斜盘式压缩机活塞滑履间隙对振动的影响

加工精度等因素使得斜盘式压缩机活塞滑履间隙不可避免,不同间隙对压缩机的振动贡献量也不同。首先对同型号不同活塞滑履间隙的压缩机进行仿真分析,再结合试验对不同转速和活塞滑履间隙工况下的压缩机进行振动测试,利用时域信号和频谱分析确定间隙是压缩机空转时的主要振动源之一。通过仿真和试验分析发现,压缩机的振动冲击随着间隙和转速的增加而加剧,试验与仿真结果比较吻合,研究结果为压缩机故障诊断提供参考和依据。     

制动器螺栓复合应力下的失效分析

用手制动拉索和制动器螺栓将装运的面包车固定在平板车上，到达目的地后发现制动器螺栓出现松动和断裂现象。在运输过程中，制动器螺栓不仅承受上下振动方向高频率低应力而形成的双向弯曲状态，而且又要承受前后方向的低频率高应力而形成的单向弯曲状态。通过受力分析并结合扫描电镜对断口形貌和显微组织的观察，在螺栓齿根发现多处疲劳源，在扩展阶段，出现疲劳辉纹和大量二次裂纹，最终在拉应力作用下形成撕裂台阶而断裂。     

压缩机网状气阀阀座结构的力学分析和应用

介绍活塞压缩机汽缸用网状气阀阀座的结构的力学分析。通过对实际应用中断裂阀座的应力计算,找到阀座断裂的原因,改进阀座结构,使气阀正常工作。     

氢气压缩机缸盖螺栓断裂失效分析

某石化公司氢气压缩机缸盖螺栓发生断裂,采用宏、微观断口分析、化学成分分析、金相检验以及力学性能测试等试验手段分析了该氢气压缩机缸盖螺栓的断裂原因。结果表明：断裂起源于螺杆与螺栓头部连接螺纹末端的应力集中处,由于应力集中,加之螺栓强度等级偏低,使螺栓在长期工作过程中的往复交变应力和扭转应力共同作用下发生了低应力高周疲劳断裂。     

变排量压缩机斜盘运动卡滞现象分析

变排量斜盘式压缩机可以根据吸气腔压力、排气腔压力、斜盘腔压力来改变斜盘倾角。压缩机在使用中发现斜盘倾角变化出现卡滞现象,即斜盘从一个角度不能灵活、准确的变化到另外一个角度。通过压缩机斜盘的动力学分析,得出作用在斜盘上的侧向气体力矩会使斜盘毂和主轴之间产生较大的摩擦力,从而导致斜盘运动出现卡滞。针对斜盘毂和主轴之间摩擦力偏大,提出改进措施,研究结果为压缩机的结构优化提供了参考。     

某压缩机内部活塞与滑阀连接螺栓断裂失效分析

某螺杆压缩机内部活塞与滑阀之间的连接螺栓在使用过程中仅运行2 500h即发生断裂。采用化学成分分析、宏观观察、光学显微镜和扫描电镜观察等方法对连接螺栓的断裂原因进行了分析。结果表明:导致连接螺栓断裂的主要原因是螺栓装配服役期间承受附加弯曲应力,在交变应力的共同作用下于应力集中的齿根周边过早萌生裂纹并疲劳扩展,最终造成螺栓断裂。     

斜撑杆失效案例分析

飞机发动机吊架斜撑杆作为飞机发动机安装的重要结构部件,服役过程中往往承受着复杂多变载荷的影响,某型号飞机在飞行后的例行检查中发现飞机发动机吊架一根材质为30CrMnSiA的斜撑杆发生断裂现象。该文通过宏观形貌检查、力学性能检测、化学成分分析、金相观察及扫描电镜(SEM)等方法对斜撑杆使用过程中发生断裂的原因进行分析。结果表明,斜撑杆螺纹根部应力集中引起表面早期裂纹,在一次异常载荷作用下引起斜撑杆发生过应力断裂。     

苯乙烯装置中氢压机吸气阀的断裂原因

某苯乙烯装置中氢压机四级气缸东侧吸气阀在运行中发现其阀座密封面有部分区域断裂。通过宏观分析、低倍分析、化学成分分析、金相检验、硬度测试和扫描电镜分析等方法,对阀座密封面断裂的原因进行了分析,并提出了相应的措施。结果表明:阀座因热处理工艺不当,在阀座上表面外圈台阶部分金属损伤处形成疲劳裂纹,并在工作过程中向两端不断扩展,在交变载荷的作用下阀片内的弹簧断裂,导致裂纹处应力更加集中和阀座承载能力下降,加快阀座疲劳裂纹的扩展,最终导致阀座密封面部分区域断裂损伤。     

10t吊钩断裂原因分析

10 t吊钩在使用过程中发生断裂失效。采用化学成分分析、断口分析和金相检验等方法对吊钩断裂的原因进行了分析。结果表明:由于该吊钩柄部与螺纹尾部的过渡处R角太小,并且有明显的机加工刀痕,造成应力严重集中,使得裂纹在此处萌生;吊钩在作业过程中,由于存在起吊倾斜角和吊运时的前后摆动,使得吊钩柄部两侧承受了较大的拉、压应力,促使裂纹不断扩展,最终导致吊钩发生了双向弯曲疲劳断裂。     

汽车雨刮器刮杆接头断裂失效分析

某汽车雨刮器上的刮杆接头在进行12h的连续雪堵试验后发生断裂失效。为查明断裂原因,对刮杆接头进行了宏观分析、断口分析、化学成分分析、硬度测试以及金相检验。结果表明:该刮杆接头内侧R凸角的台阶处存在机械损伤缺陷,裂纹源萌生于此机械损伤缺陷处,加之R凸角台阶的应力集中效应,故在连续雪堵试验时刮杆接头发生一次性大应力断裂。     

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 ...