NiTi形状记忆合金丝在Al基复合材料中的约束态马氏体逆相变特征

利用DSC,XRD,SEM等实验手段研究了NiTi记忆合金丝在铝基体约束状态下的马氏体逆相变特征。研究结果表明,预应变NiTi记忆合金丝在加热过程中发生两种马氏体逆相变：热致马氏体逆转变(MT→P)与应力诱发马氏体逆转变(Md→P),其中热致马氏体逆相变温度与未预应变样品基本相同,且不受预应变影响;而应力诱发马氏体向母相转变温度随预应变增加而升高;随预应变增加,热致马氏体与应力诱发马氏体的逆转变量减少。文中引入马氏体变形度概念,并对马氏体在逆转变过程中的变形度变化进行了讨论。     

热循环对预应变NiTi记忆合金丝/铝基复合材料马氏体逆相变的影响

采用热压法将0.26mm的NiTi合金丝复合于铝中,利用SEM,DSC,热膨胀仪等实验手段研究了热循环对预应变为4%的NiTi合金丝/铝基复合材料马氏体逆相变的影响。结果表明,在第一次加热过程中,马氏体逆转变开始温度明显升高;第二次加热过程中逆转变开始温度比未预应变样品略有降低;随热循环次数增加,逆相变开始温度降低;当循环次数超过30次后,逆转变温度几乎保持不变。并对热循环过程中的马氏相变过程进行了分析讨论。     

预应变对铝基体中复合的TiNi合金丝马氏体逆相变的影响

采用示差扫描热分析(DSC)、X射线衍射(XRD)和扫描电子显微分析(SEM)等方法,研究了预应变对铝基体中复合的TiNi形状记忆合金丝的马氏体逆相变的影响.结果表明,预应变的TiNi丝发生两种逆相变,一种是热致马氏体(TIM)的逆相变,另一种是应力诱发马氏体(SIM)的逆相变.预应变样品的TIM逆相变的起始温度与未预应变样品的基本相同.SIM逆相变的起始温度随预应变的增大而升高.TIM和SIM逆相变的分数随预应变的增大而减少.     

真空固溶及时效处理后NiTi合金的两步逆相变

利用真空炉对NiTi形状记忆合金进行了固溶处理，并对固溶处理及时效后合金的相变行为及力学性能进行了研究。结果表明，时效处理及预应变后合金丝的DSC曲线上均有两个逆马氏体相变峰，并随着预应变的增加，两个逆马氏体相变温度均升高。预应变后的合金丝在自由加热过程中能够输出两段回复应变，分别对应于两步逆马氏体相变。     

爆炸合成NiTi／NiTi合金的相变行为

采用爆炸焊将两块原子百分比不同的NiTi合金制成大块成分不均匀的NiTi／NiTi复合板，并在此基础上对其相变行为以及相应的回复应变特征进行了研究。结果表明焊后的复合板具有良好的界面结合和可逆马氏体相变；冷变形后NiTi／NiTi合金的逆相变温度及其相变温度范围随预应变量的增大而升高；同时，在较宽的温度范围内得到两步回复应变。     

振动时效对NiTi记忆合金回复特性与相变行为的影响

研究了振动时效对约束态下NiTi形状记忆合金的力学性能与相变行为的影响,用自制的拉伸机测试了振动与未振动NiTi合金在自由加热过程中的回复应变,用万能拉伸实验机测试了NiTi合金的力学性能,用DSC测试了NiTi合金的相变行为.结果表明,随着振动幅度的增加,NiTi合金丝在自由加热过程中输出的两段回复应变减小;随着振动时间的延长,NiTi合金输出的回复力减小,最多约80MPa.DSC结果表明约束态振动后再变行马氏体逆相变温度升高,相变潜热减小,而继承变形马氏体和热诱发马氏体相变潜热增加.所有结果均直接或间接表明,振动时效降低了NiTi形状记忆合金产生的回复力.这可能是由于振动在NiTi合金中产生了微观塑性变形,降低了回复力.     

TiNi形状记忆合金在定应变约束下的马氏体相变

通过DSC及回复应变的测量,研究了定应变约束态加热-冷却过程对预应变TiNi形状记忆合金相变行为的影响。结果表明,在约束态相变中,逆相变温度区间拓宽;取向马氏体除向母相转变外,应变还要进一步增大;在正相变过程中,从母相生成的马氏体也具有变形结构。约束态不完全相变后,样品中存在两种马氏体;再变形马氏体和继承变形马氏体,在随后的无约束逆相变过程中,前者的相变温度高于后者,并且输出两段回复应变。     

TiNi和TiNiCu记忆合金丝/镍基机敏复合材料相变潜热研究(英文)

通过DSC对TiNi和TiNiCu记忆合金丝/镍基机敏复合材料的相变潜热进行了研究.结果表明,预应变TiNi试样在无约束状态下的第一次马氏体逆相变过程中,相变潜热值随预应变水平的增加而迅速增大,而在镍基体约束下,相变潜热值随预应变水平的增加而迅速减小.但TiNiCu和TiNiCu丝/镍基复合材料的相变潜热变化趋势与TiNi试样的明显不同.对上述现象给出了合理的解释.     

TiNi合金在恒应力约束下的不完全相变

利用DSC对预应变TiNi形状记忆合金丝在恒应力约束下的马氏体不完全逆相变进行了研究,发现不完全相变热循环样品在第二次自由态加热过程中出现两步马氏体逆转变和两段应变回复现象.分析认为:经过恒应力约束下的不完全逆相变后,TiNi样品中存在不同的马氏体,在随后的加热过程中先后逆转变,产生两段回复应变.     

NiTi形状记忆合金丝输出应力与应变

本文研究了预应变ＮｉＴｉ形状记忆合金丝输出应力与应变及其关系。结果表明，预应变ＮｉＴｉ记忆合金丝输出应力与应变是非线性关系。输出应力由相变输出应力和弹性输出应力组成，相变输出应力随温度升高而升高，而与预应变几乎无关，相变输出开始和终止应力庶线性关系，输出应变由相变输出应变和弹性输出应变组成，相变输出应变随预应变增加而增加，随温度升颃是减少，输出是预应变和温度的函数。     

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.……     

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 ...