Thin Metal Plate Research Articles

External Loading Effects on Guided Wave Magnetostrictive Sensor Using a Surface-Bonded Nickel Patch

This paper presents the external loading effects on an ultrasonic guided wave (GW) magnetostrictive sensor using a nickel disk patch permanently attached to a thin metallic waveguide plate. The circular magnetostrictive patch transducer (CMPT) consists of the surface-bonded nickel patch and a detachable magnetic circuit device enclosing a ring-shaped sensing coil and cylindrical biasing magnets. Various compressive and tensile stresses were applied to the nickel patch on account of the buckling response of the plate structure. Strain gauges attached to the nickel patch, a Hall effect sensing device, and a laser displacement sensor were utilized to verify the in-plane deformation and the corresponding magnetic flux density change of the nickel patch and the plate's central deflection, respectively, under various external loading conditions of the plate. Several PZT wafers also mounted to the plate were individually used to generate a 30 kHz toneburst GW, which is less sensitive to local stiffness changes of the plate due to the buckling mode. The external loading effects on the CMPT were determined by evaluating the peak-to-peak amplitude variation of the direct arrival waveform of the GW signals acquired by the PZT and CMPT sensor networks. The experimental results demonstrate that the external load applied to the waveguide structure induces compressive and tensile stresses in the nickel patch, leading to distorted GW sensing performance and the directional pattern of the CMPT. Although the presented CMPT has an omnidirectional sensing profile due to its design configuration, the planar-stressed CMPT exhibits a specific directional sensing performance as a result of the stress-induced anisotropic magnetostriction of the nickel disk patch.

The study of acoustic emission waves generated from different types of sources

Abstract This paper presents the results in the analysis of acoustic emission signals that registered during the propagation of acoustic waves in the thin metal plate. The sources are excited by the fracture of mechanical pencil lead (Hsu-Nielsen) with different hardness to model various kinds of cracks at each specific location. To research and identify different types of fracture in the sample, the analysis was performed based on the method of the wavelet decomposition in this research. These results can be used to establish relation between the characteristics of acoustic signals and the parameter of the fracture of structure in the material.

Using open-source microcontrollers to enable digital twin communication for smart manufacturing

One of the key enabling technologies for the smart factory is the Digital Twin, which can be described as a digital model of a physical entity. In smart manufacturing, a digital twin, also referred to as a cyber-physical production system, comprises three integrated components: the product, the process and the machine. In this paper, the design, fabrication and development of a proof of principal manufacturing digital twin demonstrator is discussed. The manufacturing process is a V-bending operation of a thin metallic plate. All three components of a manufacturing digital twin are represented: the metallic plate product, the bending process and the bending machine. Low-cost, IoT-enabled, open-source microcontrollers are used to communicate between the physical and the digital twins. The microcontroller is used to control machine operations, while also extracting sensor data from the system. It is demonstrated that the digital twin enables real-time stress prediction in the product during the bending process, while also tracking and recording machine performance. An information dashboard has also been developed which presents key performance indicators to the end user.

Infrared Thermography of Steel Structure by FFT

Steel bottles, most commonly used by scuba divers, are prone to rust and need to be maintained properly and preventively examined during usage. Due to the geometrical characteristics of the tank (rounded wall) and the inaccessible inner surface of the wall where corrosion damages and initial cracks are expected to be found, the conventional nondestructive techniques do not yield usable results. Herein, emphasis is placed on non-destructive testing (NDT) by means of infrared thermography. The Pulse Phase Thermography (PPT) has been used for composite polymer matrix materials, but with the development of IR cameras, the method has found its application even for NDT of thin metal plates. In this paper, the Fast Fourier Transform (FFT) of infrared images is applied on severely corroded scuba divers tank. The amplitude and phase images contain information on damages or/and other structures inside the inspected part as these lead to a shift in the amplitude and phase of heat waves. In damaged areas heat wave passes shorter path due to differences in the thickness of the metal wall resulting in different heating/cooling curves. As a result, heat waves have different phase delay and defects can be seen as different color zones on phase images in characteristic pit corrosion oval shape.

Characterization of Brake Shims Using Analytical Constrained Layer Damping Theories

AbstractShims in automotive brake systems are applied to suppress brake squeal resulting from self‐excited vibrations. These composite structures consist of thin metal plates and elastomer layers having high damping potential. The characterization and subsequent selection of shims is mainly based on a wide range of experimental investigations so far. To reduce measuring efforts significantly a systematic modeling of shims is focused. Therefore, approaches from literature describing surface damping treatments analytically are considered. The damping effect is mainly based on the shearing of the viscoelastic core which is taken into account by the applied theory. The dissipation potential is characterized by the complex shear modulus of the elastomer layer. Hence, sandwich beam theories enable the prediction of natural frequencies and in particular loss factors of bending mode shapes. In this contribution shims bonded on rectangular steel plates are examined. The main focus is on the determination of rheological influencing variables as well as the impact of boundary conditions in detail. Moreover, the impact of the shim length on the damping behavior is investigated experimentally.

Electrochemical direct-writing machining of micro-channel array

Bipolar plate is an important component in proton exchange membrane fuel cell. The machining of micro-channel array is a key process for the fabrication of metallic bipolar plate. This paper proposed a novel approach named electrochemical direct-writing machining for generating micro-channel array on thin metallic plate at one time, showing a high machining efficiency. In this method, an insulated mask with a row of micro through-holes was integrated to a metallic nozzle, the electrolyte ejected from the nozzle reached to the workpiece through micro through-holes, and then the micro-channel array could be generated from dots to lines by controlling the movement of workpiece. In the machining process, the non-processing zones were covered by the insulated mask, which avoided the stray corrosion. By analyzing the results of simulation and experiment, it was found that due to the accumulation of electrolytic product in the ending point, the profile of this point was different from that of the starting point. The parameters with the voltage of 20 V and pulse duty cycle of 20% were useful for preparing micro channel with good profile and low dimensional difference. And compared with other pulse frequencies, the pulse frequency of 2 kHz could obtain a deeper micro channel. With other parameters unaltered, the dimension of micro channel was decreased with the increasing moving speed of workpiece. At last, with the optimized parameters (voltage = 20 V, pulse duty cycle = 20%, pulse frequency = 2 kHz, and moving speed = 20 μm·s−1), ten micro channels with the length of 60 mm were generated at one time on a metallic plate with the thickness of 0.5 mm. The width was 302 ± 3.53 μm (Mean ± SD) and the depth was 95.9 ± 1.34 μm, showing a satisfied dimensional consistency.

Formability and flow channel design for thin metallic bipolar plates in PEM fuel cells: Modeling

Formability and flow channel design for thin metallic bipolar plates in PEM fuel cells: Modeling

Quasi-static behaviour of crash components with steel skins and polymer foam cores

Different types of crash components are extensively used by the automotive industry to absorb energy during car accidents. Such components typically consist of sandwich structures with thin metal or composite plates as skins and a cellular foam as core to dissipate the energy. In this study, the quasi-static behaviour of two types of polymeric foams with different densities, namely extruded polystyrene (XPS) and expanded polypropylene (EPP), utilized as core material in a crash component, has been investigated. First, an extensive material test program involving compression tests on cubic specimens loaded in different material directions was carried out to reveal the mechanical properties of the foams. Second, quasi-static impact tests were conducted on various target configurations consisting of 0.8 mm thick skins of Docol 600DL steel and the various foam materials as core. In these tests, the applied force and the displacement of the striker were registered by the test machine, while digital cameras and 3D-DIC were used to measure the back-plate out-of-plane displacement of the various components. It seems clear from the presented results that if low weight combined with maximum energy absorption are the primary interests, an XPS foam as core seems to be beneficial, while if force reduction and minimum back-plate displacement are most important, an EPP foam as core seems to be a better choice. Thus, the response of the crash component is largely determined by the properties of the core material during quasi-static loading.

Inverse analysis for the identification of temporal and spatial characteristics of a short super-Gaussian laser pulse interacting with a solid plate

In this paper, the results of numerical experiments verifying a novel setup for laser beam profiling are presented. The experimental setup is based on infrared thermography and includes laser beam illuminating a thin metal plate. The method allows to determine four parameters of the short high-power laser pulse, namely the Super-Gaussian profile coefficient, laser power, pulse start time and duration. The unknown parameters are retrieved based on temporal and spatial temperature distributions at the rear side of the illuminated plate. The applied inverse method is based on Levenberg-Marquardt technique and is implemented in the GNU Octave environment. Solutions of the forward problem are obtained numerically, with the aid of three-dimensional transient heat transfer model implemented in the commercial software ANSYS Fluent. The paper presents the results of the sensitivity analysis as well as calibration and verification of the developed inverse algorithm through application of numerically-generated simulated (artificial) experimental data instead of the physical one. Strengths and weaknesses of the applied approach are widely discussed.

Evaluation of heat transfer in quenching processes with impinging liquid jets

Liquid jets and sprays often are used in metal-working processes like hot rolling, heat treatment or casting for intensive cooling of hot metal specimen and surfaces. Due to the potential evaporation of the quenching liquid during boiling, the local fluid flow as well as the heat transfer are extremely dynamic processes. Therefore, a numerical simulation model has been developed for flow and heat transfer to analyze the entire cooling process in the jet quenching process including all boiling regimes.In this contribution the focus is on quenching of hot metal surfaces with impinging water jets. The impingement liquid jet flow behavior and the wetting front behavior of the jet on the surface of a plate have been analyzed. As result of the simulations, the local surface temperatures and the temperature gradients at the cooled surface are evaluated as well as the local heat transfer rates.The model validation is done by means of different experimental approaches. Therefore, the progression of the wetting front at the quenched surface and the temperature distribution on the back side of thin metal plates during jet quenching has been evaluated.

Connecting physics to ICT: demonstrating a ‘Data Drawbridge’ by means of guided ultrasound waves

Digital data communication, i.e. the transmission of discrete encoded information, is already pervasive, but possesses an ever-growing importance for everyday life in contemporary societies. The underlying physics can vary vastly, e.g. between fibre-optic communication and wireless mobile cellular networks. However, at least three unifying elements can clearly be identified: modulation, transmission and demodulation. Here, we present a setup for demonstrating live as well as teaching the basic elements of data communications. Our setup comprises two identical piezoelectric transducers for actuating and sensing ultrasonic waves on spatially separated plates. The two thin metallic plates, which are bridged by a movable solid piece, constitute the physical transmission medium. Especially the choice of guided ultrasound waves, which are mechanical waves and equivalent to ordinary sound, should facilitate comprehension by students. In order to further reduce abstraction, the usage of a manifest movable link, which allows for disruption of the data flow, is accompanied by introducing the metaphor of a ‘drawbridge’. The presented didactic demonstration should be suitable for stimulating the exploration of more advanced topics in the lecture hall, such as source and channel coding, multiple-carrier and multiple-access methods.

The Study of Thin Film Capacitor on Loss and Current Distribution

The corestructure of inverter DC-link bus film capacitor is too complex, it is more urgent to build the simulation model oncapacitor core loss. Thus, in this paper, the current distribution and the loss distribution of thin film capacitor metal plate were analyzed, and then the mathematical expressions with current distribution and loss distribution were derived on the capacitorplate. On this basis, the concept of equivalent resistivity is put forward, and thelossmodel of equivalent capacitor core was established. By this method, the simulation model with capacitor core was simplified and verified by simulation. At the same time, the structure model of thin film capacitor core was established, and the influence of different core terminals and core shape were analyzed in thefilm capacitor.

Extraordinary optical reflection resonances and bound states in the continuum from a periodic array of thin metal plates.

The creation of artificial structures with very narrow spectral features in the terahertz range has been a long-standing goal, as they can enable many important applications. Unlike in the visible and infrared, where compact dielectric resonators can readily achieve a quality factor (Q) of 106, terahertz resonators with a Q of 103 are considered heroic. Here, we describe a new approach to this challenging problem, inspired by the phenomenon of extraordinary optical transmission (EOT) in 1D structures. In the well-studied EOT problem, a complex spectrum of resonances can be observed in transmission through a mostly solid metal structure. However, these EOT resonances can hardly exhibit extremely high Q, even in a perfect structure with lossless components. In contrast, we show that the inverse structure, a periodic array of very thin metal plates separated by air gaps, can exhibit non-trivial bound states in the continuum (BICs) reflection resonances, with arbitrarily high Q, and with peak reflectivity approaching 100% even for a vanishingly small metal filling fraction. Our analytical predictions are supported by numerical simulations, and also agree well with our experimental measurements. This configuration offers a new approach to achieving ultra-narrow optical resonances in the terahertz range, as well as a new experimentally accessible configuration for studying BICs.

적외선 열화상 이미지 컨트라스트 파라미터를 이용한 결함 크기의 비파괴 평가

Purpose: In this study, the defect quantification of thin metal plate was evaluated by using lock-in infrared thermography.BR Methods: A STS304 standard specimens, which had the artificial-defects of different size, were used. The focal distance between the infrared camera and the specimen was set to 500mm, and the distance between the lump and the specimen was set to 200mm. One halogen lamp with a maximum capacity of 1kW was used, and phase-lock infrared thermal images with a frequency of 1Hz were captured and analyzed.BR Result: Objectively quantified data values were obtained by analyzing the contrast ratio and signal-to-noise ratio.BR Conclusion: The possibility of defect diagnosis for thin metal plate was confirmed by using the lock-in infrared thermography technique.

Preparation and characterization of Sm2Fe17 alloy in LiF-CaF2-SmF3 molten salt

A suitable temperature range of Sm2Fe17 alloy formed only was chosen to investigate the electroreduction of Sm3+ on molybdenum and iron electrode in LiF-CaF2-SmF3 molten salt, which were studied by CV and SWV at different temperatures and concentrations of Sm3+. The reduction of Sm3+ to Sm0 on the iron electrode included two steps. Firstly, a soluble-soluble reaction appears at −0.33 V vs. Cr/Cr2O3 corresponds to the electroreduction of Sm3+ to Sm2+. The electroreduction of Sm3+ to Sm2+ is a reversible process, which is controlled by the diffusion of Sm3+ in the LiF-CaF2-SmF3 molten salt. Secondly, Sm2+ can be reduced at −0.78 V vs. Cr/Cr2O3 on the iron electrode in LiF-CaF2-SmF3 molten salt due to a lower activity of metallic samarium in the Sm2Fe17 alloy than that of samarium metal, and that makes samarium in Sm-Fe alloy more stable while that of Sm2+ could be not reduced by a molybdenum electrode. By experiment of potentiostatic electrolysis it was confirmed that the cathode product from LiF-CaF2-SmF3 melts at −1 V vs. Cr/Cr2O3 for 4 h is a thin layer metallic plate only composing Sm2Fe17 alloy.

Kirigami-based Elastic Metamaterials with Anisotropic Mass Density for Subwavelength Flexural Wave Control

A novel design of an elastic metamaterial with anisotropic mass density is proposed to manipulate flexural waves at a subwavelength scale. The three-dimensional metamaterial is inspired by kirigami, which can be easily manufactured by cutting and folding a thin metallic plate. By attaching the resonant kirigami structures periodically on the top of a host plate, a metamaterial plate can be constructed without any perforation that degrades the strength of the pristine plate. An analytical model is developed to understand the working mechanism of the proposed elastic metamaterial and the dispersion curves are calculated by using an extended plane wave expansion method. As a result, we verify an anisotropic effective mass density stemming from the coupling between the local resonance of the kirigami cells and the global flexural wave propagations in the host plate. Finally, numerical simulations on the directional flexural wave propagation in a two-dimensional array of kirigami metamaterial as well as super-resolution imaging through an elastic hyperlens are conducted to demonstrate the subwavelength-scale flexural wave control abilities. The proposed kirigami-based metamaterial has the advantages of no-perforation design and subwavelength flexural wave manipulation capability, which can be highly useful for engineering applications including non-destructive evaluations and structural health monitoring.

PRINCIPLES OF DEVELOPMENT OF THE TERAHERTZ BAND TELECOMMUNICATION SYSTEM BASED ON THE TECHNOLOGY OF HARMONIC SIGNAL AS THE INFORMATION CARRIER

Physical principles of introduction and reproduction of the information transmitted using the harmonic signal as the information carrier, are analyzed. Based on the performed theoretical calculations confirmed by the results of modeling, there are formed the principles and rules of determining optimal parameters of the ultra-wideband terahertz frequency range communication system on the basis of the technology of electronics using the harmonic signal as the information carrier. The necessity of using the terahertz frequency band while deploying future super high throughput rate telecommunication systems is reasoned. Analysis of the state-of-the-art problem is performed, the direction of research is selected and the mission is set with regards to creation of the terahertz band broadband access telecommunication system with the Gigabit throughput rate within the operating frequencies range of 130…134 GHz. Characteristics of the signal propagation path and defining of the signal losses under the conditions of the terahertz frequency band radio relay system operation are analyzed. On the basis of the analysis performed it is shown that operation of radio relay links in the terahertz band allows practically disregarding the refraction and interference of the electromagnetic waves reflected from the obstacles in the radio signal propagation domain that occurs primarily under the conditions of a dense urban building. The domains of the terahertz band frequencies, which are most of all suitable for use in the radio relay communication lines, are determined. Physical modeling of the super high data rate former is performed on the basis of the multifrequency multiplexing of the OFDM-modulated digital flows, testing at the experimental stand and the optimization aimed at attaining of the maximal throughput capacity of the channel used for transmission of the digital information of the flow are fulfilled in the Ethernet format using the developed software means. The created software and hardware means allowed attaining, for the first time, the general channel data rate of up to 1.2 Gbps at the full duplex. There are developed the block circuit diagram of the system transceiver path – the frequency converters with subharmonic pumping, the heterodyne using a high-stability setting quartz oscillator with the subsequent circuitry of multiplying and amplifying cascades, the bandpass filter using a thin metal plate in the E-plane of the 1.6×0.8 mm waveguide channel, and the horn-lens antenna.

The signatures of acoustic emission waveforms from fatigue crack advancing in thin metallic plates

The acoustic emission (AE) waveforms from a fatigue crack advancing in a thin metallic plate possess diverse and complex spectral signatures. In this article, we analyze these waveform signatures in coordination with the load level during cyclic fatigue. The advancing fatigue crack may generate numerous AE hits while it grows under fatigue loading. We found that these AE hits can be sorted into various groups based on their AE waveform signatures. Each waveform group has a particular time-domain signal pattern and a specific frequency spectrum. This indicates that each group represents a certain AE event related to the fatigue crack growth behavior. In situ AE-fatigue experiments were conducted to monitor the fatigue crack growth with simultaneous measurement of AE signals, fatigue loading, and optical crack growth measurement. An in situ microscope was installed in the load-frame of the mechanical testing system (MTS) to optically monitor the fatigue crack growth and relate the AE signals with the crack growth measurement. We found the AE signal groups at higher load levels (75%–85% of maximum load) were different from the AE signal groups that happened at lower load levels (below 60% of load level). These AE waveform groups are highly related to the fatigue crack-related AE events. These AE signals mostly contain the higher frequency peaks (100 kHz, 230 kHz, 450 kHz, 550 kHz). Some AE signal groups happened as a clustered form that relates a sequence of small AE events within the fatigue crack. They happened at relatively lower load level (50%–60% of the maximum load). These AE signal groups may be related to crack friction and micro-fracture during the friction process. These AE signals mostly contain the lower frequency peaks (60 kHz, 100 kHz, 200 kHz). The AE waveform based analysis may give us comprehensive information of the metal fatigue.

Finite difference time domain modelling of a point-excited elastic plate radiating into an acoustic cavity.

Finite difference time domain (FDTD) models are developed to solve the vibroacoustic problem of a thin elastic plate undergoing point force excitation and radiating into an acoustic cavity. Vibroacoustic modelling using FDTD can be computationally expensive because structure-borne sound wavespeeds are relatively high and a fine spatial resolution is often required. In this paper a scaling approach is proposed and validated to overcome this problem through modifications to the geometry and physical properties. This allows much larger time steps to be used in the model which significantly reduces the computation time. Additional reductions in computation time are achieved by introducing an alternative approach to model the boundaries between the air and the solid media. Experimental validation is carried out using a thin metal plate inside a small reverberant room. The agreement between FDTD and measurements confirms the validity of both approaches as well as the FDTD implementation of a thin plate as a three-dimensional solid that can support multiple wave types. Below the lowest room mode, there are large spatial variations in the sound field within the cavity due to the radiating plate; this indicates the importance of having a validated FDTD model for low-frequency vibroacoustic problems.

A novel weld seam detection method for space weld seam of narrow butt joint in laser welding

Structured light measurement is widely used for weld seam detection owing to its high measurement precision and robust. However, there is nearly no geometrical deformation of the stripe projected onto weld face, whose seam width is less than 0.1 mm and without misalignment. So, it’s very difficult to ensure an exact retrieval of the seam feature. This issue is raised as laser welding for butt joint of thin metal plate is widely applied. Moreover, measurement for the seam width, seam center and the normal vector of the weld face at the same time during welding process is of great importance to the welding quality but rarely reported. Consequently, a seam measurement method based on vision sensor for space weld seam of narrow butt joint is proposed in this article. Three laser stripes with different wave length are project on the weldment, in which two red laser stripes are designed and used to measure the three dimensional profile of the weld face by the principle of optical triangulation, and the third green laser stripe is used as light source to measure the edge and the centerline of the seam by the principle of passive vision sensor. The corresponding image process algorithm is proposed to extract the centerline of the red laser stripes as well as the seam feature. All these three laser stripes are captured and processed in a single image so that the three dimensional position of the space weld seam can be obtained simultaneously. Finally, the result of experiment reveals that the proposed method can meet the precision demand of space narrow butt joint.