To address the problem of conventional approaches for mechanical property determination requiring destructive sampling, which may be unsuitable for in-service structures, the authors proposed a method for determining ...To address the problem of conventional approaches for mechanical property determination requiring destructive sampling, which may be unsuitable for in-service structures, the authors proposed a method for determining the quasi-static fracture toughness and impact absorbed energy of ductile metals from spherical indentation tests (SITs). The stress status and damage mechanism of SIT, mode I fracture, Charpy impact tests, and related tests were frst investigated through fnite element (FE) calculations and scanning electron microscopy (SEM) observations, respectively. It was found that the damage mechanism of SITs is diferent from that of mode I fractures, while mode I fractures and Charpy impact tests share the same damage mechanism. Considering the diference between SIT and mode I fractures, uniaxial tension and pure shear were introduced to correlate SIT with mode I fractures. Based on this, the widely used critical indentation energy (CIE) model for fracture toughness determination using SITs was modifed. The quasi-static fracture toughness determined from the modifed CIE model was used to evaluate the impact absorbed energy using the dynamic fracture toughness and energy for crack initiation. The efectiveness of the newly proposed method was verifed through experiments on four types of steels: Q345R, SA508-3, 18MnMoNbR, and S30408.展开更多
Recent advances in the application of the nonlinear energy sink under a sinusoidal excitation make it possible to investigate metal-rubber vibration absorber. To provide such a vibration absorber for the integrated sp...Recent advances in the application of the nonlinear energy sink under a sinusoidal excitation make it possible to investigate metal-rubber vibration absorber. To provide such a vibration absorber for the integrated spacecraft platform,we analyze the targeted energy transfer of the simplified model with nonlinear energy sink using the complex-variables averaging method. Theoretical study shows two quasi-periodic responses that are essentially different in this nonlinear system. The steady-state response which is one of two quasi-periodic responses is caused by the linear instability of system,and another one appears as a result of the nonlinear normal modes between the linear and nonlinear oscillators,resulting from the energy transfer of different oscillators,and it can be used to vibration absorber. Secondly,this paper also discusses the performance of the proposed nonlinear absorber by using the phase portraits. All conclusion derived by the analytic model is verified numerically and the results are consistent with numerical simulations.展开更多
The twin-tube shock absorber was studied and the relevant factors of thermal equilibrium were simulated. The dynamic model of the shock absorber was constructed and simulation curves of force-displacement and force-ve...The twin-tube shock absorber was studied and the relevant factors of thermal equilibrium were simulated. The dynamic model of the shock absorber was constructed and simulation curves of force-displacement and force-velocity were output. The experiment of the twin-tube shock absorber was carried out, and the results were compared with the modeling resultss. Further, the vibration energy regeneration model was established, and the bench simulation study was carried out. The re- sults showed that the energy regeneration model not only absorbed shock energy but also converted vibration energy into electricity energy.展开更多
Thin-walled tubes are extensively applied in engineering, especially in vehicle structures to resist axial or traversal impact loads, for their excellent energy absorbing capacity. However, in the axial deformation mo...Thin-walled tubes are extensively applied in engineering, especially in vehicle structures to resist axial or traversal impact loads, for their excellent energy absorbing capacity. However, in the axial deformation mode, the force history has an extremely high peak force which may bring not only fatal injury to occupants but also damage to structures, cargo and environment. Aiming to develop energy absorbers with impact-force modificator, square metal tube with force modificator is investigated which can monitor the force-deformation history of the tube. A small device is designed to serve as an impact-force modificator, which introduces desired imperfections to the square tube just before the impact happens between the impactor and the tube, so as to reduce the peak force. Prototypes with various governing parameters were manufactured and tested both quasi-statically and dynamically to study the effects of these parameters on the characteristics of energy absorption. The results show that the force modificator can achieve the desired reduction of the peak force well whilst remaining the specific energy absorption capacity of the original square tube. With future improvements, it could be applied to vehicles or roadside safety hardware to mitigate the consequences produced by traffic accidents.展开更多
A new type energy absorber was introduced,which is composed of thousands of thin ring plates with different diameters.Because it can switch the impact to thousands of shearing actions among thin ring plates inside the...A new type energy absorber was introduced,which is composed of thousands of thin ring plates with different diameters.Because it can switch the impact to thousands of shearing actions among thin ring plates inside the absorber,the impact energy is decentralized and dissipated gradually,the impact acting time is extended and the peak of acceleration is reduced obviously.Numerical simulations by finite element method (FEM) coupled with smoothed particle hydrodynamics (SPH) method were preformed to predict the energy absorption characteristics.Energy absorption ability with different impact velocities was studied and the effects of thickness and material of ring plates were discussed.The sled crash test was carried out to validate the result of simulations.The new type absorber is effective for collision that impact velocity is lower than 40 km/h.展开更多
In this paper,a PZT(lead zirconate titanate)-based absorber and energy harvester(PAEH)is used for passive control of friction-induced stick-slip vibration in a friction system.Its stability condition coupled with PAEH...In this paper,a PZT(lead zirconate titanate)-based absorber and energy harvester(PAEH)is used for passive control of friction-induced stick-slip vibration in a friction system.Its stability condition coupled with PAEH is analytically derived,whose efficiency is then demonstrated by numerical simulation.The results show that the structural parameters of the PAEH can significantly affect the system stability,which increases with the mass ratio between the PAEH and the primary system,but first increases and then decreases with the natural frequency ratio between the PAEH and the primary system.The impacts of the electric parameters of the PAEH on the system stability are found to be insignificant.In addition,the PAEH can effectively suppress the stick-slip limit cycle magnitude in a wide working parameter range;however,it does not function well for friction systems in all the working conditions.The stick-slip vibration amplitude can be increased in the case of a large loading(normal)force.Finally,an experiment on a tribo-dynamometer validates the findings of the theoretical study,in which the vibration reduction and energy harvesting performance of the PAEH is fully demonstrated.展开更多
In this paper, we present a comprehensive numerical simulation of a point wave absorber in deep water. Analyses are performed in both the frequency and time domains. The converter is a two-body floating-point absorber...In this paper, we present a comprehensive numerical simulation of a point wave absorber in deep water. Analyses are performed in both the frequency and time domains. The converter is a two-body floating-point absorber (FPA) with one degree of freedom in the heave direction. Its two parts are connected by a linear mass-spring-damper system. The commercial ANSYS-AQWA software used in this study performs well in considering validations. The velocity potential is obtained by assuming incompressible and irrotational flow. As such, we investigated the effects of wave characteristics on energy conversion and device efficiency, including wave height and wave period, as well as the device diameter, draft, geometry, and damping coefficient. To validate the model, we compared our numerical results with those from similar experiments. Our study results can clearly help to maximize the converter's efficiency when considering specific conditions.展开更多
The relationship between Charpy absorbed energy and the fracture toughness by means of the (crack tip opening displacement (CTOD)) method was analyzed based on the Weibull stress criterion. The Charpy absorbed energy ...The relationship between Charpy absorbed energy and the fracture toughness by means of the (crack tip opening displacement (CTOD)) method was analyzed based on the Weibull stress criterion. The Charpy absorbed energy and the fracture toughness were measured for the SN490B steel under the ductile-brittle transition temperature region. For the instrumented Charpy impact test, the curves between the loading point displacement and the load against time were recorded. The critical Weibull stress was taken as a fracture controlled parameter, and it could not be affected by the specimen configuration and the loading pattern based on the local approach. The parameters controlled brittle fracture are obtained from the Charpy absorbed energy results, then the fracture toughness for the compact tension (CT) specimen is predicted. It is found that the results predicted are in good agreement with the experimental. The fracture toughness could be evaluated by the Charpy absorbed energy, because the local approach gives a good description for the brittle fracture even though the Charpy impact specimen or the CT specimen is used for the given material.展开更多
A kind of composite buffering material was made by filling the voids of honeycomb paperboard with polyurethane. Drop tests were performed to evaluate the dynamic energy absorption capacity of the material. Based on th...A kind of composite buffering material was made by filling the voids of honeycomb paperboard with polyurethane. Drop tests were performed to evaluate the dynamic energy absorption capacity of the material. Based on the tests results,the mechanical behaviors of the material under low velocity dynamic impact conditions were analyzed. It was shown that the absorbed energy of the composite material varies inversely with the void diameter. The absorbed energy of the composite material is 1- 2 times than that of honeycomb paperboard and polyurethane. The energy absorption efficiency of the composite material is better than those of honeycomb paperboard and polyurethane.展开更多
This paper presents an extended model predictive controller for maximizing the absorbed power of a point absorber wave energy converter. Owing to the great influence of controller parameters upon the absorbed power, t...This paper presents an extended model predictive controller for maximizing the absorbed power of a point absorber wave energy converter. Owing to the great influence of controller parameters upon the absorbed power, the optimization of these parameters is carried out for the first time by a firefly algorithm(FA). Error, the difference between output velocity of buoy and input wave speed which leads to power maximization in the optimized MPC is compared with the classical MPC. Simulation results indicate that given the high accuracy and acceptable speed of the algorithm, it can adjust the parameters of the controller to the point where system error decreased effectively and the absorbed energy increased about 4 MW.展开更多
The CO2 separation from natural gas, syngas or flue gas represents an important industrial field of applications. An economic and energy-efficient CO2 separation from these gas streams is a prerequisite for sustainabl...The CO2 separation from natural gas, syngas or flue gas represents an important industrial field of applications. An economic and energy-efficient CO2 separation from these gas streams is a prerequisite for sustainable industry contributions to the megatrends resource efficiency and globalization of technologies. One way of reducing operational expenditure for these separation processes is the development of better performing CO2 absorbents. Although a number of absorbents for the separation of CO2 from process gas streams exist, the need for the development of CO2 absorbents with an improved absorption performance, less corrosion and foaming, no nitrosamine formation, lower energy requirement and therefore less operational expenditure remains. Recent industrial activities have led to the development of novel high-performance CO2 scrubbing agents that can be employed in numerous industrial processes such as natural gas treatment, purification of syngas and the scrubbing of flue gas. The objective of this paper is to introduce these new high-performance scrubbing agents and to compare their performance with other state-of-the-art absorbents. It turned out, that the evaluated absorbents offer high cyclic capacities in the range of 2.4 to 2.6 mol CO2/kg absorbent and low absorption enthalpies (–30 kJ/mol) allowing for distinctive savings in the regeneration energy of the absorbent. Calculations with the modified Kremser model resulted in a reduction of the specific reboiler heat duty of 55%. Furthermore, the absorbents are less corrosive than standard amines as indicated by the measured corrosion rates of 0.21 mm/y versus 1.18 mm/y for a piperazine/methyldiethanolamine mixture. Based on new experimental results it is shown how substantial savings in operational and capital expenditure can be realized due to favorable absorbent properties. The novel high-performance CO2 system solutions meet recent industrial absorbent requirements and allow for more efficient or new CO2 separation processes.展开更多
The present study investigates the effect of the addition of nanoparticles into epoxy resins as the matrix on the impact absorbed energy of CFRP (carbon fiber reinforced polymer). Impact absorbed energy is one of th...The present study investigates the effect of the addition of nanoparticles into epoxy resins as the matrix on the impact absorbed energy of CFRP (carbon fiber reinforced polymer). Impact absorbed energy is one of the main properties to evaluate the CFRP's performance for transportation and aerospace structures. Two types of nanoparticle, namely nanofibers and nano-silica beads, were added into the epoxy resin to improve the impact absorption capacity of the CFRP. Two modified additives and conventional epoxy resins were quantitatively compared. The impact test results showed that impact absorbed energy for nanofibers was higher than nano-silica beads, and nanofibers as the additive promoted about 11% of impact absorbed energy compared with neat epoxy resin.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.52275154)National Key Research and Development Project of China(Grant No.2016YFF0203005).
文摘To address the problem of conventional approaches for mechanical property determination requiring destructive sampling, which may be unsuitable for in-service structures, the authors proposed a method for determining the quasi-static fracture toughness and impact absorbed energy of ductile metals from spherical indentation tests (SITs). The stress status and damage mechanism of SIT, mode I fracture, Charpy impact tests, and related tests were frst investigated through fnite element (FE) calculations and scanning electron microscopy (SEM) observations, respectively. It was found that the damage mechanism of SITs is diferent from that of mode I fractures, while mode I fractures and Charpy impact tests share the same damage mechanism. Considering the diference between SIT and mode I fractures, uniaxial tension and pure shear were introduced to correlate SIT with mode I fractures. Based on this, the widely used critical indentation energy (CIE) model for fracture toughness determination using SITs was modifed. The quasi-static fracture toughness determined from the modifed CIE model was used to evaluate the impact absorbed energy using the dynamic fracture toughness and energy for crack initiation. The efectiveness of the newly proposed method was verifed through experiments on four types of steels: Q345R, SA508-3, 18MnMoNbR, and S30408.
基金Sponsored by the Open Fund of National Defense Key Discipline Laboratory of Micro-Spacecraft Technology(Grant No.HIT.KLOF.MST.201302)
文摘Recent advances in the application of the nonlinear energy sink under a sinusoidal excitation make it possible to investigate metal-rubber vibration absorber. To provide such a vibration absorber for the integrated spacecraft platform,we analyze the targeted energy transfer of the simplified model with nonlinear energy sink using the complex-variables averaging method. Theoretical study shows two quasi-periodic responses that are essentially different in this nonlinear system. The steady-state response which is one of two quasi-periodic responses is caused by the linear instability of system,and another one appears as a result of the nonlinear normal modes between the linear and nonlinear oscillators,resulting from the energy transfer of different oscillators,and it can be used to vibration absorber. Secondly,this paper also discusses the performance of the proposed nonlinear absorber by using the phase portraits. All conclusion derived by the analytic model is verified numerically and the results are consistent with numerical simulations.
基金Supported by the National High Technology Research and Development Program of China(2011AA11A223)
文摘The twin-tube shock absorber was studied and the relevant factors of thermal equilibrium were simulated. The dynamic model of the shock absorber was constructed and simulation curves of force-displacement and force-velocity were output. The experiment of the twin-tube shock absorber was carried out, and the results were compared with the modeling resultss. Further, the vibration energy regeneration model was established, and the bench simulation study was carried out. The re- sults showed that the energy regeneration model not only absorbed shock energy but also converted vibration energy into electricity energy.
基金Supported by the Hong Kong Research Grant Council (No.CERG 621S05)
文摘Thin-walled tubes are extensively applied in engineering, especially in vehicle structures to resist axial or traversal impact loads, for their excellent energy absorbing capacity. However, in the axial deformation mode, the force history has an extremely high peak force which may bring not only fatal injury to occupants but also damage to structures, cargo and environment. Aiming to develop energy absorbers with impact-force modificator, square metal tube with force modificator is investigated which can monitor the force-deformation history of the tube. A small device is designed to serve as an impact-force modificator, which introduces desired imperfections to the square tube just before the impact happens between the impactor and the tube, so as to reduce the peak force. Prototypes with various governing parameters were manufactured and tested both quasi-statically and dynamically to study the effects of these parameters on the characteristics of energy absorption. The results show that the force modificator can achieve the desired reduction of the peak force well whilst remaining the specific energy absorption capacity of the original square tube. With future improvements, it could be applied to vehicles or roadside safety hardware to mitigate the consequences produced by traffic accidents.
文摘A new type energy absorber was introduced,which is composed of thousands of thin ring plates with different diameters.Because it can switch the impact to thousands of shearing actions among thin ring plates inside the absorber,the impact energy is decentralized and dissipated gradually,the impact acting time is extended and the peak of acceleration is reduced obviously.Numerical simulations by finite element method (FEM) coupled with smoothed particle hydrodynamics (SPH) method were preformed to predict the energy absorption characteristics.Energy absorption ability with different impact velocities was studied and the effects of thickness and material of ring plates were discussed.The sled crash test was carried out to validate the result of simulations.The new type absorber is effective for collision that impact velocity is lower than 40 km/h.
基金the financial support of the National Natural Science Foundation of China(U22A20181,52275214,12272324).
文摘In this paper,a PZT(lead zirconate titanate)-based absorber and energy harvester(PAEH)is used for passive control of friction-induced stick-slip vibration in a friction system.Its stability condition coupled with PAEH is analytically derived,whose efficiency is then demonstrated by numerical simulation.The results show that the structural parameters of the PAEH can significantly affect the system stability,which increases with the mass ratio between the PAEH and the primary system,but first increases and then decreases with the natural frequency ratio between the PAEH and the primary system.The impacts of the electric parameters of the PAEH on the system stability are found to be insignificant.In addition,the PAEH can effectively suppress the stick-slip limit cycle magnitude in a wide working parameter range;however,it does not function well for friction systems in all the working conditions.The stick-slip vibration amplitude can be increased in the case of a large loading(normal)force.Finally,an experiment on a tribo-dynamometer validates the findings of the theoretical study,in which the vibration reduction and energy harvesting performance of the PAEH is fully demonstrated.
文摘In this paper, we present a comprehensive numerical simulation of a point wave absorber in deep water. Analyses are performed in both the frequency and time domains. The converter is a two-body floating-point absorber (FPA) with one degree of freedom in the heave direction. Its two parts are connected by a linear mass-spring-damper system. The commercial ANSYS-AQWA software used in this study performs well in considering validations. The velocity potential is obtained by assuming incompressible and irrotational flow. As such, we investigated the effects of wave characteristics on energy conversion and device efficiency, including wave height and wave period, as well as the device diameter, draft, geometry, and damping coefficient. To validate the model, we compared our numerical results with those from similar experiments. Our study results can clearly help to maximize the converter's efficiency when considering specific conditions.
基金The work is supported by the National Natural Science Foundation of China under grant No.50275107by Fok Ying Tung Education Foundation under grant No.81405.
文摘The relationship between Charpy absorbed energy and the fracture toughness by means of the (crack tip opening displacement (CTOD)) method was analyzed based on the Weibull stress criterion. The Charpy absorbed energy and the fracture toughness were measured for the SN490B steel under the ductile-brittle transition temperature region. For the instrumented Charpy impact test, the curves between the loading point displacement and the load against time were recorded. The critical Weibull stress was taken as a fracture controlled parameter, and it could not be affected by the specimen configuration and the loading pattern based on the local approach. The parameters controlled brittle fracture are obtained from the Charpy absorbed energy results, then the fracture toughness for the compact tension (CT) specimen is predicted. It is found that the results predicted are in good agreement with the experimental. The fracture toughness could be evaluated by the Charpy absorbed energy, because the local approach gives a good description for the brittle fracture even though the Charpy impact specimen or the CT specimen is used for the given material.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51008306)
文摘A kind of composite buffering material was made by filling the voids of honeycomb paperboard with polyurethane. Drop tests were performed to evaluate the dynamic energy absorption capacity of the material. Based on the tests results,the mechanical behaviors of the material under low velocity dynamic impact conditions were analyzed. It was shown that the absorbed energy of the composite material varies inversely with the void diameter. The absorbed energy of the composite material is 1- 2 times than that of honeycomb paperboard and polyurethane. The energy absorption efficiency of the composite material is better than those of honeycomb paperboard and polyurethane.
文摘This paper presents an extended model predictive controller for maximizing the absorbed power of a point absorber wave energy converter. Owing to the great influence of controller parameters upon the absorbed power, the optimization of these parameters is carried out for the first time by a firefly algorithm(FA). Error, the difference between output velocity of buoy and input wave speed which leads to power maximization in the optimized MPC is compared with the classical MPC. Simulation results indicate that given the high accuracy and acceptable speed of the algorithm, it can adjust the parameters of the controller to the point where system error decreased effectively and the absorbed energy increased about 4 MW.
文摘The CO2 separation from natural gas, syngas or flue gas represents an important industrial field of applications. An economic and energy-efficient CO2 separation from these gas streams is a prerequisite for sustainable industry contributions to the megatrends resource efficiency and globalization of technologies. One way of reducing operational expenditure for these separation processes is the development of better performing CO2 absorbents. Although a number of absorbents for the separation of CO2 from process gas streams exist, the need for the development of CO2 absorbents with an improved absorption performance, less corrosion and foaming, no nitrosamine formation, lower energy requirement and therefore less operational expenditure remains. Recent industrial activities have led to the development of novel high-performance CO2 scrubbing agents that can be employed in numerous industrial processes such as natural gas treatment, purification of syngas and the scrubbing of flue gas. The objective of this paper is to introduce these new high-performance scrubbing agents and to compare their performance with other state-of-the-art absorbents. It turned out, that the evaluated absorbents offer high cyclic capacities in the range of 2.4 to 2.6 mol CO2/kg absorbent and low absorption enthalpies (–30 kJ/mol) allowing for distinctive savings in the regeneration energy of the absorbent. Calculations with the modified Kremser model resulted in a reduction of the specific reboiler heat duty of 55%. Furthermore, the absorbents are less corrosive than standard amines as indicated by the measured corrosion rates of 0.21 mm/y versus 1.18 mm/y for a piperazine/methyldiethanolamine mixture. Based on new experimental results it is shown how substantial savings in operational and capital expenditure can be realized due to favorable absorbent properties. The novel high-performance CO2 system solutions meet recent industrial absorbent requirements and allow for more efficient or new CO2 separation processes.
文摘The present study investigates the effect of the addition of nanoparticles into epoxy resins as the matrix on the impact absorbed energy of CFRP (carbon fiber reinforced polymer). Impact absorbed energy is one of the main properties to evaluate the CFRP's performance for transportation and aerospace structures. Two types of nanoparticle, namely nanofibers and nano-silica beads, were added into the epoxy resin to improve the impact absorption capacity of the CFRP. Two modified additives and conventional epoxy resins were quantitatively compared. The impact test results showed that impact absorbed energy for nanofibers was higher than nano-silica beads, and nanofibers as the additive promoted about 11% of impact absorbed energy compared with neat epoxy resin.