This paper presents the results of an experimental investigation on explosive breaching of p-section concrete beams. Twenty three p-section concrete beams with a 100 cm length were tested. TNT charges were placed at t...This paper presents the results of an experimental investigation on explosive breaching of p-section concrete beams. Twenty three p-section concrete beams with a 100 cm length were tested. TNT charges were placed at three positions: contact detonation in the center, contact detonation above the web and close-in detonation in the center. The external and internal breach parameters of the panels were evaluated by measuring the diameter of the ejection crater, spalling crater and breach hole created by the charge detonation. The experimental results were compared to predict values obtained by the analytical models proposed by McVay, Morishita and Remennikov. A modified breach with crater limit line and breach without crater limit line were put forward based on the experimental results. The maximum cross-sectional destruction area ratio(MCDAR) values were used to evaluate the damage degree. The maximum value of MCDAR reached 0.331 corresponding to the C5 experimental condition, of which explosion occurred above the web.展开更多
The welding temperature field and deformation of parallel arrangement small-section rectangular tubes is calculated by using a non-contact model. After comparing the computed results with the experimentally measured r...The welding temperature field and deformation of parallel arrangement small-section rectangular tubes is calculated by using a non-contact model. After comparing the computed results with the experimentally measured results, it shows that there exist big errors when applying this model to the numerical simulation of small-section rectangular tube＇ s welding temperature field and deformation. Based on a simple analysis of the errors, a contact model is presented. The heat transfer and stress analysis between small-section rectangular tubes and clamping fixture are simulated by using direct constraints method, and then the laws of the temperature distribution, which coincide with experiment, are obtained. A further numerical analysis of the stress and deformation are made, it shows that a ＂T＂ shaped stress-field is formed in the vicinity of the weld. As the stress-field departs from the centroid of tubes＇, this leads to the small rectangular tubes not only have a longitudinal deflection, but also have a transverse bending and deformation.展开更多
为了精确预测钢轨磨耗,以及为工务部门进行钢轨打磨和线路维护提供指导,建立了城市轨道交通车辆-轨道耦合动力学模型,采用Hertz-FASTRIP(FastStrip)-USFD(University of sheffield)模型对钢轨磨耗进行了计算,对城市轨道交通线路曲线段...为了精确预测钢轨磨耗,以及为工务部门进行钢轨打磨和线路维护提供指导,建立了城市轨道交通车辆-轨道耦合动力学模型,采用Hertz-FASTRIP(FastStrip)-USFD(University of sheffield)模型对钢轨磨耗进行了计算,对城市轨道交通线路曲线段钢轨磨耗的演变规律进行了预测。结果表明:LM型踏面与60 kg/m钢轨(以下简称“60钢轨”)接触时,其轮轨接触区域较大,且横移量较大时轮缘接触频繁。LM型踏面与60D钢轨接触时,其轮轨接触点在轨顶区域比较集中;相较60钢轨接触,其等效锥度更小,有利于车辆稳定运行;轮轨接触点集中在滚动圆附近,轮对横移量小于7 mm时,接触斑面积较小,法向应力较大,磨耗功较小。60D钢轨减轻了曲线外侧钢轨磨耗,且其在曲线外侧磨耗整体小于60钢轨。通过总重为5 Mt时,缓和曲线段60D钢轨最大磨耗深度为0.48 mm,相比60钢轨减小44.18%;圆曲线段60D钢轨最大磨耗深度为1.43 mm,相比60钢轨减小22.7%。60D钢轨可以进一步改善轮轨接触关系,并有效减小城市轨道交通线路曲线段的钢轨磨耗。展开更多
基金supported by The National Natural Science Foundation of China under Grant No.11390362 and No. 11221202
文摘This paper presents the results of an experimental investigation on explosive breaching of p-section concrete beams. Twenty three p-section concrete beams with a 100 cm length were tested. TNT charges were placed at three positions: contact detonation in the center, contact detonation above the web and close-in detonation in the center. The external and internal breach parameters of the panels were evaluated by measuring the diameter of the ejection crater, spalling crater and breach hole created by the charge detonation. The experimental results were compared to predict values obtained by the analytical models proposed by McVay, Morishita and Remennikov. A modified breach with crater limit line and breach without crater limit line were put forward based on the experimental results. The maximum cross-sectional destruction area ratio(MCDAR) values were used to evaluate the damage degree. The maximum value of MCDAR reached 0.331 corresponding to the C5 experimental condition, of which explosion occurred above the web.
文摘The welding temperature field and deformation of parallel arrangement small-section rectangular tubes is calculated by using a non-contact model. After comparing the computed results with the experimentally measured results, it shows that there exist big errors when applying this model to the numerical simulation of small-section rectangular tube＇ s welding temperature field and deformation. Based on a simple analysis of the errors, a contact model is presented. The heat transfer and stress analysis between small-section rectangular tubes and clamping fixture are simulated by using direct constraints method, and then the laws of the temperature distribution, which coincide with experiment, are obtained. A further numerical analysis of the stress and deformation are made, it shows that a ＂T＂ shaped stress-field is formed in the vicinity of the weld. As the stress-field departs from the centroid of tubes＇, this leads to the small rectangular tubes not only have a longitudinal deflection, but also have a transverse bending and deformation.
