吊车转盘连接螺栓断裂分析

吊车转盘后部的连接螺栓发生断裂,通过化学成分分析、宏观和微观检验等方法对断裂原因进行了分析。结果表明：螺栓为疲劳断裂,螺纹根部的细小裂纹是导致螺栓发生疲劳断裂的主要原因;螺栓松动后受到弯曲载荷是引起螺栓发生疲劳断裂的诱因。     

某铁路桥梁用20MnTiB钢高强螺栓断裂原因

某铁路主桥钢桁梁杆间20MnTiB钢高强螺栓发生断裂。采用复检试验、化学成分分析、金相检验、硬度测试、力学性能测试和断口分析等方法,分析了螺栓断裂的原因。结果表明：螺栓的断裂形式为氢致断裂,断裂原因是螺栓中锰元素含量偏高,导致耐腐蚀性下降,长期在潮湿环境下服役,致使螺栓发生氢致断裂。     

洗衣机螺栓断裂失效分析

某洗衣机螺栓在安装过程中发生断裂失效,为查明螺栓断裂的原因,对断裂螺栓进行了化学成分分析、宏观分析、金相检验和断口微观形貌分析。结果表明：螺栓断裂是由于其制造时产生了严重的带状组织,降低了螺栓的许可扭转力矩,导致螺栓在安装过程中发生扭转断裂。     

镀锌螺栓的断裂分析

镀锌螺栓在组装后放置1～2d于根部或头部发生大量断裂,采用化学成分分析、金相检验、硬度检测及断口分析等方法对螺栓的断裂性质及断裂原因进行了分析。结果表明：螺栓断裂为典型的氢脆断裂;主要原因是螺栓在后期酸洗和电镀过程中除氢不彻底,吸入了大量的氢;次要原因是热处理工艺控制不当,使螺栓心度硬度偏高,增加了其对氢脆的敏感性;两者共同作用最终导致螺栓发生氢脆断裂。     

新能源客车电容支架安装螺栓的断裂原因分析

某新能源客车上的电容支架固定螺栓发生批量断裂。通过对断裂螺栓进行宏观观察、力学性能测试、金相检验、化学成分分析等,分析了其断裂原因。结果表明:螺栓的断裂为双向弯曲疲劳断裂;发生断裂的主要原因是电容支架与车架连接结构设计不当,导致结构松动,使螺栓受到弯曲交变应力作用;次要原因是螺纹表面脱碳,降低了螺栓的疲劳强度。     

发动机缸盖螺栓断裂原因分析

某发动机缸盖螺栓在装配后发生断裂。通过宏观、微观检验以及化学成分分析、力学性能测试、氢脆试验等对断裂原因进行了分析。结果表明:缸盖螺栓发生了氢脆断裂。其原因是缸盖螺栓在表面磷化后的去氢处理不当,导致装配后缸盖螺栓在拉应力的作用下产生氢脆裂纹,并最终发生断裂。     

柴油机用高强度螺栓断裂失效分析

某柴油机用30CrMoSi钢高强度螺栓在使用过程中发生断裂。通过化学成分分析、金相检验、断口分析、硬度测试等方法对螺栓断裂原因进行了分析。结果表明:螺栓断裂为早期疲劳断裂,螺栓螺纹根部存在加工缺陷以及螺栓材料中存在较多的非金属夹杂物是导致其疲劳断裂的主要原因。最后针对螺栓断裂原因提出了预防措施。     

高铁道岔夹杆螺栓断裂原因分析

用于高铁变线道岔的某1Cr17Ni2不锈钢夹杆螺栓在使用约6a(年)后发生了断裂。使用宏观检查、化学成分分析、拉伸试验和硬度测试等方法,对螺栓的断裂原因进行了分析。结果表明:螺栓断裂的主要原因是螺栓断裂部位的过渡圆角半径不符合技术要求,加剧了该部位的应力集中,在外力的作用下诱发疲劳裂纹;夹杆螺栓处于松动状态时,高速运行的火车使螺栓产生与运行方向相反的惯性力,导致螺栓于其薄弱部位发生疲劳断裂。     

蜗轮连接螺栓断裂失效分析

装卸料机上的蜗轮连接螺栓材料为35钢,强度等级为10.9级,在设备运行大约10a后发生断裂。对断裂螺栓进行宏观、化学成分、硬度、金相、能谱和断口分析后得出,该螺栓的断裂性质为双向弯曲疲劳断裂,螺栓表面的脱碳和螺纹颈部的应力集中降低了该部位的疲劳性能。通过综合分析和螺栓受力估算后得出,螺栓断裂的主要原因是螺栓和内齿轮螺栓孔之间存在较大的间隙,使螺栓的受力状态和受力大小过早地发生了变化,造成连接螺栓疲劳断裂。     

发动机凸轮轴正时带轮紧固螺栓断裂原因分析

某汽车发动机凸轮轴正时带轮紧固螺栓在台架耐久试验中发生断裂。通过宏观检验、化学成分分析、硬度测试、金相检验以及断口分析等方法对螺栓的断裂原因进行了分析。结果表明:该紧固螺栓的断裂模式为疲劳断裂;螺栓未紧固到设计要求的预紧力,导致其在使用过程中发生松动,在交变应力作用下螺栓螺纹旋合部位萌生裂纹,最终导致螺栓发生疲劳断裂。     

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.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

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.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

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 ...