A Strain Components-Based Mohr–Coulomb Fracture Criterion for Proportional Loadings
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Ductile fracture criteria are essential when using elastoplastic materials such as advanced high strength steels (AHSS) that fail without severe localized necking. It is aimed to figure out the unified mechanism for ductile fracture and accurately describe it with phenomenological criteria. In this paper, the effect of the stress triaxiality and the Lode parameter is analyzed mathematically. The maximum shear strain and the normal strain to fracture are emphasized in the proposed strain components-based Mohr–Coulomb fracture criterion based on the fracture surface observations, and it is assumed that fracture occurs when the linear combination of the maximum shear strain and the normal strain reaches the critical value. It is then extended to describe fracture with the equivalent plastic strain and the normal strain to fracture. The experimental fracture data of AA 2024-T351 and the additively manufactured Ti-6Al-4V titanium alloy are used to verify the proposed models. A fracture forming limit diagram comprising forming limit curves calibrated from stress states under different stress triaxialities is proposed based on the proposed criteria. The study shows that a strong correlation between the maximum shear strain and the normal strain to fracture has been observed, and it can be described piecewise-linearly by the proposed strain components-based Mohr–Coulomb criteria. The proposed fracture forming limit diagram includes both the effect of the stress triaxiality and the Lode parameter and can assess the risk of failure properly. The results provide a new insight into the intrinsic deformation and fracture mechanism of materials that fail without severe localized necking.Keywords:
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Mohr–Coulomb theory
This work presents test and finite element analysis results for a steel buckling-restrained braced frame(BRBF).The objectives are to evaluate the forces of frame and brace actions on the corner gusset plate and to develop a method that considers both action forces in design.In the cyclic test of the frame,the BRBF subassembly exhibited excellent performance up to an interstory drift of 2% with a maximum axial strain of 1.7% in the proposed buckling-restrained brace(BRB).Neither BRB nor corner gusset plate buckled during the frame test.By idealizing the corner gusset plate as a strut,a strut model can be used to determine forces resulting from the frame action,which are the same order as brace forces.Considering stress distributions and force components from the frame and brace actions,maximum stresses in gusset tips are used as an additional design parameter for sizing a gusset plate and stiffeners to reach maximum compression capacity of the BRB.
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Abstract An analytical solution is presented for the stress and strain fields in a Mohr–Coulomb material in plane strain around a circular hole when it is compressed by an axisymmetric far‐field pressure. It is shown that several solutions arise involving one to three plastic zones depending on the values of Poisson's ratio and the friction angle. The solution chosen for presentation was obtained and used to validate the functioning of the Mohr–Coulomb yield condition that was added to the NONSAP finite element code. Stress and strain field comparisons are made.
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Due to the conventional Mohr-Coulomb criterion used for geotechnical materials with its limitation for overestimation of tensile performance,a modified Mohr-Coulomb model is established considering maximal tensile stress criterion.The main contents of the implicit constitutive integration algorithm are discussed systematically;and the consistent stiffness matrix is deduced.Based on the implicit Euler stress integration algorithm,the UMAT subroutine of the modified Mohr-Coulomb model is developed in ABAQUS.With the new developed model,the numerical simulation of uniaxial tensile test and triaxial compression test is implemented respectively.The study shows that the developed modified Mohr-Coulomb UMAT subroutine could effectively depict the tensile performance of geotechnical materials and fill up the deficiency of the Mohr-Coulomb model in ABAQUS.
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Duroc and Strain A were used for the terminated paternity and formed 8 crossing combinations with (L×Y),(Y×L),(strain B×strain C), (Y×strain C) which were used for female line respectively. Fattening test living weight 20～90 kg, slaughter determination and analysis of carcass qualities showed daily gain of Duroc ×(L×Y) combination is the highest (704 g) during fattening periods, and it was more higher than Duroc×(strain B×strain C), strain A×(L×Y) and strain A×(Y×strain C). Moreover, it showed very significant difference with strain A×(Y×strain C). The mixium of feed to gain ratio combination is strain A×(L×Y). combination D×(L×Y) and Duroc×(Y×strain C) were determined preliminarily to be desired patter of three-way crosses according to comparing meal quality of better fattening performance combination.
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This paper discusses the effect of Mohr-Coulomb's parameters on the analysis results of concrete-like material failure behavior using the Distinct Element Method. The failure behavior of plane concrete which is model by the particle elements arranged in a couple of plane which are stood parallel on a horizontal plane is analyzed under several constitutive law conditions. Two types Mohr-Coulomb condition are used, and various cohesion parameter and friction angles are combined in some simulation condition. It is pointed out that 5 types failure modes appear in global viewpoint depending on the Mohr-Coulomb condition.
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To solve the classical problem that the Mohr–Coulomb yield criterion overestimates the tensile properties of geotechnical materials, a modified Mohr–Coulomb yield criterion that includes both maximum tensile stress theory and smooth processing was established herein. The modified Mohr–Coulomb constitutive model is developed using the user‐defined material subroutine (UMAT) available in finite element software ABAQUS, and the modified Mohr–Coulomb yield criterion is applied to construct a numerical simulation of a shaking table model test. Compared with the measured data from the shaking table test, the accuracies of the classical Mohr–Coulomb yield criterion and the modified Mohr–Coulomb yield criterion are assessed. Compared to the shaking table test, the classical Mohr–Coulomb model has a relatively large average error (−6.98% in peak acceleration values, −8.47% in displacement values, −23.93% in axial forces), while the modified Mohr–Coulomb model has a smaller average error (+2.71% in peak accelerations value, +3.19% in displacements value, +7.56% in axial forces). The results of numerical simulation using the modified Mohr–Coulomb yield criterion are closer to the measured data.
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The genus Sediminibacterium comprises species present in diverse natural and engineered environments. Here, we report for the first time the genome sequences of the type strain Sediminibacterium salmoneum NJ-44 (NBRC 103935) and Sediminibacterium sp. strain C3 (BNM541), isolated from activated sludge, a valuable model for the study of substrate-dependent autoaggregation.
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The bearing capacity of clayey soils is low, and the induced settlements play an important role in estimating the stability of structures built on these weak soils. Therefore, these clayey soils need improved mechanical strength. In this study, a two-dimensional finite element model was used to improve the bearing capacity and settlement of soft clay soil by employing skirt sand piles, and the results were compared with reinforced cement piles. Skirt sand piles consisting of thick sand cores and closed tubes placed under a circular shallow foundation with a steel plate of suitable dimensions, as well as reinforced cement piles of different lengths and in nondrained situations were studied. These calculations were carried out using PLAXIS 2D software, and a series of finite element analyses were performed. The Mohr‒Coulomb and hardening soil models were used to model the fine-grained and granular soils, respectively. A linear elastic model was used to simulate the circular plate and skirt components. Previous experimental studies were used to validate the numerical model. The experimental test and the 2D axisymmetric model agree well. According to the assumptions, the efficiency of skirt sand piles is superior to that of deep cement piles. In addition, increasing the length of SSP skirt sand piles has a significantly greater effect on improving the bearing capacity than increasing the length of deep cement piles. As a consequence, the failure modes of piles with skirt sand were determined. It was found that the failure mode when skirt sand piles were tied into clayey soils occurred in the underlying sandy soil layer as a general shear failure.
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The experimental data showed that the morphological variation of the culture of strain 243 of Streptomyces levoris, Krass, producing telavimycin (antibiotic 243) resulted in the formation of three morphological types differing in some features from the initial culture. Cultures of the type I and II colonies were most promising for selection. Strains producing higher yields of the antibiotic as compared to the initial strain 243 were selected from these cultures. After exposure of the spores of strain 243-96 to UV light in a dose of 500 erg/mm2 a highly productive strain 243-197 was isolated. The activity of this strain is 51 per cent higher than that of strain 243-96.
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The application of nitrogen ion beam injection technique in the mutation of high-yielding validamycin-producing strain was explored.After injecting 15×1013 nitrogen ions per metric centimeter with the intensity of 10 keV into validamycin-producing strain for mutation,the regenerated single-colonies were inoculated in shake flasks for the selecting of high-yielding strains.A mutative strain 9275# was obtained,the content of effective component A in strain 9275# was 33.52% higher than that in the original strain,and 9275# had high genetic stability.
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