油压机柱塞裂纹分析

采用化学分析、金相检验和显微硬度梯度试验等方法对油压机柱塞表面淬火交界处裂纹进行了分析。结果表明，由于柱塞原材料含碳量偏高、晶粒粗大、存在严重的带状组织缺陷，加大了淬火开裂的倾向，同时降低了材料的力学性能，加之淬火时交界处产生大的组织应力，叠加的应力超过了材料的强度极限，导致裂纹的产生。     

柱塞套开裂原因分析

一批柱塞套在磨削加工后发现其中有十几件出现裂纹。采用宏观分析、化学成分分析、金相检验及硬度测试等方法对开裂柱塞套进行了分析。结果表明：柱塞套在淬火加热过程中局部过热,引起显微组织及奥氏体晶粒粗大,降低了材料的强度,导致在柱塞套淬火过程中引起淬火裂纹。最后提出了改进建议。     

1105柴油机齿轮断裂分析

采用宏观和微观分析法,对柴油内曲轴正时齿轮断裂原因进行了分析。结果表明,齿轮原材料中存在较多的非金属夹杂物及较严重的带状组织,加之工艺欠妥,使齿轮产生淬火裂纹,在装配过程中裂纹进一步扩展导致齿轮断裂。     

2Cr13不锈钢止血钳断裂原因分析

某2Cr13钢有齿止血钳在使用11个月后于刃部发生断裂。采用宏观检验、化学成分分析、硬度测试、金相检验的方法,对止血钳发生断裂的原因进行了分析。结果表明:由于淬火温度过高,导致止血钳出现淬火裂纹和粗大组织,且淬火后磨削又出现了磨削裂纹,裂纹扩展最终导致失效,最后针对此原因提出了改进措施。     

50钢被动轴断裂分析

减速器被动轴在负荷试验过程中断裂，借助金相显微和ＳＥＭ等观察该轴的显微组织和断口形貌，结果表明，锻造加热时轴局部严重过热是造成轴心淬火裂纹，校直中裂纹扩展，开启，导致轴断裂的根本原因。提出了相应的热处理措施。     

中碳合金钢双相组织疲劳裂纹扩展的研究

研究了４２ＣｒＭｏ钢亚温淬火及二次淬火两种双相组织的疲劳裂纹扩展行为。结果表明，亚温淬火双相组织可显著提高裂纹萌发生抗力，降低扩展速率；较高的疲劳性能与裂纹尖端闭合应力，断口表面粗糙度以及裂纹扩展路径弯折程度有关。断裂力学分析表明，粗糙度诱发裂纹闭合效应及裂纹路径变折效应是提高裂纹扩展抗力的主要因素，同时得到上述两种效应对裂纹扩展速率影响的表达式。     

45钢螺帽断裂原因

在加工某型45钢螺帽时，数控车过程中发现有2个螺帽发生断裂。采用宏观观察、化学成分分析、扫描电镜及能谱分析、金相检验、硬度测试和热处理工艺分析等方法，研究了螺帽断裂的原因。结果表明：螺帽断裂处存在淬火裂纹；螺帽毛坯孔壁的厚度处于淬火裂纹敏感厚度的区间内，且底孔与内壁的过渡圆弧较小，产生了应力集中，并形成了淬火裂纹，裂纹沿晶扩展，最终在数控车过程中螺帽发生断裂。     

轴坯校直断裂分析

材料为3Cr13钢的轴坯在进行机械校直时，有30%的轴坯发生了横向断裂。经分析，轴坯的化学成分符合技术条件要求。经宏、微观检验，发现轴坯的外表面有数条裂纹；其显微组织为位向明显的回火索氏体，裂纹表面有轻微的氧化脱碳；轴坯断口为萘状断口，其微观断裂途径为沿晶断裂。通过对断裂轴坯表面裂纹的分析，认为轴坯表面裂纹分为两类：一类裂纹是由于轴坯原材料表面有较深的纵向划伤缺陷，热处理时沿缺陷处进一步扩展形成的；另一类裂纹是轴坯在淬火加热过程中由于温度偏高而形成的过热裂纹。因此，淬火加热时的过热导致轴坯在淬火冷却时形成表面裂纹，这样在轴坯机械校直时表面裂纹又诱发轴坯发生断裂。     

汽车板簧的断裂分析

汽车板簧在路试中出现早期疲劳断裂。采用化学成分分析、硬度测试、断口分析和金相检验等方法对断裂的汽车板簧进行了分析。结果表明,焊接时,飞溅的熔滴在板簧表面形成烧伤坑并形成淬火马氏体及淬火裂纹,在路试中产生应力集中而成为疲劳源,在交变应力作用下使裂纹扩展而最终断裂。     

轧辊断裂原因分析

某轧辊直径由840mm减少到780mm时发生断裂,未达到其正常使用寿命,采用化学成分分析、断口分析、金相检验以及硬度检测等方法对轧辊断裂原因进行了分析。结果表明：轧辊辊颈与辊身交界处的表面存在微裂纹是导致其发生断裂的根本原因;由于套密封环时操件不当使得该处的表层显微组织发生淬火,形成薄且脆的淬火组织,加之该处为应力集中处,从而导致该处产生微裂纹;已经形成的微裂纹在轧辊工作时所承受压力和扭转力的作用下,由于应力集中裂纹尖端不断向轧辊中心扩展,当裂纹达到一定深度后,辊颈处无法承受外力的作用时便会发生瞬间失稳扩展,导致轧辊断裂。     

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.……     

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...     

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.     

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 ...