羊毛纤维对称重复扭转疲劳性能的研究OA

To further optimize the processing technology of wool fibers and the use performance of their products,the mechanical properties and damage mechanism of wool fibers under repeated torsional fatigue loading were investigated.Firstly,uniaxial tensile tests were conducted to determine the elastic limit(0.44 cN/dtex)and fracture strength(0.61 cN/dtex)of wool fibers,confirming that pretension should be controlled within the elastic range to avoid fiber damage.Secondly,based on the unidirectional torsion test,it was found that the increase in pre-tension caused the maximum twist angle to decrease from 38.2° to 33.6°.Accordingly,the twist angle for the symmetric repeated torsion fatigue test was set at 5°～30°.Further,symmetric repeated torsional fatigue tests showed that the data dispersion was minimized when pre-tension was 0.2 cN/dtex and twist angle was 20° or 25°,which can be used as stable test conditions.The relationship between fatigue life and twist angle was fitted using exponential model,and the results showed that │r│>0.95,indicating high reliability of the model,fatigue life was decreased exponentially with increasing twist angle.Scanning electron microscopy(SEM)analysis revealed that fatigue damage initiated from surface microcracks,which gradually propagated into the fiber interior with increasing cycles.The final fracture surface exhibited parallel bundle splitting and helical morphology,revealing failure mechanism dominated by torsional cumulative damage.The key parameters and damage evolution law of torsional fatigue in wool fibers were clarified,which providing a theoretical and experimental basis for their durability evaluation.