ETFE气枕曲面粘塑性成形方法研究

The viscoplastic forming method of ETFE cushion differs from the traditional cutting and welding method in fabrication of membrance structures. It takes full advantages of the unrecoverable deformation of ETFE foil to form the design surface. It not only decreases the cutting and welding processes, but also saves ETFE material. But this method is short of theoretical basis and reasonable analysis, on which does this project focus. This project would take numerous tensile tests on ETFE foil under high stress levels. The mechanical property of ETFE foil after viscoplastic forming process and its viscoelastic-plastic modeling are studied. Then, key steps in the viscoplastic forming method are discussed with numerical simulation through nonlinear finite element method. The surface of ETFE cushion and some important parameters, such as air pressure and time in form finding process, are determined. Additionally, the load capability of ETFE cushion fabricated through the viscoplastic forming method is studied in different loading condition, especially taking account of the distribution of stress. Finally, the viscoplastic forming tests of three ETFE cushion models would be carried out to verify and optimize the key steps and parameters in the method. Also, snow load and wind load are simulated in the tests to study the load capability of ETFE cushions and to examine the results of numerical analysis.

ETFE气枕曲面粘塑性成形方法是一种区别于传统裁剪拼接的膜结构加工制作方法，它利用ETFE薄膜自身优异的粘塑性变形性能形成气枕曲面，大大简化了裁剪与焊接工艺，提高了材料利用率,然而该方法的系统研究还未展开。本项目首先对高应力下ETFE薄膜材料力学特性进行试验研究，得到经历粘塑性成形后的材料力学性能，并基于材性试验结果提出高应力下ETFE薄膜材料的粘弹塑性本构模型。提出ETFE气枕曲面粘塑性成形关键工艺以及成形过程非线性有限元分析方法，通过数值分析确定成形后气枕形状及应力分布，得到成形过程所需的内压值、加压时间等工艺参数。对成形后的气枕进行受载分析，特别考虑粘塑性成形气枕应力不均匀对结构承载力的影响。完成三种形状的气枕模型粘塑性成形试验，验证并优化粘塑性成形关键步骤及成形工艺参数，进行加载及充气加压试验检验成形气枕的承载能力。本项目为ETFE气枕曲面粘塑性成形方法的推广应用奠定理论基础。

ETFE 气枕曲面粘塑性成形方法利用 ETFE 薄膜自身优异的粘塑性变形性能形成气枕曲面，大大简化了传统气枕制作过程中的裁剪与焊接工艺，提高了材料利用率，然而该方法的系统研究还未展开。本项目首先进行不同温度不同拉伸速率下 ETFE 薄膜材料单轴力学特性试验研究、双轴拉伸试验、气泡试验以及不同应力下的ETFE薄膜材料的单双轴徐变试验研究，得到ETFE薄膜在不同条件下的材料力学性能，并基于材性试验结果提出 ETFE 薄膜材料的粘弹塑性本构模型和ETFE薄膜材料的单轴和双轴徐变模型。提出了 ETFE 气枕曲面粘塑性成形关键技术以及成形过程的非线性有限元分析方法，通过数值分析确定成形后气枕形状，得到成形过程所需的内压值、加压时间等参数。对成形后的气枕进行循环充泄气加载分析和堆载分析， 研究了粘塑性成形过程对气枕受力性能的影响，考察了与传统裁剪气枕结构性能的异同。完成圆形、三角形、直角梯形三种形状共十几个气枕模型的成形试验以及相应的成形后加载试验，验证并优化了成形参数。本项目的成果为 ETFE 气枕曲面粘塑性成形方法的推广与应用奠定了理论基础。