Tensile strength and bonding in compacts: a comparison of diametral compression and three-point bending for plastically deforming materials

The tensile strength of tablets is frequently used as a measure of the bonding achieved during compaction. Tablets from two plastically deforming materials and one brittle material have been subjected to tensile strength testing using diametral compression and three-point bending. The plastically deforming materials exhibited marked inhomogeneities, with the surfaces of the tablets considerably more compact than the inner material. The results from the two tests were different, with the three-point bending test giving higher results for tensile strength. The rate of change of tensile strength with overall tablet porosity was, however, the same for the two tests. Diametral compression would thus appear to give a reasonable estimate of bonding despite the non-homogenous nature of tablets prepared from plastically deforming materials.     

水泥抗折强度测量结果不确定度评定

本文就水泥胶砂抗折强度依据GB/T17671-1999《水泥胶砂强度检验方法》(ISO法)进行测试,按JJF1059-1999《测量不确定度评定与表示》对水泥胶砂抗折强度的测量结果不确定度的评定方法。     

Numerical and experimental investigation of the strength of corrugated board packages

The buckling behaviour of corrugated paper packages was studied by means of an experimental and theoretical analysis. Mechanical behaviour of paperboard was first evaluated experimentally, then a local geometry FEM model, able to reproduce with a very good accuracy buckling loads obtained experimentally in the standard edge compression test, was developed. In order to investigate the buckling of a complete package, a finite element ‘corrugated board’ was introduced by means of a dedicated homogenization procedure. The FEM model of the package, assembled with this new element, can accurately predict the experimental data of incipient buckling observed during the standard box compression test, despite the few degrees of freedom and the minimal computational effort. Copyright © 2003 John Wiley & Sons, Ltd.     

瓦楞纸箱抗压强度的计算方法及计算机辅助设计

论述了抗压强度的计算方法 ,其中 Kellicutt公式和 Makee公式为最主要的计算方法 ,并对一个实例进行计算 ,比较两种数学模型得到的结果 ,由此得到一些有用结论 ,并提出了相应的计算机程序 ,使计算准确合理     

先进高强度钢板弯曲类回弹特性的试验研究

随着先进高强钢板在汽车及航天航空领域的广泛应用,回弹导致的成形精度问题日益突出.为了获取先进高强钢的弯曲回弹特性,通过采用U形件回弹模型,针对600MPa级别的3种典型高强钢(DP钢、TRIP钢、HSLA钢)进行了回弹试验研究.实验结果表明:在相同变形条件下,TRIP钢弯曲回弹最大,DP钢次之,HSLA的弯曲回弹最小;不同工艺条件、不同材料性能参数对弯曲回弹呈单调的影响规律,而润滑条件对弯曲回弹的影响趋势并未出现一致性规律.     

Estimation of the compression strength of corrugated fibreboard boxes and its application to box design using a personal computer

Many papers have been published on the compression strength of corrugated fibreboard boxes, using such formulae as Kellicut's equation and McKee's equation for the calculation. These equations, however, require known values of the strength of linerboard or corrugated fibreboard, they do not include the influence of moisture content and they are inadequate in the case of wrap-around boxes. The present author measured the mechanical properties of a large number of fibreboard boxes, and has derived a statistical formula useful for estimating the compression strength of a box based on its specifications — grade of corrugated fibreboard, size of box, type of box, printed area and moisture content. The calculation gives fairly good agreement with experimental results. The estimation technique has further been converted into a personal computer program, which renders the design of corrugated fibreboard boxes an easier task.     

Influence of core hardness on bending strength of tooth in cylindrical gears under quasistatic loading conditions

Dynamically loaded mechanical components can withstand overloading if they are designed by considering sufficient safety of margin for the static strength. In this study, the influence of core hardness on bending static strength of the tooth in cylindrical hardened gears is investigated experimentally. For this purpose, shot peened and unpeened gears having different core hardness and comparable surface hardness are tested on a pulsator test rig, which provides a quasi‐static loading condition by means of a servomotor. All test gears are made of 20MnCr5 steel and have the same geometry (module m = 5 mm). Average static load for fracture is measured. The relationship between the applied load and bending stress is known. Hardness profiles from the surface to the core of the test gears were measured. Strength is assumed to be a function of depth depending hardness to justify fracture initiation on the surface under bending static load conditions. Tooth root failures originating from the surface were observed experimentally. It is found that the shot peening treatment and core hardness have no considerable influence on the bending strength of the tooth under static loading conditions.     

超高强度硼钢板热弯曲数值模拟

为研究热自由弯曲和热接触弯曲方法的淬火效果和成形精度,应用ABAQUS软件,对超高强度硼钢板U形件的热弯曲过程进行了数值模拟研究.研究表明:热接触弯曲改善了热弯曲零件底部的淬火效果,且热接触弯曲可获得比热自由弯曲更好的成形精度;不同压边力下热接触弯曲回弹均随着压边力的增加而逐渐减小;数值模拟结果与实验结果吻合较好,验证了有限元模型的可靠性.     

Device for determining the ultimate strength in bending for refractories at elevated temperature

A device is developed and prepared for determining the ultimate strength in bending of refractories at elevated temperature according to GOST R 50523-93 and ISO 5013-85, that in functional possibilities, metrological characteristics, accuracy of determining physicomechanical and thermomechanical properties of test objects and other parameters surpasses existing Russian analogs. Translated from Izmeritel’naya Tekhnika, No. 2, pp. 34–37, February, 2009.     

Quasi-isotropic bending responses of metallic sandwich plates with bi-directionally corrugated cores

In order to reduce anisotropic behaviors of sandwich plates with open channel cores under the bending load, bi-directionally corrugated cores were introduced. Bi-directionally corrugated core has two additional design parameters related with a corrugation pass than uni-directionally corrugated core, so that its properties with respect to core orientations can be controlled. Sandwich plate with bi-directionally corrugated core is designed optimally so that beam buckling of face sheets is reduced drastically and anisotropic buckling behavior in the face sheets is minimized. The cores fabricated by a sectional forming process were bonded with face sheets by adhesive bonding. Three-point bending experiments were carried out with respect to core orientations. It has been shown from the experiments that sandwich plates with bi-directionally corrugated cores exhibit quasi-isotopic bending behaviors and structural performances in sandwich plates.     

制备工艺对SiCf/Si-O-C复合材料弯曲强度的影响

以聚硅氧烷为先驱体，采用先驱体转化法制备SiCf／Si-O-C复合材料。研究制备工艺参数模压压力、裂解时升温制度、裂解温度、保温时间对材料的力学性能的影响。通过对复合材料微观结构的分析研究，发现界面结构与致密度是影响SiCf／Si-O-C复合材料性能的主要因素。     

Effect of load history on the performance of corrugated fibreboard boxes

This paper investigates the effect of load histories (static and dynamic) on the compression strength and shock absorption properties of corrugated fibreboard boxes. Experiments were set up in the laboratory to simulate compressive forces and drops that occur during normal transportation of packaged products. The results show that static compression forces (not to failure) do not have significant influence on the compressive strength or shock absorption of corrugated boxes, and that dynamic compression forces do have a significant influence on these performance factors. This study was limited to one box size and style and suggests that more extensive research be undertaken to determine the effects of previous loading histories on a broad range of box configurations.     

Industrial experiences of bending fatigue strength in table liner for cement mill

A table liner for the vertical roller mill has been used to grind natural limestone. Unexpected fatigue failure accidents have occurred during portland cement manufacturing process. The design life of a table liner is 4 × 10⁷ cycles, but the actual fatigue life of a table liner is 2 × 10⁶ to 8 × 10⁶ cycles. The fatigue crack of a table liner initiates from the outside edge of the grinding path of the limestone. When such a crack occurs, the table liner has to be replaced, and this requires 30% of the total maintenance cost of the vertical roller mill. Therefore, this study examines the fatigue failure of a table liner by plane‐bending fatigue test, stress measurement test, finite element analysis and fatigue fracture analysis.     

Limit load analysis of strength undermatched welded T-joints under bending

An increasing amount of laser beam welded T‐joints (e.g. skin‐stringer) of aluminium alloys are now in use in advanced fuselage applications designed as ‘integral structures’ for weight and cost savings. It is known that weld joints generally show lower strength (undermatching) than base metal in both laser beam and friction stir welded joints of 6xxx series Al‐alloys. Damage tolerance considerations in terms of the residual strength of such joints require limit load solutions to be used in engineering fitness‐for‐service (FFS) analysis. The paper, therefore, provides an upper bound limit load solution in closed form for welded T‐joints (idealized) with strength undermatching and subject to a bending moment. In addition to the necessary requirements of the upper bound theorem, the kinematically admissible velocity field chosen leads to a stress field, which satisfies the equilibrium equations and some stress boundary conditions in the plastic zone. This is an advantage of the solution and, therefore, it is expected that the upper bound obtained is close to the exact limit load of such joints.     

Some experimental aspects of the compression behaviour of boxes made up of G‐flute corrugated boards

The load‐bearing capacity of boxes made up of thin‐walled G‐flute corrugated boards was investigated by performing monotonic and cyclic compression tests on boxes of various geometries. Results provided a large experimental database on the influence of the box dimensions and compression velocities on buckling parameters such as critical load and the corresponding critical axial deformation. Cyclic loading tests permitted the detection of the onset of an irreversible strain state, which could be related to damage initiation and propagation in the microstructure of the panels of boxes. Moreover, main differences, which could be observed between G‐flute corrugated boards and folding boards, were emphasized. Finally, the ability of some usual modelling approaches to predict the critical load of boxes was discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

中国瓦楞纸箱行业的新目标

针对瓦楞纸箱行业的发展目标,需使瓦楞纸和工业适应迅猛发展的经济,未来的瓦楞纸和工业发展实现3个到位,建设3大体系. 实现3个到位: 第一,瓦楞纸箱--瓦楞纸和箱板纸的消费定量必须到位. 现在加工瓦楞纸箱的瓦楞纸和箱板纸的消费定量(克重)仍然偏高,纸箱瓦层偏多.     

低温地面支持设备系统CGSE中阀箱的方案和强度设计

低温地面支持设备系统CGSE是用于冷却第二代阿尔法磁谱AMS02的磁体组件并将超流氦注入AMS02磁体杜瓦的低温设备系统。介绍用于CGSE系统中气氦管路阀箱和液氦管路阀箱,介绍了阀箱的技术要求、方案设计、结构特征,并进行了强度校核计算,两个阀箱的筒体和下封头的壁厚为4mm,上封头的壁厚为5mm,能满足两个阀箱承受0．1MPa外压的强度要求。     

基于长冲程振动台导轨弯曲校正的低频振动传感器校准方法

针对长冲程振动台的导轨弯曲对于基于振动台的低频振动传感器灵敏度幅值校准的影响,采用机器视觉方法测量导轨弯曲.通过建立校正模型消除导轨弯曲的影响,以提高灵敏度幅值的校准精度.导轨弯曲测量结果表明,被校振动传感器的负载越大,导轨弯曲越大,对灵敏度幅值校准的影响越大.与地球重力法的对比试验表明,在0.04 ～2 Hz范围内弯...