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Although the theoretical basis for surface acoustic wave gyroscopes (SAWGs) was first proposed in 1980, their design concepts are still under development. Nevertheless, these sensors are of a great interest in the potential market owing to their exceptional shock resistance, small size, low power consumption, and simple manufacturing process that ensures low cost. This paper aims to conscientiously investigate the ideas that have been proposed over the past decade in this area and evaluate the potential development required to bring SAWGs to market. It should be of interest for researchers in the field who might have missed some useful solutions that could be a missing piece in their own design, or for young researchers to inspire their creativity and open new research on the topic. Additionally, since some of the reviewed SAWG design concepts are based on a combination of several physical principles (for example, optical measurements), researchers from other fields may find useful solutions for incorporating surface acoustic wave techniques into their device concepts. [ABSTRACT FROM AUTHOR]

Finite Element Models (FEM) for simulating various physical phenomena are indispensable in today’s research. They are also applied in high-frequency (HF) surgical applications to simulate Joule heating and thermal necrosis formation in biological tissue. One challenge lies in choosing an appropriate mesh size, balancing between sufficiently accurate simulation results and a coarse mesh for fast computations. In this contribution, we investigate, using three mesh sizes (coarse, medium, and fine), the extent to which regression analysis of discrete simulation results of necrosis dimensions can compensate for mesh refinement in an FEM for HF soft coagulation. We conducted exponential regression analysis on discrete simulation results of the necrosis zone. It has been found that while it is generally possible, if the FEM simulation results already deviate significantly from the true solution, regression analysis cannot compensate for errors arising from the numerical method. Therefore, a coarse mesh with subsequent regression analysis can be utilized to determine necrosis propagation in depth, with a maximum error of only -3.4 % compared to the fine mesh within the considered interval. However, for the necrosis in the lateral direction, the maximum error is 44.3 %, which is too large. Even the mid-size mesh is not accurate enough in the lateral direction, necessitating the use of a fine mesh for the lateral direction.

Laser peen forming (LPF) is an appealing technique for forming metal sheets using high-energy, short-duration laser pulses. The deformation of the target metal plate is closely related to the magnitude and distribution of laser-induced residual stress. Consequently, the relationship between process parameters and residual stress is worth researching. In this research, two process parameters in LPF, laser energy and coverage ratio (spot distance essentially), and one workpiece parameter, plate thickness, were examined through an element method (FEM) of multiple square-spot laser shock peening (SSLSP). Corresponding experiments of SSLSP on aluminum alloy 2024-T351 test blocks were conducted, together with an X-ray diffraction (XRD) residual stress measurement and a surface morphology observation. The FEM simulation and experimental results show that congested laser spots had a significant influence on the magnitude of compressive residual stress; higher laser energy was beneficial to the depth of the compressive stress layer but could decrease its magnitude. Therefore, for better forming ability, higher laser energy and a higher coverage ratio are beneficial; for surface strengthening, laser energy should not be too large, and the coverage ratio should be larger than 100% to ensure that the residual stress on the treated surface is compressive, resulting in better surface integrity.

Interest in the use of container houses has been increasing in recent years because of their resistance to earthquakes and fires. The incorporation of recyclable materials into these houses will simultaneously reduce energy use and greenhouse gas emission rates. In this context, the thermal performance of an external multi-layer wall of a container house mostly made of recyclable materials is studied and compared to that of a normal wall. The current study proposes a completely new structure, where there are air gaps and plastic layers between the steel sheets to enhance thermal insulation. In these gaps, different gases including argon are tested to reduce the heat loss. Calculations are carried out for a steady-state case in the winter season using the student version of ANSYS 2023 R2 Academic software, and the heat loss is calculated for different materials and different thicknesses of the wall layers. Afterward, based on a life-cycle cost analysis, the optimum air gap materials, optimum thickness of plastic and air gap, and energy savings are determined for a period of 20 years. We found that the optimum number of plastic layers to minimize the heating load is 21, but this reduces to 11 when considering economic factors. Furthermore, if a reflective layer covers the plastic layer, the optimum is just one layer. For an insulation thickness of 2 cm, the maximum total life-cycle savings are 335.14 and 350.52 USD, respectively, and the minimum ones are 16.06 and 31.44 USD, respectively, for multi-layer walls with and without reflective layers compared to conventional walls. [ABSTRACT FROM AUTHOR]

Shock wave boundary/layer interactions (SWBLIs) are critical in high-speed aerodynamic flows, particularly within supersonic regimes, where unsteady dynamics can induce structural fatigue and degrade vehicle performance. Conventional measurement techniques, such as pressure-sensitive paint (PSP), face limitations in frequency response, calibration complexity, and intrusive instrumentation. Similarly, MEMS-based sensors, like Kulite® sensors, present challenges in terms of intrusiveness, cost, and integration complexity. This study presents a flexible, lightweight polyvinylidene fluoride (PVDF) piezoelectric sensor array designed for high-resolution wall-pressure measurements in SWBLI research. The primary objective is to optimize low-frequency pressure fluctuation detection, addressing SWBLI's need for accurate, real-time measurements of low-frequency unsteadiness. Fabricated using a double-sided screen-printing technique, this sensor array is low-cost, flexible, and provides stable, high-sensitivity data. Finite Element Method (FEM) simulations indicate that the sensor structure also has potential for high-frequency responses, behaving as a high-pass filter with minimal signal attenuation up to 300 kHz, although the current study's experimental testing is focused on low-frequency calibration and validation. A custom low-frequency sound pressure setup was used to calibrate the PVDF sensor array, ensuring uniform pressure distribution across sensor elements. Wind tunnel tests at Mach 2 verified the PVDF sensor's ability to capture pressure fluctuations and unsteady behaviors consistent with those recorded by Kulite sensors. The findings suggest that PVDF sensors are promising alternatives for capturing low-frequency disturbances and intricate flow structures in advanced aerodynamic research, with high-frequency performance to be further explored in future work. [ABSTRACT FROM AUTHOR]

Recently, deteriorated masonry structures aged over 30 years have shown serious structural problems. Simple and rapid maintenance plans are urgently needed for aging masonry structures. Polyurea (PU) is an effective retrofitting material for aging structures due to its easy spray application. This process saves time, reduces costs, and allows the structure to remain in use during retrofitting. However, a general PU is not suitable for retrofitting aged masonry and concrete structures due to its low stiffness. In this study, stiff-type polyurea (STPU) was selected as the reinforcement material for masonry structures. It was developed by modifying the chemical mix of general PU to improve stiffness. To evaluate the strengthening effect of STPU on masonry members under static loading, tests were conducted. The flexural load capacity of masonry beams with STPU-sprayed surfaces was assessed. Three different types of STPU applications were used to select the most efficient strengthening method. Reinforcing masonry structures with STPU allows brittle failure modes to achieve ductile behavior. This improves their structural performance under lateral stresses. The experimental data were used to calibrate FEM models for simulation. These models can be used for future parametric studies and masonry structural design. [ABSTRACT FROM AUTHOR]

This work presents an optimum methodology for producing friction stir spot welding (FSSW) joints using a detachable consumable pin. The study is carried out by welding two AA6061-T6 sheets using a consumable pin of the same material attached to the H13 steel tool. Three methods for attaching the consumable pin to the tool are explored: (1) push-fitting the pin in an indentation on the tool, (2) adhesively bonding the pin to the tool with a cyanoacrylate adhesive, and (3) adhesively bonding the pin to the tool with a thermosetting glue. After welding, the pin gets detached and assimilated into the workpiece. Cyanoacrylate adhesive–bonded consumable pin was the most effective in producing exit-hole–free FSSW joints with good joint strength. The use of lubricants along with adhesive-bonded consumable pins resulted in a reduction of energy requirement by 35 − 42% without compromising joint strength. Optimization was carried out using data from experiments as well as finite element method simulations. For simulating the lap shear test, the Cockcroft-Latham damage model was used. The optimum process parameters for obtaining the maximum joint strength were a rotational speed of 900 revolutions per minute and a plunge rate of 15 mm/min. Based on the study, a strategy for batch production is also proposed for enhancing productivity. [ABSTRACT FROM AUTHOR]

This study investigates the influence of ferrite shape modifications on the performance and noise characteristics of an induction cooktop. The goal is to optimize the air gap dimensions between ferrites and cookware, enhancing efficiency while managing noise levels. Using finite element method (FEM) simulations, we analyze the spatial distribution of magnetic forces and their harmonics. Eight ferrite shape models were examined, focusing on both outer and inner air gaps. Model #8 (reduced outer air gap) and Model #9 (reduced inner air gap) were experimentally validated. Noise measurements indicated that Model #8 reduced 120 Hz harmonic noise components, while Model #9 increased them due to enhanced excitation forces. Current measurements confirmed that Model #9 achieved higher efficiency, with RMS current reduced to 94.54% of the base model. The study reveals a trade-off between performance and noise: inner air gap reduction significantly boosts efficiency but raises noise levels, whereas outer air gap reduction offers balanced improvements. These findings provide insights for optimizing induction cooktop designs, aiming for quieter operation without compromising efficiency. [ABSTRACT FROM AUTHOR]

Shot peening is a commonly used method of finishing machine elements in the manufacturing process. One variation of shot peening is the impulse shot peening. This paper presents the influence of impulse shot peening technological conditions on the surface roughness (parameters Ra and Rt), topography, and microhardness. The FEM was used to determine the S11 stresses. In the experiment and simulation tests, AZ31 and AZ91HP magnesium alloy samples were used. Variable parameters in the impulse shot peening process were impact energy E (15–185 mJ), ball diameter d (3–15 mm), and impact density j (3–44 mm−2). As a result of the tests carried out, it was found that after impulse shot peening, the surface topography is change, microirregularities are flattened, and numerous depressions are formed, which can be potential lubrication pockets. The 2D surface roughness parameters for most impulse shot peening conditions are lower than for the pre-machining. The roughness parameters for magnesium alloy AZ91HP are lower than for AZ31. This is most likely due to the lower elongation A. The microhardness after impulse shot peening increased by 20 to 87 HV. As a result of FEM of the impulse shot peening, compressive stresses S11 were created in the surface layer. The depth of occurrence of S11 stresses is from 1.5 to 3.5 mm, and their values for the AZ91HP magnesium alloy samples are 10 to 25% lower than for the AZ31 alloy samples. The most favorable results of the tested properties of the surface layer were obtained for E = 100 mJ, d = 10 mm, and j = 11 mm−2. The abstract serves both as a general introduction to the topic and as a brief, non-technical summary of the main results and their implications. [ABSTRACT FROM AUTHOR]

Hematite (α -Fe2O3) is widely used in sensor sensitization due to its excellent optical properties. In this study, we present a sensitivity-enhanced surface plasmon resonance alcohol sensor based on Fe2O3/Au. We describe the fabrication process of the sensor and characterize its structure. We conduct performance testing on sensors coated multiple times and use solutions with the same gradient of refractive indices as the sensing medium. Within the refractive index range of 1.3335–1.3635, the sensor that was coated twice achieved the highest sensitivity, reaching 2933.2 nm/RIU. This represents a 30.26% enhancement in sensitivity compared to a sensor with a pure gold monolayer film structure. Additionally, we demonstrated the application of this sensor in alcohol concentration detection by testing the alcohol content of common beverages, showing excellent agreement with theoretical values and highlighting the sensor's potential in food testing. [ABSTRACT FROM AUTHOR]

A multiscale model is developed for vertically aligned carbon nanotube (CNT)-based membranes that are made for water purification or gas separation. As a consequence of driving fluids through the membranes, they carry stress waves along the fiber direction. Hence, a continuum mixture theory is established for a representative volume element to characterize guided waves propagating in a periodically CNT-reinforced matrix material. The obtained coupled governing equations for the CNT-based composite are found to retain the integrity of the wave propagation phenomenon in each constituent, while allowing them to coexist under analytically derived multiscale interaction parameters. The influence of the mesoscale characteristics on the continuum behavior of the composite is demonstrated by dispersion curves of harmonic wave propagation. Analytically established continuum mixture theory for the CNT-based composite is strengthened by numerical simulations conducted in COMSOL for visualizing mode shapes and wave propagation patterns. [ABSTRACT FROM AUTHOR]

Numerical solutions in the field of modelling of the welding process constitute significant support for the production process and are one of the most difficult to perform in terms of the complexity of physical phenomena in the welding process. This is especially true when commercial software such as Abaqus, Ansys, etc. is used in the analysis, where welding conditions are not directly reflected in the modules of the software. This work is focused on the development of mathematical models of a moveable heating source taking into account various welding techniques. The simulations are carried out in Abaqus software, which, in its basic form, does not allow simulations of welding process. The presented work contains the developed mathematical and numerical models necessary for conducting numerical studies in the field of the analysis of the welding process. The presented DFLUX subroutine allows the implementation of any mathematical model of the heating source and modelling of the movement of the source along any trajectory. As a part of the research, mathematical models are developed for three completely different welding techniques: fillet welding, circumferential welding and spiral welding. Each of these three methods requires the use of a completely different approach. Based on the developed mathematical and numerical models, testing calculations are performed. Selected calculations are compared with experimental results presented in the literature. The presented results of calculations allow for the confirmation of the correctness of the developed mathematical and numerical models of heat source power distribution. [ABSTRACT FROM AUTHOR]

On the DIFA II loom, which is a special air jet weaving machine for the production of drop-stitch fabrics with a variable distance, so called 3D or distance fabrics, the main component of the interconnecting yarn creation mechanism is a take-up bar. During the yarn loops formation, the take-up bar is exposed to high loads, while being pulled by a mechanism into a limited wedge-shaped space between the two plain weave faces, thus the bending stiffness of the bar is crucial. Deflection of the bar combined with an elongation of the warp yarns results in an uneven load distribution with an undesirably loosened central section of warp yarns. This phenomenon is deeply examined in this paper. The classical model of a thin beam loaded by a distributed linear force cannot be applied in this case. In this work are new take-up bar designs considering usage and production aspects. The take-up bar variants with different warp yarns stiffness were analysed. A numerical model was created, and calculations were performed by the FEM solver NX Nastran as a 1D solution. Additionally, the problem was analysed analytically and it shows an analogy with a beam on an elastic foundation. The theoretical Winkler's model was used and an idealised analytical solution was found. In both methods, comparable maximal deflections of the take-up bar and widths of loosened yarns were found. The obtained results of the bar deflection were validated with a good agreement on the DIFA II loom using new take-up bars. [ABSTRACT FROM AUTHOR]

Precision machining operations often lead to the failure of protective coatings on cutting tools due to common issues such as cracking, delamination, and peeling from cyclic impacts. While material selection and structural design are crucial for enhancing impact resistance, they primarily focus on static performance with limited consideration from the dynamic sights. This paper presents a novel dynamic design method for coatings, viewed through the lens of stress waves. We investigate the propagation behavior of stress waves in TaN/TiN and CrN/TiN coatings with layered structures. Our findings indicate that the attenuation of stress waves is dominated by the physical properties on both sides of the interface and the stride length. For interfaces with similar physical properties, the attenuation of stress waves is insensitive to the stride length, while for interfaces with different physical properties, the attenuation is regulated by the ratio of single-layer thickness to the full width at half maximum of the stress wave. These insights offer a strategy for extending the life of coatings and improving process safety under dynamic shocks.

This paper presents a comprehensive approach aimed at developing a coupled process-structure simulation that integrates anisotropic and elastoplastic material behavior for plastic components manufactured through Fused Filament Fabrication (FFF) 3D printing. The simulation incorporates material orientation considerations, linking the process simulation with structural simulation. Subsequently, stress and strain values from the simulations are compared with the test results. Moreover, the fracture behavior of components manufactured in this way is also taken into account in relation to material orientation. The executed simulations have yielded successful outcomes, affirming the efficacy of the anisotropic and elastoplastic simulation across all strand orientations. Special attention is paid to the application of the method. Here, the simulation method introduced in this contribution with the approaches for describing the material behavior under mechanical load can be used in the future in the dimensioning of FFF manufactured plastic components to predict the deformation behavior and failure, especially under consideration of a well economic and efficient virtual product development. [ABSTRACT FROM AUTHOR]

In this study, an effective numerical model was developed for the calculation of the deformation of laser-welded 3 mm 304L stainless steel plates with different gaps (0.2 mm, 0.5 mm, and 1.0 mm). The welding deformation would become larger when the welding gaps increased, and the largest deformation values along the Z direction, of 4 mm, were produced when the gap value was 1.0 mm. A larger plastic strain region was generated in the location near the weld seam, since higher plastic deformation had occurred. In addition, the tensile stress model was also applied at the plastic strain zone and demonstrated that a larger welding gap led to a wider residual stress area. Based on the above results, inherent deformations for butt and corner joints were calculated according to inherent strain theory, and the welding formation for the complex structure was calculated with different gaps. The numerical results demonstrated that a larger deformation was also produced with a larger welding gap and that it could reach the highest value of 10.1 mm. This proves that a smaller welding gap should be adopted during the laser welding of complex structures to avoid excessive welding deformation. [ABSTRACT FROM AUTHOR]

Within the scope of this study, the macroscopic temperature distribution in the steady-state temperature condition during Field Assisted Sintering Technique/Spark Plasma Sintering (FAST/SPS) in functionally graded materials (FGM) was investigated. The sample material exhibited a diameter of 50 mm and a thickness of 9 mm. The FGM samples were composed of steel X2CrMnNi 16-7-6 and Mg-PSZ ceramic (MgO partly stabilized ZrO 2). By varying the sintering tool setup, a specific modification of the macroscopic temperature distribution within the sample material and the sintering tool was achieved. The aim of the modifications was to optimize the temperature gradients in order to allow for the simultaneous compaction of all FGM layers under ideal circumstances. This involves achieving enhanced ceramic densification without inducing steel melting. Finite element method (FEM) simulations were carried out to get information about the temperature distribution within the sample material and the sintering tool. Furthermore, for this propose, thermocouple temperature measurements were conducted at various measurement points on pre-sintered FGM within the specific sintering tool setup. Additionally, all findings regarding the temperature distribution within the sample material and the sintering tool were compared with results concerning the temperature distribution from the microstructural and mechanical characterization of the center and edge regions of the FGM samples. The FGM samples exhibited a significant increase in temperature from the center to the edge in the radial direction depending on the used sintering tool setup. While the FGM samples showed only minor vertical temperature gradients in the center, the highest vertical temperature gradients were determined at the edge of the FGM sample using an asymmetric sintering tool setup. [ABSTRACT FROM AUTHOR]

An investigation into the evolution of temperature and stress fields, as well as the phase transformation in marine steel EH36 during multi-pass welding, and their subsequent effects on Charpy impact toughness, remains in great lack. In this study, submerged arc welding (SAW) was employed to carry out multi-pass welding on EH36 steel plates, followed by the low-temperature toughness test of weldments. Comsol software version 6.2 and finite element analysis are utilized to simulate the evolution of the microstructure, temperature, and residual stress fields throughout the multi-pass welding process. As welding progressed, the heat absorption along the vertical direction was enhanced; in contrast, a decrease is observed in the horizontal direction away from the heat source. This complicated temperature history favors the bainite transformation in the vicinity to the heat source, whereas areas more remote from the weld zone exhibit a higher prevalence of acicular ferrite due to the reduced cooling rate. The concentration of residual stress is predicted to occur at the boundary of the melt pool and at the interface between the weld and the heat-affected zone, with the greatest deformation observed near the fusion line at the top surface of the model. Furthermore, multi-pass welding may alleviate the residual stress, especially when coupled with the formation of acicular ferrite upon cooling, leading to improved low-temperature impact toughness in regions remote from the heat source. These findings offer valuable insights for the design and optimization of multi-pass welding in future applications. [ABSTRACT FROM AUTHOR]

Machinery traffic is associated with the application of stress onto the soil surface and is the main reason for agricultural soil compaction. Currently, probes are used for studying the stress propagation in soil and measuring soil stress. However, because of the physical presence of a probe, the measured stress may differ from the actual stress, i.e. the stress induced in the soil under machinery traffic in the absence of a probe. Hence, we need to model the soil-stress probe interaction to study the difference in stress caused by the probe under varying loading geometries, loading time, depth, and soil properties to find correction factors for probe-measured stress. This study aims to simulate the soil-stress probe interaction under a moving rigid wheel using finite element method (FEM) to investigate the agreement between the simulated with-probe stress and the experimental measurements and to compare the resulting ratio of with/without probe stress with previous studies. The soil was modeled as an elastic-perfectly plastic material whose properties were calibrated with the simulation of cone penetration and wheel sinkage into the soil. The results showed an average 28% overestimation of FEM-simulated probe stress as compared to the experimental stress measured under the wheel loadings of 600 and 1,200 N. The average simulated ratio of with/without probe stress was found to be 1.22 for the two tests which is significantly smaller than that of plate sinkage loading (1.9). The simulation of wheel speed on soil stress showed a minor increase in stress. The stress over-estimation ratio (i.e. the ratio of with/without probe stress) noticeably increased with depth but increased slightly with speed for depths below 0.2 m.

The brake system must be reliable and display unchanging action throughout its use, as it guards the health and life of many people. Properly matched friction pair, a drum, and a brake pad have a great impact on these factors. The brake pads are far more complex components. New technologies make it possible to develop materials with various compositions and different proportions and connect them permanently in fully controllable processes. This elaboration shows that all these factors have a greater or lesser impact on the coefficient of friction, resistance to friction wear and high temperature, and the brake pad’s operating life. The friction materials are required to provide a stable coefficient of friction and a low wear rate at various operating speeds, pressures, temperatures, and environmental conditions. The aim of this work is therefore to investigate the possibility of using a Finite Element Analysis (FEA) approach to evaluate the braking performance of a heavy-duty elevator with different non-conventional pad materials including Composite Carbon fiber reinforced, Composite Epoxy SMC and SiC (silicon carbide). The results show that the performance of SiC (silicon carbide) is better than two other materials. In the braking system with SiC, the required time for stoppage of the system is lower than two other materials.

In the present work, the mechanical response of strain aging sensitive ductile cast iron was studied when subjected to uniaxial tension in temperatures ranging from 20°C up to 300°C. Digital Image Correlation (DIC) was used to measure the strain localization patterns due to dynamic strain aging. A constitutive law based on the Kubin–Estrin–McCormick model (KEMC) was used to model the behavior of the ductile cast iron in temperatures ranging from 20° up to 300°. The displacement fields were successfully measured and the strain localization patterns were observed. These measurements were employed to calibrate the parameters of the constitutive law. Numerical simulations are shown to be in agreement with experimental measurements at the macroscopic scale.

The present paper proposes a new approach for the thermomechanical analysis of small satellites. In the first stage, the heat fluxes acting on the exterior surfaces of the assembly are evaluated with the support of the CubeSat Wizard. The orbital parameters employed ensure adequate radiation heat transfer. Afterwards, the temperature distribution of the entire structure is evaluated with the support of the LISA thermal transient environment. The most critical load case is further use for calculating stress and displacement in a static analysis. Two configurations of CardSat nanosatellites are included in the study for comparison.

Interest in the use of container houses has been increasing in recent years because of their resistance to earthquakes and fires. The incorporation of recyclable materials into these houses will simultaneously reduce energy use and greenhouse gas emission rates. In this context, the thermal performance of an external multi-layer wall of a container house mostly made of recyclable materials is studied and compared to that of a normal wall. The current study proposes a completely new structure, where there are air gaps and plastic layers between the steel sheets to enhance thermal insulation. In these gaps, different gases including argon are tested to reduce the heat loss. Calculations are carried out for a steady-state case in the winter season using the student version of ANSYS 2023 R2 Academic software, and the heat loss is calculated for different materials and different thicknesses of the wall layers. Afterward, based on a life-cycle cost analysis, the optimum air gap materials, optimum thickness of plastic and air gap, and energy savings are determined for a period of 20 years. We found that the optimum number of plastic layers to minimize the heating load is 21, but this reduces to 11 when considering economic factors. Furthermore, if a reflective layer covers the plastic layer, the optimum is just one layer. For an insulation thickness of 2 cm, the maximum total life-cycle savings are 335.14 and 350.52 USD, respectively, and the minimum ones are 16.06 and 31.44 USD, respectively, for multi-layer walls with and without reflective layers compared to conventional walls.

Shock wave boundary/layer interactions (SWBLIs) are critical in high-speed aerodynamic flows, particularly within supersonic regimes, where unsteady dynamics can induce structural fatigue and degrade vehicle performance. Conventional measurement techniques, such as pressure-sensitive paint (PSP), face limitations in frequency response, calibration complexity, and intrusive instrumentation. Similarly, MEMS-based sensors, like Kulite® sensors, present challenges in terms of intrusiveness, cost, and integration complexity. This study presents a flexible, lightweight polyvinylidene fluoride (PVDF) piezoelectric sensor array designed for high-resolution wall-pressure measurements in SWBLI research. The primary objective is to optimize low-frequency pressure fluctuation detection, addressing SWBLI’s need for accurate, real-time measurements of low-frequency unsteadiness. Fabricated using a double-sided screen-printing technique, this sensor array is low-cost, flexible, and provides stable, high-sensitivity data. Finite Element Method (FEM) simulations indicate that the sensor structure also has potential for high-frequency responses, behaving as a high-pass filter with minimal signal attenuation up to 300 kHz, although the current study’s experimental testing is focused on low-frequency calibration and validation. A custom low-frequency sound pressure setup was used to calibrate the PVDF sensor array, ensuring uniform pressure distribution across sensor elements. Wind tunnel tests at Mach 2 verified the PVDF sensor’s ability to capture pressure fluctuations and unsteady behaviors consistent with those recorded by Kulite sensors. The findings suggest that PVDF sensors are promising alternatives for capturing low-frequency disturbances and intricate flow structures in advanced aerodynamic research, with high-frequency performance to be further explored in future work.

Thermal interface materials (TIMs), as important materials for heat dissipation of insulated gate bipolar transistor (IGBT) modules, degrade under long-term thermal cycling, resulting in elevated junction temperatures and threatening the safe operation of IGBT modules. In consideration of the thermal coupling effect in IGBT modules, this paper proposes a three-dimensional thermal network model characterizing the TIM degradation. An IGBT module with the TIM is adopted to establish the finite element method (FEM) model, in which the TIM layer is divided into regular areas. The thermal network is established by simulating the heat transfer paths. The thermal impedance in each path is extracted according to the heat flow through its area considering the TIM degradation. Thereby, the impact of thermal coupling and TIM degradation on junction temperature of IGBT modules could be characterized. Furthermore, the proposed thermal network is verified by simulation from calculation accuracy of junction temperature and TIM temperature.

The early detection of small cracks in large metal structures is a crucial requirement for the implementation of a structural health monitoring (SHM) system with a low transducers density. This work tackles the challenging problem of the early detection of submillimeter notch-type defects with a semielliptical shape and a groove at a constant width of 100 µm and 3 mm depth in a 4.1 mm thick aluminum plate. This defect is investigated with an ultrasonic guided wave (UGW) A0 mode at 550 kHz to investigate the long range in thick metal plates. The mode selection is obtained by interdigital transducers (IDTs) designed to operate with a 5 mm central wavelength. The novel contribution is the validation of the detection by pulse-echo and pitch and catch with UGW transducers to cover a distance up to 70 cm to reduce the transducers density. The analysis of scattering from this submillimeter defect at different orientations is carried out using simulations with a Finite Element Model (FEM). The detection of the defect is obtained by comparing the scattered signals from the defect with baseline signals of the pristine laminate. Finally, the paper shows that the simulated results are in good agreement with the experimental ones, demonstrating the possible implementation in an SHM system based on the efficient propagation of an antisymmetric mode by IDTs. [ABSTRACT FROM AUTHOR]

This paper presents static modelling and simulation of a spherically-shaped hyperelastic balloon actuator subjected to an angular rotation with an internally applied air pressure. These actuators are extensively used in soft robotics because its safe and flexible nature. The balloon actuator is a pneumatic-type actuator made of a polymeric material. A continuum mechanics-based analytical modelling and Finite element method-based simulation are performed to predict the response of the actuator for a given angular rotation with internally applied air pressure. The proposed modelling framework is subsequently utilised to perform the parametric studies for varying pressure, thickness, and rotational speed of the actuator. Various elastic instability curves are also obtained to examine the critical inflation of the rubber balloon actuator. The analytical findings agree well with the FEM simulations. [ABSTRACT FROM AUTHOR]

A Bayesian machine learning (ML) framework was introduced for the comprehensive characterization of bond wires within insulated gate bipolar transistor (IGBT) modules under the influence of thermomechanical loadings. The primary objective of this work was to predict two critical performance metrics, namely, equivalent plastic deformation (EPD) and the number of cycles to failure (Nf). At the core of our investigation was the dependable acquisition of training data via finite element method simulations. Based on the results, exceptional predictive accuracy was achieved, as evidenced by the impressive R-squared values of 0.962 for EPD and 0.927 for Nf, both of which are obtained from the Bayesian ML model. The high performance of the Bayesian model can be attributed to its ability to effectively capture complex relationships within the data while simultaneously being robust in handling uncertainties, rendering it suitable for situations characterized by limited datasets. Furthermore, it was revealed that the weight functions of the input parameters were significantly influenced by the values of the output targets, illustrating the distinct dependencies between each output target (EPD and Nf) and the relevant input features. These findings contribute to a deeper comprehension of the intricate interactions between input parameters and output metrics, ultimately aiding in the development of more precise and dependable models for bond wire characterization in IGBT modules. [ABSTRACT FROM AUTHOR]

Machinery traffic is associated with the application of stress onto the soil surface and is the main reason for agricultural soil compaction. Currently, probes are used for studying the stress propagation in soil and measuring soil stress. However, because of the physical presence of a probe, the measured stress may differ from the actual stress, i.e. the stress induced in the soil under machinery traffic in the absence of a probe. Hence, we need to model the soil-stress probe interaction to study the difference in stress caused by the probe under varying loading geometries, loading time, depth, and soil properties to find correction factors for probe-measured stress. This study aims to simulate the soil-stress probe interaction under a moving rigid wheel using finite element method (FEM) to investigate the agreement between the simulated with-probe stress and the experimental measurements and to compare the resulting ratio of with/without probe stress with previous studies. The soil was modeled as an elastic-perfectly plastic material whose properties were calibrated with the simulation of cone penetration and wheel sinkage into the soil. The results showed an average 28% overestimation of FEM-simulated probe stress as compared to the experimental stress measured under the wheel loadings of 600 and 1,200 N. The average simulated ratio of with/without probe stress was found to be 1.22 for the two tests which is significantly smaller than that of plate sinkage loading (1.9). The simulation of wheel speed on soil stress showed a minor increase in stress. The stress over-estimation ratio (i.e. the ratio of with/without probe stress) noticeably increased with depth but increased slightly with speed for depths below 0.2 m. [ABSTRACT FROM AUTHOR]

Biofilms are ubiquitous at interfaces of natural and technical origin. Depending on type and application, biofilm formation is desired or has to be prevented. Therefore, reliable detection of initial biofilm growth is essential in many areas. One method of biofilm monitoring is the electrochemical impedance spectroscopy. Among other factors, this method is heavily dependent on the electrode geometry. In order to achieve a high measurement sensitivity, the electrode size must be chosen according to the biofilm that is to be measured. This paper presents an approach for simulating and modeling the optimal electrode geometry for a specific biofilm. First, a geometric model of a biofilm with up to 6000 individual bacteria is generated. The simulated impedances are used to calculate which electrode geometry maximizes sensitivity depending on the biofilm height. In the chosen example of an E. coli biofilm in a nutrient solution, the optimum size of an interdigital electrode (bar gap equals width) was 2.5 µm for a biofilm height of up to 2 µm. The used algorithms and models can be simply adapted for other biofilms. In this way, the most sensitive electrode geometry for a specific biofilm measurement can be determined with minimal effort. [ABSTRACT FROM AUTHOR]

This paper investigates the behavior of transverse defects under significant total strain in conditions of complex vortex metal flow implemented through the radial shear rolling (RSR) method. The aim of this study is to assess the applicability of RSR processing for the in-depth transformation of small ingots of special steel into bars, particularly for the manufacturing of structural elements in specialized construction projects such as nuclear power plants. Although a substantial total strain is anticipated to enhance the steel structure and contribute to defect closure, the question of the development or closure of potential casting defects remains unclear. To address this issue, model tests were conducted to simulate the implementation of RSR processing. Defect behavior data under very complex vortex metal flow and high strain conditions were obtained for the first time and have scientific merit. A small steel ingot with a 32 mm diameter, containing a simulated artificial defect in the form of a transverse through-hole with a 5 mm diameter, was employed. During rolling, the workpiece diameter was progressively reduced by 2 mm with each subsequent pass, reaching a final diameter of 20 mm. Additionally, to provide a more detailed visualization of the defect evolution process, the same defect was modeled in an aluminum bar over six passes, and changes in defect volume and shape were analyzed after each pass. A highly detailed 3D visualization of the actual defect evolution was achieved based on cross-sections from experimental workpieces. These data corresponded to the total strain levels obtained by finite element method (FEM) simulation. Notably, a consistent similarity was observed between the test results for both metals, revealing a reduction in defect volume of up to 67.7%. The deformational welding of defects in the outer sections, encompassing one-third of the rod's radius, occurred in the initial passes. However, defects in the axial zone of the rods remained unclosed, lengthening and gradually decreasing proportionally to the elongation of the rod, akin to conventional rolling. Consequently, the radial shear rolling (RSR) method is unsuitable for ingots with substantial discontinuities in the axial zone post-casting. Nevertheless, the method ensures the total welding of defects located in the outer zones of the ingots, even with minor applied deformations and a slight decrease in the diameter of the deformed ingot. Such data were obtained for the first time and should contribute to future investigations in this field. [ABSTRACT FROM AUTHOR]

Efficient density evolution during sintering of the as-printed component is vital to reach full densification and required properties of binder jet (BJT) components. However, due to the high porosity and brittle nature of the green compact, analysis of the microstructure development during sintering is very difficult, resulting in lack of understanding of the densification process. Density development from green state (57 ± 1.6 %) up to full density (99 ± 0.3 %) was characterized by high-resolution synchrotron X-Ray computed tomography (SXCT) on BJT 316L samples from ex-situ interrupted sintering tests. Periodicity of density fluctuations along the building direction was revealed for the first time and was related to the layer thickness of ∼ 42 µm during printing that decreased down to ∼ 33 µm during sintering. Sintering simulations, utilizing a continuum sintering model developed for BJT, allowed to replicate the density evolution during sintering with a mean error of 2 % and its fluctuation evolution from green (1.66 %) to sintered (0.56 %) state. Additionally, simulation of extreme particle size segregation (1 µm to 130 µm) suggested that non-optimized printing could lead to undesirable density fluctuation amplitude rapid increase (∼10 %) during sintering. This might trigger the nucleation of defects (e.g., layer delamination, cracking, or excessive residual porosity) during the sintering process.

This work aims to characterize 3D-printed structures composed of a thermoplastic material (polylactic acid (PLA)) containing a combination of magnetic particles composed of iron(III) oxide (hematite) and iron(II)–iron (III) oxide (magnetite) with various infill densities and print orientations in regard to their possible processing by Fused Filament Fabrication additive technology. The correct processing temperatures have been determined using thermal analysis, and the paramagnetic and mechanical properties of the samples have been tested. The relative permeability has been identified to be strongly dependent on the topology parameters of the tested samples. The results of the inductance values for the samples without magnetic additives (infill densities 50% and 100%) have been detected to be comparable; nonetheless, the magnetic samples with 100% infill density has been found to be about 50% higher. A similar trend has been observed in the case of the values of the relative permeability, where the magnetic samples with 100% infill density have been measured as having an about 40% increased relative permeability in the comparison with the samples without magnetic additives (infill densities 20–100%). Finite Element Modelling (FEM) simulations have been applied to determine the magnetic field distributions and, moreover, to calculate the holding forces of all the printed samples. The maximum value of the holding force for the minimum distance of the plastic plate has been found to reach a value of almost 300 N (magnetic sample with 100% infill density). The obtained comprehensive characterization of the printed samples may be utilized for designing and tuning the desired properties of the samples needed in various industrial applications. [ABSTRACT FROM AUTHOR]

The brake system must be reliable and display unchanging action throughout its use, as it guards the health and life of many people. Properly matched friction pair, a drum, and a brake pad have a great impact on these factors. The brake pads are far more complex components. New technologies make it possible to develop materials with various compositions and different proportions and connect them permanently in fully controllable processes. This elaboration shows that all these factors have a greater or lesser impact on the coefficient of friction, resistance to friction wear and high temperature, and the brake pad's operating life. The friction materials are required to provide a stable coefficient of friction and a low wear rate at various operating speeds, pressures, temperatures, and environmental conditions. The aim of this work is therefore to investigate the possibility of using a Finite Element Analysis (FEA) approach to evaluate the braking performance of a heavy-duty elevator with different nonconventional pad materials including Composite Carbon fiber reinforced, Composite Epoxy SMC and SiC (silicon carbide). The results show that the performance of SiC (silicon carbide) is better than two other materials. In the braking system with SiC, the required time for stoppage of the system is lower than two other materials. [ABSTRACT FROM AUTHOR]

Homogenization methods can characterize the mechanical properties of these materials based on appropriate constitutive models and data. They are also applied to the characterization of mechanical parameters under complex geotechnical conditions in geotechnical engineering because of the complexity and heterogeneous nature of geotechnical materials. Unfortunately, existing homogenization methods for geotechnical mechanical parameters often incur immense computational costs. Hence, a framework that utilizes finite element analysis for generating a dataset which is then trained using a Bayesian Optimized Back Propagation Artificial Neural Network (BP-ANN) to obtain the homogenized Mohr–Coulomb parameters of the soils is proposed. This is the first time that Bayesian optimization and a BP-ANN have been used in conjunction to predict the homogenized mechanical parameters of soils. The dataset used for training the data is generated using the commercial FEM software ABAQUS (6.10). The maximum difference between the top and bottom part of the tunnel of the heterogeneous model and homogeneous model of our test cases only varies by 5.3%, thereby verifying the excellence of the Bayesian Optimized BP-ANN. [ABSTRACT FROM AUTHOR]

Laser powder bed fusion (L-PBF) is widely used in automotive, aerospace, and biomedical applications thanks to its ability to produce complex geometries. In spite of its advantages, parts produced with this technology can show distortion due to the residual stresses developed during the printing process. For this reason, numerical simulations can be used to predict thermal gradients and residual stresses that can result in part distortion. Thus, instead of performing experimental tests and using a trial and error approach, it is possible to use numerical simulation to save time and material. In this work, the effect of laser power and scan speed on residual stress and part distortion was analysed using a commercial finite element analysis (FEA) software DEFORM-3D™ with a layer-by-layer approach. Moreover, the accuracy of the numerical model with respect to process parameters and the utilised mesh was also studied. The results obtained from the numerical simulation were compared to the actual distortions to evaluate the accuracy of the FEM model. The predicted distortions using FEM analysis well fit the trend of the measured ones. The accuracy of the numerical model increases by considering a finer mesh. [ABSTRACT FROM AUTHOR]

Quasi-beta processing was considered to be a promising processing method to obtain a component with excellent mechanical properties. To achieve an optimized quasi-beta processing parameter for TC21 alloys, the hot deformation behavior in the near β phase region for the alloy with a forged structure was investigated by the thermal compression test and finite element (FEM) simulation. The obtained results indicated that the flow behavior of the samples was significantly influenced by the hot deformation parameters, and it exhibited a flow hardening behavior at the start stage of deformation. Based on the experimental data, the constitutive equation and processing maps were obtained. The optimum hot processing parameter was 986 °C/10−3 s−1. Based on the FEM simulation results, the evolution of the temperature field, strain field, and stress field in the deformed samples at different strains exhibited a similar trend in the unstable region, which was distributed symmetrically along the center line of the samples, with the center area of the samples being the highest and the center area of the section being the lowest. [ABSTRACT FROM AUTHOR]

In this work a new design concept in the field of microwave heating assisted chemical reactors is proposed focusing on two main innovations. The first one consists in combining the resonant cavity and the vessel in the same volume, improving the durability of the system by using a metallic material for the vessel. The second consists of integrating antennas as applicator ports for energy transmission from the magnetron into the cavity, instead of waveguides, allowing greater design flexibility in terms of cavity and system dimensions. In this work, a microwave reactor with four electromagnetic energy emitting antennas is optimized. This innovation is evaluated by means of a simulation model that solves the finite element method (FEM) using the commercial software COMSOL Multiphysics coupling radio frequency and heat transfer physics. Within this work, simulations have demonstrated the microwave heating process in the configured chemical reactor where the implementation of standard waveguides would not be possible due to the incompatible size required in the selected diameter dimension for 106 litres. Therefore, the results achieved lay the foundation for the construction of a microwave reactor intended to drive the industrial process of chemical recycling of polymers on a large industrial scale.

To explore the effect of pore precipitation freezing in different saturated states on mechanical performance for drainage asphalt pavement, the study revealed the freezing behavior characteristics of pore precipitation in different saturated states by combining CT scanning, FEM simulation and mechanical tests. Firstly, the real spatial structure of drainage asphalt mixture was obtained through the CT scanning, and the corresponding FEM simulation model was established. Secondly, the process of pore precipitation freezing in different saturated states was simulated and analyzed, and its influence on the spatial structure of drainage asphalt mixture was obtained. Finally, the effect of pore precipitation freezing in different saturated states on drainage asphalt mixture was proved through mechanical tests. It is found that the effect of pore precipitation freezing on mechanical performance of drainage asphalt mixture is different under different saturated states. With the increase of saturation state, the influence of pore precipitation freezing becomes more obvious, and the difference of stress-strain distribution in spatial structure for drainage asphalt mixture is more prominent. The study explains how pore precipitation freezing in different saturated states affects the mechanical performance for drainage asphalt pavement, providing a theoretical basis for enhancing its durability.

Power cables are one of the key components of fast-growing HVDC transmission systems. The long-term reliability of HVDC cables is closely related to the occurrence of partial discharges (PDs) in their insulation systems. The article analyzes the conditions for the formation of PD pulses in gaseous voids located in the XLPE insulation of an HVDC cable. For this purpose, the MATLAB® procedure and the coupled electro-thermal simulation model implemented in COMSOL Multiphysics® software were used. The FEM model was used to study the effect of the applied voltage, the temperature field (created in the insulation of the loaded cable) and the location of the gaseous void (on cable radius) in the distribution and values of the electric field in the cable insulation. The model takes into account the influence of temperature and the electric field on the conductivity of the insulating material and relates the value of the PD inception field to the temperature/pressure of the gas inside the void. In the numerical simulation procedure, the time sequences of PDs arising in the gaseous defects of the HVDC cable insulation were analyzed, by observing changes caused by the increase in the temperature of the cable core. The model was used for a study of conditions for PD formation in models of three HVDC cables, for DC voltages from 150 kV to 500 kV. The critical dimensions of gaseous voids were also estimated for each of the analyzed cables, i.e., the dimension which, if exceeded, makes a void a source of PD. [ABSTRACT FROM AUTHOR]

This theoretical study analyzes the possibility to use the classical Mott's hypothesis to model the natural fragmentation of cylindrical structures with two or more metal cylinders arranged coaxially. A critical analysis on the validity of the used hypothesis was conducted based on empirical relations and numerical simulations. The established algorithm allows the determination of a fragment mass scale parameter for each individual cylinder, which is why the cumulative distribution of fragments for the entire structure may be calculated. The results obtained for the structures with two and three cylinders, with equal masses or equal wall thicknesses, can be approximated using a modified Mott's distribution formula in which the number of cylinders is used as an additional parameter. [ABSTRACT FROM AUTHOR]

The article analyzes the microstructure evolution of Co-Cr-Mo alloy during isothermal forging. The process of isothermal forging can be a technological solution to produce a semi-finished product for subsequent deformation processing and obtain a high-quality microstructure that excludes casting defects. Based on analysis of microstructure and phase composition and calculations, the required modes of ingot homogenization are determined. Finite element method simulation of the forging has shown that temperature and deformation conditions make deformation in the single-phase γ-region possible. However, at lower temperatures, σ-phase particles may precipitate at the last steps of deformation. After isothermal forging and water quenching, a mixture of recrystallized and polygonized structures with an average grain size of 5–10 μm and precipitation of ultra-fine dispersed particles of σ-phase (~0.13 μm) at grain boundaries are formed. Isothermal forging in the temperature range of 1100–1200 °C and at low strain rates of up to 1 s−1 allows obtaining a microstructure without pores, cracks, and large inclusions. Thus, it makes it possible to use the forging billet for further deformation by different metal forming methods. [ABSTRACT FROM AUTHOR]

• This paper presents a drained expansion solution of a cylindrical cavity with fabric change effect in the sand. • The problem is formulated as a system of first-order differential equations with the known variables. • A user-defined SANISAND model is implemented as a subroutine, which is applied to FEM simulation. Sandy soil exhibits inherently anisotropy due to its microstructure, also known as 'fabric'. However, the drastic change in fabric observed during the dilatant phase is often overlooked in current cavity expansion research. This paper presents a drained expansion solution of a cylindrical cavity with fabric change effect in the sand using a simple non-associated and anisotropic model, SANISAND. The problem is formulated as a set of first-order differential equations with the unknown variables as functions of an auxiliary coordinate, which can be solved as an initial value problem. A subroutine is implemented into the FEM simulation to verify the proposed method. Additionally, cavity expansion solutions in sand are compared with those based on state-dependent dilatancy. The anisotropic fabric of the sand is studied to investigate the impact of the initial void ratio, initial mean stress, and at-rest coefficient on the void ratio path, stress distributions and paths, and bounding surfaces. The proposed solution provides a framework for the potential use of cavity expansion in sand, considering the fabric change effect, and a benchmark for further developments and numerical calculations by using the SANISAND model. [ABSTRACT FROM AUTHOR]

Severe plastic deformation (SPD) processes offer the possibility of improving the mechanical properties of metallic materials by grain refinement. However, this great potential has so far mostly been applied on a laboratory scale or on small series. Equal-Channel Angular Pressing (ECAP) also enables to integrate the advantages in industrial processes with large output—so far, mainly for bars or thick plates. In this paper, we investigate the ECAP process for sheet metal. Preliminary investigations have shown that cracks form on the surface when aluminum AA5083 sheets are processed. To solve this problem, we determined the Johnson–Cook fracture criterion for the material and modeled the process numerically. The simulation was carried out with the superposition of a backpressure and subsequently implemented and validated experimentally. The semi-finished sheet metal products from the ECAP investigation were then mechanically characterized with microhardness measurements and tensile tests. In addition, the microstructure was investigated with Electron Back Scatter Diffraction (EBSD). Even comparatively small amounts of backpressure (10 MPa) already result in a significant suppression of the crack formation in the numerical and experimental investigations. The microhardness measurements indicate a more homogeneous strain distribution for a sufficient level of applied backpressure which enables the processing of crack-free sheets in multiple ECAP passes. As with ECAP of bulk materials, tensile tests on the processed sheets show a reduced elongation to failure (− 73%) but a significantly increased yield strength (+ 157%) compared to the initial condition of the material. Distinct substructures are found in the EBSD measurements and explain this behavior. The findings provide the basis for using ECAP on an application-oriented scale and demonstrate an advanced manufacturing method for the production of high-strength aluminum sheets. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the effects of semi-angle and platinum tube wall thicknesses on the first-step drawing process of platinum-clad nickel bars using finite element simulation. Three different semi-angles of die (3°, 5°, 7°) and three different platinum tube wall thicknesses (0.275 mm, 0.3 mm, 0.325 mm) were selected in the study. The effects of semi-angle and platinum tube wall thicknesses on drawing force, equivalent stress, cladding behavior and damage coefficients during the first-step drawing process were discussed in detail. The simulated results of cladding condition and damage obtained from Deform 3D V11 software are validated with experimental results, and it was found that the results were in good agreement. The results of this study may provide a reference for the practical production of platinum-clad nickel wires. [ABSTRACT FROM AUTHOR]