大理岩声发射Kaiser效应法测量原岩应力试验研究

为研究声发射Kaiser效应法测量原岩应力,进行了现场套孔应力解除试验,得到了试件加载方向的实测应力值,对大理岩进行单轴压缩条件下的2次加载声发射试验并确定Kaiser点.试验结果表明:通过声发射Kaiser效应法测得的地应力与通过套孔应力解除法测得的原岩应力误差小于10 %,原岩应力位于20 %~26 %的峰值强度之间,即岩石压密阶段后期或弹性阶段初期.研究结果可为提高判读Kaiser点的精度和岩石工程实际提供依据.      

地应力场的结构分析在声发射Kaiser效应中的应用

由于地压活动的复杂性及ｋａｉｓｅｒ效应和声发射技术本身存在的问题，Ｋａｉｓｅｒ效应测量原岩应力的方法在现场应力测量方面还有许多重要尚待进行深入地研究和实践，其中与生产联系最密切也是最关键的问题是原岩应力的主方向如何确定的问题。     

龙门山矿区套孔应力解除法测定原岩应力

为优化龙门山矿区开采顺序和巷道设计,原岩应力测量非常必要。文中详细介绍了应用套孔应力解除法测定矿山原岩应力,对龙门山矿区原岩应力进行了实际测定,得到了矿区原岩应力大小、方向等参数及其分布规律,结果显示：矿区原岩应力随深度增加而增大,水平应力为最大主应力,主应力方向与巷道走向基本一致,巷道设计合理。     

基于Kaiser效应红透山铜矿原岩应力测量

红透山铜矿是国内采深最大的金属矿山之一,其深部地压显现形式具有典型性。为了解深部岩体的应力状态及分布特征,应用Kaiser效应的方法进行了原岩应力的测量。岩石试样取自-467～-827水平11个位置,进行单轴压缩声发射实验。结果表明:在深度为720～1 080 m的范围内垂向应力值随埋深变大而持续增加,在量值均高于上覆岩体的自重,与埋深近似于呈线性关系;在-767中段以下应力较高,达42 MPa以上,表明深部存在着较高的应力环境。     

地下矿山原岩应力的测定

本文讨论了某地下矿区原岩应力场的测试。测试方法系采用φ36型孔径变形计在三孔交汇钻孔中进行测定的。测试结果表明:该矿区原岩应力以近水平构造应力为主,实测结果与有限单元法计算结果基本相符,为矿山的地压控制提供了重要依据。     

智能声波监测设备在生产中的应用与研究

岩石的破坏伴随着声发射，通过声发射可以反映岩石的受力状态以及岩石的结构，通过声发射Kaiser效应可以测量地层中的应力，研究岩石的性质。利用声发射仪器对岩石的破坏过程进行监测，收集有用的信息，从而应用于矿山采场顶板安全分级、冒顶预报与地压的综合分析，以及岩体工程稳定性分析和声发射测试等方面。红透山铜矿通过对DYF-2型智能声波监测多用仪在生产实际中的使用，取得了一定的成绩。     

利用磁声发射法对钢铁件微观损伤与残余应力的研究

本文通过４５钢和Ｔ１０钢在不同组织及应力状态下，磁声发射信号的强度，幅值和脉宽分布等特性的研究，表明了磁声发射特性的变化与材料内部应力状态有关。利用磁声发射可以无损地检测钢铁材料服役中出现的微观损伤和残余应力，避免应力，避免在役工件的意外事故发生。     

滥泥坪铜矿三维地应力测量及巷道布置优化研究

随着矿山开采深度的持续增加，深部高地应力作用下矿区的地压灾害发生率逐渐增长。为使矿区能够安全合理地开展生产工作，准确测量区域内的地应力分布情况，并在此基础上进行巷道布置优化研究很有必要。采用套孔应力解除法对滥泥坪深部3个中段进行三维地应力测试，并对三维应力场分布特征进行分析。测量结果表明：滥泥坪矿区应力随深度基本呈线性增长，实测的各中段最大主应力值在28.62~43.10 MPa之间，原岩应力场以水平构造应力为主，总体表现为NNW-SSE向，根据测量结果调整巷道布置方向并建立三维地质模型对巷道稳定性进行分析，研究结果对巷道布置和矿山安全生产具有重要的指导意义。     

喷锚支护对硐室围岩稳定性的影响浅析

矿山地下开采破坏了原岩的应力平衡状态，产生次生应力场，对围岩的稳定性造成影响，根据其应力状态分布，采取相应的喷浆、锚杆或喷锚联合支护，能够很好地保持硐室围岩的稳定性。     

基于声发射概率密度函数固废胶结充填体损伤分析

固废胶结充填体是保障矿山安全回采的关键承载结构,为探究其实际承载损伤破坏过程,在RMT-150C岩石力学测试系统上对不同粗骨料含量的4组胶结充填体试样进行了单轴压缩与循环载荷下的声发射试验。结果表明：循环载荷下,4组试样均具有显著的Kaiser效应,且含块石的3组试样声发射事件数更丰富,峰值应力前达到了纯尾砂试样的152%、225%和300%。同时,利用声发射概率密度与承载应力水平间的关联性,得到了4组不同块石含量胶结充填体的声发射概率密度方程,通过声发射概率密度函数实现了声发射参数量化分析胶结充填体承载损伤过程。对比损伤变量-应力水平曲线可以看出,块石的加入能够有效减缓并抑制前期损伤,当块石含量为20%时,效果最好。     

Ferroelectric/ferroelastic interactions and a polarization switching model

Ferroelectric and ferroelastic switching cause ferroelectric ceramics to depolarize and deform when subjected to excessive electric field or stress. Switching is the source of the classic butterfly shaped strain vs electric field curves and the corresponding electric displacement vs electric field loops [1]. It is also the source of a stress—strain curve with linear elastic behavior at low stress, non-linear switching strain at intermediate stress, and linear elastic behavior at high stress [2, 3]. In this work, ceramic lead lanthanum zirconate titanate (PLZT) is polarized by loading with a strong electric field. The resulting strain and polarization hysteresis loops are recorded. The polarized sample is then loaded with compressive stress parallel to the polarization and the stress vs strain curve is recorded. The experimental results are modeled with a computer simulation of the ceramic microstructure. The polarization and strain for an individual grain are predicted from the imposed electric field and stress through a Preisach hysteresis model. The response of the bulk ceramic to applied loads is predicted by averaging the response of individual grains that are considered to be statistically random in orientation. The observed strain and electric displacement hysteresis loops and the nonlinear stress—strain curve for the polycrystalline ceramic are reproduced by the simulation.     

特高锻模应力场有限元分析

本文运用有限元法对特高锻模应力场进行计算，并对影响锻模应力场的主要因素及其变化规律进行分析、为改进锻模结构，提高锻模寿命提供理论依据。     

Stress Paths in Relation to Deep Excavations

The mechanical behavior of many soils such as stiff clays depends on their current effective-stress states and stress history. For improving design and analysis of soil-structure interaction associated with deep excavations in these soils, it is important to understand effective-stress changes around excavations caused by both horizontal and vertical stress relief. In this paper, total and effective-stress variations adjacent to a diaphragm wall during construction of a 10-m-deep excavation in stiff fissured clay are reported and discussed. Interpreted field stress paths are compared with some relevant laboratory triaxial stress path tests, which simulate the horizontal and vertical stress relief in the field at an appropriate stress level. The interpreted field effective-stress paths in front of the wall are found to be similar to laboratory stress paths determined in undrained extension tests. Field stress paths behind the wall do not correspond particularly well with those from laboratory undrained compression tests, except when the stress state approaches active failure. The conventional undrained assumption does not seem to hold for the soil located immediately behind the wall during a relatively rapid excavation in the stiff clay.     

中间包结构有限元分析

介绍了某钢厂中间包结构存在的问题,简要论述了中间包产生变形和裂纹的机理.利用数值模拟的方法对中间包结构强度和刚度进行有限元分析,通过计算所得的中间包温度场和应力场,显示中间包结构高应力区和强度的薄弱位置,提出改进方案.此外还改变中间包的耐火材料层的厚度和综合导热系数,分析这些因素对中间包温度场和应力场的影响,为中间包结构的优化提供理论支持.     

A comparison of the stresses developed in tension, shear peel, and torsion strength testing of direct bonded orthodontic brackets

Strength testing of direct bonded orthodontic bracket systems is commonly performed with tension, shear peel, or torsion loads. In general, the results of these tests are reported as an average stress that is computed by dividing the experimentally measured force at failure by the area of the bracket base. The average value, obtained in this manner, implies an evenly distributed stress field. In this project, finite element model (FEM) calculations were used to determine the more realistic stress distributions generated within the cement. The results indicate that the three loading modes produce very different non-uniform stress field patterns. Furthermore, the calculated stress peaks and the stress component proportions depend on the loading method. It was therefore concluded that the manner of loading affects the strength measurements and that the average stress does not adequately characterize bond strength.     

<Emphasis Type="Italic">In situ</Emphasis> Weak Magnetic-Assisted Thermal Stress Field Reduction Effect in Laser Welding

For decades, post-welding magnetic treatment has been used to reduce residual stress of welds by improving the crystal structure of solid-state welds. In this paper, we propose a new magnetic treatment method, which can reduce the time-dependent thermal stress field in situ and reduce the final residual stress of welds by simply exerting an assisted weak magnetic field perpendicular to the welding direction and workpiece during laser welding. A new finite-element model is developed to understand the thermal–mechanical physical process of the magnetic-assisted laser welding. For the widely used 304 austenite stainless steel, we theoretically observed that this method can reduce around 10 pct of the time-dependent thermal stress field, and finally reduce approximately 20 MPa of residual stress near the heat-affected zone with a 415-mT magnetic field for typical welding process parameters. A new mechanism based on magneto-fluid dynamics is proposed to explain the theoretical predications by combining high-speed imaging experiments of the transient laser welding process. The developed method is very simple but surprisingly effective, which opens new avenues for thermal stress reduction in laser welding of metals, particularly heat-sensitive metallic materials.     

地应力场与地质构造运动关系研究

初始地应力是地下工程围岩稳定与支护结构设计的一个基本参数。文中详细介绍了地应力计算原理 ,并根据矿区实测地应力资料 ,分析了区域初始地应力场与地质构造运动的关系。为进一步研究本地区地质构造运动的演化规律提供了依据。     

An analysis of residual stress fields caused by shot peening

In this article, the compressive residual stress field (CRSF) introduced by shot peening was studied comprehensively. The 40Cr steel, which is widely applied in industry materials, was used and shot peened under different conditions. The experimental results show that the maximum of compressive residual stress field for a given material is almost the same even under different shot peening techniques and the surface residual stress values are dependent on both the mechanical properties of target materials and peening parameters.     

Cutting stress off at the pass: Reducing vigilance and responsiveness to social threat by manipulating attention.

Personality processes relating to social perception have been shown to play a significant role in the experience of stress. In 5 studies, the authors demonstrate that early stage attentional processes influence the perception of social threat and modify the human stress response. The authors first show that cortisol release in response to a stressful situation correlates with selective attention toward social threat. Second, the authors show in 2 laboratory studies that this attentional pattern, most evident among individuals with low self-esteem, can be modified with a repetitive training task. Next, in a field study, students trained to modify their attentional pattern to reduce vigilance for social threat showed lower self-reported stress related to their final exam. In a final field study with telemarketers, the attentional training task led to increased self-esteem, decreased cortisol and perceived stress responses, higher confidence, and greater work performance. Taken together, these results demonstrate the impact of antecedent-focused strategies on the late-stage consequences of social stress. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

FEM Analysis of Physical Field in Level Rolling Process of Inversion Casting by ANSYS Program

Ininversioncastingprocessmothersheetisledthroughameltwhichthencrystallizesonthesurfaceofthestrip.Throughacoupleoflevelrollersabovethemeltthecastingstripisroughlyrolled,thefigureisshownintheReference[1].Levelrollingisveryimportantintheprocess.　　ThevaluesimulationtechnologyonthebasisofFEMhasbeenusedgraduallyinthefieldofmetalplasticforminginrecent20years.Thetheoriesareadoptedfromsmallelastic-plasticdeformationFEMtobigelastic-(viscidity)plasticdeformationFEM,andtheanalysistechnologyisbecomin…