Changes In Elastic Modulus Research Articles

Research on shale dynamic and static elastic modulus and anisotropy based on pressurization history

The dynamic and static elastic parameters of rocks exhibit differences. It is of great practical significance to carry out experiments on dynamic and static elastic parameters of rocks under reservoir conditions and determine the conversion relationship between dynamic and static elastic parameters. In this study, shale oil samples from the second member of Kongdong sag in Dagang Oilfield were analyzed by triaxial compression experiments at different bedding angles and longitudinal and shear wave velocity tests. Dynamic and static stiffness coefficient, elastic modulus and acoustic wave velocity change under different directions of pressure and pressure relief. The results indicate that the P-wave velocity, fast shear wave velocity, slow shear wave velocity, dynamic and static Young’s modulus exhibit an increase as the confining pressure rises, and the parameters are greater during the unloading process than during loading process. At identical confining pressures, the dynamic Young’s modulus measured by cores with parallel bedding plane is greater than that measured by cores with vertical bedding plane. The dynamic and static elastic mechanical parameters of different bedding angles can be transformed under varying pressures, and the dynamic elastic mechanical parameters measured under varying levels of confining pressure can be transformed into static elastic mechanical parameters under equivalent confining pressures, which offer fundamental parameters for examining rock mechanics properties and serving as a reference for developing fracturing construction plans for oil and gas reservoirs.

First-Principles Study on the Mechanical Properties of Ni3Sn4-Based Intermetallic Compounds with Ce Doping

Ni3Sn4 intermetallic compound (IMC) is a critical material in modern electronic packaging and soldering technology. Although Ni3Sn4 enhances the strength of solder joints, its brittleness and anisotropy make it prone to crack formation under mechanical stress, such as thermal cycling or vibration. To improve the plasticity of Ni3Sn4 and mitigate its anisotropy, this study employs first-principles calculations to investigate the mechanical properties and electronic structure of the doped compounds Cex Ni3−xSn4 (x = 0, 0.5, 1, 1.5, 2) by adding the rare earth element Ce. The results indicate that the structure Ce0.5 Ni2.5Sn4 has a lower formation enthalpy (Hf) compared to other doped structures, suggesting enhanced stability. It was found that all structures exhibit improved plasticity with Ce doping, while the Ce0.5 Ni2.5Sn4 structure shows relatively minor changes in hardness (H) and elastic modulus, along with the lowest anisotropy value (AU). Analysis of the total density of states (TDOS) and partial density of states (PDOS) reveals that the electronic properties are primarily influenced by the Ni-d and Ce-f orbitals. At the Fermi level, all Cex Ni3−xSn4 (x = 0, 0.5, 1, 1.5, 2) structures exhibit metallic characteristics and distinct electrical conductivity. Notably, the TDOS value at the Fermi level for Ce0.5 Ni2.5Sn4 lies between those of Ni3Sn4 and other doped structures, indicating good metallicity and conductivity, as well as relative stability. Further PDOS analysis suggests that Ce doping enhances the plasticity of Ni3Sn4. This study provides valuable insights for the further application of rare earth elements in electronic packaging materials.

Elasticity Characteristics of Thenar Muscles in Carpal Tunnel Syndrome.

Measurement of thenar muscle elasticity by ultrasound shear wave elastography (SWE) may be useful for the diagnosis and evaluation of carpal tunnel syndrome (CTS), but there is a paucity of information on SWE of the thenar muscles in patients with CTS. The purpose of this study was to investigate the elasticity of the thenar muscles in patients with CTS. Twenty-two adult patients with a referral diagnosis of CTS (27 hands) and 20 healthy volunteers as a control (20 dominant hands) participated in this study. The elastic modulus of the thenar muscles was measured with SWE in two conditions, rest and pinch. The elastic modulus and percent change between the two conditions for each muscle were compared between groups. The elastic modulus of the abductor pollicis brevis (APB) in the patient group was lower than that in the control group at rest (20.6 ± 5.6 kPa vs. 25.0 ± 8.5 kPa; p = 0.034). However, the elastic modulus (87.9 ± 49.0 kPa vs. 62.5 ± 28.5 kPa; p = 0.044) and percent change (373.3 ± 336.4% vs. 169.2 ± 116.0%; p = 0.006) of the APB in the patient group were higher than those in the control group with pinch. For the opponens pollicis and adductor pollicis, there was no significant difference in the elastic modulus between groups. Patients with CTS showed differences in SWE of the APB. Future studies need to investigate the accuracy of SWE in diagnosing CTS and assessing prognosis.

Evaluating of the Relationships between aAverage Particle Size and Microstructure-Mechanical Properties of Materials Produced in Different Compositions using Ultrasonic Method

Pulse-echo ultrasonic test, which is one of the non-destructive testing methods, was used to measure ultrasonic quantities such as longitudinal velocity (VL), shear velocity (VT) and attenuation coefficient (α) in FeCrMn composites. The corresponding elastic constants were determined depending on the longitudinal and transverse velocity. The aim was to reveal the correlation between the microstructural and mechanical properties of FeCrMn composites and ultrasonic quantities. The effect of adding Cr particles on VL and VT velocities is obviously attributed to the change in elastic and shear modulus of FeCrMn composites. It was found that both VL and VT velocities, Young’s modulus (E) and shear modulus (G), as well as hardness values, changed approximately linearly with increasing Cr content. In this study, samples with different volumetric compositions were produced using the powder metallurgy method. It has been revealed that both the applied method and the increase in the amount of Cr have a significant effect on the velocities of VL and VT. The increase in VL and VT is due to the increase of Cr particles, the homogeneous distribution of Cr, the formation of samples especially at a certain temperature, and the decrease of porosity. As a result of these, a decrease in attenuation values was observed depending on the mean grain size. Elastic constants were found to vary in the same way as ultrasonic velocities. By increasing the Cr content both the hardness values and the shear modulus were improved and a good correlation was observed with the grain size.

ДИНАМИЧЕСКИЙ МЕХАНИЧЕСКИЙ АНАЛИЗ МОДИФИЦИРОВАННЫХ ПОЛИВИНИЛБУТИРАЛЕМ СОПОЛИМЕРОВ НА ОСНОВЕ ДИ(1-МЕТАКРИЛОКСИ-3-ХЛОРПРОПОКСИ-2-)МЕТИЛФОСФОНАТА И 2-ГИДРОКСИПРОПИЛМЕТАКРИЛАТА

The change of elastic modulus and tangent of angle of mechanical loss of materials based on polyvinyl butyral solutions in a mixture of monomers of di(1-methacryloyloxy-3-chloropropoxy-2-)methylphosphonate and 2-hydroxypropyl methacrylate has been investigated by the method of dynamic mechanical analysis. The presence of several peaks on the temperature dependences of tgd was observed, which is probably due to the presence of regions differing in crosslinking density. At 10 wt. % of polyvinylbutyral content in the process of (co)polymerization its partial migration to the surface of the formed polymeric material occurs.

A material model describing the nonlinear biaxial tensile behavior of fabric membrane in precise forming for inflated structures

Inflated membrane structures are increasingly used as formwork of concrete shells and in aerospace fields, which have high requirements for forming accuracy and therefore need to be analyzed for precise forming. The elastic modulus of membrane material is actually affected by stress ratio and strain state: during initial tension of membrane fabric, elastic modulus is small at low strain levels and changes quickly as stress state changes and strain grows. Therefore, a linear material constitutive model is inadequate for the precise forming analysis of an inflated structure with highly designed internal pressure, which leads to a high stress-strain state and various stress ratios. In this paper, a nonlinear material constitutive model is proposed by formulating the change of elastic modulus as a nonlinear function about strain state coupled to a linear function of stress ratio, considering the combined impacts of both factors. Biaxial tensile tests are performed to determine the material property and develop the nonlinear material model. The precise forming analysis results with the proposed material model and three commonly used membrane material models are discussed and compared based on an inflation experiment of a spherical inflated membrane structure. The simulation with the proposed model basically exhibits a nonlinear variation law and a variance of less than 0.2 % throughout the inflation, demonstrating that the proposed material model has superior accuracy in predicting the forming shape of the inflated membrane structure.

Comparative study of elastic properties measurement techniques during plastic deformation of aluminum, magnesium, and titanium alloys: application to springback simulation

Reliable determination of the elastic moduli of metals can be quite demanding, especially as the apparent elastic modulus of metals is known to decrease with deformation. Traditionally, this dependence on plastic strain has been investigated through various tensile tests, but discrepancies persist across the different approaches. Here we compare several tensile test-based evaluation protocols based on loading-unloading experiments to measure the change in elastic moduli of the light metal alloys AZ31B, EN AW-6082, and Ti–6Al–4V during tensile deformation. Additionally, the initial Young’s modulus determination via tensile testing, three-point-bending experiments, contact-free laser ultrasonic zero-group-velocity plate resonance, and piezoelectric contact ultrasonic time-of-flight measurements were compared. The results reveal non-negligible differences in the strain-dependency of elastic moduli between the determination techniques. Additionally, the laser ultrasound measurements demonstrate an improved accuracy and repeatability for the determination of the initial elastic moduli of light metal sheets. The benefit of considering the reduction of the elastic moduli in finite element springback simulation of three-point-bending tests is demonstrated and the use of the chord modulus is found to be generally most appropriate.

Viscoelastic Behavior of Cellular Biomaterials Based on Octet-Truss and Tetrahedron Topologies.

Cellular biomaterials offer unique properties for diverse biomedical applications. However, their complex viscoelastic behavior requires careful consideration for design optimization. This study explores the effective viscoelastic response of two promising unit cell designs (tetrahedron-based and octet-truss) suitable for high porosity and strong mechanics. The asymptotic homogenization (AH) method was employed to determine effective longitudinal and shear moduli, as well as Poisson's ratio, across various relative densities. Finite element simulations (ABAQUS) validated the AH results, demonstrating good agreement (<10% discrepancies). Additionally, analytical models and compression tests on 3D-printed lattice structures supported the theoretical predictions. The study revealed a strong correlation between relative density and the effective modulus of both designs. Notably, the tetrahedron-based design exhibited superior modulus, making it favorable for high loading levels, particularly when used as a high-density configuration. Both designs demonstrated minimal time-dependent elastic modulus changes and a near-constant Poisson's ratio (0.34-0.349 for octet-truss, 0.316-0.326 for tetrahedron) across a 5-50% relative density range. While minimal, time-dependent modulus reduction needs to be considered in longer-term simulations (t>107 s). This study provides valuable insights into the viscoelastic behavior of these unit cells using the homogenization method, with potential applications in various biomedical fields.

A Study on the Measurement Method of Biot Coefficient for Concrete Based on Experimental Approaches.

Concrete stress is a key factor influencing the operational safety of concrete dams, and understanding the true distribution and variation of stress is a major research focus in the field of dam engineering. In the heel region of the dam, internal voids in the concrete may allow external water infiltration under high hydraulic head, leading to changes in the concrete's elastic modulus and Biot coefficient. These changes, in turn, affect the effective stress experienced by the concrete. Consequently, the measured stress in the heel and toe regions may differ from conventional understanding and standard calculation methods for dam stresses. This is particularly evident in the following aspects: after water impoundment, compressive stress in the dam heel is higher than in the dam toe, with the heel stress exceeding the calculated value by a significant margin, and the variation in stress during the impoundment process being smaller than the calculated value. To address these issues, this paper proposes a theoretical method for measuring the Biot coefficient of concrete through experimental testing and innovatively develops the corresponding experimental equipment. This equipment can accurately simulate the conditions of the dam under different water depths (confining pressures) and measure the deformation of concrete caused by changes in water depth. Based on this equipment, tests were conducted on the elastic modulus and Biot coefficient of dry and saturated concrete specimens under different confining pressures. The Voigt-Reuss-Hill mixed average modulus formula was applied to calculate the elastic modulus of the concrete matrix, exploring the influence of pore water on the mechanical properties of the concrete. The results indicate that the pore water inside the concrete increases its equivalent elastic modulus during the testing process. In numerical simulations of the dam, this increased modulus due to pore water is often overlooked, leading to an underestimation of the results. This partially explains why the measured compressive stress in the dam heel consistently exceeds the calculated values. According to the Biot coefficient calculation theory proposed in this paper, the Biot coefficient of concrete varies with its water content. The Biot coefficient is lower in specimens with high water content compared to those with low water content. Using the Voigt-Reuss-Hill mixed average modulus formula, the elastic modulus of the concrete matrix obtained from the tests was found to be 28 GPa, which is in good agreement with the results from regression analysis. These findings are of significant importance for the safe operation of concrete dam engineering.

Technical note: Effects of chemical, radiational, and thermal treatment of bone tissue on material stiffness and anisotropy.

We evaluated the effects of four treatments for pathogen inactivation in bone tissue (ethanol storage, formalin fixation, gamma irradiation, and heat treatment via autoclave) on stiffness and anisotropy values in bone samples. Cortical bone samples from the humerus of 14 bovine specimens were subjected to Knoop microindentation analysis in longitudinal and transverse planes of section and four indenter orientations within each section. From each specimen, individual samples were assigned to one of five treatment conditions: 50% ethanol-saline solution, formalin immersion, gamma irradiation, autoclave, and buffered saline (controls). Each sample was microindented 100 times and the resultant stiffness data were analyzed by a resampled factorial analysis of variance. First- and second-order interactions as well as main effects of indenter orientation, treatment, and specimen were significant for both transverse and longitudinal sections, with the sole exception that indenter orientation-treatment interaction was nonsignificant for longitudinal sections. Interaction plots reveal that thermal (autoclave) and irradiation treatments depress stiffness values the most, while patterns of indentation stiffness at different orientations are relatively unaffected. Patterns of anisotropy are relatively unaffected by preservative treatments, but elastic modulus changes are consistent and unambiguous. Formalin and ethanol treatments are most comparable to controls and represent the best preservative media for mechanical testing. These options, however, are likely to be the least effective for ensuring the inactivation or sterilization of potentially contaminated samples.

A rock physics modelling approach for time‐lapse monitoring and characterization of fluid–rock interactions in hydrocarbon reservoirs

AbstractOne of the research gaps is to understand the development of seismic characteristics of gas‐saturated rock along with the change in rock properties because of chemical reactions. We suggest a method to explain the change in elastic properties brought on by CO2 injection in a rock by capturing the physico‐chemical interactions observed in the laboratory in a theory of rock physics. To explain the laboratory‐measured physical characteristics and velocity of a dynamic rock–fluid system, we include a time‐dependent component in the existing cemented‐sand model. We demonstrate theoretically the rate of change of elastic moduli of the dry frame by incorporating the measured rate of change of cement due to chemical dissolution. We adapt the theory such that it can be applied to the field data and calibrate the theory using water‐saturated well log data from the Ankleshwar field, an established oil field in the Cambay basin, western India. Theoretical time‐lapse logs of velocity and density are then produced using the theory over a range of CO2 saturations, assuming cementing material in grain contacts and geochemical interactions comparable to those observed in the laboratory rock. Then, using theoretical logs, corresponding time‐lapse synthetic seismic data are produced for different saturation. These data clearly demonstrate that, for a uniform model, velocity decreases by up to 18% as CO2 saturation increases from 0% to 20% (ignoring the chemical effect), and that, for a specific saturation, say 20%, chemical effects result in a 17% decrease in velocity from the present to the end of 60 years. However, for the patchy model, velocity decreases maximum by 14% and 16% due to varying saturation and chemical reaction. Moreover, for a particular saturation of CO2, say 20%, velocity differs by 16% for different types of models. This research contributes to making strategy for CO2‐sequestration in a designated field.

Experimental study on axial compressive properties of bamboo scrimber after high temperature

This study examines the uniaxial compressive mechanical properties of after high temperature bamboo scrimber, taking into account the combined effects of temperature, constant temperature duration, and moisture content. A series of 46 uniaxial compression tests were conducted on bamboo scrimber under various conditions to investigate the failure modes after high temperatures. The analysis focuses on the changes in compressive elastic modulus and peak stress of bamboo scrimber parallel and perpendicular to the grain, in relation to temperature, constant temperature duration, and moisture content. The findings reveal that below 180℃, diagonal shear failure and Y-type shear failure are the primary failure modes for specimens parallel to the grain, while diagonal shear failure predominates for specimens perpendicular to the grain. Above 180℃, bond failure and eccentric crushing become the main failure modes for specimens parallel and perpendicular to the grain, respectively. The peak compressive stress decreases significantly beyond 180℃, with a slower decrease observed as moisture content increases. Constant temperature duration has a notable impact on peak stress, with longer durations resulting in lower peak stress at the same temperature. Although temperature has a lesser effect on the elastic modulus compared to peak stress, empirical formulas were derived to establish the relationship between compressive elastic modulus and peak stress reduction coefficient with variations in temperature, constant temperature duration, and moisture content based on the experimental data.

Mechanical properties of reactive powder concrete under compression at ultra-low temperatures

In this paper, the mechanical properties of reactive powder concrete (RPC) at ultra-low temperatures were studied. RPC prisms (300 mm × 100 mm × 100 mm) were tested at ultra-low temperatures (20 °C, 0 °C, −20 °C, −40 °C, −80 °C, −120 °C, −165 °C) and resulting prism compressive strength, compressive stress-strain curve, and toughness were determined. The increase in prismatic compressive strength of RPC at ultra-low temperatures is greater than that of ordinary concrete, with an overall strength of about 2.12 times that of ordinary concrete. Pore water freezing behavior was also studied to assess the effects on the mechanical properties of RPC in ultra-low temperatures. The water-ice phase transition further improved the RPC strength. With the reduction in temperature, The change in elastic modulus of RPC change is small, the peak strain of specimens at different temperatures increases with the decrease in temperature. The peak strain of RPC showed an overall linear increase with decreasing temperatures, and the water-ice phase transition at negative temperature increases the peak strain of RPC, adding steel fibers improves the RPC ductility, limiting the fracture. With the temperature reduction, RPC toughness first increases and then decreases. The toughness is lowest at room temperature, and highest at −120 °C, which is 2.26 times higher than at room temperature. RPC has better toughness than normal concrete at different temperatures, the reduction of temperature relatively improves the toughness of RPC, and the addition of steel fibers plays a vital role in improving the toughness. This study can serve as technical support for using RPC to design liquefied natural gas full-capacity tanks.

The effect of rock mechanical heterogeneity on induced stress and initiation pressure of multi-cluster fracturing

The stress interference between fracturing clusters in horizontal wells is key in affecting the initiation and propagation of multi-cluster fractures. However, in reservoirs such as shale, there are often changes in the mechanical properties of the rock along the direction of the wellbore. Such changes are often not considered in models for multi-fracture propagation. As a result, the impact of rock mechanical heterogeneity on induced stress is not fully understood. Therefore, in this paper, a prediction model of the three-dimensional induced stress field of hydraulic fractures is established, taking into account mechanical heterogeneity. Combined with the prediction model of fracturing pressure, the changes in induced stress and initiation pressure under different conditions are analyzed. The results indicate a significant difference between the induced stress results considering mechanical heterogeneity and those considering only a single homogeneous region. The change in elastic modulus has a profound influence on induced stress and initiation pressure. Perforating at locations with low elastic modulus in situ can help reduce initiation pressure. Additionally, temporarily blocking the wellbore and reducing the flow rate to decrease the net pressure in the fractures can facilitate more fractures to initiate.

Elastic modulus, water stability and resistivity for loess solidified with white mud based solid waste cementing material: Mechanism analysis and relationship establishment

To increase the engineering application value of white mud based solid waste cementing materials: white mud-slag and white mud-slag-Calcium Carbide Residue (CCR), this paper explored the changes in elastic modulus, water stability and resistivity of loess solidified with white mud based solid waste cementing material. Furthermore, relationships between elastic modulus, water stability and resistivity were established. The following conclusions can be obtained: The alkaline activation effect of CCR was stronger than white mud, therefore the formation rate of C-S-H and C-A-(S)-H cementitious products in CCR-containing solidified loess was more faster than that without CCR. At the same time, white mud not only served as an alkaline activator, but its finer CaCO3 components also helped fill pores, while the irregular fine particles provided nucleation sites for the formation of cementitious products. Consequently, slag-white mud-CCR solidified loess exhibited the best performance in terms of elastic modulus and water stability coefficient. This was followed by slag-white mud solidified loess and lime solidified loess. In addition, the analysis of the relationship between the resistivity of solidified loess and factors such as curing age, dry density, water content, elastic modulus, and water stability coefficient revealed that the main reasons for the increased resistivity of solidified loess were the consumption of internal water and the increase in cementitious products with poor conductivity. Furthermore, the modified resistivity formula was applied to establish the fitting relationships between the resistivity of solidified loess and various parameters. The formula has been successfully applied in the slag-white mud-CCR solidified loess, where the fitting of resistivity with various parameters yielded an R2 of 0.94. This paper facilitates the resistivity method (non-destructive testing) of loess treated with slag, white mud, CCR and promotes the application of these curing agents, contributing to their broader adoption in geotechnical engineering.

Experimental study on fracture failure characteristics evaluation of wooden pallets in humid-cold environment based on piezoelectric technology

Wooden pallets often suffer mechanical damage during transportation, stacking, forklifting, and on-site handling in cold supply chain logistics. In humid-cold environments, the fracture properties of wooden pallets change, increasing the risk of sudden fracture failure. Understanding the fracture failure characteristics of wooden pallets is essential to prevent further damage to goods. Nevertheless, evaluating and identifying these characteristics currently presents significant challenges. This study investigates the changes in modulus of elasticity (MOE) and fracture failure characteristics including modulus of rupture (MOR), brittleness and toughness of wooden pallets and impact toughness of wood material under humid-cold conditions. The piezoelectric technology was applied to evaluate and identify fracture risk of wooden pallets used in various humidity and cold conditions. Quarter-sized wooden pallets and standard wood specimens were examined by laboratory study. The experimental results showed that the MOE, MOR, toughness of wooden pallets and impact toughness of wood with higher moisture content (MC) increased with decreasing temperature, while brittleness increased as temperature decreased. These results indicate that the maximum carrying ability of wooden pallets increases in humid-cold environments while the ability to resist fracture was reduced with a higher brittle rupture risk. The toughness and its corresponding piezoelectric voltage exhibited good consistency with changes in temperature and MC. The relationship between toughness and piezoelectric voltage was established with good coefficient of determination (over 0.81). It indicates that the risk of wooden pallets could be predicted effectively using piezoelectric technology.

Understanding mechanism on carbonation curing for Portland cement through phase profiling via QXRD analysis and thermodynamic modeling

The mechanism of early age accelerated carbonation cured ordinary Portland cement mixtures is evaluated using experimental and thermodynamic modeling. This study considered three early precuring conditions, two carbonation curing periods, four CO2 concentrations, and a 0.5 w/c ratio. The investigation was conducted using phase profiling of mixtures based on QXRD results and developed a thermodynamic model that simulated the experimental conditions. The mechanical characteristics of carbonation-cured mortar specimens, including compressive strength, elastic modulus, shrinkage, and mass change, were evaluated. The results revealed that short precuring durations hindered carbonation, resulting in lower CO2 uptake, strength, elastic modulus and higher shrinkage. Increasing the precuring period from six-hours to one or three days resulted significant amount of CaCO3 precipitation on the surface of the specimen and appropriate mechanical properties. One day precuring followed by one day carbonation with a 10 % CO2 exposure resulted in a higher calcite precipitation on the surface with less depth of penetration. It was found that a balance between drying-induced degradation and microstructure densification due to calcite precipitation is crucial. An appropriate precuring duration, for each binder type and mix proportion, should be applied to achieve desired properties and CO2 uptake in carbonation-cured cementitious materials.

Micro-morphology and fractal characteristics of pore structure of aeolian sand concrete under long-term semi-immersion with chloride solution

To investigate the influence of chloride exposure on hydraulic concrete, we investigated the microstructural changes and pore evolution of aeolian sand concrete (ASC) during prolonged semi-immersion in chloride solution. Our analysis included examining the mass loss rate, relative dynamic elastic modulus, and maximum depth of chloride erosion. Utilizing scanning electron microscopy (SEM), X-ray diffraction (XRD), and nuclear magnetic resonance (NMR), we assessed the microscopic morphology and pore structure evolution. Additionally, we employed fractal theory to evaluate pore structure heterogeneity in ASC before and after exposure to chloride erosion. After 450 days of chloride erosion, ASC displayed minimal changes in mass loss rate and relative dynamic elastic modulus, with a maximum erosion depth of 9.8 mm. Chlorides adhered to the immersed end at the concrete's base and migrated from the surface to the exposed top end during erosion. The erosion depth at the top end ranged from 23.9 % to 25.9 % of that at the bottom end. Within ASC, hydration products reacted with chlorides, resulting in the formation of Friedel's salt, a characteristic corrosion crystal. Following erosion, the total porosity of ASC increased, accompanied by shifts in pore size distribution. The internal structure of ASC underwent distinctive evolution, transitioning from small to large pores. ASC consistently exhibited fractal properties both before and after erosion. The fractal dimension D1 demonstrated an inverse relationship with pores of radius (r) less than 0.01 μm, while D2 was directly proportional to pores with r ≤ 0.01 μm and 0.01 <r ≤ 0.1 μm, and inversely proportional to pores with 1 <r ≤ 10 μm and r > 10 μm. This study significantly contributes to the theoretical understanding of ASC's endurance mechanisms in chloride environments.

Experimental Evaluation of Compressive Properties of Early-Age Mortar and Concrete Hollow-Block Masonry Prisms within Construction Stages.

Early-age masonry structures require temporary support until they achieve full strength. Nevertheless, there is a limited understanding of the properties of freshly laid masonry and the design of newly constructed, unsupported masonry walls. This situation has led to numerous instances of structural damage and injuries to workers, prompting conservative construction bracing techniques. This paper presents comprehensive experimental studies on early-age mortar cubes and masonry prisms to assess the effects of curing time on the compressive properties of masonry assemblies, which is necessary for the design of temporary bracing. The change in modulus of elasticity and compressive strength of masonry prisms and mortar with curing time has been experimentally assessed. The results indicate that the compressive strength of freshly cast mortar cubes is relatively insignificant until approximately 24 h after construction, when it was observed to increase logarithmically. Regarding the performance perspective, the compressive strength of early-age masonry prisms is inconsiderable, less than 15% of full strength during the first day after construction. By contrast, regarding the life safety perspective, the compressive properties of a mortar joint within a masonry assembly (which is of more practical interest) appear to have no effect on the failure strength of concrete masonry prisms over the range of ages tested. The failure modes of the early-age mortar cubes and early-age masonry prism samples depend on the curing time, and different failure modes occurred before and after the start of the primary hydration phase, which is 20.8 h after construction. It is anticipated that the proposed research will provide valuable material properties leading to efficient design of control devices (e.g., temporary bracing) and improved guidelines for concrete-block masonry construction.

Nano-, micro- and macro-indentation tests of thermal spray WC-Ni coatings with lamellar microstructure at different particle deposition temperatures

The mechanical properties of WC-Ni coatings by HVOF thermal spraying were comprehensively evaluated by indentation tests at a wide load range of 10−1-103 N, i.e. nano-, micro- and macro-indentations. The correlation between process parameters and coating microstructure and mechanical properties was characterized via particle deposition temperature. The coating microstructure changes in reduced porosity, enhanced WC phase decomposition and better splats flattening were correlated to the particle deposition temperature rising. A porosity divergence between coating surface and cross-section was found as a quantitative anisotropy indicator to coating intrinsic lamellar microstructure formed by the splats flattening and piling up. Considering the lamellar microstructure, indentation responses on coating surface and cross-section were compared for hardness and elastic modulus evaluation below 3 N. The surface hardness is higher than that of cross-section, and both increased correlatively to the particle deposition temperature rising except for the almost constant surface hardness below 1 N. An analogous particle temperature-dependent behavior was also manifested for the elastic modulus by nano-indentation below 1 N. Interestingly, the elastic modulus by coating surface micro-indentation at 30 N presented identical particle temperature dependence to that by coating cross-section nano-indentation, both consistently representing the overall coating elastic modulus change trend verified by non-destructive ultrasonic test. Indentation fracture toughness on coating surface under 1.96 kN and on coating cross-section under 49 N was comparatively evaluated, and the values had a reverse trend of dependence on the particle deposition temperature. The particle-deposition-temperature dependent mechanical properties were interpreted by the coating intra-splats and inter-splats defects reduction with enhanced carbide-metal bonding essentially determined by the melting state of the metal binder phase, providing an insight to utilize indentation tests for characterizing thermal spray coatings.