In this study, shot peening is applied to the titanium alloy Ti–6Al–4V, and the surface treatment effect on fatigue life of shot-peened specimens under high cycle loading is investigated. The induced residual stress...In this study, shot peening is applied to the titanium alloy Ti–6Al–4V, and the surface treatment effect on fatigue life of shot-peened specimens under high cycle loading is investigated. The induced residual stress is measured by using the orbital hole-drilling method. Surface profilometer and optical microscopy are employed to characterize the surface roughness and morphology. The deformed microstructure layers of the shot-peened specimens are investigated by using scanning electron microscopy. Experiments reveal that the fatigue life of Ti–6Al–4V is improved by the shot peening process, and the surface pre-peening polishing. The combination of pre-and post-peening polishing treatments further improves fatigue life of Ti–6Al–4V specimens. The present work provides useful guidelines for developing more efficient shot peening strategies.展开更多
The bonnet tool polishing is a novel, advanced and ultra-precise polishing process, by which the freeform surface can be polished. However, during the past few years, not only the key technology of calculating the dwe...The bonnet tool polishing is a novel, advanced and ultra-precise polishing process, by which the freeform surface can be polished. However, during the past few years, not only the key technology of calculating the dwell time and controlling the surface form in the bonnet polishing has been little reported so far, but also little attention has been paid to research the material removal function of the convex surface based on the geometry model considering the influence of the curvature radius. Firstly in this paper, for realizing the control of the freeform surface automatically by the bonnet polishing, on the basis of the simplified geometric model of convex surface, the calculation expression of the polishing contact spot on the convex surface considering the influence of the curvature radius is deduced, and the calculation model of the pressure distribution considering the influence of the curvature radius on the convex surface is derived by the coordinate transformation. Then the velocity distribution model is built in the bonnet polishing the convex surface. On the basis of the above research and the semi-experimental modified Preston equation obtained from the combination method of experimental and theoretical derivation, the material removal model of the convex surface considering the influence of the curvature radius in the bonnet polishing is established. Finally, the validity of the model through the simulation method has been validated. This research presents an effective prediction model and the calculation method of material removal for convex surface in bonnet polishing and prepares for the bonnet polishing the free surface numerically and automatically.展开更多
By means of a coaxial apparatus, microsecond charging have been carried out with ferent ethylene glycol concentrations of ethylene pressurized water breakdown experiments with different surface roughness of electrodes...By means of a coaxial apparatus, microsecond charging have been carried out with ferent ethylene glycol concentrations of ethylene pressurized water breakdown experiments with different surface roughness of electrodes and difglycol/water mixture. The experimental results about the breakdown stress and the effective time are presented. The breakdown stress is normalized to the situation that the effective time is transformed to 1 μs and analyzed. The conclusions are as follows: (1) the breakdown stress formula is modified to E = 0.561MA^-1/10teff^-1/^NP^1/8 ;(2) the coefficient M is significantly increased by surface polishing and ethylene glycol additive; (3) it is accumulative for the capacity of improving electrical breakdown strength for surface polishing, ethylene glycol additive, and pressurization, of which pressurization is the most effective method; (4) the highest stress of 235.5 kV/cm is observed in ethylene glycol/water mixture with an ethylene glycol concentration of 80% at a hydrostatic pressure of 1215.9 kPa and is about one time greater than that in pure water at constant pressure; (5) for pressurization and surface polishing, the primary mechanism to improve the breakdown strength of water dielectric is the increase in the breakdown time delay. Research results indicate great potential in the application of the high power pulse conditioning system of water dielectric.展开更多
To strengthen the device performance with the pattern wafer by enhancing the Cu polishing rate and improve the surface roughness with the Cu lines, a new weakly alkaline chelating agent with a barrier slurry is develo...To strengthen the device performance with the pattern wafer by enhancing the Cu polishing rate and improve the surface roughness with the Cu lines, a new weakly alkaline chelating agent with a barrier slurry is developed to meet the process demand of the advanced barrier chemical mechanical planarization(CMP). This new chelating agent has a stronger chelating ability and a lower p H value than the previous generation-FA/O I chelating agent researched before. Without an unstable oxidant agent added in the polishing slurry, it is difficult to enhance the copper polishing rate during the barrier CMP. The stronger chelating ability of the new chelating agent could increase the copper polishing rate along with controlling the Cu/Ta/TEOS removal rate selectivity to meet the requirements of the IC fabrication process. Thus it has solved the problem of excessive roughness due to the lower polishing rate, avoiding reducing the device performance with the pattern wafer. The new chelating agent with its lower p H value could make it possible to protect the low-k dielectric under the barrier layer from structurally breaking. The CMP experiment was performed on the 12 inch MIT 854 pattern wafers with the barrier slurry containing the new weakly alkaline chelating agent. By the DOE optimization, the results indicate that as the new chelating agent concentration in the slurry was up to 2.5 m L/L, the copper polishing rate is about 31.082 nm/min.Meanwhile, the wafer surface has a rather low roughness value of 0.693 nm(10×10 μm), the correction ability with the above slurry is adapted to the next generation barrier CMP and the k value of the low-k dielectric seems to have no k-shift. All the results presented show that the new weakly alkaline chelating agent with its superior performance can be used for the advanced barrier CMP.展开更多
基金the Aerospace Program and Agency for Science,Technology and Research,Singapore(A*STAR)
文摘In this study, shot peening is applied to the titanium alloy Ti–6Al–4V, and the surface treatment effect on fatigue life of shot-peened specimens under high cycle loading is investigated. The induced residual stress is measured by using the orbital hole-drilling method. Surface profilometer and optical microscopy are employed to characterize the surface roughness and morphology. The deformed microstructure layers of the shot-peened specimens are investigated by using scanning electron microscopy. Experiments reveal that the fatigue life of Ti–6Al–4V is improved by the shot peening process, and the surface pre-peening polishing. The combination of pre-and post-peening polishing treatments further improves fatigue life of Ti–6Al–4V specimens. The present work provides useful guidelines for developing more efficient shot peening strategies.
基金Supported by Young Teacher Independent Research Subject of Yanshan University of China(Grant No.15LGA002)
文摘The bonnet tool polishing is a novel, advanced and ultra-precise polishing process, by which the freeform surface can be polished. However, during the past few years, not only the key technology of calculating the dwell time and controlling the surface form in the bonnet polishing has been little reported so far, but also little attention has been paid to research the material removal function of the convex surface based on the geometry model considering the influence of the curvature radius. Firstly in this paper, for realizing the control of the freeform surface automatically by the bonnet polishing, on the basis of the simplified geometric model of convex surface, the calculation expression of the polishing contact spot on the convex surface considering the influence of the curvature radius is deduced, and the calculation model of the pressure distribution considering the influence of the curvature radius on the convex surface is derived by the coordinate transformation. Then the velocity distribution model is built in the bonnet polishing the convex surface. On the basis of the above research and the semi-experimental modified Preston equation obtained from the combination method of experimental and theoretical derivation, the material removal model of the convex surface considering the influence of the curvature radius in the bonnet polishing is established. Finally, the validity of the model through the simulation method has been validated. This research presents an effective prediction model and the calculation method of material removal for convex surface in bonnet polishing and prepares for the bonnet polishing the free surface numerically and automatically.
基金National 863 Project of China (No. 807-2020, 803-5051)
文摘By means of a coaxial apparatus, microsecond charging have been carried out with ferent ethylene glycol concentrations of ethylene pressurized water breakdown experiments with different surface roughness of electrodes and difglycol/water mixture. The experimental results about the breakdown stress and the effective time are presented. The breakdown stress is normalized to the situation that the effective time is transformed to 1 μs and analyzed. The conclusions are as follows: (1) the breakdown stress formula is modified to E = 0.561MA^-1/10teff^-1/^NP^1/8 ;(2) the coefficient M is significantly increased by surface polishing and ethylene glycol additive; (3) it is accumulative for the capacity of improving electrical breakdown strength for surface polishing, ethylene glycol additive, and pressurization, of which pressurization is the most effective method; (4) the highest stress of 235.5 kV/cm is observed in ethylene glycol/water mixture with an ethylene glycol concentration of 80% at a hydrostatic pressure of 1215.9 kPa and is about one time greater than that in pure water at constant pressure; (5) for pressurization and surface polishing, the primary mechanism to improve the breakdown strength of water dielectric is the increase in the breakdown time delay. Research results indicate great potential in the application of the high power pulse conditioning system of water dielectric.
基金Project supported by the Special Project Items No.2 in National Long-Term Technology Development Plan,China(No.2009ZX02308)the Natural Science Foundation of Hebei Province,China(No.E2014202147)
文摘To strengthen the device performance with the pattern wafer by enhancing the Cu polishing rate and improve the surface roughness with the Cu lines, a new weakly alkaline chelating agent with a barrier slurry is developed to meet the process demand of the advanced barrier chemical mechanical planarization(CMP). This new chelating agent has a stronger chelating ability and a lower p H value than the previous generation-FA/O I chelating agent researched before. Without an unstable oxidant agent added in the polishing slurry, it is difficult to enhance the copper polishing rate during the barrier CMP. The stronger chelating ability of the new chelating agent could increase the copper polishing rate along with controlling the Cu/Ta/TEOS removal rate selectivity to meet the requirements of the IC fabrication process. Thus it has solved the problem of excessive roughness due to the lower polishing rate, avoiding reducing the device performance with the pattern wafer. The new chelating agent with its lower p H value could make it possible to protect the low-k dielectric under the barrier layer from structurally breaking. The CMP experiment was performed on the 12 inch MIT 854 pattern wafers with the barrier slurry containing the new weakly alkaline chelating agent. By the DOE optimization, the results indicate that as the new chelating agent concentration in the slurry was up to 2.5 m L/L, the copper polishing rate is about 31.082 nm/min.Meanwhile, the wafer surface has a rather low roughness value of 0.693 nm(10×10 μm), the correction ability with the above slurry is adapted to the next generation barrier CMP and the k value of the low-k dielectric seems to have no k-shift. All the results presented show that the new weakly alkaline chelating agent with its superior performance can be used for the advanced barrier CMP.