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Bo Guo - One of the best experts on this subject based on the ideXlab platform.

  • Modelling Hydraulic Fracturing with a Point-Based Approximation for the Maximum Principal Stress Criterion
    Rock Mechanics and Rock Engineering, 2019
    Co-Authors: Quansheng Liu, Lei Sun, Xuhai Tang, Bo Guo
    Abstract:

    Accurate simulation of the propagation of hydraulic fractures under in situ Stress conditions in three dimensions (3D) is critical for the enhanced design and optimization of hydraulic fracturing in various engineering applications, such as shale gas/oil production and geothermal utilization. To model fracture propagation for geotechnical applications numerically, a Maximum Principal Stress criterion (MPS-criterion) with a weighted average approximation is conventionally applied. However, it is found that the weighted average approximation is inappropriate for hydraulic fracturing under in situ Stress conditions, where the presence of both hydraulic pressure and in situ Stress can lead to sharp changes of the Stress field in the vicinity of the fracture tips. When both hydraulic pressure and in situ Stress are considered, the simulated results with the weighted average approximation are inaccurate and are sensitive to the radius of the computational area. In this paper, we present numerical tests to identify this limitation of the weighted average approximation and propose a novel point-based approximation for the MPS-criterion. The performance of the MPS-criterion with the point-based approximation for hydraulic fracturing under in situ Stress conditions is confirmed by a numerical test. It can be seen that, compared to the traditional weighted average approximation, the MPS-criterion with the point-based approximation is more stable and accurate for modelling hydraulic fracturing under in situ Stress conditions.

Toshiyuki Sawa - One of the best experts on this subject based on the ideXlab platform.

  • Three-dimensional finite element analysis of Stress response in adhesive butt joints subjected to impact bending moments
    Journal of Adhesion, 2020
    Co-Authors: Izumi Higuchi, Toshiyuki Sawa, Hirohisa Okuno, Shinya Kato
    Abstract:

    The Stress wave propagation and the Stress distribution in adhesive butt joints of T-shaped similar adherends subjected to impact bending moments are calculated using a three-dimensional finite-element method (FEM). An impact bending moment is applied to a joint by dropping a weight. The FEM code employed is DYNA3D. The effects of the Young's modulus of adherends, the adhesive thickness, and the web length of T-shaped adherends on the Stress wave propagation at the interfaces are examined. It is found that the highest Stress occurs at the interfaces. In the case of T-shaped adherends, it is seen that the Maximum Principal Stress at the interfaces increases as Young's modulus of the adherends increases. In the special case where the web length of T-shaped adherends equals the flange length, the Maximum Principal Stress at the interfaces increases as Young's modulus of the adherends decreases. The Maximum Principal Stress at the interfaces increases as the adherend thickness decreases. The characteristics o...

  • Three-dimensional finite element Stress analysis of single-lap adhesive joints of dissimilar adherends subjected to impact tensile loads
    Journal of Adhesion Science and Technology, 2020
    Co-Authors: Toshiyuki Sawa, Izumi Higuchi, Hidekazu Suga
    Abstract:

    The Stress-wave propagations and Stress distributions in single-lap joints of dissimilar adherends were analyzed using an elastic three-dimensional finite-element method (DYNA3D). An impact tensile load was applied to the single-lap adhesive joint by dropping a weight. One end of the upper adherend in the single-lap adhesive joint was fixed and the other adherend (lower adherend) which was connected to a bar was impacted by the weight. The effects of Young's modulus and the thickness of each adherend on the Stress wave propagations and Stress distributions at the interfaces were examined. It was found that the Maximum value of the Maximum Principal Stress occurred near the edge of the interface of the fixed adherend. The Maximum Principal Stress increased as Young's modulus of the fixed adherend increased. It was also observed that the Maximum Principal Stress increased as the fixed adherend thickness decreased. In addition, strain responses in the single-lap adhesive joints of dissimilar adherends subjec...

  • Three-dimensional FEM Stress analysis and strength prediction of scarf adhesive joints with similar adherends subjected to static tensile loadings
    International Journal of Adhesion and Adhesives, 2014
    Co-Authors: Hiroko Nakano, Yuya Omiya, Yasuhisa Sekiguchi, Toshiyuki Sawa
    Abstract:

    Abstract The interface Stress distributions in scarf adhesive joints with similar adherends under static tensile loadings were analyzed using two-dimensional and three-dimensional finite element calculations for the two cases where adhesive length and width of the adherends were held constant. The effects of adhesive Young׳s modulus, the scarf angle and the adhesive thickness on the interface Stress distributions were examined. In addition, the joint strength was predicted using the interface Stress distributions based on the Maximum Principal Stress theory and von Mises׳ Stress criterion. It was found that when the scarf angle was around 60°, the singular Stress at the edges of the interfaces was minimal in the 3-dimensional FEM calculations while the singular Stresses vanished at 52° in the 2-dimensional FEM calculations. The value of the normalized Maximum Principal Stress at the edges of the interfaces obtained from the 3-D FEM was larger than that from the 2-D FEM. It was found that the Maximum Principal Stress increased at the edge of the interfaces as the scarf angle decreased. In addition, the effect of the adherends where the width was held constant was demonstrated. Experiments to measure strain and joint strengths were carried out. The measured strains were in a fairly good agreement with those obtained from the 3-D FEM calculations. Also, the measured joint strengths were fairly consistent with the predicted results based on the Maximum Principal Stress theory. As a result, the Maximum joint strength was observed when the scarf angle was around 60°. The difference in the interface Stress distributions was demonstrated between the two cases.

  • Stress analysis and strength evaluation of scarf adhesive joints subjected to static tensile loadings
    International Journal of Adhesion and Adhesives, 2010
    Co-Authors: Dan He, Toshiyuki Sawa, Takeshi Iwamoto, Yuya Hirayama
    Abstract:

    Abstract The Stress distributions in scarf adhesive joints under static tensile loadings are analyzed using three-dimensional finite-element calculations. The effects of adhesive Young’s modulus, adhesive thickness and scarf angle in the adherend on the interface Stress distributions are examined. As the results, it is found that the Maximum value of the Maximum Principal Stress occurs at the edge of the interfaces. The differences in the interface Stress distributions between the 2-D and the 3-D FEM results are demonstrated. It is also observed from the 3-D FEM results that the Maximum value of the Maximum Principal Stress is the smallest when the scarf angle is around 60 degree, while it is around 52 degree in the 2-D FEM when the singular Stress at the edges vanishes. In addition, the joint strength is estimated using the interface Stress distribution obtained from the FEM calculations. For verification of the FEM calculations, experiments were carried out to measure the strengths and the strains in the joints under static tensile loadings using strain gauges. Fairly good agreements were observed between the 3-D FEM and the measured results for strains. Therefore, for the joint strength, the results remain conservative.

Krishnaswa Ravichandar - One of the best experts on this subject based on the ideXlab platform.

  • a cohesive zone model for fatigue crack growth in quasibrittle materials
    International Journal of Solids and Structures, 2001
    Co-Authors: B Yang, S Mall, Krishnaswa Ravichandar
    Abstract:

    Abstract A cohesive zone model for fatigue crack initiation and growth in quasibrittle materials is proposed in the present paper. While bulk material is modeled to be linearly elastic, the softening material in the cohesive zone and cracks are modeled to be internal singular surfaces in the elastic body. The interactions of the singular surfaces are described in a cohesive force law and a Coulomb-type friction law if in contact. The cohesive zone material is modeled to accumulate damage not only along the damage locus but also along an unloading path underneath it, enabling a simulation of fatigue damage and crack growth without the ad hoc imposition of a law of growth rate within the cohesive zone model. The Maximum Principal Stress criterion is used to advance a tip of the cohesive zone in the direction of the Maximum Principal Stress when it reaches the critical value of material strength. The physical crack tip is grown as a natural process of debonding of the cohesive zone under cyclic loading, which, in contrast, may be subcritical with energy dissipation less than the material toughness under static loading. The boundary value problem formulated for fatigue crack growth incorporating the cohesive zone model is nonlinear due to the history dependence of the cohesive zone, and is solved efficiently using the iterative single-domain dual-boundary-element method of successive over-relaxation. It is demonstrated through examples that the present model is capable of predicting fatigue crack initiation as well as growth in a unified way. It is also shown that the cohesive zone model is more advantageous and flexible in handling fatigue cracks under arbitrary loading than the classical singularity-based fracture mechanics approach.

Jian Meng - One of the best experts on this subject based on the ideXlab platform.

  • 3D Finite Element Analysis of High-Pressure Common Rail Diesel Engine Connecting Rod
    Advanced Materials Research, 2011
    Co-Authors: Bin Zheng, Jian Meng
    Abstract:

    In this paper, with the ANSYS, Stress distribution, safety factor and fatigue life cycle of high-pressure common rail diesel engine connecting rod were analyzed by using 3D finite element method. The results show that the position of Maximum Principal Stress is transition location of small end and connecting rod shank at Maximum compression condition. The value of Stress is 253.98 MPa in dangerous position. Safety factor is 2.67. The position of Maximum Principal Stress is medial surface of small end at Maximum stretch condition. The value of Stress is 87.199 MPa in dangerous position. The fatigue life cycle of connecting rod is 2.6812×108. Fatigue safety factor is 1.5264.

  • 3D Finite Element Analysis of Marine Diesel Engine Connecting Rod
    Advanced Materials Research, 2011
    Co-Authors: Bin Zheng, Jian Meng
    Abstract:

    In this paper, with the ANSYS, Stress distribution and safety factor of marine diesel engine connecting rod were analyzed by using 3D finite element method. The results show that the position of Maximum Principal Stress is transition location of small end and connecting rod shank at Maximum stretch condition. The value of Stress is 24.69 MPa in dangerous position. The position of Maximum Principal Stress is transition location of small end and connecting rod shank at Maximum stretch condition. The value of Stress is 198.65 MPa in dangerous position. Safety factor is 2.51.

Quansheng Liu - One of the best experts on this subject based on the ideXlab platform.

  • Modelling Hydraulic Fracturing with a Point-Based Approximation for the Maximum Principal Stress Criterion
    Rock Mechanics and Rock Engineering, 2019
    Co-Authors: Quansheng Liu, Lei Sun, Xuhai Tang, Bo Guo
    Abstract:

    Accurate simulation of the propagation of hydraulic fractures under in situ Stress conditions in three dimensions (3D) is critical for the enhanced design and optimization of hydraulic fracturing in various engineering applications, such as shale gas/oil production and geothermal utilization. To model fracture propagation for geotechnical applications numerically, a Maximum Principal Stress criterion (MPS-criterion) with a weighted average approximation is conventionally applied. However, it is found that the weighted average approximation is inappropriate for hydraulic fracturing under in situ Stress conditions, where the presence of both hydraulic pressure and in situ Stress can lead to sharp changes of the Stress field in the vicinity of the fracture tips. When both hydraulic pressure and in situ Stress are considered, the simulated results with the weighted average approximation are inaccurate and are sensitive to the radius of the computational area. In this paper, we present numerical tests to identify this limitation of the weighted average approximation and propose a novel point-based approximation for the MPS-criterion. The performance of the MPS-criterion with the point-based approximation for hydraulic fracturing under in situ Stress conditions is confirmed by a numerical test. It can be seen that, compared to the traditional weighted average approximation, the MPS-criterion with the point-based approximation is more stable and accurate for modelling hydraulic fracturing under in situ Stress conditions.