Strain Behavior Research Articles

Root anatomy and biomechanical properties: improving predictions through root cortical and stele properties

PurposeQuantifying the stability of individual plants or their contribution to soil reinforcement against erosion or landslides requires an understanding of the tensile properties of their roots. This work developed a new analytical model to understand the tensile stress–strain behaviour of a single root axis, which is the first to incorporating root anatomical features, in order to reduce the existing uncertainty in predictions.MethodsThe root was modelled as a linear elastic stele connected to a surrounding linear elastic cortex by means of a linear elastic stele–cortex interface. By solving for force equilibrium, an analytical solution for the full tensile stress–strain behaviour — including any intermediate brittle failures of the stele, cortex and/or interface — was obtained. This model was compared to tensile tests and laser ablation tomography for maize roots.ResultsThe new modelling approach demonstrated that the root tensile strength is fully determined by the strength of the stele alone, which was an order of magnitude larger than that of the cortex while also 3–4 times stiffer. The reduction in root stiffness beyond the yield point was linked to continuing fracturing of the cortex and debonding along the stele–cortex interface. A larger proportion of the variation in experimentally measured biomechanical characteristics could be explained compared to root diameter power-law fitting methods typically applied in the literature.ConclusionStele and cortex biomechanical properties are substantially different, affecting the tensile behaviour of plant roots. Accounting for these anatomical traits increased the accuracy root biomechanical properties from tensile tests.

Influence of Cross-Correlation on the Modelled Uncertainty in Stress–Strain Behavior of Soft Clays

Reliability-based design is increasingly being applied to geotechnical problems because it allows the robust consideration of various sources of uncertainty, such as the inherent variability of soil properties. Some soil properties, however, are mutually dependent, and ignoring this cross-correlation may lead to biased estimates of the probability of unsatisfactory performance. Hence, in this study, the Gaussian copula was used to evaluate how the applied cross-correlation or independence between the compressibility properties affects the uncertainty in the stress–strain response of two marine soft clays. Two settlement calculation methods were considered: the compression index and Janbu tangential stiffness methods. The correlation coefficients were defined from the site-specific oedometer data at two extensively studied clay sites, and from a database. The simulated oedometer curves were compared to the observed variability in the site-specific data. The settlements in the clay sublayers were then computed, and different cases were compared by means of boxplots. It is concluded that the Janbu method leads to a significant overestimation of uncertainty in settlement if the cross-correlation between the compressibility parameters is ignored. On contrary, the compression index method seems less sensitive to the assumed correlation structure, and as such, the parameters can be treated as independent in most cases.

Statistical analysis of serrated flows in CoNiV medium-entropy alloy

The Portevin–Le Chatelier (PLC) effect induced by dynamic strain aging is commonly observed in various alloys. The stress-drop magnitude of serrations and the critical strain at which serrations occur are two pivotal features characterizing serrated flow. This study investigates the temperature (160–460 °C) and strain rate (6 × 10−4 s−1–2 × 10−2 s−1) dependence of the serrated flow behavior in the CoNiV medium-entropy alloy through uniaxial tensile tests. Under the guidance of the mean-field theory, a scale theory has been applied to derive a scale function and scale indices that can be used to predict the distribution of stress drops. A normal PLC behavior of critical strain is fitted using the dislocation pinning model, demonstrating the presence of specific solute atoms conforming to the dislocation pinning model within medium-entropy alloys.

Electrochemical behavior of Newcastle virus La Sota strain (Newvac vaccine) in the presence of gold nanoparticles as sensitizers investigated on Au electrode

The use of advanced electrochemical methods provides a significant methodological approach to a variety of tasks and research problems in bioelectrochemistry. Of particular importance in terms of bioelectrochemical aspects is the electrochemical behavior of viruses at charged interfaces. The gold electrode is considered ideal for investigating the behavior of biomolecules in aqueous media. Gold nanoparticles (nAu) have unique properties that allow them to be used to facilitate electron transfer between the electrode surface and biomolecules, making them a promising choice as a bioelectrochemical catalyst. The aim of the study is the analysis and physicochemical characterization of the Newcastle virus (NCV) La Sota strain, Newvac vaccine in phosphate buffer solution (PB) using gold nanoparticles as sensitizers. With respect to the electrochemical and electrical parameters, the Au/electrolyte interface constituted a system studied by Open Circuit Potentiometry (OCP), Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS), Square Wave Voltammetry (SWV) and Chronopotentiometry (CP) in association with UV-Vis spectrophotometry. Gold nanoparticles have the role of sensitizing the redox processes in which the La Sota virus participates, as indicated by the amount of charge passing through the interface associated with anodic processes (Qa / Qc) increases from 0.31 (PB), 0.43 (PB-nAu), 0.54 (PB_NCV) to 0.61 (PB_nAu_NCV).

Mating and oviposition of a breeding strain of black soldier fly Hermetia illucens (Diptera: Stratiomyidae): polygynandry and multiple egg-laying

Abstract Black soldier fly (BSF), Hermetia illucens, is a promising species to valorise organic wastes and agricultural co-products into nutrient-rich animal feed. Thus, basic knowledge of its reproductive behaviour is needed to optimize its rearing processes and future selection. In this study, we investigated the reproductive behaviour (mating and egg-laying) of a mass-breeding BSF strain to (1) determine whether their females were monandrous or polyandrous, (2) describe the impact of multiple mating on egg production and fertility, and (3) describe where and when caged individuals mate and lay eggs. Newly emerged adults were individually tagged with acrylic paint to monitor their mating and egg-laying behaviour during their entire lifetime. Our results indicate that adults mated on average three times before dying, with different or even former partners. Some of them mated up to nine times. We also provide the first observation of multiple egg-laying for domesticated H. illucens females and show that virgin females can lay unfertilized eggs, in smaller quantities compared to mated ones. Finally, this study provides the first evidences that H. illucens can be polygynandrous and that multi-mated females can lay eggs several times, thus increasing egg production, in mass breeding conditions.

How to design and execute multiaxial fatigue tests for wind turbine blades without sensitive design data?

This article proposes a methodology to design and execute multiaxial fatigue tests for wind turbine blades without the need to use sensitive design data, such as blade cross-sectional geometry. An approach based on bending moments is used, which matches the actual strain behavior of the material in all regions of beam-like structures under cyclic loading. To facilitate the implementation of the proposed methodology, a numerical validation of the equality between damage indices obtained from bending moments and strains is carried out using a commercial blade of fully known design. Then, an experimental demonstration of how to obtain the proposed bending-moment-based damage indices during real fatigue tests is performed using a large commercial blade with unknown design. It is expected that with the application of the proposed methodology, better fatigue tests can be carried out for these structures than those designed following current standards.

Effect of temperature on post-yield behavior of PVC foams

Experiments were conducted on Divinycell HCP30 foam to develop equations predicting its elastic and post-yield behavior from − 40 to + 60 °C. In these experiments, the foam was subjected to post-yield cyclic tension, compression and shear and monotonic biaxial tension and compression loading in the environmental chamber of an MTS servo-hydraulic machine. Elastic modulus and yield strength of the foam were found to decrease linearly with increasing temperature and could be expressed by a single equation in terms of room temperature properties. Post-yield behavior involved plasticity, viscoelasticity, and damage. An elastic–plastic viscoelastic damage model was used to predict post-yield behavior of the foam at different temperatures. Temperature dependent plastic hardening and viscoelastic damage functions were extracted from the experimental results and used to simulate elastic and post-yield stress–strain behavior in ABAQUS Explicit using a user-defined material subroutine. The ABAQUS user-defined material was validated with experiments on Divinycell HCP30 foam sheets at various temperatures. Good comparisons were found between ABAQUS and experimental results.

Estimation of stress–strain behavior in surrounding rock mass around deep underground openings using a set of instrumental and numerical methods

Estimation of stress–strain behavior in surrounding rock mass around deep underground openings using a set of instrumental and numerical methods

An Initial Case Study of the Computational Modeling of Cord–Rubber Segments

This paper presents an initial study of the computational modeling for determining the stress–strain behavior of the cord–rubber segment, tailored to be used as a flexible member in the construction of torque transfer coupling in railway vehicles. The presented computational models use the multibody simulation approach for the assessment of segment deformation under diverse loading characteristics. The results are then used in the finite element computational models of the cord–rubber segment. The computational model is validated through tension tests of cord–rubber segments. The homogenized and microstructural models show their ability to simulate the overall stiffness of the segment relatively accurately in tension, but they are limited in not being able to include the influence of the segment’s manufacturing technology. The micro-scale computational model then incorporates realistic representations of cord bundles, considering various cross-sectional shapes, whereas a very important factor significantly influencing the correlation of the results of the technical experiment and simulation is the consideration of the manufacturing technology in the process of building the computational model. The results show that the computational modeling approach in this work can be used for the determination of the optimal manufacturing technology conditions with regard to the stress–strain behavior of the given segment.

Characterization of the Human Plasma Biofilm Model (hpBIOM) to Identify Potential Therapeutic Targets for Wound Management of Chronic Infections.

The treatment of chronic wounds still represents a major challenge in wound management. Recent estimates suggest that 60-80% of chronic wounds are colonized by pathogenic microorganisms, which are strongly considered to have a major inhibiting influence on the healing process. By means of an innovative biofilm model based on human plasma, the time-dependent behavior of various bacterial strains under wound-milieu-like conditions were investigated, and the growth habits of different cocci species were compared. Undescribed fusion events between colonies of MRSA as well as of Staphylococcus epidermidis were detected, which were associated with the remodeling and reorganization of the glycocalyx of the wound tissue. After reaching a maximum colony size, the spreading of individual bacteria was observed. Interestingly, the combination of different cocci species with Pseudomonas aeruginosa in the human plasma biofilm revealed partial synergistic effects in these multispecies organizations. RT-qPCR analyses gave a first impression of the relevant proteins involved in the formation and maturation of biofilms, especially the role of fibrinogen-binding proteins. Knowledge of the maturation and growth behavior of persistent biofilms investigated in a translational human biofilm model reflects a starting point for the development of novel tools for the treatment of chronic wounds.

Experimental and analytical investigation of a model towards predicting the compressive stress–strain behavior of Graded Glass Fiber Reinforced Concrete (GGFRC) using fiber reinforcing index

AbstractThe stress–strain behavior of graded glass fiber reinforced concrete (GGFRC) is a crucial factor in its performance and appropriateness for diverse applications. In the present study, experimental and analytical methods were used to develop a model for the stress–strain behavior of GGFRC under uniaxial loading. The experimental program is designed to investigate the impact of mono glass fibers (3, 6, 12, and 20 mm) with varying volume fractions (0.1%–0.5%) and graded glass fibers (combinations of 3 + 6 + 12 + 20 mm) on the behavior of concrete of M50 grade. By grading glass fiber lengths in the concrete, GGFRC's pre‐peak strength and post‐peak deformation have increased, allowing the composite to control the various scales of cracking. A uniaxial compressive stress–strain model has been developed utilizing the fiber reinforcing index to predict the stress–strain curves of GGFRC in compression. The fiber reinforcing index, which is a measure of the quantity of fiber reinforcement in the material, is used as a variable in the current model to observe how it impacts the material's behavior. This would help evaluate the material's behavior under uniaxial compressive loading conditions and then use that data to develop a mathematical model that can predict the material's response under other conditions. Finally, it can be concluded that there is a significant correlation between the experimental results and the proposed analytical model.

A new method to characterize the nonlinear magneto-viscoelasticity behavior of magneto-active elastomers under large amplitude oscillatory axial (LAOA) loading

The nonlinear viscoelasticity of magneto-active elastomers (MAEs) under large amplitude oscillatory shear (LAOS) loading has been extensively characterized. A reliable and effective methodology, however, is lacking for such characterizations under large amplitude oscillatory axial (LAOA) loading. This is partly due to complexities associated with experimental compression mode characterizations of MAEs and in-part due to their asymmetric stress–strain behavior leading to different elastic moduli during extension and compression. This study proposes a set of new nonlinear measures to characterize nonlinear and asymmetric behavior of MAEs subject to LAOA loading. These include differential large/zero strain moduli and large/zero strain-rate viscosity, which could also facilitate physical interpretations of the inter- and intra-cycle nonlinearities observed in asymmetric and hysteretic stress–strain responses. The compression mode stress–strain behavior of MAEs was experimentally characterized under different magnitudes of axial strain (0.025 to 0.20), strain rate (frequency up to 30 Hz) and magnetic flux density (0 to 750mT). The measured stress–strain responses were decomposed into elastic, viscous and viscoelastic stress components using Chebyshev polynomials and Fourier series. The stress decomposition based on Chebyshev polynomials permitted determination of equivalent nonlinear elastic and viscous stress components, upon which the proposed measures were obtained. An equivalent set of Fourier coefficients was also obtained for estimating equivalent elastic/viscous stress, thereby facilitating faster calculation of the proposed material measures. The proposed methodology is considered to serve as an effective tool for deriving constitutive models for describing nonlinear and asymmetric characteristics of MAEs.

Evaluation of the inheritance and dominance of behavioral resistance to imidacloprid in the house fly (Musca domestica L.) (Diptera: Muscidae).

The house fly, Musca domestica, is a cosmopolitan species known for its pestiferous nature and potential to mechanically vector numerous human and animal pathogens. Control of adult house flies often relies on insecticides formulated into food baits. However, due to the overuse of these baits, insecticide resistance has developed to all insecticide classes currently registered for use in the United States. Field populations of house flies have developed resistance to imidacloprid, the most widely used neonicotinoid insecticide for fly control, through both physiological and behavioral resistance mechanisms. In the current study, we conducted a comprehensive analysis of the inheritance and dominance of behavioral resistance to imidacloprid in a lab-selected behaviorally resistant house fly strain. Additionally, we conducted feeding preference assays to assess the feeding responses of genetic cross progeny to imidacloprid. Our results confirmed that behavioral resistance to imidacloprid is inherited as a polygenic trait, though it is inherited differently between male and female flies. We also demonstrated that feeding preference assays can be instrumental in future genetic inheritance studies as they provide direct insight into the behavior of different strains under controlled conditions that reveal, interactions between the organism and the insecticide. The findings of this study carry significant implications for pest management and underscore the need for integrated pest control approaches that consider genetic and ecological factors contributing to resistance.

Investigating the mechanical performance and characteristics of nitrile butadiene rubber date palm fiber reinforced composites for sustainable bio-based materials

The recent focus on enhancing sustainability has emphasized the proper utilization of natural fibers and waste materials. Natural fiber reinforced composites have emerged as a promising solution for future bio-based products. This study aims to investigate the synergistic effects between date palm fiber (DPF) and Nitrile Butadiene Rubber (NBR) in order to develop innovative bio-based composites suitable for diverse industrial applications. The composites were produced through a mixing process using a Brabender internal mixer, followed by rolling. Various reinforcement materials and processing conditions were employed to characterize and analyze the mechanical properties of the composites. These properties included tensile strength, tensile modulus, strain, tear resistance, mechanical hardness, and compression behavior, assessed according to ASTM standards. The results revealed that the composites with a 40 wt% fiber loading exhibited the highest elastic modulus and tear resistance, indicating good compatibility and adhesion between the fibers and rubber. Additionally, the composites displayed increased brittleness and strain with higher fiber content. The mechanical hardness of the composites suggested their potential for various industrial applications, with the best results obtained at a 30 wt% fiber loading. Furthermore, the compression strength of the composites, evaluated using the ASTM D395 standard and a compression molding method, displayed significant improvement at a 40 wt% fiber content, indicating favorable characteristics and potential for industrial applications requiring oil, fuel, abrasion, and heat resistance in the form of bio-based products.

Effect of microstructure on the deformation of as-cast [formula omitted]-Mg/LPSO two-phase alloys: An integrated SEM-DIC and crystal plasticity study

The present work investigates the plastic deformation of as-cast Mg/LPSO two-phase alloys with varying LPSO phase volume fractions through a combination of SEM-DIC and CPFE simulations. To this end, the same microstructures observed experimentally were numerically deformed and the predicted strain fields were compared to the experimental ones. The reasonable agreement between the simulations and the experiments confirmed that basal slip in LPSO grains is the prevalent deformation mechanism. Besides, analysis of the experimental strain field in LPSO grains suggested that the relevant length scales governing the strength of basal and non-basal slip in LPSO grains were the LPSO length parallel to the basal plane and the LPSO width perpendicular to it. Finally, discrepancies in terms non-basal slip activity were suggested to be due to an overestimation of the strength of prismatic slip combined with the omission of first-order pyramidal slip in the modeling hypotheses. This study sheds light on the complex interplay between microstructure and deformation mechanisms in Mg/LPSO two-phase alloys. It emphasizes the importance of considering multiple slip modes and accurate CRSS values when modeling such systems. Additionally, it highlights the valuable insights that can be gained through a combination of experimental and computational approaches in understanding localized strain behavior.

Comparison of Tensile and Creep Properties of SAC305 and SACX0807 at Room Temperature with DIC Application

The contribution presents the verification of the methodology of accelerated creep tests from the point of view of obtaining more information about the stress–strain behaviour of the investigated materials using the Digital Image Correlation method. Creep tests are performed on SAC305 and SACX0807 lead-free solders and are supplemented by numerical modelling using the finite element method, considering the viscoplastic model based on the theory of Perzyna, Chaboche, and Norton. The stress–strain behaviour of both solders appears to be very similar at applied strain rates of 0.0002–0.0026%/s and applied creep stresses of 15–28 MPa. Initially, the viscoplastic model is calibrated using an analytical approach. Then, the finite element model updating approach is used to optimise the material parameters based on the simultaneous simulations of creep and tensile tests. As a result, the total objective function value is reduced almost five times due to optimisation. The proposed type of accelerated test with an hourglass specimen proves to be suitable for calibrating the considered class of viscoplastic models. The main benefit is that a single specimen is required to obtain creep curves on various stress levels.

A novel beam model suitable at the microscale

A novel beam model is proposed to address the limitations of existing microscale beam models by introducing a higher-order displacement field assumption for the modified couple stress theory. The governing equations and boundary conditions are derived using the variational principle. Validation through finite element analysis for a simply supported beam problem demonstrates the beam model successfully captures the width-dependent behavior of microbeams, which existing beam models cannot explain. Additionally, the beam model accurately represents the plane strain behavior as the beam width increases and the classical beam behavior at a small length scale parameter.

Phase transitions, baro- and piezocaloric effects in single crystal and ceramics of ferroelectric NH4HSeO4

A study of heat capacity, thermal dilatation and sensitivity to hydrostatic and uniaxial pressure was carried out on single-crystal and ceramic samples of NH4HSeO4. The main parameters of low-temperature successive phase transitions B2 (T1) ↔ incommensurate IC (T2) ↔ ferroelectric P1 (T3) ↔ non-ferroelectric did not depend on the type of samples. The behavior of the volumetric strain and the results of direct measurements of T3(p) contributed to the resolution of the longstanding problem associated with the ambiguity of the sign of the corresponding volumetric baric coefficient. The role of thermal expansion anisotropy in the formation of the piezocaloric effect (PCE) near the ferroelectric phase transition at T3 has been studied. Due to the strong difference in the linear baric coefficients, the main contribution to the barocaloric effect (BCE) comes from the inverse intensive and extensive PCE associated with the a-axis. Compared to a single crystal, ceramics demonstrate lower BCE values, which, however, exist in a wider temperature range, which leads to close values of integral caloric parameters. The strong decrease in both BCE and PCE at low-temperature transformations in NH4HSeO4 compared to the ferroelectrics NH4HSO4 and NH4NH4SO4 is associated with a small change in entropy during three low-temperature phase transitions, ΣΔSi = 2.52 J/mol∙K, which is a consequence of a high degree of structural ordering in selenate as a result of a high-temperature transformation at T0 between the superionic and B2 phases, accompanied by a giant change in entropy, ΔS0≈Rln21.

Evaluation of the strain response of FRP partially confined concrete using FEM and DIC testing

PurposeThis study aims to enhance the understanding of fiber-reinforced polymer (FRP) applications in partially confined concrete, with a specific focus on improving economic value and load-bearing capacity. The research addresses the need for a more comprehensive analysis of non-uniform vertical strain responses and precise stress–strain models for FRP partially confined concrete.Design/methodology/approachDIC and strain gauges were employed to gather data during axial compression tests on FRP partially confined concrete specimens. Finite element analysis using ABAQUS was utilized to model partial confinement concrete with various constraint area ratios, ranging from 0 to 1. Experimental findings and simulation results were compared to refine and validate the stress–strain model.FindingsThe experimental results revealed that specimens exhibited strain responses characterized by either hardening or softening in both vertical and horizontal directions. The finite element analysis accurately reflected the relationship between surface constraint forces and axial strains in the x, y and z axes under different constraint area ratios. A proposed stress–strain model demonstrated high predictive accuracy for FRP partially confined concrete columns.Practical implicationsThe stress–strain curves of partially confined concrete, based on Teng's foundation model for fully confined stress–strain behavior, exhibit a high level of predictive accuracy. These findings enhance the understanding of the mechanical behavior of partially confined concrete specimens, which is crucial for designing and assessing FRP confined concrete structures.Originality/valueThis research introduces innovative insights into the superior convenience and efficiency of partial wrapping strategies in the rehabilitation of beam-column joints, surpassing traditional full confinement methods. The study contributes methodological innovation by refining stress–strain models specifically for partially confined concrete, addressing the limitations of existing models. The combination of experimental and simulated assessments using DIC and FEM technologies provides robust empirical evidence, advancing the understanding and optimization of FRP-concrete structure performance. This work holds significance for the broader field of concrete structure reinforcement.

NSM-CFRP rods with varied embedment depths for strengthening RC T-beams in the negative moment region: Investigation on high cyclic response

Throughout its service life, structural reinforced concrete (RC) encounters cyclic loads and the load amplitude might always vary, leading to a mixed high and low-cycle failure. This research investigates the high cyclic response of RC T-beams strengthened in the negative moment region using near-surface mounted (NSM) Carbon Fiber Reinforced Polymer (CFRP) rods. The distinctive aspect lies in exploring varied embedment depths, including the introduction of half-embedded configurations as an alternative NSM technique. The study comprehensively analyzes load-carrying capacity, failure modes, energy dissipation, ductility, stiffness degradation, and strain behavior, providing insights into the effects of loading rates on structural response. Through an experimental program comparing fully-embedded (BF-D) and half-embedded (BH-D) CFRP rods with a control beam (BN-D) under high-rate cyclic loading, significant increases in ultimate load capacity (21.23% for BH-D and 30.86% for BF-D) are demonstrated despite debonding occurrences. The findings highlight a trade-off between benefits (enhanced ultimate load capacities, improved energy dissipation, and increased stiffness) and drawbacks (reduced ductility and tendencies toward brittle behavior) under high loading rates. Furthermore, a rate-dependent material formula is developed and validated, predicting the flexural strength of the negative moment region in good agreement with experimental results. Finally, this research contributes practical solutions to RC element strengthening challenges and advances understanding of NSM-CFRP-strengthened beam, emphasizing the impact of loading rates on structural response.