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Current constraints on aeronautical parts have led to the introduction of materials like titanium alloys as well as new part geometries featuring large dimensions and reduced thickness. Inappropriate cutting forces during turning operations could lead to high deflections and damage to the machine. In order to ensure the respect of final part geometry and the optimal use of resources, cutting forces have to be known, to anticipate the deformed shape during and after machining operations on thin parts. Current models are offering a solution which can be optimised by the modelling influence of the ploughing effect on cutting forces. Therefore, a mechanistic model is developed in order to improve the prediction of cutting forces during turning operations on titanium alloy Ti6Al4V: this model includes the effect of the clearance face contact radius and comprises two main steps. First, the effect of the clearance contact radius and the effect of the cutting edge lead angle are determined independently, via a direct identification method based on elementary cutting tests. Secondly, this analysis is extended to cutting trials in boring, cylindrical turning and face turning. Then, based on a mechanistic approach, a model is defined according to the previous results and the coefficients are identified thanks to cutting trials in real conditions. The results of the proposed model are then compared to a commonly used model which takes into account mostly the uncut chip thickness effect. It is demonstrated that the proposed cutting force model provides a more accurate prediction of cutting forces.

Soft actuation allows robots to interact safely with humans, other machines, and their surroundings. Full exploitation of the potential of soft actuators has, however, been hindered by the lack of simple manufacturing routes to generate multimaterial parts with intricate shapes and architectures. Here, we report a 3D printing platform for the seamless digital fabrication of pneumatic silicone actuators exhibiting programmable bioinspired architectures and motions. The actuators comprise an elastomeric body whose surface is decorated with reinforcing stripes at a well-defined lead angle. Similar to the fibrous architectures found in muscular hydrostats, the lead angle can be altered to achieve elongation, contraction, or twisting motions. Using a quantitative model based on lamination theory, we establish design principles for the digital fabrication of silicone-based soft actuators whose functional response is programmed within the material's properties and architecture. Exploring such programmability enables 3D printing of a broad range of soft morphing structures. 3D-printed soft actuators have limited motion and are far from reaching the level of complexity found in biological systems. Here the authors present a multimaterial 3D printing platform for the fabrication of soft actuators displaying a wide range of motions that are programmable.

Modern manufacturers of tools for turning threads make them with a non-zero value of the side rake angle of the cutting edge, which significantly increases their efficiency. The value of this angle is approximately equal to the thread lead angle. However, today there is a lack of theoretical research that would provide an algorithm for calculating the effect of the side rake angle of the cutting edge on one of the indicators of the thread accuracy - the accuracy of the pitch diameter. Its effect is particularly noticeable for thread with a large pitch and relatively small diameter - such as drill string tool-joint thread. Theoretical studies show the possibility of ensuring the required accuracy without changing the profile of the cutting edge of the lathe tool.

Based on the Hertz contact theory and considering changes in lead angle and contact angle, the axial stiffness model of a double-nut screw ball pair is established. A ball screw pair is taken as a calculation example, the accuracy of the theoretical model is verified. And the influence of the lead angle and the initial contact angle on the axial stiffness is analyzed. The research results show that the influence of the lead angle on the stiffness can be ignored and appropriately increasing the initial contact angle can effectively improve the stiffness performance.

The present study examines the effect of varying laser incidence angles on textural, microstructural, and geometric characteristics of directed energy deposition (DED) processed materials, providing a more comprehensive outlook on participating laser-matter interaction phenomena and ultimately devising strategies to ameliorate print performance. In this study, single-layer, single-/multi-track specimens were processed to examine the effect of non-orthogonal angular configurations on bead morphology, microstructure, phase composition, and textural representation of DED-processed 316L stainless steel materials. It was observed that bead size decreased at increasing lead and lean angles. Asymmetry in the distribution of the bead morphology as a function of lead angle indicates better catchment for acute lead angle configurations over obtuse configurations. No significant differences in phase composition, texture, and microstructure were observed in moderate off-axis configurations. When the penetration depth for the deposits was below 20 μm, columnar structures dominated the microstructure of the deposited material. At deeper penetration depths, columnar and equiaxed structures were observed at the bead-substrate interface and center of the bead, respectively. Compared to powder-blown DED, wire-DED dilution profiles were found to be asymmetric in both orthogonal and non-orthogonal wire DED samples.

Surface roughness, which has a significant influence on fatigue strength and wear resistance, is an important technical parameter. In practical machining, it is unstable and may be larger than the acceptable surface roughness due to unstable machining process. This will seriously deteriorate the surface performance of the workpieces. Therefore, an effective surface roughness stabilization method is of great significance to improve machining efficiency and reduce machining cost. In this paper, a surface roughness stabilization method is proposed and illustrated by taking five-axis machining as an example. A self-learning surface roughness prediction model based on Pigeon-Inspired Optimization and Support Vector Machine is firstly constructed and its prediction error is only 8.69% in the initial stage. This model has the self-learning ability that the prediction accuracy can be improved with the increase of training data. Furthermore, a machining parameters self-adaption adjustment method based on digital twin is proposed to make the machined surface quality stable. In this method, considering the feasibility of practical machining operation, the cutter posture (i.e. lead angle and tilt angle in five-axis machining) and spindle speed are selected as the adjustable parameters. When the predicted surface roughness doesn’t meet the requirements, the Gradient Descent algorithm is applied to recalculate the new parameters for adjustment. According to the experimental results, the proposed method can stabilize surface roughness and improve the surface quality, which is vital for the precision manufacturing of complex workpiece. Meanwhile, it also greatly improves the intelligence level of manufacturing and production.

Based on current research into the mathematical model of the permanent magnet synchronous motor (PMSM) and the feedback linearization theory, a control strategy established upon feedback linearization is proposed. The Lie differential operation is performed on the output variable to obtain the state feedback of the nonlinear system, and the dynamic characteristics of the original system are transformed into linear dynamic characteristics. A current controller based on the input–output feedback linearization algorithm is designed to realize the input–output linearization control of the PMSM. The current controller decouples the d–q axis current from the flux linkage information of the motor and outputs a control voltage. When the motor speed reaches above the base speed, the field-forward and straight-axis current components are newly distributed to achieve field weakening control, which can realize the smooth transition between the constant torque region and weak magnetic region. Simulation and experimental results show the feasibility and viability of the strategy.

The electromagnetic interaction between Europa and the plasma sheet in the Jovian magnetosphere generates Alfvén waves, ultimately generating auroral footprints in Jupiter's atmosphere. The position of Europa's auroral footprint is a proxy for travel time of the Alfvén waves. We measured Europa's footprint position using the far‐ultraviolet images of Jupiter obtained by the Hubble Space Telescope in two observing campaigns in 2014 and 2022. The measured footprint position indicates a longer Alfvén travel time in the 2022 campaign. We retrieved the plasma sheet parameters at Europa's orbit from the footprint position by tracing the Alfvén waves launched at Europa and found an increase of both mass density and temperature in the plasma sheet in 2022. The Poynting flux generated at Europa is calculated with the retrieved plasma sheet parameters, which suggests the total energy transfer from Europa to its auroral footprint is similar to the case of Io. Plain Language Summary Europa is an obstacle to the plasma corotating with Jupiter's magnetosphere. Through the interaction between Europa and the magnetospheric plasma flow, Alfvén waves are launched at Europa. The Alfvén waves propagate along the field line and ultimately generate auroral emissions at locations distant from the instantaneous magnetic footprint of Europa. The position of Europa's auroral footprint is a proxy for the travel time of the Alfvén waves. We measured the position of Europa's auroral footprint using the far‐ultraviolet images of Jupiter obtained by the Hubble Space Telescope in two observing campaigns in 2014 and 2022. We found large deviations of the footprint position between the two observing campaigns. By tracing the Alfvén waves launched at Europa, we retrieved plasma mass density and temperature at Europa's orbit from the measured footprint position. It is revealed that time variation in the plasma mass density and temperature caused the deviations in the footprint position. We also calculated the Poynting flux generated at Europa using the retrieved plasma parameters and found that the total energy transfer from Europa to its auroral footprint is similar to the case of Io. Key Points We measured the equatorial lead angle of Europa's auroral footprint in Jupiter's atmosphere with the HST data taken in 2014 and 2022 Plasma conditions at Europa's orbit are retrieved from the measured lead angle by tracing the Europa‐originated Alfvén waves Changes in the plasma conditions at Europa's orbit can account for the variation of the footprint lead angle

Among threaded connections of large sizes, tapered thread pipe connections are especially often used, which are a very important part of drill strings. The efficiency of the drill strings largely depends on the accuracy of the tool-joint tapered thread. The production of such joints is implemented on lathes, with the help of tools that have a carbid insert. To ensure high performance, such inserts are recommended to be installed not parallel to the axis of the thread, but at the lead angle of thread. However, the profile of the insert itself is equal to the profile of the thread, and therefore it is important to have a theoretical predictive calculation of the probable influence of the angular setting of the carbide insert on the accuracy of the thread. Based on a detailed consideration of the geometry of the mutual placement of the plate and the tapered thread and the kinematic features of the process, an algorithm for predictive calculation of the accuracy of the thread is created. The result shows that only one of the parameters of the cutting edge really depends on the angle of inclination of the cutting edge - it is its profile. The deviation can reach 7% of the tolerance on the semi-profile angle.

When milling generally shaped surfaces with a ball-end milling tool, machined surface roughness and accuracy as well as machining productivity are often monitored. Improving one of these parameters often causes a decrease in the other monitored parameters. Therefore, knowing possible ways of influencing these parameters is important for achieving the optimum result, if possible, in all requirements. A deep understanding of how some technological parameters influence finished surface roughness is still lacking, as well as detailed knowledge of the relationships among some roughness parameters. In response, an experiment entailing machining of planar samples at different orientation angles was carried out to identify the influence of the studied parameters on the transverse roughness of the final surface. A finding was made that the resulting surface roughness is dependent on the cutting edge geometry of the particular ball-end milling tools used, and the achieving of the required surface roughness can be guaranteed by setting the specific lead angles. Furthermore, it was verified that a minimum lead angle limit can be found based on the geometric properties of the specific milling tool, and the relationship between the evaluated roughness parameters Ra and Rz was found as well.