Research Of Shape Memory Alloy In Structural Self-repair Design And Experiment

Shape Memory Alloy (SMA) is a new material with perceptional and driving function, the two most significant properties of SMA are Shape Memory Effect (SME) and Super Elasticity (SE). Researcher of civil engineering using the characteristics of SMA in iNiTiative or passive control of structure get significant effect, thus aroused widespread concern. However, research of SMA used in concrete structure detection and strengthening is still in the exploration and experimental stage, further studies are needed. This paper focuses on some problems that happened in civil engineering and dose some research as follow.Aiming at the difference of SMA alloy stress-strain hysteresis loop, temperature distribution and phase transition temperature, face to the following aspects:strain rate, the temperature distribution and phase transformation front made theoretical derivation and simulations of SMA alloy performance influence. Results show that,more higher of the strain rate more bigger the hysteresis loop are and temperature tend to rising; the temperature distribution of alloy in the process of heating is related with length of alloy and electrify current state; the phenomenon of phase transition temperature non-uniform is related with internal stress of alloy, along with the increase of stress, the more obvious move forward of phase transition temperature and the more serious non-uniformity of temperature distribution are.Adopt tensile tests and differential scanning calorimetry (DSC) for SMA silk mechanics performance tests. Test results show, in loading process the higher of strain rate the bigger of hysteresis loop and strain of SMA alloy silk is bigger than general metal materials, it's strain can satisfy the conditions necessary for crack repair; SMA phase transition temperature tested by DSC, to avoid influence of the factors such as phase transition move forward, heating temperature of self-repairing tests should be controlled above 70℃.This paper researches on self-healing ability of beam crack, which contain SMA wires. The results show it has remarkable effect when SMA wire install on external, and the cracks are self-healing.This paper take advantage of Shape Memory Effect and Super Elasticity; put SMA wires into beams which made up of epoxy resin cement plaster and silica gel clay polymer. Use three-point bending experiments to make sure beam's mechanical property. Further more make a research about beam's self-healing ability. The result show us that SMA material can change beam's mechanical property clearly and beam's bearing capacity is improvement because of SMA wires. And the SMA wires can make crack self-healing come true. But that's complicated SMA lines are unlimited for sticking length, so the length must be suitable that can help crack finish self-healing. Aiming at influencing factors of polymer beam self-repairing ability: the way of SMA installation and analysis unbonded length in beam, results show that,bending moment producing in process of shape recovery of external installation of SMA wire is more favorable to crack repair; while unbonded length of embedded SMA beam is crucial to the degree of crack repair, that is unbonded length must satisfy the effective working length of SMA alloy wire, or else it's difficult to realize the fracture healing.The results of this paper will provide test reference for further research of SMA in civil structure project application.