| PTFE has been widely used in chemical, petroleum and papermaking fields. However the resistance to deformation is poor. PTFE/bronze improves the friction property, thermal conductivity, tensile strength and compressive strength of PTFE. So the creep and ratcheting of PTFE/bronze are deserve to study.In this paper, PTFE/bronze composite was prepared by the cold compaction and sintering processes. The proper compact pressure was determined through the tensile experiments. Many tensile, creep, ratcheting tests were conducted to study the effects of stress rate, time and temperature, etc. To comparison, the same tests were conducted on PTFE/bronze and pure PTFE. And the results showed that the addition of bronze can improve the resistances of creep and ratcheting. PTFE/bronze also kept a low level ratcheting strain even at high temperature. Creep strain increased with the stress level and time increasing. The eternal deformation which could not disappear during recovery time was large. The ratcheting strain increased with stress level and temperature increasing. And the longer peak stress holding time improved the ratcheting strain accumulation rate. Ratcheting strain stage-grew when creep was in the ratcheting test. PTFE/bronze was enhanced by pre-tension. The resistance of ratcheting was improved by pre-tension, but recovery decreased this enhancement. SEM was used to analysis PTFE/bronze’s micro-structure of un-deformation and fracture failure. The deformation of PTFE/bronze was explained from the microcosmic view.The Schapery model and Xia-Ellyin model were applied to predict creep tests. The stress-strain curves predicted by Schapery model and Xia-Ellyin model did not match well with the test results. In order to improve the prediction accuracy, Xia-Ellyin model was modified. The load-unload stress vs. strain relationship predicted by modified Xia-Ellyin model coincide well with the test result. Modified Xia-Ellyin model could reflect the viscidity of PTFE/bronze well. |
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