé公式进行等强度分析,可先将齿形凹模简化为常用的直圆筒型组合凹模,再应用Lamé公式进行等强度分析,确定组合凹模的分层半径和过盈量。根据结构参数建立有限元模型进行等效应力分析,以组合凹模各层达到其许用应力值为目标,调整过盈量,达到优化设计的目的。     

中等厚度板埋弧焊焊缝研究

采用不同碳当量的焊丝WGX1和WGX2等对多种中厚板进行了埋弧焊试验及焊缝拉伸试验,对接焊缝强度与焊丝熔敷金属强度相比有明显的变化,建立了强度的变化量与焊丝及母材的碳当量差值的关联性,为控制中厚板埋弧焊缝强度奠定了基础。     

基于UG的落料模起吊工况强度分析

降低模具闭合高度可减轻模具质量,并可增加模具叠放层数,但必须进行模具强度验证,基于UG 11的Pre/Post模块,通过前处理和后处理等过程,对降低模具闭合高度后的落料模结构在起吊工况下进行分析,结果表明,位移-节点、应力-单元等关键强度指标均符合强度要求。     

聚丙烯酸盐粘结剂砂温芯盒制芯工艺

以自行研制的ＤＨ－０２型聚丙烯酸盐树脂为芯砂粘结剂，进行了温芯盒法制芯工艺的研究，测定了芯砂的常温和高温强度，发气量，可使用时间，抗吸湿性等，并作了浇注铸铁件的验证。     

Significance of quenching stress in the cohesion and adhesion of thermally sprayed coatings

In thermal spraying, molten particles strike a solid surface, where they are flattened and quenched within a very short time. Considerable in-plane tensile stress on the order of 100 MPa can develop within each splat during quenching after solidification because thermal contraction of the particle is constrained by the underlying solid. Ni-20Cr alloy and alumina powders have been plasma sprayed in air onto steel substrates that were maintained at about 473 K. The influence of spraying conditions such as spray distance on the magnitude of the quenching stress have been studied by measuring the curvature of the substrate during spraying. Mechanical properties such as Young’s modulus and bend strength of the deposited coatings have also been measured. A strong correlation was found between the quenching stress and the strength of Ni-20Cr coatings, which suggests that the strength of interlamellar bonding limits the quenching stress at such temperature. Presented at ITSC ’92, June, 1992, Orlando, Florida.     

利用PA的结晶原理解决塑件常见成型缺陷

对尼龙基材(PA)的结晶速度、顶出部位的强度进行了应用分析,依据材料的性能进行改模或调整工艺,解决了因材料的结晶速度不同,导致成型过程中同一副模具换不同品种的PA时,用同一周期生产,却产生顶穿、发白、起皮、熔接痕强度不够等问题。     

Mapping the compaction and sintering response of tungsten-based materials into the nanoscale size range

Considerable knowledge exists on processing tungsten powders over a broad particle size range. Published data and processing models have been combined for tungsten powders ranging from 20 nm to 18 μm to build a response model for press-sinter processing. The model predicts apparent density, green density, green strength, sintered density, sintered grain size, and product properties such as strength, hardness, and wear resistance. Further, the model isolates several problems as particle size decreases that will require changes in how tungsten powders are handled, compacted, and sintered. Maps of strength versus processing conditions are generated from the model to direct future efforts toward improved properties using nanoscale tungsten powders. From these findings, new opportunities become evident for press-sinter consolidation of nanoscale powders.     

新型铸造热锻模具钢强韧性本质的探讨

采用微观分析方法探讨了新型铸造热锻模具钢（CHD钢）的强韧化机理,研究表明,CHD钢具有较高的强韧性和高温稳定性,其组织为具有高密度位错的板条马氏体和贝氏体的复合组织,板条界连续分布着许多薄膜状残留氏体,CHD钢在回火过程中弥散析出细小的碳化物V3C4,Mo2C,这些亚结构的配合是CHD钢具有高强韧性的本质。     

偶联剂KH-550在改性环氧树脂胶粘SiC耐磨涂层中的应用

为了获得改性环氧树脂粘接SiC颗粒钢基表面复合涂层的优异性能,试验采用偶联剂KH-550来改善材料的复合界面.结果表明:一定量的偶联剂KH-550可显著地提高改性环氧树脂胶粘SiC耐磨涂层的粘接强度(包括剪切强度、拉伸强度及弯曲强度)及耐磨性,并确定出了改性环氧树脂胶粘SiC耐磨涂层中KH-550的最佳加入量为3.3%及较好的使用方法为迁移法.     

表面纳米化对GH4049镍基高温合金性能的影响

超声喷丸(USSP)处理工艺在GH4049镍基高温合金表面制备出了纳米表面晶层,分析了不同超声喷丸强度和喷丸时间对其屈服强度、抗拉强度、显微硬度的影响,并通过试验分析了经表面纳米化后试件的残余应力分布.研究结果表明,喷丸时间的增加对材料强度的提高无直接关系,且随喷丸时间的增长,由于材料表面的损伤,会使材料的强度降低.经超声喷丸处理后,显微硬度较未处理试件明显提高,试件表面形成大约0.2mm厚度的压应力层,最大压应力远超过材料的屈服极限δs.     

Rigid-plastic and elastic-plastic finite element analysis on the clinching joint process of thin metal sheets

This article describes the joining of thin metal sheets by a single stroke clinching process. Elastic-plastic and rigid-plastic finite element analysis were applied by employing Coulomb friction and constant shear friction in order to investigate the behavior of the clinch joint formation process. Four process variables, such as die diameter, die depth, groove width, and groove corner radius were selected to investigate the parametric effect on the clinch joint. The strength of clinch joints were evaluated by examining the separation strengths, such as peel strength and tensile shear strength, respectively. A failure diagram was constructed that summarizes the analysis results. The simulation results showed that die diameter and depth were the most decisive parameters for controlling the quality of the clinch joint, while the bottom’s thickness was the most important evaluation parameter to determine the separation strengths.     

C/SiC复合材料用莫来石/硅酸钇双层涂层的抗氧化性能研究

针对C/SiC复合材料的防氧化要求,在材料表面通过等离子喷涂法制备了莫来石/硅酸钇的双层涂层,对涂层的形貌、组成和结构及其与基底的结合强度进行了表征,开展了1500℃、1h静态空气氧化实验,对抗氧化涂层的结构演变进行了分析,并对C/SiC复合材料氧化实验前后的质量和力学性能变化进行了研究。结果表明,莫来石/硅酸钇双层涂层抗氧化作用较好,涂层C/SiC复合材料的强度保留率达95.3%。     

The Determination of the Porosity of Electro Deposits

Newly developed steels with tensile strength of up to 150 Ions p.s.i. are shown to fail by embrittlement under constant load, well below their nominal ultimate strength. This effect is usually attributed to hydrogen embrittlement. The paper describes a programme of tests on one specific type of ultra-high tensile steel. Small specimens (tensometer No. 12), notched in their centre, are subjected to constant stress in specially designed rigs. Various types of electrolytic or vapour-deposited coatings are applied to the specimens. The tests are conducted in non-corrosive or corrosive conditions. It is concluded that with stresses of the order of 80% of fracture strength, specimens electroplated with cadmium generally fail in 10–100 hr in the absence of corrosion, whilst zinc vapour-coated specimens do not appear to be sensitive to delayed fracture. Nickel-chromium plated specimens give inconsistent results, whilst nickel-plating usually behaves in much the same way as zinc vapour- coated specimens.

If a corrosive agent, such as 3% sodium chloride spray, is applied, rapid failure of uncoated and coated specimens takes place at stresses of approximately 70% of the notched fracture strength. Of the metal coatings, cadmium-plated specimens are most sensitive, nickel-plated specimens the most resistant; hard silicone lacquer show the best results. There is evidence that failure is related to the mechanism of corrosion reaction rather than to the extent of corrosion. Other corrosive agents, such as tap water or solutions of ammonium carbonate, do not cause this accelerated failure even if severe corrosion takes place.