1,720,973 research outputs found
A formulation and comparison of different shell FE modeling techniques for fatigue life simulation of welded joints
Full text linkA FE shell model capable of representing a welded structure without any significantly error on its stiffness could be widely applied to dynamic problems in which the structural stress method (hot spot approach) is employed for fatigue analysis. The scope of the present work is to formulate a modeling technique capable of doing so. In order to accomplish it, a parametric optimization for simulating welded structures using shell elements is made, the design variables in the proposed formulation are defined as the weld leg length and thickness of the shell element representing the weld fillet. The main goal of the optimization was to find a range of thickness/leg length which would not change significantly the first natural frequencies, and still deliver results similar to the ones obtained by a solid model. Sequential linear programming optimizations are performed in a T-shaped structure, with constant section and different plate thicknesses and depths. Once the optimal parameters are found, two different modeling techniques are presented and compared with three well established methodologies presented in standards and the literature. The differences in the results are compared for first natural frequencies, total mass, hot spot stress and fatigue life
Optimized representation for overlapped welded components using shell FE along with the structural stress method
Full text linkThe structural stress method is widely applied to fatigue analysis of welded components. The literature contains several modeling techniques capable of representing such structures. However, these techniques can only approximate the stiffness of the structure. The scope of the present work is to propose an optimization-based modeling technique to represent overlapped welded components (lap joints). This technique employs optimal parameters in order to reproduce the stiffness of the real structure without any significant errors. The design variable is defined as the thickness of the shell finite element representing the weld fillet. Linear programming is employed to solve the optimization problem. The objective function is defined as the residual error of the first natural frequencies obtained by a shell finite element model compared with the ones obtained by a solid model. This kind of modeling technique could be directly applied to large/complex problems, where global/local analysis are performed for structural integrity verification and fatigue life simulation. Once, this optimized modeling technique is used, global/local analysis are no longer needed and a single shell FE model can be applied for all the structural analysis. After proposing an optimization-based modeling technique, its result with respect to the structural stress are compared with the ones obtained with other methodologies presented in the literature and the standards. Results concerning errors when representing the structure total mass and first natural frequencies are presented
Optimization of Shell Fe Modeling Parameters in the Simulation of Weld Fillets Using the Structural Stress Method
Full text linkThe scope of the present work consists of the optimal parameters evaluation for simulating welded structures using shell finite elements. The design variables in the proposed formulation were defined as the weld leg length and thickness of the shell element representing the weld fillet. The main goal of the optimizations was to find a range of thickness/leg length which would not change significantly the first natural frequencies, and still deliver results similar to the ones obtained using a solid model. This kind of model is widely applied to dynamic problems in which the structural stress method (hot-spot approach) is employed for fatigue analysis. Sequential linear programming were performed in T-shaped structures with different structural details (FAT class). The structures of study were represented with constant section, different plate thicknesses and depths. An interior point algorithm was employed in the parametric optimizations performed. Different modeling techniques are suggested for each FAT class tested. A comparison with three well established methodologies presented in standards and the literature is also exposed. The differences in the results are compared for first natural frequencies, total mass and hot spot stress
A Study on the Best Conventional Shapes for Composite Repair Patches
Full text linkAdhesively bonded repair patches are an excellent approach for repairing locally damaged composite components. If correctly applied, fiber-reinforced patches may restore/increment the mechanical response of damaged laminates without significantly increasing the structure's mass or altering its geometry. However, in order to take full advantage of this repairing technique, one must employ patches with a minimal surface area and maximum efficiency in incrementing the strength of the component. The present work aims to study optimum-based patch shapes for conventional repair geometries, namely rectangular and elliptical. Shell Finite Elements models were used to simulate a parent plate, which is a rectangular flat laminate with a central trespassing damage region. Unbalanced single-ply patches were modeled on the upper surface of the damaged laminate. The patches' efficiency was computed as its capability in restoring the modal response of the repaired component to its undamaged configuration. Sequential linear programming was employed alongside shell finite element models to obtain optimal geometrical parameters for the patches' shape. The study cases comported two different boundary conditions and two stacking sequences. The optimum-base repair patches were defined regarding size and fiber orientation angle
Optimal shape of repair patches in composites
Full text linkIn recent decades, the increase in demand for advanced composites in the replacement of conventional materials, to both primary and secondary aircraft components, reached a concerning level. The safety and efficiency of composite aircraft components are significantly dependent on damage assessment and repair techniques. In this scenario, the use of composite repair patches for restoring and/or improving the original strength and stiffness conditions of damaged components is a viable option. This statement is particularly true when replacing the entire damaged component is not cost-effective. The present work proposes an optimization-based methodology for obtaining the best patch configurations for the repair of damaged laminate panels. A two-phase optimization was employed: first, the fiber orientation that maximizes the strength of the repair patch was defined, followed by the minimization of the repair surface. Circular and square repair patch shapes were tested. The parent plate was considered as a rectangular plane laminate with two different stacking sequences, and different boundary conditions were tested as well. The patch was modeled as an unbalanced fiber reinforced repair with a single layer. Linear programming was employed to solve both optimization problems: fiber orientation and shape area. The error concerning the first natural frequencies of the repaired component compared to the damaged one was considered as the objective function
Studies on Shape Optimization of Repair Patches for Damaged Composites
Full text linkDue to the increasing development of health monitoring and damage detection techniques, the assessment of damage presence and its shape is a viable option to continuously evaluate the structural integrity of composite components. Along with such tool, one could employ repair patch techniques in order to restore (or locally improve) the originally designed strength of a damaged composite component. This approach would imply in the use of a composite repair patch capable of increasing the stiffness of a damaged component with minimal material addition, resulting in the minimization of costs with component replacements and extend the structures life. In this context, the present work exposes initial studies concerning simple repair shapes optimization applied to damaged composite materials. The main objective of this research is to propose an optimization procedure capable of specifying suitable patch shapes to be applied in a pre-assessed damaged area of a laminated component. The optimization formulation was defined considering as objective function the minimization of the error with respect to the structure first natural frequencies. Linear programming along with an interior point algorithm was employed in order to obtain an optimized repair patch shape. The analyzed model was a rectangular multilayered plate with a predefined damaged zone. Epoxi-graphene composite with transversely isotropic material behavior was considered for all components. A shell finite elements model was used to solve the associated modal problem
A modal-based shape optimization methodology for conventionally shaped patches in composite plate repair
Full text linkComposite materials are known to excel in high-performance applications, particularly in the aerospace industry. Due to this fact, there is a growing concern regarding the maintenance, repair, and overhaul operations of such materials. Within this context, the best approaches for restoring the degraded mechanical properties of composites converge towards the use of fiber-reinforced adhesive patches. The present work proposes a novel methodology for the shape optimization of patches for the recovery of locally damaged composite plates. A shape optimization problem was formulated with the aim of minimizing the error associated with the modal response of the repaired structure to that of the undamaged one. Sequential linear programming was employed alongside an interior point algorithm to attain the optimized dimensions of rectangular single-sided patches, which were used in the restoration of simply supported damaged square panels. The damage was introduced by the mechanical removal of material along the central region. Modal and three-point bending tests were conducted to evaluate the performance of the patch repair. The modal response of the repaired panels indicated an efficiency of 98.2% restoration of the first natural frequency. The effectiveness in terms of mechanical strength was 94.0% in restoring the maximum resisted load, and 96.5% in terms of the ultimate displacement
Aperfeiçoamento em Sistema de Transporte, Acoplamento/Montagem e Operação de Balanceamento Dinâmico Móvel
No full textA invenção ora proposta contempla uma solução criada em formato de chassis (rigidez controlada e distribuída com um arranjo otimizado) com pesos (massas elevadas diretamente no contato ao solo) nas bases que aportam estabilidade e alinhamento. Portanto, é proposto um sistema com duas sapatas massivas que atuam diretamente sobre o solo, sobre estas atua o chassi com rigidez distribuída de modo a maximizar a eficiência na distribuição de esforços às sapatas, além disso, o chassi possui na sua parcela central um acoplamento para a pista/base que suporta a atuação da máquina balanceadora. Em outras palavras, trata-se de um sistema que permite embarcar uma máquina de balanceamento tornando-a apta a realizar o balanceamento sem a ancoragem da mesma numa base de concreto armado. Para tanto há um chassi e duas sapatas desenvolvidos para realizar a função de adição de massa (kg). A base da máquina de balanceamento, que normalmente é fabricada com um formato de trilho para que a estrutura dos sensores possa ser movimentada conforme o tamanho da peça, ficará parafusada no chassi, e será transportada com ele
Mech2APDL
No full textMech2APDL è un software sviluppato in linguaggio Python, progettato per automatizzare e semplificare l'integrazione di dati materiali complessi nelle simulazioni ingegneristiche. Lo strumento esegue il trattamento statistico delle proprietà fisico-meccaniche di materiali polimerici e compositi, e integra questi dati direttamente in modelli per l'analisi a elementi finiti (FEA). L'obiettivo principale è ridurre significativamente i tempi di pre-processing, minimizzare gli errori manuali e aumentare l'accuratezza e l'affidabilità delle simulazioni strutturali in materiali avanzati. (Numero di registrazione INPI / Brasile: BR512025002465-7
Numerical and Experimental Analysis of the Mechanical Response of a Rotatory Balancing System for Industrial In-Situ Calibration
Full text linkThe present work introduces the validation of an unorthodox solution for the balancing of rigid rotors: SimMov, a piece of customized equipment for the transport of specific machinery to carry out the balancing process in situ. For such purpose, the FE models used to assess the mechanical response of the structure are exposed. The numerical results were compared, in terms of acceleration, with experimental measurements obtained with the SimMov equipment. The acceleration response was also tested through standard balancers with a permanent and rigid base, which is the usual practice for similar machinery. Moreover, a simple rotor dynamics model was solved to verify the structure's critical operating behavior. These solutions were used as input data for the FE models employed to predict the structure's response. In the FE models, high-order shell elements were used to solve modal problems using the Lanczos block algorithm. The experimental results were probed and compared at critical points, predefined by the numerical models. Data acquisition was performed with six MEMS sensors (designed for industrial applications). A sampling rate of 10.00 kHz was employed. Data processing was performed using power spectral density (Welch's method). The comparison of results demonstrated the correct functioning of SimMov for the unbalance level considered as allowable by the machine manufacturer
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