Elastodynamic stress intensity factor due to three-dimensional concentrated transient loading on the faces of a crack

The dynamic stress intensity factor for a semi-infinite crack in an otherwise unbounded elastic body is analyzed The crack is subjected to a pair of suddenly applied point loads on its faces at a distance l away from the crack tip The solution of the problem is obtained by superposition of the solutions of two simpler problems. The first of these problems is Lamb' s problem, while the second problem considers a half space with its surface subjected to the negative of the normal displacement induced by Lamb's problem in the range x>0. The latter is solved by means of integral transforms together with the application of Weiner-Hopf technique and Cagniard-de Hoop method. An exact expression is derived for the mode I stress intensity factor as a function of time for any point along the crack edge. Some features of the solution are discussed.

Elastodynamic Stress Intensity Factor History for a Semi-infinite Crack Under Three-dimensional Transient Loading

The dynamic stress intensity factor history for a semi-infinite crack in an otherwise unbounded elastic body is analyzed. The crack is subjected to a pair of suddenly-applied point loadings on its faces at a distance L away from the crack tip. The exact expression for the mode I stress intensity factor as a function of time is obtained. The method of solution is based on the direct application of integral transforms, the Wiener-Hopf technique and the Cagniard-de Hoop method. Due to the existence of the characteristic length in loading, this problem was long believed a knotty problem. Some features of the solutions are discussed and graphical result for numerical computation is presented.

爪极发电机负载漏磁计算

采用三维瞬态有限元方法对一台电励磁爪极发电机和一台混合励磁爪极发电机进行了负载漏磁计算。爪极发电机的特殊爪极结构决定了电机磁场呈三维分布,需要用三维数值方法计算。首先对永磁体进行了优化分析,确定了永磁体牌号和三维尺寸。接着分析了两种电机的气隙磁密波形。然后得到了在输出恒压的前提下两种电机不同转速和不同励磁电流下的负载平均漏磁系数以及最大输出功率。并且得出了两种电机效率与负载平均漏磁系数的变化关系。最后,计算值与样机实测值的一致性验证了计算结果的有效性。

横观各向同性体三维裂纹的瞬态扩展

讨论一对集中力作用下横观各向同性体三维裂纹的瞬态扩展问题,其解答构成三维裂纹瞬态扩展问题的基本解。求解方法是基于积分变换技术,将混合边值问题化为Wiener-Hopf型积分方程,求得了裂纹所在平面应力和位移的封闭形式解。进一步利用Abel定理和Cagniard-de Hoop方法,求得了动态应力强度因子的精确解。最后通过数值结果揭示了横观各向同性材料三维扩展裂纹尖端场的动态特性。

综合物勘方法在煤矿隐蔽致灾地质因素探查中的应用研究

为了精准查明桑树坪煤矿北二采区范围内各类隐蔽致灾地质因素,依据三维地震勘探和瞬变电磁综合物探方法的探查成果,对研究区的地质异常体进行了全面分析和评价,为北二采区未来采掘范围内的安全生产提供了依据。查明了北二采区3号煤层构造形态,新发现挠曲11个,解译断层16条;查明了区内2处3煤层开采的采空区边界及其影响区;查明了北二采区3号煤层顶底板含水层的富水情况,并解译了5处富水区;解译了奥灰含水层的起伏形态和富水性;解译了2处层滑构造。

坡面沉桩边坡动态稳定性三维极限上限分析

采用极限分析上限法,建立土质边坡坡面沉桩动态稳定性三维计算模型,研究沉桩力、桩土间横向力等对边坡动态稳定性的影响。通过算例计算,对整个沉桩过程中边坡抗滑稳定安全系数的变化规律及其内在机制进行深入研究,并分析桩径、沉桩位置、坡角对边坡抗滑稳定安全系数的影响规律。结果表明:沉桩力对边坡稳定性产生不利影响,导致沉桩前期边坡安全系数持续降低;桩体穿过破坏面后,边坡安全系数由于桩身的抗滑作用而显著提高。桩径越大,沉桩前期安全系数越低,其下降速度也越快,但桩体穿过破坏面后安全系数提升也越明显;沉桩位置越靠近坡顶,沉桩过程中安全系数下降速度越快,导致最危险点的安全系数越低;坡角越大,沉桩过程中整体安全系数越低。分析结果对于坡面沉桩的稳定性评估及设计施工具有一定参考价值。