Dilatant Behavior Research Articles

Study of phosphoric acid slurry rheological behavior in the attack reactor and development of a model to control its viscosity using artificial intelligence

This work aims to determine the rheological properties of the industrial phosphoric acid slurry and its behavior under the operating conditions of the phosphoric acid production process. For that, several experimental tests on the slurry were carried out, using a Rheometer (Anton Paar), which testing the effect of temperature and solid content. The results show that, for a fixed solids rate, the viscosity of the slurry decreases with temperatures from 75°C to 82°C and increases for temperatures above 82°C considered as the maximum temperature required by the process. This phenomenon is due to the morphological change of the gypsum which corresponds to the range of calcium sulfate hemihydrate formation. For a fixed temperature, the viscosity increases with increasing slurry solid content (31% to 37%). The viscosity increases with the shear gradient. Increasing the solid charge in the slurry increases its resistance to flow and movement. Thus, the slurry has a higher tendency to settle. A comparative study of four rheological models, Casson, Bingham, Ostwald and Herschel-Buckley, led to the selection of the Herschel-Bulkley model. This predicts the behavior of the phosphate slurry with a correlation coefficient of 99.9% and a MAE less than 4%. Overall, the results show that the threshold flow of the slurry is negligible, and its behavior is nonlinear. Thus, the slurry is a non-Newtonian fluid, with a dilatant rheological behavior. The various tests carried out enabled us to measure the viscosity of the phosphoric acid suspension for different solids contents and at different temperatures. The results obtained enabled us to study the rheological behavior and develop an artificial neural network model to control the viscosity of the slurry at the phosphoric acid attack tank.

Evaluating the Accuracy of Bonded Block Models for Prediction of Rockmass Analog Mechanical Behavior.

Large-scale rock formations, referred to as "rockmasses", consist of intact rock separated by pre-existing discontinuities (i.e., joints). The mechanical behavior of rockmasses is difficult to directly test in the laboratory due to the required specimen scale. Instead, Synthetic Rockmass Modeling (SRM) is often used to simulate field-scale rockmass behavior. SRM requires a calibrated discrete element model (DEM) of intact rock combined with a Discrete Fracture Network (DFN). While the SRM concept has been informally determined to provide reasonable results based on practitioner experience, detailed and peer-reviewed validation is lacking. The goal of this study was to evaluate the predictive capabilities of the SRM method. Previously available data on intact and rockmass analog laboratory specimens of Blanco Mera granite containing DFNs with two joint sets were used as a basis for the SRM created in this study. Specifically, the intact DEM was a Bonded Block Model (BBM), generated to match the grain structure and composition of Blanco Mera granite and the model's input parameters were calibrated so that the behavior of the BBM matched that of the intact laboratory specimens. The predictive capabilities of the model were evaluated by recreating the DFN from the jointed laboratory specimens within the intact BBM and comparing the behavior of the jointed models back to the jointed laboratory specimens, which has not been previously studied in the literature. The BBM was found capable of approximately predicting the behavior of rockmass analog specimens containing a pre-existing DFN without further calibration, which shows potential for the use of SRM in both industry and academia. Specifically, the BBM predicted the strength, dilatancy, and microfracturing behavior of the jointed laboratory specimens.

Stabilized Positive Electrode Material to Enable High Energy/Power Density Lithium-Ion Batteries

Recently, the large-scale deployment of electric vehicles (EVs) and stationary battery systems has putforward urgent requests for rechargeable batteries with higher energy/power density and longerlifespans. As such, next-generation Li-ion batteries (LiBs) are expected to meet these requirements. Thepossibility of using Ni-rich high-capacity cathode materials (NMC) can help to achieve that goal, however,they still suffer from significant capacity fade via several chemical and mechanical degradation modes.One is crack formation within secondary particles which leads to parasitic reactions that evolve oxygenand potentially initiate the formation of inactive crystal structures. LiBs mechanical and chemicaldegradation mechanisms can be extended by applying protective coatings to the cathode’s surface. Manystudies explore atomic layer deposition (ALD) for this purpose. However, the complementary molecularlayer deposition (MLD) technique might offer the benefit of depositing flexible hybrid coatings that canaccommodate potential volume changes of the electrode during the battery cycling. This study reportsthe deposition of novel organic-inorganic films via the ALD-MLD method. Characterization analysis suchas FTIR, XPS, SEM-EDS, and TEM confirmed the film deposition on the surface of the NMC electrode.Besides, the electrochemical results showed the enhancement of the coated electrode, as evidenced byproviding a longer life with a 93% capacity retention after 150 cycles (3.0-4.4 V vs. Li/Li+), while theuncoated one retained only 83% of its initial capacity. Moreover, in situ dilatometry showed irreversiblevolume change for uncoated NMC while it was mostly reversible for coated ones during the cycling. Itrevealed the dilation behavior of the electrode, resulting in crack formation, which is significantlysuppressed for the coated samples. Stable cycling of Ni-rich cathode materials in crucial conditions suchas high voltage windows and elevated temperatures is still extremely challenging. To evaluate this, in situdilatometry was performed at elevated temperatures (40 °C and 55 °C) and higher voltage ranges (3.0-4.6V). The results confirmed that in both conditions, the dilation behavior of the coated sample is still undercontrol while the capacity is comparable to the uncoated sample. This revealed that the coatings presentgood lithium-ion kinetics and reduce electrolyte decomposition. Overall, this work showed the liability ofthe ALD-MLD films deposited on NMC electrodes to mitigate the degradation mechanisms and providesinsight into a method that seems promising as a protective and elastic coating for future high-energylithium-ion battery cathodes. Figure 1

Effect of dilatancy on tension response of completely rough piles embedded in granular soils

Pile surface roughness is an important characteristic determining the displacement response of piles under various loading conditions since it leads to surface friction resistance. Considering that no capacity contribution is acquired from the pile tip, the effect of surface friction becomes more pronounced for tension piles. Pile surfaces can be classified as smooth, rough, or completely rough according to the normalized surface roughness value (Rn) of piles, and this paper focuses only on the uplift capacity of piles with normalized surface roughness values greater than 0.1 (i.e., completely rough) by employing the PLAXIS3D code verified against results of twelve physical modelling tests reported in the literature. The reason of selecting piles with completely rough surfaces in this study is that dilatancy behaviour can be only observed in the uplift load-displacement relationships of such piles, unlike the piles with smooth or rough surfaces. While numerical simulations are repeated for different normalized surface roughness values (Rn = 0.2, 0.5, 1.0, and 2.0) and different relative densities of sandy backfill (Dr = 25%, 50%, and 75%), the effect of the pile surface friction resistance on the uplift capacity, which occurs as a result of the interaction between the pile surface and sandy soil grains, is studied with special emphasis on soil dilatancy. It is observed that the numerical results are quite compatible with the physical test results. In addition, increasing the pile surface roughness and relative density of sandy soil causes an increase in the uplift capacity, and those capacity increments can only be modelled properly by increasing the dilatancy angle of sandy soil in finite element analyses.

Micromechanical investigation of the effect of an imposed stress state change during drained cyclic loading using DEM

This study investigates the effect of a stress state change at an intermediate stage during cyclic loading on the drained cyclic deformation of soil using Discrete Element Method (DEM) simulations. Drained cyclic triaxial simulations were conducted on an assembly of irregularly shaped particles, with the stress state shifting along different stress paths at an intermediate stage of cyclic loading. The analysis of the macro- and microscopic responses reveals a link between the cyclic stress–dilatancy behaviour and the anisotropy of the granular assembly. In the simulations without the stress state change or with a stress ratio increase, the strain accumulation direction aligns with the prediction of the Modified Cam Clay (MCC) flow rule; and the strain accumulation is faster at higher stress ratios when the contact distribution is more anisotropic. However, when the particle assembly experiences a stress ratio decrease during cyclic loading, the subsequent strain accumulation direction deviates from the MCC flow rule, and strains accumulate more rapidly at lower stress ratios when the contact distribution is nearly isotropic. A tentative explanation is proposed to explain the altered strain accumulation direction after the stress ratio decrease.

Effect of Grain Size Distribution on Shear Strength Characteristic of Random Fill Material at Keureuto Dam, Indonesia

Earth-fill dams are commonly constructed by composing different geomaterials to optimally utilize local natural resources. In Indonesia, random fill materials are frequently used as a major composition in dam construction. The term random fill material originated from its broad range of grain size. Grain size distribution influences shear strength characteristics of geomaterials. There are 2 shear strength equations to model the behavior of fill material, i.e., linear Mohr-Coulomb and non-linear power curve. Two series of large scale in situ direct shear tests were performed at Keureuto Dam, Indonesia. Sieve analysis tests were performed accordingly. The random fill material was composed of cobbles, gravel, and less than 25% of sand. The stress-displacement characteristics of random fill material indicated that plastic deformation occurred at shear strain of 1% to 4%. The shear failure was reached in shear displacements of 60 – 90 mm, equivalent to shear strain of 8% – 12 %. Stress-strain relationships showed a dilative behavior indicating the random fill was in a relatively dense form. The dilatancy tends to decrease as the normal stress increases. The linear Mohr-Coulomb failure criteria and non-linear power curve equation are suggested to characterize the shear strength of the random fill material. To obtain a realistic value of the non-cohesive strength parameter of granular material, the Mohr-Coulomb approach should be intercepted at zero. A relationship between secant friction angles for different normal stresses is presented. This angle tends to decrease at higher normal stresses.

The effect of particle breakage on the dilatancy and shear behavior of marine calcareous and siliceous deposits

A large part of ocean surface is covered by calcareous deposits. The Low stiffness and weak particles of calcareous soils deposited by marine organisms showed significant particle breakage under applied loads, which resulted in different behavior compared to terrigenous soils. A series of compression drained triaxial tests were carried out to evaluate the monotonic shear behavior of crushable and non-crushable soils. Three different soils, including Firoozkuh siliceous sand (as a non-crushable soil) and Hormuz and Bushehr calcareous sands (as crushable soils) which were different in mineralogy compositions were obtained from northern and southern Iran. The specimens were prepared in different relative densities (i.e., loose, medium and dense conditions) and consolidated under confining pressures ranging from 100 to 600 kPa. The monotonic shear and dilatancy behaviors of the soils have been presented in detail and the effect of particle breakage has been discussed. The results showed that particle breakage has a significant effect on the mobilized friction and dilatancy angles of marine crushable soils. There is a linear relationship between the amount of particle breakage occurring during a triaxial test and breakage angle. In addition, the mineralogical difference influences the breakage properties of calcareous deposits.

Use of recycled ceramic beads to enhance mechanical behavior of low-plastic clays

Due to the huge amount of annual non-renewable ceramic waste disposal, it is in favor of eco-system to reuse the ceramic waste in earthwork structures. Thus, among several different applications of ceramic components, they can also be used to replace aggregates in the core of embankment dams, waste disposal projects and to form subgrade of roads and railways. The main issues addressed in this study are the effect of the volumetric content and size of the ceramic inclusions on the mechanical properties of ceramic-clay mixtures. Using an experimental approach, strain-controlled monotonic, stress-controlled cyclic, and post-cyclic monotonic triaxial undrained tests were made. The innovation of this study is that sphere beads of ceramic with different diameters were added to low-plastic clay to explore the role of bead size on the mechanical properties of bead and clay mixtures under monotonic, cyclic and post-cyclic loadings. Thus, we tested four types of specimens consisting of merely pure clay, 80% clay–20% bead, 60% clay–40% bead, and 40% clay–60% bead. Scanning electron microscope (SEM) images were additionally used to investigate the fabric of the clay between the ceramic beads. Test results revealed, firstly, that effective friction angle and undrained shear strength increase with the bead content. Secondly, dilative behavior was captured in all the bead and clay mixtures. Further, both dynamic shear modulus and damping ratio increase with the bead content. Similarly, post-cyclic shear strength increases with the bead content. Finally, different bead diameters did not change the observed trend.

Stress-strain models for FRP-confined thermally damaged concrete

Fiber-reinforced polymer (FRP) jackets have been increasingly used for the strengthening and confinement of concrete columns. Despite extensive research efforts yielding various concrete confinement models that can be broadly classified as design- and analysis-oriented, an accurate model is lacking for the design of FRP-strengthened thermally damaged concrete columns. This paper presents a comprehensive review of existing experimental studies on FRP-confined thermally damaged concrete columns and collects a large database of the corresponding test results. Then, a theoretical analysis is conducted to evaluate the accuracy and reliability of typical concrete confinement models (originally proposed for undamaged concrete) through extensive comparisons with the corresponding test data. The analytical findings have revealed that none of the existing models can accurately predict the compressive behavior of FRP-confined thermally damaged concrete. Two novel confinement models, design-oriented and analysis-oriented, are proposed for FRP-confined thermally damaged concrete. These novel models have appropriately considered the effects of high-temperature exposure on the confining pressure of FRP jackets and the lateral deformation characteristics of thermally damaged concrete. The proposed models are then validated by comparing the model predictions with the corresponding test results, indicating that these models can accurately predict the compressive stress-strain responses and dilation behavior of FRP-confined thermally damaged concrete.

Dilation Characteristics of 3D PBF-LB/M AlSi10Mg Alloy

Application deployment of 3D-printed products represents a progressive area of industrial use of specific metal alloys. In parallel with starting points based on mechanical characteristics in the static and cyclic areas, dilation behavior is an important parameter. A typical application is, for example, components in the aerospace sector, where the components are exposed for a short period to a significant temperature difference in both positive and negative values. Current industrial trends lead to the deployment of additive technologies for producing aircraft system components and instrument parts. Testing of AlSi10Mg alloy samples prepared by direct metal laser sintering, in the past DMLS, now according to the standard laser powder bed fusion (PBF-LB/M) method, is carried out by measuring dilation during a controlled temperature course. The AlSi10Mg alloy is used for mechanically less stressed components, from which a high accuracy of functional dimensions is usually required, which can be affected by dilation characteristics in a wide temperature range. Additively produced components have different dilation characteristics within an identical alloy, often dependent on the production method and orientation during 3D printing. The article presents the testing results and subsequent application characteristics of an additively produced aluminum alloy, considering dilation characteristics.

Suffusion in densely compacted Satozuka pumice sand and its impact on static loading undrained shear strength and dilation behaviour

Pumice sand of volcanic origin contains a high fraction of non-plastic fines (>40 % for Satozuka pumice sand in Sapporo, Japan). Suffusion in such soil can wash away a portion of the fine particles and alter the soil microstructure. The moisture content and degree of compaction can affect the suffusion characteristics of soil deposits, however their effect has not yet been evaluated. Future construction sites in growing Sapporo City, consisting of pumice sand, will require a high degree of compaction (over 90 % and preferably over 95 %) as this sand is prone to suffusion in spite of its dense state. The aim of this study is to assess the impact of suffusion on densely compacted pumice sand with a high proportion of fines, based on its mechanical properties, with an emphasis on shear strength and dilatancy. Firstly, the suffusion characteristics of Satozuka pumice sand were evaluated. Subsequently, undrained triaxial tests (CU¯ tests) under monotonic loading were conducted on high-density specimens, with suffusion and without suffusion, to study the impact of suffusion. It is seen in the results that the hydraulic conductivity, shear strength, stress paths, and dilatancy are all noticeably affected by suffusion. The specimens with suffusion exhibit an increase in residual shear strength and maximum deviator stress under shearing and experience an earlier occurrence of phase transformation from contraction to dilation during shearing. This tendency implies that suffusion has no significant negative impact on the deterioration of earth fill made from pumice sand and non-plastic fines, and that it persists at degrees of compaction between 80 % and 100 %.

Mechanism of balloon burst during transcatheter aortic valve replacement pre-dilatation: Image observation and validation by finite element analysis

BackgroundBalloon burst during transcatheter aortic valve replacement (TAVR) is serious complication. This study pioneers a novel approach by combining image observation and computer simulation validation to unravel the mechanism of balloon burst in a patient with bicuspid aortic valve (BAV) stenosis. MethodA new computational model for balloon pre-dilatation was developed by incorporating the element failure criteria according to the Law of Laplace. The effects of calcification and aortic tissue material parameters, friction coefficients, balloon types and aortic anatomy classification were performed to validate and compare the expansion behavior and rupture mode of actual balloon. ResultsBalloon burst was dissected into three distinct stages based on observable morphological changes. The mechanism leading to the complete transverse burst of the non-compliant balloon initiated at the folding edges, where contacted with heavily calcified masses at the right coronary sinus, resulting in high maximum principal stress. Local sharp spiked calcifications facilitated rapid crack propagation. The elastic moduli of calcification significantly influenced balloon expansion behavior and crack morphology. The simulation case of the calcific elastic modulus was set at 12.6 MPa could closely mirror clinical appearance of expansion behavior and crack pattern. Furthermore, the case of semi-compliant balloons introduced an alternative rupture mechanism as pinhole rupture, driven by local sharp spiked calcifications. ConclusionsThe computational model of virtual balloons could effectively simulate balloon dilation behavior and burst mode during TAVR pre-dilation. Further research with a larger cohort is needed to investigate the balloon morphology during pre-dilation by using this method to guide prosthesis sizing for potential favorable outcomes.

A hardening load transfer function for rock bolts and its calibration using distributed fiber optic sensing

Confinement of rock bolts by the surrounding rock formation has long been recognized as a positive contributor to the pull-out behavior, yet only a few experimental works and analytical models have been reported, most of which are based on the global rock bolt response evaluated in pull-out tests. This paper presents a laboratory experimental setup aiming to capture the rock formation effect, while using distributed fiber optic sensing to quantify the effect of the confinement and the reinforcement pull-out behavior on a more local level. It is shown that the behavior along the sample itself varies, with certain points exhibiting stress drops with crack formation. Some edge effects related to the kinematic freedom of the grout to dilate are also observed. Regardless, it was found that the mid-level response is quite similar to the average response along the sample. The ability to characterize the variation of the response along the sample is one of the many advantages high-resolution fiber optic sensing allows in such investigations. The paper also offers a plasticity-based hardening load transfer function, representing a "slice" of the anchor. The paper describes in detail the development of the model and the calibration/determination of its parameters. The suggested model captures well the coupled behavior in which the pull-out process leads to an increase in the confining stress due to dilative behavior.

Stiffness-based stress–strain model of FRP-confined high-strength and ultra-high strength concrete column with various corner radii

This study introduces a unified design-oriented stress–strain model tailored for fiber-reinforced polymer (FRP)-confined high-strength concrete (HSC) with diverse cross-sectional shapes. The proposed stress–strain model incorporates more suitable mathematical forms, incorporating post-peak axial stiffnesses as crucial parameters, thereby enabling the model to accurately capture the three types of post-peak stress–strain behavior observed in FRP-confined HSC: strain-hardening, strain softening, and strain softening recovering to strain hardening. This variation in post-peak axial stiffness arises due to insufficient FRP confinement at the initial peak strength point, as well as changes in the confinement stiffness ratio stemming from the altered dilation behavior of FRP-confined HSC during the post-peak stage. To address the nonuniform effects of FRP confinement, the concept of effective confinement rigidity was defined, unifying the behavior of FRP-confined circular and square HSC. Additionally, the model incorporates the ultimate condition and the characteristic point on the post-peak branch, representing the change in FRP confinement stiffness, to establish the stress–strain model for FRP-confined HSC. The model parameters were evaluated using available experimental results, and the stress–strain curves derived from the proposed model were compared with existing models in the literature, revealing the proposed model's accuracy and rationality.

Poisson’s ratio of granular materials for Mohr-Coulomb elastoplastic model

ABSTRACT The Mohr-Coulomb elastoplastic model is extensively employed in geotechnical engineering. Despite the well-known nonlinear behaviour of granular cohesionless materials under a wide range of normal stress or confining pressure, the Mohr-Coulomb elastoplastic model continues to be largely used in geotechnical engineering, due to its simplicity and large availability in numerous commercialised software. Its application requires the input of a key parameter, named Poisson’s ratio. It is however a big challenge as its value changes with axial strain and confining pressure. In this study, the optimal Poisson’s ratio of granular materials for the Mohr-Coulomb elastoplastic model is determined by reproducing the experimental results of stress-strain relationships through numerical modelling with the Mohr-Coulomb elastoplastic model. The results show that the Poisson’s ratio μ 0.02, corresponding to the slope of the volumetric strain against axial strain curve at 2% of the peak deviatoric stress can be used in numerical modelling with the Mohr-Coulomb elastoplastic model as long as the granular material does not exhibit dilation behaviour. When the material exhibits dilation behaviour, the Poisson’s ratio μ 0.36, corresponding to the slope of the volumetric strain against axial strain curve at 36% of the peak deviatoric stress, seems to be appropriate in numerical modelling with the Mohr-Coulomb elastoplastic model. In addition, the study also shows that the Mohr-Coulomb elastoplastic model can be used to simulate mechanical behaviour of granular material under small strain, but not appropriate under large strain conditions.

Breath-like interlayer bonding facilitates efficient metal-ion storage in bilayer borophene with decreased adherence capabilities on Ag substrate

The fabrication of bilayer borophene presents an alternative approach to tackle the challenges related to thermodynamic stability and the detachment of monolayer borophene from the metal substrate, which currently restrict its practical application. However, recent theoretical investigations have revealed that the structural arrangement of the most energetic free-standing bilayer borophene, denoted as BL-α+ borophene, is different from the configuration observed experimentally (Nat. Mater. 2022, 21, 35–40). Herein, the effects of introducing an additional stratum of borophene on the electronic properties, mechanical performance, adherence capabilities towards Ag (111), and electrochemical performance as an anode material for alkali-ions batteries has been thoroughly examined. The results demonstrate that free-standing BL-α+ borophene manifests a reduced energy adhesion (Eadh) of −0.059 eV Å−2 when contrasted with its monolayer counterpart. Furthermore, the interlayer B-B bonding exhibits a breath-like dilatation and contraction behavior during metal-ion adsorption/desorption, leading to remarkable theoretical capacities of 1351.6 mAh/g for Li-ion anodes, 1351.6 mAh/g for Na-ion anodes, and 450.53 mAh/g for K-ion anodes, accompanied by moderate diffusion barriers of 0.58 eV, 0.34 eV, and 0.23 eV for Li, Na, and K ions, respectively. These results provide valuable insights into the application of borophene-based electrode materials that exhibit improved stability through a “self-stacking” mechanism.

Characterization of sacha inchi (Plukenetia volubilis) and taro (Colocasia esculenta) flours with potential application in the preparation of both gluten-free and high protein foods.

Background: Interest in alternative sources of tubers and legumes has increased in recent years because of the constant search for raw materials that provide bioactive compounds with antioxidant potential benefits for consumers. The functionality of new raw materials is sought through physical and/or chemical modifications to develop and innovate new foods. The objective of this study was to characterize taro (TF) (Colocasia esculenta) and sacha inchi (Plukenetia volubilis) flours, obtained by the wet (SIF-WM) and defatted method (SIF-DM), as an alternative for the formulation of new functional foods. Methods: The free polyphenols of the different mixtures were analyzed, and the antioxidant properties of the extracts obtained were measured using ABTS.* (2,2′-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid). The ABTS radical method, which reacts with the phenolic compounds of the food matrix, using Trolox as a standard. The blends were subjected to pasting analysis, flow profile tests, determination of viscoelastic properties (temperature sweep). Characterization of common microorganisms in these foods was performed. Results: The highest protein value was obtained in the sacha inchi flour obtained by the defatted method (72.62). The majority of components in taro were carbohydrates (85.4%). About antioxidant and determination of free polyphenols, taro flour obtained values of 2.71 µmol ET/g and 7.47 mg EAG/g, higher than Sacha inchi flours. In the rheological analysis (pasting properties, flow profile, and viscoelasticity), we observed that adding taro flour in different mixtures increases the viscosity peak and a lower breakdown, while there was an increase in setback. Except for defatted sacha flour, the others presented a flow index >1 before heating, showing a dilatant fluid behavior. The presence of Taro flour improves gel formation and stability. Staphylococcus aureus and Salmonella were present in the taro flour. Conclusions: The flours analyzed represent a raw material with great potential for the development of gluten-free foods with functional properties.

Thermal and mechanical properties of an Al-Mg-Sc-Zr high strength alloy fabricated by selective laser melting

Thermal management is one of the most promising applications of Al parts fabricated by additive manufacturing, primarily due to the drastically expanded design space enabled by the latter. The thermal properties of additively manufactured Al alloys are crucial for this application but remain poorly understood. The present study focuses on a high-strength Al-Mg-Sc-Zr alloy fabricated by Selective Laser Melting (SLM). The microstructure of the alloy is characterized by optical and electron microscopy, hardness and tensile testing are conducted, and the thermal conductivity and thermal dilatation behavior are tested. The fabricated samples exhibit strong age hardenability and yield strengths reaching ∼460 MPa. The thermal conductivity in the as-built condition is found to be rather low mainly because of the high solute concentration in the Al matrix as well as the fine grain size, and is improved by 33% after 10 h aging due to precipitation of particles. Meanwhile, abnormal non-linear thermal dilatation behavior is observed in the samples above 400 °C, probably related to the expansion of pores. Lastly, orientation dependency with respect to the building direction is found in both thermal conductivity and dilatation, which is associated with the grain alignment and melt pool structures. The above results provide critical knowledge to the process design toward co-optimization of mechanical and thermal properties of Al alloys fabricated by SLM.

Thermodilatometry of Quartz Porcelain Mixture Under Tensile Loading

Specimens composed of 50 wt.% kaolin, 25 wt.% quartz, and 25 wt.% feldspar were subjected to constant tensile stress during linear heating at 5 °C/min rate to measure their tensile deformation behavior. Deformation occurs at temperatures above 300 °C and depends on the tensile stress: higher external tensile stresses led to a more pronounced expansion of the sample during the dehydroxylation region. Consequently, at temperatures above 1100 °C, sintering of the samples in the liquid state and intense contraction occurred. The dilatation behaviour of the samples was governed by the combined effect of opposing forces. One of these forces originated from external loading and caused the elongation of the specimen. The other force resulted from surface tension, which resulted in the shortening of the specimen. At temperatures above 1100 °C, a distinct V-shaped minimum appeared on the dilatometric plot, indicating a balance between these forces. As the temperature increased, the viscosity of the glassy phase decreased, weakening the surface forces. Eventually, the external force prevailed, causing further elongation of the samples.

Crushing and mechanical characteristics of coral sands under various stress paths

Coral sand is known to have stress path dependence and fragility. In this research, a series of drained triaxial tests were conducted to explore stress path effects on the mechanical and particle breakage characteristics of coral sands. Several mechanical characteristics, such as critical state, strength, and dilatancy characteristics were studied. The results revealed that the dilatancy behaviors, stress-strain responses, and crushing of coral sands were strongly affected by consolidation stress and stress path. The critical state lines of coral sands were straight in p‘-q space and e-(p‘/P a)0.44 plane regardless of stress path. Based on these characteristics, a dilatancy equation was derived and validated through test results. The developed dilatancy equation could predict the dilatancy relationships of coral sands under various stress paths.