1,608 research outputs found
Integración de la metodología PBL y el uso del software CES EduPack para el aprendizaje colaborativo
Este trabajo es la propuesta del diseño y desarrollo de una herramienta didáctica basada en un juego de cartas del software CES EduPack para adquirir la competencia o aprendizaje de los órdenes de magnitud de parámetros de medida de las propiedades de los materiales. El trabajo ha sido desarrollado para su aplicación en el ámbito de la Ingeniería dentro del campo de la Ciencia y Tecnología de Materiales. Se propone el diseño de las cartas y metodología de uso del juego, así como, unas pruebas de test para evaluar dicho recurso como herramienta didáctica. También se analizan las ventajas pedagógicas del método frente a la metodología tradicional. La propuesta presenta como ventaja que el material de este recurso educativo es fácil de elaborar y su coste es realmente económico. Se plantea finalmente la posibilidad de extender su uso al aprendizaje de similares competencias y su futura implementación en software.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
3D numerical study of the transient behaviour on plasticity induced crack closure
Daniel Camas, Fernando Antunes, Pablo Lopez-Crespo, Antonio Gonzalez-Herrera, 3D Numerical Study of the Transient Behaviour on Plasticity Induced Crack Closure, Abstract Booklet of the MSMF9, Edited by Pavel Sandera, Brno University of Technology, 2019, pp. 136.The numerical analysis of the plasticity induced crack closure requires the development of the plastic wake. Transient behaviour is observed when the crack starts to grow. The plastic wake length has an influence on the crack closure results and a great impact on the computational cost. Previous works have analysed the influence of this parameter considering bi-dimensional specimens in either plane strain or plane stress conditions. Lately, some three-dimensional models have appeared in order to analyse the crack closure phenomenon. The main scope of this study is to quantify and comprehend the minimum length required to stabilise the crack opening and closure values considering a three-dimensional model. On this purpose, a CT aluminium specimen has been modelled three-dimensionally and several calculations have been made in order to evaluate the influence of the simulated plastic wake. The numerical analysis is made in terms of crack closure and opening values.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec
A numerical analysis of the plastic wake influence on plasticity induced crack closure
Fatigue crack closure has been studied by means of finite element method since long time
ago. Most work has been performed considering bi-dimensional models. Lately, the use of threedimensional
models has been extended. Nevertheless, the methodology employed has been taken from
that developed for bi-dimensional cases.
There are a great number of previous bi-dimensional studies which analyse different numerical
parameters and optimise them. The current computational capabilities allow a comprehensive study of
the influence of the different modelling parameters in a similar way to those studies carried out with bidimensional
models, with the advantage, that the evolution along the thickness of the analysed
parameters can be taken into consideration.
In particular, one of the key issues is related to the plastic wake length which is developed during the
previous loading cycles. This residual stresses have a great influence on the crack opening and closure
values. As the numerical analysis are complex and computationally expensive, the length of the
simulated wake is a critical parameter.
In this work, a comprehensive study of the effect of the plastic wake in fatigue crack closure is made.
On this purpose, a CT aluminium specimen has been modelled three-dimensionally and several
calculations have been made in order to evaluate the influence of the simulated plastic wake length. The
numerical analysis is made in terms of crack closure and opening values as in terms of the stress and
strain fields near the crack front.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Experimental and analytical study of cracks under biaxial fatigue
Most mechanical components experience multi-axial cyclic loading conditions during service.
Experimental analysis of fatigue cracks under such conditions is not easy and most works tend to focus more
on the simpler but less realistic case of uni-axial loading. Consequently, there are many uncertainties related to
the load sequence effect that are now well known and are not normally incorporated into the growth models.
The current work presents a new methodology for evaluating overload effect in biaxial fatigue cracks. The
methodology includes evaluation of mixed-mode (KI and KII) stress intensity factor and the Crack Opening
Displacement for samples with and without overload cycle under biaxial loading. The methodology is tested
under a range of crack lengths. All crack-tip information is obtained with a hybrid methodology that combines
experimental full-field digital image correlation data and Williams' elastic model describing the crack-tip field.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Some experimental observations of crack-tip mechanics with displacement data
Estudio de la mecánica en el vértice de la grieta mediante datos de desplazamiento.In the past two decades, crack-tip mechanics has been increasingly studied with full-field
techniques. Within these techniques, Digital Image Correlation (DIC) has been most widely used due to its
many advantages, to extract important crack-tip information, including Stress Intensity Factor (SIF), Crack
Opening Displacement, J-integral, T-stress, closure level, plastic zone size, etc. However, little information is
given in the literature about the experimental setup that provides best estimations for the different parameters.
The current work aims at understanding how the experimental conditions used in DIC influence the crack-tip
information extracted experimentally. The influence of parameters such as magnification factor, size of the
images, position of the images with respect the crack-tip and size of the subset used in the correlation is studied.
The influence is studied in terms of SIF and T-stress by using Williams’ model. The concept of determination of
the K-dominance zone from experimental data has also explored. In this regard, cyclic loading on a fatigue
crack in a compact tension (CT) specimen, made of aluminium 2024-T351 alloy, has been applied and the
surface deformation ahead of the crack tip has been examined. The comparison between theoretical and
experimental values of KI showed that the effect of subset size on the measured KI is negligible compared to
the effect of size of the image.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Hyperfine splitting in heavy ions with the nuclear magnetization distribution determined from experiments on muonic atoms
The hyperfine splitting in hydrogenlike Bi, Tl, and
Tl is calculated with the nuclear magnetization determined from
experimental data on the hyperfine splitting in the corresponding muonic atoms.
The single-particle and configuration-mixing nuclear models are considered. The
QED corrections are taken into account for both electronic and muonic atoms.
The obtained results are compared with other calculations and with experiment.Comment: 8 pages, 5 tables, accepted for publication in Nuclear Instruments
and Methods in Physics Research
Experimental evaluation of Stress Intensity Factors from strain fields using Digital Image Correlation
P Lopez-Crespo, A. Garcia-Gonzalez, Experimental evaluation of Stress Intensity Factors from strain fields using Digital Image Correlation, Proceedings of Jornadas Idmati 2014, Barcelona, junio de 2014Optical techniques offer many benefits to experimentalist compared with gauge methods. Optical techniques such as holographic interferometry, electronic speckle pattern interferometry, photo- and thermoelasticity, and various grid methods are non-contact, full-field and can have high resolution.
However, they are expensive or require special surface preparation or provide reliable measurements only in certain locations (fringes). Moreover, these techniques are hard to apply in field conditions. In contrast, the image correlation technique is cheap, easy, versatile and requires minimal surface preparation. It is ideally suited for field application. In this work a two-dimensional image correlation method was used to measure in-plane displacement fields near crack tip. Linear elasticity was assumed outside the crack tip plasticity zone. In the elastic region Muskhelishvili's complex functions approach was used to calculate the stress intensity factors from the measured displacements.
functions were used to calculate the stress intensity factors from the measured displacements.
Computationally the problem is that of solving an overdetermined system of non-linear equations. In this work genetic algorithm was used to find the solution.
The method was applied to fatigue cracks in 2 and 3 mm thick Al 7010 alloy plates loaded under mixed mode (I+II). The stress intensity factors were calculated to within 10-20% of the nominal applied values. In addition the crack tip location was calculated. The sensitivity of the technique to the experimental noise and the issues of the location and the number of the experimental data points will be discussed. Finally the extention of the method to a real time monitoring will be analysed.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
High magnification crack-tip field characterisation under biaxial conditions
This work presents a novel methodology for characterising fatigue cracks under biaxial conditions.The methodology uses high magnification Digital Image Correlation (DIC) technique for measuringdisplacement and strain crack-tip fields. By applying micro-speckle pattern on the metal surface it is possible toachieve high magnification for DIC technique. The speckles were created by electro-spray technique. Thevalidity of this novel technique is demonstrated by direct comparison with standard extensometermeasurements, under tension-compression and torsion conditions. In order to image the correct region, thenotch effect on the fatigue life was also evaluated
Comportamiento cíclico de una acero St-52-3N: Influencia de los módulos de elasticidad en las estimaciones de vida a fatiga
Dada la dependencia de los módulos de elasticidad en los métodos de estimación de vida a fatiga, se analiza el
comportamiento cíclico y la variación de estos con el grado de deformación. En este estudio se llevan a cabo una serie de
experimentos de fatiga uniaxial en control de deformación, con R=-1, a bajo número de ciclos y a temperatura ambiente,
para caracterizar el comportamiento cíclico del acero al carbono St-52-3N. Se realizaron ensayos de fatiga uniaxial tanto
de tracción como de torsión.
Se compara los valores de los módulos de elasticidad monotónico y cíclico, además de los valores cíclicos
correspondientes a los segmentos de descarga y carga (E1 ,E2) (acordes con ISO/DIS 121106). Se pone de manifiesto la
variabilidad cometida al calcular el incremento de deformación plástica según el Método Estándar de ensayo que
utilicemos (BS/ISO, ASTM, AECMA) y que determinará en cada caso la estimación del módulo de elasticidad cíclicoUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tec
Study of the stress intensity factors in the bulk of the material with synchrotron diffraction
Artículo de Proceedings de Congreso Internacional Fatigue2017In this work we present the results of a hybrid experimental and
analytical approach for estimating the stress intensity factor. It uses the
elastic strains within the bulk obtained by synchrotron X-ray diffraction
data. The stress intensity factor is calculated using a multi-point overdeterministic
method where the number of experimental data points is
higher than the number of unknowns describing the elastic field
surrounding the crack-tip. The tool is tested on X-ray strain
measurements collected on a bainitic steel. In contrast to surface
techniques the approach provides insights into the crack tip mechanics
deep within the sample.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. The authors are grateful to the ESRF for ID15 beamtime awarded under MA-1483. Financial
support of Universidad de Malaga through Plan Propio, Junta de Andalucía through Proyectos de
Excelencia grant reference TEP-3244, Campus de Excelencia Internacional del Mar (CEIMAR)
and Ministerio de Economia y Competitividad through grant reference MAT2016-76951-C2-2-P is
also acknowledged. PJW acknowledges an ERC advanced grant
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