地角螺栓断裂失效分析

应用扫描电镜、光学显微镜和化学分析等检测手段，对地角螺栓断裂原因进行了探讨。结果表明，由于材质40Cr钢调质处理不当，致使钢的显微组织中存在有沿晶界呈网状分布的铁素体相，晶界严重弱化，造成地角螺栓在拧紧时从应力集中的栓杆与螺帽圆角处沿晶脆断。     

法兰密封螺栓断裂失效分析

通过宏观检验、化学成分分析、拉伸试验、硬度试验、金相检验、断口分析等方法对某批20Cr13钢法兰密封螺栓断裂失效原因进行了分析。结果表明:由于淬火加热温度偏低造成该法兰密封螺栓显微组织中存在大量颗粒状碳化物,部分区域还存在大量带状未溶铁素体,致使该处产生应力集中,并造成螺栓的强度偏低、硬度分散度大,组织存在严重的不均匀性,当螺栓承受正常的工作载荷时,就会在应力集中的法兰密封螺栓螺纹根部沿着铁素体带产生裂纹并疲劳扩展,最终导致螺栓断裂失效。     

焊后热处理对1.25Cr0.5Mo钢在循环水中腐蚀行为的影响

目前有关焊后热处理对1.25Cr0.5Mo钢的腐蚀行为的影响规律尚无文献报道.为此,对正火态1.25Cr0.5Mo钢分别进行淬火、高温回火及调质,模拟不同的焊后热处理,对其金相组织进行分析,并对其腐蚀行为进行电化学测试,研究了不同热处理对1.25Cr0.5Mo钢组织和耐蚀性能的影响.结果表明:正火态1.25Cr0.5Mo钢的金相组织为铁素体和珠光体,淬火组织为板条马氏体,高温回火组织为粗大铁素体和珠光体,调质态组织为均匀的回火马氏体和细小碳化物;淬火处理加速了 1.25Cr0.5Mo钢在工业循环水中的腐蚀速度;高温回火处理对腐蚀行为影响不大;调质处理显著提高了 1.25Cr0.5Mo钢的耐蚀性,是因为调质热处理细化了材料的组织,细化后的组织较晶粒粗大的淬火及淬火后高温回火组织更容易形成氧化物膜,阻碍电极的放电过程,从而获得了较好的耐蚀性能.     

不锈钢丝网断裂原因分析

采用化学成分分析、金相检验、扫描电镜及X射线能谱分析等方法,对不锈钢丝网断裂原因进行了分析。结果表明,应力腐蚀及点腐蚀是引起不锈钢丝网断裂的主要原因,腐蚀介质为临海潮湿大气中的氯离子。断裂丝网材质较差,其化学成分不符合相关技术条件,铬、镍含量偏低,锰含量偏高均使1Cr18Ni9钢抗腐蚀性能下降,其显微组织中出现的较多弥散碳化物颗粒及铁素体大大降低了网丝的抗应力腐蚀和点腐蚀的性能。     

循环水泵泵轴联轴器螺栓断裂分析

采用化学成分分析、室温力学性能测试以及金相检验对某电厂材料为35CrMo钢的循环水泵泵轴联轴器螺栓的断裂原因进行了分析。结果表明:由于该螺栓在热加工成型后未按要求进行调质处理,导致其硬度和强度偏低,加上螺栓头部形状不规则以及螺栓头部与螺杆连接部位没有过渡圆弧造成应力集中,使螺栓在循环水泵运行过程中泵轴轴系的周期性振动下发生疲劳断裂。     

25Cr2MolV钢高温螺栓断裂分析与恢复热处理

利用金相技术、力学性能试验及扫描电子显微镜断口分析研究了M120汽缸25Cr1MoV钢高温紧固螺栓断裂的原因。结果表明螺栓在长期高温工作条件下,网状碳化物沿晶界析出造成材料脆化,并且存在缺口产生应力集中,加上工人拆卸不当使其受到过载冲击力而断裂。经960℃正火、900℃正火及650℃回火的恢复热处理工艺能基本上消除网状晶界,改善微观组织,使螺栓有良好的性能。     

耐候高强度螺栓钢耐典型工业大气环境腐蚀性能研究

为了研究耐候高强度螺栓钢在典型工业大气环境下的腐蚀行为，从自制的10.9级耐候螺栓中取样，与35VB螺栓对比，进行周期为24,48,96,168,216 h的模拟典型工业大气环境周期浸润加速腐蚀试验，采用腐蚀失重、XRD、SEM、电化学测试等分析试验方法，研究耐候高强度螺栓钢在模拟工业大气环境下的腐蚀行为。结果表明：10.9级耐候螺栓钢和35VB螺栓钢的腐蚀失重量均随腐蚀周期的延长而增加，10.9级耐候螺栓钢的失重量明显低于35VB螺栓钢；随腐蚀周期的延长，10.9级耐候螺栓钢和35VB螺栓钢的腐蚀产物的衍射峰强度均增大，并且在相同腐蚀周期下，10.9级耐候螺栓钢中α-FeOOH相的衍射峰较强；在相同周期下，10.9级耐候螺栓钢与35VB螺栓钢相比，自腐蚀电位较正、自腐蚀电流密度较小，且容抗弧较大，说明加入了Cu、Cr、Ni合金元素的10.9级耐候螺栓钢在典型工业大气环境中具有较为优异的耐蚀性。     

49MnVS3非调质易切削钢汽车曲轴的失效分析

49MnVS3非调质易切削钢汽车曲轴在进行发动机例行工况试验时发生断裂。对失效曲轴进行了化学成分、金相组织、力学性能和断口分析。发现该曲轴材料晶粒粗大，铁素体大都呈网状沿晶分布；材料的韧性差；宏观下，裂纹源区萌生于断口边缘部位，该处未发现刀痕及外伤；断口微观形貌为沿晶断裂和穿晶断裂，有较明显的脆性特征。结论：曲轴断裂是始、终锻温度偏高所致。     

螺栓断裂分析

某固定螺栓在冬季有多根发生断裂现象,为了查出断裂的性质和原因,对螺栓的材料成分、硬度进行了检测；分析了热处理和镀锌工艺过程中可能造成的缺陷；对螺栓的断口进行了观察；对螺栓的受力情况进行了分析.     

100t汽车车轴断裂分析

采用直读光谱、力学性能测试、金相检验和扫描电镜观察等方法对重型载重汽车的断裂车轴进行了分析。结果表明，车轴材质为40Cr钢，未经调质处理，加上车轴表层严重脱碳，导致其力学性能均低于标准值；加之轴表面存在划痕，在表面淬火后形成淬火裂纹，在使用过程中发生脆性解理断裂。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Effect of Oxide Assisted Metal Nanoparticles on Microstructure and Morphology of Gallium oxide Nanowires

Several researches have been reported about the characteristic of β-Ga2O3 nanowires which was synthesized on nickel oxide particle. But indeed, recent researches about synthesis of β-Ga2O3 nanowires on oxide-assisted transition metal are limited to nickel or cobalt oxide catalyst. In this work, Gallium oxide (β-Ga2O3 ) nanowires were synthesized by a simple thermal evaporation method from gallium powder in the range of 700 - 1000℃ using the iron, nickel, copper, cobalt and zinc oxide as a catalyst, respectively. The β-Ga2O3 nanowires with single crystalline without defects were successfully synthesized at the reaction temperature of 850, 900 and 950℃ in all the catalysts. But optimum experimental condition in synthesis of nanowires varied with the kind of catalyst. As increasing synthesis temperature,the morphology of gallium oxide nanowires changed from nanowires to nanorods, and its diameter increased. From these results, we could be proposed that the growth mechanism of β-Ga2O3 nanowires was changed with synthesis temperature of nanowires. Microstructure and morphology of Synthesized nanowire was characterized by HR-TEM, FE-SEM, EDX and XRD.     

The Influence of Nitrogen and Boron Implant into Silicon Substrate on the Phase and Internal Stress of c-BN Films

Cubic boron nitride(c-BN) film was deposited on a Si (100) substrate by the RF-magnetron sputtering.The mainly problems for fabrication of c-BN films are the low purity and high intrinsic compressive stress. In order to solve the two problems, the c-BN film with the buffer interlayer was deposited on the substrate which had been implanted with nitrogen and/or boron ions. The results show: the implantation of nitrogen ions can obviously increase c-BN content and reduce the internal stress slightly; while the implantation of boron shows no obvious improvement to the content of c-BN, which can reduce the internal stress in the film obviously. In addition, it is suggested that the implantation of nitrogen and boron shows the best result, which not only can increase the content of c-BN, but also reduce the internal stress in the c-BN film obviously.