Ultrasonic fracturing(UF)can be used to form crack networks for oil or gas in the mining industry and hard rock excavation.In this paper,the three-dimensional internal laser-engraved crack method(3DILC)is introduced t...Ultrasonic fracturing(UF)can be used to form crack networks for oil or gas in the mining industry and hard rock excavation.In this paper,the three-dimensional internal laser-engraved crack method(3DILC)is introduced to make penny-shaped internal crack within the samples without any damage to the surfaces.Physical experiments were performed on the transparent samples with internal cracks at different depths.The macro-and micro-fracture fractography characteristics were focused on and analyzed in details.Based on fractography,the mechanisms of the UF were revealed.The propagation paths of cracks of different depths were simulated based on the Paris fatigue model and compared with experimental results.The results show that the 3D-ILC method is a powerful tool for the experimental research on the internal crack propagation in the UF.Under the action of ultrasonic field,fractography shows the characteristics of beach marks,lance-like pattern,rime-like pattern and glass powder.It can be judged that the mechanisms of UF include high cycle fatigue fracture,shear fracture,and friction.The results of the numerical simulation using the Paris fatigue model are consistent with the experimental results.展开更多
In the present work the fatigue crack growth in AISI304 specimens is investigated experimentally. In 3D finite element analysis the virtual crack closure technique is applied to calculate distributions and variations ...In the present work the fatigue crack growth in AISI304 specimens is investigated experimentally. In 3D finite element analysis the virtual crack closure technique is applied to calculate distributions and variations of the stress intensity factor along the surface crack front. It is confirmed that the stress intensity factor along the surface crack front varies non-uniformly with crack growth. Crack growth rate is proportional to the stress intensity factor distribution in the 3D cracked specimen. The fatigue crack growth in surface cracked specimens can be described by the Forman model identified in conventional compact tension specimens. For crack growth in the free specimen surface the arc length seems more suitable to quantify crack progress. Geometry and loading configuration of the surface cracked specimen seem to not affect the fatigue crack growth substantially.展开更多
基金supported by the National Natural Science Foundation of China(Nos.51739008 and 41831281)the Natural Science Foundation of Jiangsu Province(No.BK20171130).
文摘Ultrasonic fracturing(UF)can be used to form crack networks for oil or gas in the mining industry and hard rock excavation.In this paper,the three-dimensional internal laser-engraved crack method(3DILC)is introduced to make penny-shaped internal crack within the samples without any damage to the surfaces.Physical experiments were performed on the transparent samples with internal cracks at different depths.The macro-and micro-fracture fractography characteristics were focused on and analyzed in details.Based on fractography,the mechanisms of the UF were revealed.The propagation paths of cracks of different depths were simulated based on the Paris fatigue model and compared with experimental results.The results show that the 3D-ILC method is a powerful tool for the experimental research on the internal crack propagation in the UF.Under the action of ultrasonic field,fractography shows the characteristics of beach marks,lance-like pattern,rime-like pattern and glass powder.It can be judged that the mechanisms of UF include high cycle fatigue fracture,shear fracture,and friction.The results of the numerical simulation using the Paris fatigue model are consistent with the experimental results.
基金supported by the German Science Foundation(DFG, YU119/5-2)
文摘In the present work the fatigue crack growth in AISI304 specimens is investigated experimentally. In 3D finite element analysis the virtual crack closure technique is applied to calculate distributions and variations of the stress intensity factor along the surface crack front. It is confirmed that the stress intensity factor along the surface crack front varies non-uniformly with crack growth. Crack growth rate is proportional to the stress intensity factor distribution in the 3D cracked specimen. The fatigue crack growth in surface cracked specimens can be described by the Forman model identified in conventional compact tension specimens. For crack growth in the free specimen surface the arc length seems more suitable to quantify crack progress. Geometry and loading configuration of the surface cracked specimen seem to not affect the fatigue crack growth substantially.
