压缩空气弹射广泛应用于航空航天、舰船、陆基武器系统等领域,具有弹射速度快、无需热防护、可重复利用、安全环保及通用性能好等优势.通过对大量文献进行分类总结,概述了压缩空气弹射的应用研究领域,简要分析了压缩空气弹射在各行业内应用过程中存在的关键技术及发展前景.研究表明:研制高效、小型化的压缩空气弹射系统是各行业各领域发展的必然趋势,相关结果为压缩空气弹射的应用与研究提供有利参考.

某低温风洞弯刀采用00Cr12Ni10MoTi马氏体时效不锈钢制造(代号:S03).分别采用构筑成形和三联特冶(真空感应熔炼+真空自耗电弧熔炼+电渣重熔)工艺路线研究了10 t级S03钢小试件钢锭制备工艺.通过X射线衍射(XRD)、扫描电镜(SEM)和拉伸、冲击等评价方法,分别研究了冶炼和热处理工艺对S03钢组织及力学性能的影响.研究结果表明,构筑成形和三联特冶工艺均可实现10 t级S03钢锭的制备,两步750 ℃固溶和500 ℃时效工艺可实现S03钢较好的综合力学性能,工艺研究结果为某低温风洞百吨级弯刀钢锭制备提供了技术支撑.

Fe–10Cr–10Ni cryogenic maraging steel is one of the key candidate materials applied in harsh cryogenic condition due to its high strength and good cryogenic toughness. In this study, the effect of aging temperature on its microstructure and mechanical properties was systematically studied based on austenite reversion and nano-precipitation. It shows that a desirable combination of high strength (834 MPa, 25 °C) and excellent cryogenic impact toughness (164 J, −196 °C) can be obtained by aging treatment at 500 °C. Multi-scale characterizations were conducted to reveal the microstructure characteristics of the steel. It was found that obvious film-like reversed austenite nucleate and grow at the high-angle grain boundaries of martensite matrix in the steel aged at 500 °C, whereas the higher aging temperature resulted in a larger content of blocky reversed austenite in martensite blocks. Austenite reversion mechanism was proposed based on the double-spherical-cap model and diffusion kinetics of Ni element. Besides, it was found that the precipitation sites of Ti-rich particles are not only distributed in matrix but also located at the dislocations, and they were identified as the clusters of Ni3Ti precipitates. Finally, the origin of the above cryogenic toughness includes the transformation-induced plasticity (TRIP) effect from the soft film-like austenite, higher density of high angle grain boundaries of martensite and fine nanoscale precipitates. Moreover, the precipitation strengthening from the clusters of Ni3Ti precipitates contributes to the high strength of the steel aged at 500 °C.

The evolution of heterogeneous microstructure and mechanical properties of a 12Cr–10Ni–Mo–Ti maraging steel was investigated at different aging temperatures. As the aging temperature increases, more reversed austenite forms with the recovery of martensite matrix. When aging temperature is up to 560 °C, more lath-like reversed austenite coalesces together and leads to the formation of martensite and austenite dual-phase microstructure. Fine η-Ni3(Ti, Al) particles initially precipitate at 440 °C and grow up with increased aging temperature. Notably, it was found that η-precipitates can be encompassed in reversed austenite at 500 °C. Thermodynamic calculations further verify the austenite reversion, and nanoprecipitation can occur independently of each other though there is competition of Ni element. However, it leads to the coarsening and dissolution of η-precipitates as the aging temperature further increases. The desirable heterogeneous microstructure of the aged martensite matrix, soft reversed austenite and stable η-precipitates at 500 °C contributes to a high yield strength (~ 1 GPa, 25 °C; ~ 1.4 GPa, -196 °C) and a reasonable cryogenic impact toughness (~ 60 J, − 196 °C), which is mainly ascribed to the precipitation strengthening of η-precipitates, transformation-induced plasticity (TRIP) toughening effect from the lath-like reversed austenite and the increased misorientation toward high-angle grain boundary.

针对弯刀传统锻造成形工艺需要复杂的工装、 大吨位钢锭和较多锻造火次,且经济性较差、 质量风险难以控制等难题,设计了配套引导工装和中频感应线圈,采用热推弯成形工艺研究不同材质、 不同缩比下的弯刀成形工艺,并获得了理想的效果.热推弯成形过程中,弯刀成形平稳、 速度快且精度高,力学性能满足要求,并且所需毛坯吨位小,具有较大的技术和经济优势.同时,在1:6和1:2弯刀缩比件的工艺研究中所积累的热推弯成形工艺各环节的关键工艺参数,可为1:1全尺寸弯刀热推弯成形提供技术支撑,为弯刀成品件的成形探索了一条新途径.

使用X射线衍射(XRD)、扫描电镜(SEM)、电子背散射衍射(EBSD)、透射电镜(TEM)和拉伸和冲击实验等手段,研究了时效温度对00Cr12Ni10MoTi马氏体时效不锈钢的组织和力学性能的影响.结果 表明:随着时效温度的升高,实验钢的强度逐渐提高,析出强化效应明显增强.在500℃时效后基体中析出大量棒状Ni3Ti,实验钢的强度达到峰值.随着时效温度的升高,实验钢的室温和低温冲击韧性衰减,在400℃时效后低温(-196℃)冲击功出现最低值51J.时效温度升高到500℃后,实验钢的冲击韧性回升,因为马氏体基体中生成的逆转变奥氏体抑制了裂纹萌生并缓解其扩展.在500℃时效产生了Ni3Ti析出强化效应和逆变奥氏体韧化效应,使实验钢具有良好的强韧性匹配.

The influence of the different heat treatment processes on the 304L austenitic stainless steel organization and performance is studied.Through the 304L austenitic stainless steel quench processing by heating up to 570 ℃,keep 1 hour time,then cool the air.It is concluded that the microstrueture and mechanical property changes slightly,and the impact toughness does not change significantly,which could eliminate welding residual stress by 40％.

In order to satisfy the plane motion control of wheeled mobile robot,the plane geometry theory was investigated.A planar motion model as the basis for the study of linear and circular trajectory tracking control algorithm was established.A navigation round was presented to synthesize an angle by calculating the deviation of both angle and position between the robot's real-time location and the target trajectory.Secondly,a PID controller to achieve the intended trajectory tracking was made.The linear and circular trajectory tracking algorithm was practically applied in robotics.The experimental results show that the error is controlled in ±1 cm.

Introduces the technical requirement of wind tunnel heat exchanger.Then illustrates the advantages and disadvantages of heat pipe technology.Combined with the design of heat exchanger(structure parameters) of one wind tunnel,makes comparison of the heat pipe exchanger and the others,analyzes the advantages of heat pipe exchanger used for wind tunnel.