For new medical β titanium implants, the surface micro texture processing technology is a difficult problem. To solve this problem, a new method of ultrasonic elliptical vibration cutting (UEVC) is adopted in this paper. The mechanism of material removal in ultrasonic elliptical vibration cutting is explored for different cutting paths. By means of simulation and experimentation, the material removal mechanism of ultrasonic elliptical vibration cutting medical β titanium alloy is revealed with respect to the aspects of cutting deformation, stress distribution, force and thermal variation, and chip formation mechanism. The results show that: (1) The cutting temperature and cutting force in the UEVC process obey the law of periodic change, and the maximum point of cutting force appears ahead of the maximum point of cutting temperature. (2) The material removal process of UEVC is a “press–shear–pull” composite cutting process. The tool squeezes the material to form the chips. Under the action of high temperature, the material is removed by adiabatic shear. (3) The difference of UEVC paths will affect the removal mode of materials and form different surface morphology. (4) For different cutting paths, compressive stress is distributed at the lowest point of the machining pit, and tensile stress is distributed at the protrusion position.
The pneumatic conveying process of fine particles through filters was studied by CFD-DEM simulation method. The porous media model and porous structure were used to simulate the airflow state and the blocking effect of fine particles when they flowed through the filter. Under different particle feed rates and initial particle velocities, the effects of the plugging rate and settling velocity in pleated filters were analyzed, and the effect of particle deposition height on fluid zone was studied. The results showed that particles should avoid the feed rate of 250–750 g/s and choose the initial particle velocity of 3–6 m/s to achieve lower plugging rate and faster settling velocity. The position of the filter should avoid the particle inlet to avoid the increase of non-uniformity. Timely cleaning of particles in the filter box can improve the filtering performance.
The thermal shock load has an important effect on the stability of thin-walled blades under high-speed operation of aircraft engines. According to the actual working conditions, the linear interpolation distribution of blade temperature is obtained by the numerical fitting method. A thermal buckling model is built to obtain the linear and nonlinear modal response of the blade through the finite element method. The results show that the blade stiffness changes under the influence of thermal buckling and the obvious torsional deformations are produced along the radial direction of the blade. Meanwhile, the largest deformation of about 1.3 mm and stress of 81 Mpa occurs on the blade tip for both the linear and nonlinear response. The buckling stress distribution and critical load factor of thermal buckling are also calculated, consistent with the rubbing part of blade. The changing radial length is the main reason for the distance reduction between the blade and casing, causing more probability of friction impact. Therefore, reasonable local thermal buckling technology is helpful to improve the design level of thermal-shock loaded blades.
The manufacturing of precise surface microstructures with low cost is needed for surface texturing-based surface engineering. In this paper, a device for the fabrication of surface microgroove texture on stainless steel based on ultrasonic impact peening (UIP) is proposed and investigated. First, the principle of applying the UIP into the fabrication of surface texture is analytically described. Then, the design of the UIP device, particularly the design of functional systems and mechanical structures, is carried out. Next, a UIP experimental device is built, and is further applied to fabricate microgroove textures on 316L stainless steel. The subsequent experimental characterization of microgroove morphology demonstrates the feasibility of the designed UIP device for the fabrication of stainless steel surface texture.
1 February 2021 in IOP Conference Series: Materials Science and Engineering
The residual compressive stress can improve the fatigue performance and strengthen the material surface. In this paper, TC4 titanium alloy is chosen as the material to measure surface residual stress under different static pressures by automatic gradient stress detection and analysis system. ABAQUS software is used to simulate the variation of residual stress in ultrasonic rolling process. The results reveal that the experimental values and the simulation values are consistent basically. The residual compressive stress reaches its maximum when the static pressure is 1000N. When the static pressure is 1100N ∼ 1200N, the depth of the residual compressive stress layer reaches its maximum.