Strain Rate Sensitivity of Porous Cotton-Phenolic Bearing Retainer

In order to study the strain rate sensitivity of porous cotton cloth-phenolic bearing retainer, the hardness and elastic modulus of the porous cotton cloth-phenolic bearing retainer were measured by nanoindenter when the strain rate ranged from 0.01 s⁻¹ to 0.05 s⁻¹. And then the viscoelastic properties of the materials were analyzed by Kelvin-Voigt model. The strain hardening effect and strain local softening effect of the material under different strain rates were studied. The results show that with the increase of strain rate, the hardness and elastic modulus of porous cotton cloth-phenolic material first increase and then decrease. When the strain rate increases from 0.01 s⁻¹ to 0.05 s⁻¹, the increase of hardness and elastic modulus of porous cotton cloth-phenolic material is related to the strain hardening phenomenon of the material. When the strain rate increases from 0.05 s⁻¹ to 0.30 s⁻¹, the creep displacement increases significantly, the contact stiffness decreases rapidly, the deformation is consumed in the contact interface between the indenter and the material in the form of heat, the material in the contact area of the indenter changes from viscoelasticity to viscosity, the local material viscosity decreases, and the hardness and elastic modulus decrease rapidly. The change of hardness and elastic modulus of porous cotton cloth-phenolic aldehyde with strain rate is the result of the competition between strain hardening effect and strain local softening effect.