Environmental Load Research Articles

Potential of thermal protection improvements in large-scale cryostat development

Tremendous efforts are being pursued by experimentalists worldwide in the designing of cryostats to minimize the most dominant radiation heat load over the cryogenic liquid kept inside it. These endeavors are imperative to secure the safe, consistent, and reliable performance of detectors, notably for experiments delving into the investigation of rare physics events, particularly those moving towards ton-scale capacities. In these experiments, maintaining a stable temperature of the cryogenic liquid is crucial. This stability helps in minimizing thermal noise and reducing the loss of cryogenic liquid by mitigating its evaporation rate, and this can be accomplished by reducing the ambient heat load coming from the outer hot wall towards the inner cold wall of the cryostat. Current work scrutinized the impacts of having no insulation, a single-layer insulation, and Multilayer Insulation (MLI) techniques on thermal protection from environmental heat loads at the cryostat’s cold wall boundary, with a particular emphasis on the effectiveness of a single-layer insulation strategy against radiative heat load, a key precursor to MLI technology. The effectiveness of single-layer insulation was quantitatively analyzed for reducing heat load in large-scale rare event searches, using GERDA as an illustrative example and focusing on an optimized configuration. Performance metrics include ambient temperature, cryogenic liquid, emissivity, and the placement of insulation for optimal efficiency. The incorporation of a single intermediate layer positioned near the cold wall boundary results in a significant heat load reduction of 57% for the GERDA geometry compared to a scenario without such a layer. A feasible decrease in emissivity from the customary O(0.01) for insulation materials down to O(0.001–0.0001) could bring about substantial reductions in heat load, potentially by factors spanning approximately 8 to 90. In the scenario involving liquid helium (4.15 K), for example, as the ambient temperature surrounding the cryogen is lowered to (200, 150, 100, 50) K from room temperature, the heat load diminishes by 80%, 94%, 98.8%, and 99.9%, respectively. Moreover, optimally positioning single intermediate layer, crafted from ultra-radiopure material, as close as achievable to the cold wall boundary with minimal emissivity can yield a substantial reduction in heat load, estimated ∼(40–60)%, thereby diminishing the evaporation rate of the cryogenic liquid.

Development of high-efficient asphalt pavement modeling software for digital twin of road infrastructure

To develop digital twin (DT) of road infrastructure, one critical element is computation of pavement responses (strains, stresses, and deflections) under traffic and environmental loading. This study aims to develop high-efficient asphalt pavement modeling software based on semi-analytical finite element method (SAFEM) for DT application. The algorithms address important aspects in vehicle-tire-pavement interaction modeling, such as dynamic vehicular loading, three-dimensional (3-D) non-uniform tire contact stress, viscoelastic behavior of asphalt material, and interface bonding condition. The simulation accuracy is verified by comparison with full-scale test and field measurements, and the relative differences are around 5 % to 20 %. Techniques including optimized discrete Fourier transform, parallel computing, graphics processing unit (GPU) acceleration, and sparse matrices are implemented for computation efficiency. As compared to the traditional 3-D FEM, SAFEM shows significant savings in computation time and storage usage. The high efficiency and accuracy make the software full of potential to be applied for DT of roadway infrastructure.

Income-based environmental effects of family food consumption and the affordability towards healthy diets

Environmentally sustainable diets are attracting increasing attention, but the environmental impact of diets with different income residents is still poorly understood. Based on the environmental footprint method, we explored the environmental impact of food consumption in China from 2000 to 2020, and used the Logarithmic Mean Divisia Index (LMDI) model to investigate its driving factors. Furthermore, we constructed a multi-objective optimization model, incorporating the affordability indicator, to optimize a healthy diet pattern. The results show that: (1) The food diversity index (FDI) was directly proportional to income, and geographically, the FDIs of economically developed provinces were higher than that of economically developing provinces. (2) The environmental footprint caused by food consumption was gradually increasing, with 60 % of the carbon footprint of low-income residents coming from grain and pork. (3) Dietary affordability was a major factor in increasing environmental footprint. High-income residents had greater access to milk, meat, etc., which had a greater negative environmental impact. We put forward suggestions on dietary optimization and affordability for different income residents, with a view to achieving nutritional and healthy diets of Chinese while generating minimum resource and environmental load, and promoting the transformation of the agro-food system.

A life cycle assessment of CCU process to produce a nanocomposite from ethanol plant CO2 emission

The use of rubber septa for controlled release of semiochemicals has raised important discussions about their efficiency and environmental impact since they are composed of fossil raw material. The life cycle assessment (LCA) of the synthesis of a nanocomposite type calcium nanocarbonate/Kraft lignin (NC-CN-KL) obtained from CO2 capture aimed to quantify the environmental loads involved in the production process. The synthesis evaluated by the LCA was performed on a laboratory scale, since it is a synthetic route classified as technological readiness level 4 (TRL-4) and is in the study and development stage. The LCA was performed according to the principles of the ISO 14044/2006 series of standards, from 101.854 g of nanocomposite as a functional unit. The limitations of the study arose from its synthesis scale, absence of LCA data on the rubber septa and other nanocomposites. The results obtained in the LCA identified electricity and other energy generation processes as the largest contributors to environmental loads for all environmental impact categories studied and suggest that research should focus on these inputs when choosing the sources used in energy nanocomposite formulation processes. LCAs for this synthesis to obtain NC-CN-KL should be carried out on a pilot scale, and it is expected that this work will contribute to the formulation of the material and decision-making, especially regarding the choice of the energy matrix.

Application for Predicting Vessel Motion Enhances Operability in Offshore Drilling

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 35341, “Enhancing Energy Efficiency and Operability in Offshore Drilling Operations: Validation and Benefits of a Machine-Learning-Based Vessel-Motion-Prediction Application,” by Daniel A.C. Canache, Massimiliano Russo, and Rune Haakonsen, Kongsberg Maritime, et al. The paper has not been peer reviewed. Copyright 2024 Offshore Technology Conference. _ This paper delves into the framework of a new application that leverages advanced machine-learning (ML) techniques in conjunction with metocean forecasts to predict vessel motions and thruster loads. The discussion encompasses the key role of diverse input factors in shaping prediction accuracy and outlines strategies to address inherent uncertainties associated with methods, weather forecasts, and the stochastic nature of the underlying problem. Methods, Procedures, and Process Traditional Physics-Based Vessel Model. A physics-based model of the vessel is used to train the ML model. As such, the accuracy of the physics-based model is critical to the success of the ML model. The model is built using vessel-specific hydrodynamic data, mass data, and thruster-control software. The thruster-control software is extracted from the actual vessel to ensure that the same settings are being used in the model. The model is used to execute time-domain simulations, which include second-order effects, from which prediction targets [six degrees-of-freedom (DOF) motions and thruster usage] are extracted. As shown in Fig. 1, four environmental components are typically considered: wind waves, swell waves, wind, and current. To train an ML model capable of predicting in any given weather condition, environmental parameters are varied over thousands of simulations. Physics-Informed Neural Network (PINN) Architecture. The adopted architecture for the ML model is a PINN, a model architecture that offers several advantages. By integrating vessel-specific hydrodynamic data, the model becomes grounded firmly in the underlying physical phenomena. Furthermore, the architecture facilitates the model’s comprehension and assessment of the environment by enabling the compilation of individual loads into an overall load acting on the vessel. Ultimately, the analysis of resultant loads on the vessel provides a means to compare various environmental load cases directly in relation to the vessel’s response. Optimizing the Training Matrix. The optimal training matrix should span the environmental parameter space up to the vessel’s station-keeping capacity while minimizing the number of necessary load cases. Given the computational expense and prolonged execution times associated with time-domain simulations, it is important to maintain a manageable number of cases. While resultant loads facilitate the comparison across different environment load cases, a systematic algorithm is needed for case selection. To address this requirement, a similarity metric incorporating cosine similarity and Euclidean distance was implemented. The downside to the Euclidean distance is that, at low magnitudes, the distance will be low regardless of direction. This is mitigated to some extent by combining the measure with the cosine similarity. The cosine similarity will be high if two vectors are close in direction regardless of their magnitudes. For the specific problem described in the complete paper (vessel responses), it is desirable that the similarities at low loads stay high because the response also will likely be low.

Acoustic emission for monitoring of fatigue damage in concrete elements of wind turbine towers

Wind energy has become an important player in the energy transition in Germany. Towers of onshore wind turbines are often designed as hybrid structures: the lower part is made of prestressed concrete whereas the upper part is made of steel tubes. The tall structures are permanently subjected to dynamic loads. A research project of BAM as part of the joint project WinConFat-Structure focusses on the development of techniques to monitor fatigue damage evolution in the concrete part. Results of a previous project show that a combination of ultrasonic and acoustic emission testing can give an indication for critical conditions near the end of the fatigue life of the concrete. In the ongoing project acoustic emission sensors have been installed at the base and at the transition piece between concrete and steel of a hybrid wind turbine tower. Beside of acoustic emission measurement the sensor spacing allows for measuring the concrete ultrasonic velocity along the circumference in both levels. Additional measurements like strain, temperature, inclination, or acceleration allow for comparison of environmental loads and change of acoustic properties of the concrete. The paper focusses on first acoustic measurements recorded since December 2023 in comparison to operating data of the wind turbine.

Floating body motion coupling study and economic evaluation of different floating photovoltaic arrangement schemes under hybrid solar-wind power generation

Abstract Reducing the number of anchor points and moorings for floating platforms is one of the ways to reduce the integration and maintenance costs of floating offshore wind and solar farms. This paper focuses on the technical feasibility and economic viability of reducing the number of anchor points and moorings for floating offshore PV platforms by using a monopile of a stationary wind turbine as a mooring anchor point and introducing a shared line system. In this paper, three different floating solar layouts and their corresponding mooring systems are numerically evaluated and optimized under different environmental loading conditions using the commercial software OrcaFlex. The results of the study show that the implementation of a shared mooring solution maximizes the cost-effectiveness economically while technically ensuring stable operation.

Harnessing blue light for cost-effective and eco-friendly antimicrobial solutions in poultry farming

Blue light in the visible spectrum naturally fights bacteria and effectively deactivates various Gram-positive and Gram-negative bacteria and fungi using photodynamic processes. It works against drug-resistant strains within these species and is gentler on mammalian cells than ultraviolet rays or chemicals. This study evaluated blue light as an affordable way to sanitize surfaces in poultry settings, such as eggs and litter. The study used an light-emitting diode array to remove harmful Esche¬richia coli and Staphylococcus aureus from these items and observed how blue light affected their survival rates. Blue light (455 nm) at 30 mW/cm2 for one hour decreased the survival of S. aureus and E. coli on solid agar plates to 29.88% and 21.04%, respectively, compared to non-irradiated cultures. Similarly, on untreated surfaces (such as plastic used for feeding and drinking), the survival rates dropped to 25.8% and 15.6%, respectively. The survival percentages on treated eggs were 50% (S. aureus) and 48.2% (E. coli) and 59% (S. aureus) and 36.46% (E. coli) on treated litter. Hence, blue light technology offers a promising alternative to traditional antimicrobial methods by leveraging specific wavelengths to target microbial cells. This approach can significantly reduce the microbial load in poultry environments, enhancing food safety and animal health. This paper reports the first use of blue light as an antibacterial within poultry research in Iraq, offering a fresh approach to disinfection in this field.

A Multi-Method Approach to Assess the Adoption of Precision Agriculture Technology in Brazil

Precision Agriculture (PA) application aims to increase crop productivity while minimizing environmental impacts. We analyzed the topics most studied in the advancement of crop production in Brazil by applying the concepts of PA using the systematic literature review (SLR). A multi-method approach combined an SLR applying the PRISMA method and secondary data analysis. We found five clusters of technologies using the PA concept related to hardware development and four clusters related to applying technologies to software development in the PA concept. Most topics focused on using sensors to control water (soil and environment), soil electrical conductivity, and data communication. The focus on sustainability led researchers to reduce chemical products related to fertilizers and pesticides using Variable Rate Fertilizers (VRT) and reducing the environmental loading. According to the research results, it was evident that PA technology might help farmers make more accurate decisions about cultivation, production, harvest, and soil management. The availability of decision support systems powered by big data and artificial intelligence to select the best crop for a given season and soil might assist Brazil's sustainable growth of food production.

Методика оценки экологического эффекта от применения биотоплив

Purpose: the fight for ecology in the transport sector is ensured by improving the design of vehicles and engines, the working processes of internal combustion engines, as well as the use of alternative fuels. To determine the rational use of biofuels in vehicles, it is necessary to assess the environmental effect that will be achieved when using them. Methods: the existing methods of estimating exhaust gas emissions from motor vehicles are considered. Based on them, improvements have been made, which include the introduction of additional coefficients that take into account changes in the environmental load depending on the percentage of biofuels mixed with traditional hydrocarbon fuels. Results: the calculation of the environmental effect from the use of biofuels was carried out using the example of adding biodiesel to petroleum diesel fuel, for which, based on statistical data from the US Environmental Protection Agency and data, WE established dependences of changes in annual emissions of harmful substances and carbon dioxide for a heavy-duty cargo vehicle. In addition to the calculation, the article presents graphs of emissions of harmful substances, taking into account their relative aggressiveness and the amount of carbon dioxide released during the combustion of biodiesel mixtures. Practical significance: The proposed method for calculating the environmental effect makes it possible to estimate the volume of emissions of harmful substances and carbon dioxide depending on the concentration of biofuels mixed with traditional fuels. Such an approach can provide an overall picture of the effect of using biodiesel, and at the same time, the coefficients used need to be clarified.

Mechanism of pyrite depression by marine Fe(II)-oxidizing bacteria in seawater flotation

Seawater flotation is a promising technique to reduce environmental and economic loads in mineral processing. This study attempted to depress pyrite, a common gangue sulfide mineral, using two marine iron (Fe) oxidizing bacteria (MFeOB), Thalassospira sp. TF-1 and Mariprofundus sp. E-4, in seawater flotation without pH control; the MFeOB could contribute to hydrophilization of the pyrite surface by oxidation and/or adhesion of bacterial cells. Pyrite or chalcopyrite samples were preconditioned in seawater containing MFeOB for different times (15 min or 30 min). As a result of flotation experiments, the recovery of pyrite preconditioned without MFeOB (i.e., control sample) decreased to 64.2 % after 30 min reaction. The same recovery was observed when pyrite was preconditioned with Thalassospira sp. TF-1, whereas the recovery was successfully decreased to 20.2 % after preconditioning with Mariprofundus sp. E-4 for 30 min. X-ray photoelectron spectroscopy analysis of preconditioned pyrite samples showed no significant difference of Fe-oxidizing compounds between with and without MFeOB reaction, suggesting that the formation of hydrophilic substances such as Fe(OH)3 derived from pyrite oxidation by MFeOB is unlikely to be the main reason for the pyrite depression by Mariprofundus sp. E-4. The adhesion experiment revealed that MFeOB cells could cover the pyrite surface but not the chalcopyrite surface, showing that the hydrophilicity of Mariprofundus sp. E-4 cell caused the pyrite depression. This result suggests that the hydrophilic/hydrophobic properties of bacterial cells are a significant determining factor in pyrite recovery in seawater flotation in the case of MFeOB.

Effects of dynamic thermal conditioning on cognitive load and performance in an office environment

In the design of buildings with minimal environmental impact, the incorporation of higher energy flexibility is becoming increasingly relevant. This approach is associated with dynamic modulations in setpoint temperatures. Until now, a link between indoor temperatures and cognitive performance of workers has been assumed, leading to high energy consumption and overcooling of office environments in summer conditions. However, research focusing on the relationship between thermal indoor environments and cognitive performance has rarely considered the influence of dynamic temperatures or temporal effects. This is the first experimental study aiming to understand the impact of temperature in relation to time of day on the subjective perception of cognitive load and performance under various thermal conditions in real-world office environments. The results indicated no observable relationship between temperature setpoints (25–30 °C) and cognitive performance. Instead, the temporal dynamics of cooling rather than fixed and static temperature setpoints appeared to have an impact.

FPSO ROLL MOTIONS DRIVEN BY SECOND-ORDER FORCES AND THE IMPACTS ON SLWR RISER DESIGN

Abstract The dynamic behavior of risers is highly influenced by the FPU motions, associated with environmental loads, caused by waves, current and wind. Particularly, as well known, under potential flow modelling, wave loads may be represented through power series expansions, with respect to a small parameter ε. First-order wave forces pulsate in the frequency range of the incident wave spectra, whereas second-order wave forces are related to sum or difference frequencies of the same spectra. The so-called second-order difference frequencies forces may then be responsible by resonating motions of the vessel in that range. Significant low-frequency motions due to second order forces are commonly observed in the horizontal plane, resonating low natural frequencies of moored floating systems characterized by low mooring stiffnesses. Recently, however, this phenomenon was also observed for roll motions in several new FPSOs that will operate in the Pre-Salt of Santos Basin. The phenomenon had already been detected in a deep draft semi-submersible in Campos Basin, but only more recently in FPSOs. The new floating units are characterized by high roll natural periods, above the typical wave period range in the pre-salt region, and the roll response to the second-order difference frequencies forces can be significant. This phenomenon was indeed detected in model tests and confirmed by numerical studies. In fact, this additional FPSO roll behavior occurs in typical periods slightly above 20 s, imposing displacements and accelerations that can directly affect the dynamics of the riser top region. The present paper addresses this phenomenon and its possible impact on steel lazy-wave riser (SLWR) designs.

Free vibration and transient response of initially compressed CNT-reinforced composite plates

This paper investigates the linear free vibration and nonlinear transient response of carbon nanotube (CNT)-reinforced composite plates subjected to pre-existent compressive load in thermal environments. CNTs are reinforced into matrix according to uniform and functionally graded distributions. The properties of constitutive materials are assumed to be temperature-dependent while the effective properties of nanocomposite are determined using an extended rule of mixture. Governing equations are established within the framework of classical plate theory incorporating von Kármán nonlinearity and initial geometrical imperfection. Analytical solutions of deflection and stress function are assumed to satisfy simply supported boundary conditions, and Galerkin method is applied to obtain a time differential equation including both quadratic and cubic nonlinear terms. Fourth-order Runge–Kutta numerical integration scheme is employed to determine dynamical deflection-time response of nanocomposite plates. Numerical analyses are presented to consider the influences of CNT volume fraction, CNT distribution, initial compressive load, geometrical imperfection, elevated temperature and plate geometry on the natural frequencies and nonlinear dynamical response of nanocomposite plates. The study reveals that the natural frequency and dynamical deflection are strongly decreased and increased when initial compressive load is increased, respectively. Numerical results also find that the natural frequencies are enhanced and dynamical deflection is dropped as a result of increase in volume percentage of CNTs, respectively.

Synthesis and properties of biomass‐based polymethacrylate comprising chitin‐derived 2‐acetamide‐2‐deoxyisosorbide as a repeat unit

AbstractSynthesis and applications of biobased polymers have been extensively studied in order to reduce the use of petroleum‐based polymers and likewise environmental load. Several biobased polymers have been produced on a commercial large scale to date. However, the lineup of biobased high‐performance polymers with transparency and high glass transition temperature is inadequate and their development is a critical issue. In this article, we design a new biobased polymethacrylate comprising rigid cis‐fused bicyclic 2‐acetamide‐2‐deoxyisosorbide (ADI) as a repeat unit. We have recently invented catalytic transformation systems from chitin as a marine biomass to ADI as a new nitrogen‐containing platform chemical. The ADI‐based polymethacrylate is synthesized via free radical polymerization of the methacrylic acid ester of ADI initiated by (NH4)2S2O8 and N,N,N′,N′‐tetramethylethylenediamine in dimethylsulfoxide–H2O mixed solvent. The molecular weight and its dispersity are estimated by size exclusion chromatography on the basis of polymethylmethacrylate standards. UV–visible spectroscopy demonstrates the high transparency of the polymer in the visible wavelength region. Differential scanning calorimetry analysis of the polymer clarifies the remarkably high glass transition temperature, compared with that of polymethylmethacrylate. The thermal decomposition temperature of the polymer is also evaluated by thermogravimetric analysis. On the basis of the favorable properties of the ADI‐based polymer, the present study proposes it as a nitrogen‐containing biobased polymer useful for real‐world applications. © 2024 Society of Chemical Industry.

Genotype‐by‐environment interaction for wheat falling number performance due to late maturity α‐amylase

AbstractLate maturity α‐amylase (LMA) is known to reduce falling number (FN) in wheat (Triticum aestivum L.), similar to the effect of preharvest sprouting (PHS) and frost, which can result in grain parcels testing below trading thresholds. Hence, Grains Australia mandates that new Australian wheat cultivars must be at a low risk of LMA expression to receive a milling classification. The multi‐environment trial dataset contained 34 environments not affected by PHS or frost and was analyzed using a five‐factor analytic linear mixed model. Factor 1 accounted for 71.4% of the genetic variation in FN, factor 2 accounted for 8.8%, factor 3 accounted for 5.7%, factor 4 accounted for 3.5%, and factor 5 accounted for 3.1%. The interaction class (iClass) summary method was used to assist in the characterization of crossover genotype‐by‐environment interaction (G × E). Poorer FN performance was best observed in the “ppp” iClass, which indicated a minor, but significant, response to crossover G × E. The environment loadings for factor 1 were associated with mild ripening conditions, characterized by fewer days above 28°C, increased rainfall, and increased variation in daily maximum temperature and relative humidity. Factors 2 and 3 were associated with “cool shock” conditions, where the maximum temperature for 1 day was above 24°C followed by at least three consecutive days below 18°C during the grain fill period. This study provides further evidence of the crossover G × E present for FN associated with LMA, poor FN performance in genotypes that express higher levels of LMA, and the environmental conditions that contribute to LMA expression.

Hydrogel and Microgel Collaboration for Spatiotemporal Delivery of Biofactors to Awaken Nucleus Pulposus‐Derived Stem Cells for Endogenous Repair of Disc

AbstractDepletion of nucleus pulposus‐derived stem cells (NPSCs) is a major contributing factor to the attenuation of endogenous regenerative capacity in intervertebral disc degeneration (IVDD). Introducing a hydrogel drug delivery system is a potential strategy for counteracting endogenous cell depletion. The present study proposes a delivery platform for the spatiotemporal release of multiple drugs by combining sodium alginate hydrogels with gelatin microgels (SCGP hydrogels). The SCGP hydrogels facilitated the initial release of chondroitin sulfate (ChS) and the gradual release of an independently developed parathyroid hormone‐related peptide (P2). The combined action of these two small molecule drugs “awakened” the reserve NPSCs, mitigated cell damage induced by H2O2, significantly enhanced their biological activity, and promoted their differentiation toward nucleus pulposus cells. The mechanical and viscoelastic properties of the hydrogel are enhanced by physical and chemical dual cross‐linking to adapt to the loading environment of the degenerated disc. A rat IVDD model is used to validate that the SCGP hydrogel can significantly inhibit the progression of IVDD and stimulate the endogenous repair of IVDD. Therefore, the spatiotemporal differential drug delivery system of the SCGP hydrogel holds promise as a convenient and efficacious therapeutic strategy for minimally invasive IVDD treatment.

On the Consistency of Stochastic Noise Properties and Velocity Estimations from Different Analysis Strategies and Centers with Environmental Loading and CME Corrections

The analysis of the Global NFavigation Satellite System (GNSS) time series provides valuable information for geodesy and geodynamics researcFh. Precise data analysis strategies are crucial for accurately obtaining the linear velocity of GNSS stations, enabling high-precision applications of GNSS time series. This study investigates the impact of different stochastic noise models on velocity estimations derived from GNSS time series, specifically under conditions of environmental loading correction and common mode error (CME) removal. By comparing data from various data centers, we find that post-correction, different analysis strategies exhibit high consistency in their noise characteristics and velocity estimation results. Across various analysis strategies, the optimal noise models were predominantly Power Law with White Noise (PLWN) and Fractional Noise with White Noise (FNWN), with the optimal noise models including COMB/JPL, COMB/SOPAC, and COMB/NGL for approximately 50% of the datasets. Most of the stations (approximately 80%) showed velocity differences below 0.3 mm/year and velocity estimation uncertainties below 0.1 mm/year. Nonetheless, variations in amplitudes and periodic signals persisted due to differences in the processing of raw GNSS observations. For instance, the NGL and JPL datasets, which were processed using GipsyX 2.1 software, showed higher amplitudes of the 5.5-day periodic signal. These findings provide a solid empirical foundation for advancing data analysis methods and enhancing the reliability of GNSS time series results in future research.

Comparative Analysis of Machine Learning Classifier Models for Predicting Student Cognitive Load and Performance Outcomes in Moodle Learning Environment

Comparative Analysis of Machine Learning Classifier Models for Predicting Student Cognitive Load and Performance Outcomes in Moodle Learning Environment

Combined extension and torsion of hydrogels with chemo-mechanical coupling: Revealing positive poynting effect

In this paper, combined extension and torsion of hydrogel subject to a chemo-mechanical coupled loading is described in the framework of continuum mechanics, where the free energy density consists of the elastic, mixing and chemical contributions. A simplified, closed-form and exactly analytical solution to the mechanical response is obtained, which accounts for the coupling effect of external loading, chemical potential and microstructural parameters, such as crosslinking degree, Flory-Huggins parameter, etc. In particular, the effect of free swelling and microscopic diffusion on deformation of the hydrogel at equilibrium state is discussed, reaching some fundamental conclusions. Negative axial forces are captured, revealing the typical positive Poynting effect where the cylinder tends to elongate on twisting, and an inhomogeneous deformation, induced by torsion, along the radial direction is demonstrated. Furthermore, the dynamic competition between external loading and solvent environment is revealed and investigated, where the direct connection between internal micro-physical parameters and macroscopic deformation is demonstrated. The theoretical results presented in this paper may provide predictions and guidance for the mechanical analysis and design of hydrogel cylinder subject to extension and torsion in a solvent.