E. A. Patterson

University of Liverpool, Liverpool, England, United Kingdom

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Publications (213)185.46 Total impact

  • G. Labeas, Vasilis P Pasialis, X.Lin, E.A. Patterson
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    ABSTRACT: Engineering simulation has a significant role in the process of design and analysis of most engineered products at all scales and is used to provide elegant, light-weight, optimized designs. A major step in achieving high confidence in computational models with good predictive capabilities is model validation. It is normal practice to validate simulation models by comparing their numerical results to experimental data. However, current validation practices tend to focus on identifying hot-spots in the data and checking that the experimental and modeling results have a satisfactory agreement in these critical zones. Often the comparison is restricted to a single or a few points where the maximum stress/strain is predicted by the model. The objective of the present paper is to demonstrate a step-by-step approach for performing model validation by combining full-field optical measurement methodologies with computational simulation techniques. Two important issues of the validation procedure are discussed, i.e. effective techniques to perform data compression using the principles of orthogonal decomposition, as well as methodologies to quantify the quality of simulations and make decisions about model validity. An I-beam with open holes under three-point bending loading is selected as an exemplar of the methodology. Orthogonal decomposition by Zernike shape descriptors is performed to compress large amounts of numerical and experimental data in selected regions of interest (ROI) by reducing its dimensionality while preserving information; and different comparison techniques including traditional error norms, a linear comparison methodology and a concordance coefficient correlation are used in order to make decisions about the validity of the simulation.
    Simulation Modelling Practice and Theory 03/2015; 52(C):92-107. DOI:10.1016/j.simpat.2014.12.006 · 1.05 Impact Factor
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    Fatigue & Fracture of Engineering Materials & Structures 05/2014; 38(2). DOI:10.1111/ffe.12213 · 1.06 Impact Factor
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    ABSTRACT: An approach for the measurement of surface displacement fields in three dimensions is presented based on the combination of two-dimensional digital image correlation with fringe projection. Only a single RGB image is required at each deformation state, thereby allowing real-time data acquisition, which is achieved using red speckle and projected blue fringes that are captured in the single image and separated using a Bayer filter. The approach allows both a perpendicular alignment relative to a flat reference surface and self-calibration, i.e., no calibration object is employed. The minimum measurement uncertainty of such a system is found to be 0.0083 +/- 0.00239 and 0.0238 +/- 0.0068 mm, respectively, for the in-plane and out-of-plane displacements. The potential of the approach is demonstrated for an elastic membrane undergoing large (5 to 20 mm) applied out-of-plane displacements, and the results show no significant difference (< 1%) in the measured in-plane displacement fields compared with a commercially available system for stereoscopic digital image correlation. (C) 2014 Society of Photo-Optical Instrumentation Engineers (SPIE)
    Optical Engineering 04/2014; 53(4):044106. DOI:10.1117/1.OE.53.4.044106 · 0.96 Impact Factor
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    ABSTRACT: The combination of fringe projection (FP) and two-dimensional digital image correlation (2D-DIC) has been proposed in previous work [1] as an alternative method to obtain displacement maps in the three spatial directions. However, if a telecentric lens is not employed in the experimental setup, the in-plane displacements obtained with 2D-DIC are influenced by the out-of-plane displacements occurring during deformation. Nevertheless, this error can be corrected if the out-of-plane displacements are known, for instance from measurements using the FP technique. In this paper a novel methodology based on the combination of FP and 2D-DIC is employed to perform the correction of the in-plane displacements, and is applied to several experimental examples. Results are compared and validated with those obtained using a commercial 3D-DIC system showing an average displacement error of 4% for X-displacements and 6.5% for Y-displacements.
    Optics and Lasers in Engineering 01/2014; 52:66-74. DOI:10.1016/j.optlaseng.2013.07.025 · 1.70 Impact Factor
  • M. N. James, Y. Lu, C. J. Christopher, E.A. Patterson
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    ABSTRACT: A significant amount of research has been directed towards characterising and predicting sub-critical crack growth mechanisms in polycarbonate (PC) materials. In particular the initiation of crazes, damage evolution and growth of fatigue cracks has attracted significant attention. It is only relatively recently that there has been clarification of the underlying physics of craze initiation and growth, and of the craze influence on crack paths. In the interpretation of mechanisms of deformation, the polymer community has perhaps not embraced the use of fractographic crack path information as fully as the metals community. This paper considers the ability of advanced imaging techniques including confocal laser scanning microscopy (CLSM), and field emission scanning electron microscopy (FESEM) to provide evidence of crack path morphology for existing models of plastic deformation and crazing in amorphous polycarbonate. It also presents the outline of a new model of crack tip stresses which takes account of craze-induced shielding mechanisms and appears able to characterise fatigue crack growth in PC.
    Engineering Fracture Mechanics 08/2013; 108:89-97. DOI:10.1016/j.engfracmech.2013.02.003 · 1.66 Impact Factor
  • The Journal of Strain Analysis for Engineering Design 04/2013; 49(4):212-223. DOI:10.1177/0309324713498074 · 1.01 Impact Factor
  • D. Backman, E. A. Patterson
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    ABSTRACT: Fatigue tests carried out on three configurations (unexpanded, cold expanded and riveted) of fiber metal laminate material clearly demonstrated the beneficial effect of riveting compared to cold expansion in zero load transfer joints, for an approximately equivalent level of interference. Digital image correlation was used to measure the in-plane surface strain on cold expanded and riveted coupons during fatigue loading, and for the first time, digital image correlation was combined with pressure sensitive films to measure the strains resulting from the application of the rivet, including those under the rivet head. A comparison of the resultant strain field showed that the application of a rivet significantly reduces the stress concentration at the central hole and is effective in extending fatigue life. Some rivet heads were removed by milling, and the results from subsequent fatigue tests were used together with closed-form calculations to explain the findings of this study. It was concluded that the beneficial effect of riveting was less as a result of interference hole filling on the part of the rivet shank, but more a combination of the effect of interference and compression through the joint thickness.
    The Journal of Strain Analysis for Engineering Design 03/2013; 49(3):141-153. DOI:10.1177/0309324713493082 · 1.01 Impact Factor
  • Shan Fu, Eann Patterson
    The Journal of Strain Analysis for Engineering Design 02/2013; 48(1):3-4. DOI:10.1177/0309324712473553 · 1.01 Impact Factor
  • International Journal of Fatigue 01/2013; 46:1. DOI:10.1016/j.ijfatigue.2012.08.001 · 1.69 Impact Factor
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    ABSTRACT: The need to provide strong evidence of the validity of predictions from computational solid mechanics models used in engineering design decisions is discussed. A new procedure is proposed, based on image decomposition, for reducing the dimensionality of strain field data from models and experiments and then comparing the resultant feature vectors via a simple linear correlation in which validation is deemed to be achieved when the coordinate pairs from the two feature vectors lie within a scatter band defined by the minimum measurement uncertainty. The procedure is illustrated by some simple examples that allow the advantages and drawbacks of the approach to be highlighted. It is anticipated that the procedure could become part of a corporate plan or regulatory process for verification and validation of computational solid mechanics models.
    The Journal of Strain Analysis for Engineering Design 01/2013; 48(1):36-47. DOI:10.1177/0309324712453409 · 1.01 Impact Factor
  • Eann A. Patterson, Mara Feligiotti, Erwin Hack
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    ABSTRACT: Experimental strain analysis, structural health monitoring and non-destructive testing and evaluation are regarded as separate disciplines that, in general, are deployed independently at different phases in the life cycle of an engineering component, i.e. in the design process, in service and after an event or service period, respectively. It is proposed that the integrated use of these three disciplines is advantageous and beneficial in terms of reduced capital and operational costs for critical and safety-relevant components, as well as, in validating simulations, in both quantifying and reducing risk of unexpected failure, and in estimating remanent life. We propose the foundation of this integration to be data-rich strain fields measured and compared quantitatively, with each other and with data from simulations, at temporal intervals during the life of a component.
    The Journal of Strain Analysis for Engineering Design 01/2013; 48(1):48-58. DOI:10.1177/0309324712444681 · 1.01 Impact Factor
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    ABSTRACT: This paper presents the background and development of a novel ‘plastic inclusion’ approach for dealing with the local plasticity which occurs at the tip of a growing fatigue crack. Localised plasticity arises from crack growth mechanisms and essentially blunts the crack, creates a reversed cyclic plastic zone, and induces shear along the crack flanks, along with the possible generation of wake contact stresses which act on the applied elastic stress field at the boundary of the elastic–plastic enclave surrounding the crack. The paper outlines the development of a meso-scale model of the elastic stress field around a growing crack that explicitly incorporates these interaction effects. The outcome is a modified crack tip stress intensity factor that includes some aspects of the magnitude of plastic wake-induced crack tip shielding and which the authors propose has the potential to help resolve some long-standing controversies associated with plasticity-induced closure. A full-field approach is developed for stress using photoelasticity and also for displacement using digital image correlation.
    International Journal of Fatigue 01/2013; 46:4–15. DOI:10.1016/j.ijfatigue.2012.04.015 · 1.69 Impact Factor
  • C. Sebastian, E.A. Patterson
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    ABSTRACT: The use and results of the procedure published by Standardisation Project for Optical Techniques of Strain measurement (SPOTS) for a successful calibration of a digital image correlation (DIC) system are described. The details of the calibration specimen used are discussed together with procedure and criteria that must be met to achieve an acceptable calibration. The DIC system was evaluated over a strain range of 289 to 2110 µstrain, with a resulting calibration uncertainty ranging from 14 to 28.7 µstrain. The optical strain measurements were obtained from images taken directly from the bare metal surface, which had been prepared with grit paper, as opposed to generating a speckle pattern by painting the surface.
    Experimental Techniques 12/2012; 39(1). DOI:10.1111/ext.12005 · 0.58 Impact Factor
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    Y. Yang, M. Crimp, R. A. Tomlinson, E. A. Patterson
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    ABSTRACT: A novel approach is introduced to map the mesoscale plastic strain distribution resulting from heterogeneous plastic deformatio in complex loading and component geometries, by applying the discrete Fourier transform (DFT) to backscattered electron (BSE images of polycrystalline patches. These DFTs are then calibrated against the full width at half the maximum of the centra peak of the DFTs collected from the same material tested under in situ scanning electron microscopy uniaxial tensile conditions, which indicates a close relationship with the global tensile strain. In this work, the technique is demonstrated by measuring the residual strain distribution and plastic zone size around a fatigu crack tip in a commercially pure titanium compact tension specimen, by collecting BSE images in a 15×15 array of 115 μm squar images around the fatigue crack tip. The measurement results show good agreement with the plastic zone size and shape measure using thermoelastic stress analysis.
    Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences 08/2012; 468(2144):2399-2415. DOI:10.1098/rspa.2011.0682 · 2.00 Impact Factor
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    Y. Yang, M. A. Crimp, R. A. Tomlinson, E. A. Patterson
    Microscopy and Microanalysis 07/2012; 18(S2):692-693. DOI:10.1017/S1431927612005314 · 1.76 Impact Factor
  • 2012 SEM XII, International Congress and Exposition on Experimental and Applied Mechanics, Costa Mesa, CA USA; 06/2012
  • 2012 SEM XII, International Congress and Exposition on Experimental and Applied Mechanics, Costa Mesa, CA USA; 06/2012
  • Mahmoodul Haq, Conway A, Patterson EA
    2012 SEM XII, International Congress and Exposition on Experimental and Applied Mechanics, Costa Mesa, CA USA; 06/2012
  • Mahmoodul Haq, Patterson EA, Drzal LT
    2012 SEM XII, International Congress and Exposition on Experimental and Applied Mechanics, Costa Mesa, CA USA; 05/2012

Publication Stats

2k Citations
185.46 Total Impact Points

Institutions

  • 2013–2015
    • University of Liverpool
      Liverpool, England, United Kingdom
  • 2005–2014
    • Michigan State University
      • • Department of Mechanical Engineering
      • • Department of Chemical Engineering and Materials Science
      • • Composite Vehicle Research Center
      East Lansing, Michigan, United States
  • 2010–2013
    • University of Plymouth
      • • School of Marine Science and Engineering
      • • Faculty of Science and Technology
      Plymouth, England, United Kingdom
  • 1985–2008
    • The University of Sheffield
      • Department of Mechanical Engineering
      Sheffield, England, United Kingdom
  • 2006
    • Warsaw University of Technology
      • Institute of Micromechanics and Photonics
      Warszawa, Masovian Voivodeship, Poland