Hole making process of carbon fiber reinforced polymer (CFRP) using end mill cutting tool

This paper presents an alternative way of producing a hole by using a helical milling concept on a carbon fiber reinforced polymer (CFRP). Delamination is a major problem associated with making a hole by drilling on the CFRP. This study focused on helical milling technique using a vertical machining center in order to produce a hole. Various levels of cutting parameter such as cutting speed, feed rate and depth of cut have been chosen to observe the effect of trust force, delamination and surface roughness. The result will be used to determine on which cutting parameters give the best hole quality that will achieved by this new approached

Fracture of solar-grade anisotropic polycrystalline Silicon: A combined phase field–cohesive zone model approach

Artículo Open Access en el sitio web del editor. Pago por publicar en abierto.This work presents a novel computational framework to simulate fracture events in brittle anisotropic polycrystalline materials at the microscopical level, with application to solar-grade polycrystalline Silicon. Quasi-static failure is modeled by combining the phase field approach of brittle fracture (for transgranular fracture) with the cohesive zone model for the grain boundaries (for intergranular fracture) through the generalization of the recent FE-based technique published in [M. Paggi, J. Reinoso, Comput. Methods Appl. Mech. Engrg., 31 (2017) 145–172] to deal with anisotropic polycrystalline microstructures. The proposed model, which accounts for any anisotropic constitutive tensor for the grains depending on their preferential orientation, as well as an orientation-dependent fracture toughness, allows to simulate intergranular and transgranular crack growths in an efficient manner, with or without initial defects. One of the advantages of the current variational method is the fact that complex crack patterns in such materials are triggered without any user-intervention, being possible to account for the competition between both dissipative phenomena. In addition, further aspects with regard to the model parameters identification are discussed in reference to solar cells images obtained from transmitted light source. A series of representative numerical simulations is carried out to highlight the interplay between the different types of fracture occurring in solar-grade polycrystalline Silicon, and to assess the role of anisotropy on the crack path and on the apparent tensile strength of the material.Unión Europea FP/2007–2013/ERC 306622Ministerio de Economía y Competitividad MAT2015–71036-P y MAT2015–71309-PJunta de Andalucía P11-TEP-7093 y P12-TEP- 105

A New Approach To Measure Unique Spectral Response Characteristics For Irregularly Shaped Photovoltaic Arrays

Current photovoltaic (PV) panel test methods do not provide efficient and repeatable standardization, which can result in inconsistent results. Test requirements for individual PV cells are promulgated by standard test conditions (STC), but do not directly translate to new array or panel designs, particularly for panels that are irregularly shaped and used for different applications. Optimal angles that yield the most power delivery from the PV device when integrated into a panel are achieved by manipulating the panel’s orientation via single or dual axis tracking (e.g., maximum power point tracking). In applications where PV is intended to be integrated into a flying object, such as an unmanned aerial vehicle (UAV), maximum power point tracking (MPPT) is not an option due to aerodynamic constraints resulting from airfoil and control surface design. In these instances, it is pertinent to develop a system that can consistently measure responses of a PV-embedded airfoil in a controlled environment that is also cost-efficient and readily available for researchers to use. Additionally, the system must also be scalable to meet the needs of larger experimental setups for future UAV development. The intent of this dissertation was to propose a new method for capturing the PV-embedded airfoil performance as it compares to a conventional flat panel in terms of efficiencies. As a result, a user has the ability to analyze the collected experimental data and subsequently develop a performance correction factor that is specific to the airfoil used. Recommendations to further enhance analysis of UAV integrated PV efficiency factors, such as vibration impacts on performance, will also be discussed. From an analysis of experimental data, unmanned aerial systems (UAS) engineers can be able to integrate renewable energy systems more effectively and therefore increase vehicle energy efficiency

Concurrently coupled solid shell-based adaptive multiscale method for fracture

Artículo Open Access en el sitio web del editor. Pago por publicar en abierto.A solid shell-based adaptive atomistic–continuum numerical method is herein proposed to simulate complex crack growth patterns in thin-walled structures. A hybrid solid shell formulation relying on the combined use of the enhanced assumed strain (EAS) and the assumed natural strain (ANS) methods has been considered to efficiently model the material in thin structures at the continuum level. The phantom node method (PNM) is employed to model the discontinuities in the bulk. The discontinuous solid shell element is then concurrently coupled with a molecular statics model placed around the crack tip. The coupling between the coarse scale and the fine scale is realized through the use of ghost atoms, whose positions are interpolated from the coarse scale solution and enforced as boundary conditions to the fine scale model. In the proposed numerical scheme, the fine scale region is adaptively enlarged as the crack propagates and the region behind the crack tip is adaptively coarsened in order to reduce the computation costs. An energy criterion is used to detect the crack tip location. All the atomistic simulations are carried out using the LAMMPS software. A computational framework has been developed in MATLAB to trigger LAMMPS through system command. This allows a two way interaction between the coarse and fine scales in MATLAB platform, where the boundary conditions to the fine region are extracted from the coarse scale, and the crack tip location from the atomistic model is transferred back to the continuum scale. The developed framework has been applied to study crack growth in the energy minimization problems. Inspired by the influence of fracture on current–voltage characteristics of thin Silicon photovoltaic cells, the cubic diamond lattice structure of Silicon is used to model the material in the fine scale region, whilst the Tersoff potential function is employed to model the atom–atom interactions. The versatility and robustness of the proposed methodology is demonstrated by means of several fracture applications.Unión Europea ERC 306622Ministerio de Economía y Competitividad DPI2012-37187, MAT2015-71036-P y MAT2015-71309-PJunta de Andalucía P11-TEP-7093 y P12-TEP -105

Monitoring and control of a photovoltaic panel in real time

The performance of the photovoltaic cell, among many factors, also depends on the accurate estimation of its internal and external parameters determined by I-V characterization, whose measurements are affected by noise and the resulting uncertainties. Their determination is of extreme importance and allows the monitoring of the maximum power point (MPP). The present work aims at designing an innovative numerical and simulation platform for op timal characterization purposes. It is a decision support software applied to the estimation of the photovoltaic cell five parameters. The modified Nelder-Mead Algorithm is implemented at its base, which allows the search for the optimum value of each parameter. Furthermore, through an experimental work, it is sought to show the performance of the developed algo rithm by applying indicators analysis, namely RMSE and R-squared. This algorithm will be also implemented in a low-cost embedded system where the purpose is to calculate the MPP; Resumo: Monitorização e controlo de um painel fotovoltaico em temo real - O desempenho da célula fotovoltaica, entre muitos fatores, depende também da estimativa precisa dos seus parâmetros internos e externos determinados pela caracterização I-V, cujas medições são afetadas pelo ruído e pelas incertezas resultantes. A sua determinação é de ex trema importância e permite a monitorização do ponto de potência máxima (MPP). O presente trabalho visa a conceção de uma inovadora plataforma numérica e de simulação para fins de caracterização ótima. Trata-se de um software de apoio à decisão aplicado à estimativa dos cinco parâmetros de uma célula fotovoltaica. Na sua base encontra-se imple mentado o Algoritmo Nelder-Mead modificado, o que permite a procura do valor ótimo de cada parâmetro. Além disso, através de um trabalho experimental, pretende-se mostrar o de sempenho do algoritmo desenvolvido aplicando a análise de indicadores, nomeadamente RMSE e R-squared. Este algoritmo será também implementado num sistema integrado de baixo custo com o objetivo de calcular o MPP

Extremum seeking control techniques applied to photovoltaic systems with multimodal power curves

International audienceThis paper proposes a modified Perturb and Observe (P&O) Extremum Seeking Control (ESC) technique in presence of multiple maxima. ESC is applied to single-phased grid-connected photovoltaic (PV) arrays which have to provide maximum power irrespective of solar irradiance conditions. In particular, partially shadow conditions may lead to steady-state power curves exhibiting multiple maxima. The power harvested from the PV generator is injected in the single-phased power grid by using two power converter stages: step-up DC-DC converter and DC-AC inverter. When multiple power maxima exist, the amplitude of the perturbation signal plays an important role in successfully tracking the global maximum. Two amplitude modulation strategies are analyzed for the same case study: amplitude modulation by using a first-order-system-response signal and amplitude modulation by using small duty ratio square-wave signal, respectively. MATLAB®/Simulink® numerical simulations are presented in order to assess the two approaches comparatively