ETFE气枕力学性能试验研究及有限元分析

Experimental research and finite element analysis on mechanical performance of ETFE cushions

对1个乙烯-四氟乙烯共聚物(ETFE)气枕足尺模型进行形态测试、加载测试及自振测试,研究了气枕的静力性能和动力特性。建立了ETFE气枕有限元模型,进行了形态、荷载及模态分析,验证了有限元分析方法的有效性。结果表明:气枕内压对外荷载较为敏感,荷载作用下内压变化幅度随初始内压增加而非线性减小;作用于气枕中部或单侧的荷载较对称荷载会引起更大的变形和内压变化;相同荷载作用下,气枕变形随初始内压增加而非线性减小;在试验内压范围内,测试气枕的基本自振频率位于6~10 Hz之间,前两阶自振频率间隔较大,2~5阶自振频率分布更为密集,气枕各阶频率均随初始内压升高而非线性增加;在低阶模态中,气枕上、下层膜面呈对称振动;ETFE气枕为低阻尼结构,各阶模态阻尼比随初始内压增加而减小;形态、荷载及模态分析的有限元结果均与试验结果吻合良好,验证了共同作用有限元模型在ETFE气枕静、动力分析中的准确性和适用性。

The static and dynamic characteristics of a full-scale ETFE cushion were studied on the basis of form-state test,loading test,and free vibration test. The interaction model of ETFE cushion was established and form-state analysis,loading analysis,and modal analysis were performed in order to verify the validity of finite element method.Results show that the internal pressure of ETFE cushion is sensitive to external loads. The variation amplitude of internal pressure decreases nonlinearly with the initial pressure increasing. The loads on the middle or side part of ETFE cushion will cause larger changes of membrane shape and internal pressure. Under the same load, the deformation of cushion also decreases nonlinearly with initial pressure increasing. In the range of common internal pressure,the first frequency of the test cushion locates between 6 Hz and 10 Hz. The interval of the first two frequencies is larger,and the second to fifth frequencies are more concentrated. The natural frequencies of cushion increase nonlinearly with the increase of internal pressure. The two-layer membranes show symmetrical vibration in lower-order modes. The ETFE cushion is a low damping structure,and the damping ratio of each mode declines with internal pressure increasing. The finite element results of form-state analysis,loading analysis,and modal analysis are in good agreement with the test results. It is verified that the interaction finite element model has good accuracy and applicability in static and dynamic analysis of ETFE cushions.