Plate Material Research Articles

Corrosion Behavior of Ta and TiN Double-Layer-Coated SUS316L for PEMFC Bipolar Plates Using Plasma-Enhanced Atomic Layer Deposition and Magnetron Sputtering

In this study, the corrosion behavior of Ta and TiN double-layered-coated SUS316L is investigated for proton-exchange membrane fuel cells (PEMFCs) bipolar plates. The surface of SUS316L is modified by depositing 4.5 μm of Ta and 200 or 400nm of TiN using magnetron sputtering and plasma-enhanced atomic layer deposition, respectively. The experimental results reveal that this coating significantly enhances the corrosion resistance and reduces the interfacial contact resistance of the bipolar plate. Under electrochemical conditions that are 500 times more acidic than those specified by the Department of Energy (DOE), the coated SUS316L achieves a corrosion current density of only 1.0µA/cm2 at 0.6 VSCE. The corrosion current density reduces up to more than two orders of magnitude, and the interfacial contact resistance with carbon paper is below 10 mΩcm2 at compression forces below 140N/cm2, thus meeting the DOE 2025 target value for both corrosion current density and interfacial contact resistance. Our findings suggest the potential of Ta and TiN double-layered-coated SUS316L as durable bipolar plate materials for PEMFCs.

Modeling of free vibrations and resonant frequencies of simply-supported submerged horizontal plate.

A theoretical approach was applied to study the vibration of simple-supported submerged horizontal plate. The derived analytical solution was used to determine natural frequencies for a horizontal plate vibrating in fluid. The investigations were conducted for a very wide range of material density and elasticity modulus covering all materials used in engineering practice. Analysis shows that plate vibration frequency decreases with increasing plate width and draft, and decreases with decreasing plate thickness. Moreover, the results show that a substantial effect on vibration of submerged plate has mass of water above plate. The results also show that plate vibration frequency decreases with increasing plate material density and decreases with decreasing elasticity modulus. The dominant factors affecting the vibration of the submerged plate are the plate width, the plate thickness, and elasticity modulus. For moderate and low values of elasticity modulus, vibration frequency is becoming lower than frequency of water waves. This is very important because wave frequencies overlap with the natural plate vibration frequencies, which may lead to resonance and failure of a structure. The problem is that the overlap of plate vibration frequencies and wave frequencies occurs for very wide range of wave and plate parameters. Laboratory experiments confirm theoretical results.

Influence of Applied Loads on Free Vibrations of Functionally Graded Material Plate–Shell Panels

An analysis of the influence of applied loads on free vibrations of plate and shell panels made of functionally graded materials is analyzed in the present work. Formulations for the static analysis considering geometrically nonlinear behavior, as well as linear buckling and free vibrations analyses are considered. A calculation of the through-thickness stress distribution is also performed. The finite element model is based on a higher order shear deformation theory using a non-conforming flat triangular plate/shell element with three nodes, and eight degrees of freedom per node is used in the numerical implementation. The results obtained with this numerical model are presented, discussed, and compared with alternative solutions published by other authors in some benchmark applications.

Transmission of Lamb wave in a micro-mechanically piezoelectric fiber-reinforced composite plate

The present work addresses the propagation characteristics of Lamb wave in a piezoelectric fiber-reinforced composite material plate. The considered plate is micro-mechanically modeled using the analytical techniques of the Strength of Materials and Rule of Mixtures. Secular equations are deduced for symmetric and antisymmetric modes of Lamb wave by employing suitable boundary conditions. The data of two distinct PFRC materials are taken into account, viz. PZT-5A-epoxy and CdSe-epoxy with different fiber volume fractions to investigate the latent characteristics of Lamb wave propagation. The amplitudes of dilatation and electrical potential of considered material are examined numerically and manifested graphically for both kinds of modes, i.e., symmetric and antisymmetric modes. The obtained graphical results are also compared for both kinds of modes. A comparative study has been carried out to exhibit the concealed characteristics of Lamb wave propagation for various distinct cases of considered structure for both symmetric and antisymmetric modes. The determined analytical results are in well agreement with the results present in the existing literature.

Continuous Purification of Biodiesel with Deep Eutectic Solvent in a Laboratory Karr Column

Following the trend of transport decarbonization, biodiesel has become a promising alternative fuel option. Its production includes multiple steps, all of which can be time-consuming and energy intensive. Improving any of these steps could bring considerable environmental and economic benefits. The utilization of deep eutectic solvents (DESs) for glycerol extraction from crude biodiesel has predominantly been explored as a batch process. This work provides insight into continuous column extraction. Different waste cooking oils were used to produce biodiesel via transesterification with methanol, and the selective solvent for purification was DES choline chloride–ethylene glycol (1:2.5, mol.). A laboratory Karr column at different pulsation frequencies and DES to biodiesel mass ratio was used for extraction. Plate material (steel and 3D printed PETG) and geometry influence on the efficiency of extraction were investigated. Contact angle measurement was used to measure the surface free energy of steel and PETG and the spreading ability of biodiesel and DESs on both materials. Extraction efficiency was analyzed by several analytical techniques. Higher efficiency was observed with steel plates of a triangular pitch hole arrangement. Increasing the mixing intensity and DES to biodiesel mass ratio further increased the efficiency of extraction.

Modelling of Cryopumps for Space Electric Propulsion Usage

Electric space propulsion is a technology that is used in a continuously increasing number of spacecrafts. The qualification of these propulsion systems has to run in ground-based test facilities which requires long testing times and powerful pumping systems. In these usually large test facilities, high pumping speeds are achieved with cryopumps. Cryopump operation is very expensive with respect to electrical energy and cooling water consumption. Therefore, being able to optimize pump shape, cold plate material, and pump placement in a chamber is beneficial. Pump design and tuned operating strategies can reduce costs and increase intervals between regeneration. Testing different pump configuration setups in a large facility is mostly prohibitive due to high costs and long testing times. Optimization via modelling is a better choice for design and also, later, for operation. Therefore, having a numerical model and proven guidelines at hand for optimization is very helpful. This paper describes a new model developed at DLR for the optimization of cryopump layout and operation. Model results are compared with cryopump operational and warm-up data. This validation is the basis for further optimization actions like multi-layer insulation layouts and pump cold plate upgrades, and helps in understanding and mitigating the detrimental effect of water condensates on the cryopump cold plates.

Investigation of the hydrodynamic and thermodynamic behavior of the liquid jet quenching process

Liquid jet quenching of metals is typically adopted to achieve specific material properties of metals, thereby making them suitable for advanced engineering applications. In this process, a metal plate is heated and cooled rapidly by impinging water jets. The temperature history during cooling leads to a microstructural transformation thereby improving the material properties such as hardness. During liquid jet quenching, since the plate surface temperature is above the Leidenfrost temperature, the boiling heat transfer dominates. This is associated with an intense cooling and water vapor generation, where the Leidenfrost effect impedes the immediate wetting of the surface. The resulting uneven cooling over the plate surface tends to potential deformation and cracking. To control this process, a detailed understanding of the spatial and the temporal heat transfer behavior is imperative. Experiments in this context are limited and therefore investigating the conjugate heat transfer process is to be combined with a multi-phase numerical model. The two-phase numerical model based on the Euler-Euler approach is developed and validated to simulate the jet quenching of a stationary plate considering all the boiling regimes within a single framework. This model consists of two phases, the liquid water which is the continuous phase (primary) and the water vapor modeled as the dispersed phase (secondary). In this study, a circular water jet (tap water) impact is considered and the plate materials under investigation are aluminum alloy (Al-alloy) and stainless steel (St-steel). Experiments are performed using infrared and high-speed imaging. The validated numerical model provides the technical parameters such as wetting front behavior, heat flux, HTC (heat transfer coefficient) etc. The influence of the jet Reynolds number and the plate material properties on the heat transfer is analysed. The study emphasizes that the plate material has a significantly higher influence on the heat transfer during jet quenching.Graphical abstract

Acoustic Source Localization in Composite Plates using sideband peak count – Index Technique

In this study the Non-Linear Ultrasonic Sideband Peak Count-Index (SPC-I) technique is used as the foundation for anovel approach towards acoustic source localization (ASL) in orthotropic composite plates. The SPC-I based technique proposed here does not require the signal attenuation information or any knowledge on the time of arrival of the signal. It should be noted that since individual sensors can have varying sensitivities, the signal attenuation measured from the recorded signal amplitude is not very reliable. In addition, it is not necessary to have any prior knowledge of the mechanical properties of the composite plate material. All these are achievable by attaching 25 sensors that are well-scattered on the surface of the plate. The signals that are generated by an acoustic source are recorded by these 25 sensors. The recorded signals are then analyzed to derive the SPC-I value for each signal. The calculated SPC-I values are run through an optimization algorithm to predict the acoustic source location. Such localization is possible because the composite plate is inherently a non-linear material. Hence, as the signal travels longer distances through a composite plate, the recorded signal should show increasing level of distortion due to material non-linearity and dispersion. This phenomenon manifests itself primarily as a consequence of signal scattering and frequency modulation. Because of this, the phenomena of increasing distortion in the signal with increasing propagation distance can be exploited and utilized to predict the location of the acoustic source by solely utilizing the SPC-I values. This acoustic source localization technique is experimentally verified on a Carbon Fiber Reinforced (CFR) composite plate of dimension 500 mm x 500 mm with a thickness of 1 mm. The experimental results confirmed the feasibility of the proposed technique.

Ion Implantation Combined with Heat Treatment Enables Excellent Conductivity and Corrosion Resistance of Stainless Steel Bipolar Plates for Hydrogen Fuel Cells.

316 L stainless steel is an ideal bipolar plate material for a proton exchange membrane fuel cell (PEMFC). However, the thickening of the passivation film on the stainless steel surface and the dissolution of corrosive ions during operation will affect the durability of the PEMFC. Herein, a heterogeneous layer is prepared on the surface of 316 L stainless steel through dual ion implantation of molybdenum ion and carbon ion combined with heat treatment to promote the corrosion resistance and conductivity of the bipolar plate. The ion implantation technique resulted in a uniform distribution of Mo and C elements on the surface of 316 L stainless steel, with a modified layer depth of about 70-80 nm. The electrical conductivity of the ion implanted samples was significantly improved, and the interfacial contact resistance was reduced from 464.25 mΩ × cm2 to 42.49 mΩ × cm2. Heat treatment enhances the surface homogenization, repairs the defects of irradiation damage, and improves the corrosion resistance of stainless steel. The corrosion current density of (Mo+C)-600 samples decreased from 1.21 × 10-8 A/cm2 to 2.95 × 10-9 A/cm2 under the long-term corrosion condition of 4 h. These results can provide guidance for the modification of stainless steel bipolar plates.

Thermal constriction resistance of a functionally graded material plate heated by a circular disc heat source on one face and isothermal on the opposite face

This article presents a study of the thermal constriction phenomenon for the Functionally Graded Materials (FGM). The studied configuration is that of a plate subjected to a circular disc heat source. The study is carried out under steady-state conditions, considering axisymmetric heat conduction. An analytical solution is developed to calculate the temperature and thermal constriction resistance. Thermal conductivity, which varies as a function of position in the depth direction of the plate, is modeled by a law that allows to consider several possible evolutions (slow, rapid or linear). The thermal constriction resistance resulting from these thermal conductivity evolutions is studied and analyzed as a function of the geometric and physics parameters of the problem. As a verification, we compared the proposed solution with the same configuration but in the asymptotic case of homogeneous conductivity. Both solutions lead to the same result. In a second step, a homogeneous apparent thermal conductivity, which would be that measured by conventional methods, is introduced. It is shown that the calculation of thermal constriction resistance using a homogeneous apparent thermal conductivity differs from that of a calculation using the full developed analytical solution. This difference is small in the case of very thin plates but becomes very significant with increasing plate thickness.

Backing plate material selection for optimizing joint performance in friction stir welded aluminium honeycomb

Aluminium honeycomb core is a thin-walled cellular structure extensively used in crash resistance applications in automotive industry. To overcome current challenges in adhesive-bonded honeycomb, new fabrication route using micro friction stir lap welding has been proposed. With a specific energy absorption capacity as high as 28.2 kJ/kg in flatwise impact testing, fabricated honeycomb demonstrated its potential for industrial applications. The structure exhibited no weld cracks or cell wall delamination, unlike adhesive-bonded honeycombs. However, in friction stir welding of thin sheets (0.5 mm), achieving an optimized heat input is challenging due to limited scope for variation in process parameter and tool design. Therefore, control of heat outflow by proper selection of backing plate material is the alternative approach for achieving desirable joint performance. Experiments with backing plates having a range of thermal diffusivities demonstrated that joint produced with mild steel backplate exhibited maximum shear-tensile strength. Conversely, joint with aluminium backplate exhibited poor plastic flow of material. Effective sheet thickness and lap width were predominantly affected by heat accumulation in weld, resulting in different failure modes.

The Effect of Laser Beam on the Width of the Cut

Conventional methods of dividing material due to their limitation to straight cuts have largely been replaced by non-conventional cutting methods, which include laser cutting. Laser cutting of polymer materials has become a priority for the manufacturing industry, mainly due to the constantly growing demand for these materials. The article discusses the effect of the laser beam on the width of the cut using lenses with different focal lengths, under different working conditions, on samples made of PMMA polymer material plates. For the experiment, the samples were produced using an ILS 3NM laser device, a CO2, with a wavelength of 10.6 μm and with maximum power 100 W, maximum feed speed 1524 mm · s-1. For the selected samples, it was studied how the dimension defined by the machining software differ from the dimension created by the machining.

Free Vibration Analysis of Porous Functionally Graded Material Plates with Variable Thickness on an Elastic Foundation Using the R-Functions Method

Free vibrations of porous functionally graded material (FGM) plates with complex shapes are analyzed by using the R-functions method. The thickness of the plate is variable in the direction of one of the axes. Two types of porosity distributions through the thickness are considered: uniform (even) and non-uniform (uneven). The elastic foundation is defined by two parameters (Winkler and Pasternak). To obtain the mathematical model of the problem, the first-order shear deformation theory of the plate (FSDT) is used. The effective material properties in the thickness direction are modeled by means of a power law. Variational Ritz’s method joined with the R-functions theory is used for obtaining a semi-analytical solution of the problem. The approach is applied to a number of case studies and validated by means of comparative analyses carried out on rectangular plates with a traditional finite element approach. The proof of the efficiency of the approach and its capability to handle actual engineering problems is fulfilled for FGM plates having complex shapes and various boundary conditions. The effect of different parameters, such as porosity distribution, volume fraction index, elastic foundation, FGM types, and boundary conditions, on the vibrations is studied.

Calculation model and influence factors of thermal conductivity of composite cement-based materials for geothermal well

The use of cement-based composites (CBC) with high thermal conductivity for geothermal well cementing is extremely important for the efficient development and use of geothermal energy. Accurate prediction of thermal conductivity can save a lot of experimental costs and time. At present, there is no specific calculation model for the thermal conductivity of CBC. In this study, the microstructure, thermal conductivity model and influencing factors of CBC were investigated by experimental tests, theoretical analysis and numerical simulation. The results showed that the cement-based material could be simplified into a two-layer structure of hydrated and unhydrated layers. Mathematical and numerical models based on the coupled Series model and the Maxwell–Eucken model were established to calculate the thermal conductivity for CBC. The mathematical and numerical models were found to be more accurate by comparison with the conventional models and experimental test results. The cubic packing was more favorable than the spherical packing to improve the thermal conductivity of CBC. The plate material had significant anisotropy. The thermal conductivity of CBC showed a rapid decrease followed by a slow decrease, a decrease followed by a slow increase and finally a rapid decrease, a rapid increase followed by an up and down fluctuation and finally a plateau, respectively, with the increase of filler particle diameter, spacing and curing temperature. Based on these results, the effective methods and future research directions were proposed to maximize the thermal conductivity of geothermal well cementing materials in actual engineering applications. The research findings can provide some technical references for the efficient development of geothermal energy and research on CBC with high thermal conductivity.

Research on microstructure and mechanical properties of TC4/304 clad plates by asymmetric rolling with local strong stress

In order to solve the problems of complex traditional preparation process and low bonding strength of titanium/steel clad plates, TC4/304 clad plates were prepared by asymmetric rolling with local strong stress (ARLSS), the effect of rolling temperature on the interface bonding of clad plates was studied. The two-dimensional simulation model of TC4/304 clad plates rolling was established by finite element method, and its accuracy was verified by experiments. The experimental results show that the interfacial bonding strength of the clad plates increased with the increasing temperature, but when the temperature reached 950 °C, the brittle intermetallic compounds (IMCs) formed extremely fast, which greatly weakens the bonding strength. The clad plates showed the best bonding strength at 900 °C. After corrugated roll bonding (CRB) (33 % reduction ratio), the bonding strength at the peak was lower than that at the trough. After FRB (46 % reduction ratio), the interface bonding strength was slightly improved. The final peak bonding strength reached 519 MPa, and the trough bonding strength was 527 MPa. The improvement of bonding strength mainly came from the improvement of TC4 matrix strength. The finite element simulation results showed that multiple cross shear zone in the deformation zone of the CRB stage were beneficial to the bonding of dissimilar metals. While the deformation of the clad plates material in the FRB stage was consistent, which effectively avoided the cracking of the bonded area and further improved the bonding strength. Therefore, the strong non-uniform plastic deformation of ARLSS process had a significant effect on the deformation coordination of dissimilar metals and the quality improvement of clad plates.

Classification criteria for austenitic stainless steel H-section under cyclic loading about major-axis

Stainless steel exhibits strain hardening characteristics under cyclic loading, hence presenting significant potential for application in seismic design. However, the current stainless steel structural design code fails to account for this beneficial effect in the cross-section classification. Given the scarcity of research about the behavior of structural stainless steel members under cyclic stress, this paper establishes the preliminary finite element model for the austenitic stainless steel (EN 1.4301) H-section. Firstly, finite element model validation of the existing cyclic tests on stainless steel members from literature was performed, followed by numerical analyses of a total of 370 beam and beam-columns members with different axial compression ratios and plate width-thickness ratios, and subsequently evaluated the cross-section classifications specified in prEN 1993-1-4, AISC 370 and CECS 410 through extensive parametric studies. The results indicate that the current design codes are conservative in the provisions for cross-section classification because they neglect the influence of plate interactions and material strengthening effects during cyclic loading. In this paper, limit and generalized expressions for austenitic stainless steel H-section with different axial compression ratios and cross-section classes under cyclic loading about major-axis are proposed. Additionally, the effect of material strengthening on cross-section classification under cyclic loading is examined.

Super hardening of Fe[sbnd]W alloy plating by phase transformation of amorphous to metal carbides-dispersed nanocrystalline alloys and application as promising alternative for hard chromium plating

Despite the superior hardness, wear resistance, and corrosion resistance of hard chromium (Cr) plating using toxic hexavalent chromium (Cr6+), the gradual restriction on the use of Cr6+ in industrial fields necessitates the development of an alternative, harmless plating material with excellent performance. Here, we report the fabrication of super-hard plating by the simple annealing of electrodeposited FeWC plating as a promising alternative for hard Cr plating. Amorphous-structured FeWC plating, including co-deposited citric acid-derived carbon, forms uniformly dispersed ternary metal carbides inside the plating during annealing, which changes the plating structure from amorphous to nano-carbide-dispersed alloys. The phase-transformed, nanocrystalline FeWC alloy annealed at 700 °C exhibited a maximum hardness of 20.5 GPa, which surpassed the hardness of hard Cr plating (12.5 GPa). The ball-on-disc tribo-test and corrosion test results further demonstrated the superior wear and anti-corrosion properties of the carbide-dispersed FeWC alloy plating compared with hard Cr plating. This study develops the applicability of this super-hard plating as a new hard coating material that overcomes the limitations of conventional metal plating without using any toxic chemical.

Active vibration control of functionally graded material plates integrated with piezoelectric layers using new Q9ɤ approach

Abstract A new efficient approach has been developed to simulate the free vibration, static, dynamic response and active control of functionally graded material (FGM) plates with integrated piezoelectric layers. This approach reinforces the standard first-order shear deformation theory by introducing a novel shear strain fields, alleviating the problem of shear locking, especially in the analysis of thin structures. These new fields accurately predict the shear strain fields, satisfying both compatibility and equilibrium equations while requiring less mesh refinement. Furthermore, this current approach provides higher performance and precision in analysing FGM structures. Additionally, a feedback control system has been implemented using either total piezoelectric layers or partial covering (patch) as actuators and sensors in both static bending control and dynamic vibration control analysis. The present work strengthens the basic techniques for further research in finite element analysis across a broader spectrum of materials and applications.

Fatigue Crack Propagation in 5754 Aluminum Alloy under Four-Point Bending

The aluminum 5754 alloy is one of the widely used engineering materials in shipping, rivet making, tread plates and automotive industries. These engineering structures envisage variable loading conditions during their service. In addition to it, it is also experiencing seismic vibrations. Hence, the engineering components made from such aluminum alloy are susceptible to fatigue fracture. In the current study, the prediction of fatigue crack growth (FCG) in 5754 aluminum alloy was made using the exponential function. The beam specimen comes up with a cross-section of 25X25 mm2, a span length of 300 mm with a mechanical notch length of 2.70 mm at the centre was subjected to four-point bending (FPB) employing hydraulic INSTRON 8800 tensile testing apparatus. The periodic loading condition deformed the material up to large plastic deformation. The applied load was further down the elasticity of the material. The experimental data provided the relation between crack length (a) to the number of cycles (N) to failure. The response surface methodology (RSM) and modified exponential equation were used to predict the FCG. In RSM, when “stress intensity factor (K)” and “number of the cycle (N)" were considered independent variables, the response (a) was optimum (maximum) as compared to when “stress intensity factor range (del K)” and “fatigue crack growth rate (da/dN)” were considered independent variables. Hence, for designing the aluminum 5754 alloys as engineering structures, it was the number of cycles which provides a safe design as compared to da/dN. The modified exponential equation using an exponential function predicted the FCG for aluminum 5754 alloy in the form of a beam specimen. The anticipated results agreed with experimental data as the prediction ratio was 1.20 and the % deviation was 3.7.

Hardness Test Analysis on ST 37 Steel Plate Material and Aluminum Using the Brinell Test Method

One of the most frequently used methods of material testing is hardness testing. The aim of conducting research on material hardness is to determine the hardness value of the material specimens tested, namely ST 37 steel plate and aluminum plate. The test method is to use the Brinell hardness test where the values ​​obtained during testing are from the force load, indenter diameter and pressure trace diameter and the pressure time that has been determined. By using testing tools such as hardness tester, mechanical caliper, indenter, flat file, stopwatch. And the materials used are ST 37 steel plate, aluminum plate and sandpaper. From the test results obtained we can calculate the Brinell hardness value of the test material. The value from the calculation of test data where the highest hardness value using the Brinell method (BHN) for ST 37 steel plate material is 256.992. Meanwhile, the highest hardness value using the Brinell method (BHN) for aluminum plate material is 55,182.