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The dynamic behavior of an electrowetting-on-dielectrics (EWOD) actuation process can be linked to certain fluid properties of the actuated polar liquid droplet. After actuation, inertia will lead to droplet oscillations, where the contact angle asymptotically approaches the newly created surface tension equilibrium value. The decay behavior, frequency, and amplitude of these oscillations can be related to material parameters, such as density, viscosity, and mass. In this paper, we study the characteristics of these oscillations, present simulation results, and develop a measurement setup for first observations of oscillations on deionized water droplets. We show that there is a big difference between two grounding schemes, in particular, regarding the dynamic movement of the liquid-gas interface. It turns out that only an electrical grounding from below leads to utilizable oscillations. Finally, we point towards applications for future Lab-on-a-Chip applications. [ABSTRACT FROM AUTHOR]

A novel prefabricated curling rink supported by steel frame and precast concrete blocks has been tested by the 2019 China Youth Curling Open, and that will be responsible for the Beijing Winter Olympics and Winter Paralympics curling competitions in 2022. Due to quite limited researches on the mechanical properties of this professional curling venue, the dynamic behavior of the prefabricated rink under human activities are not well understood. In particular, people and curling stones are potentially more susceptible to the ice vibrations when compared to the traditional curling rink constructed on rammed foundation. Small ice rink vibrations caused by the human locomotion load can make athletes feel uncomfortable, which could affect competition experience, techniques, and skills of the occupancies. At the same time, it can also result in a slightly change of the curling stone trajectories, which ultimately caused the athletes to adopt an erroneous strategy. In order to get a further understanding of the above problems, this paper conducts a series of performance studies based on the 3D finite element model built in ABAQUS and the measured dynamic loads. In this context, it includes the research of on-site measurement of dynamic loads caused by different types of human locomotion on ice sheet, which can provide a reference to the dynamic performance design of prefabricated curling rink supported by similar structural systems. Moreover, the time and amplitude parameters of the footfall forces are extracted to analyze and be compared with the human induced loads results from the existing research, generally obtained on the concrete surface. Then, on the base of the finite element model verified by experiment, the experimental achieved loads are applied for the dynamic analysis to study the vibration acceleration and velocity response of ice sheet. Finally, the vibration response results, including peak acceleration (PA), vibration dose value (VDV), root mean square acceleration (RMS), as well as root mean square velocity were evaluated according to the regulations proposed by the International Olympic Committee and the vibration evaluation standards suggested by AISC design guide, ISO guideline, and VC curves. The analysis results indicate that innovation prefabricated curling ice rink supported by steel-concrete composite floors can meet the requirements of the event and has the prospect of promotion and application. [ABSTRACT FROM AUTHOR]

A thorough study of the parameters influencing the operation of devices based on nanowired alumina substrate is presented. The basic structures are realized by growing metallic nanowires inside alumina porous substrate. The control of the areas wherein growth occurs allows building of various microwave devices supported on the filled template. The performances of these devices depend on the material parameters and topology/geometry in presence. These devices have the particularity to combine nanoscale, through the use of nanowires, and millimeter scale that is characteristic of microwave devices and their associated operating wavelength. The gap between the two‐scale ranges implies that analytical models and numerical simulation tools have to be combined to modelize and design performant microwave devices, such as Nanowired Substrate Integrated Waveguides (NSIWs) devices that are the subject of the paper. A deep parametric analysis of the properties and operation of the basic NSIW is presented and is followed by the illustration of two designs: a simple NSIW line, and an EBG NSIW filter. [ABSTRACT FROM AUTHOR]

The use of 3D glass as a cover will significantly improve the stylish sense of the product and provide a wider display interface. However flexible film are notoriously difficult to fully conform to non‐developable surface such as spheres. The greatest challenge when trying to attaching flexible display to 3D spherical glass is avoiding wrinkling phenomenon at the edge of flexible display. In this paper the finite element method is used to study the optimization of the stack‐up to avoid obvious wrinkling phenomenon. We confirm that the modulus and thickness of Optical Clear Adhesive(OCA) between flexible modulus and 3D glass cover have decisive impact on the formation of wrinkles. A wrinkle‐free watch product was successfully fabricated by replacing the low‐modulus OCA with high‐modulus OCA or by reducing the thickness of low‐modulus OCA to 50μm. [ABSTRACT FROM AUTHOR]

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]

Surface enhanced Raman spectroscopy or surface enhanced Raman scattering (SERS) being a very powerful technique for quantitative and qualitative analysis finds application in low concentration detection of chemical and biological samples. In this work, we have presented a complete methodology of simulating nanoparticles-based SERS substrate. Different configurations namely single nanoparticle, dimer, trimer and tetramer nanoparticle clusters are simulated and enhancement factor for each configuration is estimated. Presented simulations are carried out with COMSOL Multiphysics software using Electromagnetic Waves module (Wave Optics) in frequency domain. The model of gold nanoparticle is established to determine the scatter field, which was further used to estimate the enhancement factor. Simulation results thus obtained are then validated with experimental results. The simulation study using the COMSOL Multiphysics tool helps in the design and development of the SERS substrate for maximum electromagnetic enhancement at a particular wavelength. The presented simulation methodology will be helpful for various SERS related computational studies in future. Presented approach helps in understanding the effect of various parameters such as particle size, inter particle gap, excitation wavelength, etc. on the EM enhancement. Simulating various possibilities before fabrication helps in saving money and time. For device realization, gold nanoparticles are synthesized using Turkevich method to achieve uniform and spherical nanoparticles. Synthesized nanoparticles (40–45 nm radius) were drop casted on a porous cellulose paper substrate to realize a SERS substrate. Nanogaps created between nanoparticles become the hot-spot locations leading to electromagnetic coupling and hence the Raman signal enhancement. Paper based SERS substrate is tested with Rhodamine B (1 μM) test sample. Enhancement of 106 was observed with the developed SERS substrate. UV–Vis spectrometer and Raman spectrometers are used for various characterizations. • The work presents the comprehensive simulation strategy for nano particle-based SERS substrates. • Simulation results present the effect of nanoparticle size and inter particle gap on Raman enhancement. • Different configurations namely, single particle, dimer, trimer and tetramer are simulated and results are discussed. • Gold Nanoparticles are synthesized and SERS substrate using paper is prepared for Raman enhancement and results are presented. • Presented work demonstrates a low-cost SERS substrate with its analytical and experimental investigation. [ABSTRACT FROM AUTHOR]

In this paper we present a multidisciplinary modeling of a MEMS-based electrodynamic microsensor, when an additional vertical offset is defined, aiming acoustic applications field. The principle is based on the use of two planar inductors, fixed outer and suspended inner. When a DC current is made to flow through the outer inductor, a magnetic field is produced within the suspended inner one, located on a membrane top. In our modeling, the magnetic field curve, as a function of the vertical fluctuation magnitude, shows that the radial component was maximum and stationary for a specific vertical location. We demonstrate in this paper that the dynamic response of the electrodynamic microsensor was very appropriate for acting as a microphone when the membrane is shifted to a certain vertical position, which represents an improvement of the microsensor's basic design. Thus, a proposed technological method to ensure this offset of the inner inductor, by using wafer bonding method, is discussed. On this basis, the mechanical and electrical modeling for the new microphone design was performed using both analytic and Finite Element Method. Firstly, the resonance frequency was set around 1.6 kHz, in the middle of the acoustic band (20 Hz – 20 kHz), then the optimal location of the inner average spiral was evaluated to be around 200µm away from the diaphragm edge. The overall dynamic sensitivity was evaluated by coupling the lumped elements from different domains interfering during the microphone function. Dynamic sensitivity was found to be 6.3 μV/Pa when using 100 µm for both gap and vertical offset. In conclusion, a bandwidth of 37.6 Hz to 26.5 kHz has been found which is wider compared to some conventional microphones. [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]

This paper proposes an analytical model for the stress-strain state in a welded joint with a hard single-V butt weld. Analytical expressions for the stress-strain state in both the hard weld and the mild main material subjected to elasto-plastic deformation are proposed. In order to verify the proposed expressions, a finite element simulation of the stress-strain state in a welded joint with a hard single-V butt weld was carried out and the results were compared to the analytical results obtained applying the proposed analytical model. The analytical solution was basically consistent with the finite element analysis results. The proposed analytical model can be used in design practice for assessment of the stress-strain state in welded joints. [ABSTRACT FROM AUTHOR]

In glass compression molding, most current modeling approaches of temperature‐dependent viscoelastic behavior of glass materials are restricted to thermo‐rheologically simple assumption. This research conducts a detailed study and demonstrates that this assumption, however, is not adequate for glass molding simulations over a wide range of molding temperatures. In this paper, we introduce a new method that eliminates the prerequisite of relaxation functions and shift factors for modeling of the thermo‐viscoelastic material behavior. More specifically, the temperature effect is directly incorporated into each parameter of the mechanical model. The mechanical model parameters are derived from creep displacements using uniaxial compression experiments. Validations of the proposed method are conducted for three different glass categories, including borosilicate, aluminosilicate, and chalcogenide glasses. Excellent agreement between the creep experiments and simulation results is found in all glasses over long pressing time up to 900 seconds and a large temperature range that corresponds to the glass viscosity of log (η) = 9.5 – 6.8 Pas. The method eventually promises an enhancement of the glass molding simulation. [ABSTRACT FROM AUTHOR]

An innovative Stewart platform (hexapod)-based testing rig is designed, constructed, and used herein to experimentally characterize a seismic isolation device named roll-in-cage (RNC) isolator. The testing rig is a result of integrating a mechanical extension, or upgrade, to the hexapod. This allows for performing up to 15 standard mechanical tests using cylinder, block, prism, beam, plate, or bar specimens, besides reduced-scale prototypes of seismic isolation bearings. Several one-tenth reduced-scale prototypes of the RNC isolator are experimentally examined in this paper using this testing rig. Cyclic horizontal displacement tests are performed considering different test parameters including shear displacement amplitude, axial load, and loading frequency. The RNC isolator's force-displacement relationships, shear stiffness, and damping properties are investigated. Vertical cyclic displacements are also applied to examine the RNC isolator's capability to withstand vertical axial tension. Furthermore, tests at the ultimate level consisting of an increasing-amplitude shear loading, beyond the bearing's design displacement limit, are also carried out to investigate the bearing's behavior after activating its inherent self-stopping, or buffer, mechanism. The obtained experimental outputs are then related to analytical and thorough FEM simulation outputs. This relation is intended to validate those previously developed mathematical and numerical models of the RNC isolator based on the real experimental measurements in this paper. A comparative study of the results is then performed, and the main observations are highlighted. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Resin transfer molding (RTM) technologies are widely used in automotive, marine, and aerospace applications. The need to evaluate the impact of design and production critical choices, also in terms of final costs, leads to the wider use of numerical simulation in the preliminary phase of component development. The main issue for accurate RTM analysis is the reliable characterization of the involved materials. The aim of this paper is to present a validated methodology for material characterization to be implemented and introduce data elaboration in the ESI PAM-RTM software. Experimental campaigns for reinforcement permeabilities and resin viscosity measurement are presented and discussed. Finally, the obtained data are implemented in the software and then compared to experimental results in order to validate the described methodology. [ABSTRACT FROM AUTHOR]

Finite element simulations are being more and more applied when studying the crash-worthiness of vehicles during impact. This paper deals with setting up such a simulation and discusses several ways to simplify and verify a simulated crash. For this purpose, a notch impact-testing machine will be released from a certain angle and crash into a model constructed with three different wall thicknesses. The plastic and elastic deformation is measured in the front of the model and is then used for validation of the simulation. In the end, the simulation was found to be in good agreement with the real crash data. [ABSTRACT FROM AUTHOR]

Presently, the main mechanism for phase transformations in machining of steels is not absolutely clear and is still subject to research. This paper presents, three different approaches for modeling phase transformations during heating in machining operations. However, the main focus lies on two methods which can be classified into a stress related method and a thermal activation related method for the description of austenitization temperature. Both approaches separately showed very good agreements in the simulations compared to the experimental validation but were never compared in a simulation. The third method is a pre-calculated phase landscape assigning the transformation results based on a micro-mechanically motivated constitutive model to the workpiece in dependence on the temperature and strain history. The paper describes all three models in detail, and the results are also presented and discussed. [ABSTRACT FROM AUTHOR]

Pre-stress hardening grinding (PSHG) is a complex process that combines pre-stress grinding and grinding hardening. Pre-stress, as input stress, has been working throughout the grinding process. Since the grinding heat generates on the surface of material, unloading the pre-stress at different time nodes will affect the phase change after the grinding process. In this paper, the effect between pre-stress unloading time and the grinding hardening is further studied. In order to study the effect of pre-stress unloading time, experiment and simulation are used for analysis and to optimize grinding hardening layer in the PSHG process. After the PSHG experiment, the microstructure of the grinding-hardened surface is observed and investigated by scanning electron microscopy (SEM). And the SEM images are binarized to obtain the martensite content on the hardened surface. It is showed that as the pre-stressed unloading time increases, the martensite content increases. Then, a simulation model is established based on the heat conduction equation, initial boundary conditions, and latent heat of phase change. According to the simulation results, three time nodes are selected to study the unloading pre-stress. The pre-stress unloading time affects the mechanical thermal stress of the material surface layer, but has little effect on the inner layer. In the simulation, the influence of the pre-stress unloading time on the mechanical-thermal stress of the surface is compared. Finally, the effects of pre-stress unloading time on the phase transition and phase transition stress are discussed. [ABSTRACT FROM AUTHOR]

Unreinforced masonry infills are widely used in many parts of the world and it is common practice for seismic design to use simplified methods that usually do not take into account the interaction between the infill and the structure. Starting from the 1950s, many researchers have investigated the lateral response of masonry infills focusing on several different topics. The scientific interest on masonry infills is continuously raising due to the unsatisfactory seismic response of the infilled frame structures observed during post-event inspections and to the difficulty to contrive a widely scientifically and practical recognized solution. Although some modern codes consider the presence of infills with some specifications to prevent damage in the masonry panels and global and local effects on the structure, an effective evaluation of these detrimental effects has not been achieved yet. Within this paper, a FEM simulation of in-plane pseudo-static cyclic tests on a RC frame specimen infilled with unreinforced Autoclaved Aerated Concrete (AAC) masonry infill has been performed in order to study accurately the influence and the interaction of the infill with the RC structure. The experimental results performed by Calvi and Bolognini (J Earthq Eng 5:153-185, 1999), and Penna and Calvi (Campagna sperimentale su telai in c.a. con tamponamenti in Gasbeton (AAC) con diverse soluzioni di rinforzo” (in Italian), 2006) on one-bay one-storey full scale specimens are taken as reference. Non-linear static analyses using a “meso-modelling” approach have been carried out. The masonry used in the model has been calibrated according to tests of mechanical characterization and to in-plane cyclic tests on load-bearing AAC masonry conducted by Costa et al. (J Earthq Eng 15:1-31, 2011). The analyses performed have allowed to investigate the local effects on the frame and, in particular, the changes in the moment and shear demands on the RC elements due to the presence of the AAC infill in comparison with the ones in the bare structure, and to estimate the thrust and the contact length activated by the infill on the frame. [ABSTRACT FROM AUTHOR]

Fatigue is one of the main reasons of fracture in mechanical components. Generally performing experiments is a useful and effective method for determination of fatigue life. In this paper, results of different notch geometry effects on the fatigue life under mixed mode I and III were studied experimentally and numerically. For this purpose, fatigue specimens were manufactured according to the ASTM-A370 standard and all the specimens were quenched and tempered. Two types of notch geometries, V-shape and U-shape were considered in this study. The fatigue life was determined experimentally for each notch geometry and results were verified by finite element method simulation. Fractographic investigation was done broadly to determine cause of failure in the specimens. Our results showed that the notch geometry had significant effect on the fatigue life. Fatigue crack growth in the V-shape notch specimens happened quickly and the maximum fatigue life reduction occurred for that. [ABSTRACT FROM AUTHOR]

Digital shearography is an interferometric technique, which is often used for defect detection on composite structures. The measurement is fast and nondestructive and thus suitable for the application to cultural heritage. However, a major drawback of the technique is the indirect measurement, because surface strain is used to detect subsurface defects. So the determination of depth, size, and type of the defects is rather difficult. To overcome this issue, we use a combination of finite element method simulation and shearographic measurement. Due to the comparison of both data sets, the inverse problem can be solved in a more reliable way. In this paper, we investigate the application of finite element method simulation for an improved defect detection on anisotropic material. We validate the technique on a wooden sample with notches on the backside. [ABSTRACT FROM AUTHOR]

[Display omitted] • Theoretical formulas describing wave propagation in multilayer are derived. • The attenuation is dominated by physical properties of the interface and stride. • The attenuation is regulated by the ratio of single-layer thickness to the FWHM. • A novel dynamic design method for coatings is presented. 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. [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]

The grind-hardening process aims to increase the surface hardness of the material through the dual action of the mechanical and thermal load. A novel approach to model the process and predict the hardness penetration depth was developed based exclusively on the prediction of austenite-martensite transformation. A combined micro and macro scale approach was implemented to forecast the temperature reached in the surface starting from the action of a single grain and using its specific cutting power to design a moving heat source representing the interaction between the grinding wheel and the material. The martensitic transformation temperature considered in this paper takes into consideration the fast heat cycle typical of this process. In order to validate the model, tangential surface grinding tests were performed on 42CrMo4 and microstructural analysis with micro-hardness measurements were performed. This research presents a first step in developing a grinding process simulation that includes multi-grain grinding, real grain geometries, binder effect, and real workpiece-grinding wheel kinematics. [ABSTRACT FROM AUTHOR]

Flexible-die forming methods such as hydroforming (HF) and rubber pad forming (RPF) allow producing a variety of complex tubular components that are difficult to fabricate by means of conventional forming. In this paper, firstly, in the bulging of a tube with oil pressure using numerical approach, weld-seam was modeled as a mechanical defect and non-homogeneity factor was calibrated by experimental observations and Vickers micro-hardness testing. Forming limit diagram (FLD), as well as effective plastic displacement factor, was utilized to estimate the initiation and evolution of damage, respectively. Then, with the aim of achieving a defect-free part in RPF process, the effect of lubricating conditions was experimentally and numerically examined. The sound parts were obtained using nylon and drawing oil, respectively, at the tube/rubber and the tube/die interaction surfaces. The results represented that by utilizing the accurate non-homogeneity factor, the numerical method can closely predict the damage in both processes. Also, it was indicated that due to friction in RPF versus HF, the tube was pushed into the bulged zone and the strain path tended to the left side of FLD; therefore, the formability of tube was meaningfully improved. [ABSTRACT FROM AUTHOR]

Copyright of Technical Transactions / Czasopismo Techniczne is the property of Sciendo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Most used dental implants for human dental prostheses are of two steps type: first step means implantation and, after several months healing and osseointegration, second step is prosthesis fixture. For sure, dental implants and prostheses are meant to last for a lifetime. Still, there are unfortunate cases when dental implants break. This paper studies two steps dental implants breakage and proposes a set of instruments for replacement and restoration of the broken implant. First part of the paper sets the input data of the study: structure of the studied two steps dental implants based on two Romanian patents and values of the loading forces found in practice and specialty papers. In the second part of the paper, using DEFORM 2D™ FEM simulation software, worst case scenarios of loading dental implants are studied in order to determine which zones and components of the dental implant set are affected (broken). Last part of the paper is dedicated to design and presentation of a set for extracting and cutting tools used to restore the broken implant set. [ABSTRACT FROM AUTHOR]

In the metal cutting process, tool-chip contact length directly affects the chip deformation, cutting temperature distribution and tool wear. We use the DEFORM-3D finite element analysis software to simulate the drilling process of a staggered teeth BTA drill, analyze the chip formation process, deformation pattern of each cutting tooth of the staggered teeth BTA drill and study the variation pattern of the tool-chip contact length with the cutting speed and feed during the drilling process of 45 steel and 20CrMnMo. The results show that the tool-chip contact length of each cutting tooth of the BTA drill is different and that the tool-chip contact length increases with the decrease of the material strength and the cutting speed and increases with the increase of the feed. We verify the reliability of the finite element simulation by comparing the cutting force simulation data with the cutting force experimental data. [ABSTRACT FROM AUTHOR]

Bulb turbine units are one of the most installed turbines in run-of river projects with relatively low head. In order to enlarge the useful life of these turbines and avoid fatigue problems and cracks, it is of paramount importance to understand and determine the most relevant parameters and their influence on the dynamic response of the structure. In this paper, the modal characteristics of a bulb turbine unit in operation is numerically investigated, considering the rotation effect. A FEM model including alternator, shaft, runner and fluid is developed and the boundary conditions are determined. Firstly, the modal characteristic of the runner under different blade opening are analyzed. Then the influence of the rotation on the modal characteristic of the shaft and runner is discussed. The numerical method is verified by comparing with experimental results of a rotating and submerged disk. The results show that the runner modes are mainly blade-modes，which can be grouped according to the blade number, one jellyfish mode and four local modes in each group. A modified Campbell diagram of the global modes and a transformation matrix of natural frequency between dry modes and wet modes are proposed. Results of this study helps to understand the most influencing parameters, such as the added mass effect of water combined with the rotation. The proposed modified Campbell diagram could be used for an accurate calculation of natural frequencies and avoid possible resonance problems in future designs of bulb turbine units. [ABSTRACT FROM AUTHOR]

Friction behavior in a sliding contact is strongly influenced by the surface topography of the bodies in contact. This also applies to friction clutches. Even small differences in surface topography may cause significant differences in friction behavior. Thus, it is important to be able to characterize the micro-contact of the rough sliding surfaces, which are, in the case of a clutch, steel plate and friction material. One important measure for the characterization of the micro-contact is the real area of contact. Another important aspect is the contact pattern. The article introduces a method to implement a FEM (Finite Element Method) model from real surface measurements. Real surface topography of the friction pairing is considered. The simulation method is applied to different friction pairings and operating conditions. Computational results with rough and smooth steel plates, new and run-in friction linings, and different nominal surface pressure verify the model. In addition, the results on real area of contact between a steel and a friction plate are compared with published values. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Chongqing University of Posts & Telecommunications (Natural Science Edition) is the property of Chongqing University of Posts & Telecommunications and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Display omitted] • Two innovative strategies have been proposed to protect energy harvesters with frequency up-conversion mechanism from mechanical overload. • Finite element method has been used to model and analyse the proposed protection strategies. • Experiments have been conducted to verify the strategies and modelling. • The capability of protecting the harvesting device from unexpected overload is demonstrated. • The protection mechanisms and damping effects of the proposed strategies are discussed. Vibration energy harvesters utilising the frequency up-conversion mechanism have been effective in harvesting low-frequency ambient vibrations. However, the mechanical impact required for this process could also damage the devices when excessive load is applied. To address this issue, this paper presents novel protection strategies for energy harvesters with a frequency up-conversion mechanism, including a ring-type stopper within the resonant system and specially designed impact protection components (IPC) within the impact system. By applying these methods, the influence of excessive input excitation has been mitigated, and thus, the reliability and durability of the device have been improved. Finite element modelling has been employed to model the proposed protection methods, and then experiments have been conducted to verify and refine the modelling. Stress analysis is finally conducted based on the refined model to validate the effectiveness of the protection strategies. The results demonstrate that the proposed strategies are capable of protecting the harvesting system from excessive input excitations, which means the device functions effectively in the operating state and decelerates the growth rate of maximum stress and acceleration in the limiting state. This research contributes valuable insights into the development of effective protection strategies for energy harvesters with frequency up-conversion mechanisms, thereby improving their durability and performances in real-world applications. [ABSTRACT FROM AUTHOR]

This article presents a research study involving different simulations of crash tests by means of the finite element explicit dynamic software Ansys LS-Dyna to determine the roadworthiness of a fully composite chassis lightweight solar vehicle and its conformity to the World Solar Challenge (WSC) regulations. Furthermore, the paper describes the results of crash test simulations in conditions comparable with those of the standard homologation test, with an initial velocity of 15.5 m/s against a rigid barrier considering overlaps of 50% and 100%. The velocity measured at the base of the seat was later used in a sled test with a dummy to calculate the Head Injury Criterion (HIC), a number proportional to the probability of head injury caused by the impact. The values remained within the threshold of acceptability with overlap at 50% but exceeded the limit with the 100% overlap. With no load limiter implemented in the model, the seatbelt caused contact forces with the chest up to 14 kN against 6 kN of the typical load limiter used in road cars to limit damage to ribs and internal organs. Finally, the possibility of improving the front crash box was investigated by changing the crash box's planar sandwich structure with corrugated ones and layup without foam between the carbon layers. Various values of semi-amplitudes (A) of the sinusoidal profile have been tested. With a value of A of 6 mm, the capacity to absorb energy from an impact at 9 m/s was close to the original configuration. [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]

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]

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]

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]

The pre-stressed hardening grinding (PSHG) combines with the advantages of pre-stressed grinding and grinding hardening. In order to study the characteristic of PSHG, especially its residual stress within a hardened layer after PSHG, the PSHG experiment was carried on. Combining with theory and experiment results, the variation and its mechanism of residual stress were studied. The paper shows the PSHG can obtain a hardened layer with controllable residual stress after the process. The residual stress decreases with the increasing of feeding speed and grinding depth. When the grinding depth is small, the tensile residual stress decreases with the increasing of pre-stress. And when the grinding depth is large, the compressive residual stress decreases first and then increases with the increase of pre-stress because of the comprehensive effect of heat and phase transformation. Then, a finite element method (FEM) simulation was performed to study the variation of thermal stress in a hardened layer after PSHG process. Distribution and variation of thermal stress were obtained. In the end, according to the relationship between residual stress and thermal stress, the distribution and variation mechanisms of phase transformation stress were obtained and studied. They vary along with the level of phase transformation. The compressive phase transformation stress increases with the increasing of grinding depth. And due to the pre-stress's influence on the phase transformation, it decreases first and then increases with the increase of pre-stress. [ABSTRACT FROM AUTHOR]

It is necessary to improve parameters of forging lines, because it leads to higher productivity and minimization of costs during production process. This paper deals with parameters of modern preforming processes such as forging rolls and cross wedge rolling. These parameters are compared with respect to maximal forces, moments and total energy consumption necessary for production of identical part. [ABSTRACT FROM AUTHOR]

By producing of critical components in the aerospace industry is widely used the β-titanium alloy Ti10V2Fe3Al (Ti-1023) due to its extremely high ratio of strength to density, its great resistance to fatigue, its excellent resistance to corrosion and fracture toughness. This material is characterized by significant difficulties in machining. Substantial assistance in the study of the titanium alloy Ti-1023 machinability can provide a simulation of machining by numerical modeling. This paper presents the results regarding the creation of the FEM models for the cutting processes of the titanium alloy Ti-1023. The created FEM cutting models were constantly verified with experimental tests of the kinetic machining characteristics and analyses of the chip morphology by orthogonal and oblique cutting as well as flat end milling with different depths of immersion. A Johnson-Cook model was used as material model of the workpiece and the damage mechanism of the workpiece is reproduced with the Cocroft and Latham model. The parameters of material and fracture model were determined by DOE study. Comparing the experimentally established and the simulated kinetic machining characteristics and chip morphology confirms that the created FEM models are of a good quality. The size of error for simulating the chip dimensions does not exceed 10 % and ranges between 10 and 30 % for simulating the resultant forces. [ABSTRACT FROM AUTHOR]

The slab method can rapidly predict the rolling force and torque in metal forming processes and a large amount of CPU time can be saved. Up to now, the work hardening effect has not been considered in the slab analysis for forging process of double-layer clad sheet. Evaluation of considering or eliminating the work hardening effect on material behavior in the slab analysis of three layer clad sheet forging process and investigating the subsequent effects on the process outputs are novel subjects considered in this paper. The pressure distribution as well as the forging force is investigated for both conditions. In addition, three layer clad sheet forging process is entirely simulated using ABAQUS/Explicit software. The results show that considering the work hardening effect on material behavior will result into having higher stresses and forces in the process. Moreover, the results of considering the work hardening effect have better agreements with those from simulation. Finally, some experiments were performed on forging process of two layer Al/Cu clad sheet to evaluate the bonding quality of sheets. Therefore, forging process can be used for producing multi-layer clad sheets in various industries. [ABSTRACT FROM AUTHOR]