Elastic Deformation Regime Research Articles

A method of measuring the pressure-volume relationship of mortar using a thick-walled cylinder

A method for measuring the pressure-volume relationship of mortar is presented, involving axial compression of a mortar specimen in a thick-walled cylinder (TWC). Hoop strain at the outer wall of the TWC is measured to determine the average radial stress (σr) in a mortar specimen according to TWC theory. Axial stress (σa) of mortar is measured using a load cell. The pressure (P=σa+2σr3) acting on the mortar specimen is determined from the measured axial and radial stresses. Separately, axial displacement is measured to determine the current specimen volume. TWC was designed to measure mortar pressures exceeding 100 MPa within the elastic deformation regime of the TWC. Feasibility of the proposed method and influence of friction on the measured pressure-volume relationship were examined via a finite element simulation, followed by experimental manifestation of proposed method. The proposed method was found to be effective for measuring the pressure-volume relationship of mortar.

Fiber-Reinforced Flexible Self-Healing Strain Sensor with Failure-Improving Sensitivity Recovery.

In this work, we address the inherent limitations of porous, flexible, fibrous, and self-healing strain sensors. Specifically, we tackle issues such as the fatigue failure of carbon-fibrous materials and the long-term flow and low mechanical stability of self-healing materials. We achieve this by combining self-healing carbon/PBS blends with fibrous materials, creating a fiber-reinforced self-healing composite. The self-healing carbon/PBS blends provide strain sensitivity and the ability to recover after fatigue and impact failure, while the fibers prevent the long-term flow of material and the scattering of pieces during impact and fatigue failure within the elastic deformation regime, enabling shape recovery. We fabricated composite wearable strain sensors with a viscoelastic functional layer composed of two continuous phases: (i) a self-healing polymer-carbon blend and (ii) long electrospun fibers of commercial polyurethane. This setup also eliminates the other drawbacks of bulk materials, such as nonlinearity of volt-ampere characteristics, irreversibility of deformation, and a low working factor, and allows improvement of the working factor after failure and healing. Most importantly, we discovered that hindered self-healing, like in the case of the MWCNT/PBS system, enables improvement of sensor sensitivity after large strains and failure, which is due to partial failure of the network formed by conductive particles.

Homogenization of two-dimensional materials integrating monolayer bending and surface layer effects

Two-dimensional (2D) materials hold great promise for future electronic, optical, thermal devices and beyond, underpinning which the predictability, stability and reliability of their mechanical behaviors are the fundamental prerequisites. Despite this, due to the layered crystal lattice structure, extremely high anisotropy and the independent deformation mechanism of out-of-plane bending, the proper homogenization for such materials still faces challenge. That is because the monolayer bending is of independent deformation mechanism distinct from the traditional bulk deformation which thereby brings couple stress to the bulk 2D materials, while the different interlayer constraints of bulk and surface layers bring surface layer effect. In this paper, by considering the two effects, a continuum mechanics framework for extremely anisotropic 2D materials (CM2D) is proposed, without necessities of ad hoc experiments for the unclassical parameters. Under the framework of the CM2D, beam-like deformation, plate-like deformation and indentation of 2D materials are studied to showcase its ability and applicability. An analytical expression of the effective bending rigidity is derived, which can be characterized by several dimensionless parameters. It is found that the overall bending deformations of 2D materials are controlled by the competition between the intralayer deformation mode and the interlayer shear deformation mode. Besides, the size-dependent modulus is also identified on the indentation of 2D materials at the pure elastic deformation regime, distinct from the size effect caused by plasticity. In addition, we discussed the effects of monolayer bending and surface layer on the mechanical behaviors of 2D materials. Our work not only provides guidance for the studies and applications of 2D materials, but also serves as a good example with well-defined physical meanings for the strain gradient, high-order moduli and couple stress in high-order continuum mechanics theories.

An Ultrasonic Rock Bolt Sensing Technology (I): Methodology and Laboratory Studies

Rock bolts play a critical role in ground support in mining, tunneling and construction. Being able to obtain timely information on rock bolt load condition and deformation could help immensely in safeguarding workers’ safety, optimization of ground support system, and ensuring stability and longevity of underground structures. The objective of this work was to develop a practical ultrasonic rock bolt sensing technology for monitoring axial load and deformation of a full-bodied rock bolt in both elastic and plastic deformation regimes. To this end, empirical mathematical models involving simultaneous use of times of flight of longitudinal and shear ultrasonic waves propagating along the axial direction of the rock bolt were developed, sensors were designed and fabricated, and laboratory studies were conducted. The results showed that the technology was able to measure load change, provide early detection of yield, and measure both plastic and total elongations of the rock bolt undergoing a pull test. Additionally, sectional load and elongation information could be obtained by applying the technology to rock bolts divided into sections by drilled holes along their shanks, therefore, providing the capability to assess the condition of grouted bolts at different depths within a rock mass. This work has laid the groundwork for the deployment of the technology in the field.

Comparative first principles investigation on the structural, optoelectronic and vibrational properties of strain-engineered graphene-like AlC3, BC3 and C3N monolayers

Three cardinal two-dimensional semiconductors viz., AlC3, BC3 and C3N, closely resembling the graphene structure, are intriguing contenders for emerging optoelectronic and thermomechanical applications. Starting from a critical stability analysis, this density functional theory study delves into a quantitative assessment of structural, mechanical, electronic, optical, vibrational and thermodynamical properties of these monolayers as a function of biaxial strain (ε) in a sublinear regime (−2%⩽ε⩽4%) of elastic deformation. The structures with cohesive energies slightly smaller than graphene, manifest exceptional mechanical stiffness, flexibility and breaking stress. The mechanical parameters have been deployed to further cultivate acoustic attributes and thermal conductivity. The hexagonal structures with mixed ionic-covalent molecular bonds have indirect electronic band-gap and work-function acutely sensitive to ε . Dispersions of optical dielectric function, energy loss, refractive index, extinction coefficient, reflectivity, absorption coefficient and conductivity are deciphered in the UV–Vis–NIR regime against strain, where particular frequency bands featuring high polarization, dissipation, absorbance or reflectance are identified. Phonon band-structure and density of states testify dynamic stability in the ground state for all systems except the compressed ones. A comprehensive group theoretical analysis is performed to cultivate rotational; infrared and Raman-active modes, and the nature of molecular vibrations is delineated. The red-shifting of phonon bands and E2g/A1g Raman peaks with increasing ε , associates estimation of Grüneisen parameter. Finally, strain-induced alterations of thermodynamic quantities such as entropy, enthalpy, free energy, heat capacity and Debye temperature are studied, followed by a molecular dynamics-based stability assessment under canonical ensemble.

Probing the interactions of the HIV-1 matrix protein-derived polybasic region with lipid bilayers: insights from AFM imaging and force spectroscopy.

The human immunodeficiency virus type 1 (HIV-1) matrix protein contains a highly basic region, MA-HBR, crucial for various stages of viral replication. To elucidate the interactions between the polybasic peptide MA-HBR and lipid bilayers, we employed liquid-based atomic force microscopy (AFM) imaging and force spectroscopy on lipid bilayers of differing compositions. In 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayers, AFM imaging revealed the formation of annulus-shaped protrusions upon exposure to the polybasic peptide, accompanied by distinctive mechanical responses characterized by enhanced bilayer puncture forces. Importantly, our AFM-based force spectroscopy measurements unveiled that MA-HBR induces interleaflet decoupling within the cohesive bilayer organization. This is evidenced by a force discontinuity observed within the bilayer's elastic deformation regime. In POPC/cholesterol bilayers, MA-HBR caused similar yet smaller annular protrusions, demonstrating an intriguing interplay with cholesterol-rich membranes. In contrast, in bilayers containing anionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine (POPS) lipids, MA-HBR induced unique annular protrusions, granular nanoparticles, and nanotubules, showcasing its distinctive effects in anionic lipid-enriched environments. Notably, our force spectroscopy data revealed that anionic POPS lipids weakened interleaflet adhesion within the bilayer, resulting in interleaflet decoupling, which potentially contributes to the specific bilayer perturbations induced by MA-HBR. Collectively, our findings highlight the remarkable variations in how the polybasic peptide, MA-HBR, interacts with lipid bilayers of differing compositions, shedding light on its role in host membrane restructuring during HIV-1 infection.

Model for an elastic-plastic spherical contact with the DMT adhesion

This paper studied the elastic-plastic spherical contact with the DMT adhesion, and presented an improved smooth formula for the local separation outside the elastic-plastic contact area on the KE empirical formula. The elastic-plastic local separation was equal to the elastic local separation with the same contact area and a equivalent elastic contact displacement. When the contact entered the elastic deformation regime, due to zero residual plastic contact displacement, the present formula for the elastic-plastic local separation could reduce to that for the elastic local separation naturally. Utilizing the present formula for the local separation, a unified adhesion model suitable for between the elastic and elastic-plastic spherical contact with the DMT adhesion was presented. In comparison with the KE adhesion model, the present adhesion model had higher fitting accuracy and could approach the Bradley’s value as the contact displacement approached zero well, which was a good approximation to the complete integration calculation. The present adhesion model could be used for the study of the elastic and elastic-plastic spherical contact with adhesion.

Large deflection deformation behavior of a Zr-based bulk metallic glass for compliant spinal fixation application

A novel compliant spinal fixation designed based on the concept of compliant mechanisms can reduce the stress-shielding effect and adjacent segment degeneration (ASD) effectively, but propose higher requirements for the properties of the used materials. Bulk metallic glasses (BMGs), as a kind of young biomaterials, exhibiting excellent comprehensive properties, which are attractive for compliant spinal fixation. Here, according to the practical service condition of the basic elements in compliant spinal fixation, large deflection deformation behaviors of Zr61Ti2Cu25Al12 (at.%, ZT1) BMG beam, including elastic, yielding and plastic were investigated systematically. It was shown that the theoretical nonlinear analytical solution curve as the benchmark not only with the capacity to predict the nonlinear load-deflection relation within the elastic deformation regime, but also assists to capture the yielding event roughly, which can be used as a powerful design tool for engineers. To capture the beginning of the yielding event exactly, bending proof strength (σp,0.05%) accompanied with tiny permanent strain of 0.05% was proposed and determined for BMGs in biomedical implant applications, which is of significance for setting the allowable operating limits of the basic flexible elements. By approach of interrupted loading-unloading cycles, plastic deformation driven by the bending moment can be classified into two typical stages: the initial stage which mainly characterized by the nucleation and intense interaction of abundant shear bands when the plastic strain below the critical value, and the second stage which dominated by the progressive propagation of shear bands and coupled with the emergence of shear offsets on tensile side. The plasticity of BMG beam structures depends on the BMG's inherent plastic zone size (rp). When the half beam thickness less than that of the rp, the plastic deformation of BMGs will behave in a stable manner, which can be acted as the margin of safety effectively.

Post-fabrication tuning of origami-inspired mechanical metamaterials based on Tachi-Miura Polyhedron

We investigate the reconfigurability and tunability of the tessellation of Tachi-Miura Polyhedron (TMP), an origami-based cellular structure composed of bellows-like unit cells. Lattice-based three-dimensional mechanical metamaterials have recently received significant scientific interest due to their superior and unique mechanical performance compared to conventional materials. However, it is often challenging to achieve tunability and reconfigurability from these metamaterials, since their geometry and functionality tend to be pre-determined in the design and fabrication stage. Here, we utilize TMP's highly versatile phase-transforming and tessellating capabilities to design reconfigurable metamaterial architecture with tunable mechanical properties. The theoretical analyses and experiments with heat processing discover the wide range of the in-situ tunability of the metamaterial – specifically orders of magnitude change in effective density, Young's modulus, and Poisson's ratio – after its fabrication within the elastic deformation regime. We also witness a rather unique behavior of the inverse correlation between effective density and stiffness. This mechanical platform paves the way to design the metamaterial that can actively adapt to various external environments.

Dynamic Compressive and Flexural Behaviour of Re-Entrant Auxetics: A Numerical Study.

Re-entrant auxetics offer the potential to address lightweight challenges while exhibiting superior impact resistance, energy absorption capacity, and a synclastic curvature deformation mechanism for a wide range of engineering applications. This paper presents a systematic numerical study on the compressive and flexural behaviour of re-entrant honeycomb and 3D re-entrant lattice using the finite element method implemented with ABAQUS/Explicit, in comparison with that of regular hexagonal honeycomb. The finite element model was validated with experimental data obtained from the literature, followed by a mesh size sensitivity analysis performed to determine the optimal element size. A series of simulations was then conducted to investigate the failure mechanisms and effects of different factors including strain rate, relative density, unit cell number, and material property on the dynamic response of re-entrant auxetics subjected to axial and flexural loading. The simulation results indicate that 3D re-entrant lattice is superior to hexagonal honeycomb and re-entrant honeycomb in energy dissipation, which is insensitive to unit cell number. Replacing re-entrant honeycomb with 3D re-entrant lattice leads to an 884% increase in plastic energy dissipation and a 694% rise in initial peak stress. Under flexural loading, the re-entrant honeycomb shows a small flexural modulus, but maintains the elastic deformation regime over a large range of strain. In all cases, the compressive and flexural dynamic response of re-entrant auxetics exhibits a strong dependence on strain rate, relative density, and material property. This study provides intuitive insight into the compressive and flexural performance of re-entrant auxetics, which can facilitate the optimal design of auxetic composites.

Oxidation of a refractory high entropy alloy (RHEA) at moderate temperatures for wear related applications

This study was initiated to exploit the poor oxidation resistance of a RHEA, namely HfNbTaTiZr, to enhance its surface hardness and wear performance. In this regard, samples sliced from vacuum arc melted HfNbTaTiZr ingots having a hardness of ∼400 HV were held at two different temperatures (450 and 600 °C) for 3 h in air. The structural examinations conducted by using X-ray diffraction (XRD) and Raman analysis along with an energy dispersive spectrometer (EDS) equipped scanning electron microscope (SEM) revealed that the samples were covered with a complex HfNbTaTiZrO11 type oxide layer (OL) having the hardness of ∼1550 HV. The average surface roughness (Ra) and the thickness of the OLs were measured as ∼0.13 μm and ∼ 1 μm after oxidation at 450 °C and ∼ 0.29 μm and ∼ 8 μm after oxidation at 600 °C, respectively. The protective nature of the OLs was confirmed by dry sliding wear tests employed at room temperature against alumina balls under a contact pressure of ∼0.5 GPa. This led to 240- and 45-times higher wear resistance for the samples oxidized at 450 and 600 °C, respectively. During the wear tests, the untreated sample was exposed to severe wear owing to the accumulation of heavy plastic deformation at the contact surface, while for the oxidized samples wear progressed in an elastic deformation regime on the OLs resulting in mild wear. However, the roughness of the OLs played a crucial role on the wear resistance of the oxidized samples, so that the oxidation temperature of 600 °C, which imposed a higher Ra value, resulted in a reduction in wear resistance when compared to the oxidation temperature of 450 °C, which formed a smoother OL.

Microstructure evolution and mechanical behavior of additively manufactured CoCrFeNi high-entropy alloy fabricated via cold spraying and post-annealing

In this work, equiatomic CoCrFeNi high-entropy alloy (HEA) was fabricated by solid-state cold spray additive manufacturing technology and then post-spray annealed at the temperature range of 500–1000 °C for 2 h. By adjusting the annealing temperature, four types of deposits (i.e., as-sprayed, recovered (500 °C), partially recrystallized (700 °C), and fully recrystallized (1000 °C) deposits) were obtained, and their microstructure, compressive and tensile properties were systematically explored. The as-sprayed deposit exhibited high compressive yield strength due to the dislocation strengthening and grain boundary strengthening effects but fractured within the elastic deformation regime in the tensile test. Such significant tension-compression asymmetry can be attributed to the difference in the sensitivity of the deposit to interior defects (i.e., pores and particle boundaries) under tensile and compressive loads. Only recover annealing hardly influenced the microstructure and mechanical properties of the deposits. While recrystallization annealing could trigger enhanced interface diffusion and the resultant metallurgical bonding, as evidenced by the improved deposit density and less visible interparticle interfaces. The partially recrystallized and fully recrystallized deposits exhibited an excellent combination of compressive strength and ductility. While the fully recrystallized deposit exhibited almost equal tensile and compressive yield strength and the best recovery of tensile ductility, indicating the weakened tension-compression asymmetry.

Simulación de fenómenos de daño para metamateriales

Metamaterials are generated from an interrelated set of cells and can present a macroscopic behaviour that differs from the one that characterizes its basic constituents. Modelling the influence that the damage and fracture of the elemental constituents have in the macroscopic properties of the metamaterial is relevant for its mechanical analysis. Altering the resistant behaviour of the elements (changing their longitudinal elastic modulus), it is possible to approximate the effect of the damage in the complete structure. It is considered as valid the substitution of the damage and plastic deformation phenomena by intermediate states contained in the linear elastic deformation regime. Each state is characterized by the elastic module of the element, whose geometry remains unmodified. In an iterative process, when the induced stress in the elements is greater than the one stablished as the limit, they progress through the different states, diminishing their elastic modulus until they are considered as fractured and are eliminated from the structure. Mass effects are ignored, and a stress-free structure is implemented to calculate each iteration. A simple algorithm is presented to simulate the effect of damage in metamaterial structures, applicable to any finite element software.

Mechanical responses of Al20.4Mo10.5Nb22.4Ta10.1Ti17.8Zr18.8 nanopillar under uniaxial compression

The mechanical responses of crystallographic orientations [001], [110], and [111] of Al 20.4 Mo 10.5 Nb 22.4 Ta 10.1 Ti 17.8 Zr 18.8 refractory high entropy alloy (RHEA) nanopillars under the uniaxial compression are investigated by the MD simulation using 2NN MEAM potential. The [001]-orientated nanopillar shows the widest elastic deformation regime with the yielding strain about 0.075, compared to the other two nanopillars with the yielding strains about 0.03~0.04. The strength of [111]-oriented nanopillar is the highest, which is about 36.3% and 117% higher than those of [001]- and [110]-oriented nanopillars, respectively. After the strain exceeds the ultimate one, the stress gradually declines with the increasing strain, and then displays small flow stress oscillation during plastic deformation, indicating the stresses saturate at the quasi-steady flow stress. For the [001]-orientated nanopillar, the extent of BCC-HCP phase transition is the most significant at strains below the flow stress regime. From strain 0 to the beginning of the flow stress regime, the local structural transition is the main deformation mechanism, and the dislocation slip becomes the dominant deformation mechanism within the flow stress regime. For the [110]-orientated nanopillar, the dislocation nucleates at the strain between the yielding and ultimate strains, and then the dislocation density increases sharply with the increasing strain until the occurrence of the dislocation slip. The dislocation slip and deformation twinning are two main deformation mechanisms for the [110]-orientated nanopillar. For the [111]-orientated nano-pillar, the dislocation nucleates at the strain larger than the ultimate strain when the stress undergoes an abrupt drop. After the dislocation nucleation, the dislocation density shows a distinct increase during the stress drop, leading to the appearance of dislocation lines. In the flow stress regime, the dislocation density gradually decreases from the maximum value about 600.17 10 19 m -2 to zero with the increasing strain. Local shear strain of [110]-oriented Al20.4Mo10.5Nb22.4Ta10.1Ti17.8Zr18.8 nanopillar during the compression • The mechanical responses of crystallographic orientations [001], [110], and [111] of Al 20.4 Mo 10.5 Nb 22.4 Ta 10.1 Ti 17.8 Zr 18.8 refractory high entropy alloy nanopillars under the uniaxial compression • 2NN MEAM potential parametrization process for the Al-Mo-Nb-Ta-Ti-Zr system using DFT calculation data. • Polyhedral template matching (PTM) method for monitoring the local structural transformation. • Atomic local shear strain for observing dislocation slip band growth • dislocation extraction algorithm (DXA) results for dislocation nucleation and evolution

Pyrene-Based Macrocrosslinkers with Supramolecular Mechanochromism for Elastic Deformation Sensing in Hydrogel Networks

Excimer-containing polymers with supramolecular mechanochromism are an attractive and well-investigated class of mechanoresponsive materials. However, only recently steps toward mechanophore-like mechanochromic systems that are anchored within the parent polymer structure and that show defined optical transitions on the molecular scale have been reported. However, the multi-step syntheses of these constructs are tedious. Here we report the development of a series of pyrene-based macrocrosslinkers that display supramolecular mechanochromism and are readily synthesized from mostly commercial reagents. We incorporate the water-soluble macrocrosslinkers in hydrogel networks and demonstrate their reversible mechanochromic behavior in the elastic deformation regime.

Impact of welding simulated heat treatment on hydrogen embrittlement behavior of high-strength fine-grained steels

Hydrogen embrittlement (HE) sensitivity of S690QL structural steel and X80 pipeline steel in both as delivered and welding simulated heat treatment conditions have been investigated by slow strain rate test (SSRT) with in-situ hydrogen charging. Both investigated steel grades show low strength losses, however, high ductility losses, represented by losses in total elongation and area reduction after in-situ hydrogen charging at a constant current density. The resulting diffusive hydrogen contents after charging are associated with the material microstructure, which are 2–3 ppm for S690QL and 1–2 ppm for X80. The lath martensite dominated microstructure in heat-treated S690QL specimens revealed extremely high HE sensitivity as demonstrated by fracture occurring within the elastic deformation regime. Hydrogen induced damage was found associated with the brittle nature of the quenched lath martensite, the severe grain coarsening, and the large fraction of high angle grain boundaries. The X80 pipeline steel reveals a transition from granular bainite dominated microstructure to lath bainite/martensite dominated microstructure after welding simulated heat treatment. The uptake of diffusive hydrogen during the in-situ charging process of X80 specimens was less compared to S690QL specimens, which was also desorbed at higher temperatures as characterized by hydrogen thermal desorption analysis. The results suggest a controlled bainitic/martensitic microstructure transformation with designed precipitation hardening would contribute to both strength enhancement and the suppression of hydrogen mobility.

Evolution of local densities during shear banding in Zr-based metallic glass micropillars

Shear bands (SBs) play an important role in plastic deformation of metallic glasses (MGs), but the evolving mechanism of SBs is still elusive. We study the structural formation and evolution of SBs inside MGs using synchrotron X-ray nano-computed tomography with the combination of high-resolution transmission electron microscopy. It is found that discrete anisotropic low-density regions, as manifestation of the activations of accumulated shear transformation zones, are created in the elastic deformation regime, which form SBs of density fluctuations under large plastic deformation. With further increasing plastic strain, the thickness of SBs increases from ∼ 105 nm to ∼ 180 nm, and their local densities decrease. Before the formation of cracks, the low-density regions in SBs gradually evolve into nanovoids with the matrix around densified. Compared to the unaffected matrix, densified regions with more crystal-like order (CLO) structure appear around thick SBs of severe bond breaking, and the densification is more apparent near crack surface with CLO structure further increasing. The results are significant for understanding the structural evolution during shear banding and plastic deformation mechanism for glassy materials.

A Lagrangian Hencky-type non-linear model suitable for metamaterials design of shearable and extensible slender deformable bodies alternative to Timoshenko theory

Among the most studied models in mathematical physics, Timoshenko beam is outstanding for its importance in technological applications. Therefore it has been extensively studied and many discretizations have been proposed to allow its use in the most disparate contexts. However, it seems to us that available discretization schemes present some drawbacks when considering large deformation regimes. We believe these drawbacks to be mainly related to the fact that they are formulated without keeping in mind the mechanical phenomena for describing which Timoshenko continuum model has been proposed. Therefore, aiming to analyze the deformation of complex plane frames and arches in elastic large displacements and deformation regimes, a novel intrinsically discrete Lagrangian model is here introduced whose phenomenological application range is similar to that for which Timoshenko beam has been conceived. While being largely inspired by the ideas outlined by Hencky in his renowned doctoral dissertation, the presented approach overcomes some specific limitations concerning the stretch and shear deformation effects. The proposed model is applied to get the solutions for some relevant benchmark tests, both in the case of arch and frame structures. It is proved that, also when shear deformation effects are of relevance, the enriched, yet simple, model and numerical computation scheme herein proposed can be profitably used for efficient structural analyses of non-linear mechanical systems in rather nonstandard situations.

Refractive indices of shock-induced polymorphic Gd3Ga5O12 single crystals

Gd 3 Ga 5 O 12 single crystals [gadolinium gallium garnet (GGG)] were shock compressed to elastic deformation, elastoplastic transformation, and structural phase-transition regimes with the corresponding single, two-wave, and three-wave structures. Velocity profiles at the front interface and the rear free surface of the sample are measured by a Doppler pin system. Results of these measurements are analyzed in detail, and the refractive index, n, at 1550 nm is obtained as a function of shock pressure or density. Incorporating previously published single-wave data above 100 GPa, characteristic variations in the refractive index are presented and discussed within the context of shock-induced polymorphism of the GGG.

Measurement of the mechanical properties of silver and enamel thick films using nanoindentation

AbstractAnalyzing material properties of thick film multilayers deposited onto soda‐lime silicate glass raises several challenges since these layers can exhibit complex multiphase microstructures. The mechanical properties of sintered silver and glass enamel thick films have been investigated using nanoindentation methods to provide deeper understanding of the composite stack in‐service failure mechanisms. The spatial distribution of the Young's modulus and hardness have been studied on the cross section of the layers to avoid the influence of surface roughness and underlying glass substrate. The apparent indentation fracture toughness of the layers has been evaluated via SEM and high‐resolution surface topography images of the hardness imprints. A modified Berkovich indenter has been employed to study the elastic and plastic deformation regimes while the fracture deformation regime has been investigated using a cube‐corner indenter. In the enamel layer, copper chromite spinel pigments were found to provide a beneficial effect on the films mechanical performance due to their significantly higher elastic, hardness, and toughness properties compared to the surrounding amorphous phase. The amorphous phase of the enamel layer and the glass substrate has comparable mechanical properties, while the fracture toughness of sintered silver is higher, partially explaining the failure initiation in the enamel layer.