Different phenomenological equations based on plasticity, primary creep （as a viscoplastic mechanism）, secondary creep （as another viscoplastic mechanism） and different combinations of these equations are presente...Different phenomenological equations based on plasticity, primary creep （as a viscoplastic mechanism）, secondary creep （as another viscoplastic mechanism） and different combinations of these equations are presented and used to describe the material inelastic deformation in uniaxial test. Agreement of the models with experimental results and with the theoretical concepts and physical realities is the criterion of choosing the most appropriate formulation for uniaxial test. A model is thus proposed in which plastic deformation, primary creep and secondary creep contribute to the inelastic deformation. However, it is believed that the hardening parameter is composed of plastic and primary creep parts. Accordingly, the axial plastic strain in a uniaxial test may no longer be considered as the hardening parameter. Therefore, a proportionality concept is proposed to calculate the plastic contribution of deformation.展开更多
The electric field required for stable propagation of a positive streamer along an ice surface was investigated by measuring the currents associated with the streamer discharge.The influence of the surface properties,...The electric field required for stable propagation of a positive streamer along an ice surface was investigated by measuring the currents associated with the streamer discharge.The influence of the surface properties,namely the existence of a water film on the ice surface and surface contamination,was analyzed.Results showed that in the presence of an ice surface,except in case of low conductive surface,streamers propagate stably with an external field lower than that generally measured for propagation in air alone(approximately 5 kV/cm).For higher contamination levels,the stability field was found to be slightly influenced by the temperature,while for lower contamination levels,it decreased significantly with an increase in temperature.展开更多
文摘Different phenomenological equations based on plasticity, primary creep （as a viscoplastic mechanism）, secondary creep （as another viscoplastic mechanism） and different combinations of these equations are presented and used to describe the material inelastic deformation in uniaxial test. Agreement of the models with experimental results and with the theoretical concepts and physical realities is the criterion of choosing the most appropriate formulation for uniaxial test. A model is thus proposed in which plastic deformation, primary creep and secondary creep contribute to the inelastic deformation. However, it is believed that the hardening parameter is composed of plastic and primary creep parts. Accordingly, the axial plastic strain in a uniaxial test may no longer be considered as the hardening parameter. Therefore, a proportionality concept is proposed to calculate the plastic contribution of deformation.
文摘The electric field required for stable propagation of a positive streamer along an ice surface was investigated by measuring the currents associated with the streamer discharge.The influence of the surface properties,namely the existence of a water film on the ice surface and surface contamination,was analyzed.Results showed that in the presence of an ice surface,except in case of low conductive surface,streamers propagate stably with an external field lower than that generally measured for propagation in air alone(approximately 5 kV/cm).For higher contamination levels,the stability field was found to be slightly influenced by the temperature,while for lower contamination levels,it decreased significantly with an increase in temperature.
