Providing early safety warning for batteries in real-world applications is challenging.In this study,comprehensive thermal abuse experiments are conducted to clarify the multidimensional signal evolution of battery fa...Providing early safety warning for batteries in real-world applications is challenging.In this study,comprehensive thermal abuse experiments are conducted to clarify the multidimensional signal evolution of battery failure under various preload forces.The time-sequence relationship among expansion force,voltage,and temperature during thermal abuse under five categorised stages is revealed.Three characteristic peaks are identified for the expansion force,which correspond to venting,internal short-circuiting,and thermal runaway.In particular,an abnormal expansion force signal can be detected at temperatures as low as 42.4°C,followed by battery thermal runaway in approximately 6.5 min.Moreover,reducing the preload force can improve the effectiveness of the early-warning method via the expansion force.Specifically,reducing the preload force from 6000 to 1000 N prolongs the warning time(i.e.,227 to 398 s)before thermal runaway is triggered.Based on the results,a notable expansion force early-warning method is proposed that can successfully enable early safety warning approximately 375 s ahead of battery thermal runaway and effectively prevent failure propagation with module validation.This study provides a practical reference for the development of timely and accurate early-warning strategies as well as guidance for the design of safer battery systems.展开更多
The first wall in the Experimental Advanced Superconducting Tokamak （EAST） used graphite tiles to withstand high thermal energy. The graphite tiles are mounted on the heat sink using screw bolts which have been prel...The first wall in the Experimental Advanced Superconducting Tokamak （EAST） used graphite tiles to withstand high thermal energy. The graphite tiles are mounted on the heat sink using screw bolts which have been preloaded to produce a clamp force. The clamp force is very important to keep the graphite tiles tightly on the surface of the heat sink so that the heat flux crosses this contacting surface in a small thermal resistor. Without the clamp force, the small gap between the graphite tiles and the heat sink will make it impossible for thermal power to be carried away by cooling water. Some bolts may even fall off with the loss of clamp force. From the mathematical models, the loss process of the clamp force has been studied. Research results explain how the different thermal expansions of three members of the screw joint makes the clamp force decrease to zero under temperature rise and external force, and how the stiffness affects the relation between the clamp force and temperature. The research also gives the critical temperature at which the clamp force can remain above zero. Analysis results indicate that the current screw joints are almost destined to lose their clamp force during the running time of EAST, so the bolt joints should be redesigned in order to improve its reliability.展开更多
The interrelationship between preload forces and natural frequencies of anchors was obtained from the structure of an anchor and its mechanical characteristics. We established a numerical model for the dynamic analysi...The interrelationship between preload forces and natural frequencies of anchors was obtained from the structure of an anchor and its mechanical characteristics. We established a numerical model for the dynamic analysis of a bolt support system taking into consideration the working surroundings of the anchor. The natural frequency distribution of the system under various preload forces of the anchor was analyzed with ANSYS. Our results show that each order of the system frequency varied with an increase in preload forces. A single order frequency decreased with an increase in the preload force. A preload force affected low-order frequencies more than high-order frequencies. We obtained a functional relationship by fitting preload forces and fundamental frequencies, which was in agreement with our theretical considerations. This study provides theoretical support for the detection of preload forces.展开更多
基金supported by the National Key R&D Program of China(2022YFB2404300)the National Natural Science Foundation of China(NSFC Nos.52177217 and 52106244)。
文摘Providing early safety warning for batteries in real-world applications is challenging.In this study,comprehensive thermal abuse experiments are conducted to clarify the multidimensional signal evolution of battery failure under various preload forces.The time-sequence relationship among expansion force,voltage,and temperature during thermal abuse under five categorised stages is revealed.Three characteristic peaks are identified for the expansion force,which correspond to venting,internal short-circuiting,and thermal runaway.In particular,an abnormal expansion force signal can be detected at temperatures as low as 42.4°C,followed by battery thermal runaway in approximately 6.5 min.Moreover,reducing the preload force can improve the effectiveness of the early-warning method via the expansion force.Specifically,reducing the preload force from 6000 to 1000 N prolongs the warning time(i.e.,227 to 398 s)before thermal runaway is triggered.Based on the results,a notable expansion force early-warning method is proposed that can successfully enable early safety warning approximately 375 s ahead of battery thermal runaway and effectively prevent failure propagation with module validation.This study provides a practical reference for the development of timely and accurate early-warning strategies as well as guidance for the design of safer battery systems.
文摘The first wall in the Experimental Advanced Superconducting Tokamak （EAST） used graphite tiles to withstand high thermal energy. The graphite tiles are mounted on the heat sink using screw bolts which have been preloaded to produce a clamp force. The clamp force is very important to keep the graphite tiles tightly on the surface of the heat sink so that the heat flux crosses this contacting surface in a small thermal resistor. Without the clamp force, the small gap between the graphite tiles and the heat sink will make it impossible for thermal power to be carried away by cooling water. Some bolts may even fall off with the loss of clamp force. From the mathematical models, the loss process of the clamp force has been studied. Research results explain how the different thermal expansions of three members of the screw joint makes the clamp force decrease to zero under temperature rise and external force, and how the stiffness affects the relation between the clamp force and temperature. The research also gives the critical temperature at which the clamp force can remain above zero. Analysis results indicate that the current screw joints are almost destined to lose their clamp force during the running time of EAST, so the bolt joints should be redesigned in order to improve its reliability.
基金the financial support from the National Basic Research Program of China (No. 2013CB227900)the China Postdoctoral Science Foundation (No. 20110491483)the State Key Laboratory of Coal Resources and Mine Safety(No. 10F08)
文摘The interrelationship between preload forces and natural frequencies of anchors was obtained from the structure of an anchor and its mechanical characteristics. We established a numerical model for the dynamic analysis of a bolt support system taking into consideration the working surroundings of the anchor. The natural frequency distribution of the system under various preload forces of the anchor was analyzed with ANSYS. Our results show that each order of the system frequency varied with an increase in preload forces. A single order frequency decreased with an increase in the preload force. A preload force affected low-order frequencies more than high-order frequencies. We obtained a functional relationship by fitting preload forces and fundamental frequencies, which was in agreement with our theretical considerations. This study provides theoretical support for the detection of preload forces.
