Based on the Brinson constitutive model of SMA, a piecewise linear model for the hysteresis loop of pseudo-elasticity is proposed and applied in the analysis of responses of an SMA-spring-mass system under initial vel...Based on the Brinson constitutive model of SMA, a piecewise linear model for the hysteresis loop of pseudo-elasticity is proposed and applied in the analysis of responses of an SMA-spring-mass system under initial velocity activation. The histories of displacement and velocity of the mass, and the response of stress of SMA are calculated with Brinson’s model and the piecewise linear model. The difference of results of the two models is not significant. The calculation with piecewise-linear model needs no iteration and is highly efficient.展开更多
Shape memory alloy （SMA） materials possess completely superelasticity or pseudoelasticity above the austenite finish temperature and many unique mechanical, thermal, thermal-mechanical and electrical properties comp...Shape memory alloy （SMA） materials possess completely superelasticity or pseudoelasticity above the austenite finish temperature and many unique mechanical, thermal, thermal-mechanical and electrical properties compared with other conventional materials. Many studies have reported that the superelastic and hysteresis properties of the SMA materials can absorb energies coming from external excitations or sudden impacts. In addition, due to the special electrical properties of NiTi superelastic wires, they can also be used as strain-sensing element to monitor structural health conditions. Composite laminated specimens embedded with SMA wire sensors are fabricated and detailed testing system is designed such as multi-parameters measuring for impact and weak signal processing for SMA sensor. Low velocity impact test shows that SMA wire sensors embedded in fiber-reinforced plastic （FRP） laminate can be well used to monitor impact responses, such as the location of impact damage, impact degree, and strain distribution. Experimental results and theoretical predictions reveal almost the same. Comparing with other method, a simple, economic and reliable technique method monitoring important engineering structures on line is provided.展开更多
DCT(deep cryogenic treatment)is commonly used in industry to improve the wear resistance characteristics of steels,especially.However,there are just a few researches about the effects on non-ferrous metals.The purpose...DCT(deep cryogenic treatment)is commonly used in industry to improve the wear resistance characteristics of steels,especially.However,there are just a few researches about the effects on non-ferrous metals.The purpose of this work was to investigate how DCT affects the properties of Cu-14Al-4Ni alloy treated at different soak time and submitted to thermomechanical cycling.A comparative experimental analysis was performed of the thermal properties of alloys obtained on a vacuum furnace,treated by DCT and thermomechanically cyclized.The results indicates that thermomechanical cycling promoted the appearance and growth of the martensitic phaseγ'1,less ductile than the martensitic phaseβ'1,which together with the induced hardening produced an increase in transformation temperatures and microhardness.The higher the number of cycles,the greater these effects.The DCT promoted an increase in the intensity of the diffraction peaks corresponding to the phaseβ'1 and the maintenance of them during the thermomechanical cycling of the material,which indicates that the DCT stabilizes the martensitic phaseβ'1 and,consequently,caused a reduction and stabilization of the martensitic transformation temperatures and the microhardness,when compared to the untreated material.The longer the soaking time of DCT,the greater these effects.展开更多
基金National Natural Science Foundation ofChina(No.5 973 10 3 0 )
文摘Based on the Brinson constitutive model of SMA, a piecewise linear model for the hysteresis loop of pseudo-elasticity is proposed and applied in the analysis of responses of an SMA-spring-mass system under initial velocity activation. The histories of displacement and velocity of the mass, and the response of stress of SMA are calculated with Brinson’s model and the piecewise linear model. The difference of results of the two models is not significant. The calculation with piecewise-linear model needs no iteration and is highly efficient.
基金This project is supported by Provincial Natural Science Foundation of Jiangsu, China(No.BJ99034)Foundation of Nantong City Science and Technology Leader, China(No.2004033)
文摘Shape memory alloy （SMA） materials possess completely superelasticity or pseudoelasticity above the austenite finish temperature and many unique mechanical, thermal, thermal-mechanical and electrical properties compared with other conventional materials. Many studies have reported that the superelastic and hysteresis properties of the SMA materials can absorb energies coming from external excitations or sudden impacts. In addition, due to the special electrical properties of NiTi superelastic wires, they can also be used as strain-sensing element to monitor structural health conditions. Composite laminated specimens embedded with SMA wire sensors are fabricated and detailed testing system is designed such as multi-parameters measuring for impact and weak signal processing for SMA sensor. Low velocity impact test shows that SMA wire sensors embedded in fiber-reinforced plastic （FRP） laminate can be well used to monitor impact responses, such as the location of impact damage, impact degree, and strain distribution. Experimental results and theoretical predictions reveal almost the same. Comparing with other method, a simple, economic and reliable technique method monitoring important engineering structures on line is provided.
文摘DCT(deep cryogenic treatment)is commonly used in industry to improve the wear resistance characteristics of steels,especially.However,there are just a few researches about the effects on non-ferrous metals.The purpose of this work was to investigate how DCT affects the properties of Cu-14Al-4Ni alloy treated at different soak time and submitted to thermomechanical cycling.A comparative experimental analysis was performed of the thermal properties of alloys obtained on a vacuum furnace,treated by DCT and thermomechanically cyclized.The results indicates that thermomechanical cycling promoted the appearance and growth of the martensitic phaseγ'1,less ductile than the martensitic phaseβ'1,which together with the induced hardening produced an increase in transformation temperatures and microhardness.The higher the number of cycles,the greater these effects.The DCT promoted an increase in the intensity of the diffraction peaks corresponding to the phaseβ'1 and the maintenance of them during the thermomechanical cycling of the material,which indicates that the DCT stabilizes the martensitic phaseβ'1 and,consequently,caused a reduction and stabilization of the martensitic transformation temperatures and the microhardness,when compared to the untreated material.The longer the soaking time of DCT,the greater these effects.
