The surface temperature of extruded AZ31B alloy plate was measured by infrared thermograph in air during tension and high-cycle fatigue tests. The mechanism of heat production was discussed and the value of critical f...The surface temperature of extruded AZ31B alloy plate was measured by infrared thermograph in air during tension and high-cycle fatigue tests. The mechanism of heat production was discussed and the value of critical fatigue damage temperature was calculated according to the P—ΔT curve. Results show that the variation trend of temperature is different between tension and fatigue tests. The temperature evolution in tension test consists of four stages： linear decrease, reverse linear increase, abrupt increase, and final drop. The initial decrease of temperature is caused by thermal elastic effect, which is corresponding to the elastic deformation in tension progress. When cyclic loading is above the fatigue limit, the temperature evolution mainly undergoes five stages： initial increase, steep reduction, steady state, abrupt increase, and final drop. The peak temperature in fatigue test is caused by strain hardening that can be used to evaluate the fatigue life of magnesium alloy. The critical temperature variation that causes the fatigue failure is 3.63 K. When ΔT≤3.63 K, the material is safe under cyclic loading. When ΔT3.63 K, the fatigue life is determined by cycle index and peak temperature.展开更多
Background: Infrared thermographic imaging(IRTG) is a safe and reliable technology used to monitor skin temperature. The main aim of our study was to evaluate the relationship between skin temperature changes and musc...Background: Infrared thermographic imaging(IRTG) is a safe and reliable technology used to monitor skin temperature. The main aim of our study was to evaluate the relationship between skin temperature changes and muscle fatigue in order to answer the main research question if IRTG can be used to monitor muscle fatigue.Methods: This was a case study performed on a 23-year-old trained middle distance runner. After warm-up the subject was exercising on the dynamometer for 7.5 min at 120?/s performing only concentric contractions of quadriceps. At the same time IRTG recording of both(exercising and non-exercising) quadriceps was performed.Results: A correlational analysis that was performed in order to quantify the relationship between power and temperature change over time has shown that there is a significant negative correlation between skin temperature increase and power decrease(r = -0.543, p = 0.036) of exercising quadriceps. In linear regression model the exercising quadriceps power could be predicted from skin temperature. No such relationships were noted for the non-exercising limb that served as a control.Conclusion: We believe that correlation between skin temperature change and muscle power output as described in this case study deserves further analysis on the larger sample including subjects of the different ages, health status, and physical abilities in order to create a new tool for monitoring the muscle fatigue.展开更多
This study presents a robustness optimization method for rapid prototyping(RP)of functional artifacts based on visualized computing digital twins(VCDT).A generalized multiobjective robustness optimization model for RP...This study presents a robustness optimization method for rapid prototyping(RP)of functional artifacts based on visualized computing digital twins(VCDT).A generalized multiobjective robustness optimization model for RP of scheme design prototype was first built,where thermal,structural,and multidisciplinary knowledge could be integrated for visualization.To implement visualized computing,the membership function of fuzzy decision-making was optimized using a genetic algorithm.Transient thermodynamic,structural statics,and flow field analyses were conducted,especially for glass fiber composite materials,which have the characteristics of high strength,corrosion resistance,temperature resistance,dimensional stability,and electrical insulation.An electrothermal experiment was performed by measuring the temperature and changes in temperature during RP.Infrared thermographs were obtained using thermal field measurements to determine the temperature distribution.A numerical analysis of a lightweight ribbed ergonomic artifact is presented to illustrate the VCDT.Moreover,manufacturability was verified based on a thermal-solid coupled finite element analysis.The physical experiment and practice proved that the proposed VCDT provided a robust design paradigm for a layered RP between the steady balance of electrothermal regulation and manufacturing efficacy under hybrid uncertainties.展开更多
基金Project(51175364)supported by the National Natural Science Foundation of ChinaProjec(2013011014-3)supported by the Natural Science Foundation of Shanxi Province,China
文摘The surface temperature of extruded AZ31B alloy plate was measured by infrared thermograph in air during tension and high-cycle fatigue tests. The mechanism of heat production was discussed and the value of critical fatigue damage temperature was calculated according to the P—ΔT curve. Results show that the variation trend of temperature is different between tension and fatigue tests. The temperature evolution in tension test consists of four stages： linear decrease, reverse linear increase, abrupt increase, and final drop. The initial decrease of temperature is caused by thermal elastic effect, which is corresponding to the elastic deformation in tension progress. When cyclic loading is above the fatigue limit, the temperature evolution mainly undergoes five stages： initial increase, steep reduction, steady state, abrupt increase, and final drop. The peak temperature in fatigue test is caused by strain hardening that can be used to evaluate the fatigue life of magnesium alloy. The critical temperature variation that causes the fatigue failure is 3.63 K. When ΔT≤3.63 K, the material is safe under cyclic loading. When ΔT3.63 K, the fatigue life is determined by cycle index and peak temperature.
文摘Background: Infrared thermographic imaging(IRTG) is a safe and reliable technology used to monitor skin temperature. The main aim of our study was to evaluate the relationship between skin temperature changes and muscle fatigue in order to answer the main research question if IRTG can be used to monitor muscle fatigue.Methods: This was a case study performed on a 23-year-old trained middle distance runner. After warm-up the subject was exercising on the dynamometer for 7.5 min at 120?/s performing only concentric contractions of quadriceps. At the same time IRTG recording of both(exercising and non-exercising) quadriceps was performed.Results: A correlational analysis that was performed in order to quantify the relationship between power and temperature change over time has shown that there is a significant negative correlation between skin temperature increase and power decrease(r = -0.543, p = 0.036) of exercising quadriceps. In linear regression model the exercising quadriceps power could be predicted from skin temperature. No such relationships were noted for the non-exercising limb that served as a control.Conclusion: We believe that correlation between skin temperature change and muscle power output as described in this case study deserves further analysis on the larger sample including subjects of the different ages, health status, and physical abilities in order to create a new tool for monitoring the muscle fatigue.
基金the National Natural Science Foundation of China,Nos.51935009 and 51821093National key research and development project of China,No.2022YFB3303303+2 种基金Zhejiang University president special fund financed by Zhejiang province,No.2021XZZX008Zhejiang provincial key research and development project of China,Nos.2023C01060,LZY22E060002 and LZ22E050008The Ng Teng Fong Charitable Foundation in the form of ZJU-SUTD IDEA Grant,No.188170-11102.
文摘This study presents a robustness optimization method for rapid prototyping(RP)of functional artifacts based on visualized computing digital twins(VCDT).A generalized multiobjective robustness optimization model for RP of scheme design prototype was first built,where thermal,structural,and multidisciplinary knowledge could be integrated for visualization.To implement visualized computing,the membership function of fuzzy decision-making was optimized using a genetic algorithm.Transient thermodynamic,structural statics,and flow field analyses were conducted,especially for glass fiber composite materials,which have the characteristics of high strength,corrosion resistance,temperature resistance,dimensional stability,and electrical insulation.An electrothermal experiment was performed by measuring the temperature and changes in temperature during RP.Infrared thermographs were obtained using thermal field measurements to determine the temperature distribution.A numerical analysis of a lightweight ribbed ergonomic artifact is presented to illustrate the VCDT.Moreover,manufacturability was verified based on a thermal-solid coupled finite element analysis.The physical experiment and practice proved that the proposed VCDT provided a robust design paradigm for a layered RP between the steady balance of electrothermal regulation and manufacturing efficacy under hybrid uncertainties.
