低速侧向撞击下充压管道的动力响应与失效机理研究

Pipelines are used throughout industry to convey gases and liquids often under high pressures over long distance between pressure vessels and other industrial plant. These pipelines are often situated in potentially dangerous environments so that safety calculations are required by various bodies to assess the hazards associated with the accidental release of any contents. The study on the potentially dangerous environments and the better understanding of the dynamic response mode and failure mechanism are vital for the continue development of the impact resistant design guidelines for the pressurized pipelines..The project involves experimental investigations, development and calibration of numerical models and analytical approaches, and analytical parametric studies. Firstly, the systematical experimental investigations will be conducted as the focus on the influence of the impact position and oblique impact. The relationship between the impact parameters and the dynamic response mode will be investigated by measuring the transient response of variables such as deformation and internal pressure. Secondly, analytical models will be developed and calibrated to model the measured fundamental behavior of the specimens, and be used further to conduct parametric studies. The dynamic response model and failure mechanism will be evaluated and summarized according to the given impact case based on the investigation of force, deformation and energy. Finally, the simplified beam model will be specified developed for the high-pressurized pipeline in view of its global deformation characteristic. This model will incorporate the forces generated by the internal medium which follows the pipeline large deformation and generates the inertia and centrifugal accelerations..The project will facilitate: (1) better prediction of the performance and failure mechanism of pipelines subjected to low-velocity impact events, and (2) the development of impact-safety provisions to protect public property and life.

偶然事件造成的撞击加载通常会造成充压管道失效，从而引起灾难性后果。管道抗撞技术的进一步发展迫切需要对其可能承受的复杂撞击工况以及具有普遍代表意义的响应模式进行深入研究。本项目拟采用系统试验、数值模拟、理论推导手段针对充压管道低速撞击行为开展研究。首先，针对撞击角度、位置发生改变的工况进行系统试验，通过解析管道变形、内压等变量的瞬态发展过程，探明撞击参数与响应模式之间的连接关系和相互作用机理。然后，基于试验数据和有限元参数分析，总结、归纳管道在撞击过程中内力、变形、能量等参数的分布特征和演变规律，揭示对应不同撞击工况的管道响应模式和失效机理。最后，针对高压管道整体变形特点，基于大变形动力学控制方程，发展考虑液固耦合效应并适用于管道分析的简化梁模型计算方法。本项目的研究成果将为全面、清晰的认识充压管道撞击行为提供试验和理论依据，同时也将为建立高效的管道安全性设计、评价理论提供新思路。

本课题立足低速撞击（小于15m/s）,通过动、静力实验、三维有限元模拟和理论推导系统研究了充压管道冲击动力行为和失效机理。.管道正向撞击实验考察因素涵盖介质类型、充压水平、撞击体形状、撞击位置，首次清楚揭示了介质质量和充压水平共同主导管道动力行为的机理，并明确对于低速撞击问题，相比介质质量，充压水平起首要主导作用。跨中和1/4跨处发生撞击将引起管道首先在撞击区产生局部变形，随之管段发生整体弯曲变形，因塑性耗能区域增大导致失效能量提高；根部位置承受撞击将引起管道脆性剪切破坏，其对应失效能量最小。内充压力介质因可有效阻止撞击区域局部变形开展，导致管道整体变形比份增大，促使失效模式由撞击区域向管道根部转移。内压的升高较小程度上影响管道最终塑性变形，却显著改变局部变形与整体变形比值，从而导致管道失效能量的极大降低。刀形撞击体因与管道接触面积较半圆形和楔形小，塑性耗能区域过于集中从而导致失效能量最小。.斜向撞击下，管道将经历撞击瞬时局部变形，随之撞击体与管道摩擦滑移以及全管段整体弯曲变形耦合过程。摩擦滑移的存在将导致管道截面扁平化范围较正向撞击局部变形区域加大，从而产生更大的塑性耗能能力，导致管道失效能量高于正向撞击工况。内充压力介质的存在将显著降低撞击体与管道的摩擦滑移距离，导致失效能量降低。.选用水、空气和干沙为内充介质进行的四点弯曲实验表明，薄壁管道将在加载前期经历截面扁平化，后期在某个截面集中发展塑性，形成“结节”，整体弯曲行为呈现明显的前期弹性-中期塑性强化-后期软化特点。内充介质和压力水平可以显著提高管道的临界曲率和弯矩，其提升程度取决于介质性质和压力水平。.基于ABAQUS程序，应用其自带的Surface based Fluid Cavity功能模拟管道内充介质和压力水准，可以实现对充压管道动力响应行为的精细模拟。基于管道变形后构型，并考虑内压和介质质量影响，采用实验测量的弯矩-曲率关系描述管道弯曲行为，本课题推导了基于线元的管道大变形运动方程，实现了应用简单梁单元进行充压管道动力行为的模拟。.本项目所开展的实验研究成果清晰、明确地回答了诸如介质压力，撞击形状、位置、角度等因素影响充压管道冲击动力行为的机理；基于有限元软件的数值模拟为高效分析管道响应提供了行之有效的路径；理论推导的基于梁单元的分析方法为建立简化、可靠的管道安全性设计、评价理论提供了新思路。