A finite element model for unbonded flexible pipe under combined axisymmetric and bending loads

Flexible pipes are key equipment for offshore oil and gas production systems, conveying fluids between the platform and subsea wells. The structural arrangement of unbonded flexible pipes is quite complex, encompassing several layers with polymeric, metallic and textile materials. Different topologies and a large amount of intricate nonlinear contact interactions between and within their components, especially because of the relative stick-slip mechanism during bending, makes numerical analysis challenging. This paper presents an alternative three-dimensional nonlinear finite element model that describes the response of flexible pipes subjected to combined axisymmetric and bending loads. To simulate the response of a flexible pipe under axial tension or compression combined with uniform curvature, an equivalent thermal loading is employed on the external sheath, which is modelled as an orthotropic thermal expansion material with temperature-independent mechanical properties. To assess the feasibility of the proposed model, the bending moment versus curvature of the finite element solution is compared with experimental results obtained in literature and good agreements are found between them. Detailed finite element results such as contact pressures, armour wire slip displacements and friction, normal and transverse bending stresses are also shown and compared with available analytical models.     

Strength evaluation of intersection between stiffeners and primary supporting members in double hull structure

In this previous study, a consistent theoretical formula was established in single hull structure, taking account of all the structural components affecting the load share of each member, in combination with the combined load effect of direct force from the longitudinal stiffener and shear force on the primary supporting member. What's more, it has been known qualitatively that the bending moment at the root of the web stiffener in double hull structure is less than that in single hull structure. However, the difference between double hull and single hull structures has not been achieved. In this study, the authors develop a theoretical formulation to represent the stresses at the root of the web stiffener due to the load from both the longitudinal stiffener and the shear force on the primary supporting member in the double hull structure. Then, the results calculated by the derived formulae are compared with the results obtained by finite element analysis, and good accuracy of the proposed formula was verified. Finally, the calculated stresses were compared between double hull and single hull structures. On one hand, the share of loading born by the web stiffener is almost comparable between the double hull and single hull structures. On the other hand, the bending moment at the root of the web stiffener is smaller in the double hull structure than in single hull structure, and therefore, the maximum stress is smaller.     

地震工况下铁路路基边坡极限状态法设计研究

当前铁路路基设计理论正处于容许应力法向极限状态法转轨中,《铁路路基极限状态法设计暂行规范》(Q/CR9127—2015)针对路基边坡稳定性,仅提出了持久设计工况下的边坡稳定性的极限状态设计表达式及其分项系数,而对地震设计工况下规范没有给出相应的内容。在考虑地震力的条件下,提出地震设计工况下路基边坡稳定性分析公式,引入地震作用效应及其分项系数,通过对地震设计工况下路基边坡极限状态法与容许应力法对比分析,得出地震工况下路堤和路堑边坡各自的极限状态法分项系数优化幅度,为相应规范的修编提供参考。     

从设计、工艺上解决摩托车后减振弹簧的弯曲变形

减震器弹簧的疲劳强度受材料表面的裂纹、疵点、伤痕及腐蚀介质、工作温度等影响很大,弹簧疲劳强度偏低不能满足弹簧最大工作负荷下疲劳强度的要求,会造成减震器弹簧弯曲、变形,甚至断裂。     

宁高城际轨道交通线路技术标准研究

宁高城际高淳段作为江苏沿江城市群轨道交通网中的一条重要线路,联系了南京市主城区、东山副城、溧水区石湫镇和高淳区,承担南京市主城区与高淳区间的远距离轨道交通。前期系统制式专题研究确定,本线的速度目标值为120km/h,车辆选用B型车4辆编组。但我国尚无与之相应的轨道交通线路设计规范,因此实际设计中需要参照地铁或国铁相关规范。而本线线路的平、纵面设计参数与地铁和国铁均有较大差异,不能完全参考《地铁设计规范》或《铁路线路设计规范》,因此必须对本线的关键技术参数进行专题研究,根据本线的功能定位和特点选取合适的技术标准,计算出关键技术参数应用于工程设计。     

电气化铁路接触网用棒形瓷绝缘子断裂分析

接触网用棒形瓷绝缘子作为接触网系统的关键零部件,其质量的好坏直接关系到接触网的可靠性,从而影响正常的行车安全。以瓷件的气孔、裂纹等缺陷为载体,通过数学模型对棒形瓷绝缘子的断裂机理进行分析,再通过弯曲强度试验对接触网用棒形绝缘子断裂原因及断裂后的断面进行探讨。分析结果表明:棒形瓷绝缘子断裂位置的一致性较高,且不同种类的缺陷可以通过断裂后的断面来推断。最后,给出提高绝缘子强度的控制措施。     

电气化铁道用铜及铜合金接触线反复弯曲试验方法的研究

在弯曲半径和工装夹具相同的条件下，对不同规格、不同种类国产接触线，在不同速度下进行反复弯曲试验，研究弯曲速度对接触线试验结果的影响。     

冷再生疲劳预估模型的研究

以梁式试件三分点加载弯曲疲劳试验得到的疲劳方程为基础,将材料的容许拉应力引入方程,代替原方程中的参数应力比S,建立σR-logN方程。并通过此疲劳方程对冷再生基层混合料的疲劳性能简要分析。     

车身薄壁梁结构刚度特性的仿真研究

将车身薄壁梁截面参数对其弯曲刚度和扭转刚度的影响进行定量分析和性能优化意义重大.以车身薄壁梁的刚度质量系数SME作为评价指标,通过对典型闭口和开口截面梁的分析,得到了薄壁梁截面参数与SME的解析表达式.利用HyperMesh软件进行有限元仿真计算,对定量化表述的理论公式进行了验证,并提出基于刚度特性优化的薄壁梁截面设计...     

硅粉HBSPC性能研究

针对我国重型货车急剧上升的特点,公路建设中的高性能混凝土路面日益得到重视和应用.其中硅粉对提高HBSPC混凝土路面强度和耐久性具有优异的作用.为了比较不同硅粉对HBSPC性能的影响,选取了两种硅粉进行对比,就硅粉HBSPC的几项主要性能作了分析,以促进其广泛应用.