Penetration analysis for geo-material based on unified strength criterion

A unified strength criterion is applied for penetration analysis of geo-materials. Based on the cylindrical cavity-expansion theory the relation between the radial traction on the cavity surface and the impact velocity of a rigid projectile is derived. The finial penetration depth of the projectile is analytically obtained and the effect of strength criterion on the penetration depth is investigated. By comparing with existing test results, it is found that the proposed penetration model is effective in the analysis of a rigid projectile penetrating into a semi-infinite geo-material target.     

Fluctuation analysis of discipline development based on impact factor

Summary  Based on the impact factors of the journals recorded by JCR from 1998 to 2003, this paper established the fluctuation model for discipline development. According to the Fluctuation Strength Coefficient, then we gave analysis and evaluation of developing trends of the disciplines in recent years.     

Numerical analysis of the cutting interaction between indenters acting on disordered materials

In this paper, an attempt is made to find some general relations for the microcutting process in brittle or quasi-brittle materials, under different hypotheses of microscopic failure behavior. Fracture beneath the indenters and sudden chip formation are the main dissipation mechanisms taken into consideration. Fracture patterns in more homogeneous brittle solids are obtained by the Finite Element Method in the framework of Linear Elastic Fracture Mechanics (LEFM). On the other hand, the quasi-brittle response due to microstructural heterogeneities is taken into account by Lattice Model simulations. The analysis is not limited to the more common study of a single indenter. When two indenters are acting in parallel, their mutual distance plays an important role. If the indenters are very close, they behave like a unique larger indenter, whereas if the distance is relatively large, their mechanical interaction vanishes. In addition, when the distance is approximately three to four times their dimension, the mechanism of chipping (with formation of secondary chip between the two parallel grooves) can take place, improving the ratio of removed volume to spent energy and then the demolition ability of the two indenters. Some comparisons are proposed between the presented approach and more sophisticated and computationally demanding models from the literature, as well as with experimental data. The analysis should provide useful hints for the optimal design of super-abrasive tools.     

Influence of directionality on strength and impact behaviour of high strength steels

Abstract

The directionality of the strength and impact behaviour of control rolled 110 grade high strength steel has been examined. Tensile specimens tested along the rolling direction were found to give strengths of ～60 MPa lower than when tested transversely in the rolling direction. Charpy V notch impact samples, in contrast, gave lower impact transition temperatures when taken in the rolling direction (35°C lower). The difference in strength between the two directions is believed to be mainly as a result of the strong texture produced on control rolling. The difference in impact behaviour is due to the more severe fissuring on the fracture surface of the longitudinally tested specimens. Fissuring is more marked on the longitudinally tested sample because of the greater grain elongation in that direction, the initial fracture path being along the grain boundaries.     

The impact strength of polycarbonate

Measurements of the Charpy notched impact strength of polydiancarbonate indicate that the polymer can exist in one of two modifications A and B. There is a temperature (below room temperature) above which the A form is unusually tough; the B modification is comparatively brittle at all temperatures. The A form can be converted to the B form by an annealing process which proceeds rapidly above 80°C. We have not been able to determine the precise morphological difference between the A and B forms but most of the data can be explained by making a hypothesis about the yield behaviour of the A form.     

Multiscale modeling of the impact of textile fabrics based on hybrid element analysis

In this work, a multi scale modeling approach has been developed to simulate the impact of woven fabrics using a finite element (FE) analysis. A yarn level of resolution is used in the model. This approach, referred to as the hybrid element analysis (HEA) is based on decreasing the complexity of the finite element model with distance away from the impact zone based on the multiscale nature of the fabric architecture and the physics of the impact event. Solid elements are used to discretize the yarns around the impact region, which transition to shell elements in the surrounding region. A new method for modeling the shell yarns is incorporated that more accurately represents the contours of the yarn cross section. Impedances have been matched across the solid–shell interface to prevent interfacial reflections of the longitudinal strain wave. The HEA method is validated by first applying it to the FE model of a single yarn for which an analytical solution is known. The HEA method is then applied to a woven fabric model and validated by comparing it against a baseline model consisting of yarns discretized using only solid elements.     

基于转静干涉效应的压气机叶片气动载荷分析

转静叶排的相互作用会使压气机内部流场存在复杂的非定常性。为深入研究压气机叶片的气动载荷特性,以某型航空发动机压气机为研究对象,考虑叶排间的转静干涉效应,利用滑移网格技术对整个叶盘的三维流场展开模拟,求解干涉周期T_b内压气机转子内部的流动规律。同时对叶片气动载荷的非定常特性进行进一步分析,讨论了不同压比、转速对压气机叶片气动载荷的影响。结果表明叶片压力面和吸力面气动载荷波动峰值的主导频率皆为转静干涉频率f₀的倍频,其中一倍频（1×f₀）分量占主导地位。在干涉周期T_b内,叶片表面压力涡发生周期性的迁移与耗散,压力面和吸力面气动载荷的变化呈相反趋势。随着压比的增加,压气机叶片气动载荷逐渐增大,但其脉动幅值和频谱峰值基本不变。转速的升高使得转静干涉的频率增大,增强了压气机叶片气动载荷的非定常特性。研究结果能够应用于叶盘结构的气动优化设计,可为高性能航空发动机压气机的研制提供支持和参考。     

Effect of impact damages on the compressive strength of composite laminates

Abstract

By simplifying the impact damages as a single delamination near the surface with an elliptical boundary, the approximate solution of total strain energy release rates can be derived as a function of delamination major axis, minor axis, external compressive strain, Possion's ratio of parent medium, extensional and bending stiffnesses of sublaminate. A linear relation of residual strength versus strain energy release rate can be constructed by correlating the approximate solution with test data of compressive residual strain (strength) after impact (CSAI), indicating that the dimension between the delamination major and minor axis should be dependent. In addition, the delamination aspect ratio is found to be not only a function of the specimen geometry and the extensional stiffness, but also a function of laminate thickness. The approximate solution provides a method for predicting the post impacted strength of composite laminate for only either thick laminate or thin laminate with low impact energy.     

Modelling the impact of crushing on the strength performance of corrugated fibreboard

This paper presents different ways of modelling the strength of corrugated fibreboard (CFB) subjected to different levels of pre-crushing. The strength performance was measured through four-point bending loading and edge crush test (ECT). The models used in this study were an analytical solution, an equivalent flute model, and detailed flute geometry models that consisted of idealized sine geometry and real geometry. The study found that the bending performance was dependent on the calliper of CFB rather than the flute geometry. All models showed a similar trend in predicting the drop in bending stiffness as the level of pre-crushing increased, albeit with different absolute value. It was found that the real geometry model of the board predicted ECT performance better than the other models. However, at severe pre-crushing levels (>50%), there was a significant drop in the experimental ECT force not predicted by the models. For these cases, there was evidence of delamination of the flute, a failure mechanism that was not included in any of the models. The analytical solution model provides the quickest prediction but could not predict the crushed ECT performance due to not considering the calliper variable in the equation. The equivalent model showed faster solving time compared with both real and idealized geometry models, although these microgeometry models predicted ECT the most accurately.     

Identify asthma genes across three phases based on protein–protein interaction network

Asthma is a common inflammatory disease that is generally caused by genetic mutations or environmental factors. Recently, the emerging of omics data provides an alternative way to understand asthma. In this study, the authors present a new framework to detect asthma disease genes based on protein–protein interaction network (PPIN) and gene expression. Specifically, they construct PPINs for different stages of asthma, and detect those interactions occurred in the specific stages. By investigating the proteins in these stage‐specific interactions, they find they are more likely related to asthma, and the functional enrichment analysis indicate that the pathways enriched in the differential interactions are related to the progress of asthma. Moreover, some proteins in the differential interactions have been previously reported to be related to asthma in the literature, implying the usefulness of the proposed approach.Inspec keywords: genomics, proteins, molecular biophysics, lung, pneumodynamics, diseases, genetics, molecule‐molecule reactions, molecule‐molecule collisionsOther keywords: asthma gene identification, three‐phase gene identification, protein–protein interaction network, common inflammatory disease, genetic mutation‐caused disease, environmental factors, asthma‐associated omics data, asthma disease gene detection, PPIN construction, asthma gene expression, asthma stages, stage‐specific interaction proteins, asthma stage‐specific interactions, asthma‐related interactions, functional enrichment analysis, asthma progress‐related differential interactions, differential interaction proteins     

The interaction between matrix cracks and delaminations during quasi-static impact of composites

This paper discusses the investigation of the impact process for beam-like composite specimens. The research is focused on the initiation of delaminations at matrix cracks and on the interaction of delaminations with matrix cracks. The research is based on experiments and on finite element calculations. This study improves the fundamental understanding of the impact process in composite laminates, and gives clear indications on the relative influence of different material properties (transverse strength, interlaminar fracture toughness) on the damage development during impact.     

Evaluation of interfacial strength between fiber and matrix based on cohesive zone modeling

This paper presents a measurement technique of interfacial strength considering non-rigid bonding on a fiber/matrix interface modeled as a cohesive surface. By focusing on the stress concentration near a fiber crack obtained from a single-fiber fragmentation test, the stress contours in matrix observed by photoelasticity can be related to the interfacial strength by defining a characteristic length. An equation expressing the relationship between the characteristic length on the stress contour and the interfacial strength was derived, and validated using finite element analysis. The primary advantage of proposed measurement technique is that only a single fiber crack, which usually occurs within elastic deformation of matrix, is required for the evaluation of interfacial strength, whereas saturated fiber fragmentation is necessary in the conventional method. Herein, a sample application was demonstrated using a single carbon fiber and epoxy specimen, and an average interfacial strength of 23.8 MPa was successfully obtained.     

ABS/HGB复合材料断口分形维及其与冲击强度的关系

为了改善填料与基体树脂的相容性,应用硅烷偶联剂对中空玻璃微珠(HGB)进行表面处理,并制备了HGB填充聚丙烯腈-丁二烯-苯乙烯三元共聚物(ABS)复合材料,HGB的体积分数为0～15%.在室温条件下,测量了ABS/HGB复合材料的冲击强度.基于冲击断口的SEM图像,采用像素点覆盖法和投影覆盖法测算了ABS/HGB复合材料的冲击断口表面分形维(Ds),并考察了分形维与复合材料冲击断裂强度(σI)的关系.结果表明,ABS/HGB复合材料的冲击强度与断口表面分形维密切相关:σI随着Ds的增加而提高,两者之间呈指数函数关系.应用像素点覆盖法测算的Ds值为1.62～1.74,而应用投影覆盖法测算的Ds值则为2.51～2.58.     

基于LS-DYNA的移动硬盘跌落冲击耐撞性能分析

移动硬盘独特的机械工作方式和部件结构的复杂性决定其对振动冲击非常敏感。针对移动硬盘复杂的内部结构,遵循质量等效原则,基于ANSYS/LS-DYNA动力学分析软件建立非工作状态下的移动硬盘整体跌落冲击有限元模型,分析并确定移动硬盘跌落冲击耐撞性能评价指标。通过数值仿真,分析传动臂材料、传动臂形状以及跌落角度对移动硬盘耐撞性能的影响,为移动硬盘的耐撞性分析、评估与设计提供理论依据。     

Physical factors affecting the impact strength of polycarbonate

The effects due to internal stress, physical ageing and thickness have been separated. It is shown that each of these variables can cause a change from tough to brittle fracture. A 6 mm laminate assembled from 2 mm sheet has the toughness associated with the thinner material.