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Dinis L.M.J.S.,University of Porto | Jorge R.M.N.,University of Porto | Belinha J.,Institute of Mechanical Engineering
Computers and Structures | Year: 2011

The Natural Neighbour Radial Point Interpolation Method (NNRPIM), an improved meshless method, is used in the numerical implementation of an Unconstrained Third-Order Plate Theory applied to laminates. The nodal connectivity and the node dependent integration background mesh are constructed resorting to the Voronoï tessellation and to the Delaunay triangulation. Within NNRPIM the obtained interpolation functions, constructed with the Radial Point Interpolators, pass through all nodes inside the influence-cell providing the interpolation functions with the delta Kronecker property. In order to prove the high accuracy and convergence rate of the proposed meshless method several well-known benchmark static and dynamic laminate examples are solved. The numerical results obtained with the NNRPIM are compared with the Unconstrained Third-Order Plate Theory exact solution, when available, and with exact solutions of other plate deformation theories. © 2010 Civil-Comp Ltd and Elsevier Ltd. All rights reserved. Source


Belinha J.,Institute of Mechanical Engineering | Dinis L.M.J.S.,University of Porto | Natal Jorge R.M.,University of Porto
International Journal for Numerical Methods in Engineering | Year: 2013

SUMMARY: In this work an innovative numerical approach is proposed, which combines the simplicity of low-order finite elements connectivity with the geometric flexibility of meshless methods. The natural neighbour concept is applied to enforce the nodal connectivity. Resorting to the Delaunay triangulation a background integration mesh is constructed, completely dependent on the nodal mesh. The nodal connectivity is imposed through nodal sets with reduce size, reducing significantly the test function construction cost. The interpolations functions, constructed using Euclidian norms, are easily obtained. To prove the good behaviour of the proposed interpolation function several data-fitting examples and first-order partial differential equations are solved. The proposed numerical method is also extended to the elastostatic analysis, where classic solid mechanics benchmark examples are solved. © 2013 John Wiley & Sons, Ltd. Source


Belinha J.,Institute of Mechanical Engineering | Jorge R.M.N.,University of Porto | Dinis L.M.J.S.,University of Porto
Computer Methods in Biomechanics and Biomedical Engineering | Year: 2013

In this work, a novel anisotropic material law for the mechanical behaviour of the bone tissue is proposed. This new law, based on experimental data, permits to correlate the bone apparent density with the obtained level of stress. Combined with the proposed material law, a biomechanical model for predicting bone density distribution was developed, based on the assumption that the bone structure is a gradually self-optimising anisotropic biological material that maximises its own structural stiffness. The strain and the stress field required in the iterative remodelling process are obtained by means of an accurate meshless method, the Natural Neighbour Radial Point Interpolation Method (NNRPIM). Comparing with other numerical approaches, the inclusion of the NNRPIM presents numerous advantages such as the high accuracy and the smoother stress and strain field distribution. The natural neighbour concept permits to impose organically the nodal connectivity and facilitates the analysis of convex boundaries and extremely irregular meshes. The viability and efficiency of the model were tested on several trabecular benchmark patch examples. The results show that the pattern of the local bone apparent density distribution and the anisotropic bone behaviour predicted by the model for the microscale analysis are in good agreement with the expected structural architecture and bone apparent density distribution. © 2013 © 2013 Taylor & Francis. Source


Zhu Y.,Institute of Mechanical Engineering
Jixie Qiangdu/Journal of Mechanical Strength | Year: 2016

Diagnosis and resolution faults of gas bearing turbo-expander influences the operation of refrigeration system. Through the analysis of the structure of gas bearing turbo-expander is of great importance for fault diagnosis. Crashes, caused by the rotor imbalance, was eliminated by static balance and dynamic balance test, when gas bearing turbo-expander was started and run, it should be regulated not to overspeed to ensure that rotor were not overloaded. The reason of gas bearing stability was analyzed, caused by the radial load and frequent start-stop and flash power outage. The relationship between gas supply pressure, radial clearance and the rotor balance was analyzed. Clearance, between the machine shell and wheel, could be adjusted to avoid the increase of the internal leakage. Measures was adopt to reduce external leaks, such as adjusting the sealing gap at the back of the wheel and providing plenty of sealing gas. The causes of liquid impact fault was analyzed, and processing method was put forward. Failures caused by gas pipeline jam and unclean bearing gas were analyzed. Methods are proposed to ensure safe and stable operation of the turbo-expander gas bearing, such as rigorous test of dynamic and static balance, the correct assembly, standardized operation, and regular maintenance. © 2016, Journal of Mechanical Strength. All right reserved. Source


Belinha J.,Institute of Mechanical Engineering | Dinis L.M.J.S.,University of Porto | Natal Jorge R.M.,University of Porto
International Journal of Mechanical Sciences | Year: 2013

An innovative numerical approach, combining the simplicity of low-order finite elements connectivity with the geometric flexibility of Meshless methods, is extended to the elastostatic analysis of thick plates. The nodal connectivity is enforced using the natural neighbour mathematical concept and the background integration mesh is constructed uniquely depending on the nodal mesh. The nodal connectivity is imposed through nodal sets with reduced size, reducing significantly the test function construction cost. The interpolation functions are constructed using Euclidean norms and easily obtained. It is considered as the Reissner-Mindlin plate shear deformation theory. Several thick plate elastostatic benchmark examples are solved. © 2013 Elsevier Ltd. Source

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