Microstructural Variations Research Articles

Exploring the micromorphological diversity of palynomorphic flora from lesser Himalaya biodiversity hotspot

Palynology, a prominent field in plant systematics and biodiversity studies, plays a vital role in identifying and determining the plant species present in a specific region. The current study was performed to evaluate the micromorphological traits of pollen from flora of Lesser Himalaya. Pollen microstructural variations aid in the identification of species belonging to specific botanical families and various geographic habitats. Flowers of 24 selected species categorized into 16 families were collected, preserved and then acetolysis protocol followed. Pollen was examined under a light and scanning microscopy (LM and SEM) for palynomorph description. The palynomorphs characteristics such as size, shape, exine surface, and aperture orientation, were examined. Status of these plants show that herbs are being dominant (11 species), while shrubs (7 species), climbers (3 species), bulbous plants (2 species), small tree, sedge, weed (1 species each). Pollen shape determined in equatorial view were; spheroidal, sub-prolate, oblate-spheroidal, prolate, spherical and sub-oblate. The variations were seen among pollen types; tricolpate, tricolporate and polyporate in most of the species. Exine stratification was observed mostly scabrate while echinate, cristate-reticulate, granulate, punctate, rugulate-perforate, striate-rugulate, verrucate, cristate-foveolate was visualized in each different species. Palynomorph apertural patterns were observed sunken, furrowed, slightly bulged, scabrate, granulate, slit like, and perforate. The largest polar diameter was measured in Hymenocallis littoralis (138.6 µm) whereas smallest in Parthenium hysterophorus (14.70 µm). Equatorial distance was calculated maximum for Cascabela thevetia (110.1 µm) and minimum for Hibiscus rosa-sinensis (1.7 µm). P/E ratio was calculated largest in Hymenocallis littoralis (1.8) and lowest in Duranta erecta (0.89). The palynomorphs taxonomic characters investigated can be helpful in species level identification and provide a baseline to conduct more systematic research with respect to specific plant families and genera.

Mechanical and microstructural characterization of AISI SAE 4130 steel welded joints made by robotic gas metal arc welding process: influence of electrode work angle in 'T' welded joints

Microstructural variations within welded metals, specifically in terms of phases and their corresponding volume fractions, play a crucial role in influencing weld strength and other mechanical properties. Welded joints in a ‘T’ configuration pose a unique challenge due to the dynamic heat distribution caused by changes in the electrode work angle (EWA) between perpendicularly aligned plates. This study focuses on characterizing the microstructure and micro-hardness of ‘T’ welded joints in a 6 mm thick plate of AISI SAE 4130, welded using the robotic gas metal arc welding process. The examination covers three distinct zones: the base material (BM), the fusion zone (FZ), and the heat-affected zone (HAZ). The extent of the HAZ is meticulously measured on both the vertical and horizontal plates within the weld zones. The x-ray diffraction (XRD) analysis results indicated that the average crystallite size of the base metal and fusion zone is 25.75 nm and 24.51 nm respectively. As per the scanning electron microscope (SEM) image observations, the higher wire feed rate yields to brittle fracture surface. The torch angles notably influence the dimensions of the HAZ on the vertical and horizontal plates of a ‘T’-Joint. Welding at higher EWA and contact-tip-work-distance, results in a larger HAZ on the vertical plate. Conversely, employing a flattened EWA and an increased contact-tip-work-distance leads to a greater extent of the HAZ on the horizontal plate. Furthermore, the micro-hardness of the fusion zone and heat-affected zone demonstrates an increase at higher settings of wire feed rate and travel speed. This phenomenon is attributed to the elevated heat inputs, which contribute to the formation of a finer microstructure within the weldment.

Effect of Fe addition and ion irradiation on surface hardness in zirconium alloys: Experiments and modeling

Exploring the effect of Fe addition and ion irradiation on surface hardness in Zr alloys not only elucidates the strengthening mechanisms of individual alloying elements but also facilitates the assessment of mechanical properties under varying damage levels. In this work, the microstructural variations and surface hardness of Zr and Zr-Fe alloys were examined through Ne+ and Au3+ irradiation experiments. Electron backscatter diffraction (EBSD) characterization suggested the potential of Fe addition in Zr-Fe alloys for grain refinement. Transmission Electron Microscopy (TEM) observations indicated the formation of dislocation loops in irradiated materials, accompanied by a transformation of Zr3Fe particles from a crystalline to an amorphous state. Furthermore, nano-indentation tests were employed to measure the depth-dependent hardness, revealing an augmentation in hardness with increasing Fe content and highlighting noticeable irradiation hardening in Zr alloys. A mechanical model was then developed to theoretically investigate the contribution of diverse hardening mechanisms in ion-irradiated Zr alloys, particularly addressing the impact of non-uniformly distributed defects. Theoretical analysis denoted that the irradiation-induced defects hardening at varying depths follows distinct laws, whereas the precipitation hardening in Zr-Fe alloys was attributed to high-density strengthening particles induced by Fe addition. Moreover, it was determined that the surface hardness is governed by geometrically necessary dislocations (GNDs) and irradiation-induced defects at shallow depths, whereas precipitates and statistically stored dislocations (SSDs) dominate at relatively larger depths.

Stress and Microstructures Characterization Based on Magnetic Incremental Permeability and Magnetic Barkhausen Noise Techniques.

Both microstructure and stress affect the structure and kinematic properties of magnetic domains. In fact, microstructural and stress variations often coexist. However, the coupling of microstructure and stress on magnetic domains is seldom considered in the evaluation of microstructural characteristics. In this investigation, Magnetic incremental permeability (MIP) and magnetic Barkhausen noise (MBN) techniques are used to study the coupling effect of characteristic microstructure and stress on the reversible and irreversible motions of magnetic domains, and the quantitative relationship between microstructure and magnetic domain characteristics is established. Considering the coupling effect of microstructure and stress on magnetic domains, a patterned characterization method of microstructure and stress is innovatively proposed. Pattern recognition based on the Multi-layer Perceptron (MLP) model is realized for microstructure and stress with an accuracy rate higher than 97%. The results show that the pattern recognition accuracy of magnetic domain features and micro-magnetic features simultaneously as input parameters is higher than that of micro-magnetic features alone as input parameters.

Exploring microstructure variations and hydrogen storage characteristics in TiVNbCrNi high-entropy alloys with different Ni incorporation

In recent years, high-entropy alloys (HEAs), as a novel class of hydrogen storage materials, have been deemed highly promising due to their extensive compositional tunability and the unique high entropy effects. This study aims to enhance the comprehensive hydrogen storage performance of the TiVNbCr-based HEA by introducing Ni. The effects of Ni addition on the microstructural evolution of the alloy and its impact on activation properties, hydrogen absorption and desorption kinetics, thermodynamics, and cycling performance under the complex physicochemical environment of multiple principal elements was systematically investigated. The findings indicate that Ni addition shortens the activation incubation period of the alloy but more Ni reduces the intrinsic hydrogen absorption kinetics. In the Ti25V30Nb10Cr33Ni2 alloy, a high reversible hydrogen storage capacity of up to 2.2 wt% at room temperature was achieved, surpassing most of the currently reported body-centered cubic (BCC)-structured high-entropy hydrogen storage alloys. Furthermore, the influence of Ni on the alloy's hydrogen desorption kinetics and cycling hydrogenation performance was studied. Results from 110 cycles of testing reveal that the introduction of Ni-induced Laves phases can act to relax stress, thereby reducing strain accumulation during the hydrogen absorption and desorption cycling process. This could provide guidance for the design of high-entropy hydrogen storage alloys with extended cycling lifetimes.

Microstructure and Thermal Mechanical Behavior of Arc-Welded Aluminum Alloy 6061-T6

In this study, the welding thermal cycle, as well as the microstructural and mechanical properties of welded AA6061-T6 plates, were studied. The plates were prepared and bead-on-plate welded using gas metal arc welding (GMAW). Numerical simulations using SYSWELD® were performed to obtain the thermal distribution in the welded plates. The numerical heat source was calibrated using the temperatures obtained from the experimental work and the geometry of the melting pool. The mechanical properties were obtained through microhardness tests and were correlated with the welding thermal cycle. Moreover, the mechanical behavior and local deformation in the heat-affected zone (HAZ) were investigated using micro-flat tensile (MFT) tests with digital image correlation (DIC). The mechanical properties of the subzones in the HAZ were then correlated with the welding thermal cycle and with the microstructure of the HAZ. It was observed that the welding thermal cycle produced microstructural variations across the HAZ, which significantly affected the mechanical behavior of the HAZ subzones. The results revealed that MFT tests with the DIC technique are an excellent tool for studying the local mechanical behavior change in AA6061-T6 welded parts due to the welding heat.

Cross-centroid ripple pattern for facial expression recognition

AbstractIn this paper, we propose a new feature descriptor Cross-Centroid Ripple Pattern (CRIP) for facial expression recognition. CRIP encodes the transitional pattern of a facial expression by incorporating a cross-centroid relationship between two ripples located at radius r1 and r2 respectively. These ripples are generated by dividing the local neighborhood region into subregions. Thus, CRIP has the ability to preserve macro and microstructural variations in an extensive region, which enables it to deal with side views and spontaneous expressions. Furthermore, gradient information between cross centroid ripples provides strength to capture prominent edge features in active patches: eyes, nose, and mouth, that define the disparities between different facial expressions. Cross-centroid information also provides robustness to irregular illumination. Moreover, CRIP utilizes the averaging behavior of pixels at subregions that yields robustness to deal with noisy conditions. The performance of the proposed descriptor is evaluated on seven comprehensive expression datasets consisting of challenging conditions such as age, pose, ethnicity, and illumination variations. The experimental results show that our descriptor consistently achieved a better accuracy rate as compared to existing state-of-the-art approaches.

Macro-micro mechanical behavior of saturated cemented sands during drained triaxial shearing

To enhance the understanding of the macro-micro mechanical behavior of cemented sands, a series of drained triaxial shearing tests were conducted on saturated cemented sands with varying cement contents and confining stresses. These tests incorporated high-performance acoustic emission (AE) monitoring and an environmental scanning electron microscope (ESEM) technique. The results yielded quantitative interpretations of macro-mechanical response, microstructural variation, and AE behaviors. Specifically, increasing cement content led to an exponential reduction in porosity (or pore area ratio) and a power increase in pore number, possibly due to the production of hydration products that segment large pores. Relationships were established among peak strength (or AE hits), cement content, and confining stress. However, AE trends diverged from those observed in peak strength due to microstructural modifications under different cement contents and their resulting differences in micromechanical behavior during shearing. General relationships between AE rate and mechanical parameters were established during the initial shearing stage, regardless of cement content and confining stress. Moreover, AE evolution efficiently characterized subtle variations in failure patterns due to its high sensitivity to failure-induced structural modifications. These contributions have the potential to establish a non-destructive field evaluation framework and provide guidelines for the efficient utilization of cemented soils in geological and geotechnical engineering applications.

Alkali-assisted extraction, characterization and encapsulation functionality of enzymatic hydrolysis-resistant prolamin from distilled spirit spent grain

Curcumin is a natural lipophilic polyphenol that exhibits significant various biological properties such as antioxidant and anti-inflammatory properties following oral administration. However, its uses have shown limitations concerning aqueous solubility, bioavailability and biodegradability that could be improved by prolamin-based nanoparticle. In this study, curcumin was encapsulated into prolamin from sorghum (SOP) and wheat (WHP) and distilled spirit spent grain (DSSGP), which was obtained after microbial proteolysis of the former two cereal grains. All the three prolamins showed clear variation of protein profiles and microstructure as confirmed by electrophoresis analysis, disulfide bond determination and Fourier-transform infrared spectroscopy (FTIR). For curcumin-loaded nanospheres (NPs) fabrication, three prolamin-based NPs shared features of spherical shape, uniform particle size, and smooth surface. The average size ranged from 122 to 193 nm depending on the prolamin variety and curcumin loading. In the experiments in vitro, curcumin showed significantly improved UV/thermal stability. Furthermore, DSSGP was more resistant to enzymatic digestion in vitro, hence achieving the controlled release of curcumin in gastrointestinal tract. Collectively, the results indicated the improved bioavailability and biodegradability of curcumin encapsulated by DSSGP, which would be an innovative potential encapsulant for effective protection and targeted delivery of hydrophobic compounds.

Nano-computed tomography analysis of downscaled cement sheath samples: Insights into porosity distribution

Mitigating greenhouse gas emissions from hydrocarbon wells is an industrywide challenge, with microstructural variations in the cement sheaths lining the wells recognized as key factors in forming leakage pathways. To better understand the microstructural variations in cement sheaths and the corresponding mechanisms, downscaled samples simulating rock–cement–casing and casing–cement–casing cement sheaths were prepared and then scanned using nano-computed tomography at resolutions of 11.93 μm and 6.80 μm, respectively. Both the radial and axial porosity of regions of interest were quantified and analyzed. The results showed that radial porosity distributions were quite different between the rock–cement–casing and casing–cement–casing samples. In the rock–cement–casing samples, the radial porosity decreased from the cement–rock to the cement–casing interface due to cement migration, while in the casing–cement–casing samples, the highest radial porosities occurred in both the cement–casing interfaces due to the influence of an interfacial transition zone. The axial porosity distribution was similar in all the rock–cement–casing and casing–cement–casing samples because the porosity decreased from the top to the bottom due to the particle settling phenomenon. These findings enhance our understanding of the factors affecting gas leakage pathways from wells, and the proposed methodology can be used to optimize cement blends to produce effective wellbore barriers.

Experimental investigations of 9 mol.% Mo5SiB2 isopleth phase diagram in Mo–Mo5SiB2–TiC pseudo-ternary system

The present work focuses on gaining a systematic understanding of the microstructure variation and solidification reactions of alloys in the Mo-rich portion of the Mo–Mo5SiB2(T2)–TiC pseudo-ternary system. A series of MoSiBTiC alloys with 9 mol% T2 were selected from the vicinity of the Mo–TiC binary and Mo–Mo5SiB2(T2)–TiC ternary eutectic point to carefully examine the solidification pathway and phase diagram. The solidification reaction temperature of the alloys was detected via an ultra-high-temperature thermal analysis method using blackbody radiation. Solidification was observed in situ using an electromagnetic levitation (EML) apparatus, and the microstructure evolution of solidified EML samples under different thermal histories was characterized. The results provide an experimentally based reassessment of the liquidus surface projection. The primary Moss phase region is shown to be larger than indicated in previously reported data, and a Mo2B primary region should exist in the triangle. As the main result of the investigation of the solidification pathway of a series of MoSiBTiC alloys, an isopleth phase diagram with 9 mol.% T2 in Mo–Mo5SiB2(T2)–TiC pseudo-ternary system is presented.

Mapping spatial superconducting property variations in IG-processed bulk ternary (Gd0.33Y0.13Er0.53)Ba2Cu3Oy

To effectively utilize REBa2Cu3Oy material in various industrial applications, it is crucial to achieve high-quality material with consistent properties. Recent reports indicate that the Infiltration Growth (IG) process, although promising, demonstrates less uneven performance when compared to melt-textured materials. This study focuses on the recently developed single-grain ternary (Gd0.33Y0.13Er0.53)Ba2Cu3Oy material. A total of 36 small pieces were carefully selected for analysis, utilizing scanning electron microscopy (SEM) to examine microstructures, and superconducting transition temperature (Tc) and critical current density (Jc) at 77 K using a SQUID magnetometer. Magnetization results indicate consistent Tc values across the entire sample, while spatial variations in Jc values were observed. Specifically, Jc values no clear trend along the a/b-axis and decreased along the c-axis as the distance from the center increased, correlating with microstructural variations observed through scanning electron microscopy. Quenching experiments conducted on (Gd0.33Y0.13Er0.53)2BaCuO5 (RE211) pellets at 880°C and 1050°C revealed that the heating cycle had a significant impact on both particle and pore sizes in the RE211 secondary phase pellet. Larger pore sizes at the periphery were attributed to the fusion of RE211 secondary phase particles before Ba-Cu-O liquid infiltration. These findings emphasize the importance of further processing optimization to achieve uniform bulk materials for the IG process. Such optimization is crucial to produce uniform bulk superconducting material, essential for everyday applications.

Role of oscillation frequency and amplitude on the microstructure and properties of linear friction welded nickel aluminium bronze joints

This study explores the influence of oscillation frequency and amplitude on the quality of linear friction welded joints using as-cast nickel aluminium bronze. Welding was conducted at 30 Hz, 50 Hz, and 70 Hz oscillated frequencies and amplitudes of 1.5 mm, 2 mm, and 3 mm. The joint’s performance was thoroughly investigated through systematic analysis, including macrostructure examination, peak interfacial temperature measurement, microstructure evaluation, strain assessment, cooling rate determination, microhardness testing, and tensile property characterization. The width of the weld zone varied from 183 μm to 297 μm, and the thermomechanical affected zone (TMAZ) area ranged from 4.48 mm2 to 14.79 mm2 across different process parameters. In the parent material, the volume fraction of the β-phase was as low as 20.2%, contrasting with the dominant α-phase at 79.8%. The average grain size of the lamellar and globular α-phase mixture was 26.4 μm. Notably, the weld zone exhibited extremely refined α-phase grains, with diameters less than 5 μm in all cases. The volume fraction of the β‘-phase increased significantly with higher frequencies, from 15.299% at 30 Hz to 26.98% at 50 Hz, peaking at 40.08% at 70 Hz, leading to varying k phases. This variation in microstructure had a substantial impact on mechanical properties. Tensile strength ranged from 503 MPa to 582 MPa, while ductility varied from 13.5% to 21.7%. Additionally, the hardness of the parent material increased from approximately 155 Hv to 260 Hv. This study demonstrates that controlling the oscillation frequency and amplitude in linear friction welding processes can yield consistent, high-quality welds in nickel aluminium bronze.

Direct FE[formula omitted] failure prediction of fused-filament fabricated parts

The rapid development of additive manufacturing technology and the consequential microstructural variations have brought the simulation aspects into focus. To capture an accurate mechanical response, multiscale methods are used to determine the macroscopic constitutive behaviour. Among these methods, the recently introduced Direct FE2 (DFE2) technique has shown some success in predicting material behaviour via the direct incorporation of representative microstructure volumes into the macroscopic structure. The present study highlights the predictive modelling capabilities of DFE2 linked with an element elimination technique (EET) in investigating the performance of fused-filament fabrication (FFF) samples under tension and compression. Parts were manufactured by FFF with various raster angles to vary the failure characteristics. Their mechanical responses and fracture behaviours were simulated by DFE2 and benchmarked against conventional finite element (FE) analysis, highlighting that the results of DFE2 were competitive against FE. Most importantly, the combination of EET with DFE2 resulted in predictive insights regarding changes in the failure surface for samples with varying raster angles.

Accelerated, physics-inspired inference of skeletal muscle microstructure from diffusion-weighted MRI.

Muscle health is a critical component of overall health and quality of life. However, current measures of skeletal muscle health take limited account of microstructural variations within muscle, which play a crucial role in mediating muscle function. To address this, we present a physics-inspired, machine learning-based framework for the non-invasive estimation of microstructural organization in skeletal muscle from diffusion-weighted MRI (dMRI) in an uncertainty-aware manner. To reduce the computational expense associated with direct numerical simulations of dMRI physics, a polynomial meta-model is developed that accurately represents the input/output relationships of a high-fidelity numerical model. This meta-model is used to develop a Gaussian process (GP) model that provides voxel-wise estimates and confidence intervals of microstructure organization in skeletal muscle. Given noise-free data, the GP model accurately estimates microstructural parameters. In the presence of noise, the diameter, intracellular diffusion coefficient, and membrane permeability are accurately estimated with narrow confidence intervals, while volume fraction and extracellular diffusion coefficient are poorly estimated and exhibit wide confidence intervals. A reduced-acquisition GP model, consisting of one-third the diffusion-encoding measurements, is shown to predict parameters with similar accuracy to the original model. The fiber diameter and volume fraction estimated by the reduced GP model is validated via histology, with both parameters accurately estimated, demonstrating the capability of the proposed framework as a promising non-invasive tool for assessing skeletal muscle health and function.

Impact of temperature variations on BISON predictions of Ag release in AGR-1 and AGR-2 experiments

Understanding and quantifying the release of fission products like silver (Ag) from TRistructural ISOtropic (TRISO) fuel particles is important to assess the safe operation of advanced high temperature reactors. Although the silicon carbide (SiC) layer of TRISO particles is effective as the main fission product barrier, Ag can be released from intact TRISO particles. A mechanistic model for the effective Ag diffusivity, Deff, was previously developed as a function of temperature and microstructure variables informed by atomistic modeling of Ag diffusivity. In this study, we use this model to explore how experimental temperature uncertainties impact the overall predicted Ag release. This analysis indicates that calculated temperature uncertainties have a significant impact on the overall Ag release predictions. Furthermore, we show that the time average volume average (TAVA) temperature is not an appropriate proxy for the detailed temperature histories to predict fission product release due to the Arrhenius dependence of Ag diffusivity with respect to temperature. The detailed temperature histories, therefore, provide the most accurate results and are of most importance for modeling efforts. Overall, this work shows the importance of considering the experimental uncertainty of the temperature on computational predictions of fission product transport and release and the need for more accurate temperature histories from future experiments.

An approach for topology optimization of heat sinks for two-phase flow boiling: Part 2 – Model calibration and experimental validation

Flow boiling offers increased heat transfer coefficients and effective heat capacity rates that can be leveraged by topology optimization (TO) to generate high-performance microchannel heat sinks. Topology optimization of heat sinks having two-phase flows can be accomplished using the homogenization approach wherein designs are represented as spatially varying distributions of microstructures, as demonstrated in Part 1 of this two-part study. Flow and heat transfer within the microstructures are captured using a two-phase mixture model featuring an effective porous medium formulation. However, closure of these governing equations requires empirical correlations for pressure drop and heat transfer that are specific to the operating conditions, geometry, and surface finish. Therefore, it must be demonstrated these available correlations can be successfully calibrated over a range of microstructural variations present within the homogenization framework, so as to attain the required prediction generality and accuracy needed to ensure the resulting designs achieve Pareto-optimality. This Part 2 of our study successfully demonstrates a comprehensive end-to-end process for two-phase flow model calibration, topology optimized design generation, and experimental validation of optimized performance for flow boiling heat sinks. To this end, a TO algorithm with the homogenization approach and a two-phase mixture model is implemented using available flow boiling correlations for microchannels. A set of uniform pin fin calibration samples are additively manufactured and experimentally tested under flow boiling at various flow rates and heat inputs for model calibration. All of the unknown/free coefficients in the adopted correlations are determined by minimizing the error between the model predictions and the experimental measurements using gradient-based optimization. The calibrated topology optimization algorithm is then used to generate a Pareto-optimal set of heat sinks optimized for minimum pressure drop and thermal resistance during flow boiling. Experimental characterization of these additively manufactured heat sinks, unseen during the model coefficient calibration process, reveals that the measured Pareto optimality curve matches that predicted by the topology optimization algorithm. Lastly, a heat sink design is generated for a design space involving multiple hot spots and background heating to showcase the capability of the experimentally calibrated two-phase topology optimization algorithm at handling complex boundary conditions. The optimized heat sink intelligently distributes an adequate amount of coolant flow to each of the heated regions to avoid local dry-out. This work demonstrates a complete framework for two-phase topology optimization of heat sinks through experimental calibration of flow boiling correlations to the porous medium used by the homogenization approach.

Role of micro‐constituents on the fatigue deformation micro‐mechanisms of IN 713 C alloy

AbstractThe cast IN 713 C alloy is extensively used in the aerospace and automobile industries. Even with improved casting methods, the inhomogeneity in the microstructure is still inevitable and causes strain localizations during cyclic loading. So far, the effect of microstructural variables on the low cycle fatigue (LCF) deformation behavior of IN 713 C alloy has rarely been studied. In this study, IN 713 C alloy is LCF tested at 650°C and 750°C for strain amplitudes of 0.35% to 0.6%. The results showed that the deformation heterogeneity resulted from carbides, γ′ precipitates, and γ–γ′ eutectics distribution, governing the LCF failure micro‐mechanisms. The principle fatigue cracks were seen to be initiated from the precipitate‐free zone and oxidized‐surface carbides. It is corroborated that the higher GNDs were observed at carbide/matrix, eutectic/matrix, γ′/matrix interfaces, and in the interdendritic areas where voids and cracks formed. The higher GNDs at these sites facilitate crack initiation and propagation.

Preliminary study on the mechanical behavior of clay in one-dimensional compression with DEM simulations

The mechanical behavior and physical properties of clay are closely associated with its microstructure. Current research on the macroscopic mechanics and physical properties of clay is comprehensive and systematic. However, the microstructural variations underlying these characteristics have been predominantly examined under mercury intrusion porosimetry and scanning electron microscopy, while quantitative and systematic studies are notably limited. This research employs the discrete element method (DEM) simulation to investigate the microscopic responses of clay, simulating one-dimensional compression tests on two clay types: card-house and book-house structures. The analysis of pore size and morphology was conducted using virtual mercury intrusion porosimetry and the pore segmentation method. The clay microstructure was quantitatively characterized by parameters such as pore aspect ratio, orientation distribution, and cumulative pore volume curve. The findings demonstrate that DEM effectively replicates the fundamental mechanical behavior of clay, revealing and explaining the evolution pattern of clay pore structure during one-dimensional compression in terms of platelet alignment adjustment. This macroscopic compression is characterized by variations in pore size distribution, orientation, and aspect ratio.

Micro-macro modeling of tensile behavior of a friction stir welded hybrid joint of AlSi10Mg parts produced by powder bed fusion and casting

Additive manufacturing (AM) has gained considerable interest due to its ability to produce lightweight parts with hierarchical microstructures. However, the current constraints on the build chamber size in powder-bed fusion type AM processes limit its industrial application. A hybrid welded joint, consisting of an AM-processed and a conventionally manufactured part, can be employed to produce larger components. Due to the varying processing conditions, these hybrid welded joints contain a wide range of microstructural heterogeneities, which influences the mechanical properties of the joint. Using a numerical model to predict the mechanical behavior of welded joints by considering the microstructural variations is essential for the safe and reliable implementation of hybrid welded joints. This study aims to predict the local tensile behavior of each region of a hybrid friction-stir welded joint of AlSi10Mg produced by laser-based powder bed fusion and casting using a microstructure-sensitive model as well as the global tensile behavior by considering the properties of each region using a joint macroscopic model. The results from this modeling approach agree well with the experimental results. Therefore, this method can predict the mechanical behavior of hybrid welded joints and can establish the structure–property relationship in each weld region.