自走铁矿结构面的赤平极射投影分析

采用国际岩石力学学会推荐的详细线观测法对自走铁矿的节理裂隙进行了调查。用频率分布直方图统计了结构面间距和倾角。认为巷道为节理密集、发育的碎裂岩体。借助理正软件对调查数据进行分析,绘制出节理裂隙赤平极射投影极点等密度图和优势产状的分组表。将用于隧道稳定性判断的方法引入到巷道中,对自走铁矿的岩体稳定性进行了分析,认为节理对巷道的稳定性不利,建议巷道进行锚杆加固或喷砼等措施。     

中国华能集团某办公楼关键节点弹塑性分析

华能集团人才创新创业基地办公楼东侧结构单元,采用混合结构体系(局部6-15轴至6-19轴为四层顶托柱转换)。因造型奇特,受力复杂,结构存在多处关键构件,如悬挑桁架与剪力墙核心筒连接处节点、球形办公室与支撑桁架连接节点等,为保证结构的安全性,利用ABAQUS分析软件,对这些关键节点进行了有限元建模,在大震工况下对关键节点的性能进行了弹塑性有限元分析。结果表明:在大震下,各关键节点除局部单元出现塑性外,节点的整体性能处于弹性状态,满足大震不屈服的抗震性能要求。     

钢轨焊后热处理现状及分析

我国铁路建设施工中钢轨焊后热处理主要采用中频电感应加热和火：焰加热两种方式。中频电感应加热方式的自动化程度较高，不易受操作人员的素质和环境因素的影响；而火焰加热方式多为人工操作，且不易形成量化控制标准，所以受到人为和环境因素的影响较多。伴随中频感应加热技术的进步和铁路施工质量要求的不断提高，中频电感应加热方式在钢轨焊后热处理领域应得到进一步推广。     

Grease Lubrication of a Multiple-Branch Mechanical System

Abstract

Greasing is the preferred lubrication method in many mechanical devices. To simplify the design, some systems use multiple branches so that the grease must go through channels or different restrictions to reach target spots. Conceptually, flow restriction can be included in the design to achieve optimal grease distribution, but the detailed design can be complicated. For example, appropriate dimensions of various machine elements and their manufacturing tolerances must be considered along with the property of the grease, its feeding device, and its seal design. Currently, grease-feeding design relies heavily on experimental tests. A system-level modeling and analysis is desirable to understand the sensitivity of design parameters to the overall lubrication performance. In the study of grease lubrication of a universal joint, we have developed a semi-empirical model to address this challenge. The model is found useful to provide design guidance. The methodology can be extended and applied to more complicated cases. Laboratory tests on grease flow rates were conducted for a number of design alternates. Based on these data, the functional relationship of an equivalent discharge coefficient and the system parameters can be determined. Charts generated by the analytical model provide designers with a convenient tool for making design decisions.     

Behavior of thick-walled CHS X-joints under cyclic out-of-plane bending

This paper deals with experimental investigations to study the seismic behavior of thick-walled circular hollow section (CHS) X-joints subjected to out-of-plane bending (OPB). Important geometric parameters were varied in designing three full-scale joint specimens in order to evaluate their effect on connection behavior. Test results indicated that the failure modes and the connection efficiency of these joints significantly depended on the brace-to-chord thickness ratio τ and the brace-to-chord diameter ratio β. The tension fracture was identified as a critical failure mode for thick-walled X-joints with large β. CHS X-joints with larger β ratio were found to demonstrate better connection ductility and more satisfactory energy dissipating capacity than those joints with smaller β ratio under cyclic OPB loading. This observation was further verified by the proposed simplified analytical model results. Finite element (FE) analyses were performed to simulate the experimental behavior and facilitate the interpretation of the important test observations.     

Determination of cohesive laws of composite bonded joints under mode II loading

In this work, mode II cohesive laws of carbon–epoxy composite bonded joints were obtained using the direct method applied to the end notched flexure (ENF) test. The direct method is based on the differentiation of the relation between the evolution of the fracture energy (J_II) and the crack tip opening displacement in mode II (CTOD_II) during the test. A data reduction scheme based on equivalent crack length concept was used to obtain the evolution of the fracture energy during the test. The method allows overcoming problems related to identification of crack tip in mode II tests and the presence of a non-negligible fracture process zone (FPZ), which both difficult the right estimate of J_II. The digital image correlation technique (DIC) was used to monitor the CTOD_II, which was synchronized with the load–displacement data. A trapezoidal cohesive law was fitted to the experimental one in order to perform numerical simulations using finite element analysis. The main goal was to validate all the procedure used to get the cohesive laws. The good agreement obtained between the numerical and experimental load-CTOD_II curves and between the cohesive laws demonstrates the adequacy of the proposed procedure concerning the evaluation of the composite bonded joints cohesive laws under mode II loading.     

CEA studies and qualifications prior to the JT-60SA TF coils manufacture

Following the first conceptual design activity in which the general design of the JT-60SA TF system was defined in agreement with all the participants in the project (CEA, ENEA, F4E), a second phase dealing with the detailed design was engaged by each of the voluntary contributors. For the French part which includes the procurement of 9 of the TF winding packs and their integration in the casing, an industrial contract was signed mid 2011 with Alstom (France). Several actions have been carried out to prepare the manufacturing phase.To precisely define one of the main interfaces which is the temporary electrical connection of the coils to the current leads during cold test in the CEA facility as well as their final connection to the feeders at the Naka site, a design compatible with both requirements was developed by CEA, supported by the previous developments led on the joints and assembly techniques.In addition to prepare the coils manufacture, hydraulic qualification was led on the first conductor qualification length to set the parameters which will be used by the coils manufacturer for conductor acceptance.At last, mechanical characterizations of both the conductor and of the empty compacted jacket were performed in order to define as precisely as possible the elastic and plastic properties of these components. These are crucial properties used during the bending process which is one of the most important operations during the winding pack manufacture. These data will be very helpful for the winding machine parameters settings as well as for designing the local bending tooling needed to shape the conductors extremities at the connection area and at the double pancakes joggles.     

高强混凝土L形柱框架节点的非线性有限元分析

在华东交通大学所做试验的基础上,利用有限元分析软件ANSYS对L形柱框架节点进行了非线性有限元分析,主要考察裂缝发展机理及轴压比对节点受剪承载力的影响。经过分析,得到了高强混凝土L形柱框架节点受剪承载力在不同轴压比情况下的变化规律。     

Multi-level analysis of low-cost Z-pinned composite joints: Part 2: Joint behaviour

In the framework of the E-U program ALCAS (Advanced Low-Cost Aircraft Structure), a new Z-pinning technique was developed by EADS Innovation Works. This technology was used to manufacture low-cost Z-pinned junction demonstrators (L and T shaped specimens) typical of aeronautical structures. In order to understand load transfer mechanisms in this kind of assembly, a multi-level analysis was performed. In the first part of this study, tension and shear pin behaviour was investigated as well as pin pull-out from neat resin or laminate. An analytical model was proposed to predict the maximum load capability of a single pin for an insertion depth of less than 8 mm which correspond to the usual technology. Now, in this second part, we demonstrate that the behaviour of the junction under pull-out, shear and unfolding is globally homothetic to the mechanical behaviour of a pin. This study provides the basis for a pre-sizing methodology for Z-pinned junctions under complex loading.     

Experimental testing of joints for seismic design of lightweight structures. Part 1. Screwed joints in straps

Connections in x-braced shear walls play a crucial role in the seismic performance of lightweight structures: they should be strong enough to allow energy dissipation via plastification of the diagonal straps. An extensive experimental research on tensile screwed joints between straps is reported here. Two dominant failure modes are identified: (1) tilting and net section failure (T+NSF) and (2) tilting, bearing and pull out (T+B+PO). The analysis in terms of strength and ductility shows that T+NSF joints are suitable for seismic design, because the straps yield before the connections fail. T+B+PO joints, on the contrary, are not suited because the connection fails before the straps can yield. The influence of various design parameters (strap thickness, number and diameter of screws, steel grade) in the failure mode is studied, and design criteria to induce a T+NSF response are given.