Experimental Study On The Cyclic Plasticity Of Pipe PE100

Due to their good resistance to impact, stress-cracking, corrosion, and the advantagesof energy saving and health, PE pipe have been widely used in water supply and drainageand town gas distribution field. Research on the mechanical behavior and cyclicdeformation behavior of PE pipe is one of the basic jobs to improve the reliability of thematerials and reduce accident.The cyclic strain test under symmetry torsion and uniaxial ratcheting test were carriedout for pipe PE100at room temperature. The uniaxial test, multiaxial strain and ratchetingexperiments were carried out at RT and40℃.The uniaxial tests focused on the stress-strainresponse under different strain rates and the effects of cyclic strain amplitude, mean stress,stress amplitude stress rate, loading history and holding time of peak stress on cyclic plasticstrain. While the multiaxial tests aimed on the influence of temperature and loading path onthe cyclic plastic deformation of pipe PE100.The uniaxial test results showed that, pipe PE100is a kind of rate-dependent andcyclic softening material. Softening level increased with the increase of strain amplitude.The former loading of cyclic load bigger than critical value can induce cyclic hardening forfollowing loading with smaller one, however such kind of hardening would vanish with aperiod of release time, which indicates recovery ageing effect of the material. Theratcheting strain is sensitive to the mean stress, amplitude stress, stress rate and loadinghistory.The multiaxial experimental results showed that the softening and hardeningproperties of material under multiaxial strain cyclic loading and axial ratcheting strainunder multiaxial ratcheting cyclic loading were associated with the loading path andtemperature. Multiaxial cyclic strain experiment indicated that the circular path causes themost non-proportional additional softening. While the multiaxial ratcheting cyclic loadingtest showed that ratcheting strain is related to axial load, shear strain amplitude, shear strainrate, and the former larger loading condition restrains the subsequent plastic strainaccumulation. Compared with the non-proportional path of linear and diamond, theratcheting strain caused by the circular path was the biggest. It was also founded that theelevation of temperature made the material soften and increase its ratcheting strain.