Numerical Experimental Investigation Research Articles

EXPERIMENTAL AND NUMERICAL SIMULATION OF A NOVEL MAGNETIC POLE REPULSIVE PASSIVE DAMPER FOR VIBRATION CONTROL

This article presents a novel magnetic pole repulsive damper (MPRD) incorporating neodymium magnetic repulsive blocks and springs. The study explores the mechanical properties of the springs and magnetic blocks through numerical simulations using ANSYS and experimental evaluation. To gain deeper insights into the behaviour of the MPRD, an accurate and high-fidelity finite element model was developed. The evaluation process involved a comprehensive comparison between the numerical simulations and experimental tests, explicitly focusing on cyclic compression–tension forces. The study encompassed the functioning, design implications, fabrication technique, mechanical performance, and numerical simulation for the cyclic compression–tension forces of the MPRD. The cyclic compression–tension tests revealed a gradual increase in force, with the MPRD achieving an ultimate force of 2,877 kN. The MPRD exhibited robust hysteresis behaviour in cyclic loading, showing its capacity to undergo and uphold the stability of the combination of its materials. The cyclic compression–tension results indicated the maximum force carrying capability of the damper. This resilience implies its full reusability in such scenarios. The comparison between cyclic compression–tension tests confirmed the alignment between the numerical simulation and experimental investigation.

Hydrodynamic performance of a biomimetic undulating fin robot under different water conditions

Inspired by the agile swimming behavior of the Black Ghost Knife Fish utilizing undulating propulsion in complex aquatic environments, this study investigates the locomotion principles and hydrodynamic performance of an undulating propulsion system under varying hydrodynamic conditions through numerical simulations and experiments. The influence of the fin aspect ratio on the thrust performance of the robot was explored, revealing a linear correlation between the aspect ratio and thrust generation. Furthermore, based on an aspect ratio of 0.3, the effects of frequency, amplitude, and wavenumber on the robot’s swimming performance were examined. The results indicated a quadratic relationship between frequency and thrust, a linear relationship between amplitude and thrust, and a trend where thrust initially increased and then decreased with wavenumber, reaching an optimal level around wavenumber 1. Using numerical simulations and experimental investigations, the thrust performance of the robot under wave conditions demonstrated a noticeable reduction in hydrodynamic performance compared to still water conditions. The effects of frequency, amplitude, and wavelength on thrust remained consistent with still water conditions, but the instantaneous thrust became unstable. The current conclusions provide valuable insights for designing and optimizing undulating propulsion robots, offering systematic guidance for selecting appropriate motion parameters to accomplish different tasks.

Observing suppressed polarization in flexible ferroelectric negative capacitance field effect transistors

Negative capacitance (NC) has the potential to enable low power microelectronics beyond the fundamental thermionic limit, and it has been theorized that the thermodynamically unstable NC of ferroelectrics can be stabilized by linear dielectric, making negative capacitance ferroelectric field effect transistors (NC-FeFET) possible. Nevertheless, the validity of NC as a physical concept for ferroelectrics remain contentious despite numerous theoretical and experimental investigations, and the intrinsic ferroelectric NC with suppressed polarization has not been demonstrated except locally at vortex core. While NC-FeFET with subthreshold swing (SS) lower than 60 mV/dec limit has been reported, such device characteristics has not been directly connected to suppressed polarization at materials’ level, and alternative mechanisms other than NC have also been proposed. Here we demonstrate stable sub-60 mV/dec SS with hysteresis free IV in NC-FeFET based on SrTiO3/Pb(Zr0.1Ti0.9)O3/SrTiO3 heterostructure, and observe its suppressed polarization at both macroscopic and microscopic scales. The intrinsic ferroelectric NC thus is experimentally confirmed and directly connected to NC-FeFET performance, and the mica-based device is also highly flexible and robust under cyclic bending as well as extended heating.

Investigation of energy trapping effect for nonlinear guided waves in a topographical structure

Cumulative second harmonic generation (SHG), where the amplitude of the generated second harmonic increases with propagation distance, is commonly utilized to enhance the measurability of nonlinear guided waves by providing a sufficient signal-to-noise ratio. Investigating and confirming the cumulative SHG of feature guided waves (FGWs) in topographical waveguides is crucial for accurately assessing material nonlinearity in such structures. This study examines the cumulative SHG of FGWs propagating in a typical topographic structure of a welded joint through both numerical simulations and experimental investigations. A theoretical model is developed using the semi-analytical finite-element (SAFE) method and perfectly matched layer (PML) to analyze the propagation characteristics of FGWs in a welded joint. The numerical and experimental results provide verification of the “trapping effect” of FGWs within the welded joint. Furthermore, the “cumulative effect” of SHG of FGWs is observed. Remarkably, both the experimental and numerical findings demonstrate that cumulative SHG of FGWs can be achieved by employing suitable mode selection and frequency tuning in the topographic structure, which aligns well with the theoretical predictions. This investigation contributes to advancing our understanding of cumulative SHG in FGWs propagated within topographical structures. These findings have practical implications for accurately characterizing material nonlinearity in topographic waveguides.

Numerical simulation and experimental investigation for the dynamic rocking response of two stacked rigid blocks

A system of two stacked rigid blocks (TSRBs), such as a statue on a pedestal, is extensively constructed and utilized. However, the numerical simulation of its dynamic response has been a crucial and challenging problem due to the diversity of motion patterns and the nonlinearity in the impacts. Therefore, a high-accuracy and appropriate numerical simulation approach for solving the rocking response of TSRBs was proposed in this paper. First, their rocking patterns were presented, and the judgment diagram of their transitions was defined. Then, the rocking equations of the motion and the formulas of the post-impact angular velocities were introduced. Next, to solve the rocking response of TSRBs, a novel numerical method stemming from the Rosenbrock method and the substep-two-step method was proposed and preliminarily verified. Moreover, free and forced vibration experiments were conducted to verify its accuracy further, and the regularity of the motion was summarized. Finally, parametric analyses of the applications was performed on statue-pedestal systems to investigate the influence of the wall thicknesses and height-to-width ratios of the pedestals on the dynamic response. The results indicate that the proposed method has favorable stability, acceptable accuracy, and high computational efficiency due to its accurate impact point identification and rocking pattern determination. In practice, to reduce the dynamic response of statues, it is preferred to place pedestals with smaller wall thicknesses and larger height-to-width ratios under statues.

Elucidating the process mechanism in Mg-to-Al friction stir lap welding enhanced by ultrasonic vibration

The composite structures/components made by friction stir lap welding (FSLW) of Mg alloy sheet and Al alloy sheet are of wide application potentials in the manufacturing sector of transportation vehicles. To further improve the joint quality, the ultrasonic vibration (UV) is exerted in FSLW, and the UV enhanced FSLW (UVeFSLW) was developed for making Mg-to-Al dissimilar joints. The numerical analysis and experimental investigation were combined to study the process mechanism in Mg/Al UVeFSLW. An equation related to the temperature and strain rate was derived to calculate the grain size at different locations of the weld nugget zone, and the effect of grain size distribution on the threshold thermal stress was included, so that the prediction accuracy of flow stress was further improved. With such modified constitutive equation, the numerical simulation was conducted to compare the heat generation, temperature profiles and material flow behaviors in Mg/Al UVeFSLW/FSLW processes. It was found that the exerted UV decreased the temperature at two checking points on the tool/workpiece interface from 707/671 K in FSLW to 689/660 K in UVeFSLW, which suppressed the IMCs thickness at Mg-Al interface from 1.7 µm in FSLW to 1.1 µm in UVeFSLW. The exerted UV increased the horizontal materials flow ability, and decreased the upward flow ability, which resulted in the increase of effective sheet thickness/effective lap width from 2.01/3.70 mm in FSLW to 2.04/4.84 mm in UVeFSLW. Therefore, the ultrasonic vibration improved the tensile shear strength of Mg-to-Al lap joints by 18 %.

Combination of wavelet transform and extreme learning machine for detecting damages in composite plates

This paper reports a two-stage damage detection method for effectively identifying multi-damage in composite plate structures. The first stage focuses on detecting damage locations using the wavelet transform to reveal the singularities from a modal shape of the composite plate. In the second stage, extreme learning machine (ELM) is employed to search the damage severities from the pre-calculated damage evaluation database (the relationship between the natural frequencies and severities). Using finite element method (FEM) and experimental modal analysis (EMA), the numerical simulations and experimental investigations are executed to verify the effectiveness of the combination method for simply supported composite plates structures with various damages. Results show that the proposed two-stage method is effectively to identify multiple damages in composite plate structures with reasonable precision might be extend to real-world applications.

Numerical analysis and experimental investigation of residual stress and properties of T-joint by a novel in-situ laser shock forging and arc welding

A novel technique, referred to as Weld-LSF, has been proposed for the low-stress manufacturing of T-joints through in-situ synchronous assisted arc welding, employing laser shock forging. This innovative process introduces plastic deformation in the deposited weld seam at elevated temperatures, effectively reducing the tensile residual stresses (TRS) associated with welding. The thermal-mechanical coupling finite element model for Weld-LSF has been established, combining the classical bar-frame model and the inherent strain theory. The mechanism behind achieving low-stress welding of T-joints through in-situ LSF has been analyzed. Subsequently, experimental investigations were conducted using Q345 base metal and ER60–5 welding wire to study the influence of in-situ LSF on the microstructure and mechanical properties of the specimens. The results demonstrate that by introducing in-situ LSF at higher temperatures in the weld seam, tensile residual stresses are transformed from high to low levels, with the average TRS reduced from 342 MPa to 185 MPa, representing a significant reduction of 45.9 %. In-situ LSF forms a hardened layer with a depth of approximately 0.5 mm on the surface of the weld seam, albeit with certain depth limitations. Furthermore, the in-situ LSF treatment addresses the issue of poor ductility caused by stress concentration at the weld toe of T-joints, achieving a desirable combination of strength and ductility. The feasibility of in-situ LSF technology in welding fabrication has been established. In comparison to traditional welding techniques, the in-situ LSF treatment offers promising prospects for achieving low-stress welding, thereby enhancing the mechanical performance and fatigue life of the welding process.

Characterization of Polymeric Composites for Hydrogen Tank.

Carbon neutrality has led to a surge in the popularity of hydrogen tanks in recent years. However, designing high-performance tanks necessitates the precise determination of input material properties. Unfortunately, conventional characterization methods often underestimate these material properties. To address this limitation, the current research introduces alternative designs of ring tensile specimens, which enable accurate and reliable characterization of filament-wound structures. The advantages and disadvantages of these alternative designs are thoroughly discussed, considering both numerical simulations and experimental investigations. Moreover, the proposed ring tensile methods are applied to characterize thermoplastic composites for hydrogen storage tanks. The results indicate that the mechanical strengths and stiffness of carbon fiber-reinforced thermoplastic Elium® 591 composites closely match those of epoxy-based composites. This newfound accuracy in measurement is expected to contribute significantly to the development of recyclable hydrogen tanks.

Experimental-numerical investigation and design of bolted-cover plate connections under bending for modular steel buildings

Experimental-numerical investigation and design of bolted-cover plate connections under bending for modular steel buildings

Experimental investigations on composite stub columns: hollow sections with embedded solid core made of HSS

AbstractA new composite column system using a solid core and an encasing jacket made from (ultra‐)high‐strength structural steel filled with concrete is presented in this paper that can serve as a promising alternative to prefabricated reinforced concrete columns from an economic and constructive point of view. Within the scope of a research project, this topic is being investigated in more detail by means of numerous experimental and theoretical investigations to enable the use of (ultra‐)high‐strength steels in the future. In this article, stub column tests were carried out to assess the resistance to pure compression and to gain insights into the structural performance of this new composite column system. Novel measurement techniques are used to evaluate the different normal force bearing components of the steel core, the hollow steel section, and the filled concrete over the entire loading process. A clear dependence of the load‐bearing behaviour on the cross‐sectional shape and the load introduction form (full‐surface load introduction vs. load introduction via the core surface) was observed.

Numerical Modeling, Experimental Investigation, and Optimization of a Micro Hot Embossing Process

Abstract This paper describes the development of a finite element simulation model and a self-made low-cost experimental setup for the micro hot embossing process. The simulation model incorporates stress relaxation behavior through the utilization of the generalized Maxwell model. It also considers thermal expansion and contact friction effects, enabling accurate prediction of the deformed pattern of polymethyl methacrylate (PMMA). Simulations and experiments were performed for various pressure and temperature combinations, and the resulting pattern profile depths were found to be in good agreement, between the simulation and experimental results. In addition, the simulation model was used to generate response surfaces through face-centered central composite design (CCD) to identify the ideal combination of process parameters of the micro hot embossing process for creating a patterned SMD (surface mount device) LED chip panel.

Experimental investigations and three-dimensional computational fluid dynamics modeling of sediment transport in tanks influenced by cavities

Sediment transport is a very complex process in urban water systems, and sediment movement mechanisms are poorly understood. However, it is necessary to comprehend sediment transport to optimize stormwater and sewer tank designs for better performance in trapping particulate pollutants. This work focuses on the numerical simulation and experimental investigation of tank sediment transport. In the numerical simulation, a discrete phase model is applied to calculate particle trajectories, and the particle tracking calculation is coupled with the steady-state flow calculation. A user-defined function is developed in the Fluent computational fluid dynamics (CFD) code to implement the settling condition and improve the particle motion predictions. In the experimental work, a back-scattered ultrasonic method is used to measure the velocity field, and the accumulation of particles at the bottom is reproduced by transforming the raw experimental data. The sediment deposition is also recorded photographically, and the trap efficiency is calculated. The CFD and experimental results are compared to estimate the accuracy of the modified settling boundary condition, showing an improvement in the trap efficiency and deposition zone predictions. High water level in the tank corresponds to higher sediment trap efficiency, and sediment deposition type is strongly affected by the water level. Tank length and the presence of cavity alter the sediment deposition zone, and the presence of cavity increases the trap efficiency of tank.

Ab initio investigations of A=8 nuclei: α–α scattering, deformation in 8He, radiative capture of protons on 7Be and 7Li and the X17 boson

We apply the No-Core Shell Model with Continuum (NCSMC) that is capable of describing both bound and unbound states in light nuclei in a unified way with chiral two- and three-nucleon interactions as the only input. The NCSMC can predict structure and dynamics of light nuclei and, by comparing to available experimental data, test the quality of chiral nuclear forces. We discuss applications of NCSMC to the α–α scattering and the structure of 8Be, the p+7Be and p+7Li radiative capture and the production of the hypothetical X17 boson claimed in ATOMKI experiments. The 7Be(p, γ)8B reaction plays a role in Solar nucleosynthesis and Solar neutrino physics and has been subject of numerous experimental investigations. We also highlight our investigation of the neutron rich exotic 8He that has been recently studied experimentally at TRIUMF with an unexpected deformation reported.

Erosion and Transport of Dry Soil Bed by Collisional Granular Flow: Insights From a Combined Experimental–Numerical Investigation

AbstractCollision‐induced stresses on soil beds under granular geophysical flows have been demonstrated to be highly erosive. However, it remains mostly elusive as to how a collisional granular flow erodes and transports soil bed material. This paper presents a combined experimental and numerical investigation into the mechanisms underlying collision‐induced erosion and transport of dry soil beds. A series of flume experiments are conducted where collisional granular flows erode dry sand beds under varied conditions. The experiments are then back‐analyzed using a hybrid continuum–discrete simulator to gain physical insight into the erosion and transport processes. Results show that the key mechanism of collision‐induced erosion and transport is the retexturing of the soil bed surface. This implies that bed morphology, which has often been overlooked in mobility and hazard assessments, has profound effects on erosion and transport potential. Further, contrary to most existing models that assume all the eroded bed volume is carried away by granular flow, it is found that only up to 80% of the eroded material is transported. Also found is that the collisional stresses of the monodisperse grains in this study follow the Pareto distribution in which 80% of differences in the outcomes are due to 20% of causes. This finding suggests that there is measurable certainness in a seemingly random process of coarse grain collisions with an erodible soil bed.

A Novel Framework for Consequence Prediction of Battery Thermal Runaway Failure Hazards

Lithium-ion batteries (LIBs) are widely utilized for energy storage in a broad range of applications, such as handheld electronics, emobility, spaceflight vehicles, etc. Thermal runaway (TR) and subsequent combustion of LIBs represent several significant hazards to consumers, including substantial energy release, jet flames, toxic gases, airborne particulates, and secondary explosions. Numerous experimental investigations in the literature have measured the energy release and chemical composition of off-gasses during LIB TR, but little theoretical work has been completed to this end. The current study focuses on prediction of product chemical composition, flame temperature, and energy release for LIBs undergoing TR failure through implementation of chemical equilibrium analyses (CEA). Theoretical calculations for various LIB electrolyte decomposition and combustion scenarios were compared to data available in the literature. Excellent agreement was observed between predicted and experimental measured heats of combustion for plain LIB electrolytes, indicating the global thermodynamic properties are well captured by the modeling approach. Theoretical product gas production (i.e., moles of gas per mole of electrolyte) and composition were compared to experimentally measured values from accelerated rate calorimetry experiments. The results indicate that general trends are well captured by the CEA modeling approach developed here and that the standard experimental protocols documented within the literature can be improved. Similar theoretical predictions for battery failure experiments (product gas composition and energy release) are also presented. The novel modeling framework presented here can be used in future work to evaluate LIB failure hazards for existing systems and to evaluate the safety of future designs. In addition, this modeling approach provides unique insight into how adjusting global battery chemistry (cathode, electrolyte, etc.) changes the potential hazards produced battery thermal runaway and failure. Figure 1

Numerical simulation and experimental investigation of the laser cladding processes of Ti6Al4V with coaxial shroud protection

Laser cladding with coaxial shroud protection offers the possibility to process reactive metals in an open environment. The numerical analysis was performed on the thermal field and dynamics of molten pool with the aim of clarifying the mechanism of the complex effects of the applied extra shielding gas on the resultant microstructure and surface quality of cladding layers of Ti6Al4V. A three-dimensional (3D) computational fluid dynamics (CFD) model was first developed to investigate the extra shielding gas effect on the molten pool. The simulation shows that the extra shielding gas influences both the surface and internal flow field characteristics of the molten pool. The predicted solidification parameters imply fully columnar microstructure in the entire cladding layer. Comparative analysis was then carried out between the numerical simulation and experiments. The electron backscattering diffraction (EBSD) examination reveals that the high cooling rate due to the extra shielding gas inhibits the formation of grain boundary α phase and simultaneously refines the microstructure. The extra shielding gas reduces the surface roughness of cladding layers, and its bunching effect improves the powder utilization. The multi-track cladding experiments reveal that the extra shielding gas can effectively suppress crack formation with a large overlap ratio. This study provides a better understanding of the effect of extra shielding gas flow on molten pool, which helps control and improve the quality of cladding layers.

Locomotion characteristics of a wheeled vibration-driven robot with an enhanced pantograph-type suspension.

Introduction: The paper considers the improved design of the wheeled vibration-driven robot equipped with an inertial exciter (unbalanced rotor) and enhanced pantograph-type suspension. The primary purpose and objectives of the study are focused on mathematical modeling, computer simulation, and experimental testing of locomotion conditions of the novel robot prototype. The primary scientific novelty of the present research consists in substantiating the possibilities of implementing the enhanced pantograph-type suspension in order to improve the robot's kinematic characteristics, particularly the average translational speed. Methods: The simplified dynamic diagram of the robot's oscillatory system is developed, and the mathematical model describing its locomotion conditions is derived using the Euler-Lagrange differential equations. The numerical modeling is carried out in the Mathematica software with the help of the Runge-Kutta methods. Computer simulation of the robot motion is performed in the SolidWorks Motion software using the variable step integration method (Gear's method). The experimental investigations of the robot prototype operating conditions are conducted at the Vibroengineering Laboratory of Lviv Polytechnic National University using the WitMotion accelerometers and software. The experimental data is processed in the MathCad software. Results and discussion: The obtained results show the time dependencies of the robot body's basic kinematic parameters (accelerations, velocities, displacements) under different operating conditions, particularly the angular frequencies of the unbalanced rotor. The numerical modeling, computer simulation, and experimental investigations present almost similar results: the smallest horizontal speed of about 1mm/s is observed at the supplied voltage of 3.47V when the forced frequency is equal to 500rpm; the largest locomotion speed is approximately 40mm/s at the supplied voltage of 10V and forced frequency of 1,500rpm. The paper may be interesting for designers and researchers of similar vibration-driven robotic systems based on wheeled chassis, and the results may be used while implementing the experimental and industrial prototypes of vibration-driven robots for various purposes, particularly, for inspecting and cleaning the pipelines. Further investigation on the subject of the paper should be focused on analyzing the relations between the power consumption, average translational speed, and working efficiency of the considerer robot under various operating conditions.

Numerical Analysis and Experimental Investigation of High Cycle Fatigue Behavior in Additively Manufactured Ti–6Al–4V Alloy

Additive Manufacturing (AM) of the Ti–6Al–4V alloy has gained significant importance across various industries, including biomedical, aerospace, cellular, and land vehicle applications, due to its numerous benefits. The certification of performance and reliability of AM materials, particularly for critical applications, heavily relies on evaluating fatigue strength. In this study, a numerical analysis based on the finite element method is presented to predict the High Cycle Fatigue (HCF) behavior of AM Ti–6Al–4V alloy. The investigation focuses on exploring the sensitivity of material fatigue life to surface roughness and Ultimate Tensile Strength (UTS). Uniaxial tensile and High Cycle Fatigue (HCF) tests were conducted on Ti–6Al–4V alloy samples extracted from rectangular walls manufactured using the Laser Metal Deposition (LMD) process. The walls were surface machined prior to sample extraction. Porosity and surface roughness measurements were performed on the samples. Numerical simulations of the HCF tests were carried out, considering various surface roughness ranges and UTS values. The numerical results were then compared to experimental data. The findings consistently demonstrated that higher surface roughness led to a shorter fatigue life, while higher UTS values resulted in a longer fatigue life. The numerical solutions aligned with the experimental results, indicating the efficacy of the finite element method in predicting the fatigue behavior of AM Ti–6Al–4V alloy. These insights contribute to a better understanding of the relationship between surface roughness, UTS, and fatigue life of Ti–6Al–4V alloys manufactured by AM.

Numerical simulations, experimental investigation and optimization of hybrid space thermal radiators

Spacecraft thermal management is a critical issue as power requirements for high-capacity satellites and human space flights continue to grow. Radiators play a vital role in heat transportation and act as sinks in this process. This study focuses on the optimization of a novel space thermal radiator. Conventionally, space thermal radiators have parallel tubes. Recent studies have evaluated the performance of serial radiators for heat transportation in spacecraft. In this study, a hybrid radiator that combines the advantages of both parallel and serial radiators is proposed for space applications. Performance analysis through conjugate heat transfer analysis is conducted on hybrid radiators and compared with parallel and serial radiators. Hybrid radiators effectively reduce the impact of micro-meteoroids and orbital debris. By appropriately isolating the leaking tube, hybrid radiators can maintain 95.4% heat rejection even in the event of tube leaks caused by orbital debris impact. Using Taguchi signal-to-noise ratio analysis, the optimal radiator geometry only incurs a 10 Pa pressure drop, compared to the 572 Pa baseline configuration, and has a lower mass of 4.3 kg instead of 6.8 kg. The study also found that when reduction in pressure drop is a priority, increasing tube diameter is crucial, but when mass reduction is important, decreasing fin thickness should be prioritized. The study demonstrates that hybrid radiator is a better alternative to parallel and serial radiators in spacecraft heat transportation process, especially when reduction in mass and pressure drop are equally crucial.