A test platform is established as per the practical working condition ofelevating platform fire truck. The influences of pipes and load on dynamic characteristics ofload-sensing system are studied by series of step re...A test platform is established as per the practical working condition ofelevating platform fire truck. The influences of pipes and load on dynamic characteristics ofload-sensing system are studied by series of step response experiments. Experimental results showthat the feedback pipe makes the most important influence on the dynamic response speed ofload-sensing system. Its internal diameter should be optimized for given length of pipe. On theother hand, the stability of load-sensing pump is improved as the length of input pipe increases ina certain range. The influence of input pipe on the dynamic response speed is caused mainly by thepressure-wave travel time in the input pipe.展开更多
With von Mises yield criterion,the loading range of Net Section Collapse(NSC) Criteria is extended from combined tension and bending loadings to combined bending,torsion and internal pressure loadings.A new theoretica...With von Mises yield criterion,the loading range of Net Section Collapse(NSC) Criteria is extended from combined tension and bending loadings to combined bending,torsion and internal pressure loadings.A new theoretical analyzing method of plastic limit load for pressure pipe with incomplete welding defects based on the extended NSC Criteria is presented and the correlative formulas are deduced,the influences of pipe curvature,circumferential length and depth of incomplete welding defects on the plastic limit load of pressure pipe are considered as well in this method.Meanwhile,according to the orthogonal experimental design method,the plastic limit loads are calculated by the finite element method and compared with the theoretical values.The results show that the expressions of plastic limit load of pressure pipe with incomplete welding defects under bending,torsion and internal pressure based on extended NSC criteria are reliable.The study provides an important theoretical basis for the establishment of safety assessment measure towards pressure pipe with incomplete welding defects.展开更多
The loss of metal in a pipe due to corrosion usually results in localized thinned areas with various depths and an irregular shape on its surface. In this paper, a number of numerical models of pipes with different si...The loss of metal in a pipe due to corrosion usually results in localized thinned areas with various depths and an irregular shape on its surface. In this paper, a number of numerical models of pipes with different size defects are established. The limit loads of these pipes are researched using the nonlinear finite element method. The effect of defect parameters of the local wall-thinning pipes on the limit load is discussed. The results show that limit loads decrease obviously when the depths and lengths of the defect increase. However, when the defect length reaches a certain value, the effect of defect length on limit loads is not significant. These results are compared with the results of the method of API 579. When the defect length is adequately small, the results of FEM are in good agreement with the ones of APl 579, but when the defect depth and length is adequately large, the API 579 is not suitable.展开更多
Recently a research team at Ohio University,USA,conducted a unique full-scale feld load test to simulate the aeration pipe installations at a copper extraction mine operated in Chile.The overliner material taken from ...Recently a research team at Ohio University,USA,conducted a unique full-scale feld load test to simulate the aeration pipe installations at a copper extraction mine operated in Chile.The overliner material taken from the mine was used in recreating the in situ conditions.Electric heaters were utilized to raise the temperature inside each pipe to simulate the essential element of the copper extraction process.The maximum vertical deflection reached by the test pipes was close to 20%,when the simulated heap pile height was 80 m.The plastic pipes and the overliner material were also tested in the laboratory.Based on the results,the maximum heap pile fll depth was recommended for the aeration system.The results indicated that the vertical deflection was the primary performance index for the aeration pipes installed in heap piles at mines.Lastly,the pipe made of polypropylene resin was super.展开更多
The propagation of stress waves in a large-diameter pipe pile for low strain dynamic testing cannot be explained properly by traditional 1D wave theories. A new computational model is established to obtain a wave equa...The propagation of stress waves in a large-diameter pipe pile for low strain dynamic testing cannot be explained properly by traditional 1D wave theories. A new computational model is established to obtain a wave equation that can describe the dynamic response of a large-diameter thin-walled pipe pile to a transient point load during a low strain integrity test. An analytical solution in the time domain is deduced using the separation of variables and variation of constant methods. The validity of this new solution is verifi ed by an existing analytical solution under free boundary conditions. The results of this time domain solution are also compared with the results of a frequency domain solution and fi eld test data. The comparisons indicate that the new solution agrees well with the results of previous solutions. Parametric studies using the new solution with reference to a case study are also carried out. The results show that the mode number affects the accuracy of the dynamic response. A mode number greater than 10 is required to enable the calculated dynamic responses to be independent of the mode number. The dynamic response is also greatly affected by soil properties. The larger the side resistance, the smaller the displacement response and the smaller the refl ected velocity wave crest. The displacement increases as the stress waves propagate along the pile when the pile shaft is free. The incident waves of displacement and velocity responses of the pile are not the same among different points in the circumferential direction on the pile top. However, the arrival time and peak value of the pile tip refl ected waves are almost the same among different points on the pile top.展开更多
The dynamic strain field under the action of blasting load is measured by means of a super-dynamic strain system and a CS2092H dynamic measuring analysis system, and the relation between the peak valwe of strain and t...The dynamic strain field under the action of blasting load is measured by means of a super-dynamic strain system and a CS2092H dynamic measuring analysis system, and the relation between the peak valwe of strain and the quantity of explosive charge is obtained. And the authors probe into the mechanism of soot descaling of soot-delivery pipe under the action of blasting, and offer an effective method to clean soot in soot-delivery pipe. The study provides a theoretical basis for a further study on blasting descaling or soot-delivery pipe.展开更多
The objective of the present experimental work is to investigate the performance of a wrapped screen heat pipe for atmospheric air heating to compare with the limits of this pipe. The experiment was conducted using co...The objective of the present experimental work is to investigate the performance of a wrapped screen heat pipe for atmospheric air heating to compare with the limits of this pipe. The experiment was conducted using copper pipe material and acetone as working fluid at different vapor temperatures. The testing also consists of a heater, a blower for heat removal (condenser), temperature measuring device, a vapor temperature probe, acetone charging system, and a vacuum pump. The copper outside diameterof the pipe is 0.022 m, with a total length of 0.6 m. The results showed that the pipe wall temperature (Tw) for a wrapped screen heat pipe has a rapid increase and takes 50 min to reach steady state at (Q = 63 W). The vapour temperature of working fluid increases as the heat load increases at constant air velocity. It was also been found that the range of vapour temperature deceases as the filling ratio increases that means the increasing of the filling ratio results the decrease of the maximum vapour temperature and the variation in the vapour temperature. The best recorded filling ratio is 0.6 which has the lowest vapour temperature at highest heat load. The maximum heat transport limit for this pipe is 80 W and the maximum temperature difference for air is 5。C.展开更多
煤矿井下作业环境复杂多变,钻探成为煤矿开采的必备环节。钻杆加卸是钻探过程中的重要步骤,传统的人工钻杆加卸方式不仅耗时费力,而且劳动强度极大,对工人的身体健康构成严重威胁。为了提高煤矿井下钻机的钻杆加卸效率,降低劳动强度,提...煤矿井下作业环境复杂多变,钻探成为煤矿开采的必备环节。钻杆加卸是钻探过程中的重要步骤,传统的人工钻杆加卸方式不仅耗时费力,而且劳动强度极大,对工人的身体健康构成严重威胁。为了提高煤矿井下钻机的钻杆加卸效率,降低劳动强度,提升作业安全性,探讨并总结当前煤矿井下智能化钻机配套钻杆自动加卸技术,发现多轴液驱机械手式换杆技术具有高度的灵活性和适应性,可作为解决多规格钻具自动加卸问题的有效方案。基于当前机械手关键技术的研究,分析得出动态路径规划方法是多轴机械手式钻杆加卸系统研究的难点,在总结当前机械手动态轨迹规划领域研究进展的基础上,分析现有路径规划方法的优缺点,特别是在动态环境下的适应性表现。在此基础上,研究了基于快速随机搜索树(Rapidly-exploring Random Tree,RRT)算法的混合轨迹规划策略在复杂环境下的应用,展示了这些方法在提升机械手路径规划精度、减少操作时间以及增强系统鲁棒性方面展现出的显著优势。针对未来研究方向,提出了进一步提升机械手动态轨迹规划算法性能,增强机械手自主作业能力,推动煤矿井下自动化技术全面应用的建议。展开更多
基金This project is supported by National Natural Science Foundation of China(No.59875076).
文摘A test platform is established as per the practical working condition ofelevating platform fire truck. The influences of pipes and load on dynamic characteristics ofload-sensing system are studied by series of step response experiments. Experimental results showthat the feedback pipe makes the most important influence on the dynamic response speed ofload-sensing system. Its internal diameter should be optimized for given length of pipe. On theother hand, the stability of load-sensing pump is improved as the length of input pipe increases ina certain range. The influence of input pipe on the dynamic response speed is caused mainly by thepressure-wave travel time in the input pipe.
基金Project (No. X106871) supported by the Natural Science Foundation of Zhejiang Province,China
文摘With von Mises yield criterion,the loading range of Net Section Collapse(NSC) Criteria is extended from combined tension and bending loadings to combined bending,torsion and internal pressure loadings.A new theoretical analyzing method of plastic limit load for pressure pipe with incomplete welding defects based on the extended NSC Criteria is presented and the correlative formulas are deduced,the influences of pipe curvature,circumferential length and depth of incomplete welding defects on the plastic limit load of pressure pipe are considered as well in this method.Meanwhile,according to the orthogonal experimental design method,the plastic limit loads are calculated by the finite element method and compared with the theoretical values.The results show that the expressions of plastic limit load of pressure pipe with incomplete welding defects under bending,torsion and internal pressure based on extended NSC criteria are reliable.The study provides an important theoretical basis for the establishment of safety assessment measure towards pressure pipe with incomplete welding defects.
基金supported by the National High Technol-ogy Research and Development Program of China(2007AA04Z404)Natural Science Basic Research Plan in Shaanxi Province of China (SJ08A17)the Technical Innovation Foundation of NWPU(2008KJ02019)
文摘The loss of metal in a pipe due to corrosion usually results in localized thinned areas with various depths and an irregular shape on its surface. In this paper, a number of numerical models of pipes with different size defects are established. The limit loads of these pipes are researched using the nonlinear finite element method. The effect of defect parameters of the local wall-thinning pipes on the limit load is discussed. The results show that limit loads decrease obviously when the depths and lengths of the defect increase. However, when the defect length reaches a certain value, the effect of defect length on limit loads is not significant. These results are compared with the results of the method of API 579. When the defect length is adequately small, the results of FEM are in good agreement with the ones of APl 579, but when the defect depth and length is adequately large, the API 579 is not suitable.
文摘Recently a research team at Ohio University,USA,conducted a unique full-scale feld load test to simulate the aeration pipe installations at a copper extraction mine operated in Chile.The overliner material taken from the mine was used in recreating the in situ conditions.Electric heaters were utilized to raise the temperature inside each pipe to simulate the essential element of the copper extraction process.The maximum vertical deflection reached by the test pipes was close to 20%,when the simulated heap pile height was 80 m.The plastic pipes and the overliner material were also tested in the laboratory.Based on the results,the maximum heap pile fll depth was recommended for the aeration system.The results indicated that the vertical deflection was the primary performance index for the aeration pipes installed in heap piles at mines.Lastly,the pipe made of polypropylene resin was super.
基金The 111 Project under Grant No.B13024the National Natural Science Foundation of China under Grant No.51378177+1 种基金the Program for New Century Excellent Talents in University under Grant No.NCET-12-0843the Fundamental Research Funds for the Central Universities under Grant No.106112014CDJZR200007
文摘The propagation of stress waves in a large-diameter pipe pile for low strain dynamic testing cannot be explained properly by traditional 1D wave theories. A new computational model is established to obtain a wave equation that can describe the dynamic response of a large-diameter thin-walled pipe pile to a transient point load during a low strain integrity test. An analytical solution in the time domain is deduced using the separation of variables and variation of constant methods. The validity of this new solution is verifi ed by an existing analytical solution under free boundary conditions. The results of this time domain solution are also compared with the results of a frequency domain solution and fi eld test data. The comparisons indicate that the new solution agrees well with the results of previous solutions. Parametric studies using the new solution with reference to a case study are also carried out. The results show that the mode number affects the accuracy of the dynamic response. A mode number greater than 10 is required to enable the calculated dynamic responses to be independent of the mode number. The dynamic response is also greatly affected by soil properties. The larger the side resistance, the smaller the displacement response and the smaller the refl ected velocity wave crest. The displacement increases as the stress waves propagate along the pile when the pile shaft is free. The incident waves of displacement and velocity responses of the pile are not the same among different points in the circumferential direction on the pile top. However, the arrival time and peak value of the pile tip refl ected waves are almost the same among different points on the pile top.
文摘The dynamic strain field under the action of blasting load is measured by means of a super-dynamic strain system and a CS2092H dynamic measuring analysis system, and the relation between the peak valwe of strain and the quantity of explosive charge is obtained. And the authors probe into the mechanism of soot descaling of soot-delivery pipe under the action of blasting, and offer an effective method to clean soot in soot-delivery pipe. The study provides a theoretical basis for a further study on blasting descaling or soot-delivery pipe.
文摘The objective of the present experimental work is to investigate the performance of a wrapped screen heat pipe for atmospheric air heating to compare with the limits of this pipe. The experiment was conducted using copper pipe material and acetone as working fluid at different vapor temperatures. The testing also consists of a heater, a blower for heat removal (condenser), temperature measuring device, a vapor temperature probe, acetone charging system, and a vacuum pump. The copper outside diameterof the pipe is 0.022 m, with a total length of 0.6 m. The results showed that the pipe wall temperature (Tw) for a wrapped screen heat pipe has a rapid increase and takes 50 min to reach steady state at (Q = 63 W). The vapour temperature of working fluid increases as the heat load increases at constant air velocity. It was also been found that the range of vapour temperature deceases as the filling ratio increases that means the increasing of the filling ratio results the decrease of the maximum vapour temperature and the variation in the vapour temperature. The best recorded filling ratio is 0.6 which has the lowest vapour temperature at highest heat load. The maximum heat transport limit for this pipe is 80 W and the maximum temperature difference for air is 5。C.
文摘煤矿井下作业环境复杂多变,钻探成为煤矿开采的必备环节。钻杆加卸是钻探过程中的重要步骤,传统的人工钻杆加卸方式不仅耗时费力,而且劳动强度极大,对工人的身体健康构成严重威胁。为了提高煤矿井下钻机的钻杆加卸效率,降低劳动强度,提升作业安全性,探讨并总结当前煤矿井下智能化钻机配套钻杆自动加卸技术,发现多轴液驱机械手式换杆技术具有高度的灵活性和适应性,可作为解决多规格钻具自动加卸问题的有效方案。基于当前机械手关键技术的研究,分析得出动态路径规划方法是多轴机械手式钻杆加卸系统研究的难点,在总结当前机械手动态轨迹规划领域研究进展的基础上,分析现有路径规划方法的优缺点,特别是在动态环境下的适应性表现。在此基础上,研究了基于快速随机搜索树(Rapidly-exploring Random Tree,RRT)算法的混合轨迹规划策略在复杂环境下的应用,展示了这些方法在提升机械手路径规划精度、减少操作时间以及增强系统鲁棒性方面展现出的显著优势。针对未来研究方向,提出了进一步提升机械手动态轨迹规划算法性能,增强机械手自主作业能力,推动煤矿井下自动化技术全面应用的建议。
