The aim of this study is to actively explore the quantitative measurement of residual stress of trapezoidal internal threads after extrusion processing. In this paper, innovative stress test ...specimens of the Ti-6Al-4V alloy disc with a diameter of 86 mm and a thickness of 20 mm were designed, and vibration extrusion tapping was carried out with a Tr14*2 extrusion tap in the center of the disc. Then, based on the elastic principle and the linear superposition principle, the incremental slicing method or crack flexibility method was applied to retrieve the residual stress distribution from the strain measurement. The stress distributions along the axial direction of the threaded hole and along the tangential and normal directions of the threaded hole were measured. The redistribution law of internal residual stress of extruded internal threaded parts was explored and studied, which provides a basis for studying the fatigue resistance of materials. In addition, the three-dimensional finite element method was used innovatively to calculate the stress flexibility factor of circular pie specimens with finite boundary constraints as not used the previous two-dimensional plane strain approximation.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Clear medical images can effectively help doctors to make pathological analysis and diagnosis.Aiming at the problem of image blur caused by camera unfocused during the process of medical image ...acquisition, this paper proposes a new image deblurring network based on the deblur generative adversarial networks(DeblurGAN).The network uses channel attention structure in Generator and extracts details effectively.During the process of image up-sampling, we use the method of bilinear interpolation with a convolution layer instead of transpose convolution, which removes the checkerboard effects.The model is trained by the combination of adversarial loss and content loss to obtain clear image.The experimental results show that the network achieves better performance in both PSNR and SSIM compared with DeblurGAN.
FSJ process of 7022 aluminum alloy was simulated by the finite element method. The residual stress and deformation laws were obtained by the simulation. The simulation results were verified correctly ...by the experiments. The simulation shows that the residual stress is mainly concentrated in the jointing region. The maximum tensile stress is located in the middle of jointing region. The residual compressive stress is located in the ends and other parts of jointing region. The deformation in the advancing side in the direction of vertical the jointing region is greater than that in the retreating side. The tilting in the key eye side is higher than that in the staring side. The whole deformation is such as the saddle shape.
The NiCoCrAlY coatings strengthened by three nano-particles with the same addition were prepared on a Ni-base super alloy using laser cladding technique. The dry frictional wear behaviors of the ...coatings at 500 °C in static air were investigated. The comparison was made with the coating without nano-particles. The results show that the wear mechanism of the NiCoCrAlY coatings with nano-particles, like the coating without nano-particles, is the delamination wear due to the strong plastic deformation and oxidative wear. However, the frictional coefficient of the coatings increases and presents the decrease trend with the increase of sliding distance after adding nano-particles. Moreover, the wear rate of the coatings with nano-particles is only 34.0%-64.5% of the coating without nano-particles. Among the three nano-particles, the improvement of nano-SiC on the high temperature wear resistance of the coating is the most significant.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
TG1; The nanometer Al2O3 dispersion strengthened NiCoCrAlY high-temperature protective coatings by crosscurrent CO2 laser on Ni-based superalloy GH4033 were produced. Microscopic morphologies, phase ...constitutions of cladding coatings and distribution of nano-Al2O3 particles were examined using SEM and XRD. The results show that the interface grains, after adding proper nano-Al2O3, grow from epitaxial to non-epitaxial shape gradually, and the columnar dendrites become thinner and denser with cellular shape. Cracks in the substrate close to the interface are eliminated. Moreover, dispersive nano-Al2O3 particles mainly distribute around cellular substructure and on grain-boundaries, which prevents the diffusion of alloying elements and restrains the formation of new phase. There is a critical value of nano-Al2O3 addition, and the most suitable content of nano-Al2O3 is 1% (mass fraction) in this experimental conditions. The "nanometer effect" of nano-Al2O3 particles plays an important role in the improvement of coating microstructure.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Conventional cold extrusion is generally considered to be less practical for trapezoidal threads, requiring a relatively large form tapping torque. The machining of it is always based on cutting, but ...the actual demands of high strength and long life have brought this process to its limits. These requirements drove the present work, which proposes a new process for the fabrication of a Ti-6Al-4V-alloy trapezoidal thread using low-frequency torsional vibration extrusion (LTVE) through a forming tap. A semi-analytical model of torsional vibration extrusion with friction was established by solving the problem of mechanical friction and slip-line field. The influence of low-frequency torsional vibration on the form tapping torque was studied, and the total amounts were determined quantitatively. The conclusion shows that the total tapping torque was composed of the positive pressure load and the friction load on the forming tap. The friction load was generated by the tool/workpiece friction, which is the largest component, accounting for more than 90 %. The introduction of vibration can reduce the friction in the thread form tapping so as to obtain high rheological properties, which is applicable for the low-frequency stage. Finally, a mechanical LTVE tapping excitation device was proposed based on this process method, and an experimental prototype that can meet the requirements of titanium alloy trapezoidal thread machining was developed. Experimental verification indicated that the LTVE forming process had reduced the total form tapping torque. It also proved the method’s overall reliability and effectiveness and the underlying insights needed to guide the thread manufacturing.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The hardness, elastic modulus, and scratch resistance of a glass-ceramic rigid substrate were measured by nanoindentation and nanoscratch, and the fracture toughness was measured by indentation using ...a Vickers indenter. The results show that the hardness and elastic modulus at a peak indentation depth of 200 nm are 9.04 and 94.70 GPa, respectively. These values reflect the properties of the glass-ceramic rigid substrate. The fracture toughness value of the glass-ceramic rigid substrate is 2.63 MPa？m1/2. The material removal mechanisms are seen to be directly related to normal force on the tip. The critical load and scratch depth estimated from the scratch depth profile after scratching and the friction profile are 268.60 mN and 335.10 nm, respectively. If the load and scratch depth are under the critical values, the glass-ceramic rigid substrate will undergo plastic flow rather than fracture. The formula of critical depth of cut described by Bifnao et al. is modified based on the difference of critical scratch depth
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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