Assessing the Impact of Membrane Deformations on Wing Sail Performance

Abstract The aim of this research is to quantify the membrane deformations and their impact on performance for a ribbed wing sail. A 1m x 0.8m rectangular planform NACA0012 foil was designed to replicate a single section of a wing-sail. Two foils were manufactured based on this geometry, one out of solid foam and one using a rib and membrane structure. These were tested in the R.J. Mitchell closed return 3.6 m x 2.5 m wind tunnel at the University of Southampton. Their aerodynamic performance was assessed over a range of angles of attack using a six-component force balance showing the overall performance of the membrane wing was reduced by between 5-11% depending on the analysis conducted. A stereo camera system was used to perform Digital Image Correlation (DIC) in order to quantify the full field deformation of the membrane wing structure whilst under aerodynamic load. This showed membrane deformations of up to 15% of the section thickness. The experimental membrane displacements were then used to create a deformed wing sail geometry, removing the effect of foil bend and twist, allowing a CFD investigation of the impact of membrane deformations alone. This indicated that the static membrane deformations resulted in a decrease in performance of up to 1.3% compared to the rigid aerofoil.

Download Full-text

Full-Field Operational Modal Analysis of an Aircraft Composite Panel from the Dynamic Response in Multi-Impact Test

Sensors ◽

10.3390/s21051602 ◽

2021 ◽

Vol 21 (5) ◽

pp. 1602

Author(s):

Ángel Molina-Viedma ◽

Elías López-Alba ◽

Luis Felipe-Sesé ◽

Francisco Díaz

Keyword(s):

Modal Analysis ◽

Energy Absorption ◽

High Speed ◽

Operational Modal Analysis ◽

Modal Identification ◽

Image Correlation ◽

Composite Panel ◽

Impact Excitation ◽

Full Field ◽

The Impact

Experimental characterization and validation of skin components in aircraft entails multiple evaluations (structural, aerodynamic, acoustic, etc.) and expensive campaigns. They require different rigs and equipment to perform the necessary tests. Two of the main dynamic characterizations include the energy absorption under impact forcing and the identification of modal parameters through the vibration response under any broadband excitation, which also includes impacts. This work exploits the response of a stiffened aircraft composite panel submitted to a multi-impact excitation, which is intended for impact and energy absorption analysis. Based on the high stiffness of composite materials, the study worked under the assumption that the global response to the multi-impact excitation is linear with small strains, neglecting the nonlinear behavior produced by local damage generation. Then, modal identification could be performed. The vibration after the impact was measured by high-speed 3D digital image correlation and employed for full-field operational modal analysis. Multiple modes were characterized in a wide spectrum, exploiting the advantages of the full-field noninvasive techniques. These results described a consistent modal behavior of the panel along with good indicators of mode separation given by the auto modal assurance criterion (Auto-MAC). Hence, it illustrates the possibility of performing these dynamic characterizations in a single test, offering additional information while reducing time and investment during the validation of these structures.

Download Full-text

Identification of Orthotropic Elastic Properties of Wood by a Synthetic Image Approach Based on Digital Image Correlation

Materials ◽

10.3390/ma15020625 ◽

2022 ◽

Vol 15 (2) ◽

pp. 625

Author(s):

João Henriques ◽

José Xavier ◽

António Andrade-Campos

Keyword(s):

Digital Image Correlation ◽

Digital Image ◽

Pinus Pinaster ◽

Model Updating ◽

Image Correlation ◽

Synthetic Image ◽

Tangential Plane ◽

Full Field ◽

The Impact ◽

Constitutive Parameters

This work aims to determine the orthotropic linear elastic constitutive parameters of Pinus pinaster Ait. wood from a single uniaxial compressive experimental test, under quasi-static loading conditions, based on two different specimen configurations: (a) on-axis rectangular specimens oriented on the radial-tangential plane, (b) off-axis specimens with a grain angle of about 60(radial-tangential plane). Using digital image correlation (DIC), full-field displacement and strain maps are obtained and used to identify the four orthotropic elastic parameters using the finite element model updating (FEMU) technique. Based on the FE data, a synthetic image reconstruction approach is proposed by coupling the inverse identification method with synthetically deformed images, which are then processed by DIC and compared with the experimental results. The proposed methodology is first validated by employing a DIC-levelled FEA reference in the identification procedure. The impact of the DIC setting parameters on the identification results is systematically investigated. This influence appears to be stronger when the parameter is less sensitive to the experimental setup used. When using on-axis specimen configuration, three orthotropic parameters of Pinus pinaster (ER, ET and νRT) are correctly identified, while the shear modulus (GRT) is robustly identified when using off-axis specimen configuration.

Download Full-text

Static Residual Tensile Strength Response of GFRP Composite Laminates Subjected to Low-Velocity Impact

Applied Sciences ◽

10.3390/app10165480 ◽

2020 ◽

Vol 10 (16) ◽

pp. 5480

Author(s):

Jong-Il Kim ◽

Yong-Hak Huh ◽

Yong-Hwan Kim

Keyword(s):

Tensile Strength ◽

Composite Laminates ◽

Impact Damage ◽

Image Correlation ◽

Matrix Cracking ◽

Low Velocity Impact ◽

Stress Concentrations ◽

Low Velocity ◽

Full Field ◽

The Impact

The dependency of the static residual tensile strength for the Glass Fiber-Reinforced Plastic (GFRP) laminates after impact on the impact energy level and indent shape is investigated. In this study, two different laminates, unidirectional, [0°2]s) and TRI (tri-axial, (±45°/0°)2]s), were prepared using the vacuum infusion method, and an impact indent on the respective laminates was created at different energy levels with pyramidal and hemispherical impactors. Impact damage patterns, such as matrix cracking, delamination, debonding and fiber breakage, could be observed on the GFRP laminates by a scanning electron microscope (SEM), and it is found that those were dependent on the impactor head shape and laminate structure. Residual in-plane tensile strength of the impacted laminates was measured and the reduction of the strength is found to be dependent upon the impact damage patterns. Furthermore, in this study, stress concentrations in the vicinity of the indents were determined from full-field stress distribution obtained by three-dimensional Digital Image Correlation (3D DIC) measurement. It was found that the stress concentration was associated with the reduction of the residual strength for the GFRP laminates.

Download Full-text

Measurement of Transient Dynamic Response of Circuit Boards of a Handheld Device During Drop Using 3D Digital Image Correlation

Journal of Electronic Packaging ◽

10.1115/1.3000097 ◽

2008 ◽

Vol 130 (4) ◽

Cited By ~ 7

Author(s):

S. B. Park ◽

Chirag Shah ◽

Jae B. Kwak ◽

Changsoo Jang ◽

Soonwan Chung ◽

...

Keyword(s):

Digital Image Correlation ◽

Digital Image ◽

High Speed ◽

Image Correlation ◽

Impact Response ◽

Experimental Methodology ◽

Full Field ◽

Handheld Device ◽

3D Digital Image Correlation ◽

The Impact

In this work, a new experimental methodology for analyzing the drop impact response is assessed using a pair of high-speed digital cameras and 3D digital image correlation software. Two different test boards are subjected to Joint Electron Device Engineering Council (JEDEC) standard free-fall impact conditions of half-sine pulse of 1500 G in magnitude and 0.5 ms in duration. The drop is monitored using a pair of synchronized high-speed cameras at a rate of up to 15,000 frames per second. The acquired images are subsequently analyzed to give full-field dynamic deformation, shape, and strain over the entire board during and after impact. To validate this new methodology for analyzing the impact response, the in-plane strain as well as the out-of-plane acceleration at selected locations were measured simultaneously during the drop using strain gauge and accelerometers and were compared with those obtained using high-speed cameras and 3D digital image correlation presented in this paper. Comparison reveals excellent correlation of the transient behavior of the board during impact and confirms the feasibility of using the full-field measurement technique used in this study.

Download Full-text

Characterization of Mechanical Behavior of Polyurethane Foams Using Digital Image Correlation

Applied Mechanics ◽

10.1115/imece2005-81115 ◽

2005 ◽

Author(s):

Helena (Huiqing) Jin ◽

Wei-Yang Lu ◽

Simon Scheffel ◽

Michael K. Neilsen ◽

Terry D. Hinnerichs

Keyword(s):

Digital Image Correlation ◽

Digital Image ◽

Polyurethane Foams ◽

Image Correlation ◽

Compression Tests ◽

Steel Cylinder ◽

Full Field ◽

Strain Concentration ◽

The Impact ◽

Dic Technique

Polyurethane foams have good energy absorption properties and are effective in protecting sensitive components from damages due to impact. The foam absorbs impact energy by crushing cells and undergoing large deformation. The complex deformation of the foam needs to be modeled accurately to simulate the impact events. In this paper, the Digital Image Correlation (DIC) technique was implemented to obtain the deformation field of foam specimens under compression tests. Images of foam specimen were continuously acquired using high-speed cameras. The full field displacement and strain at each incremental step of loading were calculated from these images. The closed-cell polyurethane foam used in this investigation was nominal 0.32 kg/m^3 (20 pcf). In the first experiment, cubic specimens were compressed uniaxially up to 60%. The full-field displacements and strains obtained using the DIC technique provide detailed information about the inhomogeneous deformation over the area of interest during loading. In the second experiment, compression tests were conducted for a simple foam structure - cubic foam specimens with a steel cylinder inclusion. The strain concentration at the interface between steel cylinder and foam was studied to simulate the deformation of foam in a typical application. In the third experiment, the foam was loaded from the steel cylinder during the compression. The strain concentration at the interface and the displacement distribution over the surface were compared for cases with and without a confinement fixture to study the effects of confinement. These experimental results demonstrate that the DIC technique can be applied to polyurethane foams to study the heterogeneous deformation. The experimental data is briefly compared with the results from modeling and simulation using a viscoplastic model for the foam.

Download Full-text

Digital Image Correlation Applications in Composite Automated Manufacturing, Inspection, and Testing

Applied Sciences ◽

10.3390/app9132719 ◽

2019 ◽

Vol 9 (13) ◽

pp. 2719 ◽

Cited By ~ 7

Author(s):

Farjad Shadmehri ◽

Suong Van Hoa

Keyword(s):

Digital Image Correlation ◽

Digital Image ◽

Composite Structures ◽

Structural Testing ◽

Image Correlation ◽

Thermoplastic Composites ◽

Automated Manufacturing ◽

Camera System ◽

Composite Manufacturing ◽

Full Field

Since its advent in the 1970s, digital image correlation (DIC) applications have been rapidly growing in different engineering fields including composite material testing and analysis. DIC combined with a stereo camera system offers full-field measurements of three-dimensional shapes, deformations (i.e., in-plane and out-of-plane deformations), and surface strains, which are of most interest in many structural testing applications. DIC systems have been used in many conventional structural testing applications in composite structures. However, DIC applications in automated composite manufacturing and inspection are scarce. There are challenges in inspection of a composite ply during automated manufacturing of composites and in measuring transient strain during in-situ manufacturing of thermoplastic composites. This article presents methodologies using DIC techniques to address these challenges. First, a few case studies where DIC was used in composite structural testing are presented, followed by development of new applications for DIC in composite manufacturing and inspection.

Download Full-text

Recent Developments in ARCMAC and Related Creep Strain Monitoring Techniques

ASME 2011 Pressure Vessels and Piping Conference: Volume 7 ◽

10.1115/pvp2011-57948 ◽

2011 ◽

Author(s):

Aditya Narayanan ◽

Andy Morris ◽

Catrin Mair Davies ◽

John Dear

Keyword(s):

High Temperature ◽

Creep Strain ◽

High Temperatures ◽

Strain Measurement ◽

Measurement Techniques ◽

Image Correlation ◽

Camera System ◽

Full Field ◽

Optical Strain Measurement ◽

Optical Strain

Developments have been made to E.ON’s Auto-Reference Creep Management and Control (ARCMAC) system to measure strain at high temperature using both Digital Image Correlation (DIC) and conventional ARCMAC techniques. These techniques are aimed at measuring creep strain rate in power plant steam pipes and associated weldments operating at high temperatures and pressures for the purposes of estimation of remaining life of such components. The ARCMAC optical strain measurement system is used to measure point to point strain through the capture and analysis of images of a pair of Inconel gauges, with Silicon Nitride spheres, welded to steam pipe and other components. A modified ARCMAC image capture system has been developed using a DSLR camera, with higher resolution offering the potential to capture DIC images suitable for measuring strain accurately. Development of the system to measure strain using both ARCMAC gauges and DIC at high temperature offers the potential to obtain full-field strain measurement across features such as welds, giving a useful improved research tool for creep evaluation. The recently developed DSLR-ARCMAC camera system has been optimised to measure strain using a number of optical strain measurement techniques, including the ARCMAC strain measurement procedure and DIC. These techniques have been used to measure strain during room temperature tensile tests prior to their use at high temperatures. Following these experiments, creep testing of CMV steel specimens is planned paying particular attention to the evaluation of the ARCMAC system at high temperatures.

Download Full-text

Error Estimations in Digital Image Correlation Technique

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.7-8.265 ◽

2007 ◽

Vol 7-8 ◽

pp. 265-270 ◽

Cited By ~ 17

Author(s):

Thorsten Siebert ◽

Thomas Becker ◽

Karsten Spiltthof ◽

Isabell Neumann ◽

Rene Krupka

Keyword(s):

Digital Image Correlation ◽

Digital Image ◽

Optical Measurement ◽

Measurement Techniques ◽

Image Correlation ◽

Field Analysis ◽

Correlation Technique ◽

Full Field ◽

Wide Range ◽

The Impact

The reliability for each measurement technique depends on the knowledge of it’s uncertainty and the sources of errors of the results. Among the different techniques for optical measurement techniques for full field analysis of displacements and strains, digital image correlation (DIC) has been proven to be very flexible, robust and easy to use, covering a wide range of different applications. Nevertheless the measurement results are influenced by statistical and systematical errors. We discuss a 3D digital image correlation system which provides online error information and the propagation of errors through the calculation chain to the resulting contours, displacement and strains. Performance tests for studying the impact of calibration errors on the resulting data are shown for static and dynamic applications.

Download Full-text

A Correction Method for Heat Wave Distortion in Digital Image Correlation Measurements Based on Background-Oriented Schlieren

Applied Sciences ◽

10.3390/app9183851 ◽

2019 ◽

Vol 9 (18) ◽

pp. 3851 ◽

Cited By ~ 2

Author(s):

Chang Ma ◽

Zhoumo Zeng ◽

Hui Zhang ◽

Xiaobo Rui

Keyword(s):

Digital Image Correlation ◽

Heat Wave ◽

Digital Image ◽

Heat Waves ◽

Correction Method ◽

Image Correlation ◽

Full Field ◽

Wave Disturbances ◽

Background Oriented Schlieren ◽

The Impact

Digital image correlation (DIC) is a kind of displacement and strain measurement technique. It can realize non-contact and full-field measurement and is widely used in the testing and research of mechanical properties of materials at high temperatures. However, many factors affect measurement accuracy. As the high temperature environment is complex, the impact of heat waves on DIC is the most significant factor. In order to correct the disturbance in DIC measurement caused by heat waves, this paper proposes a method based on the background-oriented schlieren (BOS) technique. The spot pattern on the surface of a specimen in digital image correlation can be used as the background in the background-oriented schlieren technique. The BOS technique can measure the distortion information of the images caused by heat flow field. The specimen images taken through the heat waves can be corrected using the distortion information. Besides, the characteristics of distortions due to heat waves are also studied in this paper. The experiment results verify that the proposed method can effectively eliminate heat wave disturbances in DIC measurements.

Download Full-text

Detection of Delamination in Polymer Composites by Digital Image Correlation—Experimental Test

Polymers ◽

10.3390/polym11030523 ◽

2019 ◽

Vol 11 (3) ◽

pp. 523 ◽

Cited By ~ 6

Author(s):

Gábor Szebényi ◽

Viktor Hliva

Keyword(s):

Digital Image Correlation ◽

Digital Image ◽

Composite Structures ◽

Image Correlation ◽

Personal Safety ◽

Compression Tests ◽

Release Agent ◽

Camera System ◽

Full Field ◽

Reinforced Polymer

Fiber-reinforced polymer composite structures are frequently used in industries where personal safety is critical; therefore, it is important to periodically estimate or monitor the condition of high value, load bearing structures. The digital image correlation (DIC) is well known as an effective method to obtain full field surface strains; in this paper, it was used to detect artificial damage inside the structures. Carbon or glass fabric reinforced epoxy specimens were produced and tested. All specimens contained an artificial through-delamination which was created by the insertion of different foils of a mould release agent during production. Tensile and compression tests were done while the camera system collected the images of the deformed surface to be analyzed posteriorly. In most cases the approximate locations of delaminations could be effectively detected from strain maps by the localization of zones showing different strain values than intact zones.

Download Full-text