Previous research conducted using a compaction profile sensor and a standard cone penetrometer over a wide range of soil types and conditions found that the unit pressure acting on the cutting edge, defined as the con...
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Previous research conducted using a compaction profile sensor and a standard cone penetrometer over a wide range of soil types and conditions found that the unit pressure acting on the cutting edge, defined as the cone index equivalent (CIE), at a specific depth (d) was related to the cone index (CI) value at that depth, the depth of the cutting edge (d), and the interaction between CI and the depth of the cutting edge (i.e., CI. d) with a very high coefficient of multiple determination irrespective of the soil type and conditions. The objective of this study was to provide an analytical basis for the relationship between CIE and CI. A two-dimensional axisymmetric model for soil-cone interaction and a three-dimensional model for soil-tine interaction were developed using a finiteelement method (FEM). A non-linear elasto-plastic constitutive behavior along with the Drucker-Prager yield criterion were used to represent the soil cutting process. Simulations studies were conducted in 25 distinct soil types and conditions, and the results indicated a similar relationship between CIE and CI, as observed in the previous research. These results support the existence of a strong theoretical basis for the empirical relationship observed in the previous research.
High-speed machining (HSM) may produce parts at high production rates with substantially higher fatigue strengths and increased subsurface micro-hardness and plastic deformation, mostly due to the ploughing of the rou...
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High-speed machining (HSM) may produce parts at high production rates with substantially higher fatigue strengths and increased subsurface micro-hardness and plastic deformation, mostly due to the ploughing of the round cutting tool edge associated with induced stresses, and can have far more superior surface properties than surfaces generated by grinding and polishing. Cutting edge roundness may induce stress and temperature fields on the machined subsurface and influence the finished surface properties, as well as tool life. In this paper, a finiteelement method (FEM) modeling approach with arbitrary Lagrangian Eulerian (ALE) fully coupled thermal-stress analysis is employed. In order to realistically simulate HSM using edge design tools, an FEM model for orthogonal cutting is designed, and solution techniques such as adaptive meshing and explicit dynamics are performed. A detailed friction modeling at the tool-chip and tool-work interfaces is also carried out. Work material flow around the round edge cutting tool is successfully simulated without implementing a chip separation criterion and without the use of a remeshing scheme. The FEM modeling of the stresses and the resultant surface properties induced by round edge cutting tools is performed for the HSM of AISI 4340 steel. Once FEM simulations are complete for different edge radii and depths of cut, the tool is unloaded and the stresses are relieved. Predicted stress fields are compared with experimentally measured residual stresses obtained from the literature. The results indicate that the round edge design tools influence the stress and temperature fields greatly. An optimization scheme can be developed to identify the most desirable edge design by using the finiteelement analysis (FEA) scheme presented in this work.
The present work aimed at predicting the strength of weld-bonded joints having square or spew fillet adhesive layer. For comparison purposes. adhesive bonded and resistance spot-welded joints were also included in thi...
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The present work aimed at predicting the strength of weld-bonded joints having square or spew fillet adhesive layer. For comparison purposes. adhesive bonded and resistance spot-welded joints were also included in this study. The present work demonstrated that, the major principal stress predicted in joints having spew fillet adhesive layer is lower than that predicted in joints having adhesive layer with square edges. Consequently, it is advised to use adhesive layer having spew fillet to strengthen weld-bonded joints. (C) 2002 Published by Elsevier Science B.V.
A new three-dimensional finite element modeling methodology for nonlinear analysis of reinforced concrete walls is developed and implemented in OpenSees software. The model is validated against broad experimental data...
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A new three-dimensional finite element modeling methodology for nonlinear analysis of reinforced concrete walls is developed and implemented in OpenSees software. The model is validated against broad experimental data obtained for nine planar (unidirectional loading) and two U-shaped (multidirectional loading) specimens. Results of the detailed validation studies presented indicate that the proposed model can accurately capture a wide range of measured global (e.g., load-deformation) and local (e.g., strains) wall responses. However, the model fails to capture the loss of wall lateral load capacity observed in experiments due to various complex failure mechanisms that are not incorporated in presented model formulation.
Recent works, both numerical and experimental, on residual stress and geometrical errors in selective laser melting-produced parts highlighted the preponderance of these phenomena. However, their mechanisms of appeara...
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Recent works, both numerical and experimental, on residual stress and geometrical errors in selective laser melting-produced parts highlighted the preponderance of these phenomena. However, their mechanisms of appearance are not yet fully explained. An in-house finiteelement model was developed and implemented to reproduce their formations. The consistence of the model with existing simulation results and with respect to experimental observations was checked. Simulations were then performed using a computational design of experiments to better comprehend the underlying phenomena and the influence of the laser speed and power. Relationships between process parameters and residual stress, plastic strain, and geometrical errors formations have been put into evidence which can support optimization procedures at design stage.
Ultrasonic surface rolling (USRP) is a newly developed process in which ultrasonic vibration and static force are applied on work-piece surface through the USRP operator to generate a nanostructured surface layer with...
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Ultrasonic surface rolling (USRP) is a newly developed process in which ultrasonic vibration and static force are applied on work-piece surface through the USRP operator to generate a nanostructured surface layer with mechanical behaviors highly improved. Compared with other surface severe plastic deformation (S-2 PD) methods, it can realize mechanized machining and be directly used for preparing final product. Notwithstanding the excellent performance of USRP, elaborate relation between process parameters and surface layer characteristics is still inadequacy due to inconvenient and costly experimental evaluation. Therefore, in this paper a three-dimensional finiteelement model (FEM) has been developed to predict the treatment conditions that lead to surface nanocrystallization. Simulated results of surface deformation, stress and strain are investigated to assess the formation of nanostructured layer. The numerical results from the FEM corresponds well with the values measured experimentally, indicating that this dynamic explicit FEM is a useful tool to predict the processing effects and to relate the treating parameters with the surface layer in terms of the size of nanostructured layer, residual stress and work hardening. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.
Developing a biomechanical model which connected with the actual anatomy of the human body is helpful to understand the human response to vibration. A finiteelement model of the seated human body with 175 cm in statu...
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Developing a biomechanical model which connected with the actual anatomy of the human body is helpful to understand the human response to vibration. A finiteelement model of the seated human body with 175 cm in stature and 68.6 kg in weight, which consists of seven segments, six joints and soft tissue, was established to reflect apparent mass based on the Hybrid III dummy model. By comparing the body segment mass percentages with previous data, the rationality of mass distribution in this model was verified. The biomechanical parameters play a crucial role in biodynamic modeling, while the joint and soft tissue parameters are difficult to choose due to the wide range of anthropometric parameters. In this study, the root-mean-square error between the calculated and the measured apparent mass was taken as objective function, and the effect of fifteen human parameters on the objective function was analyzed through sensitivity analysis. Then seven parameters with a considerable influence on the objective function were selected as design variables, and four approximate models were established for parameter optimization. Soft tissues and joint parameters of the model were determined by parameter identification, and the finiteelement model that can reflect vertical in-line and fore-and-aft cross-axis apparent mass of the human body without backrest was developed. The seated human model presented in this paper can also reflect the transmissibility from seat to the first thoracic spine and the main modes of the human body below 10 Hz, which is conducive to express the human response to vibration.
Carbonation is one of the many reasons of reinforcement corrosion in concrete structures. Due to the coupling effects of moisture, heat and carbon dioxide transport in concrete, the modeling of this problem is a rathe...
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Carbonation is one of the many reasons of reinforcement corrosion in concrete structures. Due to the coupling effects of moisture, heat and carbon dioxide transport in concrete, the modeling of this problem is a rather challenging task. A nonlinear finiteelement approach is adopted here for tracing the spatial and temporal advancement of the carbonation front in concrete structures with and without cracks. A two-dimensional Windows-based finiteelement computer program, called CONDUR, is developed and the results obtained from the program are compared with available experimental data. The program is designed to be flexible and comprehensive in its scope. (C) 2003 Elsevier Ltd. All rights reserved.
Considering microwave (MW) heating as a viable alternative for in-shell pasteurization of eggs, after the simulation of the MW heating process by using a finiteelement model, process optimization was carried out to d...
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Considering microwave (MW) heating as a viable alternative for in-shell pasteurization of eggs, after the simulation of the MW heating process by using a finiteelement model, process optimization was carried out to determine the most effective procedure and design for the process. The varying parameters obtained by using different modeling techniques for MW heating of in-shell eggs were optimized. Laboratory-scale experimental trials were conducted to test the validity and effectiveness of the optimized parameters. The optimal parameters set forth were found to be more efficient in terms of heating time and uniformity. MW heating appeared to be a viable alternative for the pasteurization of in-shell eggs. Copyright (C) 2011 John Wiley & Sons, Ltd.
Four dimensional (4D) textiles consist of a textile with a printed polymeric grid, where deformation of the grid is induced by introducing residual stresses in the textile, in this case through pre-stretching of the t...
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Four dimensional (4D) textiles consist of a textile with a printed polymeric grid, where deformation of the grid is induced by introducing residual stresses in the textile, in this case through pre-stretching of the textile substrate prior to printing. The fourth dimension refers to the ability of the structure to change shape over time by changing the residual stress in the textile. In order to design a useful component for a specific application, the material properties of constituents, direction and amount of residual stress, anisotropy of the textile substrate, geometry of the printed polymer, and pattern of the printed grid can all be altered. Due to the large amount of design variables involved, a validated modeling technique that can account for the complex material behavior of the soft, flexible textile under large strains and deformations along with the bifurcation and stability behavior of buckling beams is needed. In this study, an initial model was created to capture the time-independent buckling behavior and compared with experiments for rectangular elements of varying geometry and pre-strain. Once the model was calibrated, it fit experiments well, although additional advancements must be made to predict the nonlinear behavior of a wide variety of architectures with further accuracy. Finally, modeling strategies for large grids are laid out and discussed, and preliminary results are shown. Although this model did not include the transient nature of shape change, it can serve as a precursor for designing 4D Textiles and eventually predicting their time-dependent behavior under loading changes.
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