Static Compression Research Articles

Phase transition behavior of benzene under dynamic compression: A stable precocious phase

The phase transitions of benzene under static and dynamic compression were measured by Raman spectroscopy. Under a static compression of up to 23.90 GPa, benzene underwent two phase transitions at approximately 0.71 GPa and 2.73 GPa, and one chemical transformation above 21.95 GPa. Under dynamic compression, liquid benzene was solidified by rapid compression from approximately 0.36 GPa to 3.81 GPa, 6.68 GPa, 9.96 GPa and 16.68 GPa, step by step within 5 ms. It was discovered that liquid benzene changed from the liquid phase into the coexistence phase of I&II at 3.81 GPa and 6.68 GPa, but then changed into two precocious phases at 9.96 GPa and 16.68 GPa. According to the alteration and evolution of the ν1 ring breathing mode (992 cm−1), rapid compression might hasten the mixed-phase’s structural transformation and make it easier to generate benzene pure phase. Decompression measurements on benzene suggest the precocious pure phase II produced by rapid compression can maintain its stable structure rather than undergo a phase change as the pressure decreases to 2.76 GPa. These phase behaviors may be attributed to the dynamic lattice instability brought on by the faster compression rate as well as the deviation from equilibrium state brought on by the dynamic pressure-induced temperature rise.

Some Unfamiliar Structural Stability Aspects of Unsymmetric Laminated Composite Plates.

It is widely recognized that certain structures, when subjected to static compression, may exhibit a bifurcation point, leading to the potential occurrence of a secondary equilibrium path. Also, there is a tendency of deflection increment without a bifurcation point to occur for imperfect structures. In this paper, some relatively unknown phenomena are investigated. First, it is demonstrated that in some conditions, the linear buckling mode shape may differ from the result of geometrically nonlinear analysis. Second, a mode jumping phenomenon is described as a transition from a secondary equilibrium path to an obscure one as a tertiary equilibrium path or a second bifurcation point. In this regard, some non-square plates with unsymmetric layer arrangements (in the presence of extension-bending coupling) are subjected to a uniaxial in-plane compression. By considering the geometrically linear and nonlinear problems, the bucking modes and post-buckling behaviors, e.g., the out-of-plane displacement of the plate versus the load, are obtained by ANSYS 2023 R1 software. Through a parametric analysis, the possibility of these phenomena is investigated in detail.

Role of gravity magnitude on flowability and powder spreading in the powder bed fusion additive manufacturing process: Towards additive manufacturing in space

Understanding powder spreading under low gravity conditions is essential for optimizing final products using additive manufacturing in space. In this study, we investigated the role of gravity on flowability and spreading mechanisms through combined experimental and discrete element method (DEM) studies. Three powders with different theoretical densities were used to reenact low compressive conditions resembling those in a low-gravity environment. The influence of low compressive conditions on flowability and spreading behavior was examined using the Hall flowmeter, rotating drum, and spreading experiments. In the experimental result, the static flowability was primarily affected by the presence of elongated particles rather than the compressive conditions. The dynamic AoR of TD_4 powder increased compared to that of TD_8 powder, despite the presence of spherical particles with a smooth surface finish. A DEM simulation study was conducted using TD_8 powder to investigate the impact of different gravity levels on dynamic flowability. The DEM studies revealed that the dynamic flowability under rotation was decreased under low gravity owing to the promoted cohesive interactions. The powder spreading experiment was performed using the three powders with different theoretical densities. The in-situ observation with particle image velocimetry analysis revealed that kinetic energy dissipation in the spreading process was accelerated in the TD_8 powder pile, despite its high interparticle friction and cohesive force. The powder spreading simulation was conducted using TD_8 powder to clarify the effect of low gravity on the powder spreading process. In TD_8 powder under 1 G, particle supply was facilitated by a synergistic effect of free-falling and deposited particles. However, increased cohesive interactions under 0.5 G and 0.16 G restricted particle supply via free-falling, consequently reducing the powder bed density by about 2 % and 6.2 %, respectively. These findings prove that the cohesive force predominantly controls dynamic flowability and powder bed quality in the spreading process under low gravity conditions.

Centrifuge modelling of dry granular run-out processes under deflective Coriolis condition

Coriolis effects, encompassing the dilative, compressive, and deflective manifestations, constitute pivotal considerations in the centrifugal modelling of high-speed granular run-out processes. Notably, under the deflective Coriolis condition, the velocity component parallel to the rotational axis exerts no influence on the magnitude of Coriolis acceleration. This circumstance implies a potential mitigation of the Coriolis force's deflective impact. Regrettably, extant investigations predominantly emphasize the dilative and compressive Coriolis effects, largely neglecting the pragmatic import of the deflective Coriolis condition. In pursuit of this gap, a series of discrete element method (DEM) simulations have been conducted to scrutinize the feasibility of centrifugal modelling for dry granular run-out processes under deflective Coriolis conditions. The findings concerning the deflective Coriolis effect reveal a consistent rise in the run-out distance by 2%–16%, a modest increase in bulk flow velocity of under 4%, and a slight elevation in average flow depth by no more than 25%. These alterations display smaller dependence on the specific testing conditions due to the granular flow undergoing dual deflections in opposing directions. This underscores the significance and utility of the deflective Coriolis condition. Notably, the anticipated reduction in error in predicting the final run-out distance is substantial, potentially reaching a 150% improvement compared to predictions made under the dilative and compressive Coriolis conditions. Therefore, the deflective Coriolis condition is advised when the final run-out distance of the granular flow is the main concern. To mitigate the impact of Coriolis acceleration, a greater initial height of the granular column is recommended, with a height/width ratio exceeding 1, as the basal friction of the granular material plays a crucial role in mitigating the deflective Coriolis effect. For more transverse-uniform flow properties, the width of the granular column should be as large as possible.

Comparative Biomechanical Study of Fragment-Specific Plates and Headless Screws for Radial Styloid and Lunate Facet Fixation in Distal Radius Fracture Evaluated in a Synthetic Composite

To evaluate the compressive stiffness (ability to resist compression under an applied load) of fragment-specific plate and headless screw fixation for radial styloid and volar lunate facet fractures in a synthetic composite distal radius. A simulated radial styloid fracture (AO type B1.1) and simulated volar lunate facet fracture (AO type B3.3) were created in synthetic composite distal radii and fixed with a fragment-specific plate (FSP) using a radial styloid or lunate facet plate or with two- or three-headless screws (2HS, 3HS), creating 6 fixation models: B1.1/FSP, B1.1/2HS, B1.1/3HS, B3.3/FSP, B3.3/2HS, and B3.3/3HS. Compressive stiffness of fixation constructs under initial static load, cyclic load, and final static load was investigated. Nonaxial loadings, including shearing and rotation, were not evaluated. Regarding AO type B1.1, the mean stiffness of the B1.1/FSP construct was not significantly different from the intact radius, and the mean stiffness was greatest in the B1.1/3HS and lowest in the B1.1/2HS construct. For AO type B3.3, the mean stiffness of the B3.3/3HS construct was not significantly different from the intact radius, and the mean stiffness of the B3.3/FSP and B3.3/2HS construct was greatest and lowest, respectively. Minimal differences in stiffness between initial and final static loads confirmed that there was no evidence of failure implant under cyclic compressive loads. Fragment-specific plates and two- or three-headless screw fixation maintained mechanical stability through compressive cyclic loading for radial styloid and volar lunate facet fractures. The FSPs and three-headless screws fixations provided superior stiffness over the two-headless screws fixation. There was no articular fracture failure in all fixation constructs with initial static compression, cyclic loading, and final compression. Fragment-specific plates and headless screws can both be considered as adequate fixation for radial styloid and volar lunate facet fractures.

Prediction of axial compressive stresses in ultra-high-performance concrete blocks using non-destructive ultrasonic techniques

The application of ultra-high-performance concrete (UHPC) in civil engineering structures is growing rapidly. On the other hand, previous non-destructive testing (NDT) techniques mainly focused on determining the relationship between the acoustic characteristics and elastic modulus, Poisson's ratio, cracking resistance, and strength. This study presents an experimental approach utilizing ultrasonic techniques to predict the axial compressive stresses in UHPC structures. Both cubic and prismatic UHPC blocks were designed and tested under different compressive axial loading conditions, and their ultrasonic acoustic characteristics were evaluated in detail. Normal strength concrete (NSC) blocks were also included in the investigation for comparison purposes. A detailed account of the tests results is provided, including the relationships between the compressive stresses in UHPC blocks and the typical time- and frequency-domain acoustic parameters. Based on the experimental results, an analytical working stress evaluation method for UHPC components using the ultrasonic acoustic parameters is proposed. It is shown that there is close correlation and high prediction stability between the compressive stress in UHPC blocks and the ultrasonic velocity, which is suggested as the main acoustic parameter for stress detection. The correlation between the acoustic amplitude parameters and concrete compressive stress is also shown to be significant, yet is associated with relatively low prediction stability. Moreover, in comparison with conventional NSC blocks, greater correlation and regularity ratios are observed between the typical acoustic parameters and the axial compressive stress in UHPC specimens. Overall, the analytical models proposed in this study are shown to be in close agreement with the experimental results, and can be used, in conjunction with the ultrasonic NDT techniques, to provide a reliable prediction of the level of compressive stresses in UHPC members.

Controllable stress-adsorbed layers in Ti/TiN/TiAlN coatings: Mechanical performance and micropillar compression

Solid particle erosion often compromises the durability of turbine engine blades, particularly those used in offshore and desert environments. Surface protective coatings have emerged as a promising solution to significantly enhance the erosion resistance of compressor blades. In this study, TiAlN multilayer coatings were deposited onto Ti-6Al-4V substrates using a vacuum arc deposition technique. The article explored the strategic incorporation of TiN-Ti-TiN stress-adsorbed layers (SALs) within TiAlN-based coatings. It also investigated the microscale mechanisms leading to coating failure under conditions of micropillar compression. The findings revealed that the presence of metal/ceramic interfaces significantly improved the adhesion strength, crack resistance, erosion resistance and fracture toughness of the coatings. The multilayer deformation behavior of the coatings was primarily determined by the plastic flow of the softer metal layers. The SALs played a crucial role in reducing the elastic strain energy by generating nanotwins, coherent interfaces, and high-density dislocations during deformation, thereby improving the coatings' plastic deformation capability. Moreover, the implementation of dual-cycle SALs successfully reduced radial crack propagation, facilitating a transition from brittle fracture to a combined brittle-ductile fracture mechanism. This study highlights the critical role of metal/ceramic interfaces and SALs in improving the erosion resistance and co-deformability of TiAlN-based hard coatings.

The Role of Deformation and Microstructure Evolution on Texture Formation of a TA15 Alloy Subjected to Plane Strain Compression.

In this study, the texture formation mechanism of a TA15 titanium alloy under different plane strain compression conditions was investigated by analyzing the slipping, dynamic recrystallization (DRX) and phase transformation behaviors. The results indicated that the basal texture component basically appears under all conditions, since the dominant basal slip makes the C-axis of the α grain rotate to the normal direction (ND, i.e., compression direction), but it has a different degree of deflection. With an increase in deformation amount, temperature or strain rate, {0001} poles first approach the ND and then deviate from it. Such deviation is mainly caused by a change in slip behaviors and phase transformation. At a smaller deformation amount and higher strain rate, inhomogeneous deformation easily causes a basal slip preferentially arising from the grain with a soft orientation, resulting in a weak basal texture component. A greater deformation amount can increase the principal strain ratio, thereby promoting other slip systems to be activated, and a lower temperature can increase the critical shear stress of the basal slip, further causing a dispersive orientation under these conditions. At a higher temperature and a lower strain rate, apparent phase transformation will induce the occurrence of lamellar α whose orientation obeys the Burgers orientation of the β phase, thereby disturbing and weakening the deformation texture. As for DRX, continuous-type (CDRX) is most common under most conditions, whereas CDRX grains have a similar orientation to deformed grains, so DRX has little effect on overall texture. Moreover, the microhardness of samples is basically inversely proportional to the grain size, and it can be significantly improved as lamellar α occurs. In addition, deformed samples with a weaker texture present a higher microhardness due to the smaller Schmidt factors of the activated prism slip at ambient loading.

Mechanical properties and energy evolution mechanism of wheat grain under uniaxial compression

To determine the mechanical properties and energy evolution characteristics of wheat kernels during compression, the mechanical properties and energy evolution of wheat kernels with high-gluten, medium-gluten, and low-gluten were analyzed in uniaxial compression test. Based on the theory of Hertz's formula, the stress-strain laws of the three varieties of wheat kernels in the process of compression damage were investigated; Based on the law of energy conservation, the energy evolution characteristics of the three varieties of wheat kernels under the same compression conditions were analyzed. The results showed that the stress-strain process of wheat kernels with high-gluten, medium-gluten, and low-gluten under compressive stress followed a similar trend overall, with the corresponding minimum failure strengths at the peak being 51.79 MPa, 50.07 MPa, and 46.21 MPa, respectively. The energy evolution patterns of three varieties of wheat kernels under uniaxial compressive loading were approximately the same, indicating that the elastic energy was mainly accumulated before the peak and reached the maximum at the peak. In contrast, the proportion of dissipated energy increases after the peak and rapidly exceeds the elastic energy. In this paper, the damage characteristics of wheat kernels are described from the energy point of view, which is of great significance for the new conceptualization of the evolution of wheat grain damage.

Origami-inspired soft fluidic actuation for minimally invasive large-area electrocorticography

Electrocorticography is an established neural interfacing technique wherein an array of electrodes enables large-area recording from the cortical surface. Electrocorticography is commonly used for seizure mapping however the implantation of large-area electrocorticography arrays is a highly invasive procedure, requiring a craniotomy larger than the implant area to place the device. In this work, flexible thin-film electrode arrays are combined with concepts from soft robotics, to realize a large-area electrocorticography device that can change shape via integrated fluidic actuators. We show that the 32-electrode device can be packaged using origami-inspired folding into a compressed state and implanted through a small burr-hole craniotomy, then expanded on the surface of the brain for large-area cortical coverage. The implantation, expansion, and recording functionality of the device is confirmed in-vitro and in porcine in-vivo models. The integration of shape actuation into neural implants provides a clinically viable pathway to realize large-area neural interfaces via minimally invasive surgical techniques.

Advancements and challenges in strained group-IV-based optoelectronic materials stressed by ion beam treatment

In this perspective article, we discuss the application of ion implantation to manipulate strain (by either neutralizing or inducing compressive or tensile states) in suspended thin films. Emphasizing the pressing need for a high-mobility silicon-compatible transistor or a direct bandgap group-IV semiconductor that is compatible with complementary metal–oxide–semiconductor technology, we underscore the distinctive features of different methods of ion beam-induced alteration of material morphology. The article examines the precautions needed during experimental procedures and data analysis and explores routes for potential scalable adoption by the semiconductor industry. Finally, we briefly discuss how this highly controllable strain-inducing technique can facilitate enhanced manipulation of impurity-based spin quantum bits (qubits).

Prediction on the time-varying behavior of tunnel segment gaskets under compression

The compression force is a critical indicator for assessing the waterproofing capability of ethylene propylene diene monomer (EPDM) rubber gaskets, and the relaxation of EPDM gaskets under compression is a key factor contributing to water leakage in shield tunnels. In this study, detailed accelerated aging tests of gaskets with different precompression openings were conducted. Analytical method and simulation method for predicting the long-term performance of EPDM gaskets considering their different compression states were proposed. First, the compression curve of the gasket was divided into three stages to analyze the mechanism of compression force degradation in depth. Under the action of a compression force, the unrecoverable deformation caused by open holes shortened stage III of the compression curve, which constituted the primary factor influencing gasket compression force relaxation. In addition, the Arrhenius equation was used to establish a conversion relationship between the accelerated aging test conditions and actual service time, and an analytical expression (AE) method for predicting the compression force degradation pattern of gaskets was proposed. Finally, a finite element (FE) method based on the relaxation constitutive model was proposed, enabling simulation of deteriorating tunnel segment gasket performance under complex compression states. Then, the effectiveness and accuracy of the proposed relaxation model were validated by comparing the compression force curves and deformation states obtained from experiments and simulations. Based on the time-varying relaxation constitutive parameters, the variation in the compression force of EPDM gaskets with different joint openings over time was simulated. The results show that the minimum compression force retention rates of gaskets after 100 years of service predicted by the AE method and FE method are 28.5 % and 30.6 %, respectively. This study provides two effective means for predicting the long-term mechanical performance of compressed EPDM gaskets, offering pivotal insights for long-term waterproofing design of shield tunnel joints.

Investigating the damage characteristics of kiwifruits through the integration of compressive load and finite element method

Fruits are susceptible to various forms of mechanical damage after harvesting. Compression-induced bruising is the most common damage incurred, and it crucial to mitigate this for reducing economic losses associated with fruit. This study investigates the impact of compression on kiwifruit. Experiments combined with finite element method simulations were conducted to analyze the relationship between compression distance and bruise volume of kiwifruits under different storage times. This study's results found that compression distance and storage time are linearly positively correlated with the bruise volume of kiwifruit. The difference in bruising volume between simulation results and actual results is less than 14 %. The aforementioned results indicate that our employed compression model is capable of simulating real compression scenarios. This study provides significant theoretical insights into predicting and evaluating potential damages that may occur during post-harvest processing of kiwifruits under compression conditions.

New Design Criteria for Long, Large-Diameter Bored Piles in Near-Shore Interbedded Geomaterials: Insights from Static and Dynamic Test Analysis

This paper presents an analysis of long, large-diameter bored piles’ behavior under static and dynamic load tests for a megaproject located in El Alamein, on the northern shoreline of Egypt. Site investigations depict an abundance of limestone fragments and weak argillaceous limestone interlaid with gravelly, silty sands and silty, gravelly clay layers. These layers are classified as intermediate geomaterials, IGMs, and soil layers. The project consists of high-rise buildings founded on long bored piles of 1200 mm and 800 mm in diameter. Forty-four (44) static and dynamic compression load tests were performed in this study. During the pile testing, it was recognized that the pile load–settlement behavior is very conservative. Settlement did not exceed 1.6% of the pile diameter at twice the design load. This indicates that the available design manual does not provide reasonable parameters for IGM layers. The study was performed to investigate the efficiency of different approaches for determining the design load of bored piles in IGMs. These approaches are statistical, predictions from static pile load tests, numerical, and dynamic wave analysis via a case pile wave analysis program, CAPWAP, a method that calculates friction stresses along the pile shaft. The predicted ultimate capacities range from 5.5 to 10.0 times the pile design capacity. Settlement analysis indicates that the large-diameter pile behaves as a friction pile. The dynamic pile load test results were calibrated relative to the static pile load test. The dynamic load test could be used to validate the pile capacity. Settlement from the dynamic load test has been shown to be about 25% higher than that from the static load test. This can be attributed to the possible development of high pore water pressure in cohesive IGMs. The case study analysis and the parametric study indicate that AASHTO LRFD is conservative in estimating skin friction, tip, and load test resistance factors in IGMs. A new load–settlement response equation for 600 mm to 2000 mm diameter piles and new recommendations for resistance factors φqp, φqs, and φload were proposed to be 0.65, 0.70, and 0.80, respectively.

Hydrogen penetration into the NiTi superelastic alloy investigated in-situ by synchrotron diffraction experiments

Microstructural changes induced by a hydrogen permeation into the NiTi superelastic alloy were investigated in-situ using the X-ray synchrotron diffraction. A new design of an electrochemical cell enabled to uncover time and position dependent processes under a flat alloy surface exposed to the cathodic hydrogen. The diffraction data supported by thermo-elastic FEM calculations helped to quantify an evolution of compressive stresses in the B2 austenitic phase hosting hydrogen atoms. The compressive stress state initiates a formation of martensitic phases starting from the exposed surface layer and advancing into the alloy volume with increasing time of hydrogen charging. We have performed the ab-initio DFT study in order to rationalize volumetric changes associated with variations in the B2 austenite and B19′ martensite lattice parameters. The numerical results also contributed to the identification of a new hydride phase with orthorhombic crystal structure and lattice parameters a = 0.8505 nm, b = 0.7366 nm and c = 0.4722 nm.

Research progress on freeze–thaw constitutive model of concrete based on damage mechanics

Abstract In cold areas, freeze–thaw damage seriously affects the long-term use and safe operation of concrete structures. The constitutive model is an important foundation for predicting deformation and strength characteristics of concrete materials and for the non-linear analysis of concrete structures. This study is based on the elaboration of methods for the constitutive model of damaged materials by using damage mechanics and others. This study focuses on the existing constitutive model results of concrete under the static axial compression load, dynamic load, and coupling environmental load, and analyzing the problems in existing studies. Research has shown that segmented models exhibit higher fitting accuracy of concrete freeze–thaw constitutive model under static axial compression loads. By defining coupled damage variables, it is possible to approach the actual freeze–thaw damage of concrete under environmental coupling, and attention should be paid to the differences or interactions between damage factors. In order to meet the actual engineering needs of high altitude and cold areas needs to expand the temperature range of freeze–thaw tests and consider the dynamic loads impact on concrete damage, the establishment of constitutive model of concrete under the actual freeze–thaw damage is the focus of frost-resistant durability research of hydraulic concrete in cold regions.

Intervertebral disc creep behaviour through viscoelastic models: an in-vitro study

The intervertebral disc (IVD) is a complex biological structure that ensures the spine strength, stability, mobility, and flexibility. This is achieved due to its biphasic nature which is attained by its solid phase (annulus fibrosus) and fluid phases (nucleus pulposus). Hence, the IVD biomechanical response to long-term loads, which is critical as it affects hydration, and nutrients-water transport influencing disc height reduction, has been further explored and mathematically modelled in this paper. An in-vitro study was performed on seven human lumbar spine specimens (L4-5), to assess if the classical rheological models and Nutting's power law can model in a simple way the intermediate characteristics between solid and fluid of the IVD. Creep tests were conducted by applying a static compression load of 500 N for 15 min. A correlation analysis was done (Pearson, p < 0.05) between the model parameters and the maximum value of Disc Height Reduction, followed by a linear regression analysis. In summary, the long-term IVD mechanical behavior was modeled in a simple way, emphasizing that yet there is no mathematical certainty about this mechanical behavior. Hence, a future aim might be to develop intervertebral disc prostheses capable of replicating only the disc mechanical response, without necessarily considering the microscopic-level biological drivers. Therefore, a future goal is to fully understand and model the disc's mechanical response toward the design of new disc prostheses that would consider only the macroscopic aspect, without considering the biological aspects.

A computational model for single cell Lamin-A structural organization after microfluidic compression.

In recent years, nuclear mechanobiology gained a lot of attention for the study of cell responses to external cues like adhesive forces, applied compression, and/or shear-stresses. In details, the Lamin-A protein-as major constituent of the cell nucleus structure-plays a crucial role in the overall nucleus mechanobiological response. However, modeling and analysis of Lamin-A protein organization upon rapid compression conditions in microfluidics are still difficult to be performed. Here, we introduce the possibility to control an applied microfluidic compression on single cells, deforming them up to the nucleus level. In a wide range of stresses (~1-102 kPa) applied on healthy and cancer cells, we report increasing Lamin-A intensities which scale as a power law with the applied compression. Then, an increase up to two times of the nuclear viscosity is measured in healthy cells, due to the modified Lamin-A organization. This is ascribable to the increasing assembly of Lamin-A filament-like branches which increment both in number and elongation (up to branches four-timelonger). Moreover, the solution of a computational model of differential equations is presented as a powerful tool for a single cell prediction of the Lamin-A assembly as a function of the applied compression.

High-pressure phase transition in 3-D printed nanolamellar high-entropy alloy by imaging and simulation insights

We report on the high-resolution imaging and molecular dynamics simulations of a 3D-printed eutectic high-entropy alloy (EHEA) Ni40Co20Fe10Cr10Al18W2 consisting of nanolamellar BCC and FCC phases. The direct lattice imaging of 3D-printed samples shows the Kurdjumov–Sachs (K–S) orientation relation {111} FCC parallel to {110} BCC planes in the dual-phase lamellae. Unlike traditional iron and steels, this alloy shows an irreversible BCC-to-FCC phase transformation under high pressures. The nanolamellar morphology is maintained after pressure cycling to 30 GPa, and nano-diffraction studies show both layers to be in the FCC phase. The chemical compositions of the dual-phase lamellae after pressure recovery remain unchanged, suggesting a diffusion-less BCC–FCC transformation in this EHEA. The lattice imaging of the pressure-recovered sample does not show any specific orientation relation between the two resulting FCC phases, indicating that many grain orientations are produced during the BCC–FCC phase transformation. Molecular dynamics simulations on phase transformation in a nanolamellar BCC/FCC in K–S orientation show that phase transformation from BCC to FCC is completed under high pressures, and the FCC phase is retained on decompression aided by the stable interfaces. Our work elucidates the irreversible phase transformation under static compression, providing an understanding of the orientation relationships in 3-D printed EHEA under high pressures.

A random elastoplastic framework of relationships between CBR and Young’s modulus for coarse-grained soils

The material quality indicator most commonly used for the quality of road materials is the California Bearing Ratio test (CBR). In addition, the CBR test provides a value commonly used to correlate with the resilient modulus (used in the design and analysis of pavement) due to its cost-effectiveness. This test measures soil resistance to penetration by a punch and compares it with the pressure measured in a standard material at the same penetration (2.5 mm or 5 mm). However, this test lacks physical explanations regarding mechanical behavior because the CBR value only compares soil penetration resistance with the pressure measured in a standard material. Another issue arises from the scattered results obtained from both equations and tests, highlighting the need for variability analysis of the CBR test to assess the effect of the different geotechnical variables on the CBR value. For this purpose, simulations using FEM (Finite Element Method) considering random soil parameters were performed for the CBR test. These FEMs included a linear elastic model and two failure criteria (Mohr–Coulomb and Drucker-Prager with a cap) and were prepared for granular soils. The evaluation shows that the increase or decrease in the CBR value is a function of the elastic modulus, yield stress, and friction angle. Moreover, the simulations expand the knowledge of the shearing mechanisms, generated stresses, displacement fields, and load sharing when the CBR test is made. From these results, a physical explanation of test results can be done. FEM simulations showed stress zones in conditions of elastic, compression, and shear behavior. These zones can explain the importance of elastic modulus, yielding stress, and friction angle in the CBR value. From numerical results, a new equation was proposed and compared with practical equations proposed by international standards and other sources to estimate the probability of underestimated values CBR according to the correlations used.