Search Results (104)

Modern machining industries require high precision and efficiency in machine tools, where thermal deformations significantly impact accuracy. This study focuses on optimizing the structural parameters of a vertical turning center to minimize thermal displacements affecting machining precision. The optimization process is divided into parametric and topological methodologies. The parametric approach targets three primary objectives: minimizing mass (q₁), maximizing static stiffness (q₂), and reducing thermal displacement (q₃). Multi-criteria optimization techniques, including Pareto-based and scalarization methods, are applied to balance these conflicting factors. Finite Element Analysis (FEA) models assist in evaluating machine stiffness and displacement, with constraints imposed on structural mass and stiffness to maintain performance. Parametric optimization, using iterative computational algorithms such as Genetic Algorithm (GA) and Particle Swarm Optimization (PSO), refines rib and wall thicknesses of the lathe table to achieve displacement reductions. The optimization process successfully lowers displacement at critical measurement points while maintaining structural integrity. Hybrid PSO (hPSO) outperforms other algorithms in achieving optimal parameter sets with minimal computational effort. Topological optimization, based on the Solid Isotropic Microstructure with Penalization (SIMP) method, further enhances structural efficiency by refining material distribution. The iterative process identifies optimal energy flow paths while ensuring compliance with mechanical constraints. A hybrid approach integrating parametric adjustments with topological refinement leads to superior performance, achieving a 43% reduction in displacement at key measurement points compared to the initial design. The final optimized design reduces mass by 1 ton compared to the original model and 2.5 tons compared to the best rib–wall optimization results. The study’s findings establish a foundation for implementing active deformation compensation systems in machine tools, enhancing machining precision. The integration of parametric and topological optimization presents a robust framework for designing machine tool structures with improved thermal stability and structural efficiency. Full article

The rational design of advanced composite gels requires rigorous rheological analysis to decode their flow-deformation mechanisms, a prerequisite for optimizing performance in food and biomedical applications. However, systematic thermal analysis and rheological profiling of Salecan/Sanxan hydrogels remain unexplored, constituting a critical knowledge gap in this field. This study engineered Salecan/Sanxan hydrogels and systematically probed Salecan-dependent rheological and thermal properties. Through Power Law and Herschel–Bulkley model analyses, the hydrogels demonstrated composition-dependent rheological properties: yield stress (4.7–29.2 Pa), η₅₀ (342.6–3011.4 mPa·s), and Arrhenius equation fitting revealed tunable activation energy (14,688.3–30,997.1 J·mol⁻¹). Notably, when the gel was formulated with 3% Sanxan and 2% Salecan at a volume ratio of 1:2, its thermal-decomposition temperature rose by 9%, from 224.4 °C to 245.1 °C. Conversely, a 1:1 mixture of 2% Sanxan and 2% Salecan produced the lowest freezing point recorded (–18.3 °C), an 18% reduction compared with the control (–15.4 °C). These findings demonstrate the tunable rheological and thermal properties of Salecan/Sanxan hydrogels. By establishing that precise modulation of polymer mixing ratios can match the entire processing shear spectrum, this study not only fills a critical knowledge gap but also creates a versatile platform for designing tailor-made foods and biomedical matrices. Full article

For the first time, the kinetics of isothermal curing and thermal degradation of polyethylene glycol maleate (pEGM)–based systems and their composites with mineral fillers were investigated in the presence of a benzoyl peroxide/N,N-Dimethylaniline redox-initiating system. DSC analysis revealed that the curing process at 20 °C can be described by the modified Kamal autocatalytic model; the critical degree of conversion (α_c) decreases with increasing content of the unsaturated polyester pEGM and in the presence of fillers. In particular, for unfilled systems, α_c was 0.77 for pEGM45 and 0.60 for pEGM60. TGA results demonstrated that higher pEGM content and the incorporation of fillers lead to increased thermal stability and residual mass, along with a reduction in the maximum decomposition rate (dTGₘₐₓ). Calculations using the Kissinger–Akahira–Sunose and Friedman methods also confirmed an increase in the activation energy of thermal degradation (E_a): E_KAS was 419 kJ/mol for pEGM45 and 470 kJ/mol for pEGM60, with the highest values observed for pEGM60 systems with fillers (496 kJ/mol for SiO₂ and 514 kJ/mol for CaCO₃). Rheological studies employing three-interval thixotropy tests revealed the onset of thixotropic behavior upon filler addition and an increase in structure recovery after deformation of up to 56%. These findings underscore the potential of pEGM-based systems for low-temperature curing and for the design of composite materials with improved thermal resistance. Full article

Soundproof enclosures are essential components in ultra-high voltage converter transformer equipment. However, conventional designs pose considerable fire risks, as they may impede fire suppression efforts in case of equipment failure. This study adopted a multi-technique experimental strategy to systematically evaluate the influence of flexibilizer content on the thermal and combustion properties of soundproof enclosures. The methodology combined scanning electron microscopy and thermogravimetric analysis, cone calorimetry and thermal deformation tests. Subsequently, the entropy method was applied to quantify comprehensive fire risk based on the experimental data. The results showed that incorporation of a flexibilizer reduced thermal stability, evidenced by a decrease in the initial pyrolysis temperature from 570 K to 505–545 K at a heating rate of 5 K/min. As flexibilizer content increased, the activation energy (E_α) exhibited a pattern of initial decrease, followed by an increase, and then a subsequent decrease, with most samples exhibiting Eα values below 250 kJ/mol. Simultaneously, flexibilizer addition improved critical fire safety parameters, including reduced heat release rate, total heat release, smoke production, CO₂ release rate, mass loss rate, thermal deformation temperatures, and increased CO release rate. The comprehensive fire risk score decreased significantly from 0.2801 to a range of 0.1147–0.2522 after the addition of the flexibilizer. Thus, this study provides a quantitative assessment of fire safety in ultra-high voltage converter transformer equipment through risk evaluation, offering valuable insights for developing safer enclosure materials. Full article

Incorporating Nitinol (NiTi) shape memory alloy (SMA) into concrete structures has gained significant attention in recent years due to its ability to enhance the properties of concrete. This review paper illustrates the history of NiTi SMA and its use in various civil engineering structural applications. A detailed analysis of the existing literature and case studies offers perspectives on the possible applications, benefits, and prospects of utilizing NiTi SMA to reinforce and strengthen elements in concrete structures. The study examined publications on the internal usage of NiTi SMA in concrete and cement-based matrices as an embedded element, including fibers, bars, cables, wires, powder, and strands. In addition, superelastic and shape memory forms of NiTi were considered. It was concluded that the superelasticity of NiTi aided in energy dissipation from impact or seismic events. It also improved the re-centering performance and deformation capacity and reduced residual stresses, strains, and cracks. Conversely, the SMA effect of NiTi helped bridge cracks, recover the original shape, and induced prestressing forces under thermal activation. Full article

The thermal deformation behaviour of a spray-formed 7055 as-forged aluminium alloy was studied using isothermal hot-press tests under different deformation conditions (strain rates of 0.01, 0.1, 1, and 10 s⁻¹, temperatures of 340, 370, 400, 430, and 460 °C). An Arrhenius constitutive model was developed using flow stress data corrected for friction and temperature, yielding a correlation coefficient (R) of 0.9877, an average absolute relative error (AARE) of 4.491%, and a deformation activation energy (Q) of 117.853 kJ/mol. Processing maps integrating instability criteria and power dissipation efficiency identified appropriate processing parameters at 400–460 °C/0.08–0.37 s⁻¹. Furthermore, this study investigated how strain rate and temperature influence microstructural evolution. Microstructural characterization revealed that both dynamic recovery (DRV) and dynamic recrystallization (DRX) occur simultaneously during thermal deformation. At low temperatures (≤400 °C), DRV and continuous dynamic recrystallization (CDRX) dominated; at 430 °C, deformation microstructures and recrystallized grains coexisted, whereas abnormal grain growth prevailed at 460 °C. The prevailing mechanism of dynamic softening was influenced by the applied strain rate. At lower strain rates (≤0.1 s⁻¹), discontinuous dynamic recrystallization (DDRX) was the primary mechanism, whereas CDRX became dominant at higher strain rates (≥1 s⁻¹), and dislocation density gradients developed within adiabatic shear bands at 10 s⁻¹. Full article

It is essential to develop the optimal hot-working process of the (CoCrNi)₉₄Al₃Ti₃ alloy, a recently developed precipitation-hardened medium-entropy alloy with promising mechanical properties, for its industrial application. In this study, the hot workability of the as-forged (CoCrNi)₉₄Al₃Ti₃ alloy was investigated over a temperature range of 1000 °C to 1150 °C and a strain rate ranging from 0.001 to 1 s⁻¹ using a Gleeble-1500D thermal simulation machine of Dynamic Systems Inc., USA. As a result, the constitutive relationship was established, and the hot deformation activation energy was calculated as 433.2 kJ/mol, suggesting its well-defined plastic flow behavior under low-energy-input conditions. Hot-processing maps were constructed to identify the stable hot-working regions. Microstructure analysis revealed that the hot-forged (CoCrNi)₉₄Al₃Ti₃ alloy exhibited continuous dynamic recrystallization (CDRX) behavior under optimal hot-working conditions. Considering the hot-processing maps and DRX characteristics, the optimal hot-working window of hot-forged (CoCrNi)₉₄Al₃Ti₃ alloy was identified as 1100 °C with a strain rate of 0.1 s⁻¹. This work offers valuable guidance for developing high-efficiency forming processes for (CoCrNi)₉₄Al₃Ti₃ medium-entropy alloy. Full article

In this study, we studied the dual role of magnesium on the high-temperature deformation mechanisms and microstructural evolution of high-Mg 5383 aluminum alloys. We developed a quantitative framework to characterize high-temperature flow behavior and constructed 3D processing maps to identify processing instabilities. The results indicate that solid solution strengthening induced by Mg atoms leads to a substantial increase in peak flow stress. The thermal activation energy rises significantly from 182 kJ/mol to 209 kJ/mol at a Mg content of 5 wt.%, which highlights the pronounced solute drag effects on dislocations. Moreover, Mg-modified grain boundary dynamics enhance power dissipation efficiency by 34% (from 35% to 47%). With an increasing Mg content, the processing instability domains expand, thereby shifting the optimal processing parameters towards higher-temperature and lower-strain-rate regions (500 °C/0.05 s⁻¹). The results provide a theoretical foundation for optimizing the thermal processing characteristics and mechanical properties of high-Mg aluminum 5xxx series alloys. Full article

The research investigates the thermal behavior of mixed systems based on natural and artificial cellulose fibers used as precursors for carbon nonwoven materials. Flax and hemp fibers were employed as natural components; they were first chemically treated to remove impurities and enriched with alpha-cellulose. The structure, chemical composition, and mechanical properties of both natural and viscose fibers were studied. It was shown that fiber properties depend on the fiber production process history; natural fibers are characterized by a high content of impurities and exhibit high strength characteristics, whereas viscose fibers have greater deformation properties. The thermal behavior of blended compositions was investigated using TGA and DSC methods across a wide range of component ratios. Carbon yield values at 1000 °C were found to be lower for blended systems containing 10–40% by weight of bast fibers, with carbon yield increasing as the quantity of natural fibers increased. Thus, the composition of the cellulose composite affects carbon yield and thermal processes in the system. Using the Kissinger method, data were obtained on the value of the activation energy of thermal decomposition for various cellulose and composite systems. It was found that natural fiber systems have three-times higher activation energy than viscose fiber systems, indicating their greater thermal stability. Blends of natural and artificial fibers combine the benefits of both precursors, enabling the deliberate regulation of thermal behavior and carbon material yield. This approach opens up prospects for the creation of functional carbon materials used in various high-tech areas, including thermal insulation. Full article

In this paper, the as-cast microstructure, microsegregation, the kinetics of secondary precipitation phase, and thermal deformation behavior in Ta-containing GH4151 alloy (Ta-GH4151) were studied using optical microscope (OM), scanning electron microscope (SEM), electron probe (EPMA), differential scanning calorimetry (DSC), mechanical testing and simulation (MTS) and electron backscattering diffraction (EBSD). The results indicate that Ti, Ta, Nb and Mo are mainly distributed in the interdendritic region and exhibit negative segregation characteristics, while Cr and W are mainly distributed in the dendritic arm region and exhibit positive segregation characteristics. The initial dissolution temperatures for Laves phase, eutectic (γ + γ′) and η phase are 1140–1150 °C, 1150–1160 °C and 1170–1180 °C, respectively. The diffusion activation energies of Nb, Ta and W are 313 kJ/mol, 323 kJ/mol and 345 kJ/mol, respectively. The hot deformation activation energy of Ta-GH4151 alloy after homogenization is 1694.173 kJ/mol. Based on the constitutive equation and hot processing map, the optimum hot deformation temperature and strain rate range are determined to be 1160–1170 °C/0.3–1 s⁻¹. The addition of Ta not only increases the redissolution temperature of the Laves phase, eutectic (γ + γ′) and η phase but also increases the segregation of Nb, Ta and W, diffusion activation energy and homogenization. The results are expected to provide a more comprehensive understanding of the modification and accelerated application of GH4151 alloy. Full article

The hot deformation behaviors and dynamic softening mechanisms of XM-19 super austenitic stainless steel (SASS) were investigated using the isothermal compression test in the temperature range from 1025 to 1250 °C and a compression rate of 0.01–10 s⁻¹. A hot processing map with a strain of 0.9 was constructed, and the analysis results show that the optimal thermal deformation parameters are a temperature range of 1200–1250 °C and a strain rate range of 0.03–0.2 s⁻¹. The thermal activation energy at 0.7 strain is calculated to be 614.3 kJ/mol by developing constitutive equations under various deformation parameters, which is essentially higher than the range of thermal deformation activation energy of typical austenitic stainless steels. At a high temperature of 1250 °C, the synergistic effect of adiabatic heating and increased dislocation density drives the recrystallization fraction to surge from 20% to 78% as the strain rate rises from 0.01 to 10 s⁻¹, while at a fixed strain rate of 0.1 s⁻¹, the increase in deformation temperature from 1025 °C to 1250 °C promotes dynamic recrystallization (DRX), leading to a parallel rise in recrystallization fraction to 25%. The nucleation mechanism of XM-19 SASS is primarily driven by discontinuous dynamic recrystallization (DDRX), with a supporting role of continuous dynamic recrystallization (CDRX). The contribution of CDRX decreases gradually with increasing deformation temperature. Full article

The modification of the layered silicate with a structural type 2:1 montmorillonite by the cationic surfactant hexadecyltrimethylammonium bromide was carried out. The obtained organomontmorillonite was milled for 2–25 min in a high-energy planetary ball mill. The structural and physicochemical characteristics of the modified montmorillonite and the mechanochemically activated montmorillonite were investigated using various methods such as X-ray diffraction, thermal analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and determination of the specific surface area as well as the parameters of the porous structure by the low-temperature adsorption–desorption of nitrogen. The modification of montmorillonite with the quaternary ammonium salt led to a slowdown of deformation and subsequent amorphization of the montmorillonite structure during the high-energy milling. Mechanochemical activation of the modified montmorillonite increased its sorption capacity nine times, with the maximum uranium sorption achieved after mechanochemical treatment for 10 min. Full article

In this paper, constant strain rate compression was carried out by means of an MMS-100 thermal/force simulation tester in a temperature range of 790~940 °C, with a strain rate of 0.01–1 s⁻¹ and a compression volume of 60%. A linear regression method was used to fit the relationship between strain stress, strain rate, and deformation temperature, and the Arrhenius-type constitutive equation of Ti55531 titanium alloy was established; the heat deformation activation energy of Ti55531 titanium alloy was obtained as 211,747.5 kJ·mol⁻¹. A thermal processing map of Ti55531 alloy was established. EBSD results show that after hot compression, the recrystallization volume fraction greatly increased. The original sample recrystallization volume fraction was 23.2%. Under a deformation temperature of 850 degrees Celsius and deformation rate of 0.01, the recrystallization volume fraction rose to 38.5%; after the annealing process, the recrystallization volume fraction further increased to 72.6%. Under the deformation temperature of the thermal compression process, the higher the deformation rate, the larger its recrystallization volume fraction. After annealing, the recrystallization volume fraction further increased. This study can provide a reference and theoretical guidance for the development and optimization of the thermal processing process of Ti55531 titanium alloy. Full article

The hot forming-quenching integrated process (HFQ^®) organically combines the deformation and heat treatment, which can improve the forming performance of aluminum alloy while ensuring the final strength of formed parts. Thermal deformation in HFQ^® has a non-negligible influence on precipitation behavior in subsequent artificial aging treatment and affects the mechanical properties of the formed parts. In this study, the relationship between the precipitation behavior and thermal deformation ratios was investigated. Results indicated that the formation temperatures of η′ and η decreased with an increasing deformation ratio; however, the former decreased more than the latter. The activation energy of η′ precipitation decreased linearly with increasing deformation ratio. Additionally, the phase transition fraction of η′ increased with the deformation ratio, leading to shorter times required to reach equivalent phase transition fractions. Deformation accelerated the phase transition of η′, and greater deformation resulted in a shorter transition time. The aging time required for peak Vickers hardness decreased with increasing deformation ratio, reflecting the promotion of precipitated phase formation and transformation by introduced dislocations. Consequently, peak hardness and yield strength were achieved in shorter aging times. In terms of industrial applications, this discovery offers significant advantages for shortening the production cycle of the hot stamping process and reducing production costs. Full article

Hydrogels like agarose have long been used as sieving media for the electrophoresis-based analysis of biopolymers. During gelation, the individual agarose strands tend to form hydrogen-bond mediated double-helical structures, allowing thermal reversibility and adjustable pore sizes for molecular sieving applications. The addition of tetrahydroxyborate to the agarose matrix results in transitional chemical cross-linking, offering an additional pore size adjusting option. Separation of SDS-proteins during gel electrophoresis is an activated process defined by the interplay between viscosity, gelation/cross-link formation/distortion, and sample conformation. In this paper, the subunits of a therapeutic monoclonal antibody were separated by capillary SDS agarose gel electrophoresis at different temperatures. The viscosity of the separation matrix was also measured at all temperatures. In both instances, Arrhenius plots were used to obtain the activation energy values. It was counterintuitively found that larger SDS–protein complexes required lower activation energies while their low-molecular-weight counterparts needed higher activation energy for their electromigration through the sieving matrix. As a first approximation, we considered this phenomenon the result of the electric force-driven distortion of the millisecond range lifetime reticulations by the larger and consequently more heavily charged electromigrating molecules. In the meantime, the sieving properties of the gel were still maintained, i.e., they allowed for the size-based separation of the sample components, proving the existence of the reticulations. Information about the activation energy sheds light on the possible deformation of the sieving matrix and the solute molecules. In addition, the activation energy requirement study helped in optimizing the separation temperature, e.g., with our sample mixture, the highest resolution was obtained for the high-molecular-weight fragments, i.e., between the non-glycosylated heavy chain and heavy-chain subunits at 25 °C (lower E_a requirement), while 55 °C was optimal for the lower-molecular-weight light chain and non-glycosylated heavy chain pair (lower E_a requirement). Future research directions and possible applications are also proposed. Full article