Thick Metal Plate Research Articles

Temperature distribution and bending behaviour of thick metal plate by high frequency induction heating

Temperature distribution over SS400 carbon steel plate during the induction‐based line heating process was first analysed by a numerical method by electromagnetic‐thermal coupling analysis. To verify the effectiveness of the numerical analysis results, actual line heating‐induced deformation process was carried out by applying newly designed laboratory‐scale high frequency (HF) induction heating (IH) equipment capable of bending thick plate with a moving accuracy of ±0·1 mm in heating coil position. Comparison of analytical and experimental results showed a very good correlation. In this way, the effects of HF IH parameters such as input power and moving speed of heating source on the temperature distribution were subsequently confirmed. HF IH‐induced permanent bending for thick steel plate is also discussed in terms of z‐axis displacements and angular distortion.

Thick Film Transducers for High Frequency Coded Ultrasonography

Recently a new technology of piezoelectric transducers based on PZT thick film has been developed as a response to a call for devices working at higher frequen- cies suitable for production in large numbers at low cost. Eight PZT thick film based focused transducers with resonant frequency close to 40 MHz were fabricated and experimentally investigated. The PZT thick films were deposited on acoustically engineered ceramic substrates by pad printing. Considering high frequency and non- linear propagation it has been decided to evaluate the axial pressure field emitted (and reflected by thick metal plate) by each of concave transducer differing in radius of curvature – 11 mm, 12 mm, 15 mm, 16 mm. All transducers were activated using AVTEC AVG-3A-PS transmitter and Ritec diplexer connected directly to Agilent 54641D oscilloscope. As anticipated, in all cases the focal distance was up to 10% closer to the transducer face than the one related to the curvature radius. Axial pressure distributions were also compared to the calculated ones (with the experimentally determined boundary conditions) using the angular spectrum method including nonlinear propagation in water. The com- puted results are in a very good agreement with the experimental ones. The trans- ducers were excited with Golay coded sequences at 35–40 MHz. Introducing the coded excitation allowed replacing the short-burst transmission at 20 MHz withthe same peak amplitude pressure, but with almost double center frequency, result- ing in considerably better axial resolution. The thick films exhibited at least 30% bandwidth broadening comparing to the standard PZ 27 transducer, resulting in an increase in matching filtering output by a factor of 1.4–1.5 and finally resulting in a SNR gain of the same order.

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Fundamental studies on burrs of a thick metal plate in blanking are carried out to elucidate the burr forming mechanism of a blank cut using a blanking die without putting a blank holder on the plate on the scrap side. In this study, we examined the effects of scrap width, tool shape, wearing at the tool edge and blanking speed on burr shape and height experimentally. The following results are obtained. Even if the cutting edge of a punch does not show any wear, burrs grow up in the case of working under tensile force at connecting areas between the blank side and the scrap side during a blanking process, that is, narrow scrap width and rotating deformation of scrap caused by a punch with triangular groove. Wear at the cutting edge of a punch induces burrs and also burr shape varies with tool shape owing to the difference in the deformation process on the scrap side. In particular, sharp burrs are formed in the case of blanking using a punch with a flat face. In the case of blanking using a wear-free triangular groove punch, the burr height at a high blanking speed is less than that at low blanking speed.

Design, Optimization, and Fabrication of Slotted-Interdigitated Thin Metallic Bipolar Plates for PEM Fuel Cells

Thin metallic sheet bipolar plates (BPPs) with sustainable coating are promising candidates to replace conventional graphitic or machined thick metal plates due to their lightweight and low cost. Interdigitated flow field design is easier for two stamped thin metallic sheets joined together to compose reactant flow fields in both sides and serpentine coolant flow field in the middle. Unfortunately, this kind of BPP inevitable brings two main defects: rupture of material during forming process and uneven flow distribution in practical operation. First, we propose a slotted-interdigitated configuration of the flow field for proton exchange membrane fuel cell with consideration of the characteristics of the metallic sheet forming process. In order to relieve the uneven flow distribution, an analytic model is introduced to analyze the reactant gas flow based on the similarity between the gas flow and the electrical current. Furthermore, an optimization model is proposed. The depth of the slot on the channel rib is optimized to eliminate the uneven flow distribution to obtain high reaction performance. Second, we studied the BPPs from the manufacturability perspective because it is also another important factor that should be considered in the design stage. The key geometric dimensions of flow field section, where the rupture occurs, are extracted and parametrized. Finite element analysis model is established to analyze the formability of BPP by flexible forming process (FFP). In addition, different dies with various flow channel sections are prepared and experiments are performed. Some design principles about material selection and key geometric dimension definition are proposed to improve the formability of BPPs. In the end, based on the design principles and experimental results, the dies are carefully design and fabricated experimental setup for FFP is prepared and practical experiments are performed. High quality metallic BPPs are achieved eventually by FFP.

Burr formation in milling cross-connected microchannels with a thin slotting cutter

This paper studies the burr formation mechanism in milling cross-connected microchannels, and investigates the influences of radial depth of cut ae, cutting speed v, feed speed vf and mesh size on the burr formation. A thin slotting cutter is carried out to fabricate cross-connected microchannels in a metal plate of thickness H. Two kinds of large burrs are produced in the meshes formed by two sets of perpendicular and cross-connected microchannels: flake-like burr and curl-like burr. Results indicate that when ae is equal to or slightly larger than H/2, flake-like burrs are formed. When ae is much larger than H/2, curl-like burrs are produced. Furthermore, curl-like burrs formed at low v are relatively longer than those formed at high v. High vf is unfavorable for the occurrence of long curl-like burrs. In addition, larger mesh is in favor of longer burrs due to its larger capacity.

Electromagnetic scattering by a subwavelength circular hole in a perfect metal plate of finite thickness: matched asymptotic expansion

We present an approach to the problem of electromagnetic scattering by a subwavelength circular hole in a perfect metal plate of finite thickness. The matched asymptotic expansion is employed to solve the scattered fields in the inner and outer regions with respect to the hole position. By use of the dual potentials and Fabrikant’s theory, the solutions are expressed as a combination of spherical functions. In particular, the scattering behavior is illustrated with the near-field quasistatic potentials as well as the far-field radiation patterns. The dipole strengths associated with the subwavelength hole are scaled by the angle of incidence in terms of the vertical electric field and/or horizontal magnetic field components. The effect of the plate thickness is manifest on the attenuation of the dipole strengths associated with the subwavelength hole. For a large thickness, the dipole strengths approach the values for an infinitely deep hole, while for a very small thickness, the results coincide with the Bethe theory.

Fabrication of Metallic Bipolar Plates for Proton Exchange Membrane Fuel Cell by Flexible Forming Process-Numerical Simulations and Experiments

PEM fuel cell nowadays is expensive for widespread commercialization, though it has obvious advantages, such as high efficiency, high power density, fast startup and high system robustness. As one of the most important and costliest components in the PEM fuel cell stack, bipolar plates (BPPs) account for more than 80% of the weight and 30% of the cost of the whole stack. By replacing the conventional graphitic or machined thick metal plates with the lightweight and low-cost thin metallic sheet BPP with sustainable coating, PEM fuel cell will become an attractive choice for manufacturers. In this study, the fabrication of micro-channel features by flexible forming process (FFP) are studied first, which demonstrates the feasibility of using FFP to manufacture thin metallic BPPs. Then, the obtained knowledge is applied onto the fabrication of real thin metallic BPPs with some process amendment. The first investigation of this study focuses on the forming of micro-channel features with 100 μm thickness stainless steel sheet. A finite element analysis (FEA) model is built and key process parameters (hardness of soft tools used in FFP, friction coefficients between contact surfaces) associated with the formability of BPPs are studied. The FEA is partly validated by the experiments. In the second investigation, finite element analysis method is adopted in the design of the BPP forming process. Based on the numerical simulation results, the die setup is prepared and some process amendments are made to improve the formability of BPPs. As a result, high quality metallic BPPs are obtained in the latter experiments, which demonstrates the feasibility to manufacture the metallic bipolar plate by FFP.

Design of critical listening rooms: A historical perspective.

Critical listening room design has progressed to follow loudspeaker evolution from mono to two-channel to multi-channel, as well as the advances in loudspeaker quality. There are basically two fundamental approaches to two-channel room design. The non-environment room, in which the contribution of the room is minimized, and versions of live-end-dead-end, in which early reflections were minimized creating a spatio-temporal reflection free zone and diffuse reflections from the rear of the room are used to create passive surround sound. This presentation will focus on an immersive design for multi-channel loudspeaker formats, which utilizes broad bandwidth absorption and diffusion. Research with low-frequency plate resonators and a broad bandwidth diffusion chamber has contributed to the proposed design and results will be discussed. The proposed multi-channel critical listening room includes the use of low-frequency control down to 40 Hz provided by 4-in.-thick metal plate resonators on a portion of the front wall and in all corners, broad bandwidth diffusion on all wall and ceiling surfaces, and strategically placed multiple subwoofers. The intent is to minimize monophonic reflections and create lateral enveloping energy by uniformly scattering sound from all of the active sound sources in the room.

Mini piezoelectric power generator with multi-frequency response

This paper reports mini piezoelectric power device with multi-frequency response, which works as a power generator under a mechanical vibration environment. It has a 0.192 mm thick PZT-5A piezoelectric bulk film on a 0.1 mm thick Invar42 metal plate, which has a good performance for thermal treatment process. The maximum output power in the C123 cantilever, which has electrically connected in parallel with C1, C2 and C3 cantilevers, is 162 μW at 113 Hz with input drive of 5g acceleration. The output AC voltage of mini piezoelectric power generator is 19.7 V p−p and load impedance is 150kΩ at 113 Hz with input drive of 5g. The acquired device performance was tested by using B&K vibration exciter 4808. Additionally, we demonstrated LED lighting test, which works as a mini piezoelectric power generator under device was mounted on the vacuum pump, which excited ±5 g acceleration.

Casimir Interaction from Magnetically Coupled Eddy Currents

We study the quantum and thermal fluctuations of eddy (Foucault) currents in thick metallic plates. A Casimir interaction between two plates arises from the coupling via quasistatic magnetic fields. As a function of distance, the relevant eddy current modes cross over from a quantum to a thermal regime. These modes alone reproduce previously discussed thermal anomalies of the electromagnetic Casimir interaction between good conductors. In particular, they provide a physical picture for the Casimir entropy whose nonzero value at zero temperature arises from a correlated, glassy state.

Interference of surface plasmon polaritons controlled by the phase of incident light

Interference patterns of surface plasmon polaritons (SPPs) are observed in the extraordinary optical transmission through subwavelength holes in an optically thick metal plate. It is found that the phase of incident light can be transferred to SPPs. We can control the destructive and constructive interferences of SPPs by modulating the relative phase between two incident beams. Using a slightly displaced Mach–Zehnder interferometer, we also observe a SPP interference pattern composed of bright and dark stripes.

A simple Monte Carlo based optimisation model to determine image contrast in an imaging system

Whilst a radiotherapy imaging system can be modeled accurately using full Monte Carlo simulations a quicker method is required for system optimisation. Here we present a Monte Carlo based optimisation model that takes a radiation spectrum and detector response curve as inputs and predicts contrast for a particular imaging system. The model consists of two parts. The first part looks at the interaction of mono-energetic beams with phantoms of various bone and water compositions. In-particular the scatter and primary components emerging from the phantom are analysed. The second part models the response of a detector to various mono-energetic beams. Weighting of the phantom simulations with a linac spectrum results in the prediction of the scatter and primary components incident on an imaging device. Subsequent application of a detector response curve yields the scatter and primary signals in the imager. This technique has been applied to standard 6 and 4MV linac spectra as well as an experimental low atomic number (Z) target configuration to determine various imaging parameters. In particular it has been used to determine the contrast with various detector, phantom and linac spectra combinations. Use of the model shows significant benefits in using a detector with a reduced metal plate thickness for the low Z beam for thin, 5.8cm phantoms that approximate the head and neck region. Whilst contrast can be doubled using the low Z beam and standard MV imager over the current 6MV system, a further improvement in contrast is predicted when using a detector without a metal plate.

Transmission of microwaves through a stepped subwavelength slit

The transmission of normally incident plane wave microwaves through a single stepped subwavelength slit in a thick metal plate is explored. The presence of the step substantially increases the radiation wavelength which may be resonantly transmitted to well beyond twice the plate thickness. Insight into the resonant behavior is provided through analysis of field solutions produced by a finite element model.

Damping function in the penetration/perforation struck by rigid projectiles

The present paper defines a third dimensionless parameter, i.e., the damping function ξ, besides the impact function I and geometry function N of projectile introduced previously, in the penetration/perforation dynamics of a rigid projectile. It only depends on the interaction of projectile and target materials and is independent of projectile geometry. A general penetration resistance, which contains the terms of viscous effect and dummy mass of projectile induced by the deceleration effect, is adopted in the formulation. Dimensionless formula of depth of penetration (DOP) is conducted with only three parameters I, N and ξ for general convex shapes of various rigid projectiles. Different geometry parameters are also presented for some common shapes of projectiles. With accounting for viscous effect and dummy mass of a projectile, the normal perforations of thick metallic plates struck by sharp-nosed rigid projectiles are further studied and only I, N and ξ as well as the dimensionless target thickness χ dominate in perforation. The influence of damping function ξ on penetration/perforation has been discussed in detail. Theoretical predictions of penetration and perforation in the present manuscript show good agreement with the individual published test data of different projectiles and impact velocities as well as different targets.

On the estimation of residual stresses by the crack compliance method

The crack compliance method is a destructive experimental method used for the estimation of residual stress profiles in thick metal plates. Simplifying assumptions, such as dimensional reduction, are generally used in applications of this method. The question of how the simplifying assumptions affect the estimated residual stresses is addressed in this paper.

Electron beam welding of the dissimilar Zr-based bulk metallic glass and Ti metal

We successfully welded 3 mm thick Zr41Be23Ti14Cu12Ni10 bulk metallic glass plate to Ti metal by electron beam welding with a beam irradiated 0.4 mm on the BMG side of the interface. There was no crystallization or defects in the weld because changes in the chemical composition of the weld metal were prevented. Bending showed that the welded sample had a higher strength than the Ti base metal. The interface had a 10 μm thick interdiffusion layer of Zr and Ti.

Theoretical determination of the ablation rate of metals in multiple-nanosecond laser pulses irradiation regime

A detailed understanding of the physical determinants of the ablation rate in multiple nanosecond laser pulses regime is of key importance for technological applications such as patterning and pulsed-laser deposition. Here, theoretical modeling is employed to investigate the ablation of thick metallic plates by intense, multiple nanosecond laser pulses. A new photo-thermal model is proposed, in which the complex phenomena associated to the ablation process are accounted for as supplementary terms of the classical heat equation. The pulsed laser ablation in the nanosecond regime is considered as a competition between thermal vapourization and melt ejection under the action of the plasma recoil pressure. Computer simulations using the photo-thermal model presented here and the comparison of the theoretical results with experiment indicate two different mechanisms that contribute to the decrease of the ablation efficiency. First, during the ablation process the vapour/plasma plume expanding above the irradiated target attenuates the laser beam that reaches the sample, leading to a marked decrease of the ablation efficiency. Additional attenuation of the laser beam incident on the sample is produced due to the heating of the plasma by the absorption of the laser beam into the plasma plume. The second mechanism by which the ablation efficiency decreases consists of the reduction of the incident laser intensity with the lateral area, and of the melt ejection velocity with the depth of the hole.

Very Low Profile and Dielectric Loaded Feeder Antenna

In this letter, very low profile planar horn antenna feeders are designed and measured. Using previous results of antennas consisting of a narrow slot on a metallic plane and flanked by two grooves, a further step is given here by reducing the thickness of the prototype. A key factor in the approach is the operation in the transversal slot resonance instead of the usual longitudinal slot resonance. Moreover, by inserting a dielectric material of relative permittivity epsiv <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> > 1, the thickness can be further reduced, maintaining and even improving the radiation features of the prototype. Reducing the metallic plate thickness has important consequences in the weight and profile of the antennas, making them easy to handle and to fit into different structures. In addition, in ranges where the wavelength is of the order of centimeters, a thick metallic plate can be a serious drawback due to mechanical restrictions. In these cases the design following the rules given in this letter can alleviate this constraint.

Slow waves caused by cuts perpendicular to a single subwavelength slit in metal

Resonant transmission of microwaves through a subwavelength slit in a thick metal plate, into which subwavelength cuts have been made, is explored. Two orientations of the cuts, parallel and perpendicular to the long axis of the slit, are examined. The results show that the slits act as though filled with a medium with anisotropic effective relative permeability which at low mode numbers has the two values ∼(1, 9.1), increasing to ∼(1, 14.4) for higher mode numbers.

On the performance of dichroic mirrors with hexagonal holes

AbstractThis article presents an innovative design of a 45°‐incidence S/X/Ka‐band inductive dichroic mirror, intended for the upgrade of a ground station antenna of the European Space Agency supporting deep‐space missions. The dichroic mirror consists of a thick metal plate perforated periodically with hexagonal holes. The use of hexagonal shapes allows for tightly packing the holes and provides a large number of degrees of freedom. This permits to improve the electrical performance of the dichroic mirror and to increase its mechanical stiffness. To highlight the advantages of this shape, first we report the simulated and measured performance of a dichroic mirror with rectangular holes, with the aim of validating the analysis tool and of providing a comparison for the new design. Afterward, we discuss the design of the new dichroic mirror based on hexagonal holes, and systematically compare the performance obtained in the two cases, namely with rectangular and hexagonal holes. It is shown that the use of the new dichroic mirror with hexagonal holes permits to preserve the radiation pattern of the feed horn and does not significantly increase the cross‐polar level. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1858–1862, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21767