Strain accumulation process under periodical loading in polymeric materials

摘要

Paper presents methodology for analyzing strain accumulation process in polymeric materials when exposed to periodical (cyclic) loading.Within each loading cycle material undergoes a combination of the creep and relaxation process.At certain conditions the retardation process between two loading cycles cannot be fully completed.Consequently strain starts to accumulate,which leads to hardening of the material and ultimately to the failure of polymeric product.Critical frequency of the applied periodic loading depends on the material retardation time (location of mechanical spectrum),while the magnitude of accumulated strain on the strength of corresponding discrete spectrum lines.So,the spectrum shape defines the intensity and the magnitude of accumulated strain.For certain type of material the accumulated strain will almost certainly lead to the failure of the product,while material with different time-dependent characteristics will not experience the critical limit of accumulated strain that would cause failure.Thus,the mechanical spectrum of polymeric material is the most important function for predicting durability of dynamically loaded polymeric products.We present mathematical methodology for predicting durability of such periodically loaded polymeric products,more specifically,for the case of the drive belts.The methodology includes numerical calculations of accumulated strain as a function of the number of loading cycles and function of loading angular velocity.Based on these calculations we can determine the critical angular velocity area of periodic loading where the strain accumulation is the most intensive,and may lead to material failure.