The blade is a crucial component in an aero engine. In electrochemical machining of blades, the shaping law of the leading/trailing edge is intricate because of the complexity of the flow field and ...electric field distributions at these locations. This paper researches the formation of the leading/trailing edge. The dissolution process of the leading/trailing edge is simulated using an initial cathode and then its forecasted profile is obtained. The cathode is then adjusted according to the deviations between the forecasted profile and the model. Meanwhile, a coefficient between the deviations and the corrected value of the cathode is obtained after optimization simulation and the optimal value is about 1.17. Then, an optimal cathode is acquired by using the optimal coefficient. In addition, the effects of the thermal and hydrogen generation are also considered. The temperature increases to 8.28 K and the bubble rate increases to 25.30% at the electrolyte outlet. Furthermore, verification experiments are performed with the optimal cathode. The results show that the margin edges are formed and the accuracy is 0.13 mm of the leading edge, while the allowance of the profile at the electrolyte outlet is larger than that at the inlet, which means that the bubble rate is dominant in the inter-electrode gap. The results indicate that the design method for the leading/trailing edge is appropriate and can be used for manufacturing other complex components such as blisks and diffusers.
Compared with the laser shock peening, the warm laser shock peening has been demonstrated to get a stable compressive stress distribution under heating and cyclic loading, which is mainly due to warm ...laser shock peening combined with the advantages of laser shock peening and dynamic strain aging. The surface morphology evaluation of warm laser shock peening was investigated systematically in this work, the GH4169 nickel-base super-alloy is selected as the material with which to conduct experiments of laser shock peening and warm laser shock peening. It can be found that there are a lot of surface ripples appearing after the treatment of warm laser shock peening, which is different from the surface reliefs by the treatment of laser shock peening. Under high temperature and strain rate, δ phase transformed into γ″ phase. Simultaneously, compared with the δ phase of the larger grain size, the grain size of γ″ phase is much smaller, and is unable to form the surface relief. Warm laser shock peening produced a higher dislocation density and more stabilized dislocations that are pinned by the “Cottrell Clouds” formed by γ″ phase, which can inhibit the residual stress failure at the high temperature-alternating load.
Laser shock peening is one of the best method to enhance the mechanical and fatigue properties of titanium aluminide alloys. Most research depends on the pressure model produced by Professor Fabrro, ...based on Von-Mise stress yield standard, when the pressure is 2 Hugoniot elastic limit (HEL), the plastic deformation reaches the maximum limit and when the pressure is 2.5HEL The stress release from the edge of laser shock area, This research discussed the titanium aluminide alloys surface mechanical and fatigue properties after reducing the pressure of laser shock and inducing the repetitions of laser shock properly. When the pressure reached HEL the material began plastic deformation, in the experiment environment there are several factors affect the results, so the pressure should be more than 1HEL and less than 2HEL-2.5HEL. As the same repetitive times the effective of 2HEL-2.5HEL pressure is better than the less pressure but with the repetitive times rise the 2HEL-2.5HEL pressure specimens would be cracked and the less pressure specimens mechanical and fatigue properties still increase. The results show that with inducing the repetitions and reducing the pressure the material surface hardness improved nearly 25% and the fatigue life increase nearly 40% in high fatigue cycle, the microstructure is similar but the less pressure more repetitive times specimens contains dislocation cells. It indicates that with 2HEL-2.5HEL pressure (the maximum plastic deformation) the mechanical and fatigue properties reached to its peak after 3 times LSP and with 1.5 HEL pressure 8 times repetitive laser shock can reach to the saturate limit of the material itself, that means with less pressure and more repetitive laser shock is more accurately to get close to the saturate limit of the material.
In most laser shock process experiments, the traditional typical laser path is usually in use. The traditional typical laser path is easy to control the laser beam and the multi-axis machining ...platform, effective to improve the material surface properties. The traditional laser path moves from the start point and goes through straight line and turn back in the next row then continue to full fill the machining area. However, the surface stress distribute is unbalance. The material surface would be destroyed when the outside stress larger than limit of any axis. To make the stress distribution more reasonable, the manuscript discuss the reasons caused the phenomenon.
Blades are key components in modern aero engines. Their leading and trailing edges are extremely difficult to machine using electrochemical machining (ECM) because of their small thickness and radius ...of curvature and their marginal location. Traditional ECM of blades requires gaps between the convex part cathode and concave part cathode at the leading and trailing edges to allow passage of electrolyte. The presence of these gaps may lead to large variations in electric field intensity at the end of the machining process as the leading and trailing edges are forming. This paper proposes a new design of cross-structural cathodes to decrease the dynamic variation of the electric field at marginal locations. A mathematical model of material removal is established, taking account principally of the electric field factor. The forming process of the leading edge is simulated, and changes in electric field intensity during the final stages of the process are analyzed. The simulation results show that the maximum fluctuation in the electric field intensity at the leading edge is 62.42% when a conventional cathode is used, but only 30.51% with cross-structural cathodes. Experiments are conducted to compare the performance of conventional and cross-structural cathodes. The results show that, in comparison with conventional cathodes, the use of cross-structural cathodes reduces variations in machining current in the forming stage of margin profiles and leads to more accurate repeatability of the process.
The combination of additive manufacturing and conventional metal forming processes provides the possibility for improvements of forming efficiency and flexibility. Substrate preheating is an ...implementable technique to improve the interface adhesion properties of the hybrid forming method. The present experiment investigates the adhesion of additive manufactured 316 L steel on P20 and 1045 steel substrates under two substrate temperatures, and the geometrical characterization, interfacial microstructure and mechanical property of the hybrid specimens were compared. As a result, it was found that the ratio of deposition height to the width was reduced and the width was increased under substrate preheating. Tensile results show that the ultimate strength of 1045 and 316 L hybrid specimens was obviously increased, while the properties of hybrid specimens P20 and 316 L were similar, under different substrate temperature conditions. For the hybrid specimens with the metallurgically bonding characteristic, the tensile properties can reach the level of 316 L depositioned specimens fabricated by laser metal deposition (LMD). Furthermore, substrate preheating had little effect on the microstructure of the laser metal deposition zone, and significant influence on the microstructure of the heat affected zone, which was reflected in the difference of the hardness distribution.
Laser shock peening (LSP), as an innovative surface treatment technology, can effectively improve fatigue life, surface hardness, corrosion resistance, and residual compressive stress. Compared with ...laser shock peening, warm laser shock peening (WLSP) is a newer surface treatment technology used to improve materials’ surface performances, which takes advantage of thermal mechanical effects on stress strengthening and microstructure strengthening, resulting in a more stable distribution of residual compressive stress under the heating and cyclic loading process. In this paper, the microstructure of the GH4169 nickel superalloy processed by WLSP technology with different laser parameters was investigated. The proliferation and tangling of dislocations in GH4169 were observed, and the dislocation density increased after WLSP treatment. The influences of different treatments by LSP and WLSP on the microhardness distribution of the surface and along the cross-sectional depth were investigated. The microstructure evolution of the GH4169 alloy being shocked with WLSP was studied by TEM. The effect of temperature on the stability of the high-temperature microstructure and properties of the GH4169 alloy shocked by WLSP was investigated.
To deal with the oblique laser shock situation for some complex structure workpieces, the shock wave pressure model is established for different shock angles and different laser polarization states ...according to the laser parameters. The laser energy loss when passing through the water layer is calculated in this model. The finite element method is applied to analyze the distribution of residual stress in surface and depth directions after LSP. The surface topography and residual stress are measured by experiment at different shock angles and different laser polarization states. The results show that the pit depth gradually decreases as the shock angle increases, and the pit depth of orthogonal polarized laser shock peening is smaller than the parallel polarized laser shock peening. The degree of difference is especially obvious when shock angle exceeds 30°.With the increase of the shock angle, the surface residual stress increases first and then decreases. The influence depth of compressive residual stress decreases with the increase of the shock angle. The residual stress changes for the orthogonal polarized laser oblique shock with the angle is in keeping with parallel polarized laser oblique shock, but the rate of the residual stress reduce is faster. The residual stress hole problem can be solved by choosing the appropriate shock angle in some cases.
•We study a new double spiral tool-path generation algorithm for HSM.•Machining process can be achieved without cutter lifting and retraction motion exists.•We present segmentation rules to improve ...the uniformity of path intervals.
Complex pockets have been widely used in industry for the production. At present, the basic forms of tool-path which most commercial CAM software systems used are still limited to direction-parallel and contour-parallel offset. If the pocket contains multiple islands, the tool-path will include many cutter lifting and retraction motions. In this paper, we propose a new double spiral tool-path generation and linking method for complex pockets with multiple islands which can be used for high speed machining. We also provide segmentation rules to divide surface for further improving machining accuracy and efficiency. Taking into account the path interval, step length and other processing parameters, precise milling can be achieved without cutter lifting and retraction operations to ensure optimal processing performance and reduce processing time. The proposed algorithm has been implemented and tested bounded by 2D straight lines and circular arcs of various shapes, and validated successfully through the actual machining of a complicated pocket. The results indicate that this method is superior to other existing machining methods, and it can realize high speed machining of complicate-shaped pocket based on parametric surface with multiple islands.
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