孤岛煤柱沿空掘巷围岩稳定与控制技术研究

孤岛煤柱结构特殊,在孤岛煤柱中掘巷,巷道应力集中程度高,围岩完整性差,围岩控制非常困难。本研究提出了孤岛煤柱沿空掘巷模型,以某矿为例,孤岛煤柱将完全处于塑性区和破碎区,整个煤柱不会存在弹性核区。通过PFC^2D颗粒流模拟软件模拟,得出整个煤柱可分为裂隙区和破碎区,巷道两侧破碎区范围在2.5 m左右,锚固范围需超出破碎区范围,因而需要帮锚索支护进行围岩控制,得出支护阻力和裂隙发育相互关系,分析认为,相比无支护一定的支护阻力对控制裂隙发育作用明显,但支护阻力到达一定数值后,增加支护阻力对进一步控制裂隙发育作用不大。通过现场观测,对比有无锚索不同支护条件下围岩变形情况,得出帮部布置锚索时,可以明显降低围岩变形速度10～15 mm /d,有效控制锚固范围内围岩的变形,保证巷道正常使用。     

大型复杂型面铝合金翻边件电磁成形塑性流动行为研究

大型复杂型面铝合金翻边件电磁成形是一个电磁场和结构场耦合作用下的复杂塑性成形过程。由于大型复杂型面的影响,使得铝合金翻边件在电磁成形过程中的塑性流动行为与传统带凸模翻边成形不同。基于松散耦合法建立耦合电磁场和结构场的大型复杂型面铝合金翻边件电磁成形有限元模型,研究采用1层、2层和3层平板线圈电磁翻边下的板料塑性流动行为,并采用试验研究揭示了不同压边力控制下板料法兰部分塑性流动规律。结果表明,当采用3层平板线圈时,翻边件的复杂型面部分完全贴膜,法兰部分材料进入凹模腔的部分更多,促使板料发生更多的塑性流动;不同压边力控制下,法兰部分由塑性流动产生不同的工件形式,在压边力不足时,法兰部分产生明显的起皱现象;通过合理的压边力控制,可得到贴膜性良好的大型复杂型面铝合金翻边件。     

巷道围岩塑性区与支护反力关系分析

基于D-P准则对侧压系数为1的圆形巷道围岩进行了塑性分析,得到了塑性区半径的解析解;根据具体的地质条件进行了案例分析,并对巷道围岩开挖后的应力场、位移场进行了数值模拟。结果表明：巷道围岩应力场、位移场均呈对称性分布;巷道周围围岩形成应力集中和降低,巷道开挖后应进行适时支护,并加强巷道肩部和底部拐角处的支护强度;垂直位移量大于水平位移量,随着围岩向深部发展,位移量逐渐减小直至为0。     

Influence of constitutive model in springback prediction using the split-ring test

The aim of this paper is to compare several plastic yield criteria to show their relevance on the prediction of springback behavior for a AA5754-0 aluminum alloy. An experimental test similar to the Demeri Benchmark Test [Demeri MY, Lou M, Saran MJ. A benchmark test for springback simulation in sheet metal forming. In: Society of Automotive Engineers, Inc., vol. 01-2657, 2000] has been developed. This test consists in cutting a ring specimen from a full drawn cup, the ring being then split longitudinally along a radial plan. The difference between the ring diameters, before and after splitting, gives a direct measure of the springback phenomenon, and indirectly, of the amount of residual stresses in the cup. The whole deep drawing process of a semi-blank and numerical splitting of the ring are performed using the finite element code Abaqus. Several material models are analyzed, all considering isotropic and kinematic hardening combined with one of the following plasticity criteria: von Mises, Hill’48 and Barlat’91. This last yield criterion has been implemented in Abaqus. Main observed data are force-displacement curves during forming, cup thickness according to material orientations and ring gap after splitting. The stress distributions in the cup, at the end of the drawing stage, and in the ring, after springback, are analyzed and some explanations concerning their influence on springback mechanisms are given.     

锥形塑料光纤过渡器的制作及测试

研究了可作为塑料光纤与石英光纤连接器件的锥形塑料光纤过渡器的制作方法及性能测试.采用重力垂直熔融拉锥法制作锥形塑料光纤过渡器,并研究其在实验室条件下的最佳工艺参数.重复实验发现,当加热电压为6.0 V,加热区中心温度在214 ℃附近,拉伸力为1.40 g左右时,塑料光纤的拉伸过程容易控制,拉伸后的塑料光纤表面具有良好的光学质量.测试显示锥形塑料光纤的透射率随着锥度的增大而减小,表面显微形貌良好,出射模式数明显减少,出射模模场强度集中在低阶模部分,可见光透射谱在400～500 nm的损耗加大.对测试结果的分析表明,采用重力垂直熔融拉锥法可以制备性能优良的锥形塑料光纤过渡器,实验得到的最佳工艺参数可为POF连接器、耦合器的实际生产提供参考.     

连续配筋混凝土机场道面节点的动载响应分析

针对连续配筋混凝土机场道面,建立有限元模型,并用ANSYS软件进行模拟分析．在移动荷载作用下,机场道面的面层上部节点竖向位移、应力最大,结合部位属于薄弱层,最容易破坏,交变的水平及横向应力是引起道面破坏的主要因素;节点塑性应变集中发生在面层中间节点附近,竖向最大,几乎是其余两个方向的两倍,水平向最小．钢筋单元应力时程曲线中,研究点最近的横向钢筋单元应力最大,且钢筋单元的应力远小于钢筋抗拉强度．     

对出口塑料集装袋抗光老化性的分析与研究

塑料集装袋的抗光老化性从光老化机理角度进行了分析,对抗光老化性能进行了试验研究,提出集装袋生产在抗光老化性能方面的一些规律,强调了尽快制定集装袋抗光老化性能的测试标准和加强对盛装出口货物的集装袋抗光老化性能测试的重要性.     

组合式塑料检查井简介

新一代组合式塑料检查井采用高分子树脂为原料,通过注塑工艺一次成型井体,现场分体组装而成。组合式检查井与排水管采用热熔连接或承插连接,具有优越的水密性,能更好地减少污水渗漏,防止地下水的二次污染,并有效地解决接口和传统检查井井体渗漏的问题,同时对减少路面沉降、提高道路质量也有明显的作用,其工程造价仅为混凝土预制井的1／2,与砖砌井的造价相当．极具推广价值。     

贫煤和瘦煤捣固炼焦的试验研究

对贫煤和瘦煤混合煤料的捣固炼焦进行了试验研究,结果表明,对混合煤料进行捣固处理,可以增大煤料的最大胶质层厚度和堆密度,降低煤料的最终收缩度;对于贫煤配加量不超过10％的混合煤料,捣固炼焦后可以生产出合格的冶金焦。     

Slenderness classification of unstiffened metal plates under shear loading

Buckling behavior of slender and compact carbon steel, stainless steel and aluminum plates under the action of in-plane shear is investigated. Unstiffened shear plates with respect to their slenderness parameter and buckling behavior are qualitatively and quantitatively divided into slender, moderate and stocky categories. Accordingly, slender plates have a low buckling capacity, followed by a large postbuckling reserve. Their ultimate load coincides with the formation of inclined yield bands. Stocky plates yield before buckling. They have some post-yield capacity, buckle plastically and their ultimate and critical loads are equivalent. Moderate plates have concurrent material yielding and geometrical buckling followed by a sudden loss of stiffness. They neither have post-yield nor postbuckling reserves. Since the proportional limit stress is observed to be the cause of bifurcation in stocky plates, it is suggested that in dealing with the slenderness parameter, the yield stress be replaced by the proportional limit stress.