为了研究Ⅰ-Ⅱ复合型裂纹动态扩展问题及裂纹止裂问题,侧开单裂纹半孔板(single cleavage semi circle compression,SCSCC)试样采用分离式霍普金森压杆(SHPB)实验系统进行冲击,完成SCSCC试样I–II复合型裂纹动态断裂实验,并针对实验进...为了研究Ⅰ-Ⅱ复合型裂纹动态扩展问题及裂纹止裂问题,侧开单裂纹半孔板(single cleavage semi circle compression,SCSCC)试样采用分离式霍普金森压杆(SHPB)实验系统进行冲击,完成SCSCC试样I–II复合型裂纹动态断裂实验,并针对实验进行数值分析,研究其扩展路径。为了验证数值模拟的可靠性,不仅进行有限尺寸中心裂纹板受冲击拉伸作用的动态有限差分法分析,而且在对SHPB实验进行数值分析后,将模拟监测点应变值与实验中入射杆应变片测得的应变值进行比较。结果表明:(1)验证分析中应力强度因子结果与其他测试的结果比较吻合,同时,模拟监测点记录下的应变值与SHPB实验中入射杆应变片记录下的应变数据相比较,两者吻合程度很高,说明使用数值方法模拟SHPB实验的可行性;(2)数值模拟的裂纹扩展路径与SHPB实验裂纹扩展路径基本吻合;(3)SCSCC试件在扩展过程中,裂纹尖端存在短暂停留现象,并最终朝着试件中轴线方向(最大应力区)移动;(4)SCSCC试件是一种便于研究裂纹动态扩展问题的构型,可以有效地求解不同复合程度的I–II复合型裂纹问题,为后续的止裂研究提供基础。展开更多
Polymer tribology is a fast growing area owing to increasing applications of polymers and polymer composites in industry, transportation, and many other areas of economy. Surface forces are very important for polymer ...Polymer tribology is a fast growing area owing to increasing applications of polymers and polymer composites in industry, transportation, and many other areas of economy. Surface forces are very important for polymer contact, but the real origin of such forces has not been fully investigated. Strong adhesive interaction between polymers leads to an increase in the friction force, and hence, the asperities of the material may be removed to form wear particles or transfer layers on the counterface. The theory of polymer adhesion has not been completely elucidated yet and several models of adhesion have been proposed from the physical or chemical standpoints. This paper is focused on the research efforts on polymer adhesion with emphasis on adhesion mechanisms, which are very important in the analysis of polymer friction and wear.展开更多
以126 k V模块化多断口直流真空断路器为研究对象,在连续过渡模型建模中考虑金属蒸气与离子密度的影响,给出中频真空电弧介质恢复动态数学模型;通过对其开断过程的数值仿真,得到断口间鞘层动态变化与介质恢复强度变化关系曲线以及弧后...以126 k V模块化多断口直流真空断路器为研究对象,在连续过渡模型建模中考虑金属蒸气与离子密度的影响,给出中频真空电弧介质恢复动态数学模型;通过对其开断过程的数值仿真,得到断口间鞘层动态变化与介质恢复强度变化关系曲线以及弧后电流、瞬态恢复电压与新阴极表面电场强度分布。采用对比分析方法,研究各断口间瞬态恢复电压分配规律以及弧后介质恢复强度影响因素。研究结果表明:由于线路阻抗产生的瞬态恢复电压等因素使得各断口间开断电压及电弧能量分配不均,某一断口所受电压及电弧能量高于其他断口,金属蒸气初始密度大且弧后电流下降率较大,瞬态恢复电压上升速率更快,鞘层发展速度缓慢,新阴极表面场强较高,易发生重击穿从而导致断路器开断失败。在换流回路中采用较大电容以保证TRV合理分配,进而提高多断口直流真空断路器开断性能。展开更多
文摘为了研究Ⅰ-Ⅱ复合型裂纹动态扩展问题及裂纹止裂问题,侧开单裂纹半孔板(single cleavage semi circle compression,SCSCC)试样采用分离式霍普金森压杆(SHPB)实验系统进行冲击,完成SCSCC试样I–II复合型裂纹动态断裂实验,并针对实验进行数值分析,研究其扩展路径。为了验证数值模拟的可靠性,不仅进行有限尺寸中心裂纹板受冲击拉伸作用的动态有限差分法分析,而且在对SHPB实验进行数值分析后,将模拟监测点应变值与实验中入射杆应变片测得的应变值进行比较。结果表明:(1)验证分析中应力强度因子结果与其他测试的结果比较吻合,同时,模拟监测点记录下的应变值与SHPB实验中入射杆应变片记录下的应变数据相比较,两者吻合程度很高,说明使用数值方法模拟SHPB实验的可行性;(2)数值模拟的裂纹扩展路径与SHPB实验裂纹扩展路径基本吻合;(3)SCSCC试件在扩展过程中,裂纹尖端存在短暂停留现象,并最终朝着试件中轴线方向(最大应力区)移动;(4)SCSCC试件是一种便于研究裂纹动态扩展问题的构型,可以有效地求解不同复合程度的I–II复合型裂纹问题,为后续的止裂研究提供基础。
基金partially supported by the grant of State Administration of Foreign Expert Affairs and Ministry of Education of China No.DL2017QHDX001the joint grant No.T16R-054 of Belarusian Republican Foundation for Fundamental Research and Russian Foundation for Basic Research
文摘Polymer tribology is a fast growing area owing to increasing applications of polymers and polymer composites in industry, transportation, and many other areas of economy. Surface forces are very important for polymer contact, but the real origin of such forces has not been fully investigated. Strong adhesive interaction between polymers leads to an increase in the friction force, and hence, the asperities of the material may be removed to form wear particles or transfer layers on the counterface. The theory of polymer adhesion has not been completely elucidated yet and several models of adhesion have been proposed from the physical or chemical standpoints. This paper is focused on the research efforts on polymer adhesion with emphasis on adhesion mechanisms, which are very important in the analysis of polymer friction and wear.
基金国家自然科学基金项目(5120716651307179)+3 种基金海军工程大学自然科学基金项目(435517F21)Project Supported by National Natural Science Foundation of China(5120716651307179)Natural Science Foundation of Naval University of Engineering(435517F21)
文摘以126 k V模块化多断口直流真空断路器为研究对象,在连续过渡模型建模中考虑金属蒸气与离子密度的影响,给出中频真空电弧介质恢复动态数学模型;通过对其开断过程的数值仿真,得到断口间鞘层动态变化与介质恢复强度变化关系曲线以及弧后电流、瞬态恢复电压与新阴极表面电场强度分布。采用对比分析方法,研究各断口间瞬态恢复电压分配规律以及弧后介质恢复强度影响因素。研究结果表明:由于线路阻抗产生的瞬态恢复电压等因素使得各断口间开断电压及电弧能量分配不均,某一断口所受电压及电弧能量高于其他断口,金属蒸气初始密度大且弧后电流下降率较大,瞬态恢复电压上升速率更快,鞘层发展速度缓慢,新阴极表面场强较高,易发生重击穿从而导致断路器开断失败。在换流回路中采用较大电容以保证TRV合理分配,进而提高多断口直流真空断路器开断性能。
