Flow Field Characteristics and Experimental Research on Inner-Jet Electrochemical Face Grinding of SUS420J2 Stainless Steel

Electrochemical grinding (ECG) is processed by the combination of dissolution and grinding. It is very suitable for the processing of difficult-to-cut stainless steel, but its processing performance is restricted by the matching effect of dissolution and grinding. In this work, the processing of the torus surfaces of the stainless steel shaver cap was taken as the research object. A flow field model including the through-hole structure and the rotation of the grinding head was proposed to optimize the flow field distribution and promote the uniform dissolution of materials. The flow field simulation results showed that the rotational flow formed by the high-speed rotation prolonged the electrolyte flow path and was not conducive to the discharge of electrolytic products, and the reasonable selection of the diameter and distribution of the through-hole could reduce the velocity difference. The effects of rotational speed, feed rate, and inlet pressure on the flatness and surface roughness of the torus surfaces were experimentally investigated, and a better matching effect of dissolution and grinding was obtained. Moreover, the experimental results showed that the inner-jet ECG had a good prospect in the batch processing of high-hardness stainless steel parts.

Design of the High-Speed PMSG with Two Different Shaft Material Considering Overhang Effect and Mechanical Characteristics

In general, high-speed machines should be designed to satisfy electromagnetic and mechanical characteristics. In this study, the design of high-speed permanent magnet synchronous generator with two different shaft materials considering overhang effect and mechanical characteristics was performed. It was confirmed that the leakage magnetic flux generated by the two shaft materials electromagnetically affects the high-speed generator. Additionally, it is important to accurately predict the natural frequency mode and critical speed to prevent damage and vibration of the rotating body owing to scattering during high-speed rotation. Therefore, the mechanical characteristics of the designed model were analyzed. In this study, we propose a design method that considers both the electromagnetic effects and mechanical characteristics. Subsequently, verification was performed through experiments and comparisons for the validity and reliability of the proposed design method.

AN ASSESSMENT OF THE DISPLACEMENT OF A CAM FOLLOWER USING REGULA FALSI METHOD

Cam is a mechanical component that transforms circular motion to reciprocating motion by using mating component, called the follower. The principal aim of this work was to study and analyse the displacement of a cam-follower with Regula Falsi method and verify its input by using MATLAB and FORTRAN simulations. A study was conducted on angle of rotation and the displacement of the follower, which is equal to the radius of the cam given as transcendental equation to find the exact solution. The parameters such as initial guess, final guess, iteration counter and the desired displacement are involved in finding the angular displacement to the cam system in high speed rotation. The analysis was done using a computer programming that enables verification of the results obtained and ascertaining whether the inputs are correct or not for the displacement in cam follower system. The computer output showed results of the two data sets that yielded solutions and two that did not. The results revealed that the programme could be used to find the angular displacement corresponding to a given follower displacement for any cam; if the function CAMF is modified to include the appropriate radius function, r(x). The results further revealed that at a halve cycle of a rotating cam, which is equivalent to (x = 3.142 rad), is a solution that would provide the desired displacement of the follower (opening and closing of valves).

Influence of Impeller Sinusoidal Tubercle Trailing Edge On Pressure Pulsation in a Centrifugal Pump At Nominal Flow Rate

The high-speed rotation of impellers leads to strong rotor-stator interaction, which mainly causes the pressure pulsation of centrifugal pumps. An impeller with a bionic sinusoidal tubercle trailing edge (STTE) can reduce the intensity of the rotor-stator interaction and thus reduce the pressure pulsation of the centrifugal pump. In this study three profiles of STTE were designed based on the pectoral fin structure of humpback whales of which the influence on the pressure pulsation of centrifugal pumps was studied via experiment and numerical simulation. Results show that a reasonable design of STTE can effectively eliminate the high-frequency pressure pulsation in the rotor-stator interaction region of the centrifugal pump. The use of STTE2 and STTE3 profiles affects the amplitude reduction of pressure pulsation at the blade passing frequency (fBPF). Compared with the impeller without the STTE profile, the amplitudes of pressure pulsation with STTE2 and STTE3 profiles are decreased by 47.10% and 44.20% at the pump discharge, while the decrease, at the volute throat are 30.36% and 25.97%, respectively. Detailed flow structures inside the pump show that the STTE profile can inhibit the vortex generation at the blade trailing edge, and the local high-intensity pressure pulsation can be reasonably avoided. This study helps improve the pressure pulsation characteristic of centrifugal pumps and their operation stability.

Dynamic Support Stiffness of Motorized Spindle Bearings under High-speed Rotation

The rotor operating stiffness of high-speed motorized spindles (HSMSs) is key to machining accuracy. Because HSMSs are difficult to load due to their high speeds, a contact loading device was developed to test rotor operating stiffness. The dynamic support stiffness of the front/rear bearings (DSSB) is the main factor affecting the rotor operating stiffness. Two novel experimental schemes for measuring the DSSB are proposed: 1) indirect measurement—by analysing deformation displacements at two points on the external loading rod of the HSMS, and 2) direct measurement—by eddy current sensors installed near the front/rear bearings. Based on the experimental device and two experimental schemes, the influences of working-condition parameters on the DSSB were tested. The results show that the proposed experimental device and two experimental schemes can effectively and accurately measure rotor operating stiffness and DSSB at speeds of up to 30,000 rpm. However, because the tapered connection gap between the loading rod and rotor increases the measured deformation displacement, the DSSB measured by the indirect measurement scheme was relatively small. The DSSB decreases with speed and increases with radial force and working temperature. This study provides a new experimental basis for the quality inspection of finished HSMSs and the verification of theoretical bearing stiffness models.

E-Textile Systems Reliability Assessment—A Miniaturized Accelerometer Used to Investigate Damage during Their Washing

E-textiles reveal a new and hybrid sector of the industry that is created by the integration of electronic components or textile-based electronics in our daily life textile products. They are facing problems in terms of washability, reliability, and user acceptance. This manuscript explains the mechanical stresses acting during the washing process and their impact on e-textile systems. Different washing programs were investigated in terms of total process duration. This washing process duration is mainly divided into three diverse washing actions: low-speed rotation, high-speed rotation, and stop time. This investigation was performed to highlight the importance of the washing actions and their percentages in the total washing process. A piece of fabric with a flexible PCB (printed circuit board), equipped with an accelerometer with a Bluetooth communication device and a microcontroller, was placed in the washing machine to analyze the movement of fabric provoked by washing stresses. The PCB was used for fabric movements recording to determine the impact of mechanical stress on e-textile systems during the washing process. From the video analysis, it was concluded that the duration of the low-speed and high-speed rotation actions should be privileged comparing to the duration of the whole washing process. A power spectral density (PSD) analysis based on the accelerometer outputs was realized. Mechanical stresses at different frequencies were identified. Based on this analysis, it could be possible to improve the protocols of mechanical tests (Martindale and pilling box) used to simulate the mechanical stress applied to e-textile systems during the washing process.

Gentlefile Versus Protaper in the Shaping Ability in Simulated J-shaped Root Canals

Background: The aim of this study was to compare the shaping ability of Gentlefile (GF), a unique stainless-steel (SS) rotary system, and ProTaper (PT), a popular mechanical nickel-titanium (NiTi) system, in J-shaped simulated canals. Methods: Thirty-three resin blocks with a J-shaped canal were selected and randomly divided into 3 groups according to tip diameters: GF red (#23); PT F2(#25); GF blue (#26). They were prepared in one training model which imitated human dentition. Specimens were photographed by a dental operating microscope before and after preparation. The images were processed and measured using professional software. Centering ability and canal transportation were calculated, canal aberration and instrument separation were also recorded. Results: The GF system was significantly less transported than PT F2 in the apical and middle section. What’s more, better centering ability of GF was shown in all sections, including the coronal level. However, there was no difference between GF red and GF blue based on above criteria. Two cases of instrument separation of GF were noted.Conclusion: Under the conditions of this study, the two GF files showed better shaping ability, but were more easily separated than PT F2. As a novel SS rotary system, Gentlefile is more flexible to prepare narrow and curved root canals by scraping dentin with high-speed rotation, which might help remove smear layer much thoroughly and cause less dentin microcracks.

High-speed rotating device for X-ray tomography with 10 ms temporal resolution

The temporal resolution of X-ray tomography, using a synchrotron radiation X-ray source, has been improved to millisecond order in recent years. However, the sample must be rotated at a speed of more than a few thousand revolutions per minute, which makes it difficult to control the environment around the sample. In this study, a high-speed rotation device has been developed, comprising two synchronized coaxial motors movable along the direction of the axis, which can stretch or compress the rotating sample. Using this device, tomograms of breaking rubber were successfully obtained at a temporal resolution of 10 ms.