Setting Times of Early-Age Mortars Determined from Evolution Curves of Poisson’s Ratio

Setting times, as the early-age properties of cement-based materials, are important properties to ensure the quality and long-term performance of engineering structures. To determine the initial and final setting times of cementitious materials, the compressive wave velocity and shear wave velocity of six early-age mortar samples were monitored. Their time evolution curves of Young’s modulus, shear modulus, bulk modulus, and Poisson’s ratio were then calculated and analyzed. The signature times of the derivatives of the Poisson’s ratio evolution curves correlate well with the initial and final setting times, and the remarkably high coefficient of determination values relative to the data from this study are higher than those presented in the current literature. The proposed derivative method on the Poisson’s ratio evolution curve is as good as the derivative methods from vs. evolution curves used by prior studies for the estimation of both the initial and final setting times of the early-age properties of cement-based materials. The formation and subsequent disappearance of ettringite of low Poisson’s ratio were postulated to cause the initial dip in the Poisson’s ratio evolution curves.     

Study on a Chiral Structure with Tunable Poisson’s Ratio

A chiral structure with a negative Poisson’s ratio containing a hollow circle with varying diameters was designed, and the finite element method was used to investigate the variation in the Poisson’s ratio when the hollow circle diameter was varied (d = 0, 1, 2, 3, and 4 mm). The simulation results showed that the Poisson’s ratio was sensitive to the hollow circle diameter, and the minimum Poisson’s ratio was −0.43. Three specimens with different hollow circle diameters (d′ = 0, 1, and 3 mm) were 3D-printed from thermoplastic polyurethane, and the Poisson’s ratio and equivalent elastic modulus were measured. In the elastic range, the Poisson’s ratio increased and the equivalent elastic modulus decreased as the hollow circle diameter increased. The simulation and experimental results showed good agreement. The proposed structure is expected to be applicable to protective sports gear owing to its high energy absorption and the fact that its properties can be modified as required by adjusting the geometric parameters of the unit cell.     

Mechanical Parameters of Leather in Relation to Technological Processing of the Footwear Uppers

This paper aimed to define two critical mechanical properties of leather—Young’s modulus and Poisson ratio—essential to the virtual simulation of the behaviour of the footwear uppers against the manufacturing operations of stitching and perforating. The following technological aspects were considered to analyse the materials from manufacturing conditions point of view: the number of layers (one layer and two layers), the nature of the materials used for uppers subgroups (calfskin-outer upper, sheep leather-lining, polyester knitted fabric-lining), the overlapping width in the stitching area, the number of parallel stitches (single stitch and double stitch), the punching interval and the type of perforations (simple and with eyelets), resulting in nine kinds of samples. Furthermore, the elasticity (Young’s modulus) and lateral contraction (Poisson’s ratio) were calculated during the tensile strength analysis performed on the SATRA STM 466 equipment. Both mechanical parameters are essential to simulate the behaviour of the virtual footwear prototypes in various conditions.     

A Comparative Analysis of Selected Methods for Determining Young’s Modulus in Polylactic Acid Samples Manufactured with the FDM Method

The objective of this study was to compare three methods for determining the Young’s modulus of polylactic acid (PLA) and acrylonitrile-butadiene-styrene (ABS) samples. The samples were manufactured viathe fused filament fabrication/fused deposition modeling (FFF/FDM) 3D printing technique. Samples for analysis were obtained at processing temperatures of 180 °C to 230 °C. Measurements were performed with the use of two nondestructive techniques: the impulse excitation technique (IET) and the ultrasonic (US) method. The results were compared with values obtained in static tensile tests (STT), which ranged from 2.06 ± 0.03 to 2.15 ± 0.05 GPa. Similar changes in Young’s modulus were observed in response to the processing temperatures of the compared methods. The values generated by the US method were closer to the results of the STT, but still diverged considerably, and the error exceeded 10% in all cases. Based on the present findings, it might be concluded that the results of destructive and nondestructive tests differ by approximately 1 GPa.     

The Influence of Density on the Value of Young’s Modulus for Dry Ice

The efficiency of material consumption is an important consideration for production processes; this is particularly true for processes that use waste materials. Dry ice extrusion serves as a good example. An examination of the literature on this subject leads to an observation that the commercially available machines for dry ice compression are characterized by a high value of working force. Consequently, the effectiveness of the source consumption, electric energy and carbon dioxide, is very low. The subject of the experimental research presented in the article is the influence of the density of dry ice on the value of Young’s modulus. The first part of the article presents the test methodology and the special test stand that was developed to accommodate the unique characteristics of solid-state carbon dioxide. The test results present the characteristics of compaction and relaxation used as the basis for determining the value of Young’s modulus. Based on the test results obtained for various material density values, the characteristics of Young’s modulus are developed and graphed as a function of the density. The presented results are important for furthering the research on the development of extrusion and compaction processes; for example, using the Drucker–Prager/Cap model for the purpose of optimizing the geometrical characteristics of the work assembly components.     

Evaluation of the Equivalent Mechanical Properties of Lattice Structures Based on the Finite Element Method

Lattice structures have excellent mechanical properties and can be designed by changing the cellular structure. However, the computing scale is extremely large to directly analyze a large-size structure containing a huge number of lattice cells. Evaluating the equivalent mechanical properties instead of the complex geometry of such lattice cells is a feasible way to deal with this problem. This paper aims to propose a series of formulas, including critical structural and material parameters, to fast evaluate the equivalent mechanical properties of lattice structures. A reduced-order model based on the finite element method and beam theory was developed and verified by comparing it with the corresponding full model. This model was then applied to evaluate the equivalent mechanical properties of 25 types of lattice cells. The effects of the material Young’s modulus and Poisson’s ratio, strut diameter, cell size, and cell number on those equivalent mechanical properties were investigated and discussed, and the linear relationship with the material parameters and the non-linear relationship with the structural parameters were found. Finally, a series of analytical-fitting formulas involving the structural and material parameters were obtained, which allows us to fast predict the equivalent mechanical properties of the lattice cells.     

Negative Poisson’s Ratio-Spacer Design and Its Thermo-Mechanical Coupling Analysis Considering Specific Force Output

Aiming at the problems of a complex structure or poor controllability of the existing bearing preload control devices, a method of self-regulation via a negative Poisson’s ratio (NPR) spacer is proposed. Firstly, the principle of preload automatic adjustment at the bearing operation was introduced and the NPRs with three types of cell structures were analyzed. Furthermore, a thermo-mechanical coupling analysis model of the NPR spacer was established and the deformation and force output characteristics of the NPR spacer were studied and experimentally verified. It is found that the concave hexagonal cell structure has the optimal deformation characteristics for bearing preload adjustment. When the temperature is considered, the absolute value of Poisson’s ratio of the NPR spacer decreases as the speed increases and the elongation of the NPR spacer and the output forces are much larger than those without temperature consideration. With the increase in temperature or rotating speed, the axial elongation and output forces of the NPR spacer increases while the effect of temperature is relatively larger.     

Apparent Young’s Modulus of the Adhesive in Numerical Modeling of Adhesive Joints

This article is an evaluation of the phenomena occurring in adhesive joints during curing and their consequences. Considering changes in the values of Young’s modulus distributed along the joint thickness, and potential changes in adhesive strength in the cured state, the use of a numerical model may make it possible to improve finite element simulation effects and bring their results closer to experimental data. The results of a tensile test of a double overlap adhesive joint sample, performed using an extensometer, are presented. This test allowed for the precise determination of the shear modulus G of the cured adhesive under experimental conditions. Then, on the basis of the research carried out so far, a numerical model was built, taking the differences observed in the properties of the joint material into account. The stress distribution in a three-zone adhesive joint was analyzed in comparison to the standard numerical model in which the adhesive in the joint was treated as isotropic. It is proposed that a joint model with three-zones, differing in the Young’s modulus values, is more accurate for mapping the experimental results.     

Relationship between Young’s Modulus and Planar Density of Unit Cell,Super Cells (2 × 2 × 2), Symmetry Cells of Perovskite (CaTiO3) Lattice

Calcium titanate-CaTiO₃ (perovskite) has been used in various industrial applications due to its dopant/doping mechanisms. Manipulation of defective grain boundaries in the structure of perovskite is essential to maximize mechanical properties and stability; therefore, the structure of perovskite has attracted attention, because without fully understanding the perovskite structure and diffracted planes, dopant/doping mechanisms cannot be understood. In this study, the areas and locations of atoms and diffracted planes were designed and investigated. In this research, the relationship between Young’s modulus and planar density of unit cell, super cells (2 × 2 × 2) and symmetry cells of nano CaTiO₃ is investigated. Elastic constant, elastic compliance and Young’s modulus value were recorded with the ultrasonic pulse-echo technique. The results were C₁₁ = 330.89 GPa, C₁₂ = 93.03 GPa, C₄₄ = 94.91 GPa and E = 153.87 GPa respectively. Young’s modulus values of CaTiO₃ extracted by planar density were calculated 162.62 GPa, 151.71 GPa and 152.21 GPa for unit cell, super cells (2 × 2 × 2) and symmetry cells, respectively. Young’s modulus value extracted by planar density of symmetry cells was in good agreement with Young’s modulus value measured via ultrasonic pulse-echo.     

X-ray Diffraction Analysis and Williamson-Hall Method in USDM Model for Estimating More Accurate Values of Stress-Strain of Unit Cell and Super Cells (2 × 2 × 2) of Hydroxyapatite,Confirmed by Ultrasonic Pulse-Echo Test

Taking into account X-ray diffraction, one of the well-known methods for calculating the stress-strain of crystals is Williamson-Hall (W–H). The W-H method has three models, namely (1) Uniform deformation model (UDM); (2) Uniform stress deformation model (USDM); and (3) Uniform deformation energy density model (UDEDM). The USDM and UDEDM models are directly related to the modulus of elasticity (E). Young’s modulus is a key parameter in engineering design and materials development. Young’s modulus is considered in USDM and UDEDM models, but in all previous studies, researchers used the average values of Young’s modulus or they calculated Young’s modulus only for a sharp peak of an XRD pattern or they extracted Young’s modulus from the literature. Therefore, these values are not representative of all peaks derived from X-ray diffraction; as a result, these values are not estimated with high accuracy. Nevertheless, in the current study, the W-H method is used considering the all diffracted planes of the unit cell and super cells (2 × 2 × 2) of Hydroxyapatite (HA), and a new method with the high accuracy of the W-H method in the USDM model is presented to calculate stress (σ) and strain (ε). The accounting for the planar density of atoms is the novelty of this work. Furthermore, the ultrasonic pulse-echo test is performed for the validation of the novelty assumptions.     

The Influence of the Physical-Mechanical Parameters of Rock on the Extent of the Initial Failure Zone under the Action of an Undercut Anchor

This paper presents the results of a numerical FEM (Finite Element Method) simulation of the formation of a rock failure zone in its initial stage of development. The influence of rock parameters, such as the Young’s modulus, Poisson’s ratio and friction factor of the rock in the contact zone with the working surface of the undercut anchor head, were taken into account. The obtained results of FEM simulations were compared with the results of field tests conducted in Polish mining plants extracting rock raw materials.     

Young’s Modulus and Vickers Hardness of the Hydroxyapatite Bioceramics with a Small Amount of the Multi-Walled Carbon Nanotubes

The Vickers hardness and Young’s modulus of the hydroxyapatite (HA) bioceramics with a small amount of the multi-walled carbon nanotubes (MWCNTs) were studied by using ultramicrotester Shimadzu for dynamic tests DUH-211. Small concentrations of MWCNTs were from 0.05 to 0.5 wt.%. The argon inert atmosphere and vacuum condition were taken for the prevention of the MWCNTs oxidation. The Brunauer–Emmett–Teller (BET) surface area S_BET of the HA-MWCNTs composites was determined by thermal adsorption-desorption of nitrogen. It was found that for HA-MWCNTs sintered in the Ar atmosphere, an increase in the concentration of nanotubes up to 0.5 wt.% leads to a decrease in porosity near 3 times in comparison to HA without MWCNTs additives. The small amount of additives of multi-walled carbon nanotubes leads to an increase in hardness of 1.3 times and compression strength of composite and compression strength of composite that is comparable in absolute values with the literature data of enamel hardness (3–5 GPa) and compression strength (95–370 MPa). The absolute values increase close to linearly with the increase of nanotube concentrations. The Young’s modulus of sintered composite slightly changes with the variation of concentrations of nanotubes and close to the enamel (75–100 GPa). The ratio of plastic work to total work and the ratio of elastic (reversible) work to the total work of deformation of composite HA/MWCNTs are practically constant at a studied range of MWCNTs concentration. The additives of the multi-walled carbon nanotubes lead to both an increase in the elasticity index of ~1.5 times and an increase in the resistance to plastic deformation of ~3 times, which improved the tribological performance of the surface. Plastic and elastic (reversible) work slightly changed.     

Grain-to-Grain Interaction Effect in Polycrystalline Plain Low-Carbon Steel within Elastic Deformation Region

A grain is surrounded by grains with different crystal orientations in polycrystalline plain low-carbon steel. The grain is constrained by its adjacent grains in the tension process. The interaction of the grain with the adjacent grains was investigated within the elastic deformation region. The following results have been obtained: (1) the Young’s modulus of a grain without consideration of grain-to-grain interaction is denoted as the inherent Young’s modulus; when the inherent Young’s modulus of a grain is equal to the Young’s modulus of the bulk material, there is almost no interaction between the grain and its adjacent grains; when a grain has a great difference between its inherent Young’s modulus and the Young’s modulus of the bulk material, its grain-to-grain interactions increase significantly; (2) the grain-to-grain interaction is mainly caused by the difference in the inherent Young’s modulus between the grain and its adjacent grains; the misorientation angle between the grain and its adjacent grains has almost no effect on the grain-to-grain interaction.     

Novel Biocompatible Zr-Based Alloy with Low Young’s Modulus and Magnetic Susceptibility for Biomedical Implants

The microstructure, mechanical properties, magnetic susceptibility, electrochemical corrosion performance, in vitro cell compatibility and blood consistency of Zr-16Nb-xTi (x = 0, 4, 8, 12 and 16 wt.%) materials were investigated as potential materials for biomedical implants. X-ray diffraction (XRD) and Transmission electron microscopy (TEM) analyses revealed the secondary phase martensite α’ formed during the quenching process. The phase composition contained metastable β and martensite α’, resulting from Ti addition. These phase constitutions were the main causes of a low Young’s modulus and magnetic susceptibility. The in vitro cytocompatibility analysis illustrated that the MG63 cells maintained high activity (from 91% to 97%) after culturing in Zr-16Nb-xTi extraction media for 12 days due to the high internal biocompatibility of Zr, Nb and Ti elements, as well as the optimal corrosion resistance of Zr-16Nb-xTi. On the basis of Inductively coupled plasma optical emission spectrometry (ICP-OES) ion release studies, the concentration of Zr, Nb and Ti was noted to reach the equipment detective limit of 0.001 mg/L, which was much lower than pure Ti. With respect to the corrosion behavior in Hank’s solution, Zr-16Nb-16Ti displayed superior properties, possessing the lowest corrosion current density and widest passivation region, attributed to the addition of Ti. The blood compatibility test illustrated that the Zr-16Nb-xTi materials were nonhemolytic, and the platelets maintained a spherical shape, with no aggregation or activation on Zr-16Nb-xTi. Overall, Ti addition has obvious effects on the developed Zr-16Nb-xTi alloys, and Zr-16Nb-4Ti exhibited low magnetic susceptibility, low modulus, good biocompatibility and proper corrosion properties, demonstrating the potential of use as implant biomaterials.     

Insight into the Interaction between Water and Ion-Exchanged Aluminosilicate Glass by Nanoindentation

This work aims to explore the interaction between water and ion-exchanged aluminosilicate glass. The surface mechanical properties of ion-exchanged glasses after different hydration durations are investigated. The compressive stress and depth of stress layer are determined with a surface stress meter on the basis of photo-elasticity theory. The hardness and Young’s modulus are tested through nanoindentation. Infrared spectroscopy is used to determine the variation in surface structures of the glass samples. The results show that hydration has obvious effects on the hardness and Young’s modulus of the raw and ion-exchanged glasses. The hardness and Young’s modulus decrease to different extents after different hydration times, and the Young’s modulus shows some recovery with the prolonging of hydration time. The ion-exchanged glasses are more resistant to hydration. The tin side is more resistant to hydration than the air side. The results are expected to serve as reference for better understanding the hydration process of ion-exchanged glass.     

Burger Model as the Best Option for Modeling of Viscoelastic Behavior of Resists for Nanoimprint Lithography

In this study, Atomic Force Microscopy-based nanoindentation (AFM-NI) with diamond-like carbon (DLC) coated tip was used to analyze the mechanical response of poly(methyl methacrylate) (PMMA) thin films (thicknesses: 235 and 513 nm) on a silicon substrate. Then, Oliver and Pharr (OP) model was used to calculate hardness and Young’s modulus, while three different Static Linear Solid models were used to fit the creep curve and measure creep compliance, Young’s modulus, and viscosity. Values were compared with each other, and the best-suited method was suggested. The impact of four temperatures below the glass transition temperature and varied indentation depth on the mechanical properties has been analyzed. The results show high sensitivity on experiment parameters and there is a clear difference between thin and thick film. According to the requirements in the nanoimprint lithography (NIL), the ratio of hardness at demolding temperature to viscosity at molding temperature was introduced as a simple parameter for prediction of resist suitability for NIL. Finally, thinner PMMA film was tentatively attributed as more suitable for NIL.     

Destructive and Non-Destructive Evaluation of Fibre-Reinforced Concrete: A Comprehensive Study of Mechanical Properties

Ultrasonic pulse velocity (UPV) and rebound hammer tests are accepted as alternatives to destructive testing to determine the compressive strength, dynamic modulus of elasticity, and Poisson’s ratio, which are needed for structural design. Although much work has been conducted for plain concrete, the research data for fibre-reinforced concrete (FRC) is insufficient. In this regard, this study explains the correlations between compressive strength, rebound hammer, and UPV tests for plain concrete and FRC contains 0.25%, 0.50%, and 1.00% of 30 mm and 50 mm long steel fibres. A total of 78 concrete cube and beam specimens were tested by direct, semi-direct, and indirect UPV and rebound hammer test methods. The study found that the rebound hammer test is more suitable for measuring the compressive strength of matured FRC than young concrete. The UPV test revealed that the volume fraction does not, but the length of steel fibres does affect the UPV results by the direct test method. The UPV direct method has the highest velocity, approximately two times the indirect velocity in FRC. UPV measurements can be effectively used to determine the dynamic modulus of elasticity and Poisson’s ratio of FRC. The dynamic elastic modulus increases while the Poisson’s ratio decreases for the same steel fibre length when at increasing FRC fibre content. The results of this study will be significant for non-destructive evaluations of FRC, while additional recommendations for future studies are presented at the end of the paper.     

Influence of Thin Film Deposition on AFM Cantilever Tips in Adhesion and Young’s Modulus of MEMS Surfaces

Adhesion is a critical factor in microelectromechanical systems (MEMSs) and is influenced by many parameters. In important fields, such as microassembly, an improved understanding of adhesion can result in higher precision. This study examines the influence of deposition of gold and titanium onto the atomic force microscope (AFM) tips in adhesion forces and Young’s modulus, between a few MEMS substrates (silicon, gold, and silver) and the AFM tips. It was found that, except for gold substrate, an AFM tip coated with gold has the highest adhesion force of 42.67 nN for silicon substrates, whereas the titanium-coated AFM tip decreases the force for all the samples. This study suggests that such changes must be taken into account while studying the adhesion force. The final results indicate that utilizing gold substrate with titanium AFM tip led to the lowest adhesion force, which could be useful in adhesion force measurement during microassembly.     

Relationship between Thermal Diffusivity and Mechanical Properties of Wood

This paper describes an experimental study of the relationships between thermal diffusivity and mechanical characteristics including Brinell hardness, microhardness, and Young’s modulus of common pine (Pinus sylvestris L.), pedunculate oak (Quercus robur L.), and small-leaf lime (Tilia cordata Mill.) wood. A dependence of Brinell hardness and thermal diffusivity tensor components upon humidity for common pine wood is found. The results of the measurement of Brinell hardness, microhardness, Young’s modulus, and main components of thermal diffusivity tensor for three perpendicular cuts are found to be correlated. It is shown that the mechanical properties correlate better with the ratio of longitude to transversal thermal diffusivity coefficients than with the respective individual absolute values. The mechanical characteristics with the highest correlation with the abovementioned ratio are found to be the ratio of Young’s moduli in longitude and transversal directions. Our technique allows a comparative express assessment of wood mechanical properties by means of a contactless non-destructive measurement of its thermal properties using dynamic thermal imaging instead of laborious and material-consuming destructive mechanical tests.     

Predicting Compression Pressure of Knitted Fabric Using a Modified Laplace’s Law

The aim of this study is to develop a mathematical model for the prediction of compression pressure based on fabric parameters, such as engineering stress, engineering strain and engineering modulus of elasticity. Four knitted compression fabrics with different fibrous compositions and knit structures were used. Rectangular-cut strips were employed for the force–elongation characterization of the fabrics. The experimental pressure values between the fabric and rigid cylinder were assessed using a Picopress pressure measuring device. The mechanical and physical parameters of the fabric that influence the interface pressure, such as strain, elasticity modulus/stress and thickness, were determined and integrated into Laplace’s law. A good correlation was observed between the experimental and calculated pressure values for all combinations of fabrics, mounted with variable tension on the cylinder. Over the considered range of pressures, the difference between the two datasets was generally less than 0.5 mmHg. The effect of washing after five, ten and fifteen washing cycles on the fabric–cylinder interface pressure was found to be significant.