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941.
942.
田彬 《民用飞机设计与研究》2016,(2):89
需求是商用飞机研制的基础,并贯穿于整个飞机研制的生命周期。在需求研发团队中建立一套有效的需求管理流程,使捕获、传递和更改需求的过程更规范高效。在飞机研制早期就保证需求的正确性和完整性,这样最终达到节约成本和优化进度的目的,设计出客户想要的飞机。 相似文献
943.
为了,解决较宽温域范围内特别是高温下材料的润滑问题,本文采用热压烧结方法制备了一系列含各种不同固体润滑剂(Mo、MoS2、BaF2、CaF2、BaF2/CaF2、CuO)的氧化锆基高温自润滑陶瓷复合材料.其中ZrO2(Y2O3)-Mo-BaF2/CaF2系列复合物在800 ~1 000℃表现出较低的摩擦因数,在1 000℃摩擦因数低至0.28左右,已接近工程应用的许用值;另一种ZrO2(Y2O3)-MoS2-CaF2系列复合物同SiC陶瓷球对磨时在800~1 000℃内摩擦因数为0.30 ~0.22,具有较好的摩擦磨损性能. 相似文献
944.
Aluminum alloy (Al-alloy) thin-walled (D/t > 20, diameter D, wall thickness t) bent tubes have attracted increasing applications in many industries with mass quantities and diverse specifications due to satisfying high strength to weigh ratio requirements of product manufacturing. However, due to nonlinear nature of bending with coupling effects of multiple factors, the similarity theory seems not applicable and there occurs a challenge for efficient and reliable evaluation of the bending formability of thin-walled tube with various bending specifications. Considering the unequal deformation and three major instabilities, the bending formability of thin-walled Al-alloy tube in changing tube sizes such as D and t are clarified via both the analytical and FE modeling/ simulations. The experiments of rotary draw bending are conducted to validate the theoretical models and further confirm ’size effect’ related bending formability. The major results show that (1) The anti-wrinkling capability of tube decreases with the larger D and smaller t, and the effect significance of t is larger than that of D even under rigid supports; (2) The wall thinning increases with the larger D and smaller t, and this tendency becomes much more obvious under rigid supports; (3) The cross-section deformation increases with the larger D and smaller t according to the analytical model obtained intrinsic relationship, while this tendency becomes opposite due to the nonlinear role of mandrel die; (4) The size factor D/t can be used as a nondimensional index to evaluate both the bending formability regarding the wall thinning and cross-section deformation. 相似文献
945.
Inner flange and side wrinkling often occur in rotary-draw bending process of rectangular aluminum alloy wave-guide tubes, and the distribution and magnitude of wrinkling is related to geometrical parameters of the tubes. In order to study the effects of geometrical parameters on wrinkling of rectangular wave-guide tubes, a 3D-FE model for rotary-draw bending processes of thin-walled rectangular aluminum alloy wave-guide tubes was built based on the platform of ABA-QUS/Explicit, and its reliability was validated by experiments. Simulation and analysis of the influence laws of geometrical parameters on the wave heights of inner flange and side wrinkling were then carried out. The results show that inner flange wrinkling is the main wrinkling way to rectan- gular wave-guide tubes in rotary-draw bending processes, but side wrinkling cannot be neglected because side wrinkling is 2/3 of inner flange wrinkling when b and h are smaller. Inner flange and side wrinkling increase with increasing b and h; the influence of b on side wrinkling is larger than that of h, while both b and h affect inner flange wrinkling greatly. Inner flange and side wrinkling decrease with increasing R/h; the influence of h on inner flange and side wrinkling is larger than that of R. 相似文献
946.
Auto-normalization algorithm for robotic precision drilling system in aircraft component assembly 总被引:2,自引:0,他引:2
A novel approach is proposed to detect the normal vector to product surface in real time for the robotic precision drilling system in aircraft component assembly, and the auto-normalization algorithm is presented based on the detection system. Firstly, the deviation between the normal vector and the spindle axis is measured by the four laser displacement sensors installed at the head of the multi-function end effector. Then, the robot target attitude is inversely solved according to the auto-normalization algorithm. Finally, adjust the robot to the target attitude via pitch and yaw rotations about the tool center point and the spindle axis is corrected in line with the normal vector simultaneously. To test and verify the auto-normalization algorithm, an experimental platform is established in which the laser tracker is introduced for accurate measurement. The results show that the deviations between the corrected spindle axis and the normal vector are all reduced to less than 0.5°, with the mean value 0.32°. It is demonstrated the detection method and the auto-normalization algorithm are feasible and reliable. 相似文献
947.
948.
研究了两端铰支输流管道在脉动内流作用下的参数共振问题。用数值方法分析了各种参数共振的响应曲线,其存在区域以及响应频率与脉动流频率之间的关系。研究结果发现,组合共振区域内发生两种不同的拟周期运动和组合周期运动。而且第一振型次谐波共振曲线延伸到组合共振区域。因此,在同一脉动频率下存在可发生多种不同运动的参数区域。 相似文献
949.
950.
本文简要论述了卤代烷1211和1301灭火剂的灭火机理及对臭氧层的破坏机制,介绍了几种欧美广泛采用的卤代烷1211和1301替代物的性能,并提出了评价卤代烷1211和1301灭火剂替代物的指标体系。 相似文献