Changes In Modulus Research Articles

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.

Investigating the role of solvents in modulating glass transition and dynamic mechanical characteristics of polystyrene film

This study investigates how different solvents impact the glass transition and dynamic mechanical properties of polystyrene (PS) films. Using FTIR spectroscopy, it analyzes solvent-induced variations in molecular vibrations, particularly in the phenyl ring region. Results show solvent-specific effects on the 750 cm-1 peak, associated with the "meta-substituted aromatic ring," influencing phenyl ring vibrations. DSC analysis highlights solvent effects on the glass transition temperature (Tg), revealing complexities in PS films prepared with chloroform, tetrahydrofuran (THF), and toluene. Varied Tg behavior suggests solvent-driven structural modifications and gradual solvent removal. Dynamic Mechanical Analysis (DMA) demonstrates solvent-dependent changes in storage modulus, loss modulus, and tan δ, indicating solvent polarity role in polymer chain dynamics. Toluene-induced plasticization reduces Tg and increases creep compliance, revealing PS film sensitivity to solvents. These findings stress solvent selection importance in tailoring thermal and mechanical properties of polymer films for specific applications.

Stress-strain state of ceramic shell mold during formation of spherical steel casting in it. Part 2

The paper presents the results of numerical calculations of the solution to the problem of modeling the process of possible cracking in a spherical shell mold when pouring liquid steel into it and cooling the solidifying casting. The numerical scheme of the axisymmetric problem and the algorithm for its solution were given in Part 1. The crack resistance is estimated by magnitude of the normal stresses in the ceramic shell during its co-cooling with a solidifying casting. The results detailed analysis considered: fields of displacement, stresses, and temperatures both on spherical surface and in growing crust of solidified metal. The solution took into account the change in the shear modulus of the mold material from temperature, and an assessment of this refinement was given. The problem was solved in two ways. The first – with a constant shift modulus of the shell mold; the second – with its temperature-dependent shift modulus. There is a significant difference between these variants in terms of magnitude of the normal stresses arising in the shell mold. The authors analyzed resistance of the shell mold spherical geometry to external influences from its support filler and filling funnel. The problem of determining the contact and free surfaces at the boundary of the shell mold and support filler was solved. The results are presented graphically in the form of diagrams of stresses and temperatures over the studied area in its different sections and time intervals for cooling of the growing metal crust. The role of compressive normal stresses σ22 , σ33 on the surface of contact of the shell mold with liquid metal at the initial moment of cooling on probability of cracking in a spherical mold is shown. The level of strain-stress state in a spherical shell mold when cooling a steel casting in it is significantly determined by dependence of shift modulus of the shell mold on temperature.

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.

Oligo-cyclic loading-induced evolution of stress distribution and apparent amorphous modulus in lamellar stacks of high-density polyethylene

Assessing the resistance of high-density polyethylene (HDPE) against earthquake-like loads involves understanding the changes in structure and properties induced by oligo-cyclic loading at various length scales. To study the evolution of stress distribution and intrinsic properties within lamellar stacks from pristine to oligo-cyclic loading pre-conditioned materials, simultaneous in-situ SAXS/WAXS measurements were performed. During the elastic deformation of each pristine and preconditioned sample, crystal strain was tracked using the in-situ WAXS technique. Based on the established elastic tensor of the crystalline structure in polyethylene, we calculated the microscopic stress values within crystalline lamellae. In the pristine sample, lamellar stacks exhibit closely series-like coupling in the equatorial region and parallel-like coupling in the polar region of the spherulite. In the pre-conditioned sample, stress is primarily concentrated in the intra-fibrillar region, where the crystalline and amorphous phases are series-coupled, and strong strain concentration occurs in the inter-fibrillar region. By combining the local strain in the amorphous layer within the lamellar stacks in the equatorial region of the spherulite and the intra-fibrillar region with series-coupled lamellar stacks, measured by in-situ SAXS tests, the apparent amorphous modulus at the lamellar stack scale can be determined. This modulus changes from 71 to 106 MPa in the equatorial region of pristine spherulites to a notable 2000–7000 MPa in the intra-fibrillar region under the influence of oligo-cyclic pre-loading. Importantly, this apparent modulus is affected by both crystallization conditions and molecular structure, with molecular parameters exerting the primary influence.

Origins of Giant Anisotropic Phonon Heat Transfer in True‐1D van der Waals Material

AbstractThermal rectification devices, which facilitate preferential heat flow in a singular direction, stands as pivotal tools in the realization of solid‐state thermal circuits. 1D atomic chains, exhibit heightened thermal rectification efficiency owing to their exceptional directional heat conduction properties. These will find widespread utility in many applications, encompassing areas such as cooling, energy harvesting, and thermal isolation systems. However, unlike quasi‐1D materials, the intrinsic anisotropic heat transport in true‐1D atomic chains is yet to be systematically studied. Herein, the origins of the anisotropic heat transfer in three representative 1D structures (TaSe3 and BaTiS3 marked as quasi‐1D, MoI3 labeled as true‐1D) is first investigated by integrating a first‐principles density functional theory‐based framework of two‐channel heat conduction model. In contrast to quasi‐1D, MoI3 exhibits a giant anisotropy of lattice thermal conductivity (κL) in chain‐ and cross chain‐directions with a high ratio up to ≈20, which far exceeds the previous report for HfTe5 and ZrTe5. Such unique heat transfer reveals comprehensively by charge‐sharing and transferred charges, p‐‐d orbital hybridization and Young's modulus changes, induces an exceptionally large anisotropy. This study presents a high‐performance implementation of thermal rectification designed to regulate directional heat current, demonstrating its potential applicability in solid‐state thermal circuits.

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.

Full-scale polymer relaxation induced by single-chain confinement enhances mechanical stability of nanocomposites

Polymer nanocomposites with tuning functions are exciting candidates for various applications, and most current research has focused on static mechanical reinforcement. Actually, under service conditions of complex dynamic interference, stable dynamic mechanical properties with high energy dissipation become more critical. However, nanocomposites often exhibit a trade-off between static and dynamic mechanics, because of their contradictory underlying physics between chain crosslinking and chain relaxation. Here, we report a general strategy for constructing ultra-stable dynamic mechanical complex fluid nanocomposites with high energy dissipation by infusing complex fluids into the nanoconfined space. The key is to tailor full-scale polymer dynamics across an exceptionally broad timescale by single-chain confinement. These materials exhibit stable storage modulus (100 ~ 102 MPa) with high energy dissipation (loss factor > 0.4) over a broad frequency range (10−1 ~ 107 Hz)/temperature range (−35 ~ 85°C). In the loss factor > 0.4 region, their dynamic mechanical stability (rate of modulus change versus temperature (k)) is 10 times higher than that of conventional polymer nanocomposites.

Process–Property Correlation in Sustainable Printing Extrusion of Bio-Based Filaments

This study investigated the effect of two critical variables for environmental process sustainability, i.e., extruder temperature and printing rate, on thermomechanical performance and accuracy in overall sample sizes, when printing bio-based materials. In this context, 3D specimens produced from basic polylactide (n-PLA) and wood-filled PLA polymer (f-PLA) were realized using extrusion-based additive manufacturing technology (MEX) by varying the nozzle temperatures (200 °C, 210 °C, and 220 °C) and speed (from 70 mm/s to 130 mm/s). Dynamic mechanical analysis (DMA) was carried out on the produced specimens, providing information on changes in storage modulus at testing temperature of 30 °C (E′30) and glass transition temperature (Tg) for each printing condition. Measurements of sample sizes allowed for printing precision considerations as a function of processing temperature and speed. The results revealed similar trends in E′30 changes in printed specimens at a fixed extruder temperature as a function of printing speed for n-PLA and f-PLA. Infrared spectroscopy was performed on printed samples and unextruded material to attest potential material degradation under various operating conditions. Finally, images of sample surface allowed to verify the homogeneity of the diameter of the extruded material, and the layer–layer contact at the interface.

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.

Regularity analysis of resilient modulus for hot-mix asphalt with large temperature fluctuations

To evaluate the regularity of resilient modulus for hot-mix asphalt (HMA) under large temperature fluctuations, back propagation (BP) neural network technology was used to analyze the continuous change of HMA resilient modulus. Firstly, based on the abundant data, the training model of HMA resilient modulus was established by using BP neural network technology. Subsequently, BP neural network prediction and regression analysis were performed, and the prediction model of HMA resilient modulus at different temperatures (−50 °C to 60 °C) was obtained, which fully considered multi-factor and nonlinearity. Finally, the fitted theoretical model can be used to evaluate the HMA performance under the condition of large temperature fluctuations, and the rationality of theoretical model was verified by taking Harbin region as an example. It was found that the relationship between HMA resilient modulus and temperatures can be described by inverse tangent function. And the key parameters of theoretical model can be used to evaluate the continuous change characteristics of HMA resilient modulus with large temperature fluctuations. The results can further improve the HMA performance evaluation system and have certain theoretical value.

Effect of Knee Angle, Contractile Activity, and Intensity of Force Production on Vastus Lateralis Stiffness: A Supersonic Shear Wave Elastography Pilot Study.

Supersonic shear image (SSI) ultrasound elastography provides a quantitative assessment of tissue stiffness using the velocity of shear waves. SSI's great potential has allowed researchers in fields like biomechanics and muscle physiology to study the function of complex muscle groups in different conditions. The aim of this study is to use SSI to investigate changes in the stiffness of the vastus lateralis (VL) muscle as a consequence of passive elongation, isometric contraction, and repeated muscle activity. In a single session, 15 volunteers performed a series of isometric, concentric, and eccentric contractions. SSI images were collected from the VL to assess its stiffness before and after the contractions and at various knee angles. Two-way within-subjects ANOVA was used to test the effects of muscle contraction type and knee angle on VL stiffness. Linear regression analysis was employed to assess the relationship between muscle stiffness and the intensity of isometric contractions. After maximal contractions, VL stiffness increased by approximately 10% compared to baseline values, and following maximal isometric (p < 0.01) and eccentric contractions (p < 0.05). Yet, there was no change in VL shear modulus at the end of concentric contractions. The relaxed VL shear modulus increased with knee flexion both before and after the knee extensor contractions (p < 0.001). A linear relationship between the shear modulus and the degree of isometric contraction was observed, although with notable individual variation (R2 = 0.125). Maximal contractile activity produces modest increases in relaxed muscle stiffness. The SSI-measured shear modulus increases linearly with the degree of isometric contraction.

Effect of monovacancy defects on anisotropic mechanical behavior of monolayer graphene: A molecular dynamics study

The mechanical properties of monolayer graphene were studied using molecular dynamics (MD) simulation. The simulation results show that the tensile stress in the [010] crystal direction is greater than that in the [110] and [100] directions under uniaxial tensile. This confirms that graphene exhibits anisotropic behavior when subjected to external loading, resulting in changes in the Young's modulus in different directions. The calculated Young's modulus were 764.68 GPa, 532.50 GPa and 697.83 GPa for the [010], [110] and [100] directions, respectively. On this basis, the effect of defects on the mechanical properties was also considered. When there are vacancy defects, the stress concentration is linearly distributed along the Zigzag direction on both sides of the atomic vacancy defects. The effect of crack defects on the mechanical properties of graphene [010] crystal direction is the most significant. With the increase of crack size, the difference in fracture strength and fracture toughness calculated by MD simulation and the Griffith model decreases gradually. The potential energy of the non-defect model was found to be the highest, with the potential energy decreasing as the defect size increases. In addition, it was found that the strain rate also affects the stress-strain behavior of the monolayer graphene. However, when the crack size is large, the difference in the effect of strain rate on the anisotropic tensile fracture stress can be ignored.

Scale-inspired programmable robotic structures with concurrent shape morphing and stiffness variation.

Biological organisms often have remarkable multifunctionality through intricate structures, such as concurrent shape morphing and stiffness variation in the octopus. Soft robots, which are inspired by natural creatures, usually require the integration of separate modules to achieve these various functions. As a result, the whole structure is cumbersome, and the control system is complex, often involving multiple control loops to finish a required task. Here, inspired by the scales that cover creatures like pangolins and fish, we developed a robotic structure that can vary its stiffness and change shape simultaneously in a highly integrated, compact body. The scale-inspired layered structure (SAILS) was enabled by the inversely designed programmable surface patterns of the scales. After fabrication, SAILS was inherently soft and flexible. When sealed in an elastic envelope and subjected to negative confining pressure, it transitioned to its designated shape and concurrently became stiff. SAILS could be actuated at frequencies as high as 5 hertz and achieved an apparent bending modulus change of up to 53 times between its soft and stiff states. We further demonstrated both the versatility of SAILS by developing a soft robot that is amphibious and adaptive and tunable landing systems for drones with the capacity to accommodate different loads.

Study on updating finite element model of steel truss structure based on knowledge-enhanced deep reinforcement learning

Accurate assessment of the damage to a structure is the key to structural health monitoring. Among them, one effective means to assess the real-time status of the structure is by establishing a finite element model (FEM) of the structure and updating it synchronously. Previous research mainly updates the FEM of the structure with a certain moment in time without considering the continuous changes of structural parameters over a longer time. In this paper, we propose a FEM updating method for steel truss structure based on knowledge-enhanced deep reinforcement learning, which introduces long short-term memory (LSTM) network based on a deep deterministic policy gradient (DDPG) algorithm and constructs a knowledge-enhanced noise function (NF) module based on parametric analysis. The NF-LSTM-DDPG algorithm can fit a continuous variation of structural parameters. The ablation experiments revealed that the LSTM network and the NF module facilitate the exploration and learning ability of the DDPG algorithm. The NF-LSTM-DDPG algorithm is used in an actual steel truss structure case, and the variation rules of the elastic modulus and support deviations obtained from the solution are consistent with the actual situation. The average relative error of the 34 strain measurement points after updating is 14.147 %, and the relative error is higher than 20 % in only 13 days out of 187 days of continuous monitoring. Five days were selected for the comparative study, and the experimental results show that the relative error of the NF-LSTM-DDPG algorithm is 13.206 %, which is higher than that of the particle swarm optimization algorithm and the simulated annealing algorithm. The change of elastic modulus updated based on the NF-LSTM-DDPG algorithm is more reasonable than other algorithms.

The Effect of the Proportion of Rubber Components on the Properties of EVA/SBR/BR Foams

In actual production processes, pure ethyl vinyl acetate (EVA) foams have a high shrinkage rate, and the foaming matrix is prone to plastic deformation, even causing the collapse of bubbles. This limits the further application of EVA foams. In this study, we incorporated styrene butadiene rubber (SBR) and butadiene rubber (BR) into EVA to improve the mechanical properties and dimensional stability of EVA composite foams without sacrificing their low-density characteristics of low density. We used a melting index meter, rotorless vulcanizing meter and dynamic mechanical analysis (DMA) to characterize the changes in viscosity and energy storage modulus of the composite matrix. Scanning electron microscopy (SEM) was used to study the microscopic morphology of foams. The mechanical properties test results showed that the addition of SBR reduced the density of EVA/SBR/BR composite foams, and the addition of BR improved the mechanical properties and dimensional stability of the foams. By combining the advantages of both, the density of products is comparable to pure EVA, the tensile strength and the compressive strength are increased by 11% and 6.3% relative to pure EVA, respectively.

Exploring the structural characteristics and electrical conductivity of MnTiO3 across ferroelectric and paraelectric phases

In this study, we present the ceramic's structural, dielectric, and impedance characteristics obtained through the solid-state reaction method synthesis. Initial structural analysis was conducted utilizing X-ray diffraction at room temperature. The XRD results show that MnTiO3 exhibits rhombohedral symmetry. SEM images of MnTiO3 show the presence of both cubic and large agglomerated grains. This demonstrates the effectiveness of the dielectric HN model in controlling the mechanism. The alternating current (ac) conductivity, when examined in relation to frequency, displays a remarkable adherence to the Johnscher's power law. The change in electrical modulus and the width at half maximum (FWHM) of the curve indicate that the as-prepared sample exhibits a non-Debye relaxation mechanism. Both the temperature data and the frequency dependence of the impedance were used to analyze the electrical conductivity of the sample, which showed a negative temperature coefficient resistance (NTCR).

Heavy rainfall and moisture susceptibility of pavement foundation: A case study coupling finite element method and MnROAD moisture monitoring data

The Midwest region, including Minnesota, has been experiencing increased heavy precipitation events due to climate change, and the Minnesota Department of Transportation (MnDOT) is currently investigating the effect of climate change on pavement foundation and other transportation assets. As part of this effort, a study was conducted to investigate the impact of heavy rainfall on pavement foundation performance by focusing on moisture dynamics and resilient modulus changes in the pavement base layer. This study is aimed at understanding the adverse effects of heavy rainfall on moisture fluxes within pavement foundation and corresponding stiffness of the base aggregate layer. A two-step approach was adopted for predicting changes in saturation when estimating corresponding resilient modulus values using the resilient modulus prediction equation employed in AASHTOWare Pavement Mechanistic-Empirical (ME) Design. PLAXIS 3D, a finite-element analysis tool, was utilized to simulate the movement of moisture within the pavement layers under varying heavy rainfall scenarios. By incorporating predicted saturation from PLAXIS 3D simulations into the Pavement ME equation, corresponding resilient modulus values were estimated for the base layer. To ensure its accuracy and reliability, the model was validated using field sensor data from the MnROAD facility. Multiple linear regression models were developed to provide a means for estimating resilient modulus changes due to heavy rainfall. This study highlights the importance of considering moisture effects in pavement design and maintenance in regions prone to heavy rainfall events, and findings can be used by transportation agencies as part of their transportation/geotechnical asset management programs.

Multi-material structures of Ti6Al4V and Ti6Al4V-B4C through directed energy deposition-based additive manufacturing

The demand for advanced materials has driven innovation in titanium alloy design, particularly in the aerospace, automotive, and biomedical sectors. Additive manufacturing (AM) enables the construction of multi-material structures, offering potential improvements in mechanical properties such as wear resistance and high-temperature capabilities, thus extending the service life of components such as Ti6Al4V. Directed energy deposition (DED)-based metal AM was used to manufacture radial multi-material structures with a Ti6Al4V (Ti64) core and a Ti6Al4V-5 wt.% B4C composite outer layer. X-ray diffraction analysis and microstructural observation suggest that distinct B4C particles are strongly attached to the Ti6Al4V matrix. The addition of B4C increased the average hardness from 313 HV for Ti6Al4V to 538 HV for the composites. The addition of 5 wt.% B4C in Ti6Al4V increased the average compressive yield strength (YS) to 1440 MPa from 972 MPa for the control Ti6Al4V, i.e., &gt;48% increase without any significant change in the elastic modulus. The radial multi-material structures did not exhibit any changes in the compressive modulus compared to Ti6Al4V but displayed an increase in the average compressive YS to 1422 MPa, i.e., &gt;45% higher compared to Ti6Al4V. Microstructural characterization revealed a smooth transition from the pure Ti6Al4V at the core to the Ti64-B4C composite outer layer. No interfacial failure was observed during compressive deformation, indicating a strong metallurgical bonding during multi-material radial composite processing. Our results demonstrated that a significant improvement in mechanical properties can be achieved in one AM build operation through designing innovative multi-material structures using DED-based AM.