Dynamic response of structural beams undergoing moving loads and thermal strains using finite elements – Part 1

Surface coatings are crucial for improving the thickness distribution by reducing the interfacial friction between the component and forming die during superplastic forming process. In addition, these coatings act as an oxygen barrier to minimise the formation of alpha case. In this paper, the effect of friction was studied with a single-sheet superplastic forming component using finite-element (FE) analysis and validated through experimental trials. Tensile tests of Ti-6Al-4V were conducted at 900° C according to ASTM E2448 standard, and time-hardening creep power law was used to estimate the material parameters for FE simulation. Herein, two cases were studied. Firstly, a uniform friction condition (one frictional constant) for the whole die surface was studied and a pressure cycle using a strain rate control algorithm was derived using Abaqus. Four different friction constants were studied using the pressure cycle. Low, medium and high fiction coefficients were analysed, along with frictionless conditions. A comparison of FE and experimental results indicated that combining a new coating variant and Boron nitride (BN) achieved similar results to that observed with FE simulation with low friction constant, while results with Boron nitride coating correlated with FE simulation with a medium friction constant. Secondly, a varying friction approach was studied wherein the die surface geometry was segmented and assigned heterogeneous coefficient of friction (COF) values. The obtained FE results suggest that varying friction can introduce slight improvement in the thickness distribution for the selected component geometry.

An energy-stable full discretization for the modified elastic flow of closed curves is proposed. This is a gradient flow of a modified elastic energy combining bending and Dirichlet energies. The minimization of Dirichlet energy can lead to improved mesh quality. Gradient flows for both isotropic and anisotropic cases are considered. We derive new evolution equations for the parameterization and curvature vector of curves in arbitrary codimension. The proposed formulation is discretized by a parametric finite element method in space and a first-order implicit scheme in time. We establish the unconditional energy stability for the fully discretized scheme. Additionally, the second-order accuracy of the BDF2 scheme is demonstrated. Numerical examples in two and three dimensions illustrate the efficiency, energy stability, and asymptotic mesh distribution of the method for simulating the modified elastic flow.

This article compares the results of numerical and experimental analysis of the mechanical properties of an optimized 3D-printed beam. The samples were subjected to a four-point bending test, and corresponding numerical models were created at the same time. The beams were printed using 3D printing and their weight was reduced by using an internal spatial grid with variable thickness that gradually increases towards the outer walls. This approach allows for effective optimization of material strength while minimizing raw material consumption during production. One of the key findings is the determination of the ultimate strength between fibers, the mode of failure, and the high agreement between the experimental results and the numerical model using the finite element method. The optimized beam achieved nearly 60% weight reduction while maintaining comparable load-bearing capacity. The knowledge gained opens up new possibilities in the field of materials engineering and also makes a significant contribution to the methodology of developing and optimizing these structures using 3D printing technology.

To address the issue of sound absorption valleys in open-cell aluminum foam and enhance mid-to-high frequency (800–6300 Hz) performance, we developed a novel pore-penetrating 316L stainless steel fiber–aluminum foam (PPFCAF) composite using an infiltration method. The formation mechanism of the pore-penetrating fibers, the resultant pore-structure, and the accompanying sound absorption properties were investigated systematically. The PPFCAF was fabricated using 316L stainless steel fiber–NaCl composites created by an evaporation crystallization process, which ensured the full embedding of fibers within the pore-forming agent, resulting in a three-dimensional fiber-pore interpenetrating network after infiltration and desalination. Experimental results demonstrate that the PPFCAF with a porosity of 82.8% and a main pore size of 0.5 mm achieves a sound absorption valley value of 0.861. An average sound absorption coefficient is 0.880 in the target frequency range, representing significant improvements of 9.8% and 9.9%, respectively, higher than that of the conventional infiltration aluminum foam (CIAF). Acoustic impedance reveal that the incorporated fibers improve the impedance matching between the composite material and air, thereby reducing sound reflection. Finite element simulations further elucidate the underlying mechanisms: the pore-penetrating fibers influence the paths followed by air particles and the internal surface area, thereby increasing the interaction between sound waves and the solid framework. A reduction in the main pore size intensifies the interaction between sound waves and pore walls, resulting in a lower overall reflection coefficient and a decreased reflected sound pressure amplitude (0.502 Pa). In terms of energy dissipation, the combined effects of the fibers and refinement increase the specific surface area, thereby strengthening viscous effects (instantaneous sound velocity up to 46.1 m/s) and thermal effects (temperature field increases to 0.735 K). This synergy leads to a notable rise in the total plane wave power dissipation density, reaching 0.0609 W/m3. Our work provides an effective strategy for designing high-performance composite metal foams for noise control applications.

This paper presents the design and structural analysis of a support system for a 3D printer, developed to improve resin drainage by enabling rotational movement along two axes. Three design variants were created, and after evaluating their performance, the second variant was chosen for its higher torque capacity and potential for future enhancements. This variant showed the most promise in achieving the desired functionality while allowing for further optimization. Finite element analysis (FEA) was utilized to investigate the structural behavior of the support system under loading conditions, ensuring the design remained within the elastic range. The FEA simulations were performed using Beam, Solid, and Shell element types, which provided insights into stress and strain distribution within the structure. This analysis guided the design process, allowing for refinements that improved the structural integrity and load-bearing capacity of the support. Alongside FEA, analytical calculations were performed to assess the bending stress and shear forces on the aluminum profile under three-point bending conditions. These calculations confirmed that the support structure was capable of handling the operational loads while staying within the elastic domain, ensuring reliable performance. This study demonstrates the effectiveness of combining finite element analysis with analytical methods to optimize the design of 3D printer support systems. The results highlight the potential for enhancing the performance and efficiency of additive manufacturing processes through improved structural designs.

This study investigates the performance of 70% alumina refractories on the roof of an Electric Arc Furnace (EAF) in the nickel matte smelting process. The methods used include material characterization through X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD), and Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDX), thermodynamic simulation using FactSage, and thermal stress simulation based on Finite Element Analysis (FEA). The results of the study show a significant decrease in Al₂O₃ content to below 16% in the corrosion zone, as well as an increase in Fe₂O₃ which triggers the formation of corrosive hercynite (FeAl₂O₄) and magnesium spinel (MgAl₂O₄) phases. FactSage simulations confirmed the stability of these phases at temperatures of 1200–1400 °C. FEA results identified maximum stress concentrations in the central zone of the roof, approaching the strength limit of the refractory material. Based on these findings, the proposed mitigation strategies include: optimizing the brick geometry design to reduce stress (most realistic in the short term), increasing the alumina content and decreasing Fe₂O₃ in the refractory material (potentially effective, but requires economic evaluation), and controlling the furnace temperature distribution (most technically challenging). This study provides a comprehensive approach to designing more reliable and durable EAF refractories.

Manual demolition activities in urban environments can generate significant vibrations that propagate to neighboring buildings, potentially affecting occupant comfort and structural integrity, yet limited research exists on vibrations induced by hand-operated demolition tools. This study investigates the dynamic response of a three-story masonry residential building subjected to vibrations from manual demolition work using different tools (small hammer, large hammer, pneumatic hammer, and circular saw). Experimental measurements were conducted using piezoelectric accelerometers positioned across three building levels, while a three-dimensional finite element model was developed in SAP2000 and calibrated against experimental data through modal analysis. The experimental campaign identified dominant vibration frequencies between 11 and 14Hz, corresponding to the first six structural modes of the building. An accurate Finite Element Model is calibrated on the experimental results. The validated numerical procedure, calibrated through experimental modal data, enables the assessment of vibration levels induced by manual demolition activities and facilitates parametric studies for different scenarios, providing a practical tool for structural engineers.

The actin cytoskeleton is remarkably adaptable and multifunctional. It often organizes into nematic bundles such as contractile rings or stress fibers. However, how a uniform and isotropic actin gel self-organizes into dense nematic bundles is not fully understood. Here, using an active gel model accounting for nematic order and density variations, we identify an active patterning mechanism leading to localized dense nematic structures. Linear stability analysis and nonlinear finite element simulations establish the conditions for nematic bundle self-assembly and how active gel parameters control the architecture, orientation, connectivity, and dynamics of self-organized patterns. Finally, we substantiate with discrete network simulations the main requirements for nematic bundle formation according to our theory, namely increased active tension perpendicular to the nematic direction and generalized active forces conjugate to nematic order. Our work portrays actin gels as reconfigurable active materials with a spontaneous tendency to develop patterns of dense nematic bundles.

During metal machining, under certain conditions, vibrations occur, both at the cutting tool, at the workpiece and at the machine tool. The appearance of vibrations during the cutting process is troublesome, because vibrations reduce the durability of cutting tools (especially in tools with inserts). It also increases machine tool wear and worsens the quality of the machined surface (roughness). The problem of vibration is vast and will represent a permanent research topic for tool makers, machine tool builders and process engineers. This paper presents the study and finite element analysis of the vibrations of a cutting tool, a tool used in the longitudinal turning process, both for deburring and finishing operations. The behavior of the tool, the natural frequencies and the elastic deformations that lead to the impairment of the processing precision and the quality of the surface obtained after processing were demined by calculation. We believe that this study is useful both to the manufacturers of cutting tools, but especially to the technological engineers, for the optimization of the process, by avoiding the cutting parameters that lead to resonance with the tool's own frequencies.

A difference finite element method based on the Nitsche-type stabilization for the three-dimensional Stokes–Stokes model

Towards 120° spiral notch pattern, this paper proposes a finite element model to characterize the nonlinear deformation and designs an inconsistent-configuration device to achieve constant-curvature bending. Effects of the notch geometry on bending stiffness are analyzed using the model. By deriving bending stiffness equations and modeling cable friction, the non-constant curvature bending behavior of the device are characterized. A nonuniform pattern is designed to maintain a constant force-to-stiffness ratio, ensuring uniform curvature. The optimized design reduces tip displacement errors to <1.81 mm under constant-curvature assumptions. This work provides a systematic approach to modeling and optimizing notched devices for neurosurgical applications.

Abstract Achieving a uniform current distribution among parallel conductors is essential to prevent local heating and performance degradation in superconducting rotating machines that are used in aircraft to realize high-current operation. Although transposition methods are effective under single-phase excitation, their effectiveness under practical motor conditions remains unclear. This study investigates the current distribution characteristics of three parallel conductors transposed within an armature coil under realistic motor operating conditions involving three-phase excitation and rotor rotation. To this end, we conducted numerical simulations using finite element analysis for evaluating the effect of both the three-phase magnetic field and the rotating magnetic field of the rotor on current distribution. A previously developed transposition configuration for single-phase armature coils was applied to a three-stranded double-pancake winding, and an analysis was conducted. The results revealed that transposition significantly suppressed current imbalance even in the presence of rotor rotation, reducing the deviation from the ideal distribution to within a few percentages. Further, shielding currents induced by the magnetic field of the rotor were identified as a major factor. The effect of the shielding current on the current distribution was substantially mitigated by the transposition design. Experiments were performed in liquid nitrogen using a rotating test system for validating the method, and current distributions were measured using Rogowski coils under both static and rotating conditions. The measured results were in close agreement with the simulation results, confirming that the proposed transposition method was effective even under actual motor operating conditions. These findings confirm that transposition configurations developed under single-phase conditions can be extended to realistic motor environments, providing a robust approach for ensuring current uniformity in multistrand superconducting armature coils.

Abstract In this work, we consider the model of a mass transport problem through polymeric membranes which is important in many applications especially drug delivery. The aim of this paper is to present a more accurate mathematical model to describe this phenomenon. We propose adopting fractional diffusion modeling for the concentration by using spatial fractional-order Riesz derivative. The numerical simulations for studying this phenomenon were carried out using an approach of finite element method and finite difference method. The error analysis and stability condition for this technique are derived. For the order of the fractional derivative, we studied three cases: the constant-order case, the piecewise continuous case, and the time-varying-order case. The results obtained show that using time-varying Riesz fractional derivative yields a more accurate description of the considered problem than both the classical diffusion model reported in the literature and the other fractional derivatives considered.

Neck pain is a highly prevalent condition in the general population, but the addition of helmet loads contributes to the neck pain that 97% of fighter pilots report. The mechanism for neck pain in pilots is unknown; however, there is likely nerve root (NR) dysfunction involved. This study implemented a spinal cord, NRs, and novel foraminal ligaments into the previously validated VIVA OpenHBM. After performing sensitivity analyses and validating added tissues, helmet loads and muscle forces were applied. The results indicate that helmet loads generate compression on NRs that temporarily impair blood flow and impulse propagation in a neutral posture.

Minimally invasive neurosurgical procedures are widely popular for the excision of deep-seated brain tumours and skull-base lesions. However, the limited maneuverability of the instruments due to highly confined routes and spaces is a challenge for the neurosurgeons. Even robotic arm-based interventions are difficult to implement as these procedures typically require frequent tool changes. Therefore, a combination of human dexterity and robotic intervention can be a good alternative. Accordingly, we have developed a dedicated, robotically manipulated hand-held instrument prototype that could easily maneuver in confined surgical environments. The manipulator is a continuum-type robot developed by alternate stacking of stiff and flexible discs, actuated by tendon wires attached to a high torque reduction motor. The manipulator mechanics were simulated using Cosserat-rod theory and validated through finite element analysis, physical experiments with calibrated weights. The manipulator was then integrated with a hand-held operating unit and the functionality was tested in a neuro-endo-trainer, followed by functional validation on a human cadaver head. The simplistic design and compact actuation unit of the prototype exhibited ease of fabrication, enhanced maneuverability in confined spaces and a universal appeal to the surgeons. The prototype demonstrated a maximum tip angle of 42.2° under suspended weight of 2.943N, and successfully supported payloads up to 50g without structural damage. Functional trials in a neuro-endo-trainer and cadaver confirmed superior maneuverability and access compared to rigid instruments, enabling smooth approach to extended or off-axis skull base regions. As such, the presented manipulator meets key design criteria for a practical, hand-held tool in minimally invasive neurosurgery and serves as a platform for future clinical translation.

Managing high energy consumption and thermal energy has become crucial for ensuring a sustainable and stable environment. Recently, passive radiative cooling (PRC) has emerged as an innovative method for reducing environmental energy density without requiring external energy input. This study focused on three wavelength ranges: 2.5-5μm, 8-13μm, and 16-27μm, to optimize net cooling power. We acquired the optical and electrical properties of the materials utilized in this study through density functional theory (DFT). A honeycomb structure was designed as a spectrally selective emitter by using Finite Element Method (FEM) method to enhance radiative properties. We analyzed how geometric parameters affect absorbance and emissivity performance. With the optimal geometry, we achieved a net cooling power of 150.4W/m² under 994W/m² of direct solar irradiation during the day. At night, in the absence of sunlight, the net cooling power increased to 198W/m². The system reached equilibrium temperatures of 256K during the day and 244K at night, assuming an ambient temperature of 300K. Even when considering parasitic convection and conduction, the cooler successfully maintained sub-ambient temperatures. Furthermore, the designed cooler exhibited polarization independence and high emissivity across a wide range of incidence angles (from 0° to 75°).

Abstract To address the challenges of insufficient adhesion, poor obstacle-crossing capability, and low environmental adaptability in traditional tracked wall-climbing robots during operations on vertically curved metal surfaces, this paper proposes a solution for a flexible tracked wall-climbing robot based on permanent magnetic adhesion, which features adaptive curvature capabilities. Firstly, the overall structural design and operational principles of the robot are systematically elaborated, and a mechanical model is established based on its wall motion characteristics. Secondly, to ensure operational stability, critical conditions for slippage and overturning are defined through systematic force analysis, while the adaptive motion principles during obstacle crossing are demonstrated. Building on this foundation, finite element analysis of the magnetic field is conducted on the permanent magnetic adhesion structure, and the influence of magnetic field parameters on adhesion force is systematically explored through magnetic circuit optimization design and parametric simulation of the permanent magnet assembly, ultimately achieving design optimization of the permanent magnet structure. Finally, experimental validation is performed using a physical prototype, confirming the robot's motion flexibility and adaptive capabilities in curved wall environments. The experimental results demonstrate that the designed robot exhibits stable and reliable adhesion, strong load-bearing capacity, and excellent obstacle-crossing performance, providing a viable technical solution for operations in complex metal wall environments.

Crystal plasticity finite element analysis of slip and twinning activities of magnesium alloy in compression with shear

Understanding the three-dimensional biomechanical behavior of the capsuloligamentous complex, considering it as a single sheet of fibrous tissue, is beneficial for assessing patients with limited glenohumeral range of motion in vivo. The aim of this study was to investigate the three-dimensional strain distribution of all capsuloligamentous regions, viewing it as a single sheet of fibrous tissue, during passive glenohumeral motion and to determine which area of the capsuloligamentous structure is essential for a particular glenohumeral motion. Three-dimensional strain changes of the capsuloligamentous complexes of six fresh-frozen cadavers were measured using a stereoimaging technique and finite element analysis. The comparative strain of the capsuloligamentous complex was measured at 0°, 30°, 60°, and 90° of glenohumeral abduction in the scapular plane and from 60° of internal rotation to 60° of external rotation in 15° increments across four regions (i.e., posterior, superior, anterior, and inferior) and 30 subregions. At 0° of abduction, the superior capsule affected only the range from 30° of internal rotation to 30° of external rotation. Only the anterior and posterior capsules affected more than 30° of external and internal rotations, respectively. At 30° of abduction, the posterior capsule primarily affected internal rotation, whereas the anterior capsule primarily affected external rotation. At 60° of abduction, the inferior capsule, especially the anterior subregions, significantly affected internal and external rotations. The anterior capsule affected external rotation to a lesser extent than the inferior capsule. At 90° of abduction, only the inferior capsule primarily affected internal and external rotation. Evaluation of all capsuloligamentous regions as a single continuous sheet of fibrous tissue showed that the comparative strain of the superior and posterior capsular regions during passive glenohumeral rotation is more limited than previously known. The inferior capsular region has a more significant comparative strain during glenohumeral rotational motion than has been documented in previous studies.