【作者】 张超；

【导师】 陈旭；

【作者基本信息】 天津大学 ， 化工过程机械， 2020， 硕士

【摘要】 质子交换膜燃料电池广泛应用于燃料电池汽车等新能源发电装置当中,质子交换膜是质子交换膜燃料电池的重要元件,用于传导质子、隔绝燃料。质子交换膜在工作状态下受到装置框架的约束、环境温湿度的影响以及车辆启动、制动等过程的牵制,不可避免地遭受复杂循环载荷的作用。然而,现有对质子交换膜力学行为的研究集中于单轴条件下的拉伸、蠕变、应力松弛等性能,对其在单轴、双轴循环加载作用下的循环变形行为研究较少,对描述其单轴、双轴循环变形行为的本构模型研究更是屈指可数。因此,研究质子交换膜在循环加载作用下的力学行为并对其进行本构描述具有重要意义。本研究在室温下对质子交换膜进行了一系列单轴力学实验,包括单轴拉伸、多级加载-卸载恢复、蠕变恢复等基本力学实验,以及包含加载速率、应力幅值、平均应力、峰值应力保持时间等影响因素的棘轮变形实验。通过实验观察确定了质子交换膜是率相关粘弹-粘塑性材料,棘轮应变随加载速率的增大而减小,随应力幅值、平均应力、峰值保持时间的增大而增大。同时得到了材料性能参数,并由此提出了三维Schapery非线性粘弹性模型与Ohno-Abdel-Karim随动强化准则相结合的循环粘弹-粘塑性本构模型,用以描述质子交换膜在应力控制循环加载作用下的循环变形行为。经过实验数据与模拟结果的对比验证,发现本研究所提出的循环粘弹-粘塑性本构模型能够很好地描述质子交换膜在应力幅值、平均应力、加载速率等影响因素下的单轴棘轮变形行为,模拟棘轮应变趋势以及数值都与实验吻合得很好。为了验证模型的多轴适应性,对质子交换膜双轴多路径棘轮变形行为进行了模拟,发现该模型能够较好地描述质子交换膜在方形路径和比例路径下的双轴棘轮变形行为,模拟棘轮应变趋势以及数值都与实验大体相符。另外,为更好地描述质子交换膜的蠕变行为,在模型中叠加蠕变塑性部分,通过与单轴蠕变恢复以及参考的双轴蠕变恢复实验数据相对比,发现加入蠕变应变部分的塑性-蠕变本构模型能够更合理地描述材料的蠕变特性。更多还原

【Abstract】 Proton exchange membrane fuel cells are widely used in new energy power generation devices such as fuel cell vehicles.Proton exchange membranes are important components of proton exchange membrane fuel cells,which are used to conduct protons and prevent reactants from crossing.The proton exchange membranes are inevitably subjected to complex cyclic loads under operation conditions due to the constraints of the device frame,the influence of ambient temperature and humidity,and the restraint of vehicle startup and shutdown process.However,existing researches on the mechanical behavior of proton exchange membranes focus on tensile,creep,stress relaxation and other properties under uniaxial conditions,while the cyclic deformation behaviors under uniaxial and biaxial cyclic loading conditions are rarely studied.In addition,studies on constitutive models to describe the cyclic deformation behaviors under uniaxial and biaxial cyclic loading conditions are even more rare.Therefore,it is of great significance to study the mechanical behaviors of proton exchange membranes under cyclic loading conditions and to describe them using constitutive models.In this study,a series of uniaxial mechanical experiments are carried out on the proton exchange membrane at room temperature,including basic mechanical experiments such as uniaxial tension,multilevel loading-unloading recovery,and creep recovery,as well as ratcheting deformation experiments under different loading rates,stress amplitudes,mean stresses and peak stress holding times.Through experimental observation,it is confirmed that the proton exchange membrane is a kind of ratedependent viscoelastic-viscoplastic material.Ratcheting strain decreases with the increase of loading rate,while increases with the increase of stress amplitude,mean stress and peak stress holding time.At the same time,the material performance parameters are obtained,and a viscoelastic-viscoplastic constitutive model combining the three-dimensional Schapery nonlinear viscoelastic model and the Ohno-AbdelKarim nonlinear kinematic hardening rule is proposed to describe the deformation behaviors of the proton exchange membrane under stress controlled cyclic loading conditions.Through the comparison of experimental data and simulation results,it is found that the viscoelastic-viscoplastic constitutive model used in this study can describe the uniaxial ratcheting behaviors of the proton exchange membrane under the influence of loading rate,stress amplitude,and mean stress reasonably.The simulated ratcheting strain trend and values are in good agreement with the experiment.In order to verify the universality of the model,the biaxial multipath ratcheting deformation behaviors of the proton exchange membrane are simulated,and it is found that the model can well describe the biaxial ratcheting deformation behaviors of the proton exchange membrane under the square and proportional paths.The simulated ratcheting strain trend and values are roughly consistent with the experiments.In addition,in order to better describe the creep behavior of the proton exchange membrane,the creep plastic section was added to the model.Compared with uniaxial and biaxial creep-recovery experimental data,it is found that the creep plastic constitutive model can describe the creep characteristics of the material more reasonably.更多还原