An experiment model, scaled 1: 1, designed for studying a blasting method to clear away soot in a soot-delivery pipe in coal-burning power plant is described. By mixing RDX and Nitramon on a particular scale and stick...An experiment model, scaled 1: 1, designed for studying a blasting method to clear away soot in a soot-delivery pipe in coal-burning power plant is described. By mixing RDX and Nitramon on a particular scale and sticking the explosive cartridge on the outwall surface of the pipe, the experimental result makes clear that the controlled blasting method can get rid of the soot effectively. Under the action of the blasting compression wave and reflectance tension wave,the soot is destroyed effectively in the region of - 60° ~60° around the bIasting site, that creates a condition for the second blasting in the surplus soot.展开更多
Strain rate effects on the stress-strain behavior of sand were investigated by performing special plane strain and triaxial compression tests on saturated and air-dried sand specimens. In these tests, the loading stra...Strain rate effects on the stress-strain behavior of sand were investigated by performing special plane strain and triaxial compression tests on saturated and air-dried sand specimens. In these tests, the loading strain rate was changed many times by a factor of up to 1 000 during otherwise monotonous loading at a constant axial strain rate. Test results show that the stress jump upon a stepwise change in the strain rate decays with an increase in the irreversible strain when monotonous loading continues at the changed strain rate and the amount of stress jump is essentially proportional to the instantaneous stress. Based on the amount of these stress jumps, a parameter fl called the rate-sensitivity coefficient is introduced to represent the quantity of the observed viscous properties of sand, which equals 0.021 3 and 0.024 2 respectively for Hostun and Toyoura sands. Further analyses on the results indicate that the effect of the presence of pore water is deemed to be negligible with sand and the fl value is rather independent of loading method, wet condition and confining pressure.展开更多
Transient effects of stress-strain fields in the vicinity of a stationary crack tip under high rate loads are discussed.Exact analytical solutions to near tip stresses are compared to fields prescribed by leading term...Transient effects of stress-strain fields in the vicinity of a stationary crack tip under high rate loads are discussed.Exact analytical solutions to near tip stresses are compared to fields prescribed by leading terms(one or several) of Williams asymptotic expansion.Influence of load application mode,time(or,which is the same,distance from a crack tip) and Poisson's ratio on this discrepancy is extensively examined.Some effects connected with crack tip propagation speed are also discussed.Significant inconsistencies between real(or received in numerical solutions of state equations-e.g.finite element computations) crack tip fields and stress intensity factor(SIF) singular field observed by numerous researchers are explained.The scope of problems where SIF field can be used for correct prediction of dynamic stress-strain fields in the crack tip region is established.Possibility to correctly approximate fields that are not SIF dominated,accounting additional terms of Williams expansion,is studied.展开更多
文摘An experiment model, scaled 1: 1, designed for studying a blasting method to clear away soot in a soot-delivery pipe in coal-burning power plant is described. By mixing RDX and Nitramon on a particular scale and sticking the explosive cartridge on the outwall surface of the pipe, the experimental result makes clear that the controlled blasting method can get rid of the soot effectively. Under the action of the blasting compression wave and reflectance tension wave,the soot is destroyed effectively in the region of - 60° ~60° around the bIasting site, that creates a condition for the second blasting in the surplus soot.
基金Project(50679056) supported by the National Natural Science Foundation of ChinaProject(06-0378) supported by Program for NewCentury Excellent Talents in University+1 种基金Project(05SG25) supported by the "Dawn" Program of Shanghai Education Commission, ChinaProject(B308) supported by the Shanghai Leading Academic Discipline, China
文摘Strain rate effects on the stress-strain behavior of sand were investigated by performing special plane strain and triaxial compression tests on saturated and air-dried sand specimens. In these tests, the loading strain rate was changed many times by a factor of up to 1 000 during otherwise monotonous loading at a constant axial strain rate. Test results show that the stress jump upon a stepwise change in the strain rate decays with an increase in the irreversible strain when monotonous loading continues at the changed strain rate and the amount of stress jump is essentially proportional to the instantaneous stress. Based on the amount of these stress jumps, a parameter fl called the rate-sensitivity coefficient is introduced to represent the quantity of the observed viscous properties of sand, which equals 0.021 3 and 0.024 2 respectively for Hostun and Toyoura sands. Further analyses on the results indicate that the effect of the presence of pore water is deemed to be negligible with sand and the fl value is rather independent of loading method, wet condition and confining pressure.
基金supported by RFBR research grants, Russian Federal programs and academic programs of the Russian Academy of Sciences
文摘Transient effects of stress-strain fields in the vicinity of a stationary crack tip under high rate loads are discussed.Exact analytical solutions to near tip stresses are compared to fields prescribed by leading terms(one or several) of Williams asymptotic expansion.Influence of load application mode,time(or,which is the same,distance from a crack tip) and Poisson's ratio on this discrepancy is extensively examined.Some effects connected with crack tip propagation speed are also discussed.Significant inconsistencies between real(or received in numerical solutions of state equations-e.g.finite element computations) crack tip fields and stress intensity factor(SIF) singular field observed by numerous researchers are explained.The scope of problems where SIF field can be used for correct prediction of dynamic stress-strain fields in the crack tip region is established.Possibility to correctly approximate fields that are not SIF dominated,accounting additional terms of Williams expansion,is studied.
