Lead Angle Research Articles

Study on cell wall deformation in ultrasonic cutting aluminum honeycomb by straight-blade knife

Aluminum honeycomb sandwich structure has been widely used in the aeronautic and astronautic fields. As the core part, aluminum honeycomb needs to be machined but defects are easily generated. Ultrasonic cutting is an advanced machining technology for honeycomb materials due to improved machining quality. However, ultrasonic cutting aluminum honeycomb by straight-blade knife is usually accompanied by cell wall deformation, which results in poor machining quality. To facilitate the industrial use of ultrasonic cutting aluminum honeycomb with a straight-blade knife, a finite element (FE) model was developed, and experimental studies had been performed. The effects of the blade-inclined angle and lead angle of the straight-blade knife were studied by analyzing the cutting force, the stress and deformation in the cutting zone. Results showed that the cell wall deformation was significantly suppressed when cutting with a corresponding blade-inclined angle and a lead angle. Meanwhile, effects of ultrasonic cutting parameters on the cell wall deformation were also studied, indicating that a well-machined cell wall could be obtained when cutting with large ultrasonic amplitude.

Changes in the Plasma Sheet Conditions at Europa's Orbit Retrieved From Lead Angle of the Satellite Auroral Footprints

AbstractThe 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.

A novel approach of stability and topography prediction in five-axis ball-end milling process through workpiece-edge-coupling

By studying the workpiece-edge-coupling (WEC) in five-axis ball-end milling, the contact characteristics between the workpiece and edge curve are analyzed, and the chip model is extracted and simplified. The edge curve involved in the cutting process of each edge are calculated at each time and a new instantaneous numerical chip thickness model is established. Then the milling forces and stability lobe diagram (SLD) are calculated in following cut process with lead and tilt angle. The milling forces and SLD of lead angle at 15° and tilt angle at −15° are verified by comparing with Otzurk model as references, and it is found the SLD of WEC model can reflect the unstable points more properly than that of Otzurk model. Also the vibration in [Formula: see text] and [Formula: see text] directions show a divergence trend, which proves the high precision for the new algorithm adapted to the stability prediction of five-axis ball-end milling process. In addition, the surface topography is acquired considering lead and tilt angle as well as forced vibration, and the result is consistent with the experiment in the existing literature. It is found that the milling forces, SLD and surface topography show the same variation trend with the increase of lead and tilt angle. Besides, the stability region significantly expands and the surface topography improves by applying positive tilt angle other than the negative. Then, under the conditions of positive lead and tilt angle, increasing lead angle and decreasing tilt angle reduces the milling force, expands the stability region of SLD and improve the surface topography. The optimized tool posture is acquired by the coincident analysis of milling force, SLD and surface topography under different lead and tilt angle.

The residual stress state in meso- and micro-milling processes with a ball-end mill in Ti–6Al–4V titanium alloy

An experimental investigation and comparative analysis of the residual stress state between micro- and meso-milling processes with a ball-end mill on the Ti–6Al–4V titanium alloy were carried out. A methodology to study the characteristic kinematics of a five‑axis machining process in a three-axis vertical machining centre was proposed. The study considers the chip formation process according to the lead and tilt angles of the tool axis concerning the normal vector of the surface. When using the up‑milling cutting strategy, the defect of smeared/adhered material to the surface occurs in both the micro- and meso-milling levels, associated with the build-up edge and build-up layer phenomenon. The residual stress tensor of the surface was obtained through the X-ray diffraction technique. The down-milling cutting strategy produced the best surface finish and higher compressive residual stresses. The experiments showed higher compressive residual stresses in the feed direction than in the cross-feed direction. The micro-milling process produced higher compressive residual stresses than those observed in the meso-milling process.

Polynomial shaping based three-dimensional impact angle and field-of-view constrained guidance

This paper proposes a polynomial-based three-dimensional (3D) impact angle-constrained guidance law considering the seeker's field-of-view (FOV) bound. The guidance laws are derived using nonlinear coupled dynamics of the interceptor-target engagement against stationary as well as constant velocity targets. Line-of-sight (LOS) orientations between the interceptor and the target in both pitch and yaw planes are shaped as two cubic polynomial functions of relative range. An explicit expression for the look angle of the interceptor is acquired in terms of the LOS polynomials. This expression facilitates the embodiment of the FOV constraint in the boundary conditions inflicted on the polynomials. A system of equations with the eight unknown coefficients is obtained by employing the appropriate launch and terminal conditions of the interceptor-target engagement. Reference LOS angle and lead angle profiles are generated using the calculated coefficients, complying to which the interceptor achieves a zero miss distance with desired impact angle and FOV constraints. A tracking controller is then designed using a nonlinear control technique that enables the interceptor to follow reference lead angle profiles in mutually orthogonal planes. Unlike the already existing guidance strategies for 3D impact angle and FOV-constrained target interception, the proposed nonlinear guidance strategy is designed without the use of linearization or decoupling. Moreover, no switching logic or multi-phase guidance structures are employed in the proposed guidance strategy, which eliminates possible jumps in the guidance command. The effectiveness of the proposed guidance law is validated using numerical simulations, along with a comparison study with the existing strategy.

Impact time guidance law for arbitrary lead angle using sliding mode control

PurposeThis paper aims to investigate a novel impact time control guidance (ITCG) law based on the sliding mode control (SMC) for a nonmaneuvering target using the predicted interception point (PIP).Design/methodology/approachTo intercept the target with the minimal miss distance and desired impact time, an estimation of time-to-go is introduced. This estimation results in a precise impact time for multimissiles salvo attack the target at the same time. Even for a large lead angle, the desired impact time is achieved by using the sliding mode and Lyapunov stability theory. The singularity issue of the proposed impact time guidance laws is also analyzed to achieve an arbitrary lead angle with the desired impact time.FindingsNumerical scenarios with desired impact time are presented to illustrate the performance of the proposed ITCG law. Comparison with the state-of-art impact time guidance laws proves that the guidance law in this paper can enable the missile to intercept the target with minimal miss distance and final impact time error. This method enables multiple missiles to attack the target simultaneously with different distances and arbitrary lead angles.Originality/valueAn ITCG law based on sliding mode and Lyapunov stability theory is proposed, and the switching surface is designed based on a novel estimation time-to-go for the missile to intercept the target with minimal miss distance. To intercept the target with initial arbitrary lead angles and desired impact time, the authors analysis the singular issue in SMC to ensure that the missile can intercept the target with arbitrary lead angle. The proposed approach for a nonmaneuvering target using the PIP has simple forms, and therefore, they have the superiority of being implemented easily.

Influence of the width of cut in ultrasonic vibration superimposed face milling of X46Cr13 and X40CrMoV5-1 on the surface microstructure and CVD diamond coating adhesion

Ultrasonic vibration superimposed milling (UVSM) with an oscillating movement of the specimen in the direction of the tool axis is an efficient method for the generation of microstructured functional surfaces. The application of end milling cutters with a diameter smaller than the length and the width of the surface to be structured generally results in recuts and path overlaps. In order to avoid surface recutting, a small lead angle was realized by slightly tilting the ultrasonic system with the specimen. The overlapping area of two adjacent paths was kinematically simulated for different widths of cut (from 70% to 90% of the tool diameter). Cutting experiments were carried out by UVSM of X46Cr13 and X40CrMoV5-1 steel specimens to investigate the influence of the width of cut on the surface generated in the overlapping area and also the adherence of a subsequently deposited CVD diamond layer. For this purpose, 3-D laser scanning microscopy and SEM analysis were applied. The knowledge gained allows for designing UVSM processes, especially regarding 3-D freeform surfaces with defined microstructures subjected to CVD diamond coating.

Analytical Prescribed Performance Guidance with Field-of-View and Impact-Angle Constraints

Aiming at the impact-angle-control guidance with field-of-view constraint in the three-dimensional space, a novel analytical prescribed performance guidance law is proposed. First, a new prescribed performance function is designed in the relative range domain, and the common drawbacks of most existing prescribed performance functions, such as large overshoot, time dependency, and infinite-time convergence, are avoided. Second, the three-dimensional biased pure proportional navigation guidance frame is selected. The biased term is derived based on the prescribed performance control theory and the optimal error dynamic method, for realizing the terminal impact-angle constraint. After that, the analytical solution of missile lead angle is derived under some linearization approximations, and two methods are respectively developed for obtaining the range of the guidance gain and updating its value to guarantee the satisfaction of the field-of-view constraint during the guidance process. Moreover, for the proposed guidance law and methods, the tracking error could be ensured to remain in the predefined performance boundaries. Finally, numerical simulations are conducted to verify the effectiveness of the new theoretical findings.

Dominating influence of cutting-edge lead angles on arc-trajectory machining of Nomex® honeycomb composites by using a straight blade cutter

Nomex® honeycomb composites (NHCs) with circular arc features are a challenging issue in the machining of aviation curved structural components. Compared to linear feature machining, arc feature machining involves six-axis coordinated motion, introducing additional variables. Directly referencing the linear feature machining process will lead to the deterioration of contour accuracy and surface quality in arc-trajectory machining (ATM). To further explore the influence of process variables on ATM, this study developed an error model for straight blade tool (SBT) ATM and investigated the influence of cutting-edge lead angles (γ) on contour accuracy and surface quality. A vertical cutting process was proposed, and experiments proved it provided the optimal machining quality (the defect rate of core cells was only 3.93 %) compared to forward and backward inclination cutting (7.23 %∼34.3 % and 9.71 %∼17.36 %, respectively). Additionally, it was revealed that the main reason for the deterioration of surface quality on ATM was the excessive angle between the cutting edge direction and the feed direction. Based on the results above, the influence and optimization of cutting-edge lead angles were revealed, and the advantage of vertical cutting process for machining NHCs with arc-trajectory was demonstrated. This research provides a feasible method for the machining of NHCs with arc-trajectory using SBT.

Study on chip shape and cutting force model of milling process in any direction of space

This paper considers the calculation process for chip shape and cutting force of milling process in any direction of space.In the milling process with the existence of lead and tilt angle, the edges and boundary curves go through the process of one intersection, two intersections, tangency and non intersection in a milling cycle, thus the chip thickness needs to be calculated in various regions. The milling force is calculated by using the differential method. Then by comparing the milling forces when the lead angle is 5° and the tilt angle is 10° with when there is no inclination angle, the influence of inclination angle on machining process is studied. Meanwhile, by comparing the milling forces calculated by geometric analysis method with those calculated by classical Altintas model, the validity of the proposed method is verified. In addition, by comparing the milling forces obtained using the classical Altintas model with those obtained in published literature, the rationality of the method is further demonstrated.

Y-ring’s mechanical behavior during sealing cap’s assembly process based on the pressure core sampling for seafloor drill

In order to expand the application of seafloor drill in the field of natural gas hydrate exploration, a pressure core sampling technical scheme suitable for seafloor drill operating conditions is proposed. The assembly action principle of sealing cap in the scheme is introduced. The factors affecting the sealing reliability during the assembly of the sealing cap are analyzed. A geometric model of the sealing structure is established. The variation regular of the max von Mises stress is discussed during the assembly process. The relationship between the assembly parameters and the maximum von Mises stress is clarified. The parameters optimization scheme is proposed and verified by experiments. The results show that: the Y-ring’s maximum von Mises stress variation trend has five stages and the maximum von Mises stress produces peak stress in the rising stage, excessive interference and friction factor make the peak appear in the fluctuation stage in advance, the lead angle within 10°–30° has little effect on the maximum von Mises stress peak value, the axial displacement speed affect the growth rate and amplitude of the maximum von Mises stress curve, the drilling tool’s pressure loss ratio is within 8% under the 10–40 MPa after 6 h.

Distributions of tension and torsion in a threaded connection

Threaded connection is a common structure in engineering applications, and its load distribution plays a critical role on the static and dynamic performances of the system. Although Sopwith (1948) studied the tension distribution along a thread helix, a model that includes the tension and torsion distributions in threaded connections is still missing. In this paper, we establish a comprehensive model which takes tension–torsion coupling into consideration for thread connection for the first time. In the proposed model, the bolt and nut are considered as two linearly elastic bodies with a tension–torsion coupling deformation, and deformation of the thread is calculated by the modified theory of the trapezoidal cantilever beam model. Based on the compatibility condition of these deformations, tension–torsion coupling equilibrium equations for the threaded connection can be built up. Our theoretical analysis shows that the proposed model agrees with the Sopwith’s theory when the lead angle of the threaded connections is sufficiently small. However, the torque neglected by the Sopwith’s theory must be taken into account in the cases of threaded connections with large lead angles. In addition, we perform a three-dimensional finite element analysis to demonstrate the validity of the proposed model. Finally, influence of geometrical and material parameters on load distribution is investigated. The finding of this work may provide a new insight into the fastening and anti-loosening design for threaded connections.

Optimization of the Fluted Force-Feed Seeder Meter with the Helical Roller Using the Discrete Element Method and Response Surface Analysis

The seed metering process of a fluted force-feed seeder was simulated using the Discrete Element Method and its parameters optimized using the Box–Behnken Design of Experiments and the Response Surface Method. The rotational speed of the feed roller, the lead (helix) angle of the flutes, and the number of flutes were the independent variables, while the response value was the seeding uniformity index. Two regression models were investigated, and the following conclusions drawn. For the flute lead angle between 0 and 10 degrees, and the number of flutes between 10 and 14, it was found that the number of flutes and the lead angle influenced the seeding performance the most, with the order of importance being the (i) number of flutes, (ii) lead angle and (iii) roller speed. For the flute lead angle between 5 and 15 degrees, and the number of flutes between 12 and 16, it was found that the roller speed and the number of flutes influenced the seeding performance the most, with the order of importance being the (i) roller speed, (ii) number of flutes and (iii) flute lead angle. The two regression models were then minimized for the seeding uniformity index and the corresponding optima verified experimentally on a conveyor belt test stand fitted with an image recognition system.

Three-Dimensional Spatial–Temporal Cooperative Guidance Without Active Speed Control

This paper investigates the three-dimensional (3D) spatial–temporal cooperative guidance problem for multiple missiles with time-varying speeds, which is addressed by a progressive design strategy. First, the zero miss distance and desired impact directions are realized by a 3D vector impact angle control guidance (IACG) law whose time-to-go is predicted accurately and efficiently by a numerical algorithm. Then, by introducing an implicit trajectory-to-go function, the time-to-go control mechanism is clearly revealed under missile speed variation. Accordingly, a coordinated biased term is added to the 3D vector IACG law to ensure a simultaneous attack. Finally, considering the seeker’s field-of-view (FOV) limit, the resultant cooperative guidance law is further augmented by another biased term to prevent the lead angle from exceeding its upper bound. Unlike similar existing results, the proposed one can satisfy multiple complex spatial–temporal constraints without active speed control, thereby manifesting great practical significance. Several numerical simulations are provided to show the effectiveness and advantages of the proposed cooperative guidance law.

Development of an autonomous docking system for autonomous surface vehicles based on symbol recognition

Docking is an important and difficult task in ship navigation that has traditionally required excessive time and expert piloting. In this study, an autonomous docking system based on symbol recognition was developed for autonomous surface vehicles (ASVs). The docking process is divided into an approaching phase for approaching the docking port and a docking phase for guiding an ASV into the target docking port. In the docking phase, the desired heading of the ASV is determined considering the centering and lead angles. The centering angle is used for pure tracking, and the lead angle is used for guiding the ASV into the safety zone. Each angle is determined according to the ASV's relative heading angle and position, which are estimated by detecting the dock and symbols using a camera and LiDAR. Docking tests based on Turtlebot and ASV were conducted to verify the performance of the proposed docking algorithm. The performance of the developed autonomous docking system was verified by participating in the docking mission at the Korea Autonomous BOAT competition 2021.

The Io, Europa, and Ganymede Auroral Footprints at Jupiter in the Ultraviolet: Positions and Equatorial Lead Angles

AbstractJupiter's satellite auroral footprints are a consequence of the interaction between the Jovian magnetic field with co‐rotating iogenic plasma and the Galilean moons. The disturbances created near the moons propagate as Alfvén waves along the magnetic field lines. The position of the moons is therefore “Alfvénically” connected to their respective auroral footprint. The angular separation from the instantaneous magnetic footprint can be estimated by the so‐called lead angle. That lead angle varies periodically as a function of orbital longitude, since the time for the Alfvén waves to reach the Jovian ionosphere varies accordingly. Using spectral images of the Main Alfvén Wing auroral spots collected by Juno‐UVS during the first 43 orbits, this work provides the first empirical model of the Io, Europa, and Ganymede equatorial lead angles for the northern and southern hemispheres. Alfvén travel times between the three innermost Galilean moons to Jupiter's northern and southern hemispheres are estimated from the lead angle measurements. We also demonstrate the accuracy of the mapping from the Juno magnetic field reference model (JRM33) at the completion of the prime mission for M‐shells extending to at least 15 RJ. Finally, we shows how the added knowledge of the lead angle can improve the interpretation of the moon‐induced decametric emissions.

ASSESSMENT OF THE STABILITY OF MOTION OF A WHEEL SEMI-TRACK UNIT

The paper analyzes the influence of the geometric parameters of the semi-trailer unit on the stability of its movement. A mathematical model of the dynamics of the cultivator unit under the influence of disturbing forces is developed. The analysis of research results shows that in the process of movement, the wheeled semi-trailer unit is subjected to transverse forces, which arise as a result of the unevenness of the traction resistance of the side and rear beams. The main vector and the main moment cause the unit to deviate from the rectilinear movement. The differential equations obtained in the work make it possible to determine the values of the lead angles, their components, and the speed at which the lead of the unit will be the smallest. Based on the dependence of the angle of departure of the unit on the disturbing forces and speed of movement, the optimal location of the side bars of the semi-trailer unit on the tractor frame was found.

Three-dimensional impact-angle-constrained cooperative guidance strategy against maneuvering target

In order to improve the multiple-missile cooperative attack capability and penetration capability, this paper investigates two three-dimensional impact-angle-constrained cooperative guidance strategies against maneuvering target for controllable thrust missiles. First, a three-dimensional nonlinear guidance model is established that does not assume small missile lead angles in the guidance process. Second, in the line-of-sight (LOS) direction of the cluster cooperative guidance strategy, the proposed guidance algorithm transforms the simultaneous attack problem into a second-order multiagent consensus problem, which effectively solves the practical problem of low guidance precision provoked by the time-to-go estimation. Then, by combining second-order sliding mode control (SMC) and nonsingular terminal SMC theory, the guidance algorithms in the normal and lateral directions to the LOS are designed, respectively, so that the multi-missile can accurately attack a maneuvering target while satisfying the impact angle constraints. Finally, by utilizing the second-order multiagent consensus tracking control in the leader-following cooperative guidance strategy, a novel leader-following time consistency algorithm is investigated to ensure that the leader and followers can attack the maneuvering target simultaneously. Moreover, the stability of the investigated guidance algorithms is proved mathematically. The effectiveness and superiority of the proposed cooperative guidance strategies are verified by numerical simulations.

Accuracy of Thread Profile Depends on the Lathe Tool Angle of Inclination. Theoretical Investigation

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.

Electromagnetic design and temperature field analysis of hybrid excitation primary permanent magnet linear motor

Hybrid excitation primary permanent magnet linear motor has the dual advantages of high thrust density of primary permanent magnet linear motor and the flexibility on adjusting the air gap magnetic field of hybrid excitation motor. In this paper, two new 36/4 hybrid excitation primary permanent magnet linear motors with different secondary structures are proposed. Based on the detailed introduction of the motor topology and operation mechanism, the structural parameters are optimized, and the pole arc coefficient of the primary pole shoe and the secondary are finally determined to be 0.4. The secondary is magnetoresistive, and the final thrust adjustment range is about 16.8% under the conditions of optimal armature current and current lead angle. The temperature field of the motor in the magnetizing state is analyzed. The results show that the temperature of the motor decreases gradually from the center to both sides after 7200 s of operation of the new hybrid excitation structure, while the permanent magnet will not be demagnetized permanently. It shows an acceptable reliability.