Polytetrafluoroethylene (PTFE) is commonly employed in the fabrication of fluidic components within the circulatory systems of electronics, biomedicine and other industries. The process of groove cutting plays a pivotal role in the production of intricate PTFE elements. However, achieving the desired dimensional accuracy during the grooving of PTFE workpieces is challenging. This study employed PCD arc cutters to perform cutting experiments on PTFE workpieces with a specific focus on analyzing the cutting temperature, cutting force, groove width accuracy, and uniformity of groove width. The findings indicate that the cutting temperature is primarily influenced by the spindle speed during the cutting process, with the highest temperature observed at a spindle speed of 1000r/min. Furthermore, the cutting force is predominantly affected by the feed rate, and the largest force recorded at a feed rate of 0.25mm/r. The feed speed has a great influence on the accuracy and uniformity of the groove width, and an excessive feed speed has an adverse effect on the cutting accuracy. Additionally, the grooves exhibit elastic recovery post-machining, leading to a measured groove width smaller than the desired width. In this experiment, the optimal groove outcome was attained with a feed rate of 0.1mm/r and a spindle speed of 200r/min. Consequently, the process parameters investigated in this study can be effectively used in practical production settings to enhance the cutting accuracy of PTFE components.

Deep learning methods are increasingly being applied in fault diagnosis because of the capability of representing internal correlations through network structures and extracting hidden features from original data. Convolutional neural networks (CNNs) can perceive local features through convolutional kernels and obtain more advanced features through iteration, which significantly improved the accuracy of fault diagnosis. However, the randomness of feature extraction will cause the insufficient use of the input information and also limiting the network training for specific faults. In this paper, a multi-channel CNN based on Squeeze-and-Convolution attention is introduced to enhance the efficiency of fault diagnosis for rotating machinery. A multi-channel CNN is used to enhance the input information which reduces the input loss, then a new channel attention mechanism based on squeeze-and-excitation module is proposed to reduce the computational complexity of network while focusing on key features. To combine the multi-channel CNN and SC module, the proposed ISC structure enables basic CNN to extract more comprehensive and important features. The fault diagnosis results, which based on two bearing databases named MFPT datasets and Paderborn University datasets, have demonstrated that the ISC-CNN proposed in this study outperforms most commonly used methods. The method exhibits strong performance on both conventional datasets and small sample datasets, which validates its effectiveness.

The root fillet profile determines the bending strength of a gear tooth. When manufacturing gears by generating-type cutters, the tool tip center of curvature follows a trochoidal path that determines the root profile of the gear. Rack tool tip at transverse section is a part of an ellipse for helical and beveloid gears. This ellipse can be vertical, horizontal or rotated due to existence of helix and cone angles. The envelope of the family of ellipses whose centers are on the trochoid path forms the secondary trochoid curve that determines generated gear actual root fillet profile. None of the studies in the literature include the parametric equations of the secondary trochoid curve for helical and beveloid gear types. Based on the parametric equations of rotated ellipses, this study proposes an approach to obtain the equations of the family of ellipses and secondary trochoids for helical and beveloid gears. Derivatives of primary trochoid curve, rolling angle of gear blank and rotation angle of tip ellipse are used to obtain the corresponding parameter that gives the secondary trochoid point on the enveloping ellipse. Numerical examples of spur, helical, straight beveloid and helical beveloid gears are given to verify and to validate the proposed approach. Results indicate that the proposed approach is a practical way to calculate the secondary trochoid points on the enveloping ellipses.

Porous metal materials are constructed using selective laser melting (SLM). Porous metals exhibit different physical and mechanical properties, depending on the building conditions. It is crucial to understand how process parameters affect mechanical qualities so that SLM objects can be used in diverse components. In this study, SUS630 specimens were developed under various combinations of laser parameters. The influence of laser power and scanning speed on the tensile strength of porous SUS630 specimens was investigated. Initially, 13 porous specimens were produced under diverse conditions. Tensile tests were performed on these specimens. The results indicated that the laser power and the scanning speed during building affected the tensile strength of the specimens. Furthermore, the tensile strength of the porous specimens in the laminating direction was lower than in the other orientations. Since SUS630 is often used as a mold material after precipitation-hardening treatment, the H900 precipitation-hardening treatment was performed after the as-built alloy under porous conditions. The results showed that the tensile strength of the porous specimens following the treatment was greater than that of the as-built specimens. Compression tests were also conducted to investigate the relationship between compressive strength and building conditions. Furthermore, the hardness of the porous specimens was also investigated. The relationship between the Brinell hardness and the tensile strength of the porous structural materials was clarified. Similarly, the relationship between the compressive strength and the Brinell hardness of the porous specimens was also determined. The results indicated a linear relationship between Brinell hardness and tensile and compressive strength. The H900 precipitation-hardening treatment also improved the mechanical properties of the porous SUS630 specimens.

In view of the common phenomenon of rail corrugation on subway lines, both field measurement and numerical simulation were used to study mechanism of rail corrugation. In field measurement, vibration signals of vehicles were measured when a train passing through straight and curved segments. In numerical simulation, a model of single wheel set operating in curve rail is established. The good agreement between the results of field measurement and numerical simulation verified that the wavy wear is caused by the negative slope section of the wheel-rail viscous vibration characteristic. Under low load, stick-slip vibration occurs on the small radius curve of the wheelset, and the tangential creepage bouncing back and forth between the adhesive and sliding states will lead to uneven wear of the rail, resulting in initial rail corrugation. At the same time, the frequency distribution of vertical vibration acceleration is different when it passing through two relevant measured point, this means the stick-slip vibration can be eliminated by changing the wheel-rail creep characteristics by applying a third substance to the inner rail surface. And the wavelength of rail corrugation caused by the stick-slip vibration is predicted by numerical simulation and agrees well with that measured at the test site.

In a plastic gear pair, the low rigidity of plastics can lead to a higher actual contact ratio due to tooth deflection under load compared to the geometrical one. This phenomenon contributes to a decrease in tooth root stress. The effect of transmitted torque on the actual contact ratio under load is more noticeable in internal gear pairs than in external ones. Therefore, no regard for the contact ratio under load results in evaluating higher tooth root stresses in internal gear pairs. In other words, assessing the bending strength of plastic material through running tests of external gear pairs leads to underestimating the load capacity of internal gear pairs. Consistent tooth-root-stress evaluations in external and internal gear pairs require considering the actual contact ratio under load. The present study proposed a mechanical model applicable to spur gears, which enables considering the effect of the actual contact ratio under load in tooth-root-stress evaluations for plastic gears. This model extends the geometrical contact length by the Hertzian-contact semi-width at the tooth tip and defines the contact ratio under load as the extended contact length divided by the base pitch. Furthermore, the proposed model is also acceptable to helical gears through virtual spur gears with virtual overlap; i.e., an imaginary overlap in the virtual spur gear pair. Introducing a new factor, a contact ratio factor; i.e., the quotient of the geometrical and the actual contact ratios, reduced the evaluated tooth root stresses of plastic internal gear pairs and improved the consistency of the evaluations in external and internal gear pairs.