Browsing by Author "Belinha, Jorge"
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- 3D printed devices to avoid hand contact with commonly shared surfacesPublication . Pais, A.; Ferreira, C.; Pires, V.; Silva, V.; Alves, J. Lino; Bastos, João; Belinha, JorgeIn the context of the COVID-19 pandemic, public spaces had to be quickly adapted to the new circumstances especially under the uncertainty of the pandemic development. Door handles are some of the most touched surfaces and so, this point of contagion was chosen to be tackled and two solutions were developed that would prevent direct touch with the handle: a portable and a fixed device. The portable device (HYHOOK + HYTIP) is a hook-like device holding a finger cover, which permits to open doors and push buttons safely. The fixed device (HANDGENIC) is meant to be assembled in door handles to equip buildings, such as universities or schools. With the fixed device, the user can open the door using their forearm which makes them less likely to transfer any particles to eyes, nose or mouth. The 3D printing Fused Filament Fabrication (FFF) process was selected as manufacturing technique, which allows the fast production of prototypes. This work portrays the development process and design iterations taking into consideration the concerns about the functioning of the devices and possible failures or alternative uses. To assure structural integrity of the parts, finite element (FE) analysis was used to verify its mechanical response. As conclusion, it was found that FE analysis indicate that the devices are structurally sound to be used in public spaces and that 3D printing is a useful way to rapidly develop devices while testing several design possibilities.
- An alternative 3D numerical method to study the biomechanical behaviour of the human inner ear semicircular canalPublication . Santos, Carla F; Belinha, Jorge; Gentil, Fernanda; Parente, Marco; Jorge, Renato NThe vestibular system is the part of the inner ear responsible for balance. Vertigo and dizziness are generally caused by vestibular disorders and are very common symptoms in people over 60 years old. One of the most efficient treatments at the moment is vestibular rehabilitation, permitting to improve the symptoms. However, this rehabilitation therapy is a highly empirical process, which needs to be enhanced and better understood.
- An evolutionary structural optimization algorithm for the analysis of light automobile parts using a meshless techniquePublication . Gonçalves, Diogo; Lopes, Joel; Campilho, Raul; Belinha, JorgePurpose The purpose of the present work is to develop the combination of the radial point interpolation method (RPIM) with a bi-directional evolutionary structural optimization (BESO) algorithm and extend it to the analysis of benchmark examples and automotive industry applications. Design/methodology/approach A BESO algorithm capable of detecting variations in the stress level of the structure, and thus respond to those changes by reinforcing the solid material, is developed. A meshless method, the RPIM, is used to iteratively obtain the stress field. The obtained optimal topologies are then recreated and numerically analyzed to validate its proficiency. Findings The proposed algorithm is capable to achieve accurate benchmark material distributions. Implementation of the BESO algorithm combined with the RPIM allows developing innovative lightweight automotive structures with increased performance. Research limitations/implications Computational cost of the topology optimization analysis is constrained by the nodal density discretizing the problem domain. Topology optimization solutions are usually complex, whereby they must be fabricated by additive manufacturing techniques and experimentally validated. Practical implications In automotive industry, fuel consumption, carbon emissions and vehicle performance is influenced by structure weight. Therefore, implementation of accurate topology optimization algorithms to design lightweight (cost-efficient) components will be an asset in industry. Originality/value Meshless methods applications in topology optimization are not as widespread as the finite element method (FEM). Therefore, this work enhances the state-of-the-art of meshless methods and demonstrates the suitability of the RPIM to solve topology optimization problems. Innovative lightweight automotive structures are developed using the proposed methodology.
- Analysis of stress singularity in adhesive joints using meshless methodsPublication . Ramalho, L.D.C.; Dionísio, J.M.M.; Sánchez-Arce, I.J.; Campilho, R.D.S.G.; Belinha, JorgeRecent years saw a rise in the application of bonding techniques in the engineering industry. This fact is due to the various advantages of this technique when compared to traditional joining methods, such as riveting or bolting. The growth of bonding methods demands faster and more powerful tools to analyze the behavior of products. For that reason, adhesive joints have been the subject of intensive investigation over the past few years. Recently, a fracture mechanics based approach emerged with great potential to evaluate joint behavior, called Intesity of Singular Stress Fields (ISSF), similar to the Stress Intensity Factor (SIF) concept. However, it allows the study of multi-material corners and does not require an initial crack. This approach was not yet tested with meshless methods. The present work intends to fill this gap, resorting to the Radial Point Interpolation Method (RPIM). With this purpose, adhesive joints with four different overlap lengths (LO) bonded with a brittle adhesive were studied. The interface corner's stresses were also evaluated. The predicted strengths were compared with the experimental data to assess the accuracy of the applied methods. In conclusion, the ISSF criterion proved to be applicable to meshless methods, namely the RPIM.
- A bio-inspired remodelling algorithm combined with a natural neighbour meshless method to obtain optimized functionally graded materialsPublication . Pais, A.I.; Alves, J.L.; Belinha, JorgeRecent developments suggest the use of triply periodic minimal surfaces (such as the gyroid) as a possibility for bone tissue scaffold. Moreover, through functional gradients of cellular structures, the mechanical properties can be edited and enhanced to achieve the most efficient results. One of the main concerns when designing bone scaffold is avoiding stress shielding, which occurs when the Young’s modulus of the implant is higher than the Young’s modulus of the bone it is replacing. If so, bone decay occurs in the surrounding tissue. While the literature possesses some approaches exploring functional gradients of material density, there are no solutions based on bone tissue phenomenological laws. Thus, the gyroid infill obtained with PLA (𝐸 = 3145 MPa) was characterized with mechanical tests, namely tensile and compression, and the obtained model was implemented in a bone remodelling algorithm. Using the natural neighbour radial point interpolation method (NNRPIM) it was found that similar bone density distributions were obtained for the gyroid infill and for bone tissue when subject to the same boundary conditions. Finally, the gyroid mechanical behaviour was extrapolated to other materials and it was concluded that similar properties can be obtained for bone tissue and titanium alloy (𝐸 = 110 GPa) scaffold.
- Biomechanical study of the vestibular system of the inner ear using a numerical methodPublication . Santos, Carla F.; Belinha, Jorge; Gentil, Fernanda; Parente, Marco; Areias, Bruno; Jorge, Renato NatalThe inner ear has two main parts, the cochlea, dedicated to hearing, and the vestibular system, dedicated to balance. Dizziness and vertigo are the main symptoms related to vestibular disorders, which commonly affects older people. In order to eliminate these symptoms a vestibular rehabilitation is performed; this consists in a range of movements of the head, known as maneuvers, performed by a clinical professional. This procedure does not always work as expected. The aim of this work is to contribute to a better understanding on how the vestibular system works. This knowledge will help in the development of new techniques that will facilitate a more efficient rehabilitation. In order to achieve that goal, a three-dimensional numerical model of the vestibular system, containing the fluids which promote the body balance, was constructed. The vestibular components will be discretized using the finite element method and the fluid flow will be analyzed using the Smoothed Particle Hydrodynamics The results obtained with the numerical model of the semicircular canal built to study the rehabilitation process are presented and compared with other authors. The solution achieved is similar with literature.
- Biomechanics of the vestibular system: a numerical simulationPublication . Santos, Carla F.; Belinha, Jorge; Gentil, Fernanda; Parente, Marco; Jorge, Renato M. NatalThe vestibular system is located in the posterior portion of the inner ear. It is a key component to our sense of balance and movement. Any changes in this system can cause effects or symptoms such as dizziness, blurred vision, imbalance, and nausea, which are vertiginous syndrome indicators. Vertigo is reported as one of the most common symptoms in the world. It is considered the third most frequent complaint in medicine, transmitting a sense of inadequacy and insecurity. The aim of this work is to contribute to a better understanding of how the vestibular system works. This knowledge will help in the development of new techniques that will facilitate a more effective rehabilitation. Vestibular rehabilitation consists of a set of exercises, known as maneuvers, which can reduce and even eliminate symptoms of dizziness and imbalance associated with a vestibular disorder. In this work, a three-dimensional computational model of the vestibular system, containing the fluids promoting the body balance, will be presented. The smoothed-particle hydrodynamics (SPH) method will be used to simulate the fluid behavior. The results provide a better comprehension of the biomechanics of the vestibular system, which contribute to recover from any system disorders.
- A computational framework to simulate the endolymph flow due to vestibular rehabilitation maneuvers assessed from accelerometer dataPublication . Santos, Carla F.; Belinha, Jorge; Gentil, Fernanda; Parente, Marco; Areias, Bruno; Jorge, Renato NatalVertiginous symptoms are one of the most common symptoms in the world, therefore investing in new ways and therapies to avoid the sense of insecurity during the vertigo episodes is of great interest. The classical maneuvers used during vestibular rehabilitation consist in moving the head in specific ways, but it is not fully understood why those steps solve the problem. To better understand this mechanism, a three-dimensional computational model of the semicircular ducts of the inner ear was built using the finite element method, with the simulation of the fluid flow being obtained using particle methods. To simulate the exact movements performed during rehabilitation, data from an accelerometer were used as input for the boundary conditions in the model. It is shown that the developed model responds to the input data as expected, and the results successfully show the fluid flow of the endolymph behaving coherently as a function of accelerometer data. Numerical results at specific time steps are compared with the corresponding head movement, and both particle velocity and position follow the pattern that would be expected, confirming that the model is working as expected. The vestibular model built is an important starting point to simulate the classical maneuvers of the vestibular rehabilitation allowing to understand what happens in the endolymph during the rehabilitation process, which ultimately may be used to improve the maneuvers and the quality of life of patients suffering from vertigo.
- Computational simulation of cellular proliferation using a meshless methodPublication . Barbosa, M.I.A.; Belinha, Jorge; Jorge, R.M. Natal; Carvalho, A.X.Background and objective: During cell proliferation, cells grow and divide in order to obtain two new genetically identical cells. Understanding this process is crucial to comprehend other biological processes. Computational models and algorithms have emerged to study this process and several examples can be found in the literature. The objective of this work was to develop a new computational model capable of simulating cell proliferation. This model was developed using the Radial Point Interpolation Method, a meshless method that, to the knowledge of the authors, was never used to solve this type of problem. Since the efficiency of the model strongly depends on the efficiency of the meshless method itself, the optimal numbers of integration points per integration cell and of nodes for each influence-domain were investigated. Irregular nodal meshes were also used to study their influence on the algorithm. Methods: For the first time, an iterative discrete model solved by the Radial Point Interpolation Method based on the Galerkin weak form was used to establish the system of equations from the reactiondiffusion integro-differential equations, following a new phenomenological law proposed by the authors that describes the growth of a cell over time while dependant on oxygen and glucose availability. The discretization flexibility of the meshless method allows to explicitly follow the geometric changes of the cell until the division phase. Results: It was found that an integration scheme of 6 × 6 per integration cell and influence-domains with only seven nodes allows to predict the cellular growth and division with the best balance between the relative error and the computing cost. Also, it was observed that using irregular meshes do not influence the solution. Conclusions: Even in a preliminary phase, the obtained results are promising, indicating that the algorithm might be a potential tool to study cell proliferation since it can predict cellular growth and division. Moreover, the Radial Point Interpolation Method seems to be a suitable method to study this type of process, even when irregular meshes are used. However, to optimize the algorithm
- Computational simulation of the cupula behavior in vestibular pathologies of the inner earPublication . Santos, Carla; Gentil, Fernanda; Parente, Marco; Areias, Bruno; Belinha, Jorge; Natal Jorge, RenatoVertigo is reported as one of the most common symptoms in the world, commonly related with vestibular disorders. It is considered the third most frequent complaint in medicine, transmitting a sense of inadequacy and insecurity, mainly in elders. The aim of this work is to contribute to a better understanding on how the vestibular system works, mainly during vestibular rehabilitation process. This knowledge will help in the development of new techniques that will facilitate a more efficient rehabilitation. Vestibular rehabilitation consists in a set of exercises, known as maneuvers, that can reduce and even eliminate the symptoms of dizziness and imbalance associated with a vestibular disorder.
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