钢管倒棱机液压伺服系统的仿真分析

利用AMEsim系统仿真建模工具建立了该伺服系统的仿真模型,对其动态性能进行了仿真和分析,为其校正和改进提供了参考.     

低合金型高强度不锈钢材料的实验室研究

为提高不锈钢的机械性能,促进其作为结构材料使用,通过控制适当的合金元素配比和相应的加工工艺,实验室开发了一种低合金型的高强度不锈钢材料.介绍了不同工艺下其组织、硬度和力学性能的变化规律,并确定了能得到较好强塑性结合的热处理制度;利用金相显微镜、EBSD、TEM对其微观组织结构进行研究,分析了其强度提高的原因;根据相关国家标准评价了其耐腐蚀性和焊接性.结果表明,在铁素体基体上引入适当的第二相,可以在保持良好塑性的基础上大幅度提高材料的强度,同时具有良好的耐腐蚀性和焊接性.     

钢包耳轴的超声波探伤技术研究

阐述了无损检测技术中的超声波探伤方法和特点。根据钢包耳轴的生产要求,制定了对其进行超声检测的探伤工艺,并使用汉威HS610e型数字式超声探伤仪对其进行了检测。结合耳轴的制造工艺和结构特点,对检测回波进行分析研究,确定了其内部缺陷的位置和类型。     

国内外锂资源概况及其选冶加工工艺综述

简要介绍了国内外锂资源概况和锂矿物主要特性,综述了其选矿、冶炼和加工工艺及 其进展。     

设备传动隐性过定位危害与解决办法

碱纤维素冷却装置是粘胶短纤维企业生产的核心设备之一,其特点和作用为带有一定风压并且用于碱纤维素输送和密封冷却。原为奥地利兰精进口设备,其在实际生产使用中暴露出了设计、制造中的重大缺陷,经过技术人员对其存在的问题和管理措施等进行了梳理总结,取得了较好的社会效果和经济效益。供大家参考借鉴。     

钢铁行业计量和质量信息化的设计与研究

结合济钢的信息化建设,阐述了其计量和质量管理信息系统平台的实施情况和系统功能结构,论述了钢铁行业计量和质量信息化项目的研究和发展前景,对其功能的设计和规划的实施具有借鉴意义。     

李渔的生平与创作

李渔的创作与其三个有代表性的人生阶段有着密切的关系,经历了清初战乱时期、归隐山林时期和＂卖赋以糊其口＂时期。李渔的人生经历与其创作密切相关,了解其人生经历,能指导和启发学术界对其作品的深入研究。     

真空热压制备W-50%Cu复合材料

采用真空热压制备了W-50%Cu复合材料,对其性能进行了测试,并利用SEM对其微观组织和断口形貌进行了观察与分析.结果表明:在30MPa压力下进行950℃×2h烧结,获得了相对密度达99.6%的W-50%Cu复合材料,其显微硬度、电导率和抗弯强度分别达到133HV、68.9%IACS和285MPa;W-50%Cu复合材料的抗弯断裂表现出塑性断裂特征,其断裂方式主要为沿晶断裂,并伴随少量的穿晶断裂.     

谢韦尔钢铁公司的矿产资源战略及竞争力

阐述了谢韦尔钢铁公司分三步走实现了其矿产资源的发展战略,即进军矿山产业、实现矿业独立经营、走国际化发展道路。详细介绍了矿产资源产业生产经营现状。分析了其在铁矿和煤炭领域的竞争力,展望了其未来投资规划。     

型钢属性的提取、更新和BOM的自动生成

介绍了型钢属性的自动提取,单重、总重的自动计算,以及其属性的自动更新,介绍了型钢BOM的自动生成.阐述了其设计方法和实现技术.     

W对自由烧结型铁基金刚石工具胎体性能的影响

以专用于自由烧结型金刚石工具胎体的亚微米级铁基合金粉末为主要结合剂,添加金属W(添加量为0~12%,质量分数),采用自由烧结工艺制成金刚石工具胎体和金刚石/胎体试样,对胎体进行力学性能测试和断口形貌分析,并用金刚石工具进行磨削试验。结果表明,随W含量增加,胎体的相对密度及强度均下降;添加6.0%W可明显提高胎体对金刚石的把持能力,并提高胎体硬度,但随W含量进一步增加,把持能力下降,同时胎体硬度降低;W在胎体内虽然可生成强碳化物,但在自由烧结过程中起不到强化胎体的作用,反而降低胎体的韧性,尤其是当胎体中添加12.0%W时,胎体内孔隙明显,强度大幅下降;与不添加W的胎体相比,添加8.0%W时,虽然金刚石工具的锋利度有所下降,但耐磨性提高。     

Matrix metalloproteinases and tissue inhibitors of metalloproteinases in loose artificial hip joints

The role of extracellular matrix metalloproteinase enzymes and the tissue inhibitors of metalloproteinase in the periprostetic connective tissue matrix of loose artificial hip joints is reviewed. In the periprosthetic granulomatous interface connective tissues between bone and implants and inner cellular regenerating pseudocapsular tissues, matrix metalloproteinase 1, matrix metalloproteinase 2, matrix metalloproteinase 3, matrix metalloproteinase-9, and membrane type 1 matrix metalloproteinase enzymes can be shown in the light of immunohistochemistry, enzyme activity analysis, and messenger ribonucleic acid levels. Tissue inhibitors of metalloproteinase 1 and tissue inhibitors of metalloproteinase 2 also are found in the corresponding tissues. Analysis of matrix metalloproteinase and tissue inhibitors of metalloproteinase interaction shows imbalance between the enzymes and the endogenous inhibitors in favor of matrix metalloproteinase. This induces pathologic connective tissue remodeling in the interface and pseudocapsule. The data suggest that matrix metalloproteinase and tissue inhibitors of metalloproteinase system participate in the extracellular matrix degradation and tissue remodeling in artificial hip joints, and may contribute to the periprosthetic weakening, implant loosening, and osteolysis around implants. More evidence for their active involvement is sought by intervention studies with type specific matrix metalloproteinase inhibitors.     

Taking enzyme kinetics out of control; putting control into regulation

The matrix formulation of metabolic control analysis, which states that multiplying the elasticity matrix for any system by the corresponding control matrix yields an identity matrix, can be transformed into a statement that multiplying a matrix expressing internal regulatory properties by a matrix expressing external regulatory properties also yields an identity matrix. This transformation supplies the formal basis for metabolic regulation analysis, and provides the key to determining the control structure of a system without the need to know the exact changes in enzyme activities that are made to measure control coefficients.     

原位自生钛基复合材料的研究进展

原位自生钛基复合材料以其高比强度和高比模量引起了人们的广泛关注,尤其是如何提高其高温性能成为近年来钛基复合材料研究的热点.该文详细综述了原位自生钛基复合材料的各种制备方法、增强体与钛基体的选择、各种增强体的反应体系以及原位自生钛基复合材料的组织结构与力学性能,指出了原位自生钛基复合材料今后的发展方向.     

Pretension-Dependent Residual Stress of Alumina Fiber-Reinforced Composite Wire

The relationship between pretension and residual stress of an aluminum wire reinforced with 45 vol pct continuous Nextel? 610 alumina fibers is investigated. It is shown that as pretension stress increases, the matrix residual stress decreases. A transition in matrix residual stress from tension to compression occurs at a pretension stress of about 80 MPa. The initial rapidly decreased residual stress caused by pretension at relatively low pretension stresses is a result of matrix elastic compressive deformation; while the later gradually decreased residual stress at higher pretension stresses comes from matrix plastic compressive deformation. As the matrix yield stress and hardening exponent increase, the decrease in matrix residual stress with pretension stress is more rapid and the absolute value of matrix residual stress increases. An analytical model suitable for fiber-reinforced metal matrix composites (MMCs) with strong interfacial bonding is developed to describe the relationship between pretension and matrix residual stress and is shown to be in good agreement with the experimental and finite-element calculated results. The pretension-dependent matrix residual stress phenomenon suggests that the mechanical properties of fiber-reinforced MMCs associated with matrix residual stress may be effectively improved by applying tensile loads.     

Assembly of amino-terminal fibronectin dimers into the extracellular matrix

Fibronectin is a dimeric adhesion molecule that consists of three types of repeating modules. Adherent cells bind soluble fibronectin and incorporate it into insoluble fibrils in the extracellular matrix. The amino-terminal 70-kDa portion of fibronectin mediates binding to the cell surface, but amino-terminal fragments do not accumulate in the extracellular matrix. The ninth type I and first type III modules, the cell adhesion region, and the cysteines that form the interchain disulfide bonds have also been implicated in matrix assembly. To further define which regions of fibronectin are essential for matrix assembly, we generated a dimeric protein (d70 kDa) in which the 70-kDa amino terminus is directly linked to the last 51 amino acids of fibronectin, which contain the cysteines involved in interchain disulfide bonding. d70 kDa bound to cells and accumulated in the extracellular matrix. Incorporation of d70 kDa into the extracellular matrix was dependent upon protein synthesis; in cycloheximide-treated cultures that lacked a pre-existing matrix, d70 kDa accumulated in the extracellular matrix only in the presence of intact fibronectin. Monomeric 70-kDa protein was not incorporated into the matrix in the presence or absence of cycloheximide. These data indicate that fibronectin molecules containing only the amino-terminal 70-kDa region and the carboxyl-terminal 51 amino acids can become assembled into the extracellular matrix.     

A Note on Nonproportional Damping

This note deals with three aspects of nonproportional damping in linear damped vibrating systems in which the stiffness and damping matrices are not restricted to being symmetric and positive definite. First, we give results on approximating a general damping matrix by one that commutes with the stiffness matrix when the stiffness matrix is a general diagonalizable matrix, and the damping and stiffness matrices do not commute. The criterion we use for carrying out this approximation is closeness in Euclidean norm between the actual damping matrix and its approximant. When the eigenvalues of the stiffness matrix are all distinct, the best approximant provides justification for the usual practice in structural analysis of disregarding the off-diagonal terms in the transformed damping matrix. However, when the eigenvalues of the stiffness matrix are not distinct, the best approximant to a general damping matrix turns out to be related to a block diagonal matrix, and the aforementioned approximation cannot be justified on the basis of the criterion used here. In this case, even when the damping and stiffness matrices commute, decoupling of the modes is not guaranteed. We show that for general matrices, even for symmetric ones, the response of the approximate system and the actual system can be widely different, in fact qualitatively so. Examples illustrating our results are provided. Second, we present some results related to the difficulty in handling general, nonproportionally damped systems, in which the damping matrix may be indefinite, by considering a simple example of a two degrees-of-freedom system. Last, we use this example to point out the nonintuitive response behavior of general nonproportionally damped systems when the damping matrix is indefinite. Our results point to the need for great caution in approximating nonproportionally damped systems by damping matrices that commute with the stiffness matrix, especially when considering general damping matrices. Such approximations could lead to qualitatively differing responses between the actual system and its proportionally damped approximation.     

Effects of alloy steel shot on matrix hardness of impregnated diamond bit based on WC

In order to study the hardness of WC- based matrix used for impregnating diamond bits, matrix samples were prepared by hot pressing with different volume fractions of alloy steel shot. The main performance parameters of matrix (hardness, abrasion resistance and bending strength) were tested, and the surface morphology was observed using SEM. The results show that the matrix becomes harder with the increasing of sintering temperature, but adding alloy steel shot will reduce the hardness of the matrix and the higher the content of alloy steel shot, the lower the hardness of the matrix. In the process of sintering, due to the non- uniform diffusion and enrichment of some elements in the matrix, a fragile bonding interface is formed inside the sample. Under the external force conditions, the brittle interface is prone to slip and damage, ultimately affects the hardness of the matrix.     

High-Temperature Fatigue of a Hybrid Aluminum Metal Matrix Composite

An aluminum metal matrix composite (MMC) brake drum was tested in fatigue at room temperature and extreme service temperatures. At room temperature, the hybrid composite did not fail and exceeded estimated vehicle service times. At higher temperatures (62 and 73 pct of the matrix eutectic), fatigue of a hybrid particle/fiber MMC exhibited failure consistent with matrix overloading. Overaging of the A356 matrix coupled with progressive fracture of the SiC particles combined to create the matrix overload condition. No evidence of macro-fatigue crack initiation or growth was observed, and the matrix–particle interface appeared strong with no debonding, visible matrix phases, or porosity. An effective medium model was constructed to test the hypothesis that matrix overloading was the probable failure mode. The measured particle fracture rate was fit using realistic values of the SiC Weibull strength and modulus, which in turn predicted cycles to failure within the range observed in fatigue testing.