摘要：建立统一本构模型,预测面心立方金属(FCC)超声振动(UV)辅助成形塑性流动行为。该模型基于超声能场下的位错动力学并结合应力叠加机制描述UV软化行为。考虑位错密度、晶粒尺寸和超声能场的相互作用,以位错密度和晶粒尺寸作为内部状态变量建立模型,预测UV辅助成形的残余行为。开展无氧高导热(OFHC)铜UV辅助压缩试验来验证该模型的预测能力。结果表明,OFHC铜在UV下表现出明显的软化行为和残留软化行为,模型预测与实验结果吻合较好,有效反映铜的软化效应和残余效应。

摘要：The vibrations induced by the passage of high-speed trains(HSTs)are considered a crucial issue in the field of environmental and geotechnical *** wave barriers have been investigated to reduce the detrimental effects of HST-induced *** study is focused on the potential implementation of an innovative mitigation technique to alleviate the developed *** particular,the use of expanded polystyrene(EPS)blocks as partial fill material of embankment slopes was *** efficiency of the proposed mitigation technique was numerically *** specifically,a 3 D soil-track model was developed to study the cross-section of a railway track,embankment,and the underlying soil *** passage of the HST,Thalys,was simulated using a moving load method,and the soil response was calculated at several distances from the *** parameters influenced the effectiveness of the examined mitigation ***,to ensure an optimal design,a robust procedure is necessary which considers the impact of these ***,the implementation of EPS blocks on several embankments with different geometry,in terms of height and slope angle,was investigated.

摘要：In this study,2D and 3D soil arching phenomena associated with piled embankments were evaluated by performing a series of discrete numerical analyses using the particle flow code(PFC3D)*** validating the micro-parameters with experimental results,we compared the stress-displacement distribution,force chain evolution,maximum vertical displacement of particles,and deformation characteristics induced by 2D and 3D arching *** analyses were carried out to understand the influence of the fill height,pile clear spacing,friction coefficient,and porosity on soil arching with respect to the stress concentration ratio(SCR)and settlement along the elevation at various *** numerical results indicated that a plane soil arch in a 2D embankment overestimates the degree of load transfer and underestimates the settlement at the crest and within the embankment along the elevation in a 3D embankment.A lower equal settlement plane can be found in a 2D ***,an increase of fill height and friction angle,and a decrease of pile clear spacing and porosity can help to improve the degree of reduction in load transfer and settlement in both 2D and 3D ***,for partially mobilized soil arching in the 3D condition,the increase of fill height reduces the settlement of soils mainly in the portion above the square subsoil area,but has less influence over the portion above the rectangular subsoil area.

摘要：A monitoring scheme must be so designed that several possible mod-els can be efficiently separated in the stage of analysis of deformation *** on the concept of separability developed by Chen and Chrzanowski,a methodology for the design of monitoring schemes has been developed by the *** the method a computer simulation technique is employed,into whichsome rules have been elaborated allowing minimal human *** this pa-per the criterion is first presented and the design technique using the step one up-dating procedure is ***,design of a simulated monitoring networkis made as a demonstrating example.

摘要：Although numerical simulation tools are now very powerful,the development of analytical models is very important for the prediction of the mechanical behaviour of line contact structures for deeply understanding contact problems and engineering *** the line contact structures widely used in the engineering field,few analytical models are available for predicting the mechanical behaviour when the structures deform plastically,as the classic Hertz’s theory would be ***,the present study proposed an elastic-plastic model for line contact structures based on the understanding of the yield mechanism.A mathematical expression describing the global relationship between load history and contact width evolution of line contact structures was *** proposed model was verified through an actual line contact test and a corresponding numerical *** results confirmed that this model can be used to accurately predict the elastic-plastic mechanical behaviour of a line contact structure.

摘要：The safety of astronauts would be severely threatened if the lunar-landing spacecraft were under an emergency during the near moon phase of flight, which was far from the Earth. For the problem of mission abort caused by the main engine (service propulsion system, SPS) failure during lunar orbit insertion, firstly, the family of trajectories resulted from SPS premature shutdown and corresponding abort trajectories were analyzed; then an algorithm that can be applied to the near moon abort trajectories was proposed using patched-conic technique. The characteristics of the abort trajectory, such as energy consumption and return time of flight, were analyzed and presented. Finally, simulation examples were given to demonstrate various cases of near moon SPS failure. The results of the simulation have validated the approach proposed.

摘要：In order to simultaneously measure the initiation toughness of pure mode Ⅰ and mode Ⅱ cracks in one specimen,a large-size double-cracked concave-convex plate(DCCP)specimen configuration was *** tests were implemented in the drop plate impact *** gauges were employed to measure impact loads and crack initiation *** corresponding numerical model was established by using the dynamic finite difference program AUTODYN,and the experimental-numerical method and ABAQUS code were utilized to obtain the initial fracture toughness of the *** experiments and numerical research,we concluded that the DCCP specimen is suitable for measuring the initial fracture toughness of pure mode Ⅰ and mode Ⅱ cracks at the same time;the dynamic initiation toughness increases with the increase of loading rate and the crack initiation time decreases with increasing loading rate;the initiation toughness of mode Ⅱ crack is 0.5 times that of mode Ⅰ crack when subjected to the same loading *** the pre-crack in the vicinity of the bottom of a sample,when its length increases from 20 to 100 mm,the dynamic initiation toughness of the pure mode Ⅰ crack gradually decreases,and the longer the lower crack length is,the easier the crack would initiate,but the dynamic initiation toughness of pure mode Ⅱ crack varies little.

摘要：The adopted 2-D SSD （stopping sight distance） adequacy investigation in current design practice may lead to design deficiencies due to inaccurate calculation of the available sight distance. Although this concern has been identified by many research studies in the past, none of them suggested a comprehensive methodology to simulate from a 3-D perspective concurrently both the cross-section design and the vehicle dynamics in space during emergency braking conditions. The proposed methodology can accurately perform SSD adequacy investigation in any 3-D road environment where the ground, road and roadside elements are inserted by identifying areas of interrupted vision lines between driver and obstacle being less than the required distance necessary to bring the vehicle to a stop condition. The present approach provides flexibility among every road design and/or vehicle dynamic parameter inserted, as well as direct overview regarding design elements that restrict the driver＇s vision and create SSD inadequacies. As a result, precious guidance is provided to the designer for further alignment improvement but mostly an accurate aid to implement geometric design control criteria with respect to both existing as well as new road sections is delivered. The efficiency of the suggested methodology is demonstrated through a case study.

摘要：Nowadays, more and more digitalized spatial data are sold and transmitted on the Internet. Thus, there arises an important issue about copyright protection of the digital data. To solve this problem, this paper has designed and implemented a spatial data watermarking service (SDWS) system which can provide a secure framework for data transaction and transfer via the Internet and protect the rights of both copyright owners and consumers at the same time.

摘要：The structure of global lithosphere is very important to the scientific researches of tectonic movement, geodynamic process, mantle convection, resource exploration, and disaster prevention and reduction. Three-dimensional (3D) spatial modelling and visualization is an effective tool for lithosphere researches. However, both the isoline/profile methods and the Euclidean-based 3D modelling methods cannot meet the requirement of real 3D modeling of global lithosphere, whereas the recently developed global 3D grid methods have some defects on grid design, such as grid shrinkage, overlapping, non-orthogonality, and nonlatitude-longitude consistency. In this paper, Spheroid Degenerated-Octree Grid (SDOG), a non-overlapping, non-shrinking, orthogonal, latitude-longitude consistent grid in the spheroidal manifold space, was chosen as the basic grid for global lithosphere 3D modeling and visualization. The SDOG-based methods of spatial representation and modelling of lithosphere were proposed. A multi-scale model of lithosphere was designed, and the multi-scale modeling and multi-mode visualization were realized at the full advantages of SDOG in multi-hierarchical and multi-resolution and the properties of lithosphere in multi-semantic. It shows that (1) the SDOG-based method has not only overcome the defects of the current global 3D grid, but also reflected the spherical features of lithosphere more realistically and naturally than the traditional methods, providing a novel solution for global modeling, numeric simulating, and data sharing of lithosphere; and (2) more detailed plates division, more precise geo-layer structure, plates boarder and surface concave-convex, and more rich lithosphere properties are revealed as the scale-model moves on.