Rockfall represents a significant geological hazard in mountainous regions,characterized by a sudden and unpredictable feature.The process of dynamic fragmentation and energy conversion in a rockfall event remains com...Rockfall represents a significant geological hazard in mountainous regions,characterized by a sudden and unpredictable feature.The process of dynamic fragmentation and energy conversion in a rockfall event remains complex and not fully understood.This study aims to gain a further understanding of the energy transfer mechanism during rockfall impact and fragmentation by impact tests using a variety of rock-like sphere specimens.The experiments mainly focus on the quantitative correlation between fragmentation degree and influence factors,i.e.impact angle and velocity on steel and granite slabs.The analysis focuses on the energy distribution characteristics,energy dissipation mechanisms,and the energy conversion rate of the fragments during impact and fragmentation.The results show that there is a significant correlation between the energy conversion rate and the fragmentation degree.In normal impact tests,elasto-plastic deformation energy and fracture energy are found to be two primary categories of energy dissipation.The proportion of total kinetic energy after impact is inversely proportional to the initial energy.A comparative analysis between normal and inclined slab impact tests reveals that the impact angle significantly influences the energy conversion rate,which controls the fragmentation degree as well.In addition,the fragmentation degree is inversely proportional to the restitution coefficient.These findings contribute to a better understanding of the energy conversion mechanism during rockfall impact and fragmentation,providing valuable insight for the development of effective strategies to mitigate such rockfall hazards.展开更多
This letter presents a theoretical model of the normal （head-on） collisions between two soft spheres for predicting the experimental characteristic of the coefficient of restitution dependent on impact velocity. Aft...This letter presents a theoretical model of the normal （head-on） collisions between two soft spheres for predicting the experimental characteristic of the coefficient of restitution dependent on impact velocity. After the contact force law between the contacted spheres during a collision is phenomenologically formulated in terms of the compression or overlap displacement under considera- tion of an elastic-plastic loading and a plastic unloading subprocesses, the coefficient of restitution is gained by the dynamic equation of the contact process once an initial impact velocity is input. It is found that the theoretical predictions of the coefficient of restitution varying with the impact velocity are well in agreement with the existing experimental characteristics which are fitted by the explicit formula.展开更多
This study was carried out to investigate the effect of heat treatment (Normalizing and Hardening) on the mechanical properties of springs. The springs were made from mild steel rod having a diameter of 6 mm, a total ...This study was carried out to investigate the effect of heat treatment (Normalizing and Hardening) on the mechanical properties of springs. The springs were made from mild steel rod having a diameter of 6 mm, a total of 15 springs were made. The springs were then subjected to various heat treatment processes which included;normalizing, hardening and tempering. The heat treated springs were then subjected to various test in other to determine their mechanical properties, these included;impact toughness test, hardness test and tension test. The normalized spring had more strength, was harder and was much tougher than both the annealed and as received springs. The water quenched springs were the hardest of all the heat treated springs, were very brittle and had the lowest percentage elongation. Their strength was also lower than that of the normalized and as received springs. The water quenched and tempered springs had better mechanical properties required for spring making, they had the optimum combination of hardness, strength and toughness when compared with the other heat treated springs.展开更多
[目的/意义]通过InciteTM数据库中学科规范化的引文影响系数指标研究中国大陆期刊对各一级学科的影响力,探讨中国大陆期刊在所属学科建设中的作用。[方法/过程]从Web of Science平台上的JCR和InciteTM数据库中下载2010-2014年中国大陆...[目的/意义]通过InciteTM数据库中学科规范化的引文影响系数指标研究中国大陆期刊对各一级学科的影响力,探讨中国大陆期刊在所属学科建设中的作用。[方法/过程]从Web of Science平台上的JCR和InciteTM数据库中下载2010-2014年中国大陆期刊数据及其对各一级学科的学科规范化引文影响系数以及全球和中国大陆各一级学科基准。同时以SPSS20.0进行相关的统计分析。[结果/结论]期刊对所属一级学科的影响力得到评价。各一级学科被收录期刊种数的多寡并不是提高期刊对所属学科影响力的主要因素。被JCR和InciteTM收载的中国大陆期刊对所属一级学科的影响力高于全球基准值和大陆基准值的分别有19种和22种,涵盖两个以上一级学科的分别有7种和5种。其中《科学通报》尤为突出。提出了提升我国科技期刊学科影响力的策略。展开更多
基金financially supported by the Joint Funds of the National Natural Science Foundation of China(Grant No.U23A2047)the General Project of the Natural Science Foundation of Sichuan Province,China(Grant No.2023NSFSC0264).
文摘Rockfall represents a significant geological hazard in mountainous regions,characterized by a sudden and unpredictable feature.The process of dynamic fragmentation and energy conversion in a rockfall event remains complex and not fully understood.This study aims to gain a further understanding of the energy transfer mechanism during rockfall impact and fragmentation by impact tests using a variety of rock-like sphere specimens.The experiments mainly focus on the quantitative correlation between fragmentation degree and influence factors,i.e.impact angle and velocity on steel and granite slabs.The analysis focuses on the energy distribution characteristics,energy dissipation mechanisms,and the energy conversion rate of the fragments during impact and fragmentation.The results show that there is a significant correlation between the energy conversion rate and the fragmentation degree.In normal impact tests,elasto-plastic deformation energy and fracture energy are found to be two primary categories of energy dissipation.The proportion of total kinetic energy after impact is inversely proportional to the initial energy.A comparative analysis between normal and inclined slab impact tests reveals that the impact angle significantly influences the energy conversion rate,which controls the fragmentation degree as well.In addition,the fragmentation degree is inversely proportional to the restitution coefficient.These findings contribute to a better understanding of the energy conversion mechanism during rockfall impact and fragmentation,providing valuable insight for the development of effective strategies to mitigate such rockfall hazards.
基金supported by the Innovation Team Fund of the National Natural Science Foundation of China(11121202)
文摘This letter presents a theoretical model of the normal （head-on） collisions between two soft spheres for predicting the experimental characteristic of the coefficient of restitution dependent on impact velocity. After the contact force law between the contacted spheres during a collision is phenomenologically formulated in terms of the compression or overlap displacement under considera- tion of an elastic-plastic loading and a plastic unloading subprocesses, the coefficient of restitution is gained by the dynamic equation of the contact process once an initial impact velocity is input. It is found that the theoretical predictions of the coefficient of restitution varying with the impact velocity are well in agreement with the existing experimental characteristics which are fitted by the explicit formula.
文摘This study was carried out to investigate the effect of heat treatment (Normalizing and Hardening) on the mechanical properties of springs. The springs were made from mild steel rod having a diameter of 6 mm, a total of 15 springs were made. The springs were then subjected to various heat treatment processes which included;normalizing, hardening and tempering. The heat treated springs were then subjected to various test in other to determine their mechanical properties, these included;impact toughness test, hardness test and tension test. The normalized spring had more strength, was harder and was much tougher than both the annealed and as received springs. The water quenched springs were the hardest of all the heat treated springs, were very brittle and had the lowest percentage elongation. Their strength was also lower than that of the normalized and as received springs. The water quenched and tempered springs had better mechanical properties required for spring making, they had the optimum combination of hardness, strength and toughness when compared with the other heat treated springs.
文摘[目的/意义]通过InciteTM数据库中学科规范化的引文影响系数指标研究中国大陆期刊对各一级学科的影响力,探讨中国大陆期刊在所属学科建设中的作用。[方法/过程]从Web of Science平台上的JCR和InciteTM数据库中下载2010-2014年中国大陆期刊数据及其对各一级学科的学科规范化引文影响系数以及全球和中国大陆各一级学科基准。同时以SPSS20.0进行相关的统计分析。[结果/结论]期刊对所属一级学科的影响力得到评价。各一级学科被收录期刊种数的多寡并不是提高期刊对所属学科影响力的主要因素。被JCR和InciteTM收载的中国大陆期刊对所属一级学科的影响力高于全球基准值和大陆基准值的分别有19种和22种,涵盖两个以上一级学科的分别有7种和5种。其中《科学通报》尤为突出。提出了提升我国科技期刊学科影响力的策略。
