Departamento de Ingeniería Mecánica y Minera
URI permanente para esta comunidadhttps://hdl.handle.net/10953/41
En esta Comunidad se recogen los documentos generados por el Departamento de Ingeniería Mecánica y Minera y que cumplen los requisitos de Copyright para su difusión en acceso abierto.
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Ítem A meshfree approach for analyzing strain fields near crack tips from Digital Image Correlation displacement data(Wiley, 2024-03-24) Gómez-Gonzales, Giancarlo Luis; Camacho-Reyes, Alonso; Ortiz-González, Julián Andrés; Diaz-Garrido, Francisco AlbertoThe element-free Galerkin (EFG) meshfree method is employed in this research to compute strain fields based on discrete displacement data obtained from digital image correlation (DIC). To validate the method's accuracy, both simulated images with highly heterogeneous deformations and real tests conducted on notched specimens with known solutions are initially employed. The study then investigates the strain field near the crack tip in an AISI 1020 steel specimen through a multiscale experiment. From the macroscale experiment, the strain data are used to determine the crack-tip plastic zone size, and the solution is compared with predictions from linear-elastic fracture mechanics. The stress intensity factor is also determined. Furthermore, the high strain gradient ahead of the crack tip is determined from the microscale experiment and compared against commercial DIC software. Experimental results confirm the effectiveness of the proposed formulation in crack tip analysis.Ítem Effect of crack flank holes on fatigue crack growth(Elsevier, 2023-01-07) Neto, Diogo Mariano; Cavaleiro, Nuno; Sérgio, Edmundo; Jesus, Joel de; Camacho-Reyes, Alonso; Antunes, Fernando VenturaThe effect of drilling two symmetric holes along the crack flanks on the fatigue crack growth (FCG) rate was evaluated numerically. The FCG increases (decreases) when the crack tip is behind (ahead) the holes. This behaviour is enlarged both by increasing the diameter of the holes and by reducing the distance between them. This is consequence of the geometrical effect, which modifies the plastic zone size. Experimental work validated the numerical model, indicating that that cumulative plastic strain at the crack tip is an adequate crack driving force and that cyclic plastic deformation is the main damage mechanism of FCG.Ítem Investigation of Plasticity Effects on Growing Fatigue Cracks Using the CJP Model of Crack Tip Fields(MDPI, 2023-08-22) Vasco, José Manuel; Camacho-Reyes, Alonso; Gómez-Gonzales, Giancarlo Luis; Diaz-Garrido, Francisco AlbertoA growing fatigue crack gives rise to a plastic enclave that envelops the crack and can exert a shielding effect on the crack from the global elastic stress field driving fatigue propagation. This work presents the potential of the CJP model of crack tip fields to investigate the plasticity-induced shielding effects on growing fatigue cracks as well as its ability to characterise the size and shape of the plastic zone generated at the tip of a growing fatigue crack. The model was specifically developed to consider the influence of the plastic enclave generated around a fatigue crack on the surrounding elastic material. Different aspects related to fracture mechanics and its implications for fatigue crack growth have been investigated, namely plasticity-induced crack shielding, the retardation effect induced on fatigue crack growth due to the application of an overload and the estimate of the size and shape of the crack tip plastic zone. The model has been successfully applied by analysing displacement fields experimentally measured by DIC in different CT specimens made of 2024-T3 aluminium alloy and commercially pure titanium. Results presented in this work intend to contribute to a better understanding of the shielding effects during fatigue crack growth.Ítem Numerical analysis of compliance and fatigue life of the CCC specimen(Elservier, 2023-01-23) Neto, Diogo Mariano; Antunes, Fernando Ventura; Sérgio, Edmundo; Branco, Ricardo; Camacho-Reyes, Alonso; Díaz-Garrido, Francisco Alberto; Gómez-Gonzales, Giancarlo Luis; Vasco, José ManuelThis study presents the numerical evaluation of the compliance in the CCC specimen aiming to assess the crack length inside the specimen. The numerical model considered the elastoplastic behaviour of the specimen, which is modelled using axisymmetric finite elements. The results shown that the propagation of the crack yields a nonlinear increase of the compliance. Nevertheless, variation of the compliance is very small for small values of crack radius. Considering a loading sequence composed by four load blocks of constant amplitude, the fatigue crack growth was predicted both using the Paris law and the numerical model. Both predictions agree but only the numerical simulation is able to capture the crack retardation between load blocksÍtem Study of Effective Stress Intensity Factor through the CJP Model Using Full-Field Experimental Data(MDPI, 2023-08-20) Camacho-Reyes, Alonso; Vasco, José Manuel; Gómez-Gonzales, Giancarlo Luis; Diaz-Garrido, Francisco AlbertoIn this work, the Christopher–James–Patterson crack tip field model is used to infer and assess the effective stress intensity factor ranges measured from thermoelastic and digital image correlation data. The effective stress intensity factor range obtained via the Christopher– James–Patterson model, which provides an effective rationalization of fatigue crack growth rates, is separated into two components representing the elastic and retardation components to assess shielding phenomena on growing fatigue cracks. For this analysis, fatigue crack growth tests were performed on Compact-Tension specimens manufactured in pure grade 2 titanium for different stress ratio levels, and digital image correlation and thermoelastic measurements were made for different crack lengths. A good agreement (~2% average deviation) was found between the resultsobtained via thermoelastic stress analysis and digital image correlation indicating the validity of theChristopher–James–Patterson model to investigate phenomena in fracture mechanics where plasticityplays an important role. The results show the importance of considering crack-shielding effects usingthe Christopher–James–Patterson model beyond considering an exclusive crack closure influence.Ítem Studying the Effect of Short Carbon Fiber on Fused Filament Fabrication Parts Roughness via Machine Learning(Mary Ann Liebert, Inc., publishers, 2023-12-11) García Collado, Alberto; Romero Carrillo, Pablo; Dorado Vicente, Rubén; Gupta, Munish KumarAlong with the characteristic staircase effect, short carbon fibers, added to reinforce Fused Filament Fabrication parts, can significantly worsen the resulting surface finishing. Concerning this topic, the present work intends to improve the existing knowledge by analysing 2400 measurements of arithmetic mean roughness Ra corresponding to different combinations of six process parameters: the content by weight of short carbon fibers in PETG filaments f, layer height h, surface build angle th, number of walls w, printing speed s, and extruder diameter d. The collected measurements were represented by dispersion and main effect plots. These representations indicate that the most critical parameters are th, f, and h. Besides, up to a carbon fiber content of 12%, roughness is mainly affected by the staircase effect. Hence, it would be likely to obtain reinforced parts with similar roughness to unreinforced ones. Different machine learning methods were also tested to extract more information. The prediction model of Ra using the Random Forest algorithm showed a correlation coefficient equal to 0.94 and a mean absolute error equal to 2.026 μm. On the other hand, the J48 algorithm identified a combination of parameters (h = 0.1 mm, d = 0.6 mm, and s = 30 mm/s) that, independently of the build angle, provides a Ra < 25 µm when using a 20% carbon fiber PETG filament. An example part was printed and measured to check the models. As a result, the J48 algorithm correctly classified surfaces with low roughness (Ra < 25 μm), and the Random Forest algorithm predicted the Ra value with an average relative error of less than 8 %.