Computational Finite Elements

Introduction- FEM is a mathematical method in which the shape of complex geometric objects and their physical properties are computer-constructed. Physical interactions of the various components of the model can then be calculated in terms of stress and strain, detailed information which is difficult to obtain by any other experimental or analytical means due to the interaction of anatomical structures with the surrounding tissue. Aim- Comparison of biomechanical differences by FEM between labial and lingual orthodontic mechanotherapy involved in canine retraction. Material & Method - ANSYS software was preferred over others for the analysis. As ANSYS can import computer assisted designing (CAD) data and also enables to build geometry, in the current study, we have shown the simulated individual (sequential) canine retraction using the sliding (friction method) mechanics by an elastic component. Sliding mechanics was preferred over the closing loop mechanics (frictionless method) Re...

Despite the large number of abrasive waterjet machining (AWJM) models developed so far, there still has been confusion about the nature by which workpiece surfaces are eroded. It is believed that analysis of stresses generated at the AWJ cutting interafce could provide deeper insight to explain such an erosion behavior. This paper presents a stress analysis of AWJM using a nonlinear dynamic finite element (FE) code in order to explain the behaviour of the process. The main objective is to develop an erosion mechanism which would correctly describe the abrasive-material interaction. The new model considers both AWJ dynamic loading conditions and nonlinear material behavior. The results show that the workpiece material fails due to highly localized plastic deformation caused by compressive stresses, specially at the AWJ cutting interface. Also AWJM causes residual stresses to remain in the workpiece material after machining.

Introduction: Torque of the maxillary incisors is essential in esthetics and proper occlusion, while torque expression is influenced by many factors. The aim of this finite element study was to assess the relative effect of tooth morphology, bracket prescription, and bracket positioning on tooth displacement and developed stresses/strains after torque application. Methods: A three-dimensional upper right central incisor with its periodontal ligament (PDL) and alveolus was modelled. The tooth varied in the crown–root angle (CRA) between 156°, 170°, and 184°. An 0.018-inch slot discovery® (Dentaurum, Ispringen, Germany) bracket with a rectangular 0.018 × 0.025-inch β-titanium wire was modelled. Bracket torque prescription varied between 0°, 12°, and 22°, with bracket placement at the centre of the middle, gingival or incisal third of the crown. A total of 27 models were generated and a buccal root torque of 30° was applied. Afterwards, crown and apex displacement, strains in the PDL, and stresses in the bracket were calculated and analysed statistically. Results: The palatal crown displacement was significantly affected by bracket positioning (up to 94 per cent), while the buccal apex displacement was significantly affected by bracket prescription (up to 42 per cent) and bracket positioning (up to 23 per cent). Strains in the PDL were affected mainly by CRA (up to 54 per cent), followed by bracket positioning (up to 45 per cent). Finally, bracket prescription considerably affected the stresses in the bracket (up to 144 per cent). Limitations: These in silico results need to be validated in vivo before they can be clinically extrapolated. Conclusion: Tooth anatomy and the characteristics of the orthodontic appliance should be considered during torque application.

Numerical continuous finite element computations of a fluid flow modelling based on ensemble technique are presented herein. This ensemble algorithm is based on time relaxation. At each time step, it requires the storage of a single coefficient matrix with multiple right‐hands sides which corresponds to each ensemble member. Finite element convergence results for the time relaxation ensemble algorithm are presented and tested in a numerical experiment. This numerical experiment supports the theoretical finite element results. The time relaxation efficiency was shown in the second cavity benchmark problem.

Despite the large number of abrasive waterjet machining (AWJM) models developed so far, there still has been confusion about the nature by which workpiece surfaces are eroded. It is believed that analysis of stresses generated at the AWJ cutting interafce could provide deeper insight to explain such an erosion behavior. This paper presents a stress analysis of AWJM using a nonlinear dynamic finite element (FE) code in order to explain the behaviour of the process. The main objective is to develop an erosion mechanism which would correctly describe the abrasive-material interaction. The new model considers both AWJ dynamic loading conditions and nonlinear material behavior. The results show that the workpiece material fails due to highly localized plastic deformation caused by compressive stresses, specially at the AWJ cutting interface. Also AWJM causes residual stresses to remain in the workpiece material after machining.

Modeling of abrasive waterjet machining (AWJM) has been finding widespread interest for the past twenty years. Due to the complex interaction of several AWJM parameters, combined with the nonlinear dynamic high speed impact of several thousands of small abrasive particles on the workpiece surface, the mechanism of material removal has not yet been fully understood. The current paper presents an attempt to explain the mechanism of material removal in AWJ, as a result of abrasive particle impact through step by step tracing of the abrasive particle as it is interacting with the workpiece material. The new model considers the elastic-plastic behavior of the workpiece material. Also the non linear dynamic loading conditions which are characteristic feautres of AWJM are accounted for in the pesent study. The failure of the workpiece material is examined analytically, by means of a virtual finite element (FE) AWJ experiment, and experimentally, by means of scanning electron microscopy (SEM) and surface topographies. Stress results indicate that the workpiece material is subject to severe highly localized plastic deformation and as a result, small overlapping craters are generated. These craters are formed by high compressive stresses at the cutting interface. The finite element results indicate a good agreement with experimental results.

Understanding the exact nature of erosion of workpiece materials by abrasive waterjet machining (AWJM) is still confused, although it is important for successful modeling of this promising process. This paper presents a first attempt to model the AWJM process using the powerful tool of the finite element method (FEM) in order to explain the abrasive particle-workpiece interaction. Also the model predicts the behaviour of the process. The main objective is to develop an FE model which would enable to predict the depth of cut without any cutting experiments. The new model takes into account the precise representation of the constitutive behaviour of the workpiece material under AWJ dynamic loading conditions which was ignored in previous AWJM models in which the flow stress was represented by a constant value. Additionally, deformations, stresses and strains occurring in the workpiece material in the vicinity of the cutting interface as a result of the erosion impact by AWJ, could be obtained. In the present model, forces acting on the abrasive particle need not be initially determined, as in previous AWJM studies, as they are automatically calculated at each time step. The results show that the finite element method is a useful tool in predicting abrasive-material interaction and AWJ depth of cut.

Erosion of ductile materials by abrasive waterjet machining (AWJM) is still a complex phenomenon. This paper presents a first attempt to simulate the abrasive waterjet machining (AWJM) process using the finite element method (FEM) in order to determine the workpiece response in this erosive wear process. Additionally, deformations occurring in the workpiece material in the vicinity of the cutting interface as a result of the high speed AWJ impact could be obtained. The results indicate that the finite element method is a useful tool in the prediction of the AWJ deformations.

Although several theoretical and experimental models have been developed for abrasive waterjet machining #AWJM), the exact nature of
erosion is not yet understood. This paper presents an attempt to model AWJM using the ®nite element method #FEM) in order to explain the
abrasive particle±workpiece interaction process. Also, the model predicts the depth of deformation as a result of abrasive particle impact.
The main objective is to develop an FE model which would enable the prediction of the depth of cut without any cutting experiments. The
new model takes into account the precise representation of the constitutive behavior of the workpiece material under AWJ dynamic loading
conditions which was ignored in the previous AWJM models. In the present model, forces acting on the abrasive particle need not be
initially determined, as in previous AWJM studies, as they are automatically calculated at each time step. The results show that plastic
deformation is very localized. Finally, the present FE results are consistent with experimental results.