Electroelastic interaction between a piezoelectric screw dislocation and a confocal elliptic blunt crack with elliptical inhomogeneity

The electroelastic interaction between a piezoelectric screw dislocation and an elliptical inhomogeneity containing a confocal blunt crack under infinite longitudinal shear and in-plane electric field is investigated. Using the sectionally holomorphic function theory, Cauchy singular integral, singularity analysis of complex functions and theory of Rieman boundary problem, the explicit series solution of stress field is obtained when the screw dislocation is located in inhomogeneity. The intervention law of the interaction between blunt crack and screw dislocation in inhomogeneity is discussed. The analytical expressions of generalized stress and strain field of inhomogeneity are calculated, while the image force, field intensity factors of blunt crack are also presented. Moreover, a new matrix expression of the energy release rate and generalized strain energy density (SED) are deduced. With the size variation of blunt crack, the results can be reduced to the case of the interaction between a piezoelectric screw dislocation and a line crack in inhomogeneity. Numerical analysis are then conducted to reveal the effects of the dislocation location, the size of inhomogeneity and blunt crack and the applied load on the image force, energy release rate and strain energy density. The influence of dislocation on energy release rate and strain energy density is also revealed.     

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通过对套铣筒这种特殊结构钻柱的分析,在现有钻柱力学模型研究的基础上,针对 套铣筒结构特点(大筒径、薄壁筒型钻柱),建立套铣筒与井壁接触力学模型,通过分析套铣 管柱在井下屈曲状态以及与井壁接触压力的计算,对套铣筒进行力学分析以及摩阻力计算.     

PROGRESS IN MEASUREMENT TECHNOLOGY FOR DRILL STRING VIBRATION

随着深井、超深井数量的快速增加, 钻柱振动导致的钻具失效问题更加突出. 针对钻柱振动的研究可分为理论与数值模拟、测量分析两种方法. 由于钻柱振动具有复杂的非线性特征, 使得理论与数值模拟研究受到了很大限制, 因此井下振动测量技术的研究显得尤为重要. 本文比较全面和系统地介绍了国内外钻柱振动测量技术研究现状和进展情况, 并对几个应用较为成熟的国外测量系统的工作原理、分析方法及应用技术进行了详细的综述. 所得结论可为我国井下振动测量技术的发展提供重要参考.     

New method for geometric nonlinear analysis of large displacement drill strings

Introduction Drillstringsina3Dlargedisplacementwellboreareusuallyregardedas3Dcurved beamswithlargedisplacementandlargerotationbutwithsmallstrain,thus,therelationship betweenstressandstrainislinear.Thedeformationofdrillstringscanbecomposedoftwo parts:oneiscalledtheinitialdeformationcausedwhentheaxisofthedrillstringisdeformed fromitsstraightconfigurationtothepositioncoincidentwiththewellaxis,involvinglarge rotationsandwiththeimplicationoffiniterotationalproblem.Theotheristhedeformation fromthew…     

DKDP晶体的柱面形貌与缺陷分析

采用原子力显微镜观测全方位生长的DKDP晶体的{100}面形貌,发现有螺旋位错,由此推断DKDP晶体{100}面以螺旋位错机制生长;利用同步辐射X射线白光形貌术观测了DKDP晶体缺陷,探讨了不同生长条件及生长阶段对晶体完整性的影响.     

Analysis for a screw dislocation accelerating through the shear-wave speed barrier

An analysis is performed for an accelerating screw dislocation through the shear-wave speed barrier. At this instant, the function that determines the interval of the path of the dislocation motion that contributes to the wave front has roots that change from a pair of complex conjugate to a double real, which subsequently splits into two real ones. The analysis is performed at this transition to supersonic that occurs at the double root maximum of the function that defines the interval of the dislocation path that contributes to the field points. It is found that the stress has a log|ξ-ξ^*|/|ξ-ξ^*|^1/2 singularity in the coefficient of the delta function of the forming Mach front, implying that for this phenomenon the Volterra dislocation model has too strong a discontinuity (step-function) in the displacement to be meaningful. A ramp-core displacement dislocation model analysis, which removes the singularity in the stress, is presented. These results can be useful in a multiscale dislocation dynamics modeling with inertia effects.     

A moving screw dislocation near interfacial rigid lines in two dissimilar anisotropic media

This paper attempts to investigate the problem for the interaction between a uniformly moving screw dislocation and interface rigid lines in two dissimilar.anisotropic. materials. Integrating Riemann-Schwarz＇s symmetry principle with the analysis singularity of complex functions, we present the general elastic solutions of this problem and the closed form solutions for interfaces containing one and two rigid lines. The expressions of stress intensity factors, at the rigid line tips and image force acting on moving dislocation are derived explicitly. The results show that dislocation velocity has an antishielding effect on the rigid line tip and a larger dislocation velocity leads to the equilibrium position of dislocation closing with the rigid line. The presented solutions contain previously known results as the special cases.     

双螺杆冻胶纺丝法制备有机液体吸附功能纤维及其性能研究

在聚合釜中合成了BMA/HEMA二元共聚树脂,利用双螺杆纺丝机、采用冻胶纺丝技术制备了有机液体吸附功能纤维,研究了单体投料比中HEMA质量分数对纤维各种溶胀行为的影响,利用动态热机械分析仪(DMA)对纤维的动态力学性能进行了研究,同时利用环境扫描电子显微镜(SEM)观察了纤维的表面和断面形貌.结果表明,HEMA引入大分子后,所得纤维对有机液体甲苯、三氯乙烯具有吸附功能,且吸附过程符合sigmoidal模型中的Hill方程;随HEMA质量分数的增加,纤维对甲苯和三氯乙烯的饱和吸附量增大,对甲苯和三氯乙烯的最大吸附量分别可达10g/g和21g/g;随HEMA质量分数的增加,纤维剩余率增加的同时,使纤维对甲苯和三氯乙烯的握持能力增强;HEMA质量分数对纤维动态力学性能有突出影响,特别是链段运动受其影响更为明显;HEMA质量分数对纤维表面和断面形貌均有显著影响,特别是当HEMA质量分数为15wt%时,所得纤维表面出现了许多空洞,其断面存在许多尺寸不均的空洞.     

磁电弹性体中螺型位错与唇口裂纹的相互作用

研究磁电弹性体中螺型位错与唇口裂纹的相互作用。结合Muskhelishvili方法和干扰技术, 在假定裂纹面具有不可渗透条件下得到磁电弹性体中由位错和唇口裂纹所诱导的应力场、电场和磁场的解析解。应用广义Peach-Koehler公式,得到作用在位错上的影像力。通过数值算例,得到场强度因子的变化规律及影像力和广义力随位错位置的变化规律。     

INVESTIGATION ON KANE DYNAMIC EQUATIONS BASED ON SCREW THEORY FOR OPEN-CHAIN MANIPULATORS

IntroductionDynamicsofroboticmanipulatorsisthebasisofdynamiccontrolandmechanicaldesignofroboticmanipulators.Dynamicanalysisofrobotscanemploytheapproachesoftheoreticalmechanicsanddynamicequationsofanalyticalmechanics,suchasNewton_Eulerdynamicequations,Lagrange_Eulerdynamicequations ,Routhequation ,Appellequation ,andKaneequations.Theultimateresultsarethesamewhenweinvestigateononekindofmotionsaboutoneobjectivebydifferentdynamicequations,butthespeedandquantitiesofcomputationoftheseequationsare…