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Handling plastic waste through recycling allows extending the life of polymeric materials, avoiding recurrence to incineration or landfilling. In contrast with traditional mechanical recycling technologies, chemical recycling enables the obtention of the virgin monomers by means of depolymerisation to create new polymers with the same mechanical and thermal properties as the originals. Research presented in this paper is part of the polynSPIRE project (Horizon 2020 European funding programme) and develops and scales-up a heated reactor to carry out the depolymerisation of polyamide-6 (PA6), polyamide-6,6 (PA66) and polyurethane (PU) using microwave (MW) technology as the heating source. The purpose is to design and optimize a MW reactor using up to eight ports emitting electromagnetic waves. Finite element method (FEM) simulation and optimisation are used to design the reactor, considering as parameters the data obtained from experimental dielectric testing and lab-scale characterisation of the processes and materials studied. Two different COMSOL Multiphysics modules are involved in this work: Radio Frequency (RF) and Chemical Reaction Engineering (RE), to simulate the reactor cavity using two frequency levels (915 MHz and 2.45 GHz) with a power level of 46 kW, and the chemical depolymerisation process, respectively. A sensitivity study has been performed on key parameters such as the frequency, the number of ports, and position inside the reactor to consolidate the final design. It is expected that these results assist in the design and scale-up of microwave technology for the chemical recycling of plastics, and for the large-scale deployment of this sustainable recovery alternative.

This work aims to characterize printing structures with various infill densities composed of a thermoplastic material containing magnetic particles composed of mainly Iron(III) oxides with regard to their possible processing with the additive technology of Fused Filament Fabrication. A polyethylene terephthalate glycol (PET-G) structural thermoplastic with the addition of Iron(III)) oxides has been selected, and correct processing temperatures have been determined using thermal analysis. The paramagnetic properties of printed products consisting of different filling densities have been tested. Relative permeability has been identified to be strongly dependent on the printed internal structures of tested products. The samples composed of the densest structure have shown relative permeability higher by 18% with respect to the sample printed with the least dense structure. Finite Element Modelling (FEM) simulations have been applied to determine magnetic field distributions and, moreover, to calculate the holding forces of all printed samples. The performed simulations confirmed that produced composites might be utilized as magnetic switches and sensors or as more advanced components for homogenizing electric motors’ magnetic fields. Moreover, magnetic properties might be tuned according to the specific needs printing structure with the suitable density.

Carbon fiber-reinforced plastics (CFRPs) are widely used in recreational products and industrial components. Ultrasound is a powerful tool to ensure the safety of CFRP structures, but the ultrasonic velocity on CFRP depends on the frequency and direction of propagation. Understanding ultrasonic propagation is the key to its proper application to CFRP structures. In the present work, experiments, 3D FEM simulations, and theoretical analyses were performed to investigate Lamb wave propagation on CFRP plates. The simulation and experimental results agreed well, proving that the FEM simulation results were reliable. On the basis of this reliability, further results were obtained for various fd values. The S0 mode's group velocity was considerably affected by the propagation direction, but the A0 mode exhibited minimal dependence. In addition, unexpected waves were observed in the simulation and identified as the SH0 mode. A new approach for determining the theoretical group velocity was also presented. [ABSTRACT FROM AUTHOR]

The characterization and modeling of Ceiba plywood delamination requires extensive experimental and numerical study. A data reduction scheme, based on the compliance method and the concept of equivalent crack, is utilized. This method has two main advantages over conventional methodologies: it does not require crack monitoring during propagation and takes into account the effect of the fracture process zone at the crack tip. The characterization of delamination and the mechanical behavior of adhesive joint are influenced not only by the adhesive properties but also by the characteristics of the interface. Various modeling methods have been proposed to characterize the delamination of laminated materials. Among the most widely used methods is the cohesive zone model, which is based on fracture mechanics and damage theory and allows for an adequate prediction of the onset and propagation of the delamination simultaneously. This method consists of introducing a cohesion law in finite element modeling. Often, the determination of these parameters is obtained iteratively by matching the numerical results with the experimental results. In this study, the cohesive parameters of the bilinear traction–separation laws in each pure mode were determined. This identification was achieved through the design of experiments method and the Kriging metamodel. A finite element modeling of the Ceiba plywood delamination was then performed. The experimental tests carried out make it possible to assess the delamination resistance under mode I, mode II and mixed mode I + II loading. Following the description of the experimental procedure, the experimental and numerical results are presented and compared. Finally, the response to the delamination was represented by a semi-empirical criterion and an analysis of fracture surfaces was performed and interpreted. [ABSTRACT FROM AUTHOR]

In this study, the optimum position and minimum diameter of damping wire were investigated to maximize the fundamental frequencies of a rotating blade. The blade was modeled as an isotropic, homogenous and constant cross-sectional cantilever rotating beam. The damping wire was modeled as an intermediate elastic support. In most rotating-beam applications, such as turbine blades, the slenderness ratio is low; therefore, Timoshenko beam theory was selected to analyze the model. The optimal position and minimum stiffness of elastic support were determined to maximize the natural frequencies of the beam using the finite element method. Minimum diameter of the damping wire was calculated by determining the minimum stiffness. Parameter sensitivity analysis showed that the angular velocity of the blade has no remarkable effect on the optimal position and minimum diameter of damping wire. [ABSTRACT FROM AUTHOR]

The deformation behavior and microstructure evolution of a novel Mn-containing HEA were explored during the deformation temperature ranges of 800∼1100 °C, and strain rate ranges of 0.001∼1s−1. The study results indicate that the true stress-strain curves after work hardening exhibit continuous softening type at low strain rate ranges of 0.001–0.01 s−1, while softening then steady-state type at high strain rate ranges of 0.1∼1s−1, respectively. The activation energy (Q) and stress exponent (n) are calculated to as 404.6 kJ/mol and 4.9016, respectively. As the strain increases, the flow instability is prone to expand towards the regions of lower strain rate and higher deformation temperature, and the optical processing window is determined at 1050–1100 °C and 0.001–0.002 s−1. The strain and stress field distribution of the FEM simulations reveal the inhomogeneous deformation and the damage field distribution predict the crack region of deformation specimen. The critical (ε c)/peak strain (ε p) for DRX do not display a proportional relationship with strain rate and an inversely proportional relationship with deformation temperature, and the relationship between ε c and ε p can be expressed as: ε c = (0.3–0.5) ε p. Only the discontinuous dynamic recrystallization (DDRX) mechanism is activated in the whole range of deformation conditions, but it is not fully carried out. Because of the inhomogeneous stress distribution, the dynamic recrystallized grains show bimodal grain size. Furthermore, the recrystallized grains do not grow significantly due to the synergistic contribution of sluggish diffusion effect, high solution hardening effect and the trimodal B2 precipitate phase distribution. [Display omitted] • The relationship between ε c and ε p can be expressed as: ε c = (0.3–0.5) ε p. • Because of the inhomogeneous stress distribution, DRX behavior is not carried out adequately, resulting in bimodal grain size. • Recrystallized grains do not grow significantly due to sluggish diffusion, high solution hardening effect and the B2 precipitate trimodal distribution. [ABSTRACT FROM AUTHOR]

Failure assessment is one of the fundamental tasks for optimization of composite pressure vessels (CPVs). However, the extensive design space of composites usually leads to costly and repetitive work of failure assessment that hinders the design and optimization of CPVs. In this work, a combined FEM simulation and machine learning approach is used to predict the failure factors R of CPVs for further optimization. CPVs with various design parameters are automatically generated and analyzed in ABAQUS to obtain failure factors under various external loadings. Then, an assembled deep neural network (DNN) namely Multi-DNN is trained to map relations between design parameters and R of CPVs. Further, transfer learning (TL) is introduced to improve the extensibility of our approach by fine-tuning the pre-trained Multi-DNN using scarce data of new design space. Such a TL-Multi-DNN model can precisely predict R of CPVs with new design parameters. Additionally, combining the trained models and genetic algorithm, the optimization of CPVs is carried out with high efficiency and low computational cost. As a result, R of CPV with various given and new design parameters can be estimated directly by the trained models and the optimal layer sequence of CPV can be obtained efficiently. [ABSTRACT FROM AUTHOR]

In this work an extensive characterization over XeCl multishot laser irradiation was performed at different energy densities and with different thicknesses of graphitic coating superimposed on P and Al implanted 4H–SiC epitaxial layers. It was noted that at 0.6 J/cm2 the 180 nm coating provides a smooth surface unlike lower thicknesses or uncoated treatments. The μ-Raman investigation showed the crystalline quality as a function of the energy density. Through Medium Angle Annular Dark Field-Scanning Transmission Electron Microscopy (MAADF-STEM) and High Angle Annular Dark Field (HAADF)-STEM investigations, the absence of extended defects and the presence of regions with higher density of carbon interstitials (C i) was revealed. Circular Transfer Length Method (CTLM) measurements demonstrated how irradiation at 0.9 J/cm2 succeeded to reach values of (7.28 ± 1.15) × 102 Ω/sq, lower than the findings achieved with furnace treatment at 1650 °C. However, electrical characterization carried out through μ-Raman investigation over the Folded Transverse Acoustic (FTA) modes showed consistent activation of the order of 7 × 1019 cm−3 at 0.6 J/cm2 while exhibited CTLM extracted sheet resistance of (3.17 ± 0.06) × 104 Ω/sq. Therefore, this work highlights the contrast between fast processes as the accommodation and ionization of dopant atoms in substitutional positions and slow processes such as the recovery of ion implantation damage. By offering faster processing rates, lower thermal budgets, and high spatial control over the annealing process, laser annealing on 4H–SiC as a post-implantation thermal treatment approach presents several advantages over conventional annealing methods. This study marks a significant progress in comprehending and improving the effectiveness of laser annealing on 4H–SiC. [Display omitted] [ABSTRACT FROM AUTHOR]

Residual stresses are an important factor in the performance and stability of welded structures. This study investigates the characteristics and significance of residual stresses in MAG-welded ultrahigh-strength steel rectangular hollow sections. The research incorporates comprehensive X-ray diffraction residual stress measurements, electron backscatter diffraction analysis, statistical analyses, and finite element method simulations to provide valuable insights into the behaviour of welding residual stresses. The results reveal clear microstructural variations between the cold-formed corner and the flat side of the rectangular hollow section caused by welding heat input, emphasizing the need to consider these variations in residual stress assessments. Furthermore, the study examines the dependence of residual stresses on the steel grade, with higher strength steel exhibiting compressive stresses and lower strength materials experiencing tensile stresses in corner areas. Statistical analysis indicates that welding sequence and direction have negligible effects when applying the employed welding sequence. In any case, higher heat input leads to significantly larger residual stresses. Finally, the study presents a novel analytical model based on validated finite element simulations to predict the maximum variation of residual stresses depending on welding heat input. The findings provide valuable insights into the significance of welding residual stresses and their predictability. The comprehensive measurements, simulations and proposed models contributes to a better understanding of residual stress phenomena, facilitating the development of reliable design guidelines for welded structures in various engineering applications. [Display omitted] • S700 and S960 UHSS hollow sections were welded and XRD-measured. • Residual stresses in cold-formed corner depends on steel grade: more compressive in S960 steel. • S700 steel contains higher welding residual stresses with relative to yield strength. • Welding FEM-simulation with initial residual stress state was validated by XRD-results. • Novel analytical models are proposed for predicting residual stresses in UHSS hollow sections. [ABSTRACT FROM AUTHOR]

Laser cladding (LC) of industrial parts with tungsten carbide (WC)/Inconel 625 composite is highly regarded for its unique properties, for applications such as repair and improvement of surface and mechanical properties. In order to achieve high quality cladding, with minimal impact on the metallurgical structure and minimal stress and distortion caused by high local heating and cooling rate, it is necessary to determine the important parameters of the process, evaluate and investigate the effect of each one. Today, the numerical solution of this process can help predict, understand and evaluate the characteristics of the LC, and control and optimize it. In this research, using the thermo-elastoplastic simulation of the WC/Inconel 625 composite cladding process using finite element method (FEM) and the arbitrary Lagrangian-Eulerian (ALE) solution method with moving mesh strategy, the properties of the created coating have been evaluated. The laser is modeled with a moving Goldak double ellipsoidal heat source and the physical and mechanical properties of the temperature-dependent materials are considered. The physical and mechanical properties of the composite were extracted from the role of mixture and Ashby's method, respectively. Using Taguchi's experimental design method, the effect of important process parameters on output parameters such as dilution, cladding geometry, heat and stress have been investigated. Finally, the optimal parameters as well as the relationship between the parameters and each characteristic have been obtained using the linear regression model. • Three-dimensional thermo-mechanical finite element model has developed to simulate the WC/Inconel 625 composite laser cladding. • Utilizing the Taguchi strategy and ANOVA method, the optimal parameters and the effect of each on the outputs have clarified. • The generalized linear models for predicting the dilution, cladding width, maximum temperature, and maximum stress are proposed. • Calculated melt pool zone profile is in good agreement with the experimental result. [ABSTRACT FROM AUTHOR]

Abstract The objectives of this study were to characterize and evaluate the physical and mechanical properties of an experimental zirconia for dental application and compare the biaxial flexural strength results with the finite element simulation (FEM). Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramic samples were sintered at 1475 °C/2 h and characterized by X-ray diffraction, scanning electron microscopy, relative density, flexural strength using piston-on-three balls (P-3B) test and Young’s modulus. From the flexural strength results, numerical simulations were performed using Abaqus software. The complete model used 70216 elements, considering the components of the test. The results indicated full densification of sintered samples, ZrO2-tetragonal and ZrO2-cubic as crystalline phases, and average grain size of 0.6±0.2 μm. Mechanical characterization of sintered samples indicated Young’s modulus of 195±4 GPa, flexural strength of 1191±9 MPa and Weibull modulus m=16.3. FEM simulation indicated a flexural strength close to 1100 MPa, with a difference lower than 7% in relation to the experimental results. The results were compared associating the physical and mechanical properties of Y-TZP with its intrinsic phenomena such as tgm transformation and ferroelastic domain.

This work aims to develop a light symmetrical structure that can be realized through rapid prototyping techniques. The structure must meet some restrictions imposed by possible practical applications. It must withstand a moderate load, be able to adapt to a specific external shape, be relatively light, allow the execution of some changes according to user requirements, allow execution with the help of owned equipment, and allow relatively fast production (its structure and form). The major application for which the structure is designed is that of an exoskeleton for medical rehabilitation, realized by the authors. The creation of such an exoskeleton is followed by a series of research regarding different aspects of acceptability, reliability, ease of use, and the shortcomings that such a structure can cause. In this study, the authors focused on the mechanical part of the exoskeleton realization, which would fulfill some imposed kinematic and constructive conditions.

The folded sandwich structure might inevitably be impacted at low velocity when it is working, which will lead to the decline of the mechanical properties. The low-velocity impact resistance of the double-layer V-shaped aluminium folded sandwich structure is researched by the finite element method. It was found that the damage mode and the proportion of energy absorption of the double-layer and single-layer folded sandwich structures are different under low-velocity impact, and the impact stiffness and energy-absorbing capacity of the double-layer structure are better than those of the single-layer structure when the impact energy is small. In addition, in view of the low-velocity impact response characteristics of the double-layer V-shaped aluminum folded sandwich structure, two methods are proposed to improve its impact stiffness. Both methods ensure that the total mass of the structure remains unchanged. One method keeps the inner panel still and changes the wall thickness distribution of the top and bottom cores, and the wall thickness of the top core is increased. The other method keeps the wall thickness of the cores unchanged, and the inner panel is moved upward. From the finite element results, it can be seen that after increasing the wall thickness of the top core from 0.25 mm to 0.4 mm, the maximum impact distance of the impactor decreases by 30.3% when the impact energy is 5 J, and it decreases by 23.1% when the impact energy is 10 J, and with 20 J, it decreases by 14.5%. After reducing the height of the top core from 12.5 mm to 5 mm, the maximum impact distance of the impactor is reduced by 22.86% when the impact energy is 5 J, 21.85% when the impact energy is 10 J, and 20.51% when the impact energy is 40 J. The improvement is obvious. The two methods can increase the equivalent density of the top core, which can increase the stiffness of the top core. For the double-layer structure, the stiffness of the top core near the impact point has a greater influence on the low-velocity impact resistance of the entire structure.

To obtain excellent mechanical properties from large cross-sections of plastic mould steel (SDP1), we conducted multi-directional forging (MDF) to control the microstructure of ingots. To investigate the microstructural evolution of SDP1 steel during MDF, we performed hot forging at 1150 °C using a THP01–500A hydraulic press. The dimensions of the specimens were Φ38 mm × 80 mm. The microstructure of the specimens after forging was observed under a metallographic microscope. Furthermore, the results of the finite element method (FEM) simulations were employed to improve the quality of the forgings. The predicted results agreed well with the experimental ones, indicating that FEM is effective for analysing microstructural evolution during MDF. Thus, MDF for large cross-sections of SDP1 steel (Φ1000 mm × 2200 mm) was simulated. The results showed that the average grain size of SDP1 steel at the core of an ingot after MDF ranged from 40.6 to 43.3 μm. Although this was slightly higher than the grain size of the sample after traditional upsetting and stretching forging (TUSF) (35.7–46.0 μm), the microstructure of the SDP1 steel sample after MDF was more uniform than that after TUSF. Compared with TUSF, MDF not only refines the grain size but also improves the microstructure uniformity of the sample.

Knowledge about the adhesion of protective hard coatings on tool materials is of great importance to understand their failure mechanisms in metalworking. Until now, common techniques such as scratch and indentation tests are used to establish a qualitative ranking of a coating’s adhesion on various substrate materials. Nevertheless, there is a lack of quantitative measures to describe the strength of the interfaces between individual microstructural constituents of substrate-coating composites. The current work investigates the interfacial strength and thus the adhesion of TiN deposited as a hard coating on an MC-type carbide, an M6C-type carbide and on martensite being constituents of high speed steels. Tensile stresses were introduced at the interface between TiN and the individual microstructural constituents of a high speed steel via micromechanical testing of a novel MSC specimen within a scanning electron microscope. The tested MSC specimens were subsequently investigated in detail by scanning electron microscopy. Evaluation of the interface stress at fracture via finite element analysis yielded a ranking in interface strength and therefore coating adhesion in a sequence from high to low strength values from MC/TiN over M6C/TiN to martensite/TiN.

In recent years, the interest in monitoring the operating conditions of freight wagons has grown significantly to improve the safety of railway vehicles. The railway research group of the Politecnico di Torino has been working for years on the development of solutions to effectively monitor the operating conditions of passenger and freight rail vehicles. As part of the national Cluster ITS Italy 2020 project funded by Italian ministry of education, university and research (MIUR), the Politecnico di Torino has collected a considerable amount of data thanks to the wired and wireless prototypes developed. The data obtained are used in this paper for the validation and calibration of a finite element (FE) model that simulates the temperature variation of a cast iron brake block due to braking operations of an intermodal freight wagon. The developed model can be a useful tool to predict the temperature at the wheel–shoe interface as a function of the current operating conditions since a direct measurement is not easy to perform. [ABSTRACT FROM AUTHOR]

The micro single-lip deep hole drilling process is subjected to many difficulties. Especially the machining of difficult-to-cut materials like the nickel-based alloy Inconel 718 results in high thermal and mechanical loads. Irregularities in the drilling process, which lead to early tool failures must be avoided. A major challenge for micro single-lip deep hole drilling is to generate favorable chips and guarantee good chip removal. Since the chip flute of single-lip deep hole drilling tools is straight, the only mechanism to transport the chips and remove them from the bore hole is the coolant flow. In this paper the mechanical loads and the resulting chip formation for various cooling lubricant pressures are analyzed using tools with a diameter of d = 2 mm. In the experiments feed force, drilling torque, tool wear, bore hole quality as well as diameter and roundness deviations were evaluated. Individual chips are digitized and prepared as CAD models for the future consideration of the chip removal in flow simulations of the cooling lubricant. Additional FEM computational analyses of the three-dimensional chip formation with a geometric representation of the chip shape were carried out. This way not only provides valuable validated information about the process and the chip formation but also creates a basis for further investigations, which will allow an innovative simulation of the coolant flow and considers the chip formation and the chip shape. [ABSTRACT FROM AUTHOR]

This study aimed to assess particle swarm optimization (PSO) optimized with an adaptive network-based fuzzy inference system (ANFIS) for the prediction of the ultimate bearing capacity of strip footing resting on a sloping crest. To make datasets, a 2524 finite element model (FEM) simulation analysis was performed. In this sense, the k-fold validation technique selected for the selection of the testing and validation purposes. Also, the variables of the ANFIS algorithm (i.e., the number of clusters), and the PSO algorithm (the population size were optimized using a series of trial and error process. The second main objective of the current study was to assess the applicability of PSO–ANFIS in estimating the ultimate bearing capacity of the strip footing resting on a single cohesionless slope when it was subjected to an external vertical applied stress. The input parameters were the soil properties (Stype) (classified into five different classes from the weakest, shown as S1, to the strongest type, displayed in higher order), slope angle (β), setback distance ratio (b/B) (the distance of the footing from the slope crest to the footing width), and vertical settlement (Uy) of the footing, while the main output was the applied vertical stresses (Fy) that can be applied on the footing. Note that the ultimate bearing capacity (Fult) is the maximum vertical stress when Uy = 0.1 B. A thorough comparison between the measured FEM simulations, the proposed ANFIS and PSO–ANFIS models were carried out to demonstrate their effectiveness in predicting a reliable Fult resting on cohesionless slopes. [ABSTRACT FROM AUTHOR]

In this work, residual stresses arising after an industrial TIG welding process on an aerospace grade part are investigated. The customer demand for high product resistance and high dimensional accuracy calls for the control of the welding process and the minimisation of the residual stresses. Dimensional check of manufactured parts was traditionally performed in a quality room by means of coordinate measuring machines (CMM). For parts larger than 1 meter, this operation shows several issues, as the handling and the need for large and expensive measuring devices. These needs can be fulfilled by an innovative method that, through continuous dimensional check, allows to optimise the welding process parameters. This method is built on a post-process measurement of part shrinkage based on a Computer Vision technique, the outcome being a 3D reconstruction of the actual part. Moreover, the whole procedure is low-cost and time saving, as it can be performed with a conventional camera mounted on a tripod. A Finite Element Model (FEM) of the TIG process on the selected sample was developed. The result of the numerical model was compared with the Computer Vision-based post-process measurement. The simulation scenario predicted by Finite Element Analysis agrees with measurements. [ABSTRACT FROM AUTHOR]

Objective: The use of a close-fitting roughly head-shaped volume coil for MRI (magnetic resonance imaging) has the merit of improving the filling factor and thus the SNR (signal-to-noise ratio) from the brain. However, the surface of the RF coil follows that of the head which makes it difficult to determine an optimal coil winding pattern. We describe here a new method to optimize a head-shaped RF coil with the objective of maximizing its SNR and RF-magnetic-field homogeneity for operation at ultra-low magnetic field (6.5 mT, 276 kHz). Methods: The approach consists of FEM (finite-element-method) simulation and linear programing based optimization. Results: We have implemented the optimization and further studied the relationship between the design requirements and the performance of the RF coil. Finally, we constructed an optimal RF coil and scanned both a head-shaped phantom and a human subject. Conclusion: The method we outline here provide new insight into the conductor layout needed for magnetic optimization of structurally complex coils, especially when tradeoffs between competing attributes (SNR and homogeneity in this case) must be made. [ABSTRACT FROM AUTHOR]

The article by Tae-Gu Kim et al. conducted elastic FE modeling, which was inappropriate for fracture of elastic-plastic chain material (11.3% of elongation). FE analysis results and the findings in the fractographic analysis did not tally but contradicted each other. The article identified “incorrect installation”/ bending forces as the root cause while FE results of the chain under bending forces showed very low stresses at fracture locations but the highest stress in the middle of shank of the chain. The article's “step-like topographies indicating the fracture due to bending moment rather than uniaxial tension” lacked scientific support. The load value carried by each chain section under bending/incorrect installation was only half of that under tension, thus the article using same load value in FE simulation comparison for bending and tension was incorrect. The real cause of the chain fracture was likely improper checking the lifted load or/and using the wrong chain with much lower safety working load.

Grain loss in the harvesting process of combine harvesters not only causes economic losses to farmers but also affects the soil environment because of the lost grain covering the soil, influencing crop growth in the next season. Grain sieve loss-monitoring sensors represent an important accessory in combine harvesters, as they can not only provide current grain loss levels for the operator to adopt a rational action in time but also serve as an important performance signal for the control system. To reflect the rice grain sieve loss level of combine harvesters in real time, an indirect grain sieve loss-monitoring system is proposed in this paper. First, the grain collision rise time was obtained by the finite element method (FEM), and the parameters of the grain loss sensor signal processing circuit were determined accordingly to upgrade the monitoring accuracy. Then, grain loss distribution behind the cleaning shoe was analyzed in detail under different working parameters. Grain loss distribution functions at the end of the sieve and a monitoring mathematical model with relevant variables were established based on the laboratory experiment results. Finally, calibration experiments were carried out to verify the measurement accuracy of the sensor on a cleaning test bench, with an obtained relative monitoring error ≤6.41 % under different working conditions.

The aim of the article is to present a new idea of limiting the bearing voltage in electric machines with permanent magnets through the use of a shielding winding placed in stator slot wedges. The first part of the article is dedicated to the mechanisms of generating bearing voltages when the machine is supplied from the mains and from a power electronic converter. Additionally, some methods of counteracting these phenomena were described. Next, multivariant simulation tests were carried out based on the two-dimensional field model of a synchronous machine with permanent magnets. The tests were run in order to determine the internal capacitances of the machine, on which the level of bearing voltages depends. Based on these results, the optimal variant of the design solution ensuring the limitation of the bearing voltage to a safe level was selected. Using the model of a two-level converter and based on the equivalent diagram of the internal capacitances of the machine, the influence of the proposed shielding winding on the bearing voltage was estimated.

Borate glass (80B 2 O 3 –20Bi 2 O 3 in mol.%), which had a coefficient of thermal expansion (CTE) that was exceptionally compatible with that of sapphire, was designed and used as a braze to join sapphire. Prior to joining, various thermodynamic properties of the glass were investigated. Brazing was conducted at 600–750 °C, and the influence of the brazing parameters on the microstructural evolution and mechanical properties of the joints were investigated. The results showed that two crystalline phases, Bi 6 B 10 O 24 and Bi 48 Al 2 O 75 , were formed in the joint due to crystallization within the glass, which could strengthen the joint. The maximum shear strength, 55.5 MPa, was achieved for the joint that was brazed at 725 °C for 20 min. The finite element method (FEM) was utilized to simulate the shear stress during cooling. Analysis of the residual stress in the FEM simulation showed that the shear stress was mainly concentrated near the sapphire/glass interface. [ABSTRACT FROM AUTHOR]

The main purpose of the current study was to investigate the effects of the size of WC grains on the damage evolution of WC–Co junk mills. The finite element method (FEM) simulation results showed that the fine-grain (FG) tool retained its cutting edges radii longer than the coarse-grain (CG) tool. This event leads to the larger wear rate in the CG tool. Moreover, FEM analysis indicated that through increasing the feeding rate, the wear rate and the cutting forces increased as well. The observation of worn tool surface revealed that the formation of micro-pits, micro-cracks, scratching grooves and broken WC grains was among the common signs of the damage for both CG and FG tools. However, it was found that the defects are more intensive in the CG tool. This can be due to the lower boundary strength and less WC connectivity in the CG milling tool. The finer grains also decreased the mean free path in the Co binder and impeded the micro-cracks propagation in the material. [ABSTRACT FROM AUTHOR]

There is an increasing demand for microgrooves in optical systems with a pitch at wave length level. Precision glass molding (PGM) is one of the most efficient methods for fabricating microgrooves on glass surface. Nickel–phosphorus (Ni–P) exhibits excellent cutting properties and is developed as the mold material for glass microgrooves. However, the phosphorus in Ni–P mold tends to diffuse into the glass during the PGM process at high temperatures, which may reduce the optical performance of the molded glass microgroove component. In addition, the atomic diffusion increases the interface friction coefficient between the glass and the mold, resulting in the decrease of molding accuracy of the microgroove array. To solve these problems, a rhenium–iridium (Re–Ir) alloy coating is deposited on the surface of the Ni–P microgroove mold by ion sputtering. In this paper, the surface roughness of the mold before and after coating with Re–Ir alloy coating is investigated. The mechanical properties of Ni–P and the Re–Ir alloy coating are obtained using a combination of finite element method (FEM) and experimental tests. The mold deformation after heating to the molding temperature is analyzed. The results show that the mechanical properties of the Ni–P mold surface can be strengthened after being plated with Re–Ir alloy coating, the Re–Ir coating isolates the diffusion of phosphorus from the Ni–P mold, and improve the forming accuracy of glass microgrooves. [ABSTRACT FROM AUTHOR]

Conventional pathogenic bacteria-detection methods are lab-bound, time-consuming and need trained personnel. Microelectrodes can be used to recognize harmful microorganisms by dielectric impedance spectroscopy. However, crucial for this spectroscopy method are the spatial dimensions and layout of the electrodes, as the corresponding distribution of the electric field defines the sensor system parameters such as sensitivity, SNR, and dynamic range. Therefore, a variety of sensor models are created and evaluated. FEM simulations in 2D and 3D are conducted for this impedimetric sensor. The authors tested differently shaped structures, verified the linear influence of the excitation amplitude and developed a mathematical concept for a quality factor that practically allows us to distinguish arbitrary sensor designs and layouts. The effect of guard electrodes blocking outer influences on the electric field are investigated, and essential configurations are explored. The results lead to optimized electronic sensors in terms of geometrical dimensions. Possible material choices for real sensors as well as design and layout recommendations are presented. [ABSTRACT FROM AUTHOR]

Two-point incremental forming (TPIF) shows higher forming limits than single-point incremental forming (SPIF) especially for producing complex industrial functional components. However, unexpected failure still occurs occasionally under certain forming conditions in TPIF. In this paper, the applicability of six damage models for failure prediction in TPIF is evaluated. The procedure of damage parameter calibration and finite element modelling are presented. The predicted failure depth and location with these damage models are evaluated under different loading conditions. Furthermore, the stress and strain and damage evolution in TPIF are provided and discussed in detail. It is concluded that the failure location and depth can be predicted more accurately by the Ayada model than others in this work. It is noted that once double-sided contact occurs in TPIF, it reduces the variation of triaxiality through the thickness, altering the accumulation of damage. [ABSTRACT FROM AUTHOR]

A new terrestrial gravitational wave detector, Superconducting Omni-directional Gravitational Radiation Observatory (SOGRO), has been proposed in 2016 and seen as a competitive candidate of middle-frequency gravitational wave detector. In this detector, there are three pairs of 5-ton low-temperature superconducting test masses separated by 30–50 m and magnetically levitated by superconducting coils carrying persistent currents. To get a sensitivity of 10− 19 − 10− 20Hz− 1/2, the levitation frequency of the test masses need to be as low as 0.01 Hz. Because of the machining and assembling errors, the levitation coil will tilt with respect to gravity and deviate from the center of the levitation coil. Alignment coils can cancel the tilt but bring extra stiffness to the test mass that enlarges the frequency. We numerically have studied a downscaled prototype of the superconducting magnetic levitation of SOGRO and find a possible design of the superconducting levitation system, which can reduce the levitation frequency to less than 0.01 Hz without increasing any hardware and complexity of the system. This study will benefit the development of SOGRO and other superconducting levitation devices. [ABSTRACT FROM AUTHOR]

One of the most dominant manufacturing methods in the production of electromechanical devices from sheet metal is punching. In punching, the material undergoes plastic deformation and finally fracture. Punching of an electrical steel sheet causes plastic deformation on the edges of the part, which affects the magnetic properties of the material, i.e., increases iron losses in the material, which in turn has a negative effect on the performance of the electromagnetic devices in the final product. Therefore, punching-induced iron losses decrease the energy efficiency of the device. FEM simulations of punching have shown significantly increased plastic deformation on the workpiece edges with increasing tool wear. In order to identify the critical tool wear, after which the iron losses have increased beyond acceptable limits, the simulation results must be verified with experimental methods. The acceptable limits are pushed further in the standards by the International Electrotechnical Commission (IEC). The new standard (IEC TS 60034-30-2:2016) has much stricter limits regarding the energy efficiency of electromechanical machines, with an IE5 class efficiency that exceeds the previous IE4 class (IEC 60034-30-1:2014) requirements by 30%. The simulations are done using Scientific Forming Technologies Corporation Deform, a finite element software for material processing simulations. The electrical steel used is M400-50A, and the tool material is Vanadis 23, a powder-based high-speed steel. Vanadis 23 is a high alloyed powder metallurgical high-speed steel with a high abrasive wear resistance and a high compressive strength. It is suitable for cold work processing like punching. In the existing literature, FEM simulations and experimental methods have been incorporated for investigating the edge deformation properties of sheared surfaces, but there is a research gap in verifying the simulation results with the experimental methods. In this paper, FEM simulation of the punching process is verified using an electrical steel sheet from real production environment and measuring the deformation of the edges using microhardness measurements. The simulations show high plastic deformation 50 μm into the workpiece edge, a result that is shown to be in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Solid municipal waste (MSW) management is solved differently in many countries around the world, given their degree of development. There are countless systems for collecting, transporting and storing collected waste. Most machines for MSW collection are equipped with pre-compaction and compaction systems to reduce the volume of waste and transport a larger quantity over distances that often do reach several tens of kilometers. Vehicles for the collection and transport of waste are equipped with complex systems comprising: loading of containers, taking over and precompacting the material, compacting in the body of the structure and finally unloading in warehouses of the collected waste. Compacting is the process by which the volume of waste is reduced and this occurs through movements of the active organs and waste, in a complex structure located on the autochassis. The equipment is designed to collect / compact and transport in an economical and sanitary safety, pre-collected waste in generators. [ABSTRACT FROM AUTHOR]

Electrodes are crucial for controlling the movements of biohybrid robots, but their external placement outside muscle tissue often leads to inefficient and non-selective stimulation of nearby biohybrid actuators. To address this, we propose embedding pillar electrodes within the skeletal muscle tissue, resulting in enhanced contraction of the target muscle without affecting the neighbor tissue with a 4 mm distance. We use finite element method simulations to establish a selectivity model, correlating the VI E (volume integration of electric field intensity within muscle tissue) with actual contractile distances under different amplitudes of electrical pulses. The simulated selective index closely aligns with experimental results, showing the potential of pillar electrodes for effective and selective biohybrid actuator stimulation. In experiments, we validated that the contractile distance and selectivity achieved with these pillar electrodes exceed conventional Au rod electrodes. This innovation has promising implications for building biohybrid robots with densely arranged muscle tissue, ultimately achieving more human-like movements. Additionally, our selectivity model offers valuable predictive tools for assessing electrical stimulation effects with different electrode designs., (© 2024 IOP Publishing Ltd.)

A shear mode piezoelectric energy harvester for harvesting energy from rotary motion is developed. The kinetic energy in the form of rotation is converted into electrical form of energy by piezoelectric principle with oscillation of piezoelectric patch through magnetic shear force. Efforts have been made to increase the output power using shear mode of operation. In order to estimate the induced voltage of piezoelectric patch, a mathematical model and an Finite Element (FE) model are developed. Considering various parameters, optimization of the harvester was made. Analytical and Finite Element Method (FEM) results are compared and good agreement has been found. The total average output power of 358.44 W is generated when rotary speed of hub of about 600 RPM.

In this article, a novel form of thermal interface material (TIM), represented by three industrially manufactured pressure-sensitive adhesive (PSA) tapes with electrical insulating properties, is characterized regarding its applicability in an electric motor with air-gap winding. Firstly, the adhesion performances, in terms of the winding process, were investigated experimentally. Here, every TIM shows sufficient shear strength for the wire–TIM joints, as well as peel adhesion to the laminated iron core. Secondly, the thermal–physical properties of the TIMs are inspected experimentally via laser flash analysis (LFA) and differential scanning calorimetry (DSC). For every TIM, the value of the thermal resistance can double if the relatively smooth surface (Ra = 0.2 μm) of the adjacent layers is interchanged with a rougher one (Ra = 2.0–3.7 μm). Additionally, the TIM’s performance at the system level is examined. Therefore, a flat test section, according to the specifications of the original motor, is studied experimentally and numerically utilizing infrared (IR) thermography and the finite element method (FEM). The focus is set on the heat flow and temperature distribution in the test section under varying thermal loads, mass flow, and variety of TIMs.

Back-to-back geosynthetic-reinforced soil walls (BBGRSWs) are commonly used in embankments approaching bridges and narrow spaces. However, the available literature and design guidelines for BBGRSWs are limited. The aims of this research were to develop a greater understanding of the working performance of BBGRSWs and to optimize the design method of a BBGRSW to ensure the cost-efficiency as well as the stability of the structure. On the basis of a monitored BBGRSW structure located in China, we established a numerical model. The parameters of the materials used in the actual project were determined through triaxial and tensile tests. The numerical results were compared with the measured results in the field to verify the correctness of the selected parameters. Two parameters were investigated by the FEM method: the reinforcement length and the arrangement. The FEM analysis indicated that post-construction deformations such as displacement and settlement could be reduced by reinforcing the same layer on both sides. Longer reinforcements were needed to achieve the same performance if the reinforcements were cross-arranged. Thus, BBGRSWs can have a superior performance if the reinforcements are connected in the middle from both sides. Even with longer reinforcements, the safety factor of the wall with a cross-arranged reinforcement was smaller than that with same-layered reinforcements.

In the paper a numerical comparative analysis of stresses in a steel die com-pressed by a ring during the extrusion process was presented. In the research, three design solutions of the die were used. The solutions vary depending on the quotient of the wall thickness of the die insert and the wall thick-ness of the compression ring while maintaining a constant tool diameter. The stresses occurring in the areas of the ring and the die were calculated depending on the design version of the tool and the pressure value. The anal-ysis was carried out for the quotients of the die wall thickness to the ring wall thickness of 0.57, 1 and 1.75 and three press-in values of 0.004, 0.008 and 0.016 mm. The conducted research allowed determining the impact of the die design and assembly interference on the load bearing capacity. It was discovered that the use of a die insert with a smaller thickness com-pared to the thickness of the compression ring was the most advantageous from the point of view of the circumferential stresses.

We built a three-dimensional finite element (FE) model to investigate the impact response of fiber-metal laminates (FMLs). This FE model comprises two metal layers as facesheets and a carbon woven fabric-reinforced plastic laminate as inner core. Simulation was performed on ABAQUS/Explicit platform, and stiffness progressive degeneration criteria were implemented to evaluate damages in composites. The Johnson-Cook model was selected to calculate failures in metal, while surface-based cohesive behavior was adopted to simulate the delamination phenomenon. We studied the fiber stacking sequence, panel thickness, and incident angle effect on the impact behavior of FMLs. The critical penetration energy of the FMLs was determined, and the impact parameter history was discussed.

The submitted paper deals with the simulation of thermal cycles during laser welding of aluminum sheets using Finite Element Method (FEM). After the design and creation of the simulation model, the simulation results were verified by the thermal cycles measured during the experiment on real samples. Verification has shown that, despite the differences that have resulted from some simplifications, the proposed model corresponds to the actual behavior of the material used during the laser welding process.

The high-strength steels and tailor welded blanks (TWB) are applied in construction of cars parts to reduction of cars weight [1, 2]. The application of these materials brings possible complicatons during the forming when it proves the considerable influence of stress-strain characteristics differences of of the individual parts of TWB what result in non-constant material flow and consequently a negative movement of the weld interface [3, 4]. One of the ways of elimination of this negative effect is to choose a suitable blankholder system with optimal distribution of blankholder forces by using elastic blankholder with adjustable distribution of blankholder forces. Within the bounds of study the experimental blankholder system with elastic blankholder with adjustable distribution of blankholder forces was used [5, 6]. Finite element methods (FEM) simulation has unsubstitutable role n the study of formability of TWB whereby it is possible to determine the values and points of application of the blankholder forces [7, 8]. The FEM simulations results carried out in simulative LS-Dyna software are presented in this article which is focused on achieving weld interface movement minimalization of tailor welded blanks from DP600 and BH220 materials by optimization of blankholder forces [9, 10].

Starting from synthetic raw materials (CaZrO 3 and MgO), microstructural and mechanical properties were optimised in order to obtain dense multiphasic ceramic, then finite element method (FEM) of an equimolar (1:1) CaZrO 3 -MgO composite was performed in order to obtain the effective elastic modulus. Composite presents two main phases of orthorhombic CaZrO 3 (81.5 wt.%) and cubic MgO (18.5 wt.%); For 1500 °C, relative density of 99.9%, characteristic strength of 168 MPa, hardness of 7.8 MPa and toughness of 2.5 MPa.m1/2 were obtained. FEM simulation was performed using two representative volume elements (RVE's) with edge lengths of 14 μm (933 grains) and 17 μm (1670 grains), using isotropic elastic model, and anisotropic on specific set of crystallographic planes. The results of FEM using isotropic approach for the two RVE's are perfectly aligned with the experimental (245 GPa), while the anisotropic model shows a difference of 6.5%. [ABSTRACT FROM AUTHOR]

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Drawing process represents a significant area of production technology since it influences the feasibility of producing auto-body die panels. In the drawing process, the plastic deformation of blank is not uniform due to the intermittent deformation behavior of the material. This primes a non-uniform thickness distribution in the formed panels, which directly affects the die life and the quality of panels. In the presented study, a new algorithm was proposed for constructing the numerical control machining tool path for the new die surface obtained from FEM simulation and mesh mapping. The commercial package LS-DYNA was employed for the FEM simulation and to calculate the thickness distribution in the drawn workpiece. In order to construct the new numerical control machining tool path according to the new die surface, the positions of all cutter location points relative to the movement of new die mesh were determined. A set of forming die was machined using the proposed algorithm to fabricate a real workpiece of steel DC04. A comparison between the measured thicknesses in the fabricated workpiece and the FEM simulation results shows that they agree with each other very well, which directly validates the proposed algorithm. The developed method can improve product quality, increase production efficiency, and reduce labor intensity. [ABSTRACT FROM AUTHOR]

Many studies have examined the damage behaviour of dual-phase steels already. It is a topic of high interest, since understanding the mechanisms of damage during forming processes enables the production of steels with improved properties and damage tolerance. However, the focus was rarely on the comparison between representatives of this steel class, and the numerical simulation for the quantification of damage states was not thoroughly used. Therefore, this study compares the damage initiation and accumulation of two dual-phase steels (DP800 and DP1000), which are used in the automotive industry. Additionally, parameter sets of a phenomenological damage mechanics model with coupled damage evolution are calibrated for each material. The combined analysis reveals an earlier initiation of damage for the DP800, where the damage accumulation phase is prolonged. For DP1000 the damage nucleates only shortly before material failure. The material model is able to correctly predict the behaviour, while experimental analysis confirms the prediction via light optical and SEM metallography. [ABSTRACT FROM AUTHOR]

This study aims at exploring the multi-pass forging of Torx Round Flange Bolt (automotive fastener) to simulate each pass forging process using FEM simulation. The software is used to carry out the simulation analysis. Constant shear friction is always assumed at the interface between die and workpiece to explore the effective stress, the effective strain, the velocity filed, and the forging force for each pass. Through the pass schedule plan and design based on FEM analysis, the four-pass forging process is designed to form the Torx Round Flange Bolt compared the five-pass forging. It is noted that the total forging force is 1,204 kN, so the 200 tons machinery in the factory can be chosen to manufacture this automotive fastener. The die stress analysis for each pass has been explored to realize whether the dies are damaged or not. The forming feasibility of Torx Round Flange Bolt can be performed by FEM simulation. All dies designs and forming results can be proposed to the dies manufacture so as to perform the realistic experiments. Comparisons between FEM and experiment for final product dimensions can be carried out. The maximum dimension error is just around 3.32% to show a good agreement with the experiment. The research results can provide to the industries as the references of establishment of multi-pass forging technology. [ABSTRACT FROM AUTHOR]

Vertical loads are commonly transferred by piles primarily in the upper structures. However, lateral loads are also significant compared with vertical loads in pile foundation design. Compared with a pile on level ground, there are many particular characteristics in a pile that is on sloping ground. These characteristics depend on the combined loading and the magnitude of the soil lateral displacement. In order to investigate the pile's bearing characteristics, a model test was conducted and ABAQUS software was adopted to conduct 3D numerical simulation of a single pile with different slope angles under combined loads. The experimental results indicated that (1) the soil pressure along the slope direction was smaller than the other side, resulting in an asymmetry of the slope soil around the pile, and in turn introducing a horizontal thrust to the pile; (2) with the increase of slope angle, the horizontal thrust increased while the single pile's bearing capacity decreased; (3) the vertical load caused more pile horizontal displacement with the growth of slope angle; and (4) the pile's moment and the displacement also increased with the growth of the slope angle. The findings in this study can provide a useful reference in the design of piles or anti-slide piles in sloping ground. [ABSTRACT FROM AUTHOR]