适用于有限元分析的非线性弹性壳体理论

本文从连续介质力学出发导出了计及横剪效应的非线性弹性壳体理论。这个理论适合于有限元列式,可用于壳体的几何非线性和后屈曲分析。     

Ductile crack initiation behavior in steels with compressive prestrain

It is well known that compressive prestrain reduces ductility in steels. On the other hand, it has also been found that high stress triaxiality reduces equivalent plastic strain at the onset of ductile fracture. In this research, plate specimens and notched bar specimens, which were prestrained in compression with bending, were used in reversed bending tests, and the effect of compressive prestrain on ductile crack initiation in steels was investigated. It was found that small ductile cracks occurred from the microscopic wrinkles which were formed on the concave surface with compressive prestrain. The critical relationship between stress triaxiality and equivalent plastic strain at ductile crack initiation was investigated by finite-element analysis. It was found that ductile crack initiation in steels with compressive prestrain can be estimated qualitatively by the relationship between stress triaxiality and equivalent plastic strain.     

光纤光栅传感器在钢桥面铺装长期监测中的应用

钢桥面板在车辆荷载作用下,容易产生较大的局部变形。国内对于桥面铺装应力应变分析多采用有限元,实桥长期监测仍然处于空白阶段。该文依托桃浦路蕴藻浜大桥项目,对实桥监测过程中的传感器布设进行了研究。从不同结构、不同用途传感器选取方面入手,对传感器的埋设方案,安装方法进行详细介绍,为以后工程中传感器使用提供了借鉴。     

运用弹性理论研究有限长圆柱壳声辐射的一个通用方法(英文)

A general method was proposed to study the sound and vibration of a finite cylindrical shell with elastic theory.This method was developed through comprehensive analysis of the uncoupled Helmholtz equation obtained by the decomposition of elastic equations and the structure of the solution of a finite cylindrical shell analyzed by thin shell theory.The proposed method is theoretically suitable for arbitrary thickness of the shell and any frequency.Also,the results obtained through the method can be used to determine the range of application of the thin shell theory.Furthermore,the proposed method can deal with the problems limited by the thin shell theory.Additionally,the method can be suitable for several types of complex cylindrical shell such as the ring-stiffened cylindrical shell,damped cylindrical shell,and double cylindrical shell.     

二维矩形弹性液舱内液体晃荡数值模拟研究

阐述ADINA数学模型及相关数值方法,以二维矩形刚性液舱模型为例模拟液体晃荡,将所得的结果与解析解进行比较,验证该模型的有效性;通过数值模拟,研究二维矩形弹性液舱内的液体晃荡,分析不同刚度、不同频率对液体晃荡自由液面波高运动的影响。     

桩基低应变检测波型分析及桩身完整性判别

根据桩基体系中桩顶、桩身、桩端等各部位反射波的特征,分析产生离析、夹泥、缩径、断裂、扩径差异等缺陷的原因,探讨各类型缺陷的处理措施,建立同相反射波和反相反射波的判别标准。通过对大量现场检测资料的分析,验证判别标准的合理性和适用性,该方法对提高桩身完整性判别检测的精度有较大帮助。     

船体分段焊接变形仿真

船体分段在焊接过程中产生的焊接变形会使船体结构强度降低,然而精确预测和控制焊接变形是个难题.文章提供了准确预测焊接变形的固有应变等效载荷法.这种方法运用有限元法结合固有应变理论以及实验结果对焊接变形进行分析:引入简化的弹-塑性分析杆-弹簧模型,通过分析得到固有应变受焊接区域约束度及最高温度分布情况的影响;将固有应变转化为等效载荷,应用弹性有限元分析求得整个结构的焊接变形.计算结果与LEECH计算及实验结果吻合较好.     

Flexible riser-bend stiffener top connection analytical model with I-tube

The flexible riser top connection to the floating unit is a critical region considering extreme loading and fatigue lifetime assessment and is generally protected by a bend stiffener to limit the curvature in this region. The top connection usually interface the floating unit with two main configurations: i) end-fitting and bend stiffener directly connected to a riser balcony or ii) riser connected to the floating unit in the end of an I-tube, which reduces the end-fitting bending loading, and bend stiffener assembled to a bellmouth with a given inclination in relation to the I-tube longitudinal axis. The traditional modeling approach considers the riser/bend stiffener system attached to the floating unit, representative of the first configuration. A more realistic modeling approach, capturing the complex interactions of flexible riser/bend stiffener with I-tube interface can be employed for preliminary assessment with less conservatism. In this work, a large deflection analytical beam model is developed for the riser top connection with I-tube considering the bellmouth transition region with a straight rigid surface followed by a curved section. The riser follows a nonlinear bending behavior described by a bilinear moment vs curvature function and the bend stiffener polyurethane material exhibits nonlinear elastic symmetric response represented by a power law function. It is assumed that there is no gap between the riser and the bend stiffener and the riser is fixed in the end-fitting position. The mathematical formulation of the statically indeterminate system results in three systems of coupled differential equations combined with the corresponding multipoint boundary conditions to be numerically solved by an iterative procedure. A case study is carried out with a 7” flexible riser protected by a bend stiffener connected to an inclined I-tube bellmouth. The system is subjected to extreme loading conditions and the influence of the sleeve shape and I-tube length on the riser curvature distribution, including the end-fitting position, and contact forces between the riser/sleeve and riser/bend stiffener sections are assessed.     

高温高压消毒对五种桩挠曲强度与弹性模量的影响

目的研究高温高压消毒对不同桩挠曲强度与弹性模量的影响。方法采用北京实德隆碳纤维桩、玻璃纤维桩、石英纤维桩、Tenax玻璃纤维桩、Anthogyr钛桩各12支,分别分为实验组和对照组,每组6支。实验组经MelagVacuklav 24B消毒仪134℃高温、2.2 MPa高压消毒50 min,对照组不进行消毒。采用三点加荷系统测定其弹性模量和挠曲强度,并对其差异进行统计分析。结果两组内的实德隆碳纤维桩、玻璃纤维桩、石英纤维桩、Tenax玻璃纤维桩的弹性模量值与挠曲强度值彼此间无统计差异(P>0.05),Anthogyr钛桩获得了最高的弹性模量值与挠曲强度值(P<0.05);两组间经配对t检验无统计学差异(P>0.05)。结论纤维桩具有满足临床使用的挠曲强度,而其弹性模量显著低于金属桩,可以缓冲载荷,保护牙体组织,防止根折,成为桩材料发展方向。高温、高压消毒对纤维桩和钛桩的弹性模量和挠曲强度无显著影响,可用于桩的临床消毒。     

人湿尺骨干在冲击压缩实验下的力学性能及规律

目的探讨人湿尺骨密质骨在高应变率下的力学性能及其分布规律。方法用分离式Hopkinson压杆(SHPB)技术对人湿尺骨密质骨进行了应变率在.ε=1.2×103/s条件下的冲击压缩试验。结果尺骨密质骨在高应变率下的力学性能随其纵向位置变化而呈现出中间强两端弱的分布,最强的位置约在距近端1/3处,且近端强于远端。与静态结果的比较表明,尺骨密质骨对应变率有较大的依赖性。结论在冲击压缩力作用下,尺骨的两端,尤其是远端容易骨折。