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431.
432.
Influences of milling and grinding on machined surface roughness and fatigue behavior of GH4169 superalloy workpieces 总被引:4,自引:4,他引:0
Surface topography of superalloy GH4169 workpieces machined by milling and grinding is different significantly. Meanwhile, surface roughness, as one of the main indicators of machined surface integrity, has a great influence on the fatigue behavior of workpieces. Based on analyzing the formation mechanism and characteristics of surface roughness utilizing different machining processes and parameters, the machined surface roughness curve can be decoupled into two parts utilizing frequency spectrum analysis, which are kinematic surface roughness curve and stochastic surface roughness curve. The kinematic surface roughness curve is influenced by machining process,parameters, geometry of the cutting tool or wheel, the maximum height of which is expressed as R'_z.By subtracting the kinematic part from the measurement curve, the stochastic surface roughness curve and its maximum height R'_zcan be obtained, which is influenced by the defects of cutting tool edge or abrasive grains, built-up edges(BUE), cracks, high frequency vibration and so on. On the other hand, the results of decoupling analysis of surface roughness curves indicate that Raand Rz values of milling GH4169 are 2–5 times and 1–3 times as high as those of grinding, while R'_zvalue of milling is 13.85%–37.7% as high as that of grinding. According to the results of fatigue life tests of specimens machined by milling and grinding, it can be concluded that fatigue behavior of GH4169 decreases with the increase of R'_zmonotonically, even utilizing different machining processes. 相似文献
433.
《中国航空学报》2021,34(4):508-517
Ultrasonic cavitation modification (UCM) employs cavitation effect to induce strong plastic deformation on the material surface and improve surface properties. To explore the surface strengthening and grain refinement of materials by UCM, the UCM orthogonal experiments of AZ31B magnesium alloy were carried out in water and kerosene, respectively. The effects of ultrasonic amplitude, distance from the sample, and processing time on Vickers hardness and grain size of the material were studied. The results showed that the Vickers hardness of samples increased to 1.5–3 times after UCM in water, which was 23.77–48.19% higher than that in kerosene. The metallographic observation indicated the grains on the surface of AZ31B were refined after UCM. The maximum fluctuation of grain size on the material surface was not more than 10 μm after UCM in water, and most of them were concentrated between 1.5 μm and 2.5 μm, while the former was more than 40 μm and the latter were concentrated between 2 μm and 10 μm in kerosene. This reflected that the grain refinement effect of UCM in water was better than that in kerosene. Ultrasonic cavitation can be used as a benign means to improve the surface properties of materials. 相似文献
434.
为改善碳纤维增强聚醚醚酮复合材料(CF/PEEK)在铣削加工时所产生的毛刺、分层以及表面凹坑等缺陷,采用超声辅助铣削的加工方式分别沿0°、45°、90°、135°四种纤维方向角对CF/PEEK进行实验,并与传统铣削进行对比研究。结果表明:超声辅助铣削与传统铣削相比,切削力更小且加工质量更优。沿90°纤维方向角对试件进行超声辅助铣削,切削力、表面粗糙度和毛刺高度降幅最显著,分别降低了16.79%、28.9%和71.9%。而且在相同的加工参数下,超声辅助铣削与传统铣削相比,能够有效地改善表面凹坑、分层等表面缺陷。 相似文献
435.
《中国航空学报》2023,36(4):523-537
Electrochemical machining (ECM) has emerged as an important option for manufacturing the blisk. The inter-electrode gap (IEG) distribution is an essential parameter for the blisk precise shaping process in ECM, as it affects the process stability, profile accuracy and surface quality. Larger IEG leads to a poor localization effect and has an adverse influence on the machining accuracy and surface quality of blisk. To achieve micro-IEG (<50 μm) blisk finishing machining, this work puts forward a novel variable-parameters blisk ECM strategy based on the synchronous coupling mode of micro-vibration amplitude and small pulse duration. The modelling and simulation of the blisk micro-IEG machining have been carried out. Exploratory experiments of variable-parameters blisk ECM were carried out. The results illustrated that the IEG width reduced with the progress of variable parameter process. The IEG width of the blade’s concave part and convex part could be successfully controlled to within 30 μm and 21 μm, respectively. The profile deviation for the blade’s concave surface and convex surface are 49 μm and 35 μm, while the surface roughness reaches Ra = 0.149 μm and Ra = 0.196 μm, respectively. The profile accuracy of the blisk leading/trailing edges was limited to within 91 μm. Compared with the currently-established process, the profile accuracy of the blade’s concave and convex profiles was improved by 50.5 % and 53.3 %, respectively. The surface quality was improved by 53.2 % and 50.9 %, respectively. Additionally, the machined surface was covered with small corrosion pits and weak attacks of the grain boundary due to selective dissolution. Some electrolytic products were dispersed on the machined surface, and their components were mainly composed of the carbide and oxide products of Ti and Nb elements. The results indicate that the variable-parameters strategy is effective for achieving a tiny IEG in blisk ECM, which can be used in engineering practice. 相似文献
436.
437.
《中国航空学报》2023,36(7):129-146
In the quest for decreasing fuel consumption and resulting gas emissions in the aeronautic sector, lightweight materials such as Carbon Fiber Reinforced Polymers (CFRPs) and Ti-6Al-4V alloys are being used. These materials, with excellent weight-to-strength ratios, are widely used for structural applications in aircraft manufacturing. To date, several studies have been published showing that the use of metalworking fluids (MWFs), special tool geometries, or advanced machining techniques is required to ensure a surface quality that meets aerospace component standards. Conventional MWFs pose a number of environmental and worker health hazards and also degrade the mechanical properties of CFRPs due to water absorption in the composite. Therefore, a transition to more environmentally friendly cooling/lubrication techniques that prevent moisture problems in the composite is needed. This research shows that lubricated LCO2 is a viable option to improve the quality of drilled CFRP and titanium aerospace components compared to dry machining, while maintaining clean work areas. The results show that the best combination of tool geometry and cooling conditions for machining both materials is drilling with Brad point drills and lubricated LCO2. Drilling under these conditions resulted in a 90 % improvement in fiber pull-out volume compared to dry machined CFRP holes. In addition, a 33 % reduction in burr height and a 15 % improvement in surface roughness were observed compared to dry drilling of titanium. 相似文献
438.
Active and passive compliant force control of ultrasonic surface rolling process on a curved surface
Ultrasonic surface rolling process(USRP) is one of the effective mechanical surface enhancement techniques. During the USRP, unstable static force will easily do harm to the surface quality. In order to achieve a higher surface quality on the part with a curved surface, an active and passive compliant USRP system has been developed. The compliant USRP tool can produce the natural obedience deformation along the part surface. Force control based on the fuzzy Proportional-integral-derivative(PID) ... 相似文献
439.
《中国航空学报》2023,36(3):471-481
The thread rolling process has been widely applied to manufacture high-performance thread parts. In this process, the evolutions of surface and subsurface are frequently introduced, which affect the working performance of manufactured parts. In this study, an axial-infeed thread rolling process (ATRP) is employed, and the macro-meso surface characteristics under different lubrications and operating conditions are investigated. Moreover, the distributions of microstructure and hardness on the subsurface of formed tooth are analyzed in detail, along with the study of stress state and yield strength change. It is found that the MoS2 grease is more effective in reducing the surface roughness and defects than the lubrication oil and water-base graphite during the ATRP process. Increasing rolling speed improves the quality of surface morphology and can reduce the surface roughness. On the subsurface of bottom and flank, intensive shear stress occurs in a narrow region, resulting in the elongation and refinement of the grains and increasing the low angle grain boundary fraction. Based on the grain size and plastic strain, the yield strength is predicted. The maximum yield strength and hardness on the bottom of formed tooth are improved by 41.2% and 39.4%, respectively. 相似文献
440.
Xingying ZHOU Henan LIU Tianyu YU Ruiyang GUO Guangzhou WANG Yazhou SUN Mingjun CHEN 《中国航空学报》2023,36(7):194-212
High-precision turning(HPT) is a main processing method for manufacturing rotary high-precision components, especially for metallic parts. However, the generated vibration between tool tip and workpiece during turning may seriously deteriorate the surface integrity. Therefore,exploring the effect of vibration on turning surface morphology and quality of copper parts using3D surface topography regeneration model is crucial for predicting HPT performance. This developed model can update the machin... 相似文献