Bulk Modulus Research Articles

Sound velocities, elasticity and thermal properties of cBN composite with AlN binder at high pressure

Cubic boron nitride (cBN) has been used as a tool material for several decades due to its high hardness and thermal stability. Various binders are commonly added to cBN to synthesise cBN composites for better cutting performance. However, most studies have only investigated properties such as hardness and bulk modulus, without comprehensively studying elastic properties through experiments. In this study, the sound velocities and elastic properties of cBN with AlN binder were determined by using the ultrasonic interferometry technique. The bulk and shear moduli with their pressure dependence were determined as B0 = 351(3) GPa, G0 = 344(3) GPa, = 4.32(4) and = 1.74(2) using the finite strain equation-of-state approaches. Elasticity-related thermal properties, such as Debye temperature, Grüneisen parameter, thermal conductivity and coefficient of thermal expansion were also estimated. The results show that the elastic properties of the cBN composite with vol. 8.8% AlN-binder are comparable to the pure cBN compact. Additionally, the thermal conductivity and coefficient of thermal expansion have little effect on cBN composite with AlN binder compared to pure cBN.

Influence of frost heave with confining pressure under seepage on compressive strength of frozen silt in artificial ground freezing

Artificial ground freezing (AGF) is used for constructing subway cross passages in coastal areas. The continuous construction of complex projects (cross-sea or cross-river tunnels) has resulted in freezing environments with high groundwater seepage velocities. Seepage cannot provide an open system in soil freezing for moisture migration, resulting in large amount of frost heave owing to segregated ice compared to close freezing system. The influence of frost heave under seepage on the compressive strength of frozen silt during artificial ground freezing must be studied to ensure AGF construction safety. Thus, a unidirectional freezing device that can control seepage and confining pressure conditions during freezing was designed to prepare frozen silt samples under different seepage velocities with confining pressures and to measure the relevant segregation frost heave. Subsequently, uniaxial compression tests were performed. The compressive strength of frozen silt under the influence of frost heave and seepage conditions was analyzed. The frost heave rate, uniaxial compressive strength, and elastic modulus of frozen silt in an open freezing system were measured. The seepage velocity during freezing increased the frost heave rate of the silt; the uniaxial compressive strength and elastic modulus of the frozen silt increased subsequently. The effective confining pressure suppressed frost heave of silt and reduced the uniaxial compressive strength and elastic modulus of the frozen silt. The test results were analyzed considering the segregation frost heave formation mechanism, and a theoretical improvement model of the uniaxial compressive strength and elastic modulus of frozen silt related to the content of segregated ice was proposed. This research is significant for ensuring the AGF construction safety in cross-river or ocean tunnel engineering under seepage conditions.

Assessing the hydromechanical control of plant growth.

Multicellular organisms grow and acquire their shapes through the differential expansion and deformation of their cells. Recent research has addressed the role of cell and tissue mechanical properties in these processes. In plants, it is believed that growth rate is a function of the mechanical stress exerted on the cell wall, the thin polymeric layer surrounding cells, involving an effective viscosity. Nevertheless, recent studies have questioned this view, suggesting that cell wall elasticity sets the growth rate or that uptake of water is limiting for plant growth. To assess these issues, we developed a microfluidic device to quantify the growth rates, elastic properties and hydraulic conductivity of individual Marchantia polymorpha plants in a controlled environment with a high throughput. We characterized the effect of osmotic treatment and abscisic acid on growth and hydromechanical properties. Overall, the instantaneous growth rate of individuals is correlated with both bulk elastic modulus and hydraulic conductivity. Our results are consistent with a framework in which the growth rate is determined primarily by the elasticity of the wall and its remodelling, and secondarily by hydraulic conductivity. Accordingly, the coupling between the chemistry of the cell wall and the hydromechanics of the cell appears as key to set growth patterns during morphogenesis.

Assessment of the anisotropy development of mechanical properties of pitch-based carbon fibers

Carbon fiber XN-P9 derived from anisotropic pitch was heat treated at different temperatures (2000, 2500, and 3000℃) and the mechanical properties of those single filament in various directions were tested with some methods we have developed. The anisotropy of the mechanical properties of those pitch-based carbon fibers was evaluated to be developed by heat treatment. As a comparison, the properties of carbon fiber XN-05 derived from isotropic pitch were also tested. The ratio of the longitudinal tensile modulus to the shear modulus of XN-05 fiber was approximately 3. In contrast, for pristine XN-P9 fiber, the longitudinal tensile modulus was more than nine times greater than the shear modulus, and the difference between these moduli increased with the elevating heat treatment temperatures. It was suggested that the anisotropy of mechanical properties of pitch-based carbon fibers was developed by heat treatment. In compressive deformation in the transverse direction to the fiber axis, a yielding and a softening was clearly observed with the elevating heat treatment temperature. The effect of anisotropy development on the span-length dependence of flexural modulus obtained from the three-point bending test of the single filament was assessed.

Rheological behavior of brain tissue: Experiments vs theory and forensic applications

Experimental data describing the uniaxial compression and relaxation of brain tissue are compared to the predictions from a rheological model developed by Yarin and Kosmerl [“Rheology of brain tissue and hydrogels: A novel hyperelastic and viscoelastic model for forensic applications,” Phys. Fluids 35, 101910 (2023)]. A qualitative agreement between the model and experiments with swine brain tissue is confirmed, and the uniformly valid values (i.e., valid in all rheometric experiments without any change) of the rheological parameters are established. These are the values of the following four parameters: G (the shear modulus), κ (the bulk modulus), α (the dimensionless degree of hyperelasticity), and θ (the viscoelastic relaxation time). In addition, the present rheological model with the established rheological parameters is incorporated into a dynamic model of bullet penetration into brain tissue after a short-range shooting, when muzzle gases and/or air fill the bullet channel leading to its widening, wave propagation, fragmentation, and backspatter of brain tissue. This problem is of significant interest in forensic science because there is an urgent need to provide physics-informed models to reconstruct and analyze crime scenes.

Structural, electronic and optical properties of the Half-Heusler MgYGa alloy Via DFT calculations

Ab initio calculation of the structural, electronic and optical properties of half-Heusler MgYGa alloy are reported using the FP-LAPW approach of the Density Functional Theory. Generalized Gradient Approximation was used as the exchange and correlation potential for investigating these properties. Structural properties of MgYGa alloy, such as the lattice constants, bulk modulus and pressure derivative of the bulk module have been studied. Electronic properties were investigated by calculating and analyzing the electronic band structure, partial and total density of states graphs for the MgYGa compound. We have found that MgYGa compound has a metallic character. The investigation of optical properties indicates a great interaction between the compound and the incident light.

Evaluating hydrogen storage potential of NaNbO3-xHx: DFT-based approach

Alternative energy carrier materials are needed since non-renewable energy resources are diminishing at a fast rate. Increasingly, hydrogen storage has gained popularity as a clean energy source. For the first time, NaNbO3-xHx has been explored computationally as a potential material for hydrogen storage using the GGA-PBE approach as implemented in the CASTEP code. Structural, elastic, mechanical, electronic, and optical characteristics have been investigated to evaluate the suitability of the proposed material for hydrogen storage applications. All H-incorporated concentrations are thermodynamical and energetically stable and can be synthesized. Structural parameters vary with varying hydrogen concentrations; however, against each hydrogen concentration, the material maintains cubical geometry. The NaNbO2.7H0.3 show the highest (742.92 GPa) bulk modulus, while NaNbH3 stands with the lowest (52.48 GPa) among all. Standardizing the Poisson ratio reveals a brittle nature except for the X=0.3 composition. With increasing H-incorporation in the structure, the band gap increases (1.624 eV » 2.505 eV) and also causes electronic nature shifting (p-type → n-type); however, the band gap remains indirect over different symmetry points in BZ. Hence, have the potential for numerous optoelectronic applications. Furthermore, optical parameters, dielectric constant, refractive index, extinction coefficient, reflectivity, absorption coefficients, and loss functions are analyzed, which reveal the potential for numerous optoelectronic applications. Hydrogen storage capacity achieved up to 2.48 %, allowing this material to be utilized in energy storage systems.

Analytical calculation model for elastic modulus and strength of foamed concrete

Foamed concrete has gained increasing attention for its excellent engineering performance. Endeavors have been made to experimentally and numerically elucidate the mechanism of foamed concrete, while few theoretical methods are used to analytically calculate mechanical properties. This paper proposes a theoretical framework to describe the elastic behavior of foamed concrete by combining Eshelby’s equivalent inclusion theory with the Mori–Tanaka method. In the analytical model, foamed concrete is regarded as a two-phase composite comprising a homogeneous cement matrix and randomly oriented ellipsoidal air void. During derivation, the elastic modulus, strength, bulk modulus, shear modulus, and Poisson ratio are measured. A good agreement is established between the proposed method and experimental data.

High-pressure elasticity of novel (VNbTaTi)C high-entropy carbides

Acoustic velocities and elasticity of high P-T synthesized new (VNbTaTi)C high-entropy carbides (HECs) are reported at high pressure using large volume press (LVP)-based ultrasonic interferometry technique. Using the finite-strain equation approach, the bulk modulus and shear rigidity, and their pressure dependences, are derived from the current experimental data, yielding B0 = 261.6(2) GPa, G0 = 191.4(3) GPa, ∂B/∂P = 4.34(18), and ∂G/∂P = 1.83(6). Interestingly, the (VNbTaTi)C HECs is more incompressible than the superhard γ-B (~213.9GPa), and almost as incompressible as superhard PcBN (~254GPa). Meanwhile, its shear rigidity (~191.4GPa) is comparable to the superhard B6O-B4C composite (G = 202GPa), and as stiff as the (TiZrNbTa)C (193 ~ 195GPa) HECs. More strikingly, the fracture toughness is enhanced up to ~4.6(3) MPa·m1/2, and the Vickers hardness of (VNbTaTi)C HECs is ~22.6(2) GPa, which are significantly stronger than other high-entropy carbides. These new findings and results may be very important for its applications in extreme environments.

Photocatalytic efficiency of GO-based Ti-doped Co3O4 nanosheets for mixed dyes and the effects of oxidizing and reducing reagents

The hydrothermal technique was used to synthesize the GO-based Ti-doped Co3O4 nanosheets and investigate their photocatalytic properties. These synthesized smart and active materials degraded the mixed dyes of Methylene orange (MO) and Methylene blue (MB) under the sunlight within 180 min with an effective efficiency of 94.85%. Various physical parameters were studied by using distinct characterization techniques related to structural, compositional, optical, and I-V characteristics. The effects of Young’s modulus, stiffness, bulk modulus, microstrain, stacking fault, and dislocation density were studied in detail. The conversion of phase was identified by using Raman spectroscopy. The effects of band gap, surface area, and photosensitivity were illustrated thoroughly. The effect of scavengers on the photocatalytic efficiency was observed and it was concluded that both electrons and holes are activated during the photocatalytic activity. The doping of Ti has played a crucial role in enhancing surface area, electron transfer rate, photosensitivity, and reduction in the bandgap. These smart materials are also useful for photodetector applications.

Half Metallic Properties of the Polymorphs of Rubidium Selenide Compound

Half-metallic ferromagnets denote a specific category of compounds where one spin channel exhibits a gap at the Fermi level, contrasting with the metallic nature of the other spin channel. This distinction results in complete carrier spin polarization, reaching 100% at the Fermi level. A first-principles pseudopotential plane-wave method is utilized to examine the structural, electronic, and magnetic characteristics of RbSe across various polymorphs. Our investigation covers the RbSe compound in the CsCl (B2), NaCl (B1), ZnS (B3), NiAs (B81) and wurtzite (B4) phases. The calculations were done using the quantum ESPRESSO code within the generalized gradient approximation. The lattice parameters, bulk moduli, and their pressure derivatives agrees with prior theoretical data for cubic structures. The electronic band structures and density of states indicate the emergence of half-metallic and magnetic properties in RbSe, which stem from the existence of spin-polarized p orbitals within the Se atom. RbSe shows half-metallic behaviour in all structures studied with an integer magnetic moment of 1μB per formula unit for CsCl, NaCl, ZnS; and 2μB for NiAs and wurtzite. Results showed that most energetically stable phase of all five crystal structures studied is the CsCl-type of RbSe.

Impact of 3D printing parameters on static and fatigue properties of polylactic acid (PLA) bone scaffolds

In the present study, polylactic acid (PLA) scaffolds with a 60 % porosity and gyroid pore structure were 3D printed using the extrusion-based method and employing various printing parameters. The specimens were loaded under quasit-static and cyclic conditions and their mechanical behaviour were evaluated. The Taguchi method was utilized to design experiments and investigate the impact of printing parameters on the compressive properties of the scaffolds. Moreover, thermography analysis was used to examine the influence of cyclic heating during fatigue experiments. The results indicated that extrusion width was the sole variable significantly affecting the quasi-static properties of scaffolds. The largest extrusion width (0.65 mm) resulted in the highest compressive properties (6–7 MPa), plateau stress (8–9 MPa), and compressive modulus (200–215 MPa). However, fatigue experiments revealed that nozzle temperature was the sole influencing factor on the fatigue performance of scaffolds, with specimens printed at low nozzle temperature (190 °C) demonstrating the highest fatigue resistance. Thermography analysis exhibited a negative correlation between scaffold temperature and stiffness. However, the impact of temperature on the structural integrity of the scaffolds was insignificant, given that the highest temperature recorded during fatigue cycles (i.e., 39 °C) was below the glass transition temperature of the scaffolds’ material.

Stretchable rubber composites with lower hysteresis losses, improved magnetic effect, and a robust magnetic sensitivity

The stretchable materials exhibit various challenges such as high hysteresis losses, lower magnetic effect, and less magnetic sensitivity. In this work, we design and fabricate stretchable magnetic-rheological elastomers based on silicone rubber with robust magnetic sensitivity and lower hysteresis losses. The nanofillers used were carbon black (CB), and electrolyte iron particle (EIP). The stretchable materials obtained show an anisotropic effect of up to 165%. Moreover, the hysteresis losses were 0.4 kJ (control), 2.45 kJ (15 phr of CB), 0.58 kJ (60 phr of EIP), and 3.53 kJ (60 phr of hybrid filler system). The compressive modulus was 1.4 MPa (control), 3.76 MPa (15 phr of CB), 2.1 MPa (60 phr of EIP), and 3.9 MPa (60 phr of hybrid filler system). The fracture strain was 164% (control), 160% (15 phr of CB), 100% (60 phr of EIP), and 139% (60 phr of hybrid filler system). To sum up, the CB shows robust mechanical properties with high stretchability. However, the hybrid filler system shows high stiffness with a higher magnetic response. Finally, EIP-filled composites show optimum stiffness and robust magnetic response force.

Synergistic effect of Polyvinyl Acetate (PVA) and Enzyme-Induced Carbonate Precipitation (EICP) on the mechanical properties of natural sands

Effective enhancement of the mechanical properties of cohesionless soils is crucial for diverse geotechnical applications, given their inherent vulnerability to load-induced failure due to the absence of inter-particle bonding. Soil failures pose significant risks to both human lives and infrastructure, necessitating the development of environmentally friendly soil improvement methods. Conventional techniques often entail invasive processes and substantial carbon emissions. In response, contemporary approaches seek to minimize environmental impact while preserving organic material characteristics. This study investigates the synergistic effect of polyvinyl acetate (PVA) and enzyme-induced carbonate precipitation (EICP) treatment for enhancing the mechanical properties of cohesionless natural sands. Beach and river sands were treated with varying proportions of PVA in conjunction with an optimized EICP solution for yielding the best results. Unconfined compressive strength (UCS) tests were conducted at 7, 14, and 28-day curing intervals to assess the performance of the soil-polymer-EICP composites (SPEC). The results demonstrated substantial improvements in compressive strength and elastic modulus with increasing PVA content. For beach sand, after 7 days of heat curing, the peak strength increased from 0.89 MPa to 11.07 MPa for composites with 1% and 11% PVA, respectively. Similarly, for river sand, the peak strength increased from 0.87 MPa to 8.96 MPa under the same conditions. The findings also highlighted the softening behavior induced by PVA with heat curing over the period. This softening phenomenon was attributed to the thermo-plastic characteristics of the polymer film induced by temperature conditions.

Mimicking the mechanical properties of cortical bone with an additively manufactured biodegradable Zn-3Mg alloy

Additively manufactured (AM) biodegradable zinc (Zn) alloys have recently emerged as promising porous bone-substituting materials, due to their moderate degradation rates, good biocompatibility, geometrically ordered microarchitectures, and bone-mimicking mechanical properties. While AM Zn alloy porous scaffolds mimicking the mechanical properties of trabecular bone have been previously reported, mimicking the mechanical properties of cortical bone remains a formidable challenge. To overcome this challenge, we developed the AM Zn-3Mg alloy. We used laser powder bed fusion to process Zn-3Mg and compared it with pure Zn. The AM Zn-3Mg alloy exhibited significantly refined grains and a unique microstructure with interlaced α-Zn/Mg2Zn11 phases. The compressive properties of the solid Zn-3Mg specimens greatly exceeded their tensile properties, with a compressive yield strength of up to 601 MPa and an ultimate strain of >60%. We then designed and fabricated functionally graded porous structures with a solid core and achieved cortical bone-mimicking mechanical properties, including a compressive yield strength of >120 MPa and an elastic modulus of ≈20 GPa. The biodegradation rates of the Zn-3Mg specimens were lower than those of pure Zn and could be adjusted by tuning the AM process parameters. The Zn-3Mg specimens also exhibited improved biocompatibility as compared to pure Zn, including higher metabolic activity and enhanced osteogenic behavior of MC3T3 cells cultured with the extracts from the Zn-3Mg alloy specimens. Altogether, these results marked major progress in developing AM porous biodegradable metallic bone substitutes, which paved the way toward clinical adoption of Zn-based scaffolds for the treatment of load-bearing bony defects. Statement of SignificanceOur study presents a significant advancement in the realm of biodegradable metallic bone substitutes through the development of an additively manufactured Zn-3Mg alloy. This novel alloy showcases refined grains and a distinctive microstructure, enabling the fabrication of functionally graded porous structures with mechanical properties resembling cortical bone. The achieved compressive yield strength and elastic modulus signify a critical leap toward mimicking the mechanical behavior of load-bearing bone. Moreover, our findings reveal tunable biodegradation rates and enhanced biocompatibility compared to pure Zn, emphasizing the potential clinical utility of Zn-based scaffolds for treating load-bearing bony defects. This breakthrough opens doors for the wider adoption of zinc-based materials in regenerative orthopedics.

Self-composite silk fibroin membranes for guided bone regeneration: 1 material 3 architectures with intrinsic integrity

Silk fibroin (SF) takes attention in tissue engineering due to unique features, e.g., excellent biocompatibility/biodegradability with superior mechanical/thermal properties despite its lightweight. Guided bone regeneration (GBR) seeks bilayered GBR membranes to govern bone regeneration, although constituent parts of such membranes may undergo delamination once different biomaterials are combined. Herein, 3-component bilayered SF membranes were prepared for the first time utilizing the same polymer in different forms by eliminating the delamination risk of layers for GBR applications. One side consisted of a non-porous SF film serving as a barrier against penetration of non-osteogenic tissue whereas the other side was porous/fibrous composed of SF sponge and SF fibers for bone regeneration. Proper integration between these layers was confirmed via scanning electron microscopy (SEM). Composites reinforced with high fiber percent (30%) had remarkably enhanced compressive strength and elastic moduli, which were further improved by increasing polymer concentration from 4% to 8%. Non-porous morphology of the barrier side was preserved during 28 days of degradation while pore sizes enlarged on the other surface, which would be beneficial for cell migration into the regenerative side. Saos-2 cells seeded on composites with high fiber percent proliferated more within 14 days; however, alkaline phosphatase (ALP) activity on low-fiber-percent counterparts was elevated more. Osteogenic marker gene expressions were significantly higher than control on day 14. All self-composites were eminent candidates to promote bone regeneration with tailor-made capacity for further improvements. Taken together, 1-material 3-architecture SF fabricated by a green and practical technique holds promise for GBR applications.

Cyclic loading behavior of concrete with thermally-induced damage

The paper reports a study on concrete specimens that were subjected to constant amplitude, low-strain cyclic (LSC) and high-strain cyclic (HSC) tests to evaluate their cyclic behavior after they had been subjected to either ambient or elevated temperatures. Parameters examined included maximum normal stress, dynamic modulus, and extent of damage observed in specimens. An equation is proposed to help quantify the extent of damage in specimens, which accounts for both thermal and cyclic loading effects. Ultrasonic Pulse Velocity (UPV) measurements were also used to quantify the damage in both the LSC and HSC tests. Results show that losses in compressive strength and dynamic modulus are greater in cases with higher temperature exposures due to thermally induced damages. Also, cyclic characteristics of the specimens were found to be significantly influenced by the strain amplitude used in cyclic loading tests.

Study on rock energy evolution and constitutive model under water–rock interaction

To explore the degradation in rock mechanical properties due to water–rock interactions and formulate a nonlinear damage constitutive model for the entire stress–strain curve of rocks, experiments involving saturated, dry-wet cycling, and uniaxial compression tests were conducted on granite and siltstone. Based on energy theory, the energy evolution of the rock throughout the testing process was scrutinized. The range of the compaction stage was identified through the analysis of the dissipation energy change curve. A nonlinear damage constitutive model for rocks subjected to water-rock interactions was then devised, drawing on concepts from statistical damage mechanics. The findings indicated a progressive reduction in uniaxial compressive strength and elastic modulus due to water–rock interactions, while the Poisson’s ratio was observed to increase. The energy density curve under these conditions delineated four distinct phases: compaction energy dissipation, linear energy accumulation, pre-peak gradient increase, and post-peak sudden change. The introduction of the unit elastic strain energy density metric underscored the deteriorating effects from an energy standpoint. A nonlinear damage constitutive model, incorporating the compaction stage based on a coupled damage variable, was formulated. The predictions of this model closely matched the empirical data, thereby affirming its validity. This model provides an enhanced depiction of rock deformation and failure mechanisms under the influence of water–rock interactions.

Causal emergent principles and relations for mechanical properties of covalent and ionic crystals

A knowledge and data-synergized intelligent computation architecture for materials was proposed within the data science paradigm. As a vital operation, two digital ensemble descriptors implying chemical composition and structural trend for crystals were created using the features contained in the Periodic Table of elements without a priori assumption, which affords causal emergence and regulation principles for the mechanical response of covalent and ionic solids. In addition to a linear correlation among structural state/mechanical response parameters, causal analytic relations in an exponential form between structural and thermodynamic state/mechanical response parameters and a digital ensemble descriptor were unveiled through least squares regression, in which the coefficients are classified in accordance with symmetry principles on the atom and lattice. Thereafter, the underlying physicochemical mechanisms of chemical pressure and chemical bonding are found responsible for the mechanical responses of bulk modulus and hardness of solids. At last, a physical prediction model was established for crystalline solids and demonstrated the feasibility of the predictive design of novel superhard materials. It is believed that by constructing suitable digital ensemble descriptors, this intelligent computation architecture and consequent physical prediction models on the basis of causal analytic relations are able to generalize by depicting crystalline solids with covalent and ionic bonds in other crystallographic structures.

First-principles investigations for electronic and thermoelectric properties of XGeF[formula omitted](X = K, Rb): Nonlocal corrections and SCAN insights

In this research work we have studied the electronic band structures, density of states and thermoelectric parameters of fluorine based cubic perovskites KGeF3 and RbGeF3 using PW, PBE, SCAN, rVV10 and vdW-DF3 exchange correlation functionals implemented in Quantum ESPRESSO for thermoelectric applications. The lattice constant and bulk modulus of KGeF3 (RbGeF3) is 4.409 (4.407 Å) and 50.8 (51.8 GPa), respectively. KGeF3 has band gap of 1.917eV and RbGeF3 has band gap of 1.982eV with PBE. The band structures of both compounds are consistent to total density of states. The Seebeck coefficient, power factor, electrical and thermal conductivity are studied in a wide range of temperature from 0 to 800K. The detailed study of band gaps and thermoelectric parameters with variety of DFT methods indicates the significance of KGeF3 and RbGeF3 in thermoelectric devices under high temperature.