改性聚丙烯纤维微膨胀混凝土在超长结构工程的研究与应用

目前,在结构工程中开裂已经是相当普遍和严重的问题,而大部分的裂缝发生在早期,且对混凝土耐久性影响深远.应用改性聚丙烯纤维和膨胀剂双掺技术,通过砂浆、混凝土的平板试验,考察聚丙烯纤维微膨胀混凝土对控制混凝土早期变形裂缝的效果,进一步通过对其自由收缩率、限制膨胀率、力学性能等技术指标的测试,来分析控制早期裂缝的原因,以此确定北京出版发行物流中心项目超长结构墙体的最佳配合比及工艺参数,并且通过实际验证,证明是一种有效控制早期裂缝的方法之一,并且对控制超长结构裂缝起到一点借鉴作用.     

Mathematical Models of Block Media in Problems of Geomechanics. Part II: Consideration of the Transverse Block Deformations

The mathematical models are constructed for the elastic and elastoplastic deformation of a block rock mass. Of principal importance is to determine the mechanisms of block deformation. The solutions of problems on mine working in block massif and on rigid punch indentation are considered.     

热轧带肋钢筋的矫直工艺研究

提出了一种新的热轧带肋钢筋的矫直方式，使得矫直后的钢筋表面无划伤，强度与塑性均有提高，消除了矫直后的钢筋屈服点不明显现象。并对经过不同矫直工艺后的热轧带肋钢筋的金相组织分布、力学性能进行了研究。     

铁基形状记忆合金0Cr9Ni6Mn16Si5的生产工艺

研究了0Cr9Ni6Mnl6Si5形状记亿合金的生产工艺和性能。研究结果表明，0Cr9Ni6Mnl6Si5合金可以采用EF VOD VHD工艺冶炼。该合金具有强的热敏感性和高温变形抗力，高温可加工热塑性温度区间比较窄，温度超过l100℃时塑性直线下降。铸锭的开锻温度为l080℃，终锻温度为900℃；锻造管坯只有采用挤压方法实施管材成形。挤压成形的毛坯管可以采用冷轧与冷拔相结合的方法进一步加工成薄壁管。     

Nonlocal damage modelling using the element-free Galerkin method in the frame of finite strains

Prediction of size effects has been a challenging problem since some experiments found the size effect in material damage. Both material model and numerical algorithm have to be improved to consider the complex damage process. In the present paper we implement element-free Galerkin (EFG) method for a strain-gradient based nonlocal damage model and use it to analyze ductile material damage process. The EFG algorithm overcomes some drawbacks of the FEM in convergence of numerical iteration due to large deformations as well as evaluation of the higher-order gradients of the plastic strain. The numerical benchmarks show that the EFG method for the nonlocal damage model provides more stable numerical results. The size effect in notched specimens can be predicted in the computations. Both ductile fracture in tensile specimens as well as their size effects are investigated and the computational results agree very well with experiments.     

Measurements of the microhardness and compression testing of ferroelectric lead nitrate phosphate single crystals

Ferroelectric crystals of lead nitrate phosphate (LNP) have been grown employing the controlled reaction between lead nitrate and orthophosphoric acid. The microhardness of LNP crystals has been determined. The effect of annealing and quenching on the mechanical properties of these crystals has been studied.     

稀土对6063铝合金热塑性的影响

采用热扭转试验、扫描电镜和透射电镜观察,研究了混合轻稀土对6063铝合金热塑性的影响规律,探讨了稀土的影响机制。结果表明,在480—560℃的温度范围内,混合轻稀土的加入能显著提高6063铝合金的热塑性;加稀土的 RE6063合金不经均匀化退火,其热塑性就与已均匀化处理的6063铝合金相当。通过组织观察和分析,讨论了稀土提高热塑性和改善铸态、均匀化态组织之间的关系。     

带圆角弯曲板应力集中和极限载荷的分析

根据折线形截面假设,提出了一种计算带圆角平板受弯曲时的应力集中系数和弹塑性极限载荷的简单而有效的方法。文中详细讨论了圆角的半径(ρ)和圆角的深度系数(t)对局部应力的影响;比较了深圆角和浅圆角两种情况,并推导出弹塑性交界面与弹塑性极限载荷及局部应力的关系。文中算例与光弹性实验和有限元结果进行比较后表明,该方法简单、有效,适用于工程实际问题。     

Large strain finite element analysis of a local second gradient model: application to localization

The original article to which this Erratum refers was published in the International Journal for Numerical Methods in Engineering 2002; 54 :365–398.     

Non‐uniform plastic deformation of micron scale objects

Significant increases in apparent flow strength are observed when non‐uniform plastic deformation of metals occurs at the scale ranging from roughly one to ten microns. Several basic plane strain problems are analysed numerically in this paper based on a new formulation of strain gradient plasticity. The problems are the tangential and normal loading of a finite rectangular block of material bonded to rigid platens and having traction‐free ends, and the normal loading of a half‐space by a flat, rigid punch. The solutions illustrate fundamental features of plasticity at the micron scale that are not captured by conventional plasticity theory. These include the role of material length parameters in establishing the size dependence of strength and the elevation of resistance to plastic flow resulting from constraint on plastic flow at boundaries. Details of the finite element method employed in the numerical analysis of the higher order gradient theory will be discussed and related to prior formulations having some of the same features. Copyright © 2003 John Wiley & Sons, Ltd.