Yield Criterion Research Articles

Crack-tip plastic zone and initiation mechanism of rock based on Eshelby stress

The crack initiation and propagation mechanism of rock is significantly related to characteristics of the crack-tip plastic zone due to energy dissipation. In this paper, conservation integral and configurational stress/force is derived by the Noether’s method. The crack-tip configurational stress field is then deduced and analyzed. Additionally, the Drucker–Prager yield criterion of configurational stress is derived and it is used to predict the crack-tip plastic zone of rock. The fracture criteria of rock are also developed based on the critical area and minimum polar radius of the crack-tip plastic zone. Subsequently, the effects of bedding dip angles and porosity on rock mixed mode fracture are investigated, and the fracture resistance of rock is assessed using the resistivity and wave velocity. It is shown that the configurational force as the crack driving force is induced by the invariant transformation of an action integral with respect to translation of a defect. It is also found that the crack-tip plastic zone assessed by Drucker–Prager yield criterion of Cauchy stress is discontinuous at the crack surface while that predicted by yield criterion of configurational stress is continuous. The present fracture criteria take into account the internal friction angle, and the predicted initiation angles and fracture loads are in good agreement with those determined by the maximum tensile stress (MTS) fracture criterion and experiments. The fracture loading envelope decreases with the porosity, bedding dip angles and resistivities of rock, but increases with wave velocity.

Multiaxial yield behavior of 2D re-entrant auxetic cellular materials

A series of re-entrant honeycombs (RH) with different off-axis angles and perturbation parameters are constructed and utilized to numerically explore the multiaxial yield behavior for 2D auxetic cellular materials. The off-axis angle significantly affects the anisotropic properties and Poisson's ratio of RH. The effects of microstructural irregularity on the multiaxial yield surfaces are also evaluated for all of the topologies. Simulation results under principal stress space, mean stress-effective stress space and normal stress-shear stress space reveal that the unique microstructure of auxetic cellular materials makes its mechanical properties significantly different from conventional cellular materials with positive Poisson's ratio. Furthermore, a pressure-dependent anisotropic phenomenological yield criterion is proposed for 2D auxetic cellular materials, which can effectively capture the multiaxial yield behavior of RH with different topologies in principal stress space. The present conclusions provide fresh insights into the microstructural design of auxetic cellular materials and pave the way for their future engineering applications.

Dehydration and Environmentally Friendly Thermal Processing of Excess Activated Sludge

Introduction. Currently, there is a problem with the accumulation of large amounts of production waste. One type of this waste is excess activated sludge, which is a waste product from biological wastewater treatment that has a high moisture content. When excess activated sludge is deposited in beds, problems can arise related to changes in the gas-air environment, the release of unpleasant odors, as well as the contamination of groundwater and soil. Prolonged presence of sediment in sludge beds in oxygen-free conditions leads to its decay and deterioration of moisture-yielding properties. For these reasons, the development of new methods for disposing of large volumes of waste generated during wastewater treatment is essential. The aim of this research is to develop a technique for preliminary neutralization and thermal treatment of excess activated sludge using energy waste. Materials and Methods. The work used excess activated sludge with a moisture content of 98.2% (waste of hazard class IV). Water treatment sludge (waste of hazard class V) was used as a reagent to increase moisture yield. For experimental studies on dehydration, a laboratory centrifuge Elmi CM-6M.01 was used. Tests were conducted under various conditions (500, 1 000, and 1 500 revolutions per second for 1, 2, and 3 minutes), and the value of centrifugation was determined as a criterion for moisture yield in the sludge. Fuel pellets were produced by rolling with technical lignosulfonate as a binding agent. Elemental analysis of the samples was conducted to study the possibility of thermal treatment using an EA 3 000 Euro Vector Analyzer. Results. A comprehensive technology has been developed to clean the resulting gas emissions from solid particles formed during the combustion of fuel pellets and remove them from the furnace in the form of fly ash along with the outgoing gases. This technology also removed sulfur oxides, nitrogen oxides, and polychlorinated dibenzodioxins and dibenzofurans, while beneficially utilizing flue gas heat by reducing its temperature from 900–1 200°C to 140°C. Discussion and Conclusion. The approach proposed in this article for the processing and disposal of large volumes of waste allows for the reduction of moisture content of excess activated sludge and the use of this waste as a secondary energy source. This method is environmentally friendly and addresses both technical and environmental challenges, such as the effective recycling of industrial waste and reducing the anthropogenic impact on soil, air, and groundwater. It also provides an opportunity to generate additional electrical and thermal energy through thermal utilization of waste. The results of this work indicate that it is possible to integrate the use of various types of industrial waste (sewage sludge, water treatment waste, and pulp and paper industry waste) as secondary energy sources. These findings have practical implications for enterprises in both the municipal and industrial sectors with wastewater treatment facilities.

Merging Photorefractive Keratectomy and Collagen Crosslinking: An Analysis of Literature and a Guide to Prevalent Protocols.

The purpose of this review was to summarize the different surgical approaches combining photorefractive keratectomy (PRK) and corneal crosslinking (CXL), present each protocol template in a simple format, and provide an overview of the primary outcomes and adverse events. A literature review was conducted as outlined by the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. Eight different databases were searched. Papers were included if PRK was immediately followed by CXL. Thirty-seven papers met the inclusion criteria of a total yield of 823. The latest research into simultaneous PRK and CXL has been shown to not only stabilize the cornea and prevent keratoconus progression but also improve the visual acuity of the patient. Improvements in uncorrected distance visual acuity and (spectacle) corrected distance visual acuity were found to be significant when considering all protocols. There were also significant reductions in K1, K2, mean K, Kmax, sphere, cylinder, and spherical equivalent. Random-effects analysis confirmed these trends. Corrected distance visual acuity was found to improve by an average of 0.18 ± 1.49 logMAR (Cohen's D [CD] 0.12; P <0.02). There was also a significant reduction of 2.57 ± 0.45 D (CD 5.74; P <0.001) in Kmax. Cylinder and spherical equivalent were also reduced by 1.36 ± 0.26 D (CD 5.25; P <0.001) and 2.61 ± 0.38 D (CD 6.73; P <0.001), respectively. Combining the 2 procedures appears to be of net benefit, showing stabilization and improvement of ectatic disease, while also providing modest gains in visual acuity. Since customized PRK and CXL approaches appear superior, a combination of these would likely be best for patients.

Exploring the yield and yield contributing traits variability in dolichos bean (Lablab purpureus): A character association and path analysis approach

An experiment was conducted during 2019–20 and 2020–21 at ICAR-Central Institute for Subtropical Horticulture, Lucknow, Uttar Pradesh to evaluate the magnitude of variability in dolichos bean [Lablab purpureus (L.) Sweet] genotypes for important horticultural traits and their associations. The observed range and mean variations of the studied traits revealed a significant genetic diversity among the genotypes. The narrow gap in the genotypic (GCV) and the phenotypic coefficient of variation (PCV) for delineated characters indicated that they are governed by genetic factors, and environmental factors had little or no impact on the phenotypic expression of these traits. The traits including pod yield, days taken to first flowering, weight of pod, plant height, and pod width, showed positive GCV, indicating the presence of additive genes action. Traits such as pod weight, days taken to first flowering, and pod width displayed high heritability and moderate genetic advance, suggesting that the high heritability of these traits is due to the effects of additive genes and that genetic gain can be expected through the phenotypic selection. The higher genotypic correlations revealed an inherent association between the traits. Therefore, the selection criterion for high yield was proposed based on the strong character association between plant height, number of pods/cluster, pod width, and pod weight. The number of pods/plant, followed by the number of clusters/plant had the highest direct positive effect on yield. Consequently, pod yield may be increased through selection of heavier pods, more clusters/ plant, and more pods/cluster.

An elastoplastic semi-analytical solution for enhanced geothermal wellbore stability considering temperature-sensitive failure criterion

Temperature alters the rocks’ mechanical behavior and influences the stability and operation of enhanced geothermal wells. The stability of the well is a concern during construction, just after the construction, at the time of production, and injection. Most available analytical and semi-analytical solutions for wellbore stability do not account for rock's temperature-dependent yield behavior. In the present study, we proposed an elastoplastic constitutive model based on the temperature-sensitive yield criterion and a semi-analytical solution for wellbore stability. The applicability of the constitutive model is demonstrated by comparing the experimental results of Comiso limestone with the model output. The model elastic perfectly plastic assumption reasonability captures the stress-strain behavior at elevated temperatures. Temperature-sensitive yield criterion effectively predicts the yield point of Comiso limestone, even the substantial decay in yield stress after the temperature of 400 οC. The semi-analytical solution of wellbore stability analysis is validated using FE (Finite element) analysis. An implementation of the semi-analytical solution is showcased for a vertical wellbore, considering changes in in-situ stresses and temperature. A parametric analysis establishes that external factors, like vertical stress increase, do not consistently decrease the size of the plastic zone. Instead, a specific threshold of vertical stress exists at which the plastic zone radius reaches its minimum value. In the presented case, the least radius of the plastic zone is observed for in-situ vertical stress of 80 MPa. Furthermore, the parametric study examines the impact of horizontal stress, support pressure, temperature, and dilation parameter, which followed the generally reported trends.

Design and validation of a new ring hoop plane strain test for characterizing the anisotropic plastic behavior of tubular materials

The accurate characterization of the plastic behavior of tubular materials is challenging due to the difficulties in acquiring proper specimens for mechanical testing. In this study, we propose a novel testing technique, namely the ring hoop plane strain Test (RHPST), as a supplementary test for characterizing materials experiencing distinct strain paths compared to standard uniaxial tensile tests. To design a suitable ring specimen’s geometry that satisfies the necessary plane strain conditions, we developed a meta-modelling approach merging response surface method (RSM) and the finite element method (FEM). Experimental tests are conducted on RHPST specimens, and 3D digital image correlation (DIC) technique is used to monitor the strain fields within the specimen's gauge section. However, observations indicate the presence of edge effects on the gauge specimen. These edge effects significantly influence and limit the homogeneity of the plane strain field. To tackle this limitation, a correction procedure is developed for separating the authentic plane strain area, constituting approximately 78% of the RHPST specimen's width. Furthermore, we successfully fabricated a novel grooved ring specimen (GRHPST), which exhibits a wider region of the plane strain state encompassing up to 90% of the gauge width, while minimizing the impact of edge effects. The true stress-true strain curve obtained from the GRHPST specimen exhibits exceptional agreement with the curve predicted using the Hill48 yield criterion. Notably, no additional corrections are required for the measured true stress-true strain curve, thereby affirming the efficacy of the GRHPST specimen as an adept test for characterizing the anisotropic plastic behavior of AA6063 tubes.

A numerical investigation into the equivalent parameters of a compressible soil treated by stone columns

A series of triaxial test simulations are adopted to estimate the equivalent strength parameters for compressible soil samples reinforced with stone columns. The simulations utilize the finite difference code, Fast Lagrangian Analysis of Continua in three dimensions FLAC3D. An elasto-plastic model is applied to utilize a Mohr-Coulomb yield criterion. The equivalent strength parameters are estimated using newly proposed formulas for geo-composite materials. The researchers compare the obtained results to the analytical formulas proposed in the literature. Additionally, the equivalent parameters are used in equivalent area models. This study investigates the effect of the replacement area ratio. This study offers two applications. Firstly, it evaluates the safety factor of embankments constructed on compressible soil improved with stone columns. Secondly, it estimates the bearing capacity of strip footings on compressible soil treated with stone columns. In all applications, both individual column and equivalent area models are considered. The proposed equations for the equivalent elastic parameters (E, ν) and the mechanical properties, equivalent cohesion, and internal frictional angle (c and φ) give results that agree with the solutions reported in the existing literature.

Genetic Architecture, Studies to Identify the Selection Criteria for Yield in Long Duration Rice Lines (Oryza sativa L.)

Genetic Architecture, Studies to Identify the Selection Criteria for Yield in Long Duration Rice Lines (Oryza sativa L.)

Experimental and numerical study on mechanical behavior of 3D printed adhesive joints with polycarbonate substrates

AbstractAdhesive joints play a crucial role in enhancing the structural integrity and performance of 3D printed parts. The purpose of this study is to investigate the failure load and behavior of polycarbonate (PC) single lap joints (SLJs) produced by fused deposition modeling (FDM) using experimental and finite element analysis (FEA) methods. The FEA of joints presents a new approach by integrating PC substrates with Hill yield criterion, transversely isotropic material and adhesive layer with cohesive zone modeling (CZM). The study focused on the effect of printing angles (0°, 45°, and 90°) and overlap lengths (12.5 and 25 mm) on the performance of SLJs. The influence of 3D printing parameters on the mechanical behavior of PC joints was investigated by tensile testing of SLJs. The experimental failure load was 1586 N for a 12.5 mm joint at 90° and 4115 N for a 25.4 mm joint at 0°. Comparison of the experimental and FEA failure loads of the joints showed maximum and minimum differences of 11.98% and 1.34%, respectively. This result showed that the proposed model is applicable for determining the joint strength as a function of the printing angle and monitoring the joint damage behavior.

2.5D finite element algorithm based on Drucker-Prager yield criterion

This note regards the embankment as an ideal elastic-plastic material, and introduces the Drucker-Prager yield criterion into 2.5-D FEM. Firstly, the pure elastic trial stress is applied, and the Drucker-Prager yield criterion is used to determine whether yielding will occur or not. Then, the backward Euler integration method and the tangent stiffness method are used to derive the consistent tangent modulus matrix, after which the iterative correction of plastic deformation is realized. Finally, an elastoplastic 2.5D FEM is proposed according to the procedures. Compared with the measured values and existing results, it was found that the elastic-plastic 2.5-D finite element algorithm proposed in this note has good consistency with the measured values. Due to the consideration of the plastic deformation of the foundation soil induced by train moving loads, the present results are slightly larger than those of existing elastic methods.

A multiscale hydro-elastoplastic model for large floating structures in two-dimension

A novel fluid–structural model was presented considering hydro-elastoplastic behavior, which coupled multiple hydro-structural-material scales. A large floating sandwich structure (LFSS) comprising upper and lower high-strength panels and a low-weight core was considered as an illustration. The mesoscale characteristics of materials and elastoplastic parameters of the low-weight perforated components were coupled by utilizing the representative volume element (RVE) method. Through the parameterized relations from RVE analysis, the flexure dynamics model for the floating sandwich structure with an equivalent homogenized core was deduced. With the flexure dynamic equation, yield criterion, and potential flow model, a multiscale hydro-elastoplasticity theoretical model was established, which combined the wave action, hierarchical component, material configuration, and structural behavior. The dynamic responses of the large floating structure under fluid–structure interaction were calculated, and the internal deformation (i.e., core strain) was set as the determining variable for the plastic region. The initially intact floating structure became hinged multi-modules after plastic cracking, and the high-strength layers at the cracking positions behaved as flexible hinges, which was defined as a hydro-elastoplastic process. The elastoplastic state evolutions of the LFSSs with different structural parameters and material configurations were solved for practical optimization. The results indicated that the multiscale coupled calculation model can provide great scientific guidance for designing large floating structures.

Ductile fracture of tubular specimens under non-proportional loading condition

The ductile fracture behaviours of two tubular specimens, a AA6260-T4 macrotube (60 mm diameter and 2 mm thickness), and a SS-304L microtube (2.38 mm diameter and 0.15 mm thickness) under non-proportional loading condition are studied using a combined experimental-numerical approach. The experiments are conducted by loading the tubes under axial force and internal pressure along various non-proportional (i.e., corner) paths until failure by controlling the force/pressure ratio. The plastic behaviours of the tubes are characterized using the non-quadratic anisotropic yield criteria Yld2000-2D and Yld2004-3D. The material models are employed in the finite element (FE) simulation of the tube experiments using Abaqus/Standard (implicit). The FE models, which include thickness imperfection to capture the failure modes observed in the experiments, are then used to probe the fracture parameters inside the tube wall where fracture is likely to initiate. It is observed that the fracture strains from the non-proportional loading results are noticeably different when introduced to the proportional fracture strains, revealing the path-dependence fracture behaviour in tubular specimens.

Deep drawing simulation of dual phase steel using hardening curves and anisotropic parameters from uniaxial and biaxial tensile tests

Among the various factors, the accuracy of the predictions from the numerical simulation of sheet metal forming processes depends on the material model used to define the mechanical behavior of the blank material. The coefficients of the hardening model to define the flow curve and the plastic strain ratios are commonly determined using the uniaxial tensile tests. The advanced anisotropic yield criteria incorporate material flow behaviour and plastic strain ratio in equi-biaxial tension. In this work, deep drawing of a flat bottom cylindrical cup has been simulated using dual-phase steel (DP600) sheets. The biaxial material properties obtained by conducting hydraulic bulge test and cruciform specimen test are used in the anisotropic yield criteria in the simulations. The hardening curves are extrapolated using different hardening laws in which the coefficients are determined from the stress-strain curves obtained from both uniaxial tensile and hydraulic bulge tests. The predicted peak drawing load and thickness variation in the drawn cups are compared with the experimental results of deep drawing.

Mesoscale numerical modeling of unreinforced masonry wall response to underground dynamic loads: A comparative study utilizing FEM and DEM

This study investigates the response of unreinforced masonry walls to dynamic loading induced by underground explosions. A mesoscale numerical modeling approach is employed to capture the nonlinear behavior of the masonry wall. The Menetrey-Willam yield criterion is utilized to represent the wall's nonlinear behavior at the mesoscale level, while the cohesive zone model (CZM) is employed to simulate the behavior of mortar, thereby overcoming the limitations of linear elasticity. The soil is characterized using the modified Mohr-Coulomb model. After calibration against material characterization tests, a numerical model is developed to obtain results that closely match experimental data. Given the disturbed nature of the crater soil, both finite element and discrete element methods are utilized for soil modeling. Comparison between these methods reveals that the discrete element method yields more realistic results in terms of displacement and strain. The study's findings enhance our understanding of the response of unreinforced masonry walls to dynamic loading and offer valuable insights for future structural designs and safety assessments.

Time-Dependent Fuzzy Reliability Analysis of Concrete Slab during the Initial Water Storage Period of CFRD: A Case Study

The concrete-faced rockfill dam (CFRD) has been widely constructed worldwide, and the reliability of the concrete panels, the most important containment structure, is critical to the safety of the CFRDs and downstream communities. Several practical projects show that concrete slab cracking usually occurs during the water storage period, which can be attributed to the rapid increase of hydrostatic pressure and uneven settlement of the dam body. In this paper, a time-dependent reliability analysis method considering the fuzziness of the failure criterion is presented to assess the slab cracking risk of the Houziyan CFRD during the water storage period. Based on the observed deformation, the material parameters are calibrated to ensure the fidelity of the numerical simulation. Based on the Drucker–Prager yield criterion and tensile strength criterion, the response surface method is utilized to construct the performance functions at different moments, and then the time-dependent reliability analysis considering the fuzzy failure criteria is implemented for the concrete slab. The case study of the Houziyan CFRD shows that, during the initial period of water storage, the reliability index of the concrete slab decreases with the rise of the water level. With a stable water level, the probability of cracking of the concrete slab slowly decreases as the deformation of the dam body and slab tend to be coordinated. Especially, considering the fuzziness of the failure criteria, the reliability index decreased by about 2%, indicating that the proposed evaluation method is biased toward safety. The method proposed in this paper can reflect the evolution law of concrete slab reliability with the operating environment and provides a new approach to evaluate the performance of the concrete slab during the water storage period.

Performance of Pile–Wall System Adjacent to Footings

The performance of a retaining wall is dependent on multiple factors including lateral earth pressure, which results from backfill soils and adjacent footings located behind a retaining wall. The prediction of a retaining wall’s performance in a footing–soil–wall system (FSPS) must incorporate the influences caused by the movement of a retaining wall. This study examines the performance of a retaining wall formed by driven, precast, concrete piles located adjacent to a concrete footing using two- and three-dimensional finite element analysis (2D and 3D FEA) by ANSYS 13.0 software. Both soil and concrete are assumed to behave as non-linear, elastic-perfectly plastic and rate-independent materials in compliance with the upper-bound model of Drucker–Prager yield criterion. Three backfill and foundation soils are considered: kaolin, silty clay, and kaolin–sand. Various conditions of soil type, footing shape ratio, pile width, and footing–pile distance through 180 FEA runs are investigated. The effects of 2D and 3D FEA on the behavior of the pile–wall system are compared. The lateral deflection and pressure distribution profiles along the pile–wall are studied and presented. Two empirical equations predicting lateral deflections at the pile toe and pile head and useful for pile structural design are developed under the ultimate pressure of the adjacent footing.

Propagation of a viscous gravity current beneath a granular mush

The two-dimensional gravity-driven motion of a relatively dense viscous liquid at the base of a granular mush is investigated using a model that exploits the relative shallowness of the flow. The granular mush obeys a $\mu (I)$ -rheology, and we assume that the two phases are segregated throughout the motion. The viscous liquid spreads under gravity, carrying the granular mush above and transporting it outwards as levees at either end of the flow. The accumulation of granular material away from the centre of the deposit produces hydrostatic pressure gradients that retard the viscous gravity current. At later times, the granular mush is quasi-static relative to the moving liquid owing to the balance of outward granular transfer by the liquid and inward hydrostatic pressure gradients associated with the granular free surface. The viscous liquid exhibits a Poiseuille-like flow structure with negligible velocity at both the base and the granular interface. The flow of a fixed volume of viscous liquid becomes self-similar with the effective viscosity quadrupled relative to a classical viscous gravity current owing to the retarding effects of the granular mush. The case of constant input flux of viscous liquid is also analysed. The qualitative features are akin to the fixed volume case with the granular mush forming levees and slowing the viscous spreading. The case in which the upper medium is a Bingham material rather than a granular mush is also discussed, and the same features are observed, demonstrating the importance of the yield criterion in the upper medium.

Studies of Molecular Marker in Sunflower (Helianthus annus L.)

Helianthus annus L., known as sunflower, is belong to Asteraceae family. This family is one of the biggest angiosperm plant families in between dicotyledons and cultivated sunflower is an important oil plant all around the world. Chloroplast DNA analysis reveals that the origin of the genus dates back to 4.75 to 22.7 million years ago. Sunflower seeds contain 18% protein, 15% cellulose, 9% water, 14% minerals and carbohydrates. In general, sunflower seeds contain 35% to 50% oil by weight. The oil content of sunflower had been specified from 36.9% to 50.2%. These features have made sunflower an important plant worldwide. In principle, the breeding of sunflowers aims to improve the oil content and to get a plant resistant to disease. All breeding methods both classical and biotechnological methods try to contribute these aims. With the help of technology DNA markers have provided useful information about polymorphism, genetic relatedness, and diversity. Technology advances in breeding, especially the use of molecular markers, offer new strategies to obtain high-yielding and resistant plants through DNA sequences located at a known location on the chromosome. Sunflower has been a model plant in Asteraceae family in molecular marker studies because of its economic importance. Many molecular marker studies have been conducted against biotic and abiotic stress conditions, increase oil content and nutritional value, and water consumption etc. Considering its economic value, current studies on the plant will shed light on future studies and improvements can be observed in many yield criteria such as water consumption, harvest efficiency, resistance to pests.

Expansion of a spherical cavity in an infinite porous rigid/plastic medium

An expanding spherical cavity of a zero initial radius surrounded by an infinite porous rigid/plastic medium is considered. The material is assumed to obey the flow theory of plasticity based on a yield criterion and its associated flow rule. The yield criterion depends on the linear and quadratic stress invariants. No restriction is imposed on this dependence, except for the standard requirements imposed on the yield criteria. It is shown that the solution can be extended into the rigid region. The yield criterion approaches the von Mises yield criterion as the relative density approaches unity. Some equations contain the expression 0/0 at the rigid/plastic boundary. In this respect, the present solution is qualitatively different from available elastic/plastic solutions. However, the solution does not provide the solution for the von Mises yield criterion as a particular case. Numerical results are presented for Green’s yield criterion. These results follow physical expectations concerning the distributions of the relative density, the radial velocity, and the radial stress. The solution is adapted for expanding a cavity of a non-zero initial radius. The pressure required for expanding the cavity is calculated.