热型连铸CuAlNi形状记忆合金丝的性能研究

用热型连铸法制取φ1.5mm的柱晶CuAlNi合金丝,具有轴向排列的柱晶组织.经过900℃固溶处理,拉伸曲线与单晶的相似,具有两个阶段的马氏体转变,抗拉强度可达633MPa,延伸率14.95%.在4%的固定应变下,反复拉伸疲劳断裂次数高达38560次,形状回复率为100%.反复拉伸后在晶界上形成一种新相,有效地松弛了晶界上的应力集中,可能是疲劳寿命大幅度提高的原因.     

热型连铸法制取CuAINi形状记忆合金丝

用热型链铸法从金属液直接成形制取直径１．５ｍｍＣｕＡＩＮｉ合金丝。将铸型温度设定为１１１０℃,可以拉铸出表面光洁、内部含有几个平行晶粒的定向凝固合金丝。拉铸速度５０ｍｍ／ｍｉｎ时,晶粒数较少,晶界平直;拉铸速度８０ｍｍ／ｍｉｎ时,晶粒数较多,晶界较曲折。试样经１０００℃固溶处理后,拉伸强度达５０２Ｎ／ｍｍ＾２,延伸率１４．４％,其中塑性应变８％。在４％固定应变下,反复拉伸的疲劳断裂次数高达７０６次,比文献的列单晶的断裂次数提高４４％。热型连铸法制取铜基形状记忆合金,既可免疫塑性加工的困难,又可获得定向凝固组织,提高合金性能,具有巨大的优越性。     

Ti-6Al-4V钛合金细晶组织的应变疲劳行为研究

研究了Ti-6Al-4V钛合金细晶等轴组织的应变疲劳性能及其断裂行为.实验结果表明,Ti-6Al-4V铁合金的应变疲劳的过渡疲劳寿命Nt约为560个循环周次,其疲劳行为具有非常明显的循环软化特性.在不同应变幅测试条件下,均为多源疲劳萌生模式.Ti-6Al-4V合金应变疲劳断口表面大量的二次裂纹特征说明该合金具有优异的应变疲劳性能.     

16Mn/Zn抗震复合材料的单向拉伸与循环变形行为

采用复合铸造工艺将16Mn钢和工业纯锌制备出双金属层状抗震复合材料,并对其在不同条件下的单向拉伸性能和循环变形行为进行了研究.研究表明:在单向拉伸条件下,应变速率对复合材料试样的应力-应变曲线影响不大;在0.5%、1%、1.5%应变下所对应的拉压应力随循环次数的增多而增大,材料出现循环硬化行为,并且循环应变的提高使材料的循环硬化行为逐渐明显,进一步循环使拉压应力趋于稳定;16Mn钢/锌抗震复合材料试件具有滞回特性,使结构适应反复载荷作用下的内力和变形,起到减震的作用.     

工业纯钛低温拉伸和循环变形中的孪生行为

在-196℃下对钛进行了拉伸和低周循环变形,观察分析了变形后试样的微观组织.结果表明,工业纯钛在-196℃拉伸变形后,强度比在室温下拉伸变形有了明显的提高,塑性也有明显的增加;在-196℃下循环变形时,循环应力-应变曲线位于-196℃静拉伸应力-应变曲线的上方,显示出明显的循环硬化特征.微观组织观察表明,-196℃拉伸及循环变形试样中存在着大量的孪晶,且孪晶数量随着循环应变幅及循环周次的增加而增加.在工业纯钛-196℃下的拉伸及循环变形中孪生起重要作用.     

发动机用灰铸铁的低周疲劳行为

研究了发动机缸体用灰铸铁材料在室温、150℃和250℃下的低周疲劳行为。根据对拉伸应力-应变、循环应力-应变和应变-疲劳寿命数据的分析,给出了疲劳参数。结果表明:在高温下灰铸铁的弹性模量、强度降低,延伸率增大;循环应力响应表明,在较小的应变幅下经历初期循环硬化、循环软化、断裂,而在高温和较大应变幅下几乎没有硬化阶段,循环软化至断裂;其室温疲劳寿命最长,150℃最短,250℃居中。微观分析结果表明:疲劳裂纹萌生于片状石墨尖端、夹杂物及孔洞处,沿石墨扩展,夹杂物导致分支裂纹及裂纹偏转,延缓裂纹的扩展;灰铸铁的疲劳断裂方式为沿晶和准解理断裂的复合机制,存在扇形解理面和二次裂纹,解理台阶上观察到疲劳条带和韧窝。     

不同环境对2D70铝合金低周疲劳性能的影响研究

循环应力和低周疲劳寿命都是材料疲劳损伤的关键指标.循环应力表征的是材料在循环载荷下抵抗变形的能力.大多数飞机构件由于拐角、圆孔、沟槽等的存在都会存在应力集中现象,当构件承受循环应力载荷时,虽然构件总体处于弹性范围内,但局部已进入弹塑性状态,即已处于循环应变的疲劳过程中.这类服役条件下的构件疲劳寿命一般小于105周次,称为低周疲劳,又由于低周疲劳断裂时应力水平往往较高,低周疲劳也称高应力疲劳或者应变疲劳.衡量材料抗低周疲劳特性的指标主要有低周疲劳极限和低周疲劳寿命,二者统称材料的低周疲劳性能.低周疲劳极限,是指材料所承受应力低于该应力极限值时其理论循环次数可为无限次;低周疲劳寿命,即构件破坏前能承受应力循环的次数.     

钢/锌层状复合材料的力学性能与耗能行为

对复合铸造法制成的钢/锌层状复合材料在不同条件下的单向拉伸和低周疲劳实验进行了研究.结果表明:锌的加入使钢/锌复合材料的塑性得到提高,同时其强度与钢相比有所降低.在单向拉伸条件下,拉伸速度对钢/锌复合材料试样的应力-应变曲线影响不大.在±0.5%,±1.0%,±1.5%应变范围内,所对应的拉压应力随着循环次数的增多而增大,表明材料出现循环硬化行为,并且循环应变的提高使材料的循环硬化行为逐渐明显,进一步循环使拉压应力趋于稳定.     

镭射BOPP基膜循环拉伸力学性能的试验研究

目的 为研究双向拉伸聚丙烯（Biaxially Oriented Polypropylene,BOPP）薄膜在重复拉伸使用后的弹性模量变化以及应变变化趋势。方法 以26μm BOPP薄膜为研究对象,以1、1.5、2、2.5、3、3.5、4N为最大加载力分别进行加载周期为15次的单轴循环拉伸试验,总结对比循环次数以及加载力对弹性模量及棘轮应变的影响,分析薄膜性能变化趋势。结果 通过对比同一加载应力不同循环下的弹性模量以及棘轮应变,发现在预设加载力下随着循环次数增加,薄膜弹性模量呈增大趋势,且增大幅度逐渐减小,其棘轮应变与弹性模量变化趋势一致;通过取均值对比不同加载力下的弹性模量以及棘轮应变变化,发现薄膜弹性模量随加载力增大而先增大后减小,最大应变以及最小应变均随加载力的增加而增大。结论 通过试验研究得出了BOPP薄膜在循环拉伸中弹性模量及棘轮应变随加载力、循环次数增大的变化趋势;对薄膜性能变化有了一定的预测,并为实际加工中的张力选择提供了指导性建议。     

机械疲劳对40Cr钢显微组织的影响

以汽车曲轴常用材料40Cr钢为研究对象,用透射电镜对经过不同疲劳周次的试样进行显微组织观察,研究其显微组织与机械疲劳的对应关系。研究表明：在同一应力水平下,随着疲劳循环次数的增加,位错从晶界出发向晶内扩展,位错的形态由无规律的分布到形成位错条带,最后形成亚晶粒组织。机械疲劳循环次数与位错密度的函数关系为p=2．88X10^8N＋5．2712X10^8。     

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.……     

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.     

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 ...