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Additive manufacturing, notably laser powder bed fusion (LPBF), excels in producing complex geometries and is widely used in the automotive, aerospace, and naval industries. Laser powder bed fusion enables the creation of components with the required stiffness and strength at a lighter weight than traditional manufacturing methods. Aluminium alloys are particularly promising for laser powder bed fusion in the automotive and aerospace sectors. To enhance the effectiveness of laser powder bed fusion‐produced components, optimized process parameters must be designed for specific materials. This study investigates the influence of processing parameters, scan speed, scan strategy, and hatch space, on the relative density, surface roughness, and microhardness of AlSi12 samples fabricated by laser powder bed fusion. A Taguchi L27 orthogonal array was used to systematically analyze the effects of these parameters. A regression model was developed and evaluated through analysis of variance using signal‐to‐noise (S/N) ratios to identify optimal parameter values. Results indicated that the scan pattern significantly affects relative density, while hatch space impacts surface roughness and microhardness. Optimal solutions were obtained through multi‐objective optimization using the non‐dominated sorting genetic algorithm (NSGA‐II) and Pareto search algorithms. Experimental validation showed average errors of 0.483 % and 0.461 % for NSGA‐II and Pareto search algorithms, respectively. [ABSTRACT FROM AUTHOR]

Porous materials are known for their excellent energy absorption capability and, thus, are widely used in anti-impact applications. However, how the pore shape and size impact the failure mechanism and overall behavior of the porous materials under impact loading is still unclear or limitedly touched. Instead of using homogeneous solids for the porous material model, pores with various shapes and sizes were implanted in a solid to establish the porous materials that have true porous structures, which permits exploration of the local failure mechanism. The results revealed that differently shaped holes have two different dominant deformation modes. And due to their different local stress distributions, they enter the plastic phase earlier and, thus, have higher specific energy absorption. Meanwhile, the model changes from hardening to a quasi-zero stiffness model as the hole size increases. The application of this work can be extended into the field of impact resistance. [ABSTRACT FROM AUTHOR]

Additive manufacturing from metal powders using selective laser melting technology is gaining increasing interest in various industries. The purpose of this study was to determine the effect of changes in process parameter values on the relative density, microstructure and mechanical properties of Ti-6Al-4V and Ti-6Al-7Nb alloy samples. The experiment was conducted in response to a noticeable gap in the research on the manufacturability of the Ti-6Al-7Nb alloy in SLM technology. This topic is significant given the growing interest in this alloy for biomedical applications. The results of this study indicate that by properly selecting the volumetric energy density (VED), the relative density of the material produced and the surface roughness of the components can be effectively influenced. Microstructural analyses revealed similar patterns in both alloys manufactured under similar conditions, characterized by columnar β phase grains with needle-like α' phases. Increasing the VED increased the tensile strength of the fabricated Ti-6Al-4V alloy components, while the opposite effect was observed for components fabricated from Ti-6Al-7Nb alloy. At the same time, Ti-6Al-7Nb alloy parts featured higher elongation values, which is desirable from the perspective of biomedical applications. [ABSTRACT FROM AUTHOR]

The processing of pure copper (Cu) has been a challenge for laser-based additive manufacturing for many years since copper powders have a high reflectivity of up to 83% of electromagnetic radiation at a wavelength of 1070 nm. In this study, Cu particles were coated with sub-micrometer tungsten (W) particles to increase the laser beam absorptivity. The coated powders were processed by powder bed fusion-laser beam for metals (PBF-LB/M) with a conventional laser system of <300 watts laser power and a wavelength of 1070 nm. Two different powder manufacturing routes were developed. The first manufacturing route was gas atomization combined with a milling process by a planetary mill. The second manufacturing method was gas atomization with particle co-injection, where a separate W particle jet was sprayed into the atomized Cu jet. As part of the investigations, an extensive characterization of powder and additively manufactured test specimens was carried out. The specimens of Cu/W powders manufactured by the milling process have shown superior results. The laser absorptivity of the Cu/W powder was increased from 22.5% (pure Cu powder) to up to 71.6% for powders with 3 vol% W. In addition, a relative density of test specimens up to 98.2% (optically) and 95.6% (Archimedes) was reached. Furthermore, thermal conductivity was measured by laser flash analysis (LFA) and thermo-optical measurement (TOM). By using eddy current measurement, the electrical conductivity was analyzed. In comparison to the Cu reference, a thermal conductivity of 88.9% and an electrical conductivity of 85.8% were determined. Moreover, the Vickers hardness was measured. The effect of porosity on conductivity properties and hardness was investigated and showed a linear correlation. Finally, a demonstrator was built in which a wall thickness of down to 200 µm was achieved. This demonstrates that the Cu/W composite can be used for heat exchangers, heat sinks, and coils. [ABSTRACT FROM AUTHOR]

Due to the wide particle size distribution of coral sand, There are significant differences in mechanical behaviour of coral sand with different particle size distribution. It is of great significance to propose a quantitative analysis method for mechanical properties considering the effect of gradation. In this study, 27 groups of coral sand specimens with particle size ranging from 5 mm to 0.125 mm were prepared. The consolidated undrained (CU) triaxial shear tests were carried out and the influence of gradation and relative density on the shear characteristic were discussed. The grading and relative density of coral sand are controlled by the median particle size (d50) and relative density (Dr), The results show that the peak deviator stress decreased, and the effective internal friction angle first increased and then decreased with the increase of d50. Both the peak deviator stress and effective internal friction angle of coral sand increase with the relative density. A parabolic relationship was founded between the effect internal friction and d50 as Dr was constant. The effective friction angle peaked when d50 was 2 mm. Finally, a calculation method of shear strength parameter considering the gradation and relative density of coral sand was proposed. [ABSTRACT FROM AUTHOR]

An expanding spherical cavity of a zero initial radius surrounded by an infinite porous rigid/plastic medium is considered. The material is assumed to obey the flow theory of plasticity based on a yield criterion and its associated flow rule. The yield criterion depends on the linear and quadratic stress invariants. No restriction is imposed on this dependence, except for the standard requirements imposed on the yield criteria. It is shown that the solution can be extended into the rigid region. The yield criterion approaches the von Mises yield criterion as the relative density approaches unity. Some equations contain the expression 0/0 at the rigid/plastic boundary. In this respect, the present solution is qualitatively different from available elastic/plastic solutions. However, the solution does not provide the solution for the von Mises yield criterion as a particular case. Numerical results are presented for Green's yield criterion. These results follow physical expectations concerning the distributions of the relative density, the radial velocity, and the radial stress. The solution is adapted for expanding a cavity of a non-zero initial radius. The pressure required for expanding the cavity is calculated. [ABSTRACT FROM AUTHOR]

The optimization of processing parameters is indispensable for the laser powder bed fusion (L-PBF) process. The deposited energy density (DED) is one of the process indexes for the L-PBF process and has a simplified formula of P·v-0.5, where P is the laser power, and v is the scan speed. This parameter describes the change in the relative density and the melt pool morphology with laser power and scan speed well, whereas it does not include the effect of other processing parameters, e.g., hatch spacing (S). In the present study, an attempt was made to incorporate the effect of S into DED. Al-12Si (mass％) alloy cube samples were fabricated by L-PBF under various P, v, and S, for evaluating the relative density and the melt pool morphology. The melt pool depth and width of L-PBF-manufactured Al-12Si alloy increased linearly with P·v-0.5 and did not exhibit a clear correlation with S. Based on the experimental observation, the effect of hatch spacing on DED was estimated to be S-0.5, and a new index of P·v-0.5·S-0.5 was proposed. This index described the change in the relative density of the L-PBF-manufactured Al-12Si alloy with laser conditions (P, v, and S) well when the thermal conduction mode melting was dominant. This study also indicated the limitation of the applicability of P·v-0.5·S-0.5 under the keyhole or transition mode melting. [ABSTRACT FROM AUTHOR]

As the critical dynamic parameters for soil, an extensive examination of the dynamic elastic modulus Ed and damping ratio λ in coarse-grained soil is of significant theoretical and practical importance. Currently, there is a scarcity of experimental equipment and methods for measuring the dynamic elastic modulus and damping ratio of coarse-grained soils. Moreover, studies examining the influence of relative density on these parameters in coarse-grained soils are largely absent. To investigate the behavior of the dynamic elastic modulus and damping ratio in coarse-grained soil under varying relative densities, a number of dynamic triaxial tests were conducted on a specific coarse-grained soil using the DYNTTS type dynamic triaxial test apparatus. The findings reveal that, under various gradations, the Ed of coarse-grained soils exhibits a decreasing trend with increasing dynamic strain, a trend that intensifies with higher relative densities. Additionally, as relative density increases, the degradation rate of the dynamic shear modulus ratio Gd/Gdmax to dynamic shear strain γd curve escalates. The maximum dynamic shear modulus Gdmax rises with increasing relative density Dr, displaying a linear relationship between Gdmax and Dr. Furthermore, both the increasing rate of λ to γd curve and the maximum damping ratio λmax progressively diminish with the escalation of relative density Dr. Notably, the maximum damping ratio has a power function relationship with the relative density. [ABSTRACT FROM AUTHOR]

The versatility of titanium (Ti) allows it to be employed in various industries, from aerospace engineering to medical technology, highlighting its significance in modern manufacturing and engineering processes. Spark plasma sintering (SPS) is currently being explored to enhance its properties further and broaden its application range. The current study focuses on exploring and optimizing the effect of SPS temperature (800, 900, 1000, 1100, 1200, and 1400 °C) on pure Ti sintered at 60 MPa in a controlled argon environment with a dwell time of 5 min. All the prepared samples were highly dense with a relative density above 99%, but exhibited significant variations in grain size (10 to 57 µm), tensile yield strength (488 to 700 MPa), ultimate tensile strength (597 to 792 MPa), and ductility (4 to 7%). A microstructural investigation was performed using XRD, SEM, and EDS to predict the influence of sintering temperature on the formation of different phases. The XRD patterns of all sintered samples showed the presence of single-phase α-Ti with hexagonally close-packed Ti. This work is a step forward in optimizing SPS-processed Ti's physical and mechanical properties for enhanced structural and biomedical applications. [ABSTRACT FROM AUTHOR]

In this study, we first developed an artificial intelligence (AI) that estimates relative densities (RD) of silicon nitride ceramics from the process conditions. We then constructed a multi-layer AI that predicts the thermal conductivities (TC) from the above process conditions using an RD obtained by the developed AI. The RD-predictive AI utilized input data (explanatory variables) which represent the effects of main powders, sintering additives, organic sacrificial pore formers and heat treatments (nitriding and/or sintering), whereas the TC-predictive AI exploited the predicted RD as well as the aforementioned explanatory variables. Both the AIs successfully improved the prediction accuracy by incorporating the types and concentrations of sintering additives and conditions into the explanatory variables. These AIs exhibit potential to predict even other properties of silicon nitride ceramics prior to the real fabrication. [ABSTRACT FROM AUTHOR]

This study investigates the effects of process parameters in the powder bed fusion–laser beam (PBF-LB) process on IN939 samples. The parameters examined include laser power (160, 180, and 200 W), laser scanning speed (400, 800, and 1200 mm/s), and hatch distance (50, 80, and 110 μm). The study focuses on how these parameters affect surface roughness, relative density, defect formation, and the microstructure of the samples. Surface roughness analysis revealed that the average surface roughness (Sa) values of the sample ranged from 4.6 μm to 9.5 μm, while the average height difference (Sz) varied from 78.7 μm to 176.7 μm. Furthermore, increasing the hatch distance from 50 μm to 110 μm while maintaining constant laser power and scanning speed led to a decrease in surface roughness. Relative density analysis indicated that the highest relative density was 99.35%, and the lowest was 93.56%. Additionally, the average porosity values were calculated, with the lowest being 0.06% and the highest reaching 9.18%. Although some samples had identical average porosity values, they differed in porosity/mm2 and average Feret size. Variations in relative density and average porosity were noted in samples with the same volumetric energy density (VED) due to different process parameters. High VED led to large, irregular pores in several samples. Microcracks, less than 50 μm in length, were present, indicating solidification cracks. The microstructural analysis of the XZ planes revealed arc-shaped melt pools, columnar elongated grains aligned with the build direction, and cellular structures with columnar dendrites. This study provides insights for optimizing PBF-LB process parameters to enhance the quality of IN939 components. [ABSTRACT FROM AUTHOR]

A series of model tests about vibroflotation were conducted to investigate soil property change on silica sand foundations, especially for earthquake-resistant behavior. First, the process of double-point vibroflotation was investigated with a simulative vibrator system. Thereafter, shaking table tests were conducted to evaluate seismic responses. The results illustrated that the relative density was significantly enhanced after the first vibratory period, with the highest enhancement appearing at the vibropoint in the plane and the middle layer along the depth. As for the seismic tests, the excess pore pressure ratios show that the vibroflotation can apparently improve the liquefaction-resistance capacity of the silica sand foundation. Moreover, the shear stiffness of the unconsolidated foundation decreases distinctly under 0.2g earthquake motion, while the consolidated foundation remains capable of transmitting acceleration. Inflicting white noise before the any earthquake motion and after 0.2g earthquake, the result shows that the predominant frequency of unconsolidated foundation decreases apparently. The dynamic shear stress–strain curves were compared, while the development law of the time history was also investigated. These results demonstrated that this method can obviously prevent the shear stiffness attenuation. To sum up, the vibroflotation compaction method can make a great densification and increase the earthquake-resistant capacity. [ABSTRACT FROM AUTHOR]

This work aims at improving the sintering property of zirconia toughened alumina (ZTA) granulated powder.ZTA slurries were prepared through ball milling using alumina powder with different particle sizes (d50:1.72 μm,3.48 μm and 13 nm) and yttria stabilized zirconia (YSZ) as the main starting materials,adding binders and dispersants.The effect of the YSZ extra-addition (0,5%,10%,15% and 20%,by mass) on the rheological property of the slurries was investigated.ZTA granulated powders were prepared using the spray drying method,and then the powders were pressed into shapes and fired at different temperatures (1 520,1 600,and 1 680 °).The linear shrinkage and relative density of the fired samples were determined.The results show that:(1)the ZTA slurries exhibit shear thinning behavior and possess a yield stress;the rheological properties of the slurries are well-described by the Herschel-Bulkley model,with a high correlation coefficient (>0.98);(2)the particle size of the prepared ZTA granulated powders is mainly within the range of 125 to 45 μm,demonstrating a wide distribution;(3)the optimal formulation is 99 mass% activated alumina powder (d50=1.72 μm),1 mass% nano-alumina (d50=13 nm),and 15 mass% YSZ (extra-adding);this formulation results in a Carr coefficient of 8.62%,a water content of 0.22%,and an angle of repose of 25.2°;after firing at 1 600 °C for 2 h,the sample exhibits a relative density of 94.8% and a linear shrinkage rate of 18.2%. [ABSTRACT FROM AUTHOR]

Equations for converting between relative density and percent by mass extract based upon physically meaningful values (rather than fitted parameters) are derived from physical principles. An exact equation and two approximate formulas using one and two physically meaningful parameters respectively are given based on the partial specific volumes of sucrose and water in solution, which are calculated for sucrose concentrations varying between 0 and 20% by mass fraction. The predictions of these equations are compared to the American Society of Brewing Chemists (ASBC) tables and the accuracy of the predicted values is analyzed. The root mean squared error over the entire range of the ASBC tables of the approximate formula with two parameters is less than 0.016°P and that of the formula using only one parameter is less than 0.023°P. The approximate formula with one parameter provides a simple and easily remembered, but nevertheless highly exact means for any brewer to calculate extract without specialized analytical devices. [ABSTRACT FROM AUTHOR]

The undrained shearing behavior of the Jhelum Riverbed sands and the effect of fines content on their overall response and their static liquefaction potential are still elusive. In this context, the present study aims to understand the undrained shearing response and static liquefaction potential of Jhelum riverbed sands through a series of isotropically consolidated undrained compression (CIUC) triaxial tests. The effect of sand type and fines content were established through CIUC triaxial tests conducted on clean sands obtained from three different locations (Khanabal, Rajbagh, and Sopore) along the Jhelum River and sand-silt mixtures. Results showed that volumetric compressibility (mv) decreased by 67, 65, and 46% as the relative density increased from 15 to 50% for KS, RS, and SS sands, respectively. Compared to clean sands, an increase of 23 and 15% in mv was observed with the addition of 7 and 14% non-plastic fines, respectively. An increase in the undrained shearing resistance by factors of 2.12, 3.08, and 1.98 for KS, RS, and SS, respectively, is observed as the relative density increases from 15 to 50%. An increase in undrained strength by 79.2% is observed when the initial effective confining pressure ( p i ′ ) is increased from 50 to 150 kPa. It was also observed that Jhelum sands follow normal behavior of increasing contractile tendency as p i ′ increased from 50 to 150 kPa. Specimens with larger mean grain diameter (D50) and lower coefficient of uniformity (CU) values exhibited higher undrained strength as well as higher liquefaction resistance. Higher roundness and sphericity values facilitate a higher generation of excess pore water pressure, resulting in higher liquefaction potential. With the addition of non-plastic fines, the Sopore Sand-silt mixture exhibited higher liquefaction potential, more strain-softening behavior, and higher excess pore pressure, resulting in 83 and 51% reduction in p i ′ at 7 and 14% fines content, respectively. A unique critical state line in q - p ′ space is observed for sand silt mixtures. [ABSTRACT FROM AUTHOR]

To explore the feasibility of geogrid reinforcement as a promising countermeasure to improve the liquefaction and post-liquefaction resistance of calcareous sand, extensive undrained monotonic and multi-stage triaxial tests were performed on unreinforced and geogrid reinforced calcareous sand with different relative densities. The test results illustrate that pore pressure generation curves of unreinforced and reinforced calcareous sand gradually evolve from S-shaped to hyperbolic-shaped with the increase in relative density, cyclic stress ratio, and effective confining pressure. Following this, a pore pressure model applicable to both unreinforced and reinforced calcareous sand is proposed. The liquefaction resistance of calcareous sand increases with the increase in relative density, whereas an elevated cyclic stress ratio increases its liquefaction susceptibility. A virtually unique relationship can be observed between the liquefaction resistance normalized to the product of phase transformation strength ratio and relative density against the number of cycles for triggering liquefaction, providing an effective means of early assessing sand liquefaction resistance. Moreover, the geogrid exhibits excellent reinforcement efficiency in enhancing the liquefaction resistance of calcareous sand at relative densities of 50% and 70%. During the post-liquefaction stage, increasing relative density and geogrid reinforcement can accelerate the recovery of stiffness and strength for liquefied calcareous sand and improve the post-liquefaction strength. In general, geogrid reinforcement is considered a good alternative to densification for improving the engineering properties of calcareous sand and offers great application prospects in marine engineering construction. • The effects of geogrid reinforcement and relative density on the liquefaction and post-liquefaction behaviors of calcareous sand are investigated. • A pore pressure model applicable to both unreinforced and reinforced calcareous sand is proposed. • The inclusion of geogrid enhances the liquefaction resistance of calcareous sand. • Increasing relative density and geogrid reinforcement accelerate the recovery of stiffness and strength for liquefied calcareous sand and improve the shear strength during the post-liquefaction stage. • Geogrid reinforcement is considered a good alternative to densification for improving the engineering properties of calcareous sand and offers great application prospects in marine engineering construction. [ABSTRACT FROM AUTHOR]

A series of 24 model laboratory tests had been performed to examine the pile response nearby the slope. The main objective of the study was to quantify the effect of the edge distance and relative density on the pile response in sloping ground with respect to level ground case. The ground slope had been maintained as 1 vertical to 1.5 horizontal for sloping ground conditions. Experiments had been performed with varying edge distances from 0 to 12 times diameter under three different relative densities as 25%, 52% and 72%. The pile response in horizontal ground condition had been acquired at the same relative density to enumerate the effect of the ground slope. The deflection and bending moment were considerably augmented for the sloping ground surface. However, values had been witnessed to decrease with the increase in the edge distance. An increase in the relative density resulted in a reduction in the pile response. A generalised p-y curve is being suggested for sloping ground conditions. Reduction factors are being reported to account for the slope effect. These can be applied to the initial stiffness and ultimate soil resistance of the p-y curve in the level ground case. [ABSTRACT FROM AUTHOR]

Liquefaction of clean and silty sands remains to be an important problem during earthquakes. Even though many factors are known to influence liquefaction behavior, the influence of density index parameter and fines content (FC) are among the most important parameters. In this study, the effect of relative density (Dr) on liquefaction behavior of clean and silty sands was investigated by cyclic direct simple shear tests on two different silty sands at various FC. Several different relationships affected from Dr are revisited or investigated including number of cycles to liquefaction (NL) and cyclic resistance ratio (CRR). It was found that liquefaction resistance-fines content-relative density relationship is much more complex than previously thought. This is because CRR-Dr lines of clean and/or silty sands may cross each other at specific relative densities, which may cause the liquefaction resistance of a clean sand to be either smaller, equal or greater than the liquefaction resistance of a silty sand with the same base sand dependent on the magnitude of relative density. The mentioned behavior is also confirmed on different clean and silty sands tested in literature. [ABSTRACT FROM AUTHOR]

In this work, the tungsten‐copper composites were fabricated by binder jet 3D printing technology. The effects of different printing layer thicknesses (50 μm to 100 μm) on the green density and green strength were investigated. Then, under the optimal layer thickness, the effects of different sintering temperatures (1300 °C to 1600 °C) on the microstructure and densification of tungsten‐40 wt.–% copper composites were studied. The experimental results showed that when the printing layer thickness was set as a lower value (50 μm), the tungsten‐40 wt.–% copper green part had the best strength and its density reached a maximum value of 60.73 %. After sintering for green parts printed with 50 μm layer thickness, the relative density, thermal conductivity and electrical conductivity of sintered parts first increased and then decreased with increasing sintering temperature. In our experiments, the tungsten‐40 wt.–% copper sample fabricated by binder jet 3D printing with a printing layer thickness of 50 μm under a sintering temperature of 1500 °C displayed the best properties, in which the relative density, thermal conductivity and electrical conductivity were 97.04 %, 228 W⋅m−1⋅K−1 and 46.5 % IACS, respectively. [ABSTRACT FROM AUTHOR]

Bio-inspired gyroid triply periodic minimum surface (TPMS) lattice structures have been the focus of research in automotive engineering because they can absorb a lot of energy and have wider plateau ranges. The main challenge is determining the optimal energy absorption capacity and accurately capturing plastic plateau areas using finite element analysis (FEA). Using nTop's Boolean subtraction method, this study combined walled TPMS gyroid structures with a normal TPMS gyroid lattice. This made a composite TPMS gyroid lattice (CTG) with relative densities ranging from 14% to 54%. Using ideaMaker 4.2.3 (3DRaise Pro 2) software and the fused deposition modeling (FDM) Raise3D Pro 2 3D printer to print polylactic acid (PLA) bioplastics in 1.75 mm filament made it possible to slice computer-aided design (CAD) models and fabricate 36 lattice samples precisely using a layer-by-layer technique. Shimadzu 100 kN testing equipment was utilized for the mechanical compression experiments. The finite element approach validates the results of mechanical compression testing. Further, a composite CTG was examined using a field emission scanning electron microscope (FE-SEM) before and after compression testing. The composite TPMS gyroid lattice showed potential as shock absorbers for vehicles with relative densities of 33%, 38%, and 54%. The Gibson–Ashby model showed that the composite TPMS gyroid lattice deformed mainly by bending, and the size effect was seen when the relative densities were less than 15%. The lattice's relative density had a significant impact on its ability to absorb energy. The research also explored the use of these innovative foam-like composite TPMS gyroid lattices in high-speed crash box scenarios to potentially enhance vehicle safety and performance. The structures have tremendous potential to improve vehicle safety by acting as advanced shock absorbers, which are particularly effective at higher relative densities. [ABSTRACT FROM AUTHOR]

Preparing uniform soil samples is essential for obtaining reliable results in the physical modeling of geotechnical structures, such as retaining walls and piles. The air pluviation method is a common approach adopted by researchers and engineers to reconstitute large-scale sand beds with high degrees of homogeneity and uniformity. This paper investigates the uniformity of sand beds prepared using the conventional manual sand pouring method, its potential impact on test results, and how creating a more uniform sand bed can enhance the reliability of the results. To achieve this goal, a novel portable sand pluviator capable of reconstituting sand beds inside a frustum confining vessel (FCV) apparatus at a high level of uniformity is adopted. The pluviator is utilised to prepare sand beds inside the FCV, and the uniformity of the resulting sand bed is assessed and compared with those prepared using the manual pouring method. Next, in order to investigate the influence of uniformity of sand beds on the outcomes of a large-scale test, a large-scale experiment involving the determination of the bearing capacity of a open-ended single-helix helical pile within the FCV is considered. Numerical analysis investigates how sand bed uniformity affects bearing capacity without extensive testing. It uses data from initial research and employs Latin Hypercube Sampling to determine the required simulations for accurate measurement of the impact of sand bed uniformity on bearing capacity. The results of this set of numerical simulations are then thoroughly analysed to assess the impact of the sand pouring method on the reliability of the experimental outcomes. Analysis of the results show that preparation of uniform sand beds at the desired relative density is one of the key elements in obtaining accurate and reliable experimental results in geotechnical physical modelling problems. [ABSTRACT FROM AUTHOR]

Long-term cyclic loading can have a significant effect on the modulus of sand, and the influence on saturated coral sand has yet to be established. In this paper, the significant influence of non-plastic fines content (FC) and relative density (Dr) on dynamic elastic modulus (E) of saturated coral sand has been evaluated by a series of cyclic triaxial drainage tests. The results show that the dynamic elastic modulus increases rapidly at the beginning of loading; then the growth slows down and finally stabilizes. In general, the development of E is influenced collectively by FC, Dr and cyclic stress ratio (CSR). The initial dynamic elastic modulus Ed-1 and steady-state dynamic elastic modulus Ed-s increase with the increase of Dr, and decrease as FC increases. The linear fitting equations are given by introducing the equivalent skeleton void ratio esk*. Furthermore, the relative dynamic elastic modulus Er is defined as the ratio of Ed-N to Ed-s, and the prediction equation for Er was developed to provide a basis for the engineering mechanical parameters of coral sands under long-term loads.

The phenomenon of fine particle migration through the voids of the granule skeleton under the seepage force is called suffusion. Relative density, original fine particle content, and gap ratio are thought to play vital roles in the suffusion process. This paper investigates the effect of geometrical characteristics (i.e., original fine particle content, gap ratio, and relative density) on soil structure and mechanical performance (i.e., small strain shear modulus) using the bender element method technique. The small strain shear modulus (G0) is used as a mechanical parameter to evaluate the shear stress transmission of the soil structure along with the erosion process. The comparison between erosion percentage and vertical strain change suggests the alteration in soil fabric after soil erosion. The G0 monitoring results show that packings with a higher original fine particle content have a lower G0 value, whereas the gap ratio and relative density present a positive relationship with G0.

Cellular materials offer industries the ability to close gaps in the material selection design space with properties not otherwise achievable by bulk, monolithic counterparts. Their superior specific strength, stiffness, and energy absorption, as well as their multi-functionality, makes them desirable for a wide range of applications. The objective of this paper is to compile and present a review of the open literature focusing on the energy absorption of periodic three-dimensional cellular materials. The review begins with the methodical cataloging of qualitative and quantitative elements from 100 papers in the available literature and then provides readers with a thorough overview of the state of this research field, discussing areas such as parent material(s), manufacturing methods, cell topologies, cross-section shapes for truss topologies, analysis methods, loading types, and test strain rates. Based on these collected data, areas of great and limited research are identified and future avenues of interest are suggested for the continued maturation and growth of this field, such as the development of a consistent naming and classification system for topologies; the creation of test standards considering additive manufacturing processes; further investigation of non-uniform and non-cylindrical struts on the performance of truss lattices; and further investigation into the performance of lattice materials under the impact of non-flat surfaces and projectiles. Finally, the numerical energy absorption (by mass and by volume) data of 76 papers are presented across multiple property selection charts, highlighting various materials, manufacturing methods, and topology groups. While there are noticeable differences at certain densities, the graphs show that the categorical differences within those groups have large overlap in terms of energy absorption performance and can be referenced to identify areas for further investigation and to help in the preliminary design process by researchers and industry professionals alike. [ABSTRACT FROM AUTHOR]

AbstractThe dynamic shear modulus G and its degradation tendency G/Gmax are essential parameters for characterizing the dynamic properties of soil. Coastal facilities constructed on calcareous sand foundations are subjected to multiple types of cyclic loadings. To investigate the effects of the uniformity coefficient Cu, effective confining pressure σ0′, relative density Dr, and median grain size d50 on the dynamic G and its degradation rule for calcareous sand, a set of resonant column tests is conducted on calcareous sand with different grain-size-distribution curves. The experimental results clearly show that the G degrades faster for calcareous sand with a lower σ0′ and a larger Cu. By contrast, the degradation of the G is affected less by Dr and d50. The G/Gmax values decreased slightly as γ increased but remained less than 10−5, whereas the G/Gmax curve descended rapidly as γ increased beyond 10−5. Based on the test results obtained in this study and previously published data, a new mathematical model characterizing the degradation tendency of G/Gmax with respect to the shear strain level of calcareous sands with different gradation conditions is proposed. The relevant parameters associated with the proposed model are correlated with Cu and σ0′. [ABSTRACT FROM AUTHOR]

Soil arching is significantly influenced by relative density, while its mechanisms have barely been analyzed. A series of DEM numerical simulations of the classical trapdoor test were carried out to investigate the multi-scale mechanisms of arching development and degradation in granular materials with different relative density. For analysis, the granular assembly was divided into three zones according to the particle vertical displacement normalized by the trapdoor displacement δ. The results show that before the maximum arching state (corresponding to the minimum arching ratio), contact forces between particles in a specific zone (where the vertical displacement of particles is larger than 0.1δ but less than 0.9δ) increase rapidly and robust arched force chains with large particle contact forces are generated. The variation in contact forces and force chains becomes more obvious as the sample porosity decreases. As a result, soil arching generated in a denser particle assembly is stronger, and the minimum value of the arching ratio is increased with the sample porosity. After the maximum arching state, the force chains in this zone are degenerated gradually, leading to a decrease in particle contact forces in microscale and an increase in the arching ratio in macroscale. The recovery of the arching ratio after the minimum value is also more significant in simulations with a larger relative density, as the degeneration of contact force chains is more obvious in denser samples. These results indicate the importance of contact force chain stabilities in specific zones for improving soil arching in engineering practice. [ABSTRACT FROM AUTHOR]

High-entropy ceramics have great potential for different applications due to their unique properties. However, the optimization of grain size and densification on high-entropy ceramics has still not been investigated. This study utilized raw material design and high-energy ball milling technology to create a kind of (Ti 19.28 V 17.77 Cr 17.11 Zr 6.29 N 39.56) 92.32 (ZrO 2) 7.68 high-entropy nitride composites with fine grain size and high densification. It displayed that CrN x could be prepared from raw material Cr 2 N by high-energy ball milling technology, which could decompose at lower temperatures, thus promoting the formation of high-entropy ceramic solid solutions. The study demonstrated the importance of CrN x via the comparation of CrN x in high-entropy systems (Ti 19.28 V 17.77 Cr 17.11 Zr 6.29 N 39.56) 92.32 (ZrO 2) 7.68 with CrN in high-entropy systems (Ti 18.6 V 17.82 Cr 12.12 Zr 7.08 N 44.36) 93.93 (ZrO 2) 6.07. Using XRD, SEM, EDS, displacement monitoring, and the phase diagram calculated by Thermo-Calc, the differences between the two systems were explored, particularly in terms of mechanical properties and grain size. The study showed that the grain size of (Ti 19.28 V 17.77 Cr 17.11 Zr 6.29 N 39.56) 92.32 (ZrO 2) 7.68 was controlled within 3 μm, with densification of 98.78 %. The Vickers hardness, bending strength, and fracture toughness at room temperature reached an average of 2248HV 0.5 , 200 MPa, and 9.428 MPa m1/2, respectively. The study highlighted the importance of selecting specific materials and combining them with corresponding preparation processes to achieve joint optimization of densification and grain size. [ABSTRACT FROM AUTHOR]

In this study, the effects of relative density and confining pressure on the shear characteristics of round gravel are investigated using a large-scale triaxial apparatus and the discrete element method. A simple and efficient numerical method for simulating flexible membranes is introduced. The results show that the stress-strain curves develop from hardened to softened type with increasing relative density, while the stress-strain curves develop from softened to hardened type with increasing confining pressure. As the axial strain increases, the strong contact force chains are vertically distributed, and the larger the relative density and confining pressure, the greater the number and thickness of the strong contact force chains. In the shear process, the distribution of average normal and tangential contact forces show "peanut-shaped" and "petal-shaped", respectively. The increase in relative density increases the anisotropy of the specimen, while the increase in confining pressure results in a decrease. A linear relationship exists between the macroscopic stress ratio and the anisotropy coefficient. The anisotropy coefficient of the normal contact force provides the greatest contribution to the macroscopic shear strength (about 55%), followed by the anisotropy coefficient of the contact normal (about 26%) and that of the tangential contact force (about 19%). [ABSTRACT FROM AUTHOR]

The dynamics, duration and specificity of alcoholic fermentation are among the factors determining the quality of white wines. These features depend mostly on technological parameters such as temperature (16°C, 20°C) and amount of total sugars (180 g/dm³, 220 g/dm³). The aim of the current study was to assess the fermentation activity of yeast Saccharomyces cerevisiae from EXCELLENCE® line, intended for production of wines under Organic and National Organic Program (NOP) standards. The used yeasts have a high fermentation activity and are characterized with relatively fast alcoholic fermentation. The result showed that there was no difference in the dynamics of alcoholic fermentation of yeast strains from the used lines. The quick fermentation of sugars was observed in the initial (lag phase) and in the final stage (silent fermentation). However, the experimental variants with different sugar contents completed the process at the same time. A straightforward relationship between the fermentation of sugars and the changes in pH was not observed. According to the mass of the obtained yeast lees, there was a clear difference between all experimental variants. Nevertheless, the mass of the obtained yeast lees for all variants was lower than the normatively allowed [ABSTRACT FROM AUTHOR]

Calcareous sand is the main geomaterial available for island-reef reclamation construction projects in the South China Sea. To clarify the effect of particle breakage on the dilatancy of calcareous sand, multiple consolidated-drained triaxial shear tests were conducted on calcareous gravelly sand (CGS) under different conditions. On this basis, dilatancy assessment indices were constructed from the perspectives of stress ratio and dilatancy ratio, and their relationships with the initial physical parameter and stress level of CGS were established. Next, the variations in particle breakage of CGS with compactness and stress level were explored, and a physical model was proposed to predict particle breakage according to plastic work. Finally, the relationship between dilatancy and particle breakage was established for CGS. The results lay a research foundation for developing an elastoplastic constitutive model considering the effect of particle breakage for CGS. In this study, the dilatancy of calcareous sand was investigated under varying relative densities and effective confining pressures. Then, the variations in the particle breakage of calcareous sand with compactness and stress level were revealed. Finally, the relationship between dilatancy and particle breakage of calcareous sand was established. [ABSTRACT FROM AUTHOR]

In this work, the electrical and thermal conductivities of open-cell porous aluminium materials produced by replication casting method are investigated and the correlations between them studied. The four-point probe method was used to measure the electrical conductivity of the samples, while the C-therm analyser was used to experimentally determine the thermal conductivity of the cellular materials. The results show that both electrical and thermal conductivities of the porous samples increase as their relative density is increased. Comparison of the measured data with theoretical models shows that the scaling function with a dynamic exponent equal to 1.55 fits the experimental data for electrical conductivity. In addition, an empirical relationship was found to exist between measured electrical and thermal conductivities, while a modified Wiedemann-Franz law was also deduced to correlate the electrical and thermal conductivities of the porous aluminium materials. [ABSTRACT FROM AUTHOR]

Vat photopolymerization is an effective and economical method for preparing ceramic specimens with complex structures. However, the improper selection of process parameters during the preparation process limits the scope of its application. In this study, the most suitable shear rate was determined based on the solid content and rheological properties of the ceramic slurry. In addition, the specific printing‐process parameters were objectively selected, and the gray correlation method was used to determine the improved weight resolution coefficient through orthogonal experiments combined with the entropy weight method to select the most suitable printing parameters. Finally, the main debinding and sintering parameters that affect the heat treatment performance were considered, and multiple characterization methods were used to detect the specimens and study the impact of parameter changes on specimen performance. The experimental results show that when the laser power is 210 mW, the slice layer thickness is.04 mm, the scanning spacing is.05 mm, and the filling mode is XY, the green bodies have the best forming quality. When the sintering temperature is 1600°C, and the holding time is 4 h, the specimens have the best mechanical properties (the flexural strength reaches 114 MPa). [ABSTRACT FROM AUTHOR]

Liquefaction is considered one of the most common phenomena resulting in serious damage during earthquakes. Appropriate estimation of liquefaction potential, damping characteristics and shear modulus of soil under dynamic loading is crucial for precise dynamic response analysis and soil modelling problems. The present paper emphasises the influence of relative density, confining pressure, and shear strain on the cyclic response of sand specimens. A parametric study comprising varying relative densities (35–65%), confining pressures (100–150 kPa), and shear strain (0.015–1.3%) under 1 Hz loading frequency was conducted in the laboratory. The sand samples were subjected to a series of consolidated undrained cyclic triaxial tests. It is observed that with an increase in confining pressure and relative density, the pore pressure ratio reduced; whereas an increase in pore pressure ratio was witnessed with an increase in shear strain. The influence of cement inclusion on the cyclic response of the specimens is evaluated for varying cement contents (1–4%). The addition of 4% cement considerably enhanced the strength of sand and arrested the liquefaction instigation. [ABSTRACT FROM AUTHOR]

This study investigated the role of SiC as a reinforcement on microstructure, corrosion, and electrochemical properties of Cu/xSiC (x = 0, 5, 10, 15, 20, 25, and 30 vol% SiC) composites. The powder metallurgy route was used to fabricate Cu/SiC composite. The distribution of SiC reinforcing particles in the Cu matrix and their interfaces were investigated using optical and SEM/EDS microscopes. The various phases of Cu strengthened with SiC particles were detected using an X-ray diffractometer. The anticorrosion behavior and electrochemical properties of composites were investigated using various electrochemical techniques in 3.5 wt% NaCl solution. The electrochemical studies showed that the inclusion of SiC particles in the Cu matrix improved the resistance to corrosion. It was found that as the reinforcing particles increased to 20 vol%, the corrosion potential increased from − 240 to − 183 mVAg/AgCl, and the corrosion current density decreased from 5.01 to 0.02 µA cm−2, while the passive current density decreased from 17.58 to 4.74 × 10–4 A cm−2. This behavior resulted from the nucleation and production of a good protective layer. On another side, increasing reinforcing particles over 20 vol%, the corrosion current density increased from 0.05 to 0.63 µA cm−2, while the corrosion potential shifted from − 196 to − 206 mVAg/AgCl. [ABSTRACT FROM AUTHOR]

In recent years, there has been a heightened focus on multiplex porosity due to its significant adverse impact on the mechanical properties of aluminum alloy components produced through wire arc additive manufacturing (WAAM). This study investigates the impacts of the process parameters and dimension parameters on the relative densities of WAAM 2219 aluminum alloy components by conducting experiments and investigates the changes in high relative density process windows with different dimension parameters. The findings reveal a hierarchy in the influence of various parameters on the relative density of the 2219 aluminum alloy: travel speed (TS), wire feed speed (WFS), the number of printed layers (L), interlayer cooling time (ICT), and theoretical length of weld (TLW). A series of data for analysis was produced through a designed experiment procedure, and on the basis of this, by integrating the data augmentation method with the eXtreme Gradient Boosting (XGBoost) algorithm, the relationship among the process parameters, dimension parameters, and relative density was modeled. Furthermore, through leveraging the established model, we analyzed the changes in the optimized process window corresponding to a high relative density with the L. The optimal windows of WFS and TS change when the L reaches a certain value. In contrast, the optimal window of ICT remains consistent despite an increase in the L. Finally, the relative density and mechanical properties of the formed 20-layer specimens within the model-derived window were verified. The relative density of the specimens within the window reached 98.77%, the ultimate tensile strength (UTS) reached 279.96 MPa, and the yield strength (YS) reached 132.77 MPa. This work offers valuable insights for exploring the process window and selecting process parameters through a more economical and faster approach in WAAM aluminum components. [ABSTRACT FROM AUTHOR]

The phenomenon of fine particle migration through the voids of the granule skeleton under the seepage force is called suffusion. Relative density, original fine particle content, and gap ratio are thought to play vital roles in the suffusion process. This paper investigates the effect of geometrical characteristics (i.e., original fine particle content, gap ratio, and relative density) on soil structure and mechanical performance (i.e., small strain shear modulus) using the bender element method technique. The small strain shear modulus (G0) is used as a mechanical parameter to evaluate the shear stress transmission of the soil structure along with the erosion process. The comparison between erosion percentage and vertical strain change suggests the alteration in soil fabric after soil erosion. The G0 monitoring results show that packings with a higher original fine particle content have a lower G0 value, whereas the gap ratio and relative density present a positive relationship with G0. [ABSTRACT FROM AUTHOR]

In the present study, the RC pile cap-pile-soil interaction was experimentally investigated by testing twelve half-scale RC pile caps. Two main parameters were considered within the experimental program; the first factor was the relative density of the supporting sandy soil. Four models were tested without being rested on soil, while the other eight models were rested on sandy soil with a relative density of 80% or 90%. The second studied factor was the ratio between the spacing between the RC piles and the width of the pile (S/D), which varied within the range of 2.25, 2.5, 2.75, and 3.0. In comparison to the reference models (without underneath soil), the impacts of the examined parameters on the load-midspan deflection responses, cracking, and ultimate loads were investigated. Additionally, the associated settlements, stiffness, ductility, and energy dissipation capacity were also examined. The findings revealed that all RC pile caps exhibited a punching failure mode accompanied by shear cracks, irrespective of whether they were resting on sandy soil or not. On the contrary, the ultimate load of RC pile caps resting on sandy soil, especially with a higher relative density, was incredibly enhanced with respect to models loaded without supporting soil. The gain in the ultimate load of RC pile caps with S/D ratios of 2.25, 2.5, 2.75, and 3.0 was in the range of 5.4–6.7%, 12–16%, 15–21%, and 24–35%, respectively.

Materials properties are highly dependent on the processing parameters and technique used during sintering. The effect of Spark Plasma sintering process parameters (pressure and temperature) on the hardness and relative density of Ni–20Cr–5ZrO2 composite was investigated. Response Surface Methodology (RSM) from the design of experiment (DOE) technique was successfully employed for the experimental design, and statistical analysis was conducted on the obtained experimental results. The microstructural analysis of the sintered composite showed the presence of solid solution phases of Ni and Cr, which were confirmed by the XRD results as (Cr,Ni) alongside unreacted ZrO2 particles at sintering temperatures of 950 °C and 1000 °C. The validity of the model developed with the impact of each variable and their corresponding interaction on the responses was performed using analysis of variance (ANOVA). The relative density and hardness were the two responses considered. The actual values (experiment data) and expected values (simulated data) were subjected to statistical analysis, to develop a predictive model that synchronizes density and hardness as distinct process parameters, with material hardness and relative density serving as the responses of the specified experiment. For the responses, quantitative models were created, and 10 experimental runs were processed to ascertain the desirability of the responses. The SPS processing parameters considered the most desirable were 1000 °C sintering temperature and 50 MPa pressure. The hardness property obtained under this condition is 433.23 HV with a relative density of 98.15%.

IntroductionJackup rigs are one of the most widely used and popular offshore structures in semi-deep waters due to their mobility. The new jackups usually consist of a floating triangular body supported by three independent vertical truss legs that can be raised, lowered and jacked, and each of these legs rests on foundations known as spuds. They ride and reach stability and balance by penetrating deep into the soil. In cases where the seabed soil has a layered structure including a strong layer placed on top of a weak layer, there is a possibility of punch failure during foundation penetration. Knowing about the soil flow mechanisms around the foundation of the spudcon that suffer continuous large penetration and also estimating the probability and degree of intensity of a sudden spudcon penetration are very important issues.MethodologyIn the present research, a numerical study was carried out to investigate the bearing capacity of the spudken foundation of the offshore jackup structure in soil with a two-layer system of sand on clay. Finite element analysis of large deformations has been used to simulate the continuous penetration of the spudken foundation in a layered soil consisting of a strong sand layer placed on top of a weak clay layer. Numerical simulation is done by "Eulerian-Lagrangian coupling" method in ABAQUS software.In this research, the effect of characteristics of sand and clay layers, including relative density (ID) and thickness of sand layer, shear strength at the boundary of two layers (su0), gradient of shear strength of clay layer on bearing capacity and punch rupture phenomenon are studied. In this research, the Mohr-Columb model was used to model the behavior of sandy and clay soils.Results and discussionThe results of the research show that the parameters related to geotechnical characteristics, including the shear strength of the clay layer, the shear resistance gradient, the relative density of the sand layer, and the thickness of the sand layer have a direct relationship with the bearing strength of the Spadken foundation. So that with the increase of each of these characteristics, the bearing resistance also increases. The obtained results showed that by increasing the thickness (Hs) and relative density (ID) of the sand layer, the load bearing capacity of the pispodken (q) and the volume of the transferred sandy soil mass (the height of the soil mass (hplug) and the width of the soil mass) (bplug) increases, so that with the increase of Hs from 6 m to 8 m, the value of qpeak increases from 263 kPa to 346 kPa, the value of hplug from 6.52 m to 8.26 m and the value of bplug from 6.6 m to 6.9 m and with The increase of ID from 20% to 60% increases the qpeak value from 328 kPa to 367 kPa, the hplug value from 6.85 m to 7.14 m, and the bplug value from 5.7 m to 6 m. Also, the investigation of the effects of shear resistance (su0) and shear resistance gradient (ρ) of the clay layer shows their direct relationship with the bearing capacity and the reverse relationship with the volume of the transferred soil mass, so that with the increase of su0 from 11 kPa to 20 kPa, the value of qpeak from 307 kPa to 390 kPa, the value of hplug from 7.41 m to 7.14 m and the value of bplug from 6.9 m to 6.6 m, and with the increase of ρ from 1 kPa/m to 2 kPa/m, the value of qpeak from 314 kPa At 352 kPa, the value of hplug goes from 7.14 m to 6.9 m and the value of bplug goes from 6 m to 5.7 m.ConclusionsThe results of this research can be summarized as follows:• Parameters related to geotechnical characteristics, including shear resistance of clay layer, gradient of shear resistance, relative density of sand layer, thickness of sand layer have a direct relationship with the load bearing strength of the foundation. So that with the increase of each of these characteristics, the bearing resistance also increases.• The severity and risk of punch breakage increases with the increase in the thickness of the sand layer and the decrease in the shear strength of the clay layer.• The soil rupture pattern under the infiltrating spudken foundation changes with respect to the depth, such that at surface depths, the rupture has two components, shear along the almost vertical shear plane in the sand layer and local shear rupture in the clay layer.

Porous materials are known for their excellent energy absorption capability and, thus, are widely used in anti-impact applications. However, how the pore shape and size impact the failure mechanism and overall behavior of the porous materials under impact loading is still unclear or limitedly touched. Instead of using homogeneous solids for the porous material model, pores with various shapes and sizes were implanted in a solid to establish the porous materials that have true porous structures, which permits exploration of the local failure mechanism. The results revealed that differently shaped holes have two different dominant deformation modes. And due to their different local stress distributions, they enter the plastic phase earlier and, thus, have higher specific energy absorption. Meanwhile, the model changes from hardening to a quasi-zero stiffness model as the hole size increases. The application of this work can be extended into the field of impact resistance.