Influence of strain rate on the nature of failure under prolonged static and cyclical loads. 2. Examples of calculation

Based on a physicomechanical model of intercrystallite failure in materials, such as presented in the previous communication, we have proposed a computational algorithm for the endurance of polycrystalline material under cyclical load. We have provided examples for the calculation of the cyclical strength in austenitic steel under various strain rates. Comparison of the theoretical results against the experimental data demonstrated the possibility of using the model developed here to describe the quantitative relationships governing intercrystallite failure of the material over a broad range of load regimes.Translated from Problemy Prochnosti, No. 8, pp. 42–47, August, 1991.     

A robust kinematic hardening rule for cyclic plasticity with ratchetting effects

Summary A robust kinematic hardening rule is proposed which appropriately blends the deviatoric stress rate rule and the Tseng-Lee rule in order to satisfy both the experimental observations made by Phillips et al. [1]–[5] and the nesting of the yield surface to the limit surface. The work presented in Part I is confined to the theoretical formulation of kinematic hardening rule with limited correlation to experimental results. A more general expression for the plastic modulus is proposed. The expressions proposed by McDowell and by Dafalias can be obtained as a special case of the proposed expression. An additional parameter is introduced that reflects the dependence of the plastic modulus on the angle between the deviatoric stress rate tensor and the direction of the limit backstress relative to the yield backstress.     

Control of properties of PZT ceramics during liquid-phase sintering

A PZT ceramic modified by 0.4Pb-(1–x)(B₂O₃)–x(GeO₂) glass, and glass-ceramics modified by V₂O₅, have been obtained. The influence of the chemical composition of the glasses on the mechanical strength and dielectric parameters of these ceramics is investigated. The mechanical and electrical parameters of PZT ceramics are considerably improved by small additions of glass ( 1 mass %) of suitable composition. During heat treatment, the mobility of the domain walls may be changed as a result of the interaction of smelt glass with the surface layer of the crystallites (resulting from a change of V _Pb ^t" vacancy concentration in grains and decreased mechanical tension on the grain boundaries). By introducing the glass, we can decrease the porosity of the ceramics and thus decrease the attenuation of surface acoustic waves in piezoelectric filters. The origin of the liquid phase during sintering of the PZT glass-ceramics prevents PbO evaporation. This determines the preservation of the solution's stoichiometry. The glass addition leads to a decrease in the sintering temperature of PZT, which simplifies the technological process. The glass ceramics are obtained by common ceramic technology which is used for commercial piezoceramic production. The main technological problem is choosing the chemical composition and concentration of the glass and thermal process parameters.     

颗粒随机填充混合物介电性能仿真的新方法

仿真技术在混合物料的介电性能研究中具有重要价值.针对当前研究中面临的仿真模型理想化、多组分物料模拟分析不足和物料加工过程中的动态模拟分析缺失等问题,采用COMSOL App开发器编制基于蒙托卡罗法的颗粒随机生成、投放程序,构建了基质颗粒的空间位置、体积在基体中随机分布的立方体多胞有限元模型,利用能量法和有限元法,分析了颗粒填充混合物的等效介电特性.通过对比研究验证模型的有效性,与传统模型相比,上述模型更符合颗粒在混合物中的真实状态,能获得与实测值更加接近的数值结果.研究可为三维情形下多组分混合物的介电性能模拟分析提供一个参考方法,为变温变频条件下混合物的传热传质过程模拟分析提供借鉴.     

Evaluation of the mechanical characteristics of soils from static-penetration data

Conclusions 1. The specific resistance of soil not only beneath the cone of the penetrometer but also against the friction couple should be used to define the prediction of the strength and deformation characteristics of silty-clayey soils more precisely from static-penetration data, and the type of clayey soils should also be considered for the strength characteristics.2. For penetrometers equipped with radiation-logging apparatus, it is possible to evaluate mechanical characteristics of soils under field conditions, using the soil's density in addition to the penetration parameters q and f.3. In developing regional statistical relationships, it should be remembered that the extent to which q and f influence . c, and E is determined largely by what types of soil the statistical sample represents and in what range the physical indicators of its conditions vary.4. To define the recommendations of Construction Rule and Regulation 1.02.07-87 more precisely, it is expedient to use resultant correlation relationships (6)–(8) to evaluate , c, and E from static-penetration data for the genetic groups of quartenary deposits investigated.Translated from Osnovaniya, Fundamenty i Mekhanika Grungov, No. 4, pp. 21–24, July–August, 1990.     

Extended input-output models: progress and potential

"This article presents a critical survey of research on extended input-output models, emphasizing recent developments in demographic-economic and socio-economic analysis. Basic principles of model design and construction are reviewed, by reference to a representative selection of extended models. Two research themes--labor market analysis and income distribution--are pursued in greater detail as examples of the directions of current work. A comparison is made between extended models and social accounting matrices."     

情绪智力对高校教师的多层次影响实证研究

研究采用多层次数据统计软件,探讨情绪智力对高校教师职业成长、教学方式与教学质量的影响关系。采用跨层次分析468份问卷后发现:教师情绪智力对学生课程认同与教师认同具有正向影响,这种影响是通过教师情绪智力改变教师职业成长与教学方式的机制加以传导。通过上述实证检验,阐述了当前教师情绪智力对高校教学质量影响的重要作用,建议高校在教师选拔与培养的过程中不仅需要关注其科研水平的提升,也应当关注其情绪智力的培养,从而提高整体教学质量。     

基于机械臂运动的组合航天器惯性参数在轨辨识

随着空间技术发展,交会对接任务越来越多,服务航天器与目标航天器对接形成组合航天器后惯性参数会发生明显变化。因此,提出一种基于机械臂运动的组合航天器惯性参数在轨辨识方法。该方法可以分为2步:第一步辨识组合航天器的质量和质心;第二步辨识组合航天器的惯性张量。该方法优点是实现了质量、质心与惯性张量等辨识参数的相互解耦,不需要消耗航天器上宝贵的喷气燃料,仅需要测量航天器的速度,而不是加速度和力。仿真结果验证了方法的有效性。     

注气井井筒结垢预测研究

在油田开发过程中,油、气、水和泥浆在地层或管道中流动,当达到一定条件时,油垢、水垢或泥垢便会产生。在实际生产过程中,油垢和泥垢通常伴随着水垢而生成,所以对水垢结垢趋势的预测研究显得至关重要。介绍了Oddo-Tomos饱和指数法的理论预测模型,以及在生产过程中利用Oddo-Tomos饱和指数法预测油田结垢趋势的方法,阐述并分析了油田结垢对油田开采的影响。研究结果可为下一步的生产作业提供理论依据。     

注气井井筒结垢预测研究

在油田开发过程中,油、气、水和泥浆在地层或管道中流动,当达到一定条件时,油垢、水垢或泥垢便会产生。在实际生产过程中,油垢和泥垢通常伴随着水垢而生成,所以对水垢结垢趋势的预测研究显得至关重要。介绍了Oddo-Tomos饱和指数法的理论预测模型,以及在生产过程中利用Oddo-Tomos饱和指数法预测油田结垢趋势的方法,阐述并分析了油田结垢对油田开采的影响。研究结果可为下一步的生产作业提供理论依据。