Qualitative analysis for the solution of Kuramoto-Sivashinsky equation

ＷｅｗｉｌｌｃｏｎｓｉｄｅｒｔｈｅｆｏｌｌｏｗｉｎｇＫｕｒａｍｏｔｏ＿Ｓｉｖａｓｈｉｎｓｋｙｅｑｕａｔｉｏｎ［１,２］ｗｉｔｈｏｂｖｉｏｕｓｐｈｙｓｉｃａｌｍｅａｎｉｎｇｓａｎｄｍｅｃｈａｎｉｃａｌｍｏｄｅｌｓ：ｕｔ＋ε４ｕｘ４＋２ｕｘ２＋ｕｕｘ＝０,（１）ｗｉｔｈｔｈｅｉｎｉｔｉａｌｃｏｎｄｉｔｉｏｎ：ｕ（ｘ,０）＝φ（ｘ）,（２）ａｎｄｔｈｅｂｏｕｎｄａｒｙｃｏｎｄｉｔｉｏｎ：ｕ（－ｌ,ｔ）＝ｕ（ｌ,ｔ）＝ｕｘ２（－ｌ,ｔ）＝ｕｘ２（ｌ,ｔ）＝０,（３ａ）ｏｒｔｈｅｂｏｕｎｄ…     

LY12复合型断裂的实验研究

应用有限元方法和断裂实验对铝合金ＬＹ１２在Ｉ＋Ⅱ型复合载荷作用下的弹塑性断裂行为进行了研究，给出了复合型弹塑性断裂的Ｊ积分准则，结果表明：（１）不同复合型下启裂Ｊ积分值满足ＪＩｉ／ＪＩｃ＋ＪⅡｉ／ＪⅡｃ＝１，ＪＭＣ＝ＪＩｉ＋ＪⅡｉ的关系，随Ⅱ型分量增加，启裂的Ｊ积分值ＪＭＣ增加ＪＩＣ为ＪＩＣ的两部；（２）ＪＭＣ值与复合比满足ＪＭＣ＝Ｋ＾２Ｉ．ＪＩＣ／（Ｋ＾２１＋αＫ＾２ＩＩ）＋αＫ＾２Ｉ．ＪＩＣ／     

A complete expression of the asymptotic solution of differential equation with three-turning points

Ｗｅｈａｖｅｄｉｓｃｕｓｓｅｄｃｏｎｃｅｐｔｏｆｅｑｕａｔｉｏｎｗｉｔｈｎ＿ｔｕｒｎｉｎｇｐｏｉｎｔｓｉｎｍｙｐａｐｅｒ［１］,ｉ．ｅ．,ａｓｅｃｏｎｄｏｒｄｅｒｌｉｎｅａｒｏｒｄｉｎａｒｙｄｉｆｆｅｒｅｎｔｉａｌｅｑｕａｔｉｏｎｄ２ｙｄｘ２＋［λ２ｑ１（ｘ）＋λｑ２（ｘ,λ）］ｙ＝０,ｗｈｅｒｅｑ１（ｘ）＝（ｘ－μ１）（ｘ－μ２）…（ｘ－μｎ）ｆ（ｘ）,ｆ（ｘ）≠０,ａｎｄλｉｓａｌａｒｇｅｐａｒａｍｅｔｅｒ．Ａｌｔｈｒｏｕｇｈｔｈｅｆｉｒｓｔｔｅｒｍｏｆｔｈｅａｓｙｍｐｔｏｔｉｃｅｘｐａｎ…     

LARGE AMPLITUDE VIBRATION OF CIRCULAR SANDWICH PLATE

ＬＡＲＧＥＡＭＰＬＩＴＵＤＥＶＩＢＲＡＴＩＯＮＯＦＣＩＲＣＵＬＡＲＳＡＮＤＷＩＣＨＰＬＡＴＥＳＤｕＧｕｏ－ｊｕｎ（杜国君）（ＮｏｒｉｈｅａｓｉＩｎｓｔｉｔｕｔｅｏｆＨｅａｖｙＭａｃｈｉｎｅｒｙ,Ｑｉｑｉｈａｒ）（ＲｅｃｅｉｖｅｄＪａｎ．２,１９９２,...     

一类非线性离散人口模型的稳定性和振动性

本文讨论了非线性差分方程ｘｎ＋１＝ｘｎ／１－ａ－ｂｘｎ－ｋ＋ｃｘ＾２ｎ－ｋ平衡点的稳定性，并获得了此方程在条件ａ∈（１，∞），ｂ∈（－∞，＋∞）＝Ｒ，ｃ∈（０，∞）下其正解的渐近性质及其关于正平衡点振动的充分条件，且当Ｋ＝０时建立了正平衡点渐近稳定的充分必要性准则。’     

Reciprocal theorem method for solving the problems of bending of thick rectangular plates

ＲＥＣＩＰＲＯＣＡＬＴＨＥＯＲＥＭＭＥＴＨＯＤＦＯＲＳＯＬＶＩＮＧＴＨＥＰＲＯＢＬＥＭＳＯＦＢＥＮＤＩＮＧＯＦＴＨＩＣＫＲＥＣＴＡＮＧＵＬＡＲＰＬＡＴＥＳＦｕＢａｏ－ｌｉａｎ（付宝连）Ｔａｎｗｅｎ－ｆｅｎｇ（谭文锋）（ＹａｎｓｈａｎＵｎｉｒｅｒｓｉｔ...     

几种铝锡硅铜合金的摩擦磨损特性

采用环－块摩擦磨损试验机，考察了含Ｓｉ质量分数为１％～５％的Ａｌ－２０Ｓｎ－Ｓｉ－１Ｃｕ合金及传统的Ａｌ－２０Ｓｎ－１Ｃｕ合金的摩擦磨损性能．结果表明：几种Ａｌ－２０Ｓｎ－Ｓｉ－１Ｃｕ合金的磨损率低于Ａｌ－２０Ｓｎ－１Ｃｕ合金的磨损率，并且随Ｓｉ含量的增加而降低．干摩擦时，摩擦因数随Ｓｉ含量的增加无明显变化；油润滑时摩擦因数则随Ｓｉ含量的增加而略微减小．两类合金的摩擦因数均随滑动速度的增加而减小，随摩擦时间的增加先增加后减小并趋于稳定．磨损表面的ＳＥＭ分析表明：Ａｌ－２０Ｓｎ－Ｓｉ－１Ｃｕ合金在干摩擦下的磨损机制主要是磨粒磨损和氧化磨损，而Ａｌ－２０Ｓｎ－１Ｃｕ合金则包括粘着、疲劳及磨粒磨损等多种形式．在油润滑下，两者的磨损机理则分别为犁削作用和疲劳磨损及分层磨损．     

TRANSFER OPEN OR CLOSED SETVALUED MAPPING AND GENERALIZ－ATION OF H－KKM THEOREM WITH APPLICATIONS

ＴＲＡＮＳＦＥＲＯＰＥＮＯＲＣＬＯＳＥＤＳＥＴＶＡＬＵＥＤＭＡＰＰＩＮＧＡＮＤＧＥＮＥＲＡＬＩＺ－ＡＴＩＯＮＯＦＨ－ＫＫＭＴＨＥＯＲＥＭＷＩＴＨＡＰＰＬＩＣＡＴＩＯＮＳＬｉＢｉｎｇ－ｙｏｕ（李秉友）;ＳｕＪｉａ－ｂａｏ（苏家宝）（Ｄｅｐａｒｔｍｅｎｔ...     

射弹倾斜撞击带盖板炸药引发爆轰的条件

用二级轻气炮发射圆柱形、球形钢射弹以不同的角度撞击带不同厚度钢盖板的 ＴＮＴ／ＲＤＸ（４０／６０）炸药，得到了不同条件下引发炸药爆轰的阈值射弹速度。可以用ｖｄ~　（１／２）＝（１ ＋ｋ）［Ａ＋Ｂｈ／（ｄｃｏｓ）］描述临界引爆条件。对于带钢盖板的ＴＮＴ／ＲＤＸ（４０／６０）炸药，Ａ＝ ３．３３．Ｂ＝５．３４；圆柱形平头射弹撞击，ｋ／７５，球形射弹撞击，ｋ０．５＋０．２（１／ｃｏｓ－１）。由 此，本研究将Ｊａｃｏｂｓ 引爆判据推广到了斜碰撞条件。     

Generalized variational principles of symmetrical elasticity problem of large deformations

ＧＥＮＥＲＡＬＩＺＥＤＶＡＲＩＡＴＩＯＮＡＬＰＲＩＮＣＩＰＬＥＳＯＦＳＹＭＭＥＴＲＩＣＡＬＥＬＡＳＴＩＣＩＴＹＰＲＯＢＬＥＭＯＦＬＡＲＧＥＤＥＦＯＲＭＡＴＩＯＮＳＺｈａｏＹｕ－ｘｉａｎｇ（赵玉祥）ＧｕＸｉａｎｇ－ｚｈｅｎ（顾祥珍）ＬｉＨｕａｎ－ｑｉｕ...     

温度对金属材料钼位错发射的影响

应用关联参照模型、随位错位置变化的柔性位移边界条件和三维分子动力学方法研究了体心立方（ＢＣＣ）金属晶体钼在不同温度下裂尖发射位错的力学行为，随着温度的提高，不但发射位错的临界应力强度因子下降而且在同一应 度因子条件下，发射位错的数量出增加，位错速度和不全位错之间的扩展距离对温度不敏感，在位错发射过程中，发现了稳定的和不稳定的两个变形状态，在稳定的有状态，位错发射后，塞积在远离裂纹尖端处；必须增加外     

分子动力学方法在研究材料力学行为中的应用进展

报道近年来分子动力学方法应用于研究位错、裂纹、晶界及其相互作用方面的进展．主要包括:裂纹尖端的位错发射,位错发射的不稳定堆垛能,晶体与裂纹’几何关系对位错发射的影响,温度对位错发射的影响以及由裂纹尖端发射的位错列与不对称倾侧晶界的相互作用．报道主要以我们的工作为主,重点讨论裂纹尖端位错发射的研究结果      

压电双材料界面钝裂纹附近螺型位错的屏蔽效应与发射条件

研究了压电双材料界面钝裂纹附近螺型位错的屏蔽效应与发射条件.应用保角变换技术,得到了复势函数与应力场的封闭形式解,讨论了位错方位、双材料电弹常数及裂纹钝化程度对位错屏蔽效应和发射条件的影响.结果表明,Burgers矢量为正的螺型位错可以降低界面钝裂纹尖端的应力强度因子(屏蔽效应),屏蔽效应随位错方位角及位错与裂纹尖端距...     

Effect of temperature on dislocation emission from crack tip for BCC metal Mo

The effect of thermally activated energy on the dislocation emission from a crack tip in BCC metal Mo is simulated in this paper. Based on the correlative reference model on which the flexible displacement boundary scheme is introduced naturally, the simulation shows that as temperature increases the critical stress intensity factor for the first dislocation emission will decrease and the total number of emitted dislocations increase for the same external load. The dislocation velocity and extensive distance among partial dislocations are not sensitive to temperature. After a dislocation emission, two different deformation states are observed, the stable and unstable deformation states. In the stable deformation state, the nucleated dislocation will emit from the crack tip and piles up at a distance far away from the crack tip, after that the new dislocation can not be nucleated unless the external loading increases. In the unstable deformation state, a number of dislocations can be emitted from the crack tip continuously under the same external load. The project is supported by the National Natural Science Foundation of China.     

Nanoscale rotational deformation effect on dislocation emission from an elliptically blunted crack tip in nanocrystalline materials

A grain size-dependent model is theoretically established to describe the effect of a special physical micromechanism of plastic flow on the dislocation emission from an elliptical blunt crack tip in nanocrystalline solids. The micromechanism represents the fast nanoscale rotational deformation (NRD) occurring through collective events of ideal nanoscale shear near crack tips, which as a stress source is approximately equivalent to a quadrupole of wedge disclinations. By the complex variable method, the grain size-dependent criterion for the dislocation emission from an elliptical blunt crack tip is derived. The influence of the grain size and the features of NRD on the critical stress intensity factors for dislocation emission is evaluated. The results indicate that NRD releases the high stresses near the crack tip region and thereby enhances the critical stress intensity factor for dislocation emission. The NRD has great influence on the most probable angle for dislocation emission. The critical stress intensity factor will increase with the increment of the grain size, which means the emission of the dislocation becomes more difficult for larger grain size due to the effect of NRD.     

Effects of surface diffusion and resolved shear stress intensity factor on environmentally assisted cracking

Hydrogen induced crack-tip plastic deformation has been known as the primary mechanism of hydrogen assisted cracking and stress corrosion cracking. It has been systematically shown that the same mechanism of environmentally assisted crack-tip dislocation emission causes hydrogen assisted cracking, stress corrosion cracking, and liquid metal embrittlement cracking.An embrittling chemical species has to reach a crack tip in order to accelerate crack growth. Very close to a sharp crack tip, surface diffusion is shown to be the dominant transport process of embrittling species for stage-II crack growth. The role of surface diffusion in stage II crack growth is analyzed. The constant cracking velocity is proportional to the surface diffusion coefficient of an embrittling species and inversely proportional to a length parameter, , which is related to the transport process upstream.Dislocation emission at a crack tip is driven by crack-tip resolved shear stress. Crack-tip resolved shear stress field is characterized by resolved shear stress intensity factor, K_RSS·K_RSS is defined, the procedure for its calculation outlined, and its applications to crack-tip dislocation emission and environmentally assisted cracking discussed.     

弹性波与单侧界裂纹相互作用问题的边界元法

措助边界元法设计了一种迭代修正方法来求解单侧界面裂纹模型与弹性波的相互作用问题,作为对算法的检验,用这种方法我们具体地分析了平面简谐弹性波对一个则界面裂纹的入射,给出了裂纹面的接触形态及应力场。     

Transient dislocation emission from a crack tip under dynamic mode III loading

Summary  Transient dislocation emission from a crack tip under dynamic mode III loading is analyzed. By taking into account the dynamic interaction between the crack and dislocation, the governing equation for the dislocation motion is derived under the quasi-steady assumption. The behavior of dislocation emission is explored in detail by solving this equation numerically. A critical initial speed can be determined, which must be exceeded by dislocations to escape from the crack tip. The dislocation emission process is found to be completed in such a short time period that the applied load may be approximately treated as constant during dislocation emission. Based on this fact, an asymptotic criterion for transient dislocation emission is developed, from which the critical initial speed can be evaluated. In the case that the dislocation is emitted from rest, we recover the quasi-static criterion of dislocation emission. Received 22 November 2000; accepted for publication 20 March 2001     

A STUDY OF J-INTEGRAL OF THE ORTHOTROPIC COMPOSITE MATERIAL

ＡＳＴＵＤＹＯＦＪ－ＩＮＴＥＧＲＡＬＯＦＴＨＥＯＲＴＨＯＴＲＯＰＩＣＣＯＭＰＯＳＩＴＥＭＡＴＥＲＩＡＬＷａｎｇＡｉ－ｑｉｎ（王蔼勤）；ＦｅｎｇＢａｏ－ｌｉａｎ（冯宝莲）；ＹａｎｇＷｅｉ－ｙａｎｇ（杨维阳）（ＴａｉｙｕａｎＨｅａｖｙＭａｃｈｉｎｅｒｙ．...     

螺型位错偶极子与界面钝裂纹的干涉效应

研究了螺型位错偶极子与界面钝裂纹的干涉效应.应用保角变换技术,得到了复势函数与应力场的封闭解析解,讨论了位错偶极子方位、臂长及裂纹钝化程度对位错偶板子屏蔽效应和发射条件的影响.结果表明,与单个螺型位错不同,螺型位错偶极子与x轴夹角在一定范围内时才可以降低界面钝裂纹尖端的应力强度因子(屏蔽效应),屏蔽效应随偶板子臂长的增大而增强,随裂纹钝化程度的增大而增强,屏蔽区域也随裂纹钝化程度的增大而增大;位错偶极子发射所需的临界无穷远加载随偶极子臂长的增加而减小,随位错方位角及裂纹钝化程度的增加而增大;最可能的位错偶极子发射角度为0.螺型位错偶极子的发射比单个螺型位错的发射要困难.本文解答的特殊情况与相关文献给出的解答一致.