Perpendicular Rolling Research Articles

Effect of material anisotropy on the first-order vibration of piezoelectric oscillators in circular plate configurations

Valveless piezoelectric pumps are widely used in microfluidic actuation because of their simple structure, ease of integration, absence of electromagnetic interference, minimal valve wear, and absence of frequency–response lag issues. These pumps primarily rely on chamber volume changes, causing most piezoelectric oscillators to operate in the first-order vibration mode. However, recent studies on valveless piezoelectric pumps have observed that many pumps exhibit two flow peaks at similar operating frequencies; the underlying mechanism behind this anomaly remains underexplored. In this study, we investigated the impact of substrate metal on the first-order vibrations of piezoelectric oscillators. By conducting tensile tests on rolled pure copper sheets, we measured Poisson's ratio and the elastic modulus in both the parallel and perpendicular rolling directions. Subsequently, we derived the natural frequencies on the plane. Experimental verification of the theoretical predictions was achieved through amplitude experiments conducted on piezoelectric oscillators in air. The dual-peak flow phenomenon was demonstrated to be solely related to the substrate metal of the piezoelectric oscillator. This is attributed to the presence of two first-order vibration natural frequencies on the plane of the substrate metal, resulting in the generation of two amplitude peaks and consequently the appearance of two flow peaks.

Developing an Automated System to Control the Rolled Product Section for a Wire Rod Mill with Multi-Roll Passes

The key priority of metallurgical industry development is expanding the range and improving the quality of bar products and their major component, steel wire. Continuous wire rod mills with multi-roll passes have been developed and implemented over the past decades. These include mills with four-roll passes with mutually perpendicular rolls. The specific feature of mills with complex passes is the impossibility of conduct and the direct measurement of the workpiece dimensions in several directions during rolling. The paper studies the development of a system for indirect control over complex section geometry by adjusting the interstand space tension with simultaneous compensation for changes in rolling forces. The paper contribution is the first justification of a technique for the control over the indirect rolled product section on mills with multi-roll passes based on theoretical and experimental research. Analytical and experimental dependencies between the metal pressure on the rolls and the semifinished rolled product temperature, rolling speed, and single drawing have been obtained for various steel grades. The impact of process factors on the rolled product section geometry when rolling in stands with four-roll passes has first been studied. The automated control system implementing the proposed technique has passed pilot tests on a continuous five-stand mill. The processes occurring in closed-loop speed and torque control systems under controlling and disturbing effects have been experimentally studied. Implementing the proposed algorithms indirectly confirmed the reduced impact of tension and pressure on the section geometry.

Thermal Parametric Study of Butt Joints Using Friction Stir Welding

The purpose of this study is to look at the mechanical and microstructural properties of dissimilar 2024 and 7075 aluminum sheets that have been welded together using friction stir welding (FSW). The two sheets, which were aligned with perpendicular rolling directions, were successfully fused; the welded sheets were then tested under strain at room temperature to determine the mechanical response to the materials for the parents Since the fatigue behavior of light metals is known, the fatigue endurance (S–N) curves of welded joints have been achieved. A resonant electro-mechanical testing machine load is the best performance indicator for a significant part of industrial applications; welded sheets is the best performance indicator for a big part of industrial applications. At a load frequency of around 75 Hz, a constant load ratio R = 0.1 was employed. The microstructure that formed as a result of the FSW Optical and scanning electron microscopy have been used to investigate the process, both on ‘as welded’ specimens and on tested specimens following a rupture

Parametric optimization on tensile strength of friction stir butt joints of dissimilar AA6061 and AA5052 aluminium alloys by Taguchi technique

Friction stir welding(FSW) is asolid-state weldingmethod for amalgamation aluminum alloys and has been used in aerospace, rail, automotive and marine applications. In FSW, the parent metal properties such as tensile strength, ductility, and hardness are controlled the plastic flow of the metal under the action of rotating non-consumable tool. The process parameters such as welding speed, Feed, tilt angle, etc. play an important role in deciding the quality of weld in FSW. This work aims to investigate the tensile strength of dissimilar AA6061 and AA5052 aluminum sheets joined by FSW. The two aluminum sheets are arranged in a line with perpendicular rolling directions of the tool. The Taguchi L9 experimental method is chosen to construct the numbers of welding experiments. Analysis of variance (ANOVA) analysis is performed to get the optimum range of process parameters and their effects upon the tensile strength of the weld joints. The sheets are successfully welded and the welded sheets are tested under tension at room temperature to examine the strength. The result shows that the welding speed is 900 rpm, feed is 40 mm/min and tilt angle 2.5 are the influential process parameters to join these dissimilar joints.

Zero-Prandtl-number convection with slow rotation

We present the results of our investigations of the primary instability and the flow patterns near onset in zero-Prandtl-number Rayleigh-Bénard convection with uniform rotation about a vertical axis. The investigations are carried out using direct numerical simulations of the hydrodynamic equations with stress-free horizontal boundaries in rectangular boxes of size (2π/kx) × (2π/ky) × 1 for different values of the ratio η = kx/ky. The primary instability is found to depend on η and Ta. Wavy rolls are observed at the primary instability for smaller values of η (\documentclass[12pt]{minimal}\begin{document}$1/\sqrt{3} \le \eta \le 2$\end{document}1/3≤η≤2 except at η = 1) and for smaller values of Ta. We observed Küppers-Lortz (KL) type patterns at the primary instability for \documentclass[12pt]{minimal}\begin{document}$\eta = 1/\sqrt{3}$\end{document}η=1/3 and Ta ≥ 40. The fluid patterns are found to exhibit the phenomenon of bursting, as observed in experiments [K. M. S. Bajaj, G. Ahlers, and W. Pesch, “Rayleigh-Bénard convection with rotation at small Prandtl numbers,” Phys. Rev. E 65, 056309 (2002)]. Periodic wavy rolls are observed at onset for smaller values of Ta, while KL-type patterns are observed for Ta ≥ 100 for \documentclass[12pt]{minimal}\begin{document}$\eta =\sqrt{3}$\end{document}η=3. In case of η = 2, wavy rolls are observed for smaller values of Ta and KL-type patterns are observed for 25 ≤ Ta ≤ 575. Quasi-periodically varying patterns are observed in the oscillatory regime (Ta > 575). The behavior is quite different at η = 1. A time dependent competition between two sets of mutually perpendicular rolls is observed at onset for all values of Ta in this case. Fluid patterns are found to burst periodically as well as chaotically in time. It involved a homoclinic bifurcation. We have also made a couple of low-dimensional models to investigate bifurcations for η = 1, which is used to investigate the sequence of bifurcations.

Oscillatory instability and fluid patterns in low-Prandtl-number Rayleigh-Bénard convection with uniform rotation

We present the results of direct numerical simulations of flow patterns in a low-Prandtl-number (Pr = 0.1) fluid above the onset of oscillatory convection in a Rayleigh-Bénard system rotating uniformly about a vertical axis. Simulations were carried out in a periodic box with thermally conducting and stress-free top and bottom surfaces. We considered a rectangular box (Lx × Ly × 1) and a wide range of Taylor numbers (750 ⩽ Ta ⩽ 5000) for the purpose. The horizontal aspect ratio η = Ly/Lx of the box was varied from 0.5 to 10. The primary instability appeared in the form of two-dimensional standing waves for shorter boxes (0.5 ⩽ η < 1 and 1 < η < 2). The flow patterns observed in boxes with η = 1 and η = 2 were different from those with η < 1 and 1 < η < 2. We observed a competition between two sets of mutually perpendicular rolls at the primary instability in a square cell (η = 1) for Ta < 2700, but observed a set of parallel rolls in the form of standing waves for Ta ⩾ 2700. The three-dimensional convection was temporally quasiperiodic for 750 ⩽ Ta ⩽ 1114, chaotic for 1115 ⩽ Ta < 1125, and quasiperiodic once again for 1125 ⩽ Ta < 2700. The three-dimensional quasiperiodic flow bifurcated into a two-dimensional periodic flow for Ta ⩾ 2700. The convection at the primary instability were three-dimensional and quasiperiodic in time for all values of Ta (⩽3000) in a box with η = 2. Küppers-Lortz type of convection was observed at the primary instability in longer boxes (4 ⩽ η ⩽ 10). The convective structures consisted of the appearance and disappearance of straight rolls, rhombic patterns, and wavy rolls inclined at an angle \documentclass[12pt]{minimal}\begin{document}$\phi = \frac{\pi }{2} - \arctan {(\eta ^{-1})}$\end{document}ϕ=π2−arctan(η−1) with the straight rolls. We also present a low-dimensional model constructed for a square box (η = 1).

Microstructural Characterization and Mechanical Properties in Friction Stir Welding of Aa7075 Aluminium Alloy

The heat treatable aluminium alloy AA7075 is used extensively in the aircraft industry because of its high strength to weight ratio and good ductility. In this present study the effect of process parameters on the mechanical and micro-structural properties of AA 7075 joints produced by friction stir welding was analyzed. The two sheets, aligned with perpendicular rolling directions, have been welded successively. The welded sheets have been tested under tension at room temperature in order to analyze the mechanical response with respect to the parent materials. Effects of welding speed and fixed location of base metals on microstructures, hardness distributions, and tensile properties of the welded joints were investigated. Optical microscope and SEM analysis revealed that the stir zone contains a mixed structure and onion ring pattern with a periodic change of grain size as well as a heterogeneous distribution of alloying elements. The maximum tensile strength was achieved for the joint produced at rotation speed of 800rpm and a welding speed of 20 mm/s.

Quantitative microstructural characterisation of Fe–30Ni alloy after martensitic transformations by means of stereological and magnetic methods

In the Fe–30Ni alloy investigated a martensitic transformation can occur both during quenching or plastic deformation. Martensite formed during plastic deformation, depending on the thermo-mechanical treatment applied, exhibits a different morphology from that achieved during quenching and forms the so-called composite-like structure. The morphology and volume fraction of martensite depends both on strain and temperature. In the present studies Fe–30Ni alloy was deformed by monotonic rolling in one path and perpendicular rolling in the temperature range M D– M S. The aim of the investigations was a determination of martensite volume fraction depending on the strain and temperature. To examine the influence of strain, the alloy was deformed by rolling in one path or perpendicular rolling at a temperature of − 30 °C, in the strain range of 10–30%. The dependence of temperature was investigated by rolling with 30% strain in a temperature range from − 30 °C to − 80 °C. The variants of thermo-mechanical treatment performed enabled us to achieve different martensite morphologies and volume fractions. Microstructural analysis was performed by means of light microscopy and transmission electron microscopy. The results of quantitative microstructural analysis of martensite and retained austenite volume fractions formed in different thermo-mechanical treatments were compared with those obtained by magnetic measurements. The fraction of deformation-induced martensite determined varied from 2% to 86%. The partial volume fractions V V MF of martensite formed in different deformation directions were also determined. It was found that the influence of the temperature on the martensite volume fraction is more pronounced than the influence of strain.

Mechanical and microstructural behaviour of 2024–7075 aluminium alloy sheets joined by friction stir welding

The aim of the present work is to investigate on the mechanical and microstructural properties of dissimilar 2024 and 7075 aluminium sheets joined by friction stir welding (FSW). The two sheets, aligned with perpendicular rolling directions, have been successfully welded; successively, the welded sheets have been tested under tension at room temperature in order to analyse the mechanical response with respect to the parent materials. The fatigue endurance (S–N) curves of the welded joints have been achieved, since the fatigue behaviour of light welded sheets is the best performance indicator for a large part of industrial applications; a resonant electro-mechanical testing machine load and a constant load ratio R=σ min/ σ max =0.1 have been used at a load frequency of about 75 Hz. The resulted microstructure due to the FSW process has been studied by employing optical and scanning electron microscopy either on ‘as welded’ specimens and on tested specimen after rupture occurred.

Mechanical response of 2024-7075 aluminium alloys joined by Friction Stir Welding

The mechanical and microstructural properties of 2024 and 7075 aluminium alloys joined together by friction stir welding were analysed in the present study. The two materials were welded with perpendicular rolling direction and after were tested in tension at room temperature in order to analyse the mechanical response and to observe the differences with the parent materials, the tensile response of the material in longitudinal direction revealed an increase in strength respect to the transverse one. The cyclic fatigue tests were conducted in the axial direction with R = σmin/σmax = 0.1). The microstructure resulting from the FSW process was studied by employing optical and scanning electron microscopy.

Grain-boundary motion in layered phases.

We study the motion of a grain boundary that separates two sets of mutually perpendicular rolls in Rayleigh-Bénard convection above onset. The problem is treated either analytically from the corresponding amplitude equations, or numerically by solving the Swift-Hohenberg equation. We find that if the rolls are curved by a slow transversal modulation, a net translation of the boundary follows. We show analytically that although this motion is a nonlinear effect, it occurs in a time scale much shorter than that of the linear relaxation of the curved rolls. The total distance traveled by the boundary scales as epsilon(-1/2), where epsilon is the reduced Rayleigh number. We obtain analytical expressions for the relaxation rate of the modulation and for the time-dependent traveling velocity of the boundary, and especially their dependence on wave number. The results agree well with direct numerical solutions of the Swift-Hohenberg equation. We finally discuss the implications of our results on the coarsening rate of an ensemble of differently oriented domains in which grain-boundary motion through curved rolls is the dominant coarsening mechanism.

Application of two-axial rolling for multicore Bi(2223)/Ag tapes

Multicore Ag-sheathed Bi(2223) tapes have been prepared by OPIT technique using the two-axial rolling deformation by active `Turk's head' roller. In comparison to wire drawing, the presented technique allows one to avoid the tensile stress during composite deformation and to increase the BSCCO-core density. A better homogeneity of filaments has been obtained by two-axial rolling. The transport critical current and its angular dependencies have been measured for single and 36 filament rectangular wires and tapes. Total tape widening influences the transport current density considerably but anisotropy at 0.1 T and 77 K is affected only slightly. Reduced anisotropy has been measured in a single core wire which has texturing of grains in two perpendicular rolling planes.

A grain boundary in cellular structures near the onset of convection

Abstract The structure of a grain boundary between parallel and perpendicular rolls is analysed by means of the amplitude equation. If ∊ is the (small) difference between the control parameter and its threshold value, this grain boundary is divided into an outer region of thickness of the order of ∊−½ and an inner region of thickness ∊−3/10. If the wavenumbers on both sides of the grain boundary are different, it moves with a constant velocity. This velocity ensures the balance by viscous loss of the energy gain due to the replacement of a less optimal structure by a more optimal one.

Boundary conditons on the envelope function of convective rolls close to onset

Boundary conditions are derived for the envelope function of convective rolls approaching a rigid sidewall at an arbitrary orientation. This generalizes previous results for parallel and perpendicular rolls. It provides the first step in a study of the convective pattern to be expected close to onset in Rayleigh–Benard cells of any cross section, and allows consideration of more complicated patterns in rectangular or circular cross sections.