Search Results (93)

The cyclic hardening characteristics of soil hold significant importance for understanding its performance, and the evolution of the deformation modulus serves as a crucial indicator of the hardening properties. Deformations can be classified into elastic and plastic deformations and expressed in terms of modulus; however, their roles in the cyclic hardening process remain unclear. In this study, the elastic and plastic moduli were separated using the hyperbolic evolutionary model, which characterized the evolutionary properties of both to reflect the cyclic hardening process. A series of cyclic triaxial shear tests was conducted utilizing ISO sand and emery as test materials. A hyperbolic evolution model relating the equivalent modulus to the number of cycles was established, and the effect of various test conditions on the elastic modulus is discussed. The results indicate that: (1) the relationship between the equivalent modulus and the number of cycles is hyperbolic; and (2) the parameters k and b of the hyperbolic evolution model correspond to the elastic and plastic moduli, allowing for the separation of the evolution of both from that of the deformation modulus. The hyperbolic evolution model of the equivalent modulus proposed in this paper offers new insight into the cyclic hardening properties of sand. Full article

This study investigates the impact of zirconium substitution on the structural, elastic and magnetic properties of CoCr₂O₄ nanoparticles. A series of CoCr_2−xZr_xO₄ nanoparticles, x = 0.00, 0.05, 0.10, 0.15 and 0.20, are synthesized via the co-precipitation method. X-ray diffraction (XRD) patterns affirm the formation of single-phase cubic structure with the space group Fd3m. Special attention is given to accurately calculating the average crystallite size (D) and lattice parameter (a) using Williamson–Hall (W–H) analysis and the Nelson–Riley (N–R) extrapolation function, respectively. The increase in Zr⁴⁺ content leads to a reduction in crystallite size and an increase in the lattice parameter. Elastic properties are estimated from force constants and the lattice constant, determined from FTIR and XRD, respectively. The observed changes in the elastic constants are attributed to the strength of interatomic bonding. The stiffness constants decrease, while Poisson’s ratio increases with increasing Zr⁴⁺ content, reflecting the increase in the ductility of the prepared samples. As the Zr⁴⁺ content increases, the stiffness constants decrease, and Poisson’s ratio increases, reflecting enhanced ductility of the samples. Furthermore, as Zr⁴⁺ content rises, Young’s modulus, the rigidity modulus and Debye temperature decrease. The magnetic hysteresis loop measurements are carried out at room temperature using a vibrating sample magnetometer (VSM) over a field range of 25 kg. Unsubstituted CoCr₂O₄ exhibits ferrimagnetic behavior. As Zr⁴⁺ content increases, saturation magnetization (M_s) and magnetic moment decrease, while remanent magnetization (M_r) and coercivity (H_c) initially decrease up to x = 0.10, then increase with further increases in x. The novel key of this study is how Zr⁴⁺ substitution in CoCr₂O₄ nanoparticles can effectively modify their elastic moduli and magnetic properties, making them suitable for various applications such as flexible electronics, protective coatings, energy storage components and biomedical implants. Full article

Using free microorganisms for industrial processes has some limitations, such as the extensive consumption of substrates for growth, significant sensitivity to the microenvironment, and the necessity of separation from the product and, therefore, the cyclic process. It is widely acknowledged that confining or immobilizing cells in a matrix or support structure enhances enzyme stability, facilitates recycling, enhances rheological resilience, lowers bioprocess costs, and serves as a fundamental prerequisite for large-scale applications. This report summarizes the various cell immobilization methods, including several synthetic (polyvinylalcohol, polyethylenimine, polyacrylates, and Eudragit) and natural (gelatin, chitosan, alginate, cellulose, agar–agar, carboxymethylcellulose, and other polysaccharides) polymeric materials in the form of thin films, hydrogels, and cryogels. Advancements in the production of well-known antibiotics like penicillin and cephalosporin by various strains were discussed. Additionally, we highlighted cutting-edge research related to strain producers of peptide-based antibiotics (polymyxin B, Subtilin, Tyrothricin, varigomycin, gramicidin S, friulimicin, and bacteriocin), glusoseamines, and polyene derivatives. Crosslinking agents, especially covalent linkers, significantly affect the activity and stability of biocatalysts (penicillin G acylase, penicillinase, deacetoxycephalosporinase, L-asparaginase, β-glucosidase, Xylanase, and urease). The molecular weight of polymers is an important parameter influencing oxygen and nutrient diffusion, the kinetics of hydrogel formation, rigidity, rheology, elastic moduli, and other mechanical properties crucial for long-term utilization. A comparison of stability and enzymatic activity between immobilized enzymes and their free native counterparts was explored. The discussion was not limited to recent advancements in the biopharmaceutical field, such as microorganism or enzyme immobilization, but also extended to methods used in sensor and biosensor applications. In this study, we present data on the advantages of cell and enzyme immobilization over microorganism (bacteria and fungi) suspension states to produce various bioproducts and metabolites—such as antibiotics, enzymes, and precursors—and determine the efficiency of immobilization processes and the optimal conditions and process parameters to maximize the yield of the target products. Full article

Previous studies on the physical properties of alloy materials often focus solely on analyzing the impact of individual alloying element content, overlooking the underlying mechanism behind the synergistic action of multiple alloying elements. Therefore, in this study, we propose a combination of high-throughput computation and numerical analysis to conduct single-element (SE) analysis and multi-element (ME) analysis on the internal relationships between alloying element content and physical properties for the multi-component Ni_x1Cr_x2Co_x3Al₁₅Ti₁₀ alloys, aiming to elucidate the competition mechanism among the Ni, Cr, and Co elements. The analysis of SE reveals how the physical properties of alloys are affected by the content of each individual alloying element, and the ME analysis further unveils the underlying competitive relationships among multiple alloying elements. The order of competitive intensity for the formation of lattice constant is Cr > Co > Ni, whereas for the formation of elastic constants and elastic moduli it is Ni > Co > Cr. At the same time, there are contradictory conclusions, such as the SE analysis showing that the Ni content is positively correlated with elastic constant $C_{11}$, while the ME analysis demonstrates that the Ni element produces a negative competitive direction. This outcome arises from the omission of considering the combined impacts of various alloying elements in SE analysis. Therefore, the ME analysis can compensate for the limitations of SE analysis, and the integration of these two analytical methods is more conducive to elucidating the competition mechanism among various alloying elements in shaping the physical properties of alloys, which provides a promising avenue for theoretical research. Full article

Researching the mechanical characteristics of concrete subjected to the freeze–thaw cycle is crucial for building engineering in cold climates. As a result, uniaxial compression tests were performed on concrete samples exposed to various freeze–thaw (F–T) cycles, and the measurements of the pore size distribution, porosity, and P-wave velocity of the saturated concrete samples were obtained, both before and after being exposed to the F–T cycles. Concrete’s F–T damage mechanism and damage evolution model were thoroughly examined. Using rock structure and moisture analysis test equipment to observe the T₂ spectrum, the results showed that the F–T cycles can cause the internal structure of the samples to deteriorate. Porosity and F–T cycles have a positive correlation, although P-wave velocity has a negative correlation with the F–T cycles. As the F–T cycles increased, the specimens’ peak strength and elastic modulus steadily declined, while the peak strain clearly exhibited an increasing trend. A microscopic F–T damage model that takes into account the pore size distribution was developed, based on the relative changes in the pore structure distribution (PSD), before and after the F–T cycles. The concrete sample damage evolution law under various F–T cycles was examined using the following metrics: total energy, pore size distribution, static and dynamic elastic moduli, porosity, and P-wave velocity. Uniaxial compressive strength (UCS) and peak strain tests were used to evaluate the accuracy of the pore size distribution damage model, as well as that of five other widely used damage models. Full article

Improving the physico-mechanical characteristics of bitumen is a constant and pressing problem in road construction. The issue is solved by modifying bitumen with various additives, one of which is a nanostructured modifier. This paper examines the effect of adding a natural mineral, shungite, to bitumen from the Koksu deposit (Kazakhstan) after grinding under different conditions. The mechanochemical activation of shungite made it possible to obtain samples with an average particle diameter of up to 3 μm. Using scanning electron microscopy, nanostructured particles with sizes of up to 100 nm were discovered in their structure. The effect of nanostructured shungite on the rheological characteristics of bitumen—elasticity and loss moduli, and loss tangent at high and low temperatures—was studied. The transition temperatures of bitumen from the viscoelastic to the liquid state were established, and their shift to the region of elevated temperatures when modified with ground shungite are shown. The presence of organic and inorganic components in the composition of shungite—carbon, silica, and metal oxides—has a beneficial effect on the rheological properties of bitumen by forming bonds with resinous asphaltene components of bitumen. The use of bitumen modified with nanostructured shungite makes it possible to replace the polymer modifier with a natural mineral to improve the quality of the road surface. Full article

This study demonstrated the potential of a non-destructive evaluation (NDE) method to assess the elastic properties of materials printed under various parameters. A database was created documenting the relationship between the elastic properties (Young’s modulus, shear modulus, and Poisson’s ratio) of PLA (polylactic acid) materials and selected printing parameters such as temperature, speed, and layer height. PLA, which is widely used in additive manufacturing, offers convenient testing conditions due to its less demanding control compared to materials like metals. Ultrasonic testing was conducted on specimens printed under different nozzle temperatures, speeds, and layer heights. The results indicated that an increase in the printing temperature corresponded to an increase in material density and elastic properties of the material. In contrast, an increase in layer height led to a decrease in both density and the elastic properties of the material. Variations in the nozzle speed had a negligible effect on density and did not show a notable effect on the elastic moduli. This study demonstrated that ultrasonic testing is effective in measuring the elastic properties of PLA materials and shows the potential of real-time ultrasonic NDE. Full article

On the human face, the lips are one of the most important anatomical elements, both morphologically and functionally. Morphologically, they have a significant impact on aesthetics, and abnormal lip morphology causes sociopsychological problems. Functionally, they play a crucial role in breathing, articulation, feeding, and swallowing. An apparatus that can accurately and easily measure the elastic modulus of perioral tissues in clinical tests was developed, and its measurement sensitivity was evaluated. The apparatus is basically a uniaxial compression apparatus consisting of a force sensor and a displacement sensor. The displacement sensor works by enhancing the restoring force due to the deformation of soft materials. Using the apparatus, the force and the displacement were measured for polyurethane elastomers with various levels of softness, which are a model material of human tissues. The stress measured by the developed apparatus increased in proportion to Young’s modulus, and was measured by the compression apparatus at the whole region of Young’s modulus, indicating that the relation can be used for calibration. Clinical tests using the developed apparatus revealed that Young’s moduli for upper lip, left cheek, and right cheek were evaluated to be 45, 4.0, and 9.9 kPa, respectively. In this paper, the advantages of this apparatus and the interpretation of the data obtained are discussed from the perspective of orthodontics. Full article

Electrospun drug-eluting fibers have demonstrated potentials in topical drug delivery applications, where drug releases can be modulated by polymer fiber compositions. In this study, blend fibers of polycaprolactone (PCL) and polyethylene oxide (PEO) at various compositions were electrospun from 10 wt% of polymer solutions to encapsulate a model drug of ibuprofen (IBP). The results showed that the average polymer solution viscosities determined the electrospinning parameters and the resulting average fiber diameters. Increasing PEO contents in the blend PCL/PEO fibers decreased the average elastic moduli, the average tensile strength, and the average fracture strains, where IBP exhibited a plasticizing effect in the blend PCL/PEO fibers. Increasing PEO contents in the blend PCL/PEO fibers promoted the surface wettability of the fibers. The in vitro release of IBP suggested a transition from a gradual release to a fast release when increasing PEO contents in the blend PCL/PEO fibers up to 120 min. The in vitro viability of blend PCL/PEO fibers using MTT assays showed that the fibers were compatible with MEF-3T3 fibroblasts. In conclusion, our results explained the scientific correlations between the solution properties and the physicomechanical properties of electrospun fibers. These blend PCL/PEO fibers, having the ability to modulate IBP release, are suitable for topical drug delivery applications. Full article

Food hydrogels, used as delivery systems for bioactive compounds, can be formulated with various food-grade biopolymers. Their industrial utility is largely determined by their physicochemical properties. However, comprehensive data on the properties of pea protein–psyllium binary hydrogels under different pH and ionic strength conditions are limited. The aim of this research was to evaluate the impact of pH (adjusted to 7, 4.5, and 3) and ionic strength (modified by NaCl addition to 0.15 and 0.3 M) on the physical stability, color, texture, microrheological, and viscoelastic properties of these hydrogels. Color differences were most noticeable at lower pH levels. Inducing hydrogels at pH 7 (with or without NaCl) and pH 4.5 and 3 (without NaCl) resulted in complete gel structures with low stability, low elastic and storage moduli, and low complex viscosity, making them easily spreadable. Lower pH inductions (4.5 and 3) in the absence of NaCl resulted in hydrogels with shorter linear viscoelastic regions. Hydrogels induced at pH 4.5 and 3 with NaCl had high structural stability, high G’ and G” moduli, complex viscosity, and high spreadability. Among the tested induction conditions, pH 3 with 0.3 M NaCl allowed for obtaining a hydrogel with the highest elastic and storage moduli values. Adjusting pH and ionic strength during hydrogel induction allows for modifying and tailoring their properties for specific industrial applications. Full article

The impact of contact between two elastic–plastic bodies is highly complex, with no established theoretical contact model currently available. This study investigates the problem of an elastic–plastic sphere impacting an elastic–plastic half-space at low speed and low energy using the finite element method (FEM). Existing linear contact loading laws exhibit significant discrepancies as they fail to consider the impact of elasticity and yield strength on the elastic–plastic sphere. To address this limitation, a novel linear contact loading law is proposed in this research, which utilizes the concept of equivalent contact stiffness rather than the conventional linear contact stiffness. The theoretical expressions of this new linear contact loading law are derived through FEM simulations of 150 sphere and half-space impact cases. The segmental linear characteristics of the equivalent contact stiffness are identified and fitted to establish the segmental expressions of the equivalent contact stiffness. The new linear contact loading law is dependent on various factors, including the yield strain of the half-space, the ratio of elastic moduli between the half-space and sphere, and the ratio of yield strengths between the half-space and sphere. The accuracy of the proposed linear contact loading law is validated through extensive Finite Element Method simulations, which involve an elastic–plastic half-space being struck by elastic–plastic spheres with varying impact energies, sizes, and material combinations. Full article

The rock’s mechanical properties play an important role in the whole process of conventional and unconventional oil and gas exploration and progression. At present, there are two approaches to determining the mechanical parameters. One is to measure the rock sample in the laboratory (i.e., static elastic modulus E_s). The other is to obtain parameters by geophysical logging data (i.e., dynamic elastic modulus E_d). In general, static parameters can more accurately reflect the mechanical properties of rock under actual geo-stresses. At the same time, their determinations are difficult. Therefore, one of the best methods is to establish the correlation between the dynamic and static parameters. This paper investigates the relation between the dynamic and static parameters using different methods for various rocks in the literature. Based on the relationship of $E_{\mathrm{s}}=\mathrm{a}{E}_{\mathrm{d}}+\mathrm{b}$, a correction between a and b is proposed using the multinomial form $\mathrm{a}=0.67+0.101\mathrm{b}-0.006{\mathrm{b}}^2+0.0001{\mathrm{b}}^3$. It is found that the E_s can be derived from the E_d just when the parameter b is known. In terms of different types of rocks, for igneous and metamorphic rocks, the best correlation between E_s and E_d obeys the power-law correlation; for sedimentary rocks, there are linear and logarithmic correlations. Theoretically, the difference between dynamic and static elastic moduli can be attributed to microcracks and pores within rocks. This study can provide guidance for engineers to predict the desired static parameters precisely using logging or seismic data. Full article

In recent years, tubular nanostructures have been related to immense advances in various fields of science and technology. Considerable research efforts have been centred on the theoretical prediction and manufacturing of non-carbon nanotubes (NTs), which meet modern requirements for the development of novel devices and systems. In this context, diatomic inorganic nanotubes formed by atoms of elements from the 13th group of the periodic table (B, Al, Ga, In, Tl) and nitrogen (N) have received much research attention. In this study, the elastic properties of single-walled boron nitride, aluminium nitride, gallium nitride, indium nitride, and thallium nitride nanotubes were assessed numerically using the nanoscale continuum modelling approach (also called molecular structural mechanics). The elastic properties (rigidities, surface Young’s and shear moduli, and Poisson’s ratio) of nitride nanotubes are discussed with respect to the bond length of the corresponding diatomic hexagonal lattice. The results obtained contribute to a better understanding of the mechanical response of nitride compound-based nanotubes, covering a broad range, from the well-studied boron nitride NTs to the hypothetical thallium nitride NTs. Full article

The mechanical properties of porcupine quills have attracted the interest of researchers due to their unique structure and composition. However, there is still a knowledge gap in understanding how these properties can be utilized to design biomimetic structures with enhanced performance. This study delves into the nanomechanical and macro-mechanical properties of porcupine quills, unveiling varied elastic moduli across different regions and cross sections. The results indicated that the elastic moduli of the upper and lower epidermis were higher at 8.13 ± 0.05 GPa and 7.71 ± 0.14 GPa, respectively, compared to other regions. In contrast, the elastic modulus of the mid-dermis of the quill mid-section was measured to be 7.16 ± 0.10 GPa. Based on the micro- and macro-structural analysis of porcupine quills, which revealed distinct variations in elastic moduli across different regions and cross sections, various biomimetic porous structures (BPSs) were designed. These BPSs were inspired by the unique properties of the quills and aimed to replicate and enhance their mechanical characteristics in engineering applications. Compression, torsion, and impact tests illustrated the efficacy of structures with filled hexagons and circles in improving performance. This study showed enhancements in maximum torsional load and crashworthiness with an increase in filled structures. Particularly noteworthy was the biomimetic porous circular structure 3 (BPCS_3), which displayed exceptional achievements in average energy absorption (28.37 J) and specific energy absorption (919.82 J/kg). Finally, a response surface-based optimization method is proposed to enhance the design of the structure under combined compression-torsion loads, with the goal of reducing mass and deformation. This research contributes to the field of biomimetics by exploring the potential applications of porcupine quill-inspired structures in fields such as robotics, drive shafts, and aerospace engineering. Full article

Orthodontic mini-implants are devices used for anchorage in various orthodontic treatments. We conducted a pilot study which aimed to observe preliminary trends regarding the impact of heat treatment on the elastic modulus of Ti6Al4V alloy and stainless steel 316L mini-implants. The initial phase involved testing the impact of heat treatment on the mechanical properties of Ti6Al4V alloy and stainless steel 316L mini-implants. Material and methods: Ten self-drilling mini-implants sourced from two distinct manufacturers (Jeil Medical Corporation^® and Leone^®) with dimensions of 2.0 mm diameter and 10 mm length were tested. They were separated into two material groups: Ti6Al4V and 316L. Using the CETRUMT-2 microtribometer equipment, indentation testing was conducted employing a diamond-tipped Rockwell penetrator at a constant force of 4.5 N. Results: Slight differences were observed in the elastic modulus of the Ti6Al4V alloy (103.99 GPa) and stainless steel 316L (203.20 GPa) compared to natural bone. The higher elastic moduli of these materials indicate that they are stiffer, which could potentially lead to stress-shielding phenomena and bone resorption. Heat treatment resulted in significant changes in mechanical properties, including elastic modulus reductions of approximately 26.14% for Ti6Al4V and 24.82% for 316L, impacting their performance in orthodontic applications. Conclusion: Understanding the effects of heat treatment on these alloys is crucial for optimizing their biomechanical compatibility and longevity in orthodontic treatment. To fully evaluate the effects of heat treatment on mini-implants and to refine their design and efficacy in clinical practice, further research is needed. Full article