Ti Ni shape memory alloys（SMAs） have been normally used as the competent elements in large part of the industries due to outstanding properties, such as super elasticity and shape memory effects. However, traditiona...Ti Ni shape memory alloys（SMAs） have been normally used as the competent elements in large part of the industries due to outstanding properties, such as super elasticity and shape memory effects. However, traditional machining of SMAs is quite complex due to these properties. Hence, the wire electric discharge machining（WEDM） characteristics of Ti Ni SMA was studied. The experiments were planned as per L27 orthogonal array to minimize the experiments, each experiment was performed under different conditions of pulse duration, pulse off time, servo voltage, flushing pressure and wire speed. A multi-response optimization method using Taguchi design with utility concept has been proposed for simultaneous optimization. The analysis of means（ANOM） and analysis of variance（ANOVA） on signal to noise（S/N） ratio were performed for determining the optimal parameter levels. Taguchi analysis reveals that a combination of 1 μs pulse duration, 3.8 μs pulse off time, 40 V servo voltage, 1.8×105 Pa flushing pressure and 8 m/min wire speed is beneficial for simultaneously maximizing the material removal rate（MRR） and minimizing the surface roughness. The optimization results of WEDM of Ti Ni SMA also indicate that pulse duration significantly affects the material removal rate and surface roughness. The discharged craters, micro cracks and recast layer were observed on the machined surface at large pulse duration.展开更多
Shape memory alloys （SMAs） are the developing advanced materials due to their versatile specific properties such as pseudoelasticity, shape memory effect （SME）, biocompatibility, high specific strength, high corro...Shape memory alloys （SMAs） are the developing advanced materials due to their versatile specific properties such as pseudoelasticity, shape memory effect （SME）, biocompatibility, high specific strength, high corrosion resistance, high wear resistance and high anti-fatigue property. Therefore, the SMAs are used in many applications such as aerospace, medical and automobile. However, the conventional machining of SMAs causes serious tool wear, time consuming and less dimensional deformity due to severe strain hardening and pseudoelasticity. These materials can be machined using non-conventional methods such as laser machining, water jet machining （WJM） and electrochemical machining （ECM）, but these processes are limited to complexity and mechanical properties of the component. Electrical discharge machining （EDM） and wire EDM （WEDM） show high capability to machine SMAs of complex shapes with precise dimensions. The aim of this work is to present the consolidated references on the machining of SMAs using EDM and WEDM and subsequently identify the research gaps. In support to these research gaps, this work has also evolved the future research directions.展开更多
Shape memory alloys (SMA) have been applied to a wide variety of applications in a number of different fields such as aeronautical applications, sensors/actuators, medical sciences as well as orthodontics. It is a hot...Shape memory alloys (SMA) have been applied to a wide variety of applications in a number of different fields such as aeronautical applications, sensors/actuators, medical sciences as well as orthodontics. It is a hot topic to enhance the anti-corrosion ability of orthodontic wires for clinical applications. In this letter, a very nice fractal structure, micro-domains with identical nanometer sized grooves, was ob- tained on the surfaces of the orthodontic wires with an oxygen plasma and acid corrosion. The concave parts of the grooves were dominated by titanium and convex parts were the same as the bulk wires. The micro-nano fractal structure generated a hydrophobic surface with the largest contact angle to water being about 157°. The titanium dominated nanolayer and the hydrophobicity of the surface resulted in jointly the great improvement of the anti-corrosion ability of the orthodontic wires. Because the fractal structures of the wires were formed automatically when they immersed in acidic environment, hence, the self-protection of the oxygen plasma-treated orthodontic wires in acidic environment indicates their potential applications in orthodontics, and should be also inspirable for other applications of SMA materials.展开更多
A deformation measurement method of interframe displacement was proposed in this paper. By online monitoring the shape di- mensions of both the deformation zone and its adjacent zone by machine vision, the initial and...A deformation measurement method of interframe displacement was proposed in this paper. By online monitoring the shape di- mensions of both the deformation zone and its adjacent zone by machine vision, the initial and terminative positions of deformation were dynamically identified during dieless drawing, and the global monitoring and online closed-loop control of the deformation zone were achieved. The dieless drawing process was systematically carried out on NiTi shape memory alloy wires. It is shown that the deformation measurement method of interframe displacement can track the axial displacement of the wires, but this cannot be achieved by traditional machine vision. The initial and terminative positions of deformation can be accurately identified by this method. The proposed rectifying control technology can effectively decrease the wire diameter fluctuation during dieless drawing, that is, the standard deviation of the wire diameter fluctuation could be decreased fi＇om 0.30 to 0.08 mm after three passes of dieless drawing, indicating that the control system has a good rectifying ability.展开更多
The microstructure of CosoNi22Ga28 ribbon with the L10 structure is examined. The band-like morphology is observed. These bands with the width in a range of 40-200 nm appear along the transverse direction of the ribbo...The microstructure of CosoNi22Ga28 ribbon with the L10 structure is examined. The band-like morphology is observed. These bands with the width in a range of 40-200 nm appear along the transverse direction of the ribbon. The giant magnetoimpedance （GMI） effect in this alloy is measured. The results show that Co5oNi22Ga28 exhibits a sharp peak of the GAI effect. The maximum GAH ratio up to 360% is detected. The GMI effect measured versus temperature shows large jumps of the magnetoimpedance amplitude at the reversal martensitic transformation temperature 240℃ and Curie temperature 375℃C respectively. The jump ratios of the magnetoimpedance amplitude examined at these temperatures are about 5 and 10, respectively.展开更多
Carbon fiber reinforced polymer (CFRP) composites have excellent mechanical properties, specifically, high specific stiffness and strength. However, most CFRP composites exhibit poor impact resistance. To overcome thi...Carbon fiber reinforced polymer (CFRP) composites have excellent mechanical properties, specifically, high specific stiffness and strength. However, most CFRP composites exhibit poor impact resistance. To overcome this limitation, this study presents a new plain-woven CFRP composite embedded with superelastic shape memory alloy (SMA) wires. Composite specimens are fabricated using the vacuum-assisted resin injection method. Drop-weight impact tests are conducted on composite specimens with and without SMA wires to evaluate the improvement of impact resistance. The material models of the CFRP composite and superelastic SMA wire are introduced and implemented into a finite element (FE) software by the explicit user-defined material subroutine. FE simulations of the drop-weight impact tests are performed to reveal the superelastic deformation and debonding failure of the SMA inserts. Improvement of the energy absorption capacity and toughness of the SMA-CFRP composite is confirmed by the comparison results.展开更多
文摘Ti Ni shape memory alloys（SMAs） have been normally used as the competent elements in large part of the industries due to outstanding properties, such as super elasticity and shape memory effects. However, traditional machining of SMAs is quite complex due to these properties. Hence, the wire electric discharge machining（WEDM） characteristics of Ti Ni SMA was studied. The experiments were planned as per L27 orthogonal array to minimize the experiments, each experiment was performed under different conditions of pulse duration, pulse off time, servo voltage, flushing pressure and wire speed. A multi-response optimization method using Taguchi design with utility concept has been proposed for simultaneous optimization. The analysis of means（ANOM） and analysis of variance（ANOVA） on signal to noise（S/N） ratio were performed for determining the optimal parameter levels. Taguchi analysis reveals that a combination of 1 μs pulse duration, 3.8 μs pulse off time, 40 V servo voltage, 1.8×105 Pa flushing pressure and 8 m/min wire speed is beneficial for simultaneously maximizing the material removal rate（MRR） and minimizing the surface roughness. The optimization results of WEDM of Ti Ni SMA also indicate that pulse duration significantly affects the material removal rate and surface roughness. The discharged craters, micro cracks and recast layer were observed on the machined surface at large pulse duration.
文摘Shape memory alloys （SMAs） are the developing advanced materials due to their versatile specific properties such as pseudoelasticity, shape memory effect （SME）, biocompatibility, high specific strength, high corrosion resistance, high wear resistance and high anti-fatigue property. Therefore, the SMAs are used in many applications such as aerospace, medical and automobile. However, the conventional machining of SMAs causes serious tool wear, time consuming and less dimensional deformity due to severe strain hardening and pseudoelasticity. These materials can be machined using non-conventional methods such as laser machining, water jet machining （WJM） and electrochemical machining （ECM）, but these processes are limited to complexity and mechanical properties of the component. Electrical discharge machining （EDM） and wire EDM （WEDM） show high capability to machine SMAs of complex shapes with precise dimensions. The aim of this work is to present the consolidated references on the machining of SMAs using EDM and WEDM and subsequently identify the research gaps. In support to these research gaps, this work has also evolved the future research directions.
基金Supported by the National Natural Science Foundation of China (Grant No. 30572067)Ministry of Science and Technology of China
文摘Shape memory alloys (SMA) have been applied to a wide variety of applications in a number of different fields such as aeronautical applications, sensors/actuators, medical sciences as well as orthodontics. It is a hot topic to enhance the anti-corrosion ability of orthodontic wires for clinical applications. In this letter, a very nice fractal structure, micro-domains with identical nanometer sized grooves, was ob- tained on the surfaces of the orthodontic wires with an oxygen plasma and acid corrosion. The concave parts of the grooves were dominated by titanium and convex parts were the same as the bulk wires. The micro-nano fractal structure generated a hydrophobic surface with the largest contact angle to water being about 157°. The titanium dominated nanolayer and the hydrophobicity of the surface resulted in jointly the great improvement of the anti-corrosion ability of the orthodontic wires. Because the fractal structures of the wires were formed automatically when they immersed in acidic environment, hence, the self-protection of the oxygen plasma-treated orthodontic wires in acidic environment indicates their potential applications in orthodontics, and should be also inspirable for other applications of SMA materials.
基金financially supported by the National Basic Research Priorities Program of China (No.2011CB606300)the National Natural Science Foundation of China (Nos.50634010 and 50674008)+1 种基金the Program for New Century Excellent Talents in Chinese Universities(No.NCET-06-0083)the Universities Fundamental Research Foundation of the Ministry of Education, China (No.FRF-TP-10-002B)
文摘A deformation measurement method of interframe displacement was proposed in this paper. By online monitoring the shape di- mensions of both the deformation zone and its adjacent zone by machine vision, the initial and terminative positions of deformation were dynamically identified during dieless drawing, and the global monitoring and online closed-loop control of the deformation zone were achieved. The dieless drawing process was systematically carried out on NiTi shape memory alloy wires. It is shown that the deformation measurement method of interframe displacement can track the axial displacement of the wires, but this cannot be achieved by traditional machine vision. The initial and terminative positions of deformation can be accurately identified by this method. The proposed rectifying control technology can effectively decrease the wire diameter fluctuation during dieless drawing, that is, the standard deviation of the wire diameter fluctuation could be decreased fi＇om 0.30 to 0.08 mm after three passes of dieless drawing, indicating that the control system has a good rectifying ability.
基金Supported by the National High Technology Research and Development Programme of China under Grant No 2003AA327010, and the National Natural Science Foundation of China under Grant No 60271028.
文摘The microstructure of CosoNi22Ga28 ribbon with the L10 structure is examined. The band-like morphology is observed. These bands with the width in a range of 40-200 nm appear along the transverse direction of the ribbon. The giant magnetoimpedance （GMI） effect in this alloy is measured. The results show that Co5oNi22Ga28 exhibits a sharp peak of the GAI effect. The maximum GAH ratio up to 360% is detected. The GMI effect measured versus temperature shows large jumps of the magnetoimpedance amplitude at the reversal martensitic transformation temperature 240℃ and Curie temperature 375℃C respectively. The jump ratios of the magnetoimpedance amplitude examined at these temperatures are about 5 and 10, respectively.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.11802243 and 11802241).
文摘Carbon fiber reinforced polymer (CFRP) composites have excellent mechanical properties, specifically, high specific stiffness and strength. However, most CFRP composites exhibit poor impact resistance. To overcome this limitation, this study presents a new plain-woven CFRP composite embedded with superelastic shape memory alloy (SMA) wires. Composite specimens are fabricated using the vacuum-assisted resin injection method. Drop-weight impact tests are conducted on composite specimens with and without SMA wires to evaluate the improvement of impact resistance. The material models of the CFRP composite and superelastic SMA wire are introduced and implemented into a finite element (FE) software by the explicit user-defined material subroutine. FE simulations of the drop-weight impact tests are performed to reveal the superelastic deformation and debonding failure of the SMA inserts. Improvement of the energy absorption capacity and toughness of the SMA-CFRP composite is confirmed by the comparison results.
