高应变区准三维模型失效评定曲线FAC的研究

本文推导了压力容器高应变区准三维模型的分段弹塑性Ｊ积分工程估算公式，并由此建立了高应变区失效评定曲线ＦＡＣ，并与二维模型及英国的选择１曲线作了比较，以便为合理地制定我国接管高应变区的失效评定曲线提供一定的参考依据。     

热带粗轧机组立过程的三维有限元模拟

本文采用全三维刚塑性有限元法对室温下的铝和不同温度下的２Ｓ－Ａｌ平辊侧压稳定变形过程进行了解析，计算结果和实测值吻合较好，较明显地提高了计算精度，并提出了用超薄单元近似处理奇异点的办法，使计算编程简化，能迅速地得到了较好的解。     

平板试件孔边塑性区的研究

小孔缺陷对受力平板试件的承栽能力有着重要的影响。本文采用应力函数法和叠加原理，推导出了单向拉伸平板试件孔边应力场；利用该应力场公式、主应力公式和Mises屈服方程推导出了孔边塑性区方程，利用Mathematica软件求解出孔边塑性区尺寸-r和θ，并绘出了无限大单向拉伸平板试件的孔边塑性区。采用退火态SUS304—2B不锈钢和热轧态LC52铝舍金两种材料的带孔平板试件进行单向拉伸实验，通过实验结果与上述孔边应力集中理论的分析比较发现，由于塑性钝化使得单向拉伸带孔平板试件的实际承载能力与理论计算存在一定差别。     

热带粗轧机组立轧过程的三维有限元模拟

本文采用全三维刚塑性有限元法对室温下的铝和不同温度下的２Ｓ－Ａｌ平辊侧压稳定变形过程进行了解析，计算结果和实测值吻合较好，较明显地提高了计算精度。并提出用超薄单元近似处理奇异点的办法，使计算编程简化，能迅速地得到较好的解     

盒形件拉延成形的刚塑性有限元数值模拟

本文采用刚塑性有限元理论，开发了一个二维数值模拟程序系统，对盒形件拉延成形中的法兰变形区进行了较全面的数值模拟，研究了冲压成过程中法兰变形区的金属流动规律。     

超塑处理对喷射成形GCr15钢超塑性的影响

研究了超塑处理对喷射成形GCr15钢超塑性的影响，超塑性拉实验结果表明，未经超塑处理的铸态试样，延伸率为119％，经过二次油淬和二次油淬＋高温回火超塑处理的两种试样，延伸率分别为328％和671％，变形温度和应变速率对GCr15钢的超塑性有一定的影响，但材料的微观组织对其超塑性具有决定性作用，超塑处理改变了材料试样的微观组织，导致其超塑性发生变化，经过二次油淬＋高温回火超塑处理后试样具有球化组织，其超塑性最好，未经超塑处理的铸态试样具有珠光体组织，超塑性最差，经过二次油淬超塑处理后试样的组织是马氏体和少量碳体物的混合，其超塑性介于上述两种试样之间，喷射成形工艺使GCr15钢获得均匀细化的稳定组织，这对于细晶超塑性是必要的，超塑处理材料的超塑性得到更大的提高。     

椭圆异型挤压塑性成形映射理论及模腔优化解析

针对金属椭圆异型挤压塑性成形及模腔优化的理论课题,应用复变共形映射数学研究成果,利用奇偶点相互迭代的三角插值法和法线收敛法,将三维金属异型挤压塑性成形问题转化为二维轴对称成形问题,求解异型挤压模腔曲面函数,建立映射函数解析方法,推导椭圆异型材挤压金属塑性成形连续流动场和应变速度场的数学解析式,并应用金属塑性成形能量极值原理,进行异型材挤压模腔参数的优化,同时为精密快速地实现挤压模腔的CAD/CAM一体化目标提供技术支持。     

框架结构“人控塑性铰”减震效应研究

本文基于框架结构杆模型时程分析法引入分段变刚度杆单元和退化双线性恢复力骨架曲线，建立了钢筋混凝土二维框架结构地震反应弹塑性时程分析理论模型，对滞回拐点提出了一个行之有效的处理方法，以构件强度比作为控制手段，研究了塑性铰出现部位不同对结构地震反应的影响，得到了一些规律性认识和有益的结论，对实际工程具有重要的参考价值和应用前景。     

露天矿山三维设计方法应用研究

针对传统露天矿山开采设计采用二维方式的不直观、低效率等缺点,提出了露天矿山的全三维设计方法.首先以矿业三维软件为平台创建矿床地质模型,利用统计学方法进行品位赋值,形成地质品位计算模型,在此基础上利用三维有限元计算方法进行开采境界边坡角及边坡台阶组合参数优化研究.借助境界圈定及三维排产程序进行采剥方案、生产规模、开采境界...     

图像配准参数的自适应求取方法

提出了一种可见光和红外图像的自动配准方法，针对多数配准过程需人工干预的问题，建立二维仿射变换模型，以图像边界为特征，以目标边界互相关函数最大为原则，对二维仿射变换模型自适应搜索求取最佳配准参数，给出了实际可见光和红外图像配准的实验结果。     

A generalized elastoplastic plate theory and its algorithmic implementation

In continuum mechanics within specific classes of problems, one- or two-dimensional theories are often simpler to apply than the more complete three-dimensional one. This is, for example, the case of thin bodies, such as plates or shells, which may be studied using appropriate two-dimensionai theories. Within this approach, the reduction of the dimension is traded for a loss of information relative to the motion in the transverse direction. For example, in the case of non-linear material behaviour, classical plasticity plate theories are usually not able to model the effects related to the spreading of plasticity through the cross-section. In the present paper we discuss a generalized plasticity plate model, which can be used to reproduce some of the three-dimensional effects in a two-dimensional setting. We present the continuous and the discrete time model, including both isotropic and kinematic hardening mechanisms; moreover, the form of the tangent matrix consistent with the discrete model is addressed. Finally, some examples (cantilever beam, clamped circular plate and clamped square plate under monotonic and cyclic loading) are studied numerically using a three-dimensional classical plasticity theory, a classical plasticity plate theory and the proposed plate theory. The generalized plasticity plate model matches the three-dimensional response with greater accuracy, than the classical plasticity plate model.     

Three-dimensional analyses of plastic constraint for through-thickness cracked bodies

A three-dimensional strip yield model has been proposed to rationalize effects of out-of-plane and in-plane constraints. By use of the model, plastic constraints around a straight-through crack in finite thick plates made of strain hardening materials are analyzed. A global constraint factor α is defined to simulate the three-dimensional effects in two-dimensional analysis. Effects of thickness and stress states on the size of crack-tip plastic zone and α are studied in detail. A unique variation curve of α against normalized thickness is obtained for different combination of materials, load levels and geometry. Influences of the in-plane constraint on the α-thickness curve are analyzed as well. It is shown that the influence of T-stress can be considerable only if the plastic-zone size becomes comparable to the crack length. The difference between the present results and Newman, Bigelow and Shivakumer's three-dimensional finite element results is within 6% over a large range of thickness and stress levels. The three-dimensional shape of the plastic zone is discussed as well. Potential applications of the model are discussed and it is shown by an example that the present model can be used to explain the effects of thickness upon fatigue crack growth.     

Fatigue crack growth in a fillet welded joint

Existing theories for the growth of cracks at weld toes have proved difficult to verify because of a lack of experimental proof at short crack depths and slow growth rates. Arbitrary initial defect sizes have been employed in life calculations coupled with approximate two-dimensional stress analyses. In this study, the fatigue performance of a stress relieved fillet weld is determined by both theory and experiment. Crack growth results for shallow (less than 1 mm depth) elliptical cracks at weld toes are used to test an elastic expression for stress intensity using a correction factor from a three-dimensional stress analysis. No evidence of higher than expected growth rates, observed by others for very short cracks and cracks in notch plastic zones, is apparent. Integration of a growth law that includes the threshold stress intensity factor provides fatigue life predictions for various stress ratios and from experimentally measured defect depths. Needle peening the weld toe improves the fatigue life by retarding crack growth up to 1 mm below the weld toe.     

Steady crack growth in a thin, ductile plate under small-scale yielding conditions: Three-dimensional modeling

This work employs high resolution, finite element computations to investigate key features of the elastic–plastic fields near a steadily advancing crack at quasi-static rates under three-dimensional, small-scale yielding conditions. The model represents a structurally thin component constructed of a material (e.g., Al and Ti alloys) with flow stress and fracture toughness properties that together limit the size of the in-plane plastic zone during steady-growth to no more than several multiples of the plate thickness. The computational approach generalizes the streamline integration procedure used previously for two-dimensional studies into three dimensions to represent steady-state growth on a fixed mesh in a boundary-layer framework. The plate thickness provides the only geometrical length scale. Crack extension occurs at the remotely applied, fixed loading without the need for a local growth criterion. In the first computations of this type, the present work considers a straight crack front advancing under local and global mode I loading with zero T-stress in a moderately hardening material. Applied remote loads at steady growth generate plastic zone sizes ahead of the advancing crack front ranging from 0.25 to 6.4 times the thickness. Key results include: (1) the crack-front fields exhibit a self-similar scaling characterized by a non-dimensional loading parameter; (2) three-dimensional effects extend to distances of approximately 1.5–2.5 times the thickness ahead of the advancing crack front for key values of this loading parameter, beyond which the fields (elastic–plastic then linear-elastic at greater distances) become uniform over the thickness; and (3) crack opening profiles on the outside surface reveal a “wedge-like”, opening shape which simplifies the definition of a crack-tip opening angle.     

用变分渐近法进行复合材料层合板仿真及三维场重构

为有效模拟和准确重构复合材料层合板三维应力/应变/变形场,基于变分渐近方法构建单斜对称的复合材料层合板渐近修正理论和重构关系。主要内容包括:基于旋转张量分解概念用一维广义应变和翘曲表示板的三维应变场,以考虑包括板翘曲变形在内的所有变形;基于变分渐近法将原三维问题分析严格拆分为非线性二维板分析(等效单层板模型)和沿法线方向的一维线性分析;通过层合板厚跨比和二维应变量阶数2个较小参数将应变能渐近修正到第二阶,并转换为Reissner形式以便于实际应用;利用生成的二维板变形和翘曲函数精确重构三维场。通过一具有20层复合层合板的柱形弯曲算例表明:基于该理论和重构过程开发的渐近变分程序VAPAS重构生成的三维应力场精确性较一阶剪切变形理论和古典层合理论更好,与三维有限元精确解相一致。     

Effect of Plate Thickness on Crack-Tip Plasticity

This paper presents an analytical method for determining the three-dimensional stress fields in plates with a through-the-thickness crack, especially under elastic-plastic conditions. Using the generalised plane strain theory in conjunction with the deformation theories of plasticity, exact solutions are obtained for the effects of plate thickness on the crack-tip plastic zone size and a plastic constraint factor, which is shown to correlate well with published finite element solutions.     

Modeling of a folded plate

It is shown that the solution of a three-dimensional linear elasticity problem in a thin folded plate converges strongly inH ¹ to a solution of a two-dimensional model as the thickness goes to 0. This model consists of two plate equations coupled through their common edge.     

Three-dimensional analysis of an all-round clamped plate made of functionally graded materials

Summary A three-dimensional study for the static response of a clamped rectangular plate made of functionally graded material is presented. The governing equation of the plate is derived by the Ritz energy method within the linear, small deformation theory of elasticity. A power-law distribution for the mechanical characteristics is adopted to model the continuous variation of properties from those of one component to those of the other. The displacements and stresses of the plate for different values of the power-law exponent and thickness-side ratios are investigated. The developed three-dimensional elasticity solution by the multiterm Ritz method appears to be important because it can be used to assess the accuracy of both the two-dimensional theories as well as that of the numerical methods.     

Layered plate with discontinuous connection: Exact mathematical model

The subject of this paper is the plate composed of two identical layers connected to each other in a discontinuous way, i.e. via discontinuous elements (connectors). This paper presents a model that describes the mechanical behavior of this plate by a system of exact, analytical (explicit) equations. The discrete distribution of discontinuous connectors is replaced by a fictitious continuous medium (interlayer). Accordingly, the plate is modeled as an equivalent three-layered plate: Two outer layers and a connecting inner interlayer. In order to obtain a fast and easy to use tool, something that is necessary for an analytical model to be chosen over finite elements and empirical formulas, modeling process is developed within the framework of two-dimensional elasticity. In so doing, the model also represents a means for attaining full comprehension of the mechanical phenomena that are involved, something that neither three-dimensional elasticity nor finite elements and empirical formulas can attain. The transition from three to two-dimensional behavior is obtained by relating the normal stress in the direction transverse to the plate to the distortion in the interlayer. The two-dimensional behavior is governed using kinematic and force assumptions that do not impose appreciable constraints on the stress–strain state and structural behavior. Starting from these assumptions, the paper develops the relationships between displacements and interface stresses, for both continuous and discontinuous connection. The latter relationships, which are used in this model, and the former relationships, which were used in a previously presented model, are discussed and compared to each other. The subsequent sections of the paper describe the model and present some real case applications of discontinuously-connected layered plate.     

条层法及其对板带轧制三维变形的仿真

提出一种模拟板带轧制过程三维变形的新的数值方法——条层法。首先沿高向将变形区均匀地划分为若干层,然后再沿着金属的流动轨迹将变形区内的每层带材划分为若干流线条元,为了方便分析和计算,又将流线条元映射为矩形条元。横向位移的纵向分布被构造为四次曲线,横向分布用三次样条插值函数表示,高向分布用二次曲线拟合。根据塑性力学流动理论,分析推导了变形区三维变形和应力的数学模型。与作者曾经提出的流线条元法相比,考虑了应力与变形沿高向的不均匀分布,实现了精确的三维分析和计算。关于热带钢连轧和厚板轧制的仿真实例表明,提出的方法和模型符合实际,为板带轧制过程的三维力学仿真提供了一个新的实用工程数值方法。