Bending and buckling deformations of very thin beams with curved cross-sections are discussed. Nonconvex strain-energy density functions are considered, and the critical loads and corresponding critical conditions are defined. The Euler-Lagrange equation with Weierstrass-Erdmann corner conditions is acceptable for globally stable deformations. The deformations are defined in the context of globally stable equilibrium deformations. Regions of low and high strain are revealed, separated by a discontinuity in the curvature of the elastic curve. Since the curvature is almost zero in one section, when combined with the other section, the beam will be treated as two separate sections. The one remaining is undeformed, and the other is deformed with constant curvature. Those phenomena are easily observed in the metallic measuring bands.
In this article, we focus on the evolution of numerical solutions of degenerate parabolic hyperbolic equations in one spatial dimension with boundary conditions. Under what are known as "containment" assumptions on the data, numerical simulations are presented in order to better understand these assumptions on the evolution of the solutions.
This study focuses on the analysis and optimization of technology parameters for the Nanofluid Minimum Quantity Lubricationmethod in the hard turning of 90CrSi steel. The effects of Al₂O₃ nanoparticle concentration (NC), air pressure (p) and air flow rate (Q) on the active cutting force (Fa), passive cutting force (Fp), and specific cutting force (Pc−c) were analyzed by an experimental study. The results showed that NC&p were the factors that greatly affected Fa and Pc−c. Fa and Pc−c reached small values at low concentrations and medium pressure levels (about 5.2 Bar). In contrast, Fp is strongly influenced by the interaction between factors and reached a minimum value at 4.0 Bar. Furthermorea multi-objective optimization method was used to find a compromise solution. The overall optimal parameters proposed were: NC≈0.79%, p≈4.97 Bar, and Q≈205.6 l/min. This result provides suitable technological parameters, while also improving cutting efficiency and machining accuracy in real-world manufacturing applications.
The study analyzes the nonlinear dynamics of shallow drill strings under seismic activity in a geological environment. The main objective is to determine the impact of seismic wave influence on the oscillatory process by identifying the dynamic response to types and intensities of seismic excitation, considering the presence of finite deformations. Based on Hamilton principle, a nonlinear mathematical model for the spatial motion of the drill string was developed. A key point was the inclusion of seismic effects in the kinetic energy of the system, which is achieved by accounting for the displacement of the wellbore relative to the global coordinate system. This methodological approach provided description of the influence of dynamic ground mass displacements on the inertial parameters of the system. The research results indicate the transition of the drill string to quasi-periodic oscillation modes, which increase the unpredictability of its dynamics, the risks of resonant vibrations.
The requirement to switch out conventional shields made of hazardous or energy-intensive materials with ones made of biodegradable and environmentally friendly materials. Jute and palm fiber are cheap, readily available, and renewable resources, especially in developing countries. Natural fiber composites are ideal for applications where weight is a critical factor since they are typically thinner than traditional materials (such as portable shielding or aerospace). In this paper, the gamma radiation attenuation properties of locally available materials in Bangladesh, including untreated and treated jute fiber, untreated and treated oil palm pressed fiber (OPPFF), and beeswax, are discussed as potential alternatives to lead for radiation shielding. Using Geant4, a Monte Carlo simulation tool, the study models particle transport through matter. Gamma radioisotopes with photon energies ranging from 0.1 to 20 MeV were used to simulate the transport of 1,000,000 particles through the materials. The linear attenuation coefficient (μ), mass attenuation coefficient (μm), and half-value layer (HVL), tenth-value layer (TVL), and the mean free path were calculated for each material, and the results were validated against the XCOM values. This study explores the possibilities of readily available, inexpensive, and biodegradable natural materials- beeswax, jute, and palm fiber- as eco-friendly substitutes for gamma radiation shielding. Because of their significant concentration of low-Z elements (carbon, hydrogen, and oxygen), the GEANT4 simulation results verify that jute, palm fiber, and beeswax have measurable gamma radiation attenuation capabilities, mostly through Compton scattering. In nuclear medicine clinics or PET/CT facilities, the sustainable composite materials- jute and palm fibers embedded in a beeswax matrix, perhaps with a tiny amount of non-toxic bismuth oxide (Bi2O3) filler- can be used to create movable secondary radiation shielding barriers.
This paper presents the results of the analysis of the dynamic response of a single-degree-of-freedom system comprising a mass and a fractional derivative Kelvin-Voigt element. Using the explicit time difference scheme both for fractional and traditional derivatives, the equation of motion for the system is derived from interior nodes. The forced excitation problem is solved and the results are compared with the conventional derivative case. Furthermore, spectral analysis of mass oscillations is carried out and characteristic frequencies are discussed.
Dentin sensitivity and the success of dental restorations depend on microscopic parameters such as dentin tubule diameter. This study proposes an approach beyond traditional fixed averages in analyzing tubule diameter changes. A dynamic average model (Arithmetic, Geometric, Harmonic) that accounts for outgoing and incoming new tubule populations is adapted to dentin morphology. It is demonstrated how the effective diameter value from these dynamic averages creates an exponential effect (r4) on dentinal fluid flow rate (Q) according to Hagen-Poiseuille law. Mathematical analysis reveals that small increases in tubule diameter (Δr) cause a larger increase (∼ 16Δr) in flow rate than expected. A specific increase in tubule diameter leads to approximately a 3.16-fold increase in flow rate. This study provides a theoretical mathematical framework for predicting macroscopic outcomes of micro-morphological changes in dental practice, establishing a quantitative hypothesis requiring future experimental validation.
Design for low-energy consumption is certainly not a new research field, yet it remains one of the most challenging. The synthesis of mechanisms with minimum-effort motions is one of the most promising areas. The aim of this study is to develop a new design technique to reduce the power consumption of actuators in mechanisms with a single degree of freedom. To achieve this, the prescribed variable speed of the input link is used. By controlling the movement of the input link with a prescribed velocity - defined to maintain constant kinetic energy in the mechanism—the input torque due to inertial effects is canceled. The originality of this approach lies in the fact that the mechanism is designed using traditional methods, while the cancellation of the actuating torque is achieved solely through optimal motion control of the input link. The effectiveness of the proposed solution is illustrated through CAD simulations.
The article highlights the shortcomings of the measuring systems used in rotary drilling today. In the course of analyzing the existing developments and research in the field of monitoring and controlling of the dynamic load on the bit, it was concluded that there are no measuring systems that provide an objective assessment of the amplitude of longitudinal vibrations. Mathematical models describing the dynamics of rotary drilling of wells were analyzed and the need to determine the amplitude for an objective assessment of the dynamic component of the actual load on the bit during drilling was established. The dependencies describing the behavior of compressible fluids during impact are considered. A methodology for measuring the amplitude of longitudinal vibrations during well drilling is proposed, and a laboratory stand is developed for adjusting and confirming the proposed methodology.
The study presents a comprehensive global sensitivity investigation focusing on the failure probability in torsion-loaded thin-walled steel members with uncertainties in material, geometric, and loading parameters. Two distinct sensitivity measures are scrutinised: one formulated through variance analysis of a binary failure outcome and the other based on discrete entropy. Total-effect indices, encompassing all interaction orders, are employed to assess variable importance. The results indicate that the long-term variable load significantly influences the uncertainty in structural reliability, while material and geometric parameters play a secondary role. The entropy-based measure accentuates the distinction between dominant and less influential inputs, while the variance-based approach captures a broader sensitivity structure. The findings underscore the impact of the selected sensitivity metric on input ranking and its implications for reliability assessment.
The automobile drive shaft (propeller shaft assembly) is an important component of the power transmission system, moving continuously during operation. This article studies the influence of dynamic parameters on the durability of the automobile drive shaft, focusing on the geometric factor of shaft length L (mm) affecting the durability, evaluated through deformation ε (mm), displacement Df (mm/m), and torsion angle θ (rad). The main assumptions of the study include that the shaft lies in a vertical plane passing through the vehicle's center of gravity, which is a longitudinally symmetrical plane, ignoring manufacturing and assembly errors, friction at joints, and deformation of related parts. Applying Matlab Mupad and Simulink and Ansys Workbench software to investigate some dynamic parameters of 2 drive shaft configurations: Case 1 with length L1 = 1300 mm, shaft body thickness b1 = 6 mm (L1 = 1300 mm × 6 mm) and case 2 with length L2 = 1450 mm, shaft body thickness b2 = 6 mm (L2 = 1450 mm x 6mm). The results show that for the short shaft (L1): total displacement Df1 =518.435 mm/m, twist angle θ1 =500 (rad) and for the long shaft (L2) the total displacement Df2 =875.35 mm/m and the twist angle θ2 =973.6 rad and the deformation in all directions are also larger for the long shaft (L2), thereby directly affecting the strength of the shaft. These results provide an important scientific basis for optimizing the design of drive shafts, increasing strength and reducing vibration in light vehicles.
To address the multi-objective optimization of density and microhardness in 316L stainless steel formed parts produced by selective laser melting (SLM) technology, this study employs an orthogonal experiment combined with genetic algorithms. By designing a three-factor, three-level orthogonal experiment, the effects of laser power, scanning speed, and scanning spacing on the density and microhardness of the formed parts were analyzed. The significance of each parameter was determined using the range analysis method. Based on the experimental data, a cubic polynomial regression equation was established as the fitness function, and an optimization model aimed at achieving high density and high microhardness was constructed. The Pareto optimal solution set was found using genetic algorithms. The results indicate that laser power has the most significant impact on both indicators. The optimized parameter combination (scanning speed 640mm/s to 650mm/s, laser power 190 W, scanning spacing 0.08 mm) achieves a density of 97.26% to 97.78% and a microhardness of 250.6 HV to 251.6 HV, showing a significant improvement over the orthogonal experiment results. This validates the effectiveness of genetic algorithms in multi-objective optimization of SLM forming parameters.
This study presents the development of a high-fidelity coupled structural–acoustic finite element model of the Piaggio P.180 passenger cabin. The work aims to predict interior noise in the low- to mid-frequency range. To reduce computational cost, the fuselage was modeled using two-dimensional shell elements and one-dimensional beam elements. A detailed modal analysis accurately captured the cabin’s resonance behavior: the first three structural modes showed good agreement with experimental data. Finally, harmonic response analyses were performed to evaluate the noise reduction through the airframe up to approximately 110 Hz.
With the rapid advancement of autonomous driving technology, the mechanical structure of vehicles has emerged as a critical factor influencing driving stability. This study systematically analyzes the impact of mechanical structure improvements—focusing on chassis, suspension, and body systems—on the dynamic stability of autonomous vehicles. Through theoretical models, comparison of constructive criteria, and trials of numerous research studies, the main limitations of traditional tasks have been identified as sub-optimal weight distribution and insufficient real-time adaptation. Improvement plans include lightweight underlayer construction (weight reduction of 25.6%), adaptive suspension technology (vertical speed reduction of 39.5%), and increased torque (increase of 25.4%). Experimental data show that these changes reduce lateral turning residues by 44.4% and reduce turning speed deviations by 46.7% on wet roads, greatly improving steering accuracy and resistance to disturbances. The results highlight the interaction between mechanical construction optimization and autonomous control systems and provide a technical framework for increasing the reliability of next-generation autonomous vehicles.
In this paper, the anomalous filtration of a homogeneous fluid in a homogeneous porous medium is considered. A model of anomalous fluid filtration, composed using the fractional differentiation apparatus, is then numerically analyzed. Problems with constant, exponential, and sinusoidal boundary conditions are considered. The influence of the anomaly on the distribution of the pressure field and filtration velocity is estimated.
In this paper, a computational study is presented to analyze the structural behaviour of solid materials undergoing inelastic strains when they are subject to various loading rates. An implicit integration algorithm is applied for the mechanical simulation of solids that exhibit plastic deformations. A numerical procedure is discussed that is useful to be applied to different types of constitutive models by suitable specialization of the proper flow function. Numerical algorithms are implemented, and computational examples are illustrated by denoting the effectiveness of the adopted numerical procedure.
The plastic deformation of a thin-walled circular cylinder is considered for a specified sequence of torsion and tension. The case was originally intended for contrasting in general terms kinematic hardening with the isotropic hardening model. With the present account the analysis is accomplished presenting the closed-form solution for a linear yield stress and exploring approximations. In addition to the direct analytic treatment iterative procedures, numerical and successive functional update are investigated.
In the present paper, forced nonlinear vibrations of the Uflyand-Mindlin type plate subjected to the action of compressive harmonic loading are investigated for the case when damping forces are described by the fractional derivative Kelvin-Voigt model. The equations of motion are represented by a set of five nonlinear differential equations involving two in-plane displacements, deflection, and two angles of rotation, considering rotary inertia and shear deformations. The solution is constructed by the fractional derivative expansion method, which is the generalization of the method of multiple time scales usually used for problems with nonlinear differential equations of integer order. The simultaneous internal combinational and primary resonance case has been examined, and governing nonlinear differential equations have been derived. Numerical studies have been carried out for different combinations of plate parameters, and the influence of the fractional parameter, i.e., order of the fractional derivative, has been revealed.
This work presents a methodology for the design of simply supported wooden beams under both room temperature and fire conditions, with a uniformly distributed load. Forty-eight different configurations of wooden beams will be studied. All results were performed according to Eurocode 5, Parts 1-1 and 1-2. In this work, the load capability will be analysed according to the standards and compared with the elastic load of beam theory. The wooden beams studied will be made of glulam GL28H. Different exponential equations will be determined as representative of different beam geometries and loading conditions, which allows easy determination of the maximum load capability, rather than the standard methods, which are normally conservative and appropriate for use in design purposes with safety.
A bolted assembly composed of two metallic parts joined directly by a bolt is studied. The bolted joint is clamped-free and is subjected to a transient load in the longitudinal direction. The transient load is an impact force and is applied onto the free part. A nonlinear dynamic model is used to analyze the bolted joint dynamic response, accounting for the clamped and free parts contact interface. First, the differential equations resulting from the nonlinear model are solved using the Euler and the Newmark methods, to determine the joint dynamic response in displacement, velocity, and acceleration. Second, the effects of the bolted parts specifications on the joint dynamic response are examined, in terms of mass, stiffness, and damping. Third, the effect of the bolting stress on the joint dynamic response is investigated, and the effect of the applied transient force on the joint dynamic response is explored. All the bolted assembly parameters are then considered. The obtained results help to analyze and to predict bolted joints dynamic response, under transient longitudinal load, and for different design conditions, using simple but effective tools. They especially guide in setting the bolted joint parameters according to the desired dynamic behavior.
