用Hopkinson压杆技术测试材料动态断裂韧性的方法研究

对传统的Hopkinson压杆测试系统进行了改进 ,建立了应力波载荷作用下材料动态断裂韧性的测试方法 .该方法采用 3点弯曲试样进行动态断裂试验 ,应用试验—数值法确定动态应力强度因子的响应曲线 ,进而测试材料动态断裂韧性 .40Cr材料的试验结果表明 ,本文设计的测试装置是有效的 ,建立的测试方法是可行的 .

Numerical Simulation and Experiment on Dam Break Problem

In this paper, two novel numerical computation methods are introduced which have been recently developed at Research Institute for Applied Mechanics （ R/AM ）, Kyushu University, for strongly nonlinear wave-body interaction problems, such as ship motions in rough seas and resulting green-water impact on deck. The first method is the CIP-based Cartesian grid method, in which the free surface flow is treated as a multi-phase flow which is solved using a Cartesian grid. The second method is the MPS method, which is a so-called particle method and hence no grid is used. The features and calculation procedures of these numerical methods are described. One validation computation against a newly conducted experiment on a dam break problem, which is also described in this paper, is presented.

Influence of a Deflector or a Wall on Savonius Rotor Efficiency

The Savonius rotor is a vertical axis-wind machine composed of two half cylindrical blades presenting a central gap. It is a slow velocity machine compared with horizontal wind machines. Its efficiency is about twenty per cent. In this work experimental tests are presented using two kind of deflectors placed in front of the resistive blade. Such disposition allows to hide the resistant blade and to guide the flow toward the motrice blade. Two deflectors have been used： a short one and a long one. The results obtained in wind tunnel have shown that the long deflector is the more efficient, essentially for high values of the tip speed ratio. One has been interested, using a numerical approach, in the study of the influence of a wall on the aerodynamical field near the rotor.

Birkhoffian Symplectic Scheme for a Quantum System

In this paper, a classical system of ordinary differential equations is built to describe a kind of n-dimensional quantum systems. The absorption spectrum and the density of the states for the system are defined from the points of quantum view and classical view. From the Birkhoffian form of the equations, a Birkhoffian symplectic scheme is derived for solving n-dimensional equations by using the generating function method. Besides the Birkhoffian structure- preserving, the new scheme is proven to preserve the discrete local energy conservation law of the system with zero vector f . Some numerical experiments for a 3-dimensional example show that the new scheme can simulate the general Birkhoffian system better than the implicit midpoint scheme, which is well known to be symplectic scheme for Hamiltonian system.

Simulation Analysis of a New Type of Bionic Digging Shovel Based on DEM

The performance of a digging shovel mainly depends on the style of the shovel, while the conventional experiment methods always suffer from the problems of high lost and long period. Aiming at these problems and the characteristic that soil is composed of countless small particles, dynamic simulation analysis was performed on the resistance to a bionic digging shovel and crushing rate of the soil during the normal working process of the bionic digging shovel by EDEM through numerical simulation, calculation and comparison. The results showed that compared with the ordinary shovel, the average drag-reducing rate in the X direction was 10.41%, and the average drag-reducing rate in the Y direction was 16.28%, and the soil crushing rate was improved by 2.67%. Therefore, the bionic digging shovel has certain superiority and extension value in structure and performance. Moreover, this analysis case fully demonstrates the unique advantage of DEM method and its generalizability, and provides certain reference for similar studies.

Field experiment on coalmine heat disaster governance using cold source from surface water

Regarding the lack of cold source for underground cooling systems from either mine inflow or return air, field experiments were taken in a high temperature deep coal mine with abundant cold source from surface water. Taking Sanhejian coal mine as an example, this paper introduced the technology scheme of heat disaster governance using surface water cold source. The paper presents the basics of this field experiment at the beginning, following by the design and site layout of the cooling system including the analysis and calculation of cold source. Numerical calculation method is also applied based on the operation parameters to simulate the influence to the surface river ecosystem. The results suggest that the temperature of surface water shall be lower than 34 ℃ after heat exchange, and when more cooling capacities are needed in the future, increasing the water flow is more favorable than increasing the cooling range of water, which is better for the ecological environment protection,

Second-order schemes for solving decoupled forward backward stochastic differential equations

In this paper,by using trapezoidal rule and the integration-by-parts formula of Malliavin calculus,we propose three new numerical schemes for solving decoupled forward-backward stochastic differential equations.We theoretically prove that the schemes have second-order convergence rate.To demonstrate the effectiveness and the second-order convergence rate,numerical tests are given.

Vibration test condition for spacecraft lift-off environment

The purpose of the vibration test of spacecrafts is to assess their adaptability to low-frequency vibration environment during lift-off.This paper gives the simulation of the satellite ground vibration test(GVT) and the state of the satellite along with rocket during lift-off.The simulation results of these two states are compared on condition that the lateral vibration of satellite/launching vehicle(S/LV) interface is the same.It is shown that the dynamic responses of satellite vertex are totally different.This is because there is angular motion of S/LV interface during lift-off,but in the GVT,the angular motion is restrained.By means of numerical simulation of the lift-off state,the angular motion related to the translation motion of S/LV interface can be determined.Then,using this angular motion as supplementary condition to simulate the vibration test,the calculated dynamic responses of satellite vertex are identical with the lift-off state.It demonstrates that supplementing angular motion condition is an effective method to improve spacecraft ground vibration test more identically with the real lift-off environment.Furthermore,it is useful for the application of the multi-degree-of-freedom shaking table,and provides the basis for test condition requirement.

A Reduced Basis Approach for Some Weakly Stochastic Multiscale Problems

In this paper,a multiscale problem arising in material science is considered.The problem involves a random coefficient which is assumed to be a perturbation of a deterministic coefficient,in a sense made precisely in the body of the text.The homogenized limit is then computed by using a perturbation approach.This computation requires repeatedly solving a corrector-like equation for various configurations of the material.For this purpose,the reduced basis approach is employed and adapted to the specific context.The authors perform numerical tests that demonstrate the efficiency of the approach.