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This study proposes a simple yet effective dynamic method that can nondestructively evaluate the elastic properties of homogeneous isotropic solid materials. Like some dynamic methods, such as resonance ultrasound spectrometry and impulse excitation technique, the proposed method consists of two steps: experimentally acquiring the specimen's natural frequencies and numerically calculating the elastic properties. Compared with the existing methods, the proposed method has much lower requirements on all four aspects of experimental operations: specimen preparation, specimen positioning, vibration excitation, and vibration detection. An inverse method based on finite element modal analysis is proposed to calculate the specimen's elastic properties, and it can deliver optimal estimations with high precision and accuracy. The performance of the proposed method was assessed using the well-established sound speed-based dynamic method, i.e., ultrasound pulse-echo testing. Taking a square aluminum specimen as an example, the differences in the measurements of Young's modulus and Poisson's ratio between these two methods are 2.25% and −2.07%, respectively; the differences in the measurements of shear modulus and bulk modulus are 0.01% and −1.46%, respectively. In summary, the proposed method provides a cheaper and experimentally simpler approach to determining the elastic properties of solid materials while maintaining accuracy and reliability similar to the established methods, which typically require sophisticated, costly equipment. [ABSTRACT FROM AUTHOR]

Biomolecular condensates are viscoelastic materials defined by time-dependent, sequence-specific complex shear moduli. Here, we show that viscoelastic moduli can be computed directly using a generalization of the Rouse model that leverages information regarding intra- and inter-chain contacts, which we extract from equilibrium configurations of lattice-based Metropolis Monte Carlo (MMC) simulations of phase separation. The key ingredient of the generalized Rouse model is a graph Laplacian that we compute from equilibrium MMC simulations. We compute two flavors of graph Laplacians, one based on a single-chain graph that accounts only for intra-chain contacts, and the other referred to as a collective graph that accounts for inter-chain interactions. Calculations based on the single-chain graph systematically overestimate the storage and loss moduli, whereas calculations based on the collective graph reproduce the measured moduli with greater fidelity. However, in the long time, low-frequency domain, a mixture of the two graphs proves to be most accurate. In line with the theory of Rouse and contrary to recent assertions, we find that a continuous distribution of relaxation times exists in condensates. The single crossover frequency between dominantly elastic vs dominantly viscous behaviors does not imply a single relaxation time. Instead, it is influenced by the totality of the relaxation modes. Hence, our analysis affirms that viscoelastic fluid-like condensates are best described as generalized Maxwell fluids. Finally, we show that the complex shear moduli can be used to solve an inverse problem to obtain the relaxation time spectra that underlie the dynamics within condensates. This is of practical importance given advancements in passive and active microrheology measurements of condensate viscoelasticity. [ABSTRACT FROM AUTHOR]

β-LiGaO2 with a wurtzite-like crystal structure is a direct ultra-wide bandgap semiconductor. Similar to many wide bandgap oxides, the valence band of LiGaO2 is predominantly composed of O-2p orbital, leading to a low valence band position, drastically limiting its applications. In this work, we employ first-principles calculations to demonstrate that adding a small amount of Bi into LiGaO2 to form the highly mismatched Li(Ga1−xBix)O2 alloys can dramatically modulate the valence band compositions. Compared to LiGaO2, the valence band maximum of the alloys is significantly elevated, and a fully occupied intermediate valence band appears, further raising the valence band positions. Despite the appearance of intermediate valence bands that significantly reduce the alloys' bandgap, the bandgap remains over 3.10 eV, ensuring visible light transparency. With increasing Bi composition in the alloys, the bulk modulus increases while the shear modulus gradually decreases, which improves the ductility. Moreover, the compliant elastic constants of the alloys indicate mechanical stability. These findings suggest that Li(Ga1−xBix)O2 alloys are promising flexible transparent conductive oxides, offering valuable insights for future applications. [ABSTRACT FROM AUTHOR]

The boson peak in the terahertz vibrational spectrum carries information about nano-heterogeneities in the shear modulus in glass formers. Its evolution upon heating or cooling in a supercooled liquid state may shed light on the temperature dependence of heterogeneities. For this purpose, an analysis of the light scattering spectra of supercooled glycerol in the spectral range of the boson peak and fast relaxation was carried out and the parameters of the boson peak in the temperature range 180–330 K were determined. The temperature dependent frequency of the boson peak was then expressed in terms of the mean-square amplitude of the shear modulus fluctuations. This was done using the heterogeneous elasticity theory in combination with the perturbation theory on small fluctuations and Ioffe–Regel criterion for transverse vibrations in glass formers. The contribution of structural relaxation effects to phonon damping becomes significant with increasing temperature. It is shown here that structural relaxation largely determines the temperature dependence of the mean-square fluctuations of the shear modulus at high temperatures. By solving the inverse problem, the temperature dependence of shear modulus fluctuations was obtained. It shows a rapid decrease above ∼250 K with a linear extrapolation going to zero at the so-called Arrhenius temperature TA = 350 K. Comparison with literature data on the Landau–Placzek ratio shows that they have a similar temperature dependence at T < TA, which is explained by the appearance of nanometer scale spatial heterogeneities below TA. This is confirmed by the temperature dependence of the amplitude of the boson peak. [ABSTRACT FROM AUTHOR]

In this work, the Common Model of Multi-phase Strength and Equation of State (CMMP) model was applied to tin. Specifically, calibrations of the strength-specific elements of the CMMP foundation were developed with a combination of experiments and theory, and then the model was validated experimentally. The first element of the foundation is a multi-phase analytic treatment of the melt temperature and the shear modulus for the solid phases. These models were parameterized for each phase based on ab initio calculations using the software VASP (Vienna Ab initio Simulations Package) based on density functional theory. The shear modulus model for the ambient β phase was validated with ultrasonic sound speed measurements as a function of pressure and temperature. The second element of the foundation is a viscoplastic strength model for the β phase, upon which strength for inaccessible higher-pressure phases can be scaled as necessary. The stress–strain response of tin was measured at strain rates of 10 − 3 to 3 × 10 3 s − 1 and temperatures ranging from 87 to 373 K. The Preston–Tonks–Wallace (PTW) strength model was fit to that data using Bayesian model calibration. For validation, six forward and two reverse Taylor impact experiments were performed at different velocities to measure large plastic deformation of tin at strain rates up to 10 5 s − 1 . The PTW model accurately predicted the deformed shapes of the cylinders, with modest discrepancies attributed to the inability of PTW to capture the effects of twinning and dynamic recrystallization. Some material in the simulations of higher velocity Taylor cylinders reached the melting temperature, thus testing the multiphase model because of the presence of a second phase, the liquid. In simulations using a traditional modeling approach, the abrupt reduction of strength upon melt resulted in poor predictions of the deformed shape and non-physical temperatures. With CMMP, the most deformed material points evolved gradually to a mixed solid–liquid but never a fully liquid state, never fully lost strength, stayed at the melt temperature as the latent heat of fusion was absorbed, and predicted the deformed shape well. [ABSTRACT FROM AUTHOR]

The boson peak (BP), a low-energy excess in the vibrational density of states over the Debye contribution, is often identified as a characteristic of amorphous solid materials. Despite decades of efforts, its microscopic origin still remains a mystery. Recently, it has been proposed, and corroborated with simulations, that the BP might stem from intrinsic localized modes involving one-dimensional (1D) string-like excitations ("stringlets"). We build on a theory originally proposed by Lund that describes the localized modes as 1D vibrating strings, but we specify the stringlet size distribution to be exponential, as observed in simulations. We provide an analytical prediction for the BP frequency ωBP in the temperature regime well below the observed glass transition temperature Tg. The prediction involves no free parameters and accords quantitatively with prior simulation observations in 2D and 3D model glasses based on inverse power law potentials. The comparison of the string model to observations is more uncertain when compared to simulations of an Al–Sm metallic glass material at temperatures well above Tg. Nonetheless, our stringlet model of the BP naturally reproduces the softening of the BP frequency upon heating and offers an analytical explanation for the experimentally observed scaling with the shear modulus in the glass state and changes in this scaling in simulations of glass-forming liquids. Finally, the theoretical analysis highlights the existence of a strong damping for the stringlet modes above Tg, which leads to a large low-frequency contribution to the 3D vibrational density of states, observed in both experiments and simulations. [ABSTRACT FROM AUTHOR]

Grafting polymer chains to the surface of nanoparticles overcomes the challenge of nanoparticle dispersion within nanocomposites and establishes high-volume fractions that are found to enable enhanced material mechanical properties. This study utilizes coarse-grained molecular dynamics simulations to quantify how the shear modulus of polymer-grafted nanoparticle (PGN) systems in their glassy state depends on parameters such as strain rate, nanoparticle size, grafting density, and chain length. The results are interpreted through further analysis of the dynamics of chain conformations and volume fraction arguments. The volume fraction of nanoparticles is found to be the most influential variable in deciding the shear modulus of PGN systems. A simple rule of mixture is utilized to express the monotonic dependence of shear modulus on the volume fraction of nanoparticles. Due to the reinforcing effect of nanoparticles, shortening the grafted chains results in a higher shear modulus in PGNs, which is not seen in linear systems. These results offer timely insight into calibrating molecular design parameters for achieving the desired mechanical properties in PGNs. [ABSTRACT FROM AUTHOR]

To develop special insulating paper is of great significance to promote the service life of transformers. Using molecular simulation to guide the development of special insulating paper can greatly reduce the trial-and-error rate and waste of resources in traditional experiments. The effect of different types of polysilsesquioxane (POSS) on cellulose insulating paper was investigated by using molecular simulation. This paper investigated the thermal stability and mechanical properties and electrical characteristics of caged POSS, semi-caged POSS, and ladder-like POSS doped cellulose insulating paper. The results show that POSS with all types can enhance the performance of cellulose insulating paper, and ladder-like POSS possess the best modification effect. The glass transition temperature was increased by 58 K, and the bulk modulus, shear modulus, and elastic modulus of cellulose insulating paper doped with ladder-like POSS can improve up to 27.07%, 45.67%, and 41.28%, respectively. Meanwhile, the dielectric properties of ladder-like POSS modified insulating paper are also significantly improved. The findings of this paper propose a method for the preparation of ladder-like POSS modified insulating paper, which provides theoretical guidance for the experimental preparation of special insulating paper. [ABSTRACT FROM AUTHOR]

Under decompression, disordered solids undergo an unjamming transition where they become under-coordinated and lose their structural rigidity. The mechanical and vibrational properties of these materials have been an object of theoretical, numerical, and experimental research for decades. In the study of low-coordination solids, understanding the behavior and physical interpretation of observables that diverge near the transition is of particular importance. Several such quantities are length scales (ξ or l) that characterize the size of excitations, the decay of spatial correlations, the response to perturbations, or the effect of physical constraints in the boundary or bulk of the material. Additionally, the spatial and sample-to-sample fluctuations of macroscopic observables such as contact statistics or elastic moduli diverge approaching unjamming. Here, we discuss important connections between all of these quantities and present numerical results that characterize the scaling properties of sample-to-sample contact and shear modulus fluctuations in ensembles of low-coordination disordered sphere packings and spring networks. Overall, we highlight three distinct scaling regimes and two crossovers in the disorder quantifiers χz and χμ as functions of system size N and proximity to unjamming δz. As we discuss, χX relates to the standard deviation σX of the sample-to-sample distribution of the quantity X (e.g., excess coordination δz or shear modulus μ) for an ensemble of systems. Importantly, χμ has been linked to experimentally accessible quantities that pertain to sound attenuation and the density of vibrational states in glasses. We investigate similarities and differences in the behaviors of χz and χμ near the transition and discuss the implications of our findings on current literature, unifying findings in previous studies. [ABSTRACT FROM AUTHOR]

We report results on the mechanical and structural response to shear deformation of nanodiamond superstructures in interlayer-bonded twisted bilayer graphene (IB-TBG) and interlayer-bonded graphene bilayers with randomly distributed individual interlayer C–C bonds (RD-IBGs) based on molecular-dynamics simulations. We find that IB-TBG nanodiamond superstructures subjected to shear deformation undergo a brittle-to-ductile transition (BDT) with increasing interlayer bond density (nanodiamond fraction). However, RD-IBG bilayer sheets upon shear deformation consistently undergo brittle failure without exhibiting a BDT. We identify, explain, and characterize in atomic-level detail the different failure mechanisms of the above bilayer structures. We also report the dependence of the mechanical properties, such as shear strength, crack initiation strain, toughness, and shear modulus, of these graphene bilayer sheets on their interlayer bond density and find that these properties differ significantly between IB-TBG nanodiamond superstructures and RD-IBG sheets. Our findings show that the mechanical properties of interlayer-bonded bilayer graphene sheets, including their ductility and the type of failure they undergo under shear deformation, can be systematically tailored by controlling interlayer bond density and distribution. These findings contribute significantly to our understanding of these 2D graphene-based materials as mechanical metamaterials. [ABSTRACT FROM AUTHOR]

Unconsolidated porous media are distinct from consolidated porous rocks in the negligible bulk and shear moduli. This paper is motivated by resolving the control mechanism of P-wave attenuation in the media (represented by Toyoura sands and glass beads) saturated with water. The first model is Biot theory in which longitudinal friction (arising from velocity difference between the two phases) is quantified using dynamic permeability as a function of frequency. The first model simulates phase velocity (Vp) and the ultrasonically measured quality factor (Qp) well. A second model is the transverse squirt model in which squirt is induced by pressure differential between contact of grains (COG) and the main pore space. The second model outputs unrealistic Vp and Qp. The results reveal that P-wave attenuation in unconsolidated porous media (saturated with water) is governed by longitudinal friction rather than intrapore squirt. Remarkably, low-frequency dynamic permeability is much smaller than Darcy permeability, indicating that ultrasonic P-wave is surprisingly capable of indirectly detecting the very narrow gap at COG. [ABSTRACT FROM AUTHOR]

We systematically examine the influence of varying temperature (T) over a large range in model poly(vinyl acetate) gels swollen in isopropyl alcohol. The theta temperature Θ, at which the second virial coefficient A2 vanishes, is found to be equal to within numerical uncertainty to the corresponding high molecular mass polymer solution value without cross-links, and we quantify the swelling and deswelling of our model gels relative to their size at T = Θ, as customary for individual flexible polymer chains in solutions. We also quantify the "solvent quality" dependence of the shear modulus G relative to G(T = Θ) and compare to the gel swelling factor, α. We find that all our network swelling and deswelling data can be reduced to a scaling equation of the same general form as derived from renormalization group theory for flexible linear polymer chains in solutions so that it is not necessary to invoke either the Flory–Huggins mean field theory or the Flory–Rehner hypothesis that the elastic and mixing contributions to the free energy of network swelling are separable to describe our data. We also find that changes of G relative to G(T = Θ) are directly related to α. At the same time, we find that classical rubber elasticity theory describes many aspects of these semi-dilute solution cross-linked networks, regardless of the solvent quality, although the prefactor clearly reflects the existence of network defects whose concentration depends on the initial polymer concentration of the polymer solution from which the networks were synthesized. [ABSTRACT FROM AUTHOR]

By performing coarse-grained molecular dynamics simulations, we study the effect of crosslinking and chain uncrossability on the microphase behaviors and mechanical properties of the double-network gels. The double-network systems can be viewed as two separate networks interpenetrating each other uniformly, and the crosslinks in each network are generated, forming a regular cubic lattice. The chain uncrossability is confirmed by appropriately choosing the bonded and nonbonded interaction potentials. Our simulations reveal a close relation between the phase and mechanical properties of the double-network systems and their network topological structures. Depending on the lattice size and the solvent affinity, we have observed two different microphases: one is the aggregation of solvophobic beads around the crosslinking points, which leads to locally polymer-rich domains, and the other is the bunching of polymer strands, which thickens the network edges and thus changes the network periodicity. The former is a representation of the interfacial effect, while the latter is determined by the chain uncrossability. The coalescence of network edges is demonstrated to be responsible for the large relative increase in the shear modulus. Compressing and stretching induced phase transitions are observed in the current double-network systems, and the sharp discontinuous change in the stress that appears at the transition point is found to be related to the bunching or debunching of the network edges. The results suggest that the regulation of network edges has a strong influence on the network mechanical properties. [ABSTRACT FROM AUTHOR]

We investigate the spatial correlations of microscopic stresses in soft particulate gels using 2D and 3D numerical simulations. We use a recently developed theoretical framework predicting the analytical form of stress–stress correlations in amorphous assemblies of athermal grains that acquire rigidity under an external load. These correlations exhibit a pinch-point singularity in Fourier space. This leads to long-range correlations and strong anisotropy in real space, which are at the origin of force-chains in granular solids. Our analysis of the model particulate gels at low particle volume fractions demonstrates that stress–stress correlations in these soft materials have characteristics very similar to those in granular solids and can be used to identify force chains. We show that the stress–stress correlations can distinguish floppy from rigid gel networks and that the intensity patterns reflect changes in shear moduli and network topology, due to the emergence of rigid structures during solidification. [ABSTRACT FROM AUTHOR]

The elasticity of disordered and polydisperse polymer networks is a fundamental problem of soft matter physics that is still open. Here, we self-assemble polymer networks via simulations of a mixture of bivalent and tri- or tetravalent patchy particles, which result in an exponential strand length distribution analogous to that of experimental randomly cross-linked systems. After assembly, the network connectivity and topology are frozen and the resulting system is characterized. We find that the fractal structure of the network depends on the number density at which the assembly has been carried out, but that systems with the same mean valence and same assembly density have the same structural properties. Moreover, we compute the long-time limit of the mean-squared displacement, also known as the (squared) localization length, of the cross-links and of the middle monomers of the strands, showing that the dynamics of long strands is well described by the tube model. Finally, we find a relation connecting these two localization lengths at high density and connect the cross-link localization length to the shear modulus of the system. [ABSTRACT FROM AUTHOR]

We report a combined rheology, x-ray photon correlation spectroscopy, and modeling study of gel formation and aging in suspensions of nanocolloidal spheres with volume fractions of 0.20 and 0.43 and with a short-range attraction whose strength is tuned by changing temperature. Following a quench from high temperature, where the colloids are essentially hard spheres, to a temperature below the gel point, the suspensions form gels that undergo aging characterized by a steadily increasing elastic shear modulus and slowing, increasingly constrained microscopic dynamics. The aging proceeds at a faster rate for stronger attraction strength. When the attraction strength is suddenly lowered during aging, the gel properties evolve non-monotonically in a manner resembling the Kovacs effect in glasses, in which the modulus decreases and the microscopic dynamics become less constrained for a period before more conventional aging resumes. Eventually, the properties of the gel following the decrease in attraction strength converge to those of a gel that has undergone aging at the lower attraction strength throughout. The time scale of this convergence increases as a power law with the age at which the attraction strength is decreased and decreases exponentially with the magnitude of the change in attraction. A model for gel aging in which particles attach and detach from the gel at rates that depend on their contact number reproduces these trends and reveals that the non-monotonic behavior results from the dispersion in the rates that the populations of particles with different contact number adjust to the new attraction strength. [ABSTRACT FROM AUTHOR]

The mechanical properties of the half-Heusler alloy C2CaNa using density functional theory approach as installed in Quantum Espresso software was examined. We observed that C2CaNa will be easily compressed due to the small value of its bulk modulus. The values of the lattice constant a0, elastic constants (C11, C12, C14), Young's modulus E, Piosson's ratio ν, Shear modulus G, Zener anitropy A, pressure derivative B′, and band-gap Eg were obtained. Also the Voigt approximation, Reuss approximation and the Voigt–Reuss–Hill average of the approximation were gotten. Calculated values of G/B ratio is 0.581; this shows that C2CaNa has low resistance opposed to shear deformation. The B/G ratio evaluated for C2CaNa is 1.72. This implies that C2CaNa is "brittle" in nature at ambient condition. Our calculated elastic constants (C11, C12, and C44) for C2CaNa satisfied the following mechanical stability conditions for cubic structure: C11 – C12 > 0, C44 > 0, and C11 + 2C12 > 0. The value of C12 is an indication that C2CaNa is mechanically stable. This examination gives important experiences into the primary dependability and mechanical way of behavior of this material, this will empower advance material plan and application. [ABSTRACT FROM AUTHOR]

The objective of our study was to analyze the mechanical, magnetic, elastic, electrical, and optical characteristics of the halide-based perovskite FrSnX3 (X = Cl, Br, and I) at hydrostatic pressures ranging from 0 to 6 GPa. We conducted this analysis using first-principles calculations based on density functional theory. The thermodynamic and mechanical stability of the complex FrSnX3 (X = Cl, Br, and I) were calculated based on its formation enthalpy and elastic constant characteristics. The compound was found to be ductile and stable. FrSnCl3, FrSnBr3, and FrSnI3 are all classified as semiconductors according to band calculations. Their respective bandgaps are 1.046, 0.675, and 0.485 eV, respectively. These values remain constant when hydrostatic pressure is not applied. The bandgap and density of states of the three halides were examined to observe their variations with increasing induced pressure. The bandgaps of FrSnCl3, FrSnBr3, and FrSnI3 were measured to be 0 eV at pressures of 6, 4, and 2 GPa, respectively. In addition, a comprehensive study was conducted on the optical properties of cubic perovskites FrSnX3 (X = Cl, Br, and I) under different hydrostatic pressures ranging from 0 to 6 GPa. The investigation focused on analyzing the optical absorption, reflectivity, and refractive index, as well as the imaginary and real components of the dielectric functions. Under high pressure, the compound exhibited higher absorption capabilities for all compounds within the 10–13 eV range, transforming into a conductor. This property makes it well-suited for utilization in the UV spectrum. Chlorine exhibits the greatest absorption among all chemicals, whereas iodine demonstrates the least absorption. The reflectance values of all compounds range from 12% to 16% and increase with increasing pressure. At the energy level of zero, the refractive index's real component ranges from 1.25 to 1.7, and it increases with increasing pressure. Chlorine has a relatively low refractive index compared to iodine. Bromine has the most pronounced variance. The dielectric characteristics typically vary from 4.5 to 7.5 F/m. As pressure increases, the charge storage capacities of all compounds increase. However, among these compounds, iodine has the highest capacity, while chlorine (Cl) has the lowest. The hydrostatic pressure applied to the structure FrSnX3 (X = Cl, Br, and I) causes it to become harder and more ductile. This is evident from the increasing values of the bulk, Young's, and shear modulus, as well as the elastic constants (C11 and C12). We optimized the band structure and density of states by aligning the electrons in a co-linear location and assessed the magnetic properties. The diamagnetic characteristic of the FrSnX3 compound (where X = Cl, Br, and I) remained unchanged when subjected to increasing pressure. The results indicate that the perovskite material has exceptional absorption properties, indicating a change in its behavior from a transistor to a metal. The numerical findings highlight the potential applications of this material in photovoltaic cells, ultraviolet light absorbers, and optoelectronic devices. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Diamane superlattice generated by the interlayer bonding of twisted bilayer graphene (IB-TBG) has attracted much attention thanks to its excellent properties inherited from bulk diamond, as well as the versatile modulation of physical and mechanical properties, which may open up novel electronic applications. In this work, we have systematically studied the in-plane and interlayer mechanical behaviors of IB-TBG through molecular dynamics simulations and theoretical analysis by considering different structural parameters, such as the twisted angle, stack pattern, and interlayer bonding density. It is found that interlayer bonding density plays a crucial role in determining the in-plane and interlayer shear mechanical properties of IB-TBG. Both the in-plane tensile modulus and strength follow the same linear attenuation relationship with interlayer bonding density for different twisted angles and stacked patterns, while the interlayer shear modulus increases with interlayer bonding density following the same power law, and the critical shear strain of failure linearly decreases with interlayer bonding density. Furthermore, two failure modes are observed under shear deformation, i.e., the failure of interlayer bonding (mode I) and fracture of graphene sheets (mode G). Then, theoretical prediction is carried out by considering the balance of in-plane tension and interlayer shear, which can identify the two failure modes well. The results presented herein yield useful insights for designing and tuning the mechanical properties of IB-TBG. [ABSTRACT FROM AUTHOR]

We uniaxially and shocklessly compressed an additively manufactured aluminum alloy, laser powder bed fusion (LPBF) AlSi10Mg, to peak stresses ranging from 4.4 to 14.8 GPa at peak strain rates on the order of 10 6 s − 1 via a series of magnetic loading experiments to measure the principal isentrope, yield strength, and shear modulus as a function of material orientation and applied stress. We did not observe significant anisotropy in any of the measured quantities. We found that the principal isentrope, within the uncertainty and up to our peak stress, overlaps the material's Hugoniot. We measured yield strengths and shear moduli ranging from 0.28 to 0.81 GPa and 36 to 52 GPa, respectively. Our results indicate that LPBF AlSi10Mg behaves similarly to wrought Al alloys under quasi-isentropic compression. [ABSTRACT FROM AUTHOR]

Mechanical properties of nanocrystalline NiTi shape memory alloys (SMAs) change drastically with grain size. The present contribution develops a constitutive model to reproduce the grain size dependent superelastic behavior and tensile–compressive asymmetry observed in the experiments of nanocrystalline NiTi SMAs. Effects of grain size are incorporated in the developed model by introducing the intrinsic length scale accounting for the transformation hardening as well as the grain-core and grain-boundary phase. In this work, nanocrystalline NiTi SMA is regarded as a two-phase composite material made of inclusions of the grain-core phase dispersed in the grain-boundary phase acting as a matrix. A transformation function allowing for the description of fine-grain strengthening mechanism and tensile–compressive asymmetry is proposed. In the grain-core phase, the evolution law for transformation strain during the forward and reverse transformation is determined. Besides, the constitutive relation of the grain-boundary phase is assumed to be linearly elastic. Based on the equivalent secant bulk and shear modulus of the grain-core and grain-boundary phase, the stress–strain relationship of nanocrystalline NiTi SMAs is derived by using the extended Mori–Tanaka method. Comparisons between experimental and predicted results demonstrate that the proposed model has the ability to reproduce the grain size dependent deformation and asymmetric stress–strain behavior under tension and compression of nanocrystalline NiTi SMAs. In detail, it is found that critical transformation stresses for forward and reverse transformations, dissipation energy density, transformation strain hardening, and maximum transformation strain are sensitive to the grain size and stress states. [ABSTRACT FROM AUTHOR]

The structural, elastic, and basic thermodynamic properties of hexagonal ScxAl1−xN crystals are calculated and discussed over the whole range of possible random alloys, including the transition from wurtzite to the layered hexagonal structure. Based on a review of lattice and internal parameters in combination with complete datasets of stiffness coefficients published in the literature, differing in the considered alloying intervals and the predicted structural transitions, changes in the crystal lattices caused by the substitution of aluminum by scandium atoms are discussed and illustrated. Crystal properties like the mass densities, average bond angles, and bond lengths are calculated, and the compliance coefficients, Young's modulus, shear modulus, Poisson's ratio, compressibility, and sound velocities are determined depending on the alloy composition and in relation to the orientation of crystal planes and axes. Particular attention is paid to the occurring directional anisotropies and the changes in structural and elastic properties in the alloy region of the structural transition between wurtzite and layered hexagonal ScxAl1−xN crystals. The acoustic velocities determined are used to calculate basic thermodynamic properties such as the Debye temperature, heat capacity, and minimum heat conduction, as well as to evaluate both the influence of the alloying and the structural transition on these properties. [ABSTRACT FROM AUTHOR]

The elastic properties and solid solution strengthening of several Cu alloys that may be promising for high gradient applications were studied using ab initio calculations based on density functional theory. Specifically, the temperature and solute concentration dependence of elastic properties including bulk and shear moduli, thermal expansion coefficient, and heat capacity of these alloys were calculated. We found that the bulk and shear moduli are linearly dependent on the solute concentration in the dilute regime and change significantly for different Cu alloys. The thermal expansion coefficient and heat capacity are comparatively less sensitive to solute concentrations. Solid solution strengthening is observed to be linearly correlated with the change of lattice parameter of Cu. This work provides an in-depth understanding of the elastic properties of Cu alloys, which is key for predicting their performance at high gradient in normal conducting accelerating structures. [ABSTRACT FROM AUTHOR]

The electronic and mechanical properties of a tetragonal Fe–N binary compound have been investigated under extreme pressure using density functional theory with the generalized gradient approximation. The results of formation enthalpy, phonon dispersion, and elastic stability criterion show that an Fe–N binary compound is stable up to 150 GPa. On the one hand, the electronic properties of Fe16N2 have been demonstrated by the band structures and density of states. On the other hand, the elastic constants, shear, and compressional modulus derived from elastic constants impact on compressional velocity (Vp) greatly. The shear modulus of a binary compound with N is about 14.7% lower than the data of pure Fe. The density and Vp of an Fe–N binary compound, which are closer with the value of a preliminary reference earth model (PREM), are lower than the pure Fe's, especially in the part of higher pressure. In addition, the density of an Fe–N binary compound is about 5.3% lower than the Fe's. The effect of the temperature is not considered in this work, but the varying tendency indicates that the light element N incorporating in pure Fe is helpful for building an earth's core model. [ABSTRACT FROM AUTHOR]

Viscoelastic characterization of biological tissue has significant biomedical value. In this study, we propose a wavelet-based photoacoustic viscoelastographic microscopy to characterize the viscoelasticity of tissues beneath the optical scattering depth from photoacoustic oscillation signals. Irradiated by laser pulses, biological tissue absorbs energy, expands, continues oscillating, and emits damped transient ultrasonic waves, i.e., photoacoustic oscillation signals, for a short time. A damped oscillation wavelet is applied to map photoacoustic oscillation signals into a representation of time, frequency, and decay rate. We can evaluate the frequency and decay rate of the photoacoustic oscillation signals. By considering the interrelationships among frequency, decay rate, shear modulus, and shear viscosity coefficient, we can generate images that depict the shear modulus image and shear viscosity coefficient image within the tissue. These images of the shear modulus and shear viscosity coefficient collectively form the viscoelastogram of the tissue, offering a comprehensive portrayal of its viscoelastic properties. Our study has potential biomedical value and may improve the accurate diagnosis of diseases and achieve more effective early interventions. [ABSTRACT FROM AUTHOR]

Using first-principles calculations based on density functional theory, this work investigated the mechanical, magnetic, elastic, electrical, and optical characteristics of the halide-based perovskite FrGeX3 (X = Cl, Br, I) at different hydrostatic pressures ranging from 0 to 9 GPa. It was determined that the compound FrGeX3 (X = Cl, Br, I) is stable and ductile in nature by calculating its thermodynamic and mechanical stability using the parameters of its formation enthalpy and elastic constant. When no hydrostatic pressure is applied, the band computations reveal that FrGeCl3, FrGeBr3, and FrGeI3 all remain in the semiconductor region with bandgaps of 1.14, 0.8, and 0.645 eV, respectively. The study examined how increasing induced pressure affects the bandgap and density of states of the structure for all three halides. The bandgap of FrGeCl3, FrGeBr3, and FrGeI3 fell to 0 eV at 9, 6, and 5 GPa, respectively. In addition, the optical absorption, reflectivity, refractive index, and imaginary and real components of dielectric functions were all studied in detail for cubic perovskites FrGeX3 (X = Cl, Br, I) under varying hydrostatic pressures, from 0 to 9 GPa. Due to increased pressure, the compound transitioned into a conductor and improved its absorption capabilities for all compounds within the 8–14 eV range, making it suitable for use in the UV spectrum. Cl has the largest absorption among all compounds, whereas I displays the lowest. Reflectivity ranges from around 14% to 18% for all compounds and increases w%ith pressure. The actual component of the refractive index ranges from around 2.25 to 2.7 at 0 eV and increases with pressure. Chlorine has a low refractive index, whereas iodine demonstrates the greatest. The highest fluctuation is shown for Br. The dielectric characteristics vary from around 5 to 7.5 F/m. Chlorine (Cl) has the least charge storage capacity, while iodine (I) demonstrates the most, of which both increase with pressure in all compounds. Structure FrGeX3 (X = Cl, Br, I) is hardened and made more ductile by applying hydrostatic pressure, as seen by the increasing bulk, Young's, and shear modulus values, as well as the elastic constants (C11 and C12). While the electrons were in a co-linear position, the magnetic property was also studied by optimizing the band structure and density of states. The diamagnetic property of the combination FrGeX3 (where X = Cl, Br, I) remained unchanged even when subjected to increased pressure. According to the findings, this perovskite material has remarkable absorption properties, which point to a change in its behavior from semiconductor to metal. Their potential uses in solar cells, UV absorbers, and optoelectronic devices are highlighted by these computational results. [ABSTRACT FROM AUTHOR]

Chalcogenide perovskites, renowned for their low lattice thermal conductivity, have emerged as promising candidates for thermoelectric applications. Hence, we leveraged first-principles high-throughput calculations to investigate the electrical and thermal transport properties, as well as the ductility, of the chalcogenide perovskites ABX3 (X = S, Se, Te). Candidates with 30 combinations were initially screened by bandgap screening (Eg > 0.1 eV), stability assessment (Born–Huang criterion), and ductility evaluation (Pugh's ratio: G/K < 0.571, the ratio of shear modulus G to bulk modulus K) from the MatHub-3d database (176 ABX3 crystal structures, 32 kinds of space groups, and number of atoms Natom < 40). Intriguingly, weaker chemical bonding between the A and X site atom pairs gives rise to a higher ductility in the screened quasi-ductile perovskites. Furthermore, it should be noted that the low phonon group velocities confirmed the low lattice thermal conductivity of the materials. In consequence, the identification of quasi-ductile thermoelectrics, characterized by six n-type and six p-type candidates with ZT > 0.3 at 300 K, stands as the most promising candidates for application in thermoelectrics. [ABSTRACT FROM AUTHOR]

This research proposes the effect of micropolar-Cosserat (MC) parameters (length-scale parameters and Cosserat shear modulus) on the dispersion characteristics of propagating wave modes in periodic composite panels (PCPs). These inbuilt parameters are due to the assumption of the length-scale boundary conditions that allow for capturing the micro-rotational (MR) wave mode along with the flexural ones. A significant contribution of this study is the transformation of the two-dimensional (2-D) periodic composite problem into a series of one-dimensional (1-D) ones using the MC continuum theory. The analysis employs the transfer matrix method in the framework of the state-space approach to investigate periodic systems in the eigenvalue domain. Additionally, Bloch–Floquet's periodic boundary conditions (PBCs) are applied to the unit cell to ensure the periodicity of the system. The main innovation lies in observing veering, locking, and coupling phenomena, which occur due to alterations in lamina orientation and MC parameters. Moreover, the presence of inbuilt parameters renders the dispersion characteristics highly sensitive to even minor coefficient variations, with a mere 1% change significantly impacting eigenmode fluctuations. The sudden bandgap (BG) disappearing nature could be used to identify the accurate value of the coefficient for designing and analyzing PCPs. [ABSTRACT FROM AUTHOR]

Accurate determination of high strain rate (>103 1/s) constitutive properties of soft materials remains a formidable challenge. Albeit recent advancements among experimental techniques, in particular inertial microcavitation rheometry (IMR), the intrinsic requirement to visualize the bubble cavitation dynamics has limited its application to nominally transparent materials. Here, in an effort to address this challenge and to expand the experimental capability of IMR to optically opaque materials, we investigated whether one could use the acoustic signature of the time interval between the bubble's maximum radius and first collapse time point, characterized as the bubble collapse time, to infer the viscoelastic material properties without being able to image the bubble directly in the tissue. By introducing a modified Rayleigh collapse time for soft materials, which is strongly dependent on the stiffness of the material at hand, we show that, in principle, one can obtain an order of magnitude or better estimate of the viscoelastic material properties of the soft material under investigation. Using a newly developed energy-based theoretical framework, we show that for materials stiffer than 10 kPa the bubble collapse time during a single bubble cavitation event can provide quantitative and meaningful information about the constitutive properties of the material at hand. For very soft materials (i.e., shear modulus less than 10 kPa), our theory shows that unless the collapse time measurement has very high precision and low uncertainties, the material property estimates based on the bubble collapse time only will not be accurate and require visual resolution of the full cavitation kinematics. [ABSTRACT FROM AUTHOR]

Repeated/cyclic shearing can drive amorphous solids to a steady state encoding a memory of the applied strain amplitude. However, recent experiments find that the effect of such memory formation on the mechanical properties of the bulk material is rather weak. Here, we study the memory effect in a yield stress solid formed by a dense suspension of cornstarch particles in paraffin oil. Under cyclic shear, the system evolves toward a steady state showing training-induced strain stiffening and plasticity. A readout reveals that the system encodes a strong memory of the training amplitude (γT) as indicated by a large change in the differential shear modulus. We observe that memory can be encoded for a wide range of γT values both above and below the yielding albeit the strength of the memory decreases with increasing γT. In situ boundary imaging shows strain localization close to the shearing boundaries, while the bulk of the sample moves like a solid plug. In the steady state, the average particle velocity v inside the solid-like region slows down with respect to the moving plate as γ approaches γT; however, as the readout strain crosses γT, v suddenly increases. We demonstrate that inter-particle adhesive interaction is crucial for such a strong memory effect. Interestingly, our system can also remember more than one input only if the training strain with smaller amplitude is applied last. [ABSTRACT FROM AUTHOR]

Dynamic shear-modulus data are presented for two silicone oils DC704 and DC705 for frequencies between 1 mHz and 10 kHz at temperatures covering more than five decades of relaxation-time variation. Data are fitted to the alpha part of a phenomenological model previously shown to describe well the dynamic shear modulus of squalane, which has a large beta process [Hecksher et al., J. Chem. Phys. 146, 154504 (2017)]. That model is characterized by additivity of the alpha and beta shear compliance and by a high-frequency decay of the alpha process in proportion to ω−1/2, where ω is the angular frequency. The fits of the alpha part of this model to the DC704 and DC705 data are compared to fits by a Havriliak–Negami type model, a Barlow–Erginsav–Lamb model, and a Cole–Davidson type model. At all temperatures, the best fit is obtained by the alpha part of the squalane model. This strengthens the conjecture that so-called t -relaxation, leading to high-frequency loss decays proportional to ω−1/2, is generic to the alpha relaxation of supercooled liquids [J. C. Dyre, Phys. Rev. E 74, 021502 (2006); Nielsen et al., J. Chem. Phys. 130, 154508 (2009); and Pabst et al., J. Phys. Chem. Lett. 12, 3685–3690 (2021)]. [ABSTRACT FROM AUTHOR]

We report Brillouin light scattering measurements of monoclinic CdPS 3 , a 2D layered cadmium chalcogenophosphate. By measurement of over 400 spectra in different orientations and scattering geometries, acoustic phonons are measured to determine the 13 elastic stiffness coefficients, along with longitudinal and transverse sound velocities from Brillouin frequency shifts. Because the sample was polycrystalline with a high density of planar defects, it was not possible to assign a crystal orientation to each spectrum. Instead, we determined the anisotropy in the material properties through statistical analysis, treating each spectrum as coming from a randomly sampled crystal orientation. Values of the Voigt–Reuss averages for the bulk modulus, Young's modulus, the shear modulus, and Poisson's ratio are calculated from measured stiffnesses. This work demonstrates analysis of elastic properties of a polycrystalline, monoclinic 2D layered material through statistical analysis of a significant number of spectra. [ABSTRACT FROM AUTHOR]

We report Brillouin light scattering measurements of monoclinic CdPS 3 , a 2D layered cadmium chalcogenophosphate. By measurement of over 400 spectra in different orientations and scattering geometries, acoustic phonons are measured to determine the 13 elastic stiffness coefficients, along with longitudinal and transverse sound velocities from Brillouin frequency shifts. Because the sample was polycrystalline with a high density of planar defects, it was not possible to assign a crystal orientation to each spectrum. Instead, we determined the anisotropy in the material properties through statistical analysis, treating each spectrum as coming from a randomly sampled crystal orientation. Values of the Voigt–Reuss averages for the bulk modulus, Young's modulus, the shear modulus, and Poisson's ratio are calculated from measured stiffnesses. This work demonstrates analysis of elastic properties of a polycrystalline, monoclinic 2D layered material through statistical analysis of a significant number of spectra. [ABSTRACT FROM AUTHOR]

It has long been thought that shear band (SB) formation in amorphous solids initiates from relatively "soft" regions in the material in which large-scale non-affine deformations become localized. The test of this hypothesis requires an effective means of identifying "soft" regions and their evolution as the material is deformed to varying degrees, where the metric of "softness" must also account for the effect of temperature on local material stiffness. We show that the mean square atomic displacement on a caging timescale ⟨u2⟩, the "Debye–Waller factor," provides a useful method for estimating the shear modulus of the entire material and, by extension, the material stiffness at an atomic scale. Based on this "softness" metrology, we observe that SB formation indeed occurs through the strain-induced formation of localized soft regions in our deformed metallic glass free-standing films. Unexpectedly, the critical strain condition for SB formation occurs when the softness (⟨u2⟩) distribution within the emerging soft regions approaches that of the interfacial region in its undeformed state, initiating an instability with similarities to the transition to turbulence. Correspondingly, no SBs arise when the material is so thin that the entire material can be approximately described as being "interfacial" in nature. We also quantify relaxation in the glass and the nature and origin of highly non-Gaussian particle displacements in the dynamically heterogeneous SB regions at times longer than the caging time. [ABSTRACT FROM AUTHOR]