Effect Of Loading Rate Research Articles

Analytical models for consolidation of unsaturated composite foundation improved by impermeable columns and PVDs

In this study, two equal-strain consolidation models centred on an impermeable column and a prefabricated vertical drain (PVD), respectively, are developed for the study of unsaturated composite foundations reinforced by impermeable columns and PVDs. The analytical solutions, accounting for the smear effect, well resistance, and time-dependent loading, are obtained through the application of the constant of variation method, Fourier series expansion, and decoupling technique. The validity of the proposed solutions for both distribution modes is then verified by comparing it with the analytical solution for the consolidation of PVD-improved composite foundations. Finally, the analyses are conducted to examine the effects of loading rate, smear parameter, well resistance factor, and distribution pattern on consolidation behaviors during multi-stage loading. Notably, it is observed that the consolidation completion time is unaffected by the loading rate, instead relying on the magnitude of the loading values. The presence of multiple smear zones, resulting from the installation of impermeable columns and PVDs, amplifies the smear effect on consolidation. Additionally, increasing the number of PVDs is found to have a notable effect on accelerating the consolidation rate; however, it is crucial to consider the accompanying increase in well resistance.

Cyclic degradation mechanisms of Al0.3CoCrFeNi high-entropy alloy under different loading rates

The effect of loading rate on the cyclic degradation behavior of Al0.3CoCrFeNi high-entropy alloy (HEA) was investigated through nanoindentation experiments and molecular dynamics simulations. The evolution of mechanical properties and microstructure characteristics under different loading rates, as well as the mechanisms of cyclic degradation, were revealed. It is found that the increase of the loading rate induces higher hardness and smaller nanoindentation depth of the Al0.3CoCrFeNi HEA, which gradually increases with the cyclic loading of nanoindentation, resulting in a larger difference in characteristic nanoindentation depth among different loading rates. What’s more, a larger loading rate is inclined for nanoindentation depth to reach a steady state. Slip lines and pile-ups are formed around the nanoindentation region at higher loading rates indicating the occurrence of a more localized plastic deformation, while an amorphous transformation occurs at different loading rates after cyclic nanoindentation. Cyclic loading results in the gradual accumulation of residual stress, nanoindentation depth and amorphous structures within the material, and a localized plastic deformation. In summary, cyclic degradation of the Al0.3CoCrFeNi HEA is featured by cyclic softening due to dislocation slipping and the accumulation of amorphous phases.

Low-medium loading rate effect on dynamic fracture toughness of sandstone scaled model

To investigate the effects of loading rate on the dynamic fracture toughness of rock in a scaled system, a multi-scale experimental and numerical study is carried out with a single cleavage semi-circle (SCSC) specimen based on a new scaled modeling method. The loading curves of the scaled models are obtained by using the data recorded by an oscilloscope. The fracture time is monitored by the fracture propagation gauge (FPG) to calculate the propagation velocity of fracture. The dynamic fracture toughness of the propagation fracture can be obtained by combining experimental data with a finite-element method. The results show that the effects of loading amplitudes and model size on fracture toughness can be significantly eliminated by the scaled modeling method applied in this paper, which provides a prerequisite for a thorough analysis of the loading rate effect on scaled models. Furtherly, by introducing a new proportional coefficient factor, the scaled modeling method is confirmed to predict the dynamic fracture toughness effectively. The dynamic fracture toughness exhibits a non-linear increase with loading rate in both the fracture initiation and propagation stages. This increase is characterized by a rapid-growth in some middle range of loading rates, with a relatively slow-growth below or above that range. Furthermore, the propagation toughness is greatly affected by loading rate at low rates, whereas the initiation toughness is more significantly influenced by medium loading rates.

In-situ monitoring of crack growth and fracture behavior in composite laminates using embedded sensors of rGO coated fabrics and GnP paper

Graphene-based nanomaterials have found significant interest in the development of embedded sensors to monitor the fracture behavior in composite structures. In this work, in-situ crack propagation and fracture behavior within a glass fiber reinforced polymer composite (GFRP) was monitored using embedded reduced graphene oxide (rGO) coated fabrics and highly conductive graphene nanoplatelet (GnP) paper. All laminates were fabricated using the resin infusion process. The piezoresistive performance of both types of laminates was evaluated using in-plane and out-of-plane mechanical tests. The effect of GnP paper thickness (50/150/240 µm) and loading rate was also evaluated using tensile and Mode-I fracture loadings. Piezoresistivity of the sensors was reduced by increasing loading rate during tensile tests. All laminates with GnP paper exhibited poor mechanical performance under tensile loading. The laminates with 50 µm GnP paper showed highest sensitivity under Mode-I loading. In comparison to pristine laminates, the interlaminar fracture toughness of laminates with 50 µm GnP paper was reduced by 70%. Furthermore, laminates with rGO coated fabrics demonstrated stable crack propagation under Mode-I loading as compared to GnP based laminates. The fractured surfaces were analyzed using scanning electron microscopy to investigate the underlying fracture mechanisms of the sensors in the composite laminates.

Co-digestion of solid-liquid waste from citrus agroindustrial: Effect of hydraulic retention time and organic loading rate on H2 production in a long-term continuous operation leach bed reactor

The Leach Bed Reactor (LBR) application is a promising alternative for the anaerobic digestion of solid waste and wastewater. In this study, the LBR was continuously operated for 160 days in four different phases, for co-fermentation of solid and liquid waste from the citrus agroindustry, at 37 °C, evaluating the effect of hydraulic retention time (HRT) and organic loading rate (OLR). The maximum volumetric hydrogen production (VHPR) was observed at an HRT of 12h (958.3 mLH2.L-1.d-1); however, the highest hydrogen yield (HY) was identified at an HRT of 24h (104.9 mLH2.g-1CHO). Based on the metabolic characteristics of microorganisms identified in higher relative abundance, by 16S rRNA sequencing, such as Lactobacillus, Caproicoproducens, Bifidobacterium, Olsenella, and Solobacterium, an occurrence of chain elongation pathways in the production of butyric and caproic acids was inferred, with hydrogen production resulting from the lactic acid oxidation. The maximum electricity production potential of 16.3 kWh.m-3 liquor was estimated.

Computational Analysis of the Kinetic Processes of Microbial Electrolysis Cell-Assisted Anaerobic Digestion Using the ADM1

This study deals with the computational analysis of the kinetic processes of microbial electrolysis cell-assisted anaerobic digestion (MEC-AD) for treating raw-waste-activated sludge (WAS), compared to conventional AD, as well as investigating the effect of the organic loading rate (OLR) on the system’s performance. The aim was to derive a mathematical model for the study of MEC-AD using the ADM1 framework, which can be utilized to extract the effect of an applied potential on the kinetics of AD. The experimental data were obtained from the operation of two identical reactors (an AD reactor and an MEC-AD reactor), which were operated at different OLRs. The kinetic parameters extracted from the ADM1 showed that the MEC-AD reactor yielded improved biomass yields, substrate consumption, and first-order disintegration rates, with a predominant contribution to the disintegration of complex particulates, which increased fourfold compared to the AD reactor. Moreover, it enabled operation at higher OLRs (achieving the highest divergence from the AD reactor at the OLR of 4.14 gCOD/(L × d)), therefore accelerating WAS treatment, as well as showing an improved performance at increased solids retention time (SRT). The ADM1 exhibited efficient adaptability and predictability of the kinetic processes and can be effectively used for the optimization of the MEC-AD operation.

Nucleation Mechanism and Rupture Dynamics of Laboratory Earthquakes at Different Loading Rates

The loading rate of tectonic stress is not constant during long-term geotectonic activity and significantly affects the earthquake nucleation and fault rupture process. However, the mechanism underlying the loading rate effect is still unclear. In this study, we conducted a series of experiments to explore the effect of the loading rate on earthquake nucleation and stick–slip characteristics. Through lab experiments, faults were biaxially loaded at varying rates to produce a series of earthquakes (stick–slip events). Both shear strain and fault displacement were monitored during these events. The findings indicate a substantial effect of the loading rate on the recurrence interval and the shear stress drop of these stick–slip events, with the recurrence interval inversely proportional to the loading rate. The peak friction of the fault also decreases with the increasing loading rate. Notably, prior to the dynamic rupture of earthquakes, there exists a stable nucleation phase where slip occurs in a quasi-static manner. The critical nucleation length, or the distance required before the dynamic rupture, diminishes with both the loading rate and normal stress. A theoretical model is introduced to rationalize these observations. However, the rupture velocity of these lab-simulated earthquakes showed no significant correlation with the loading rate. Overall, this study enhanced our comprehension of earthquake nucleation and rupture dynamics in diverse tectonic settings.

Energy Behavior of Sandstone Containing Weak Filling Joints with Multiple Angles under Dynamic Splitting Loads

The impact of weak filling joints with multiple angles on the energy dissipation mechanism is significant for surrounding rock engineering to prevent and mitigate disasters. In the present study, the sandstone samples containing weak filling joints were prefabricated, and dynamic splitting tests were conducted under three nominal loading rates with a modified Split Hopkinson Pressure Bar system. The effects of nominal loading rates and joint angles on time-based curves and energy-based curves were investigated systematically. The test results indicated that the nominal loading rate and joint angle had remarkable influences on energy dissipation characteristics. The sample containing a larger joint angle preferred brittle failure, whereas the sample with a smaller joint angle failed with a plastic feature. Moreover, the reflection energy decreased as the joint angle increased, which was opposite to the evolution tendencies of transmission energy and absorption energy. The transmission energy and absorption energy had different sensitivities to changes in joint angle and nominal loading rate. The exponential function could excellently describe the dependence of transmission energy, reflection energy, and absorption energy on joint angles. With the incremental joint angle, the energy reflection ratio had a contrary tendency to the energy transmission ratio.

Experimental study of insoluble aerosol wash-down by condensate on quasi-horizontal plate

The washing behavior of radioactive aerosol caused by condensation on floor is of great significance for evaluating radioactive migration in case of an accident in nuclear power plant. Compared to the inclined or vertical wall, on a nearly horizontal floor the aerosol particles may have a characteristic transport progress, considering the slower speed of the condensate flow and weaker erosion ability to wash-down aerosol due to insufficient shear stress. An experiment in the steam environment is conducted on this study, focusing on condensation and wash-down of deposited insoluble aerosol particles on a 0.4° quasi-horizontal plate. An exponential trend of removed aerosol mass is obtained based on the experimental aerosol transport process on the quasi-horizontal surface. This paper evaluated the effects of particle load and condensation rate on transport process and removed mass. Furthermore, based on the experimental results, a fitting empirical correlation between dimensionless aerosols' removal mass and dimensionless mass of condensate are obtained by modifying the conditions of different condensation rates and aerosol loads.

Investigations on dynamic failure behaviors and energy transfer efficiency of heat-treated high-performance concrete under multiaxial constraints

In order to explore the internal relationship between the energy transfer efficiency and the dynamic mechanical response of thermal damage concrete under the coupling action of multi-axial stress constraint and high strain rate, the dynamic compression test of high performance concrete is carried out by using the true triaxial Hopkinson pressure bar test system and the combined effects of high temperature, multi-axial stress constraint and impact velocity are fully considered. The temperature effect and strain rate effect of the dynamic failure mechanical behavior of concrete under biaxial stress constraint are analyzed, and the influence mechanism of temperature, prestress and impact velocity on the energy transfer efficiency of the failure process of concrete samples is discussed. The research results show that the dynamic strength of concrete under biaxial stress constraint has both the strengthening effect of loading rate and the hardening and weakening effect of temperature. The dynamic failure of concrete subjected to different degrees of thermal damage under biaxial stress constraint changes from brittleness to plasticity (with 300 °C as the turning point). Under the biaxial stress constraint, the energy absorptivity and reflectivity decrease with the increase of the intermediate principal stress, while the transmittivity shows the opposite trend. When the biaxial stress constraint state is changed to true triaxial constraint state, the energy transfer efficiency changes abruptly along the original evolution trend. The sensitivity of high temperature and stress constraint on the energy transfer efficiency of concrete during dynamic compression is more significant than that of impact velocity. The effects of temperature and stress constraint state (change of intermediate principal stress) on energy dissipation density are positively correlated. The energy dissipation density has an exponential function growth relationship with the dynamic strength and a linear growth relationship with the strain rate.

Effect of loading rate on mechanical properties of autoclaved aerated concrete having steel wool fibres, construction waste and alkaline solution by employing accelerated curing

This paper introduces a new method for developing Autoclaved Aerated Concrete (AAC) blocks, investigating the impact of different loading rates on compressive strength and failure behaviour. Alkaline solution and accelerated curing tank curing were explored as alternatives to conventional methods using aluminium powder and autoclave curing with fly ash. Construction and demolition waste was used as a substitute for fly ash, and chopped steel wool fibres were added to enhance block strength. The blocks were tested under various loading rates, and stress–strain graphs were generated to calculate Young’s modulus of elasticity values. ANSYS software was used for simulation and comparison, validating the accuracy of analytical models. The study shows a correlation between experimental and simulated values, confirming the successful incorporation of CDW and CSWF in AAC block development. Increasing the loading rate during testing leads to lower measured Young’s modulus, indicating strain rate dependency. However, including CSWF enhances Young’s modulus by redistributing stress and restraining crack propagation. The research contributes to understanding AAC's mechanical properties and performance, supporting its potential as a sustainable alternative for masonry materials in structural applications.

CO2 uptake in ethanol-driven chain elongation system: Microbial metabolic mechanisms

CO2 as a byproduct of organic waste/wastewater fermentation has an important impact on the carboxylate chain elongation. In this study, a semi-continuous flow reactor was used to investigate the effects of CO2 loading rates (Low = 0.5 LCO2·L−1·d−1, Medium = 1.0 LCO2·L−1·d−1, High = 2.0 LCO2·L−1·d−1) on chain elongation system Ethanol and acetate were utilized as the electron donor and electron acceptor, respectively. The results demonstrate that low loading rate of CO2 has a positive effect on chain elongation. The maximum production of caproate and CH4 were observed at a low CO2 loading rate. Caproate production reached 1.88 g COD·L−1·d−1 with a selectivity of 62.55 %, while CH4 production reached 129.7 ml/d, representing 47.4 % of the total. Metagenomic analysis showed that low loading rate of CO2 favored the enrichment of Clostridium kluyveri, with its abundance being 3.8 times higher than at of high CO2 loading rate. Metatranscriptomic analysis revealed that high CO2 loading rate induced oxidative stress in microorganisms, as evidenced by increased expression of heat shock proteins and superoxide dismutase genes. Further investigation suggested that genes associated with the reverse β-oxidation pathway, CO2 uptake pathway and hydrogenotrophic methanogenesis pathway were reduced at high CO2 loading rate. These findings provide insight into the underlying mechanisms of how CO2 affects chain elongation, and it could be a crucial reason for the poor performance of chain elongation systems with high endogenous CO2 production.

Deformation Characteristics and Permeability Properties of Cap Rocks in Gas Storage of Depleted Reservoirs under Alternating Load

Gas reservoirs have significant engineering characteristics of injection and extraction. The reservoir cap rock is subjected to cyclic alternating loading and has the potential risk of seal failure. Therefore, it is necessary to study the stress−percolation−damage mechanism of the reservoir cap rock in depleted gas reservoirs. The rock Mechanics Test System (MTS) was used to study the permeability characteristics of a typical mud shale cap layer under different loading and unloading rates, analyze the deformation characteristics and permeability performance evolution law of the rock under the confining pressure alternation, and study the effects of loading and unloading rate, confining pressure and number of cycles on the permeability of the cap rock. The test results show that with the increase in the number of cycles, the hysteresis loop moves in the direction of axial strain increase offset. The overall morphology is presented as an elongated type, and the damage of the specimen is small in the cyclic confining pressure; At the beginning of the cycling period, the permeability decreases with the increase in the confining pressure in the form of a negative exponential. At the later stage of the cycling period, the permeability basically stays unchanged, and is maintained at a low level; At low confining pressure, permeability also decreases in a negative exponential form with the increase in the number of confining pressure cycles; The greater the loading and unloading rate at the beginning of the cycle, the more the permeability decreases; There is a tendency of sealing improvement under cyclic loading in the gas storage of depleted reservoirs with mud shale as the cap layer. The results of the study can provide technical parameters for the evaluation of the cap sealing of gas storage of depleted reservoirs.

Loading Rate Effect on the Pullout Capacity of OMNI-Max Anchors in Clay Coupled With Multiple Factors

Abstract As the latest development of gravity installed anchors (GIAs), the OMNI-Max anchor has drawn much attention from worldwide due to its unique behavior in the seabed. The pullout capacity of OMNI-Max anchors is a key index in engineering. However, most of the relevant studies were carried out under a quasi-static condition, which do not actually meet the installation and operation requirements. In practice, the anchor may be subjected to both long-term and short-term sharp loading during mooring. As an important environmental variable, it is essential to evaluate the effect of loading rate on the pullout capacity. Since the bearing capacity of OMNI-Max anchors is affected by many factors, it is also essential to explore systematically the coupling effects of the loading rate and other factors, including the anchor embedment depth, the anchor orientation, the bearing area, the loading angle, and the soil strength. Based on the coupled Eulerian–Lagrangian (CEL) technique, numerous analytical cases are designed and calculated by the large deformation finite element (LDFE) method. The loading rates span four orders of magnitude from the quasi-static velocity to 10 m/s (about one anchor length per second), covering a wider range in pulling out of GIAs. The end-bearing capacity factor changes remarkably with the pullout velocity for OMNI-Max anchors, and the increase can even reach more than twice of that in a quasi-static condition. As a result, a succinct explicit expression is constructed in terms of the loading rate and multiple factors, which can be effectively utilized to calculate the end-bearing capacity factor of OMNI-Max anchors in clay under complex conditions.

The effects of ammonium loading rates and salinity on ammonium treatment of wastewater from super-intensive shrimp farming

Treatment of wastewater from super-intensive shrimp farming (SISF) for discharge or recirculation purposes is currently attracting the attention of managers and researchers. The fixed bed biofilm reactor (FBBR) has been successfully used for biological treatment of drinking water as well as for wastewater treatment in aquaculture farm. Ammonium and salinity are important factors affecting the efficiency of pollutants treatment. This paper presents the results of research on ammonium treatment in super-intensive shrimp wastewater by aerobic microbiological process using FBBRs. The results showed that at ammonium loading rates of 0.014; 0.028; 0.049 and 0.070 kg/m3/d, at salinity of 10‰, the ammonium removal efficiencies were 98 - 99; 97.7 - 98.8; 96.8 – 98.7 and 95.7 – 98.0 percent respectively (ammonium concentrations in effluent were 0.05 – 0.1; 0.12 – 0.23; 0.23 – 0.56 and 0.51 – 1.07 mgN/l, respectively), at salinity of 15‰, the ammonium removal efficiencies were 95.8-96.0, 94.5-92.0, 93.1-92.3 and 66.8-68.8 percent respectively (ammonium in effluent were 0.20 – 0.21; 0.55 – 0.8; 1.20 – 1.35 and 7.8 – 8.3 mgN/l, respectively), at salinity of 20‰, the ammonium removal efficiencies were 92.0-96.0, 87.0-89.0, 69.1-70.9 and 59.6-66.0 percent respectively (ammonium in effluent were 0.2 – 0.4; 1.1 – 1.3; 5.1 – 5.4 and 8.5 – 10.1 mgN/l, respectively). This result showed that the influence of ammonium loading and salinity on ammonium treatment efficiency was very significant.

Study on the plant and fish production in the aquaponic system as affected by different hydraulic loading rates

Aquaponics is the combined culture of fish and plants in recirculating aquaculture systems, considered to be an innovative, eco-friendly and sustainable technology. The effect of the hydraulic loading rate (HLR) on the performance of fish and plants in the aquapoinc system was the main aim of this study. Four hydraulic loading rates were applied, 1.2, 1.8, 2.4 and 3.0 m day−1 under stocking density tilapia fish of 5 kg m−3 and lettuce population of 25 plant m−2 for a period of January to March, 2023. Water parameters, plant and fish parameters were determined. The most important results revealed that the highest plant nutrients removal was at HLR of 2.4 m day−1. The highest value of water parameters were found at the HLR of 2.4 m day−1. Root length increased with increasing HLR. Fresh and dry shoot and root weight values were higher at 2.4 m day−1 compared to other treatments under study. Meanwhile, fish growth parameter showed higher values at the HLR of 3.0 m day−1 compared to other treatments. The highest values of weight gain, feed growth rate, specific growth rate and feed conversion ratio were 81.72 g, 1.36 g day−1, 1.88% day−1 and 1.20 g feed g−1 fish, respectively, for all treatments under study.

DEM study on the loading rate effect of marble under different confining pressures

Abstract Based on the conventional triaxial compression test of marble, the microscopic parameters corresponding to the macroscopic mechanical properties of marble were obtained by PFC2D, and on this basis, discrete element method models were established to conduct numerical tests of triaxial compression of marble under different confining pressures and loading rates to study the effect of loading rates on the rock specimens. Under the same confining pressure, brittle damage occurs in marble when the loading rate is low, and the damage type transforms from brittle to ductile as the loading rate increases. The peak strength, cracking stress, damage stress, cohesion, and internal friction angle of marble appear to increase with the increase in the loading rate under the same confining pressure. The characteristic stresses and strength parameters are linearly related to the loading rate. The influence of the loading rate on the peak strength is the most significant. With the increase in the confining pressure, the fitting coefficient of the linear relationship between initiation stress and loading rate decreases from 18.9 to 15.4 for different confining pressures, indicating that the growth rate of initiation stress decreases with the increase in the confining pressure when the loading rate is increased, and the increase in confining pressure suppresses the growth rate of initiation stress with loading rate.

Advanced characterisation of photovoltaics for hail resistance

Climate change is intensifying severe weather events, especially in alpine environments where hailstorms are more frequent and intense. In particular, hail damage seriously affects photovoltaic systems. The severity of hailstorms as well as impact responses are important factors in mitigating loss, so the first research area that needs to be addressed is the resistance of photovoltaic modules to hail. According to IEC 61215 standard, a PV module should resist at the minimum to the impact of a hailstone of 25 mm launched at 80 km/h, while the Swiss VKF standard demands a minimum of 30 mm, practically making it 40 mm or more. The hail test stand is being enhanced to support larger diameters and higher speed, enabling module manufacturers to assess their products with adequate safety margins. Larger ice ball requires evaluating sample preparation, repeatability, representativity, and the ability to handle high speeds and masses in order to minimise uncertainty in impact energy. In this preliminary study, ice ball samples with diameters of 25, 40, and 70 mm were tested on a Hopkinson bar at speeds from 20 to 140 m/s and temperatures from −5 °C to −20 °C. The effects of impact velocity, loading rate, and impact time were examined. Finally, the first tests on PV modulus with large ice ball and high velocity are presented.

Effect of different loading rates on the fracture behavior of FRP‐reinforced concrete

AbstractIn order to study the effect of different loading rates on the fracture behavior of fiber‐reinforced polymer (FRP) reinforced concrete, the fracture experiments of FRP‐reinforced concrete beams under different loading rates were carried out. The calculation method of fracture toughness was given by analytic deduction, and the effects of different loading rates on the fracture parameters were analyzed. The experimental results show that there are three critical points in the fracture process of FRP‐reinforced concrete beam, which are the crack initiation load, crack resistance load, and ultimate load points. The effective crack length at the crack resistance load point increases with the increase of loading rate, and the effective crack length at the ultimate load point does not vary as the loading rate. With the increase of loading rate, the elastic modulus and fracture toughness increase gradually, and there is a logarithmic relationship with the loading rate, which has obvious rate correlation. The fracture process zone (FPZ) length of FRP‐reinforced concrete beams gradually decreases with the increase of loading rate.

Effects of loading rates on interfacial adhesion between aggregates and asphalt binders

Effects of loading rates on the adhesion between aggregate minerals and asphalt materials were elucidated through combined simulation and experimental studies. Silica, calcium carbonate and alumina represented the primary aggregate minerals, whereas saturate, asphaltene, resin, and aromatic represented the primary asphalt components. In the experiments and simulations, asphalt components and binders were pulled away from mineral interface at various loading rates. The relation between adhesion and loading rates was identified for the low-speed, transition and high-speed regions. Microstructural evolutions were characterized at different loading rates. Results showed that alumina generated higher adhesion to asphalt than silica and calcium carbonate, which agreed with prior experimental findings using particle probe scanning force microscopy. At low velocities, the gradual delamination of mineral-asphalt interfaces resulted in small adhesive forces. But at high velocities, the breakage of many bonds within a short period led to high adhesive forces. The study provided further understandings of the interfaces between aggregate and asphalt, which might promote the design and utilization of asphalt material.