The construction of lunar bases represents a crucial goal for long-term human residence on the Moon and future deep-space exploration. Vacuum sintering of lunar regolith for in-situ resource utilization(ISRU) is consi...The construction of lunar bases represents a crucial goal for long-term human residence on the Moon and future deep-space exploration. Vacuum sintering of lunar regolith for in-situ resource utilization(ISRU) is considered one of the most feasible strategies for early lunar infrastructure development. However, the extreme temperature fluctuations on the lunar surface pose potential threats to the structural stability of sintered regolith materials. To investigate the mechanical deterioration and damage mechanism of vacuum-sintered lunar regolith under extreme cryogenic-thermal cycling, lunar regolith simulants are used to fabricate specimens through vacuum sintering. A series of cryogenic-thermal cycling tests is designed, combined with uniaxial compression and X-ray CT scanning, to systematically analyze their macro-micro responses. The results show that with increasing extreme cryogenic-thermal cycles, the stress-strain curves evolve from typical brittle failure to quasiductile behavior, with uniaxial compressive strength and elastic modulus decreasing by approximately 33.86% and 61.98%, respectively. CT analyses reveal that the pore structure transforms from isolated pores to connected networks, with the pore volume fraction increasing from 13.33% to 22.64%, and the fractal dimension increases from 2.465 to 2.544, and stabilizes after multiple cycles. A significant negative correlation(R^(2)> 0.96) exists between pore structural complexity and mechanical performance. Based on these findings, a thermal fatigue damage mechanism dominated by thermal stress concentration due to mismatched thermal expansion coefficients among mineral phases is proposed. This study provides scientific insights for the design, durability evaluation, and ISRU-based construction of lunar surface infrastructure.展开更多
Fatigue cutting is a new approach for separating material. Man-made fatigue can be realized by applying a rotating bending load to a notched bar. To better utilize the new method, laser treatment is adopted in this st...Fatigue cutting is a new approach for separating material. Man-made fatigue can be realized by applying a rotating bending load to a notched bar. To better utilize the new method, laser treatment is adopted in this study. After laser radiation at the notch root, the fatigue cycle of the bar drops dramatically. Based on the experimental result, we draw the conclusion that the fatigue of the bar is influenced by the shape of the hardened area. A hardened area that has a small axial dimension and a relatively large radial dimension facilitates the fatigue. The desirable hardened area can be obtained by controlling the laser treatment parameters.展开更多
In our recent effort,we introduced a submaximal index that utilized ventilatory efficiency relative to CO2 production（VE/CO2）to evaluate the cardiovascular effectiveness to functional electrical stimulation lower-ex...In our recent effort,we introduced a submaximal index that utilized ventilatory efficiency relative to CO2 production（VE/CO2）to evaluate the cardiovascular effectiveness to functional electrical stimulation lower-extremity cycling（FESLEC）in persons with spinal cord injury（SCI）（Gorgey and Lawrence,2016）.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.U23A6018,42362034)the Applied Basic Research Foundation of Yunnan Province,China (Grant No.202401AS070068)。
文摘The construction of lunar bases represents a crucial goal for long-term human residence on the Moon and future deep-space exploration. Vacuum sintering of lunar regolith for in-situ resource utilization(ISRU) is considered one of the most feasible strategies for early lunar infrastructure development. However, the extreme temperature fluctuations on the lunar surface pose potential threats to the structural stability of sintered regolith materials. To investigate the mechanical deterioration and damage mechanism of vacuum-sintered lunar regolith under extreme cryogenic-thermal cycling, lunar regolith simulants are used to fabricate specimens through vacuum sintering. A series of cryogenic-thermal cycling tests is designed, combined with uniaxial compression and X-ray CT scanning, to systematically analyze their macro-micro responses. The results show that with increasing extreme cryogenic-thermal cycles, the stress-strain curves evolve from typical brittle failure to quasiductile behavior, with uniaxial compressive strength and elastic modulus decreasing by approximately 33.86% and 61.98%, respectively. CT analyses reveal that the pore structure transforms from isolated pores to connected networks, with the pore volume fraction increasing from 13.33% to 22.64%, and the fractal dimension increases from 2.465 to 2.544, and stabilizes after multiple cycles. A significant negative correlation(R^(2)> 0.96) exists between pore structural complexity and mechanical performance. Based on these findings, a thermal fatigue damage mechanism dominated by thermal stress concentration due to mismatched thermal expansion coefficients among mineral phases is proposed. This study provides scientific insights for the design, durability evaluation, and ISRU-based construction of lunar surface infrastructure.
文摘Fatigue cutting is a new approach for separating material. Man-made fatigue can be realized by applying a rotating bending load to a notched bar. To better utilize the new method, laser treatment is adopted in this study. After laser radiation at the notch root, the fatigue cycle of the bar drops dramatically. Based on the experimental result, we draw the conclusion that the fatigue of the bar is influenced by the shape of the hardened area. A hardened area that has a small axial dimension and a relatively large radial dimension facilitates the fatigue. The desirable hardened area can be obtained by controlling the laser treatment parameters.
基金supported by the Department of Veteran Affairs,Veteran Health Administration,Rehabilitation Research and Development Service (B7867-W)Department of Defense-CDRMP (# SC140119)
文摘In our recent effort,we introduced a submaximal index that utilized ventilatory efficiency relative to CO2 production（VE/CO2）to evaluate the cardiovascular effectiveness to functional electrical stimulation lower-extremity cycling（FESLEC）in persons with spinal cord injury（SCI）（Gorgey and Lawrence,2016）.
