The article mainly talks about the characteristic of common and fine punching and the quality of shearing edge. Although the common punching has been widely applied, the quality of shearing edge is very poor. The fine...The article mainly talks about the characteristic of common and fine punching and the quality of shearing edge. Although the common punching has been widely applied, the quality of shearing edge is very poor. The fine punching work-piece is better in quality. But it isn’t still been widely applied, because the structure of die is complicated and the manufacture of die and using pressure machine are expensive. A new fine punching processing without burr is put forward by discussing the plastic status and press stress status of the material which influence the quality of the punching work-piece in the deformation zone, it provides the plastic status of material to determine the parameter in the new processing and presents the maximum value of plastic deformation specific energy when the material reaches the plastic status. The author has analyzed the initializing clearance and instantaneous clearance of the ordinary punching. The instantaneous clearance of the ordinary punching process is instable. By studying the author brings forward a kind of punching process which initializing clearance and instantaneous clearance are stable, that is the negative clearance fine punching process. Because of using the negative clearance fine punching process, the material of sheared distorting section comes into the plastic state. The surface quality of the punching sheared edge is advanced 1.5 times than that of the ordinary punching. The recommended value of depth of the negative clearance punching has been given in this article.展开更多
Ceramic matrix composite(CMC) and superalloy bolted joints have exhibited great potential for high temperature hot structure application in hypersonic aircraft. In service conditions, the thermal expansion mismatch be...Ceramic matrix composite(CMC) and superalloy bolted joints have exhibited great potential for high temperature hot structure application in hypersonic aircraft. In service conditions, the thermal expansion mismatch between CMC and superalloy plates will cause complex thermal stress and strain distributions at hole-edge areas and assembly parameters changes of the joints under elevated temperatures. These effects might lead to early damage of joint structure, which will endanger the structural integrity and load carrying capacity of aircraft components. In the present study, transient heat transfer and thermo-structural analysis of C/SiC composite and superalloy bolted joint were carried out by using a commercial FEA software ABAQUS. The stress distributions at hole-edge areas, pre-load loosening, and variation of bolt-hole clearance of CMC bolted joints under transient temperature rises were discussed for better understanding of high temperature structural behaviors. Results showed that pre-load declined with the increase of imposed hot side temperature, due to the thermal expansion mismatch between CMC and superalloy. The bolt-hole clearance for the composite plate decreased, whereas the clearance for the superalloy plate increased with the rise of temperature.展开更多
With the considerable applications of ceramic matrix composites(CMC) in aircraft engineering, the design of CMC bolted joint gains paramount attention because of its capacity to to improve load-bearing efficiency of a...With the considerable applications of ceramic matrix composites(CMC) in aircraft engineering, the design of CMC bolted joint gains paramount attention because of its capacity to to improve load-bearing efficiency of aircraft key structure. In this work, a 3 D finite element model was established to predict tensile performance and failure modes of single-lap, single-bolt 2 D C/SiC composite, and superalloy joint, which considers the progressive damage behavior of 2 D woven C/SiC composites. On the basis of the developed progressive damage model, a parametric study was carried out to illustrate the effects of bolt preload and bolt-hole clearance on mechanical behaviors of the hybrid bolted joint. It was found that the increase in the value of bolt preload made the failure load grow first and then drop, and the optimum value of bolt preload 5.00 kN generated 56.47% rise in the initial failure load and 22.83% rise in the final failure load for the bolted joint in comparison with zero preload case. As the clearance increased from 0 to 2.00%, the initial and final failure loads respectively declined by 45.88% and 24.02% for 2.00% bolt-hole clearance relative to the neat-fit case. The loss in failure loads can be reduced to compressive stress concentration around the fastening hole-edge area, leading to the appearance of earlier damages by the introduction of increasing bolt hole clearance.展开更多
文摘The article mainly talks about the characteristic of common and fine punching and the quality of shearing edge. Although the common punching has been widely applied, the quality of shearing edge is very poor. The fine punching work-piece is better in quality. But it isn’t still been widely applied, because the structure of die is complicated and the manufacture of die and using pressure machine are expensive. A new fine punching processing without burr is put forward by discussing the plastic status and press stress status of the material which influence the quality of the punching work-piece in the deformation zone, it provides the plastic status of material to determine the parameter in the new processing and presents the maximum value of plastic deformation specific energy when the material reaches the plastic status. The author has analyzed the initializing clearance and instantaneous clearance of the ordinary punching. The instantaneous clearance of the ordinary punching process is instable. By studying the author brings forward a kind of punching process which initializing clearance and instantaneous clearance are stable, that is the negative clearance fine punching process. Because of using the negative clearance fine punching process, the material of sheared distorting section comes into the plastic state. The surface quality of the punching sheared edge is advanced 1.5 times than that of the ordinary punching. The recommended value of depth of the negative clearance punching has been given in this article.
基金Sponsored by the Pre-research Foundation of Shenyang Aircraft Design and Research Institute,Aviation Industry Corporation of China(Grant No.JH20128255)。
文摘Ceramic matrix composite(CMC) and superalloy bolted joints have exhibited great potential for high temperature hot structure application in hypersonic aircraft. In service conditions, the thermal expansion mismatch between CMC and superalloy plates will cause complex thermal stress and strain distributions at hole-edge areas and assembly parameters changes of the joints under elevated temperatures. These effects might lead to early damage of joint structure, which will endanger the structural integrity and load carrying capacity of aircraft components. In the present study, transient heat transfer and thermo-structural analysis of C/SiC composite and superalloy bolted joint were carried out by using a commercial FEA software ABAQUS. The stress distributions at hole-edge areas, pre-load loosening, and variation of bolt-hole clearance of CMC bolted joints under transient temperature rises were discussed for better understanding of high temperature structural behaviors. Results showed that pre-load declined with the increase of imposed hot side temperature, due to the thermal expansion mismatch between CMC and superalloy. The bolt-hole clearance for the composite plate decreased, whereas the clearance for the superalloy plate increased with the rise of temperature.
基金Sponsored by the Pre-Research Foundation of Shenyang Aircraft Design and Research Institute,the Aviation Industry Corporation of China(Grant No.JH20128255)the National Defence Basic Research Program(Grant No.JZ20180032)the Pre-Research Foundation of Equipment Development Department of People’s Republic of China Central Military Commission(Grant No.ZJJSN20200001)。
文摘With the considerable applications of ceramic matrix composites(CMC) in aircraft engineering, the design of CMC bolted joint gains paramount attention because of its capacity to to improve load-bearing efficiency of aircraft key structure. In this work, a 3 D finite element model was established to predict tensile performance and failure modes of single-lap, single-bolt 2 D C/SiC composite, and superalloy joint, which considers the progressive damage behavior of 2 D woven C/SiC composites. On the basis of the developed progressive damage model, a parametric study was carried out to illustrate the effects of bolt preload and bolt-hole clearance on mechanical behaviors of the hybrid bolted joint. It was found that the increase in the value of bolt preload made the failure load grow first and then drop, and the optimum value of bolt preload 5.00 kN generated 56.47% rise in the initial failure load and 22.83% rise in the final failure load for the bolted joint in comparison with zero preload case. As the clearance increased from 0 to 2.00%, the initial and final failure loads respectively declined by 45.88% and 24.02% for 2.00% bolt-hole clearance relative to the neat-fit case. The loss in failure loads can be reduced to compressive stress concentration around the fastening hole-edge area, leading to the appearance of earlier damages by the introduction of increasing bolt hole clearance.
