CODIMENSION TWO BIFURCATIONS AND HOPF BIFURCATIONS OF AN IMPACTING VIBRATING

ＸｉｅＪｉａｎｈｕａ（谢建华）（ＲｅｃｅｉｖｅｄＯｃｔ．５，１９９４；ＣｏｍｍｕｎｉｃａｔｅｄｂｙＬｉＬｉ）ＣＯＤＩＭＥＮＳＩＯＮＴＷＯＢＩＦＵＲＣＡＴＩＯＮＳＡＮＤＨＯＰＦＢＩＦＵＲＣＡＴＩＯＮＳＯＦＡＮＩＭＰＡＣＴＩＮＧＶＩＢＲＡＴＩＮＧＳＹＳＴ...     

THE REMAINDER－EFFECT ANALYSIS OF FINITE DIFFERENCE SCHEMES AND THE APPLICATIONS

ＴＨＥＲＥＭＡＩＮＤＥＲ－ＥＦＦＥＣＴＡＮＡＬＹＳＩＳＯＦＦＩＮＩＴＥＤＩＦＦＥＲＥＮＣＥＳＣＨＥＭＥＳＡＮＤＴＨＥＡＰＰＬＩＣＡＴＩＯＮＳＬｉｕＲｕ－ｘｕｎ（刘儒勋）ＺｈｏｕＺｈａｏ－ｈｕｉ（周朝晖）（Ｄｅｐｔ．ｏｆＭａｔｈ．Ｕｎｉｖｅｒｓｉｔｙｏ...     

NECESSARY AND SUFFICIENT CONDITIONS FOR THE ABSOLUTE STABILITY OF DISCRETE TYPE LURIE CONTROL SYSTEM

ＮＥＣＥＳＳＡＲＹＡＮＤＳＵＦＦＩＣＩＥＮＴＣＯＮＤＩＴＩＯＮＳＦＯＲＴＨＥＡＢＳＯＬＵＴＥＳＴＡＢＩＬＩＴＹＯＦＤＩＳＣＲＥＴＥＴＹＰＥＬＵＲＩＥＣＯＮＴＲＯＬＳＹＳＴＥＭＺｈａｎｇＪｉｙｅ（张继业）（ＲｅｃｅｉｖｅｄＯｃｔ．５．１９９４；Ｃｏｍｍ...     

Necessary and sufficient conditions for the absolute stability of discrete type lurie control system

ＮＥＣＥＳＳＡＲＹＡＮＤＳＵＦＦＩＣＩＥＮＴＣＯＮＤＩＴＩＯＮＳＦＯＲＴＨＥＡＢＳＯＬＵＴＥＳＴＡＢＩＬＩＴＹＯＦＤＩＳＣＲＥＴＥＴＹＰＥＬＵＲＩＥＣＯＮＴＲＯＬＳＹＳＴＥＭＺｈａｎｇＪｉｙｅ（张继业）（ＲｅｃｅｉｘｅｄＯｃｔ．５．１９９４Ｃｏｍｍｕ...     

Flow of a Viscoplastic Fluid on a Rotating Disk

ＦＬＯＷＯＦＡＶＩＳＣＯＰＬＡＳＴＩＣＦＬＵＩＤＯＮＡＲＯＴＡＴＩＮＧＤＩＳＫＦａｎＣｈｕｎ（范椿）（ＩｎｓｔｉｕｉｅｏｆＭｅｃｈａｎｉｃｓ，ＡｃａｄｅｍｉａＳｉｎｉｃａ，Ｂｅｉｊｉｎｇ）（ＲｅｃｅｉｖｅｄＮｏｖ．２０，１９９２；Ｃｏｍｍｕｎｉｃａｔ...     

ON THE SECOND ORDER WAVE DIFFRACTION IN TWO LAYER FLUIDS

ＯＮ　ＴＨＥ　ＳＥＣＯＮＤ　ＯＲＤＥＲ　ＷＡＶＥ　ＤＩＦＦＲＡＣＴＩＯＮ　ＩＮ　ＴＷＯ　ＬＡＹＥＲ　ＦＬＵＩＤＳＷｕＪｉａｎｈｕａ（吴建华）；ＦａｎｇＹｉｎｇ（方颖）（ＲｅｃｅｉｖｅｄＭａｙ４，１９９５；ＲｅｓｉｖｅｄＪｕｎ．２１，１９９６；Ｃｏｍｍ...     

OBLC domain decomposition for artificial compressible equation

ＯＢＬＣＤＯＭＡＩＮＤＥＣＯＭＰＯＳＩＴＩＯＮＦＯＲＡＲＴＩＦＩＣＩＡＬＣＯＭＰＲＥＳＳＩＢＬＥＥＱＵＡＴＩＯＮＬｉｎＭｉｎｇｓｅｎ（林明森）;ＨｕａｎｇＬａｎｃｈｉｅｈ（黄兰洁）（ＲｅｃｅｉｖｅｄＤｅｃ．１７,１９９４;Ｃｏｍｍｕｎｉｃａｔｅｄｂｙ...     

CHARACTERISTICS OF SUBDIFFERENTIALS OF FUNCTIONS

ＣＨＡＲＡＣＴＥＲＩＳＴＩＣＳＯＦＳＵＢＤＩＦＦＥＲＥＮＴＩＡＬＳＯＦＦＵＮＣＴＩＯＮＳ（郭兴明）ＣＨＡＲＡＣＴＥＲＩＳＴＩＣＳＯＦＳＵＢＤＩＦＦＥＲＥＮＴＩＡＬＳＯＦＦＵＮＣＴＩＯＮＳ￥ＧｕｏＸｉｎｇｍｉｎｇ（ＲｅｃｅｉｖｅｄＪｕｎｅ１６，１９９５...     

FORCED OSCILLATIONS OF BOUNDARY VALUE PROBLEMS OF HIGHER ORDER FUNCTIONAL PARTIAL DIFFERENTIAL EQUATIONS

ＦＯＲＣＥＤＯＳＣＩＬＬＡＴＩＯＮＳＯＦＢＯＵＮＤＡＲＹＶＡＬＵＥＰＲＯＢＬＥＭＳＯＦＨＩＧＨＥＲＯＲＤＥＲＦＵＮＣＴＩＯＮＡＬＰＡＲＴＩＡＬＤＩＦＦＥＲＥＮＴＩＡＬＥＱＵＡＴＩＯＮＳＪｉｎＭｉｎｇＺｈｏｎｇ（靳明忠），ＤｏｎｇＹｉｎｇ（董莹），Ｌｉ...     

ON THE STABILITY OF FORCED DISSIPATIVE NONLINEAR SYSTE

ＯＮＴＨＥＳＴＡＢＩＬＩＴＹＯＦＦＯＲＣＥＤＤＩＳＳＩＰＡＴＩＶＥＮＯＮＬＩＮＥＡＲＳＹＳＴＥＭ￥ＣｈｅｎＤａｄｕａｎ（陈达段）ＬｉｕＸｉａｏｍｉｎｇ（刘晓明）ＳｈｉＷｅｉｈｕｉ（施惟慧）（ＳｈａｎｇｈａｉＵｎｉｖｅｒｓｉｔｙ．Ｓｈａｎｇｈａｉ２００...     

A shear-compression specimen for large strain testing

A new specimen geometry, the shear-compression specimen (SCS), has been developed for large strain testing of materials. The specimen consists of a cylinder in which two diametrically opposed slots are machined at 45° with respect to the longitudinal axis, thus forming the test gage section. The specimen was analyzed numerically for two representative material models, and various gage geometries. This study shows that the stress (strain) state in the gage, is three-dimensional rather than simple shear as would be commonly assumed. Yet, the dominant deformation mode in the gage section is shear, and the stresses and strains are rather uniform. Simple relations were developed and assessed to relate the equivalent true stress and equivalent true plastic strain to the applied loads and displacements. The specimen was further validated through experiments carried out on OFHC copper, by comparing results obtained with the SCS to those obtained with compression cylinders. The SCS allows to investigate a large range of strain rates, from the quasi-static regime, through intermediate strain rates (1–100 s⁻¹), up to very high strain rates (2×10⁴s⁻¹ in the present case).     

A New Shear-Compression-Specimen for Determining Quasistatic and Dynamic Polymer Properties

A new design of the shear compression specimen (SCS) for investigating the viscoelastic shear response of polymers is presented. The specimen consists of a polymer gage section with two metal ends that remain essentially rigid during deformation. Two closed-form analytic models are developed to predict the average stress and strain in the gage section from the deformation-load histories. This new SCS design and its analytic models are thoroughly evaluated via laboratory measurements and numerical simulations. These simulations show that the deformations in the gage section are more uniform than in the original design, and the distribution of the average shear stress and strain are highly homogenous. The simulation results yield good agreement with those of closed-form analytic results and the experiments demonstrate that the new SCS geometry and its analytic models are as reliable as other commonly employed specimens. It can also generate higher strain rates under usual loading conditions because of its smaller specimen gage length. The need for care in specimen preparation is also discussed in detail as illuminated by the experimental and simulation results.

平面波对有部分脱胶衬砌的圆形孔洞的散射

将波函数展开法与奇异积分方程技术相结合研究了平面波对有部分脱胶衬砌的圆形孔洞的散射。将脱离区看作弧形裂纹并忽略裂纹表面的相互作用。将衬砌和基体中的波场展开成Fou-rier-Bessel级数,利用混合边界条件得到一组对偶级数方程组并进一步转化成Hilbert奇异积分方程。数值求解给出了脱离区大小和衬砌厚度对动应力强度因子(DSIF)和散射截面(SCS)的影响。结果显示由于脱胶,动应力强度因子和散射截面呈现明显的低频共振特性。     

试样形状对轴承钢绝热剪切带微观组织的影响

绝热剪切带(ASB)的微观组织受试样几何形状的影响。对圆柱、帽形和剪切压缩型三种不同形状的试样进行分离式霍普金森压杆高速冲击试验，研究试样形状对轴承钢绝热剪切带的形成和微观组织的影响。结果表明，在应变率为1 800～3 100 s^-1的范围内，材料对应变率的敏感性很低。圆柱试样呈现明显的应变硬化，而帽形试样和剪切压缩型试样(SCS)在不同应变率下分别出现应变硬化和无应变硬化的特征，但流变应力并未因应变硬化而提高。试样形状对ASB的微观形貌和组织有很大影响。圆柱试样上产生了窄且细长的ASB，只发生了应变诱发的晶粒细化，属于形变ASB；帽形试样和SCS则形成大片状的ASB，由等轴晶组成，且发生了体心立方体(BCC)马氏体转变为面心立方体(FCC)奥氏体的相变，属于相变ASB。尤其是SCS中ASB的等轴晶，有非常清晰的晶界，是典型的动态再结晶晶粒。温升计算结果显示，圆柱试样ASB的温升远低于奥氏体相变温度，而帽形试样和SCS的温升高于马氏体的熔点，导致局部熔融。     

双钢板混凝土组合板抗爆性能分析

钢-混凝土-钢组合板是一种新型的组合结构,与传统钢筋混凝土板相比,具有抗剪强度高、延性大、耗能能力强等特点,目前已经被广泛应用于核反应堆安全壳、海洋平台及储油罐等结构。本文中,设计并制作了缩尺的普通钢筋混凝土板和钢-混凝土-钢组合板,开展了在接触爆炸荷载作用下的实验研究,通过损伤分析、跨中最大挠度对比研究不同板的抗爆性能。基于ANSYS/LS-DYNA非线性有限元程序,研究了钢-混凝土-钢组合板的损伤模式、跨中最大挠度等,并与实验结果进行了对比分析,验证了有限元分析模型的准确性和适用性。参数化分析了炸药量、混凝土强度和钢板厚度等参数对钢-混凝土-钢组合板抗爆性能的影响规律。利用多参数回归分析方法,提出钢-混凝土-钢组合板跨中挠度的预测公式。结果表明:提高混凝土强度可以降低结构的塑性损伤, 增加钢板厚度可以有效降低钢-混凝土-钢组合板的跨中最大挠度。相对于普通钢筋混凝土板,钢-混凝土-钢组合板保持了良好的整体性,且具有继续承载的能力。拟合公式能够较好地预测钢-混凝土-钢组合板跨中挠度与药量和钢板厚度的关系。     

Combined effects of topography and bottom friction on shoaling internal solitary waves in the South China Sea

A numerical study to a generalized Korteweg-de Vries (KdV) equation is adopted to model the propagation and disintegration of large-amplitude internal solitary waves (ISWs) in the South China Sea (SCS). Based on theoretical analysis and in situ measurements, the drag coefficient of the Chezy friction is regarded as inversely proportional to the initial amplitude of an ISW, rather than a constant as assumed in the previous studies. Numerical simulations of ISWs propagating from a deep basin to a continental shelf are performed with the generalized KdV model. It is found that the depression waves are disintegrated into several solitons on the continental shelf due to the variable topography. It turns out that the amplitude of the leading ISW reaches a maximum at the shelf break, which is consistent with the field observation in the SCS.Moreover, a dimensionless parameter defining the relative importance of the variable topography and friction is presented.     

Determination of the Johnson–Cook Material Parameters Using the SCS Specimen

This note addresses the determination of the Johnson-Cook material parameters using the shear compression specimen (SCS). This includes the identification of the thermal softening effect in quasi static and dynamic loading as well as and the strain rate hardening effect in dynamic loading. A hybrid experimental–numerical (finite element) procedure is presented to identify the constitutive parameters, with an application to Ti6Al4V alloy. The present results demonstrate the suitability of the SCS for constitutive testing.     

损伤体有效弹性性质的细观分析和不变性描述—— 一个考虑微缺陷相互作用的一般理论模式

通过引进微缺陷相互作用张量，建立了一个二维情况下考虑微缺陷（微裂纹或微孔洞）间相互作用的损伤固体有效弹性性质的一般理论模式模型中考虑了微缺陷的几何形状、取向分布和空间分布所造成的有效柔度张量的各向异性和材料中微缺陷之间的相互作用所引起的损伤柔度张量的高阶效应针对微椭圆孔、微圆孔和微裂纹问题，求得了相互作用张量的解析形式     

Quadratic stochastic estimation of far‐field acoustic pressure with coherent structure events in a 2D compressible plane mixing layer

Mathematical tools based on cross correlations between aerodynamic quantities of interest inside the shear flow region and the radiated sound pressure are used to investigate noise generation mechanisms in a plane compressible mixing layer. An original methodology relying on an efficient coupling between proper orthogonal decomposition (POD) and stochastic estimation procedures is developed to analyze the main aerodynamic mechanisms that govern noise production. POD is used to split the instantaneous flow fluctuations as the sum of three components: the large‐ and small‐scale coherent structures (LCS and SCS) and the background quasi‐Gaussian fluctuations. Based on this flow partitioning, quadratic stochastic estimation is implemented to estimate the far‐field acoustic pressure associated with each flow component. The far field acoustic pressure associated with both LCS and SCS is then investigated. By analyzing the RMS and temporal spectra of the far‐field acoustic pressure, it is observed that the SCSs, as defined thanks to the POD basis, are responsible for the main part of the noise emission. Copyright © 2009 John Wiley & Sons, Ltd.     

Numerical validation of the shear compression specimen. Part I: Quasi-static large strain testing

The shear compression specimen (SCS), which is used for large strain testing, is thoroughly investigated numerically using three-dimensional elastoplastic finite element simulations. In this first part of the study we address quasi-static loading. A bi-linear material model is assumed. We investigate the effect of geometrical parameters, such as gage height and root radius, on the stress and strain distribution and concentration. The analyses show that the stresses and strains are reasonably uniform on a typical gage mid-section, and their average values reflect accurately the prescribed material model. We derive accurate correlations between the averaged von Mises stress and strain and the applied experimental load and displacement. These relations depend on the specimen geometry and the material properties. Numerical results are compared to experimental data, and an excellent agreement is observed. This study confirms the potential of the SCS for large strain testing of material.