Using the Cowin-Nunziato model, a coefficient inverse problem for inhomogeneous poroelastic bodies is formulated, and operator equations of the 1st kind for its solution are derived. As an example, an inverse problem for a functionally graded elastic pipe with voids is considered using additional information measured in the domain of transient loading. To solve the direct transient problem, a combined method is used: transition to the Laplace transform space, followed by solution of the boundary value problem using the shooting method and inversion using an expansion in shifted Legendre polynomials. The solution to the direct problem was verified by comparing it with the solution obtained in the finite element package FlexPDE for a homogeneous pipe. The influence of the heterogeneity laws of the Lam & eacute; moduli, coupling modulus, pore diffusion modulus, density, and pore stiffness modulus on the radial displacement was investigated. For reconstruction of physical and mechanical characteristics the iteration approach is applied. Two methods discretization of operator equations (a collocation method and a projection method) are proposed. The initial approximation is defined among the constants as the average of the maximum and minimum values of the material properties. Refinement of physical and mechanical characteristics in projection method was carried out in stages: (1) among constants; (2) linear functions; (3) quadratic functions. Computational experiments were conducted to reconstruct variable properties both at internal points of the pipe and in the class of power functions. A comparative analysis of the effectiveness of the proposed discretization schemes is performed.
External forces generated due to earthquakes, wind, and blasts cause damage to the structure by which its structural integrity gets compromised. A method is to be developed to find the current state of the structure after the damage has occurred. This can be done by finding the natural frequency of the structure using modal analysis. In this study, a two-storey steel frame bolted structure has been studied experimentally on a onedimensional shake table. Results obtained through the experiment have been verified using the numerical study of the same structure. COMSOL Multiphysics was used for additional numerical analysis, and the various eigenfrequencies and mode shapes were identified. Additionally, numerical research was carried out to simulate damages ranging from 10 mm to 20 mm, and the findings indicate that the natural frequencies decrease as the damage increases. Thus, Modal analysis can be used to determine the current state of the structure. For various mode shapes, the experimental and numerical frequency variations are 0.37, 1.61, and 3.16 %, respectively.
This study investigates the mechanical, moisture resistance, and thermal behavior of hybrid flax/hemp/glass fiber reinforced epoxy composites incorporated with TiO2 and SiC nanoparticles. The composites were fabricated using compression molding with different stacking sequences and varying nanofiller contents to evaluate their influence on tensile strength, flexural strength, microhardness, fracture toughness, water absorption, and thermal stability. The results indicate that both fiber stacking configuration and hybrid nanoparticle reinforcement significantly influence the performance of the composites. Among the tested configurations, the Sequence-3 laminate containing 2 wt. % SiC and 3 wt. % TiO2 exhibited the best overall performance. Compared with the baseline composite, this optimized structure demonstrated a 33 % increase in tensile strength, 18 % improvement in flexural strength, 22 % enhancement in microhardness, and 9 % increase in fracture toughness, indicating improved load transfer and crack resistance. In addition, the incorporation of hybrid nanoparticles reduced water absorption by approximately 18 %, enhancing moisture resistance of the composite system. Thermogravimetric analysis further confirmed improved thermal stability, with delayed degradation temperatures attributed to the barrier effect and strong interfacial bonding provided by SiC and TiO2 nanoparticles. Overall, the synergistic interaction between hybrid fibers and nanofillers significantly improves the structural, thermal, and environmental performance of the composites, demonstrating their potential as sustainable lightweight materials for advanced engineering and structural applications.
This study investigates the flexural behavior of mortars modified with recycled polyethylene terephthalate through numerical simulations developed in SolidWorks Simulation using a linear dynamic approach. Prismatic specimens measuring 40 & times; 40 & times; 160 mm3 with recycled polyethylene terephthalate contents of 10 and 20 % were evaluated under three temperature levels (20, 150, and 350 degrees C) and two curing conditions: ambient and water curing. A linear dynamic finite element model was developed in SolidWorks Simulation to reproduce the bending response and analyze the temporal evolution of Von Mises stresses, principal stresses, and stress distribution patterns. The numerical model incorporated experimentally determined mechanical properties and breaking loads as input parameters. The results indicate that increasing recycled polyethylene terephthalate content reduces the stiffness and load-bearing capacity of the mortar, particularly at elevated temperatures, due to the thermal softening of the polymer and the weakening of the interfacial transition zone. Water curing enhances mechanical performance by promoting matrix hydration and improving the capacity for stress redistribution, thereby mitigating the adverse effects of thermal exposure. The numerical simulations showed strong agreement with experimental observations and successfully captured the evolution of stress localization and failure mechanisms under different thermal and curing conditions. These findings highlight the combined influence of recycled polyethylene terephthalate content, curing regime, and temperature on the structural performance of modified mortars and confirm the suitability of linear dynamic finite element analysis for investigating bending behavior in polymer-modified cementitious materials.
X-ray diffraction and temperature-dependent dielectric measurements were used to examine the structural and dielectric characteristics of Bi2Te2.8Se0.2, a promising thermoelectric material. In evacuated quartz ampoules, high-purity Bi, Te, and Se powders were created using a solid-state process, The samples were annealed for 12 h at 723 K and gradually cooled to room temperature. A highly crystalline rhombohedral structure (space group R3m) with little lattice distortion (microstrain similar to 3.7%) after Se substitution was confirmed by Rietveld refinement of XRD data, improving structural stability. Because Se has a larger atomic radius than pure Bi2Te3, the unit cell volume increased slightly. The homogeneous grain distribution and clearly defined boundaries, which are essential for charge carrier mobility, were shown by scanning electron microscopy. At about 10 Hz, dielectric loss (tan delta) showed a Debye-type peaks signifying the greatest amount of energy released by polarization processes. At the peak frequency, the imaginary electric modulus verified relaxation dynamics with relaxation time tau = 0.016 s. The dielectric constant epsilon' rose gradually (by around 20%) at higher temperatures, indicating better polarizability for thermoelectric applications. In comparison to undoped versions, this work demonstrates the originality of Se-doping in Bi2Te3 for adjustable dielectric characteristics, attaining better efficiency (potential ZT > 1.2) with reduced synthesis costs. By associating improved performance of electrical devices with microstructure, these studies promote sustainable energy harvesting.
The preparation and spectroscopic investigation of Sm2O3 doped ZnF2-PbO-B2O3 glasses. XRD patterns confirmed their amorphous nature are reported. From measured densities, various physical parameters - including molar volume, optical band gap, refractive index, electronic polarizability and optical basicity were systematically evaluated and presented. Optical absorption spectra show well defined Sm3+ transitions from H-6(5/2)-(6)F(J )where levels. The optical band gaps are found to be minimal for the glass containing 2.0 mol. % Sm2O3. Judd-Ofelt analysis yielded Omega(2 )> Omega(4 )> Omega(6) with bonding parameter delta highest at 2.0 mol. % Sm2O3, indicating a less covalent environment. Overall, the linear variation of physical and optical properties reflects the compositional role of Sm2O3. These results provide useful for potential laser-host applications.
This study focused on the characterization of a complex microstructure in 17-4 PH martensitic steel produced during laser powder bed fusion. Due to the specific nature of the LPBF process, the additive material undergoes an extremely high cooling rate (similar to 10(6) K/s) and pronounced thermal cycling. This usually gives rise to the complex microstructures consisting of delta-ferrite, austenite, and martensite. In this work, a two-step approach was developed for the partitioning of the delta-ferrite and martensite phases. The elaborated method was based on the electron backscatter diffraction technique and involved a two-factor filtration of the electron backscatter diffraction data using the distinct differences between the delta-ferrite and martensite in stored energy and grain size. From experimental observations, it was shown that the proposed technique was highly effective for an analysis of the complex microstructures produced during LPBF of 17-4 PH martensitic steel.
An effective powder metallurgy route has been used to develop new Al/B4C (0, 0.5, and 1 wt. %) nanocomposites. Following 4 h of optimized mechanical milling, particle size measurements verified for the pure Al, Al/B4C (0.5 wt. %), and Al/B4C (1 wt. %) samples as 65, 54, and 51 nm, respectively and these values are well corroborated to the crystal size measurement by XRD for the respective samples. Then the compacted (at 200 MPa) samples were sintered at an argon atmosphere at 550 degrees C for 3 h. Because of the homogeneous dispersion of 1 wt. % B4C in Al, the intensity of the Al peaks is significantly reduced in the XRD pattern of Al/1 wt. % B4C composite, which indicates the proper composite formation between Al and B4C. It is marked that the reinforcement of B4C enhanced the morphology of pure Al. Reinforcement of only 1 wt. % B4C in Al was found to enhance its microhardness value from 45 to 112 VHN (about 148 % increment).
This study investigates mechanical stresses induced by a unipolar sinusoidal pulse in a hollow cylindrical conductor, which serves as a key element of the base part of a quasi-force-free configuration pulsed magnet. The aim of the work is to assess transient mechanical effects not accounted for by static models. The applied method determines the system's natural frequencies and solves the dynamic axisymmetric problem of elasticity theory using Laplace transforms. The results include the calculated spectrum of natural frequencies; it is shown that the stress response exhibits quasistatic behavior for millisecond-duration pulses, whereas dangerous stress magnification requires microsecond pulses which are consistent with the single-degree-of-freedom model predictions. In conclusion, the adequacy of static models for designing magnets with millisecond-range pulses is confirmed, and the development of a methodology for analyzing complex multilayer magnets is proposed.
Despite all the advantages of shape memory alloy-based actuators, their widespread adoption is hampered by a significant drawback: a gradual decline in performance with repeated actuation. The ways to overcome this drawback are explored. Based on microstructural modeling, the influence of the degree of completion of the reverse martensitic transformation on the operational stability of a torsion actuator with a working body made of a TiNi alloy was investigated. The existence of a critical transformation threshold (similar to 75 %) has been identified: exceeding it leads to significant loss of work output, while limiting the transformation to this level ensures practical stabilization of the working cycle parameters. A compromise in the influence of the transformation degree was revealed: reducing it improves the stability of the actuator parameters but reduces the work output per cycle. Based on the obtained results, criteria for selection of an optimal operating mode for actuators intended for long-term cyclic operation were formulated.
While extensive research has focused on the sound absorption properties of concrete, the effect of external acoustic vibration loads on its hydration process, mechanical performance, and microstructure remains a significant scientific gap. This study investigates the influence of applying acoustic vibrations at varying frequency ranges during the critical hydration period. A conventional concrete mixture was subjected to acoustic vibrations across five frequency ranges for 24 h during hydration, using a setup with two loudspeakers at constant sound intensity. A control sample was cured without any vibrations. The mechanical performance was evaluated through compressive and tensile strength tests at 7, 14, and 28 days Microstructural analysis was conducted using scanning electron microscopy on selected samples. The results demonstrated a clear negative impact on mechanical properties. The control sample achieved the highest compressive (37.2 MPa) and tensile (3.6 MPa) strengths at 28 days. The application of acoustic vibrations generally reduced strength, with the reduction being more severe at higher frequencies. The sample E (104-2 & centerdot;104 Hz) showed the most significant decline, with compressive and tensile strengths 42.4 % and 22.2 % lower than the control, respectively. However, the effect was found to be frequency-dependent. Sample C (103-5 & centerdot;103 Hz) exhibited a relatively smaller reduction in strength compared to other treated samples, suggesting a less detrimental impact within this specific range. The study concludes that external acoustic vibrations during hydration disrupt the microstructure formation, leading to a decrease in the mechanical strength of concrete. No beneficial effects were observed within the tested parameters.
The aim of the study is to develop and perform a preliminary evaluation of a method for diagnosing and locating internal defects in multilayer polymer composite materials using non-destructive testing data. A method combining topological data analysis and graph-signal processing is proposed. To demonstrate the potential feasibility of this method, an analysis of synthetic ultrasonic signals was conducted. A set of 81 ultrasonic signals, representing various locations of internal defects in the composite material, was used. Topological data analysis enabled the identification of informative topological features and distinguished defective from defect-free cases with a silhouette score of 0.471. The results show the potential of using topological data analysis to automate the structural monitoring of internal defects in multilayer polymer composite materials.
A heat exchanger is a device that facilitates the transfer of energy between two fluids through a solid barrier. Simulations were performed in a turbulent flow regime to investigate the two-dimensional forced convective heat transfer of the nanofluid water / Al2O3 within a counter-flow heat exchanger. This study is numerical and was conducted using a single-phase approach with constant thermophysical properties. Conduction through the interface was taken into account in the computations. The results unequivocally showed an improvement in the overall coefficient of heat transfer depending on the Reynolds number along with the type of fluid. The use of nanofluid significantly increases total heat transfer in contrast to the pure base fluid; however, this is accompanied by an increase in friction coefficients, leading to higher pumping costs.
Theoretical model is suggested which describes the micromechanism of lattice dislocations emission from triple junctions of amorphous intercrystalline layers with pores and liquid-like inclusions in high-temperature ceramics. Within the model, the plastic deformation in ceramics under elevated temperatures is realized through the emission of lattice dislocations from triple junctions of grain boundaries and the subsequent glide of the emitted dislocations in the grain interior. In the exemplary case of high-temperature alpha-Al2O3 ceramics, a comparative analysis of the critical stresses for the emission of the lattice dislocations, and for their glide along the prismatic and basal slip planes in the grain interior depending on the deformation temperature was carried out in a wide temperature range from 300 to 1500 K. It is shown that the critical stress for the emission of the lattice dislocations decreases with both an increase in the length of the liquid-like inclusion and the deformation temperature, and increases with increasing the pore size.
The performance of CVD-coated carbide inserts (TiCN/Al2O3) in hard turning AISI 4340 steel at cutting speeds of 60, 95, 180, and 250 m/min, under both dry and wet conditions are investigated. The goals were to evaluate tool wear, surface roughness, and wear mechanisms over different machining conditions. Surface roughness Ra value was noticed, and it dropped to Ra = 0.30 & micro;m at 180 m/min but increased at 250 m/min due to vibration, edge instability, and wear. Flank wear rose with cutting speed: 186 & micro;m at 60 m/min, 265 & micro;m at 180 m/min, 542 & micro;m at 250 m/min (dry), and 692 & micro;m (wet), exceeding ISO tool life (VB = 300 & micro;m) due to edge breakage, flaking, and adhesion. The examination of the tool surface by SEM and EDS revealed abrasion and slight coating delamination at low speeds, adhesion and oxidation at intermediate speeds, and catastrophic tool failure at high speeds.
The linear stability of electroconvection in a horizontally oriented, thermally unstable dielectric fluid layer saturated with a Darcy porous medium and influenced by couple-stress effects are investigated. The system is subjected to a sinusoidally time-varying electric potential applied at the boundaries. The novelty of this work lies in the combined effects of couple stresses, electric field modulation, and Darcy-porous medium, an area not extensively explored in the existing literature. Using the Boussinesq approximation and a regular perturbation technique, we deal with the governing eigenvalue problem and analyze the critical conditions for the onset of convection. The analysis reveals that electric field modulation can exert either a stabilizing or destabilizing influence depending on the modulation frequency and material parameters. At low frequencies, the destabilizing role of the electric Rayleigh number becomes more pronounced, while couple stress effects contribute to system's stabilization. Additionally, the Vadasz number significantly modifies the stability behavior, enhancing the effects of modulation at high frequencies. Our findings highlight the potential of electric field modulation as a viable mechanism for controlling therma l instability in particle-laden dielectric fluids confined within porous structures. The results provide new insights into electrohydrodynamic flow control in engineering systems involving smart fluids and porous media.
Three modifier oxides, MgO, ZnO, and CdO, were mixed with 1.0 mol % of Thulium-doped lead arsenate glasses and were synthesized by the usage of melt-quenching technique. XRD patterns clearly show the evidence that samples are amorphous and had been supported with the aid of using the lack of distinct peaks. Various functional physical parameters such as molar volume, oxygen packing density (OPD), Tm3+ ion concentration, mean Tm3+ ion separation, polaron radius are evaluated by using experimentally measured densities and refractive indices. The optical absorption spectra of PbO-MO (M = Mg, Zn, Cd)-As2O3:Tm2O3 glass system have been studied. Through the application of least square fitting analysis, the J-O phenomenological parameters (02, 04, 06) for the three glass systems have been calculated.
The joining of dissimilar materials such as aluminium and steel is of growing importance in modern manufacturing, owing to the demand for lightweight structures with superior mechanical performance. This study investigates the influence of rotational speed on key thermo-mechanical performance measures during dissimilar friction stir lap welding of aluminium alloy-6061 and stainless steel-304. Using finite volume method, numerical simulations were performed to quantify maximum weld interface temperature, maximum weld interface velocity, minimum weld interface viscosity, and tool-workpiece interface torque over a rotational speed range of 200-2200 rpm. Results reveal that maximum weld interface temperature rise steeply up to about 1000 rpm and then plateau due to thermal equilibrium. maximum weld interface velocity increases almost linearly with rotational speed, indicating improved interfacial shear and material mixing. In contrast, minimum weld interface viscosity and tool-workpiece interface torque decrease markedly as rotational speed increases, reflecting enhanced thermal softening and reduced resistance to tool motion. Intermediate rotational speed values (approximate to 600-1200 rpm) provide an optimal balance of heat generation, material plasticization and torque, minimising the risk of excessive intermetallic compound growth or welding defects. The findings establish a physics-based framework for selecting process parameters that enhance joint integrity and efficiency in dissimilar friction stir lap welding of AA6061-SS304.
Shape memory alloys are promising for vibration protection systems but their long-term performance is challenged by functional fatigue due to microplastic deformation. A previously developed microstructural model that explicitly accounts for the evolution of microplastic deformation is utilized in the research to investigate the influence of this phenomenon. A one-dimensional oscillatory system with a payload isolated by two TiNi alloy springs is investigated. Numericalsimulations compare the device's response in austenitic and martensitic states, with and without microplasticity, under harmonic excitation. The results confirm that microplastic deformation significantly alters the dynamic characteristics of the system, highlighting the necessity of its inclusion for accurate performance prediction. Furthermore, the analysis demonstrates the superior performance of the shape memory alloy system compared to linear elastic counterparts, showing its inherent ability to mitigate resonance across a frequency range.
The optical resistance and geometric parameters of the damaged region under the action of laser radiation on bulk beta-Ga2O3 crystal were studied and calculated depending on the power and frequency of laser irradiation. The sample of the crystal for the study was grown by the Czochralski method and prepared by method of cleaving along the (100) plane. The optical resistance was calculated by the Liu method using the laser irradiation and ablation parameters. The experiment determined the threshold for laser damage under pulses of 1030 nm wavelength and 224 fs duration; with a beam spot size of 9.6 mu m. The threshold energy density varied from 25.99 to 16.29 J/cm2 with pulse numbers varying from 1 to 20,000. The threshold power density of incident radiation ranged from 11.6 to 7.3 GW/cm2.
