基于能量的球压痕硬度的计算方法

采用Oliver-Pharr方法计算压痕硬度容易受到卸载斜率计算偏差的影响。为了提高压痕硬度计算的准确度,减小卸载斜率对压痕硬度的影响,假定最大压入深度下的接触半径与完全卸载后的压痕半径相等,根据Hertz接触理论,基于压痕功与压痕深度的线性关系,建立了压痕硬度与压痕功的显式模型。压痕试验的结果表明,基于能量的压痕硬度计算方法能够有效提高压痕硬度计算的准确度,可以满足工程实际需要。     

Eine elastisch‐plastische Übergangsbedingung für die Tropfenschlagerosion von Gesteinen und Betonen

An elastic‐plastic transition criterion for the erosion of rocks and concrete materials by impinging liquid drops Depending on loading regime and material type, mineralic materials behave either elastic or elastic‐plastic if eroded by impinging water drops. A simple transition number that combines fracture toughness and compressive strength (respectively Vickers hardness), can be used to distinguish between both modes. Conventionally ‘hard’ materials, namely granite and feldspars, own low transition numbers (high hardness values) and respond elastic. Conventionally ‘soft’ materials, namely limestone, cement mortar and schist, are characterised by high transition numbers (low hardness values) and show an elastic‐plastic response.     

Orientation dependence of fracture toughness measured by indentation methods and its relation to surface energy in single crystal silicon

Fracture toughness of silicon crystals has been investigated using indentation methods, and their surface energies have been calculated by molecular dynamics (MD). In order to determine the most preferential fracture plane at room temperature among the crystallographic planes containing the 〈001〉, 〈110〉 and 〈111〉 directions, a conical indenter was forced into (001), (110) and (111) silicon wafers at room temperature. Dominant {110}, {111} and {110} cracks were introduced from the indents on (001), (011) and (111) wafers, respectively. Fracture occurs most easily along {110}, {111} and {110} planes among the crystallographic planes containing the 〈001〉, 〈011〉 and 〈111〉 directions, respectively. A series of surface energies of those planes were calculated by MD to confirm the orientation dependence of fracture toughness. The surface energy of the {110} plane is the minimum of 1.50 Jm⁻² among planes containing the 〈001〉 and 〈111〉 directions, respectively, and that of the {111} plane is the minimum of 1.19 Jm⁻² among the planes containing the 〈011〉 direction. Fracture toughness of those planes was also derived from the calculated surface energies. It was shown that the K _IC value of the {110} crack plane was the minimum among those for the planes containing the 〈001〉 and 〈111〉 directions, respectively, and that K _IC value of the {111} crack plane was the minimum among those for the planes containing the 〈011〉 direction. These results are in good agreement with that obtained conical indentation.     

Eine Übergangsbedingung beim Strahlverschleiß von Gesteinen und Betonen

A transition criterion for the erosion of rocks and concrete materials Depending on loading regime and material type, mineralic materials behave either elastic or elastic‐plastic if eroded by solid particles. A simple transition number, X, that combines fracture toughness and compressive strength, can be used to distinguish between both modes. Conventionally ‘hard’ materials, namely granite and feldspars, own low X‐values and respond elastic. Conventionally ‘soft’ material, namely limestone, mortar and schist, are characterised by high X‐values and show an elastic‐plastic response.     

Analytical Modeling to Predict the Strain Energy of Circular GLARE Fiber-Metal Laminates Under Lateral Indentation

This article deals with the strain energy calculation of thin circular clamped Glass Reinforced （GLARE） fiber-metal laminates subjected to static indentation by a lateral hemispherical indentor. Using one-, two- and three-parameter Ritz approximations, analytical equations of the strain energy as a function of the central plate deflection are derived. Previously published analytical formulas, concerning the load-indentation response of circular GLARE plates, are used in order to determine the Ritz parameters and the first failure load and deflection due to tensile fracture of glass-epoxy layers. In this study, the membrane and bending strain energy components of aluminum and prepreg layers are determined. Also, the elastic and plastic strain energy absorbed during the indentation loading are calculated. The derived formulas are applied successfully for GLARE 2-2/1-0.3, GLARE 3-3/2-0.4 and GLARE 31 （special lay-up） circular plates subjected to lateral indentation. The strain energy results converge satisfactorily in all examined cases. The predicted strain energy-indentation response is compared with published experimental data and a good agreement is found. No other solution of this problem is known to the authors.     

Plasma-surface interaction in ITER

The decreasing availability of energy and the concern about climate change necessitate the development of novel sustainable energy sources. Fusion energy is such a source. The ultimate potential of fusion energy is very high and badly needed. A major step forward in the development of fusion energy is the decision to construct the experimental test reactor ITER.ITER will stimulate research in many areas of science. This article discusses research opportunities in the context of plasma-surface interaction. The fusion plasma with a typical temperature of 10 keV has to be brought into contact with a physical wall in order to remove the helium produced and drain the excess energy in the fusion plasma. The fusion plasma is far too hot to be brought into direct contact with a physical wall. It would degrade the wall and the debris from the wall would extinguish the plasma. Therefore, schemes are developed to cool down the plasma. The resulting plasma-surface interaction concerned in ITER is facing several challenges including surface erosion, material redeposition and tritium retention. In this article we introduce how plasma-surface interaction relevant for ITER can be studied in a smaller scale experiment: Magnum-PSI.     

On the parameters of performance of combined refrigeration and power plants

Combined Refrigeration and Power (CRP) plants generate power and refrigerate a thermal load simultaneously from the same fuel. The overall efficiency is a parameter based on the first law generally used to quantify the fuel saving, in the sense that a plant that has greater overall efficiency saves more fuel than others to generate the same useful energy. However, the literature shows that the overall efficiency and other parameters of performance are defined in several different ways. This heterogeneity is not desirable when considering a coherent and universally accepted parameter of performance based on the first law. In this work, some parameters found in the literature are critically analyzed in order to indicate the most proper one. The indicated parameter is then formally analyzed in order to verify its mathematical consistency. The primary energy rate is considered the most well-suited parameter based on the first law to characterize the performance of a CRP plant.     

Al2O3颗粒增强共晶成分铝锰基复合材料冲蚀磨损性能研究

通过对Al2O3颗粒增强Al-2.06%Mn复合材料和Al-2.15%Mn合金在不同磨粒粒径、不同冲蚀速度的冲蚀磨损试验,探索了材料的冲蚀失效规律及其微观破坏机制。结果表明,两种材料在7m/s冲蚀速度下的冲蚀磨损失重率是在3.5m/s冲刷速度下的2～3倍;两种材料的冲蚀磨损失重率随着磨粒粒径的增大先增大后减小,磨粒粒径分布在0.053～0.106mm时两种材料的失重率出现极大值,Al2O3颗粒增强Al-2.06%Mn复合材料的抗冲蚀磨损性能优于Al-2.15%Mn合金。     

Experimental Analysis and Modeling of the Crushing of Honeycomb Cores

In the aeronautical field, sandwich structures are widely used for secondary structures like flaps or landing gear doors. The modeling of low velocity/low energy impact, which can lead to a decrease of the structure strength by 50%, remains a designers main problem. Since this type of impact has the same effect as quasi-static indentation, the study focuses on the behavior of honeycomb cores under compression. The crushing phenomenon has been well identified for years but its mechanism is not described explicitly and the model proposed may not satisfy industrial purposes. To understand the crushing mechanism, honeycomb test specimens made of Nomex, aluminum alloy and paper were tested. During the crushing, a CCD camera showed that the cell walls buckled very quickly. The peak load recorded during tests corresponded to the buckling of the common edge of three honeycomb cells. Further tests on corner structures to simulate only one vertical edge of a honeycomb cell show a similar behavior. The different specimens exhibited similar load/displacement curves and the differences observed were only due to the behavior of the different materials. As a conclusion of this phenomenological study, the hypothesis that loads are mainly taken by the vertical edge can be made. So, a honeycomb core subjected to compression can be modeled by a grid of nonlinear springs. A simple analytical model was then developed and validated by tests on Nomex honeycomb core indented by different sized spherical indenters. A good correlation between theory and experiment was found. This result can be used to satisfactorily model using finite elements the indentation on a sandwich structure with a metallic or composite skin and honeycomb core.     

基于HLA的地基动能武器作战仿真研究

在分析地基动能武器作战方式的基础上，提出了仿真的基本思路；对仿真中的主动段方案设计、中段飞行和末段飞行3类关键数学模型进行了建模分析；最后基于HLA对地基动能武器仿真系统进行了设计．     

Inelastic Neutron Scattering of H2 in Xerogel

The properties of molecular hydrogen adsorbed in Britesorb were studied through inelastic neutron scattering. We have measured both the rotational energy levels and the momentum distribution at bilayer and nearly full pore fillings. Splitting of the J=1 rotational energy levels is observed for molecular hydrogen adsorbed on the surface, while the rotational properties of the hydrogen adsorbed after monolayer completion is consistent with behavior in the bulk. Additionally, the measurement of the momentum distribution showed that the mean kinetic energy of the molecules in the bilayer is 88 K±7 K. The kinetic energy measured in the nearly full pore was 81 K±6 K, which is consistent with a simple model in which the behavior of the monolayer is dominated by the interaction with the surface of the pore wall but H₂ adsorbed after monolayer completion is bulk like.