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3 pages, 155 KiB

Open AccessEditorial

Special Issue on Advances in Digital Image Correlation (DIC)

by Jean-Noël Périé and Jean-Charles Passieux

Appl. Sci. 2020, 10(4), 1530; https://doi.org/10.3390/app10041530 - 24 Feb 2020

Cited by 10 | Viewed by 2955

Abstract

Digital Image Correlation (DIC) has become the most popular full field measurement technique in experimental mechanics [...] Full article

(This article belongs to the Special Issue Advances in Digital Image Correlation (DIC))

Research

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11 pages, 1390 KiB

Open AccessArticle

A Method for Calibrating a Digital Image Correlation System for Full-Field Strain Measurements during Large Deformations

by Robert Blenkinsopp, Jon Roberts, Andy Harland, Paul Sherratt, Paul Smith and Tim Lucas

Appl. Sci. 2019, 9(14), 2828; https://doi.org/10.3390/app9142828 - 16 Jul 2019

Cited by 16 | Viewed by 10138

Abstract

Numerous variables can introduce errors into the measurement chain of a digital image correlation (DIC) system. These can be grouped into two categories: measurement quality and the correlation principle. Although previous studies have attempted to investigate each error source in isolation, there are [...] Read more.

Numerous variables can introduce errors into the measurement chain of a digital image correlation (DIC) system. These can be grouped into two categories: measurement quality and the correlation principle. Although previous studies have attempted to investigate each error source in isolation, there are still no comprehensive, standardized procedures for calibrating DIC systems for full-field strain measurement. The aim of this study, therefore, was to develop an applied experimental method that would enable a DIC practitioner to perform a traceable full-field measurement calibration to evaluate the accuracy of a particular system setup in a real-world environment related to their specific application. A sequence of Speckle Pattern Boards (SPB) that included artificial deformations of the speckle pattern were created, allowing for the calibration of in-plane deformations. Multiple deformation stages (from 10% to 50%) were created and measured using the GOM ARAMIS system; the results were analysed and statistical techniques were used to determine the accuracy. The measured strain was found to be slightly over-estimated (nominally by 0.02%), with a typical measurement error range of 0.34% strain at a 95% confidence interval. Location within the measurement volume did not have a significant effect on error distributions. It was concluded that the methods developed could be used to calibrate a DIC system in-situ for full-field measurements of large deformations. The approach could also be used to benchmark different DIC systems against each other or allow operators to better understand the influence of particular measurement variables on the measurement accuracy. Full article

(This article belongs to the Special Issue Advances in Digital Image Correlation (DIC))

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18 pages, 9805 KiB

Open AccessArticle

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

by Farjad Shadmehri and Suong Van Hoa

Appl. Sci. 2019, 9(13), 2719; https://doi.org/10.3390/app9132719 - 5 Jul 2019

Cited by 23 | Viewed by 5493

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Advances in Digital Image Correlation (DIC))

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21 pages, 17494 KiB

Open AccessArticle

Measurement of Interlaminar Tensile Strength and Elastic Properties of Composites Using Open-Hole Compression Testing and Digital Image Correlation

by Guillaume Seon, Andrew Makeev, Joseph D. Schaefer and Brian Justusson

Appl. Sci. 2019, 9(13), 2647; https://doi.org/10.3390/app9132647 - 29 Jun 2019

Cited by 25 | Viewed by 6154

Abstract

Advanced polymeric composites are increasingly used in high-performance aircraft structures to reduce weight and improve efficiency. However, a major challenge delaying the implementation of the advanced composites is the lack of accurate methods for material characterization. Accurate measurement of three-dimensional mechanical properties of [...] Read more.

Advanced polymeric composites are increasingly used in high-performance aircraft structures to reduce weight and improve efficiency. However, a major challenge delaying the implementation of the advanced composites is the lack of accurate methods for material characterization. Accurate measurement of three-dimensional mechanical properties of composites, stress–strain response, strength, fatigue, and toughness properties, is essential in the development of validated analysis techniques accelerating design and certification of composite structures. In particular, accurate measurement of the through-thickness constitutive properties and interlaminar tensile (ILT) strength is needed to capture delamination failure, which is one of the primary failure modes in composite aircraft structures. A major technical challenge to accurate measurement of ILT properties is their strong sensitivity to manufacturing defects that often leads to unacceptable scatter in standard test results. Unacceptable failure mode in standard test methods is another common obstacle to accurate ILT strength measurement. Characterization methods based on non-contact full-field measurement of deformation have emerged as attractive alternative techniques allowing more flexibility in test configuration to address some of the limitations inherent to strain gauge-based standard testing. In this work, a method based on full-field digital image correlation (DIC) measurement of surface deformation in unidirectional open-hole compression (OHC) specimens is proposed and investigated as a viable alternative to assessing ILT stress–strain, strength, and fatigue properties. Inverse identification using a finite element model updating (FEMU) method is used for simultaneous measurement of through-thickness elastic constants with recovery of the maximum ILT stress at failure for characterization of strength and fatigue S–N curves. Full article

(This article belongs to the Special Issue Advances in Digital Image Correlation (DIC))

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16 pages, 3817 KiB

Open AccessArticle

Image Classification for Automated Image Cross-Correlation Applications in the Geosciences

by Niccolò Dematteis, Daniele Giordan and Paolo Allasia

Appl. Sci. 2019, 9(11), 2357; https://doi.org/10.3390/app9112357 - 8 Jun 2019

Cited by 11 | Viewed by 3456

Abstract

In Earth Science, image cross-correlation (ICC) can be used to identify the evolution of active processes. However, this technology can be ineffective, because it is sometimes difficult to visualize certain phenomena, and surface roughness can cause shadows. In such instances, manual image selection [...] Read more.

In Earth Science, image cross-correlation (ICC) can be used to identify the evolution of active processes. However, this technology can be ineffective, because it is sometimes difficult to visualize certain phenomena, and surface roughness can cause shadows. In such instances, manual image selection is required to select images that are suitably illuminated, and in which visibility is adequate. This impedes the development of an autonomous system applied to ICC in monitoring applications. In this paper, the uncertainty introduced by the presence of shadows is quantitatively analysed, and a method suitable for ICC applications is proposed: The method automatically selects images, and is based on a supervised classification of images using the support vector machine. According to visual and illumination conditions, the images are divided into three classes: (i) No visibility, (ii) direct illumination and (iii) diffuse illumination. Images belonging to the diffuse illumination class are used in cross-correlation processing. Finally, an operative procedure is presented for applying the automated ICC processing chain in geoscience monitoring applications. Full article

(This article belongs to the Special Issue Advances in Digital Image Correlation (DIC))

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10 pages, 1385 KiB

Open AccessArticle

Gradient Correlation Functions in Digital Image Correlation

by Mikael Sjödahl

Appl. Sci. 2019, 9(10), 2127; https://doi.org/10.3390/app9102127 - 24 May 2019

Cited by 8 | Viewed by 3806

Abstract

The performance of seven different correlation functions applied in Digital Image Correlation has been investigated using simulated and experimentally acquired laser speckle patterns. The correlation functions were constructed as combinations of the pure intensity correlation function, the gradient correlation function and the Hessian [...] Read more.

The performance of seven different correlation functions applied in Digital Image Correlation has been investigated using simulated and experimentally acquired laser speckle patterns. The correlation functions were constructed as combinations of the pure intensity correlation function, the gradient correlation function and the Hessian correlation function, respectively. It was found that the correlation function that was constructed as the product of all three pure correlation functions performed best for the small speckle sizes and large correlation values, respectively. The difference between the different functions disappeared as the speckle size increased and the correlation value dropped. On average, the random error of the combined correlation function was half that of the traditional intensity correlation function within the optimum region. Full article

(This article belongs to the Special Issue Advances in Digital Image Correlation (DIC))

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17 pages, 9484 KiB

Open AccessArticle

Dynamic Response of Copper Plates Subjected to Underwater Impulsive Loading

by Kaida Dai, Han Liu, Pengwan Chen, Baoqiao Guo, Dalin Xiang and Jili Rong

Appl. Sci. 2019, 9(9), 1927; https://doi.org/10.3390/app9091927 - 10 May 2019

Cited by 5 | Viewed by 3339

Abstract

Understanding the mechanical response and failure behaviors of thin plates under impact loading is helpful for the design and improvement of thin plate structures in practical applications. The response of a copper plate subjected to underwater impulsive loading has been studied in fluid-structure [...] Read more.

Understanding the mechanical response and failure behaviors of thin plates under impact loading is helpful for the design and improvement of thin plate structures in practical applications. The response of a copper plate subjected to underwater impulsive loading has been studied in fluid-structure interaction (FSI) experiments. Three typical copper plates, (a) without a pre-notch, (b) with a cross-shaped pre-notch (+), and (c) with a ring-shaped pre-notch (○) were selected. A high-speed photography system recorded the full-field shape and displacement profiles of the specimens in real time. The 3D transient deformation fields’ measurements were obtained using a 3D digital image correlation (DIC) technique. Strain results from DIC and the strain gauges technique were in good agreement. A dimensionless deflection was used to analyze the effect of plate thickness and loading intensity on the deformation of the copper plates. The typical failure modes of different copper plates were identified. The test plates exhibited large ductile deformation (mode

I

) for copper plates without a pre-notch, and large ductile deformation with local necking (mode

I c

), splitting (mode

II

), splitting and tearing (mode

II c

), and fragment (mode

III

) for the copper plate with a pre-notch. Full article

(This article belongs to the Special Issue Advances in Digital Image Correlation (DIC))

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17 pages, 11236 KiB

Open AccessArticle

New Four Points Initialization for Digital Image Correlation in Metal-Sheet Strain Measurements

by Alejandro-Israel Barranco-Gutiérrez, José-Alfredo Padilla-Medina, Francisco J. Perez-Pinal, Juan Prado-Olivares, Saúl Martínez-Díaz and Oscar-Octavio Gutiérrez-Frías

Appl. Sci. 2019, 9(8), 1691; https://doi.org/10.3390/app9081691 - 24 Apr 2019

Cited by 5 | Viewed by 2972

Abstract

Nowadays, the deformation measurement in metal sheets is important for industries such as the automotive and aerospace industries during its mechanical stamping processes. In this sense, Digital Image Correlation (DIC) has become the most relevant measurement technique in the field of experimental mechanics. [...] Read more.

Nowadays, the deformation measurement in metal sheets is important for industries such as the automotive and aerospace industries during its mechanical stamping processes. In this sense, Digital Image Correlation (DIC) has become the most relevant measurement technique in the field of experimental mechanics. This is mainly due to its versatility and low-cost compared with other techniques. However, traditionally, DIC global image registration implemented in software, such as MATLAB 2018, did not find the complete perspective transformation needed successfully and with high precision, because those algorithms use an image registration of the type “afine” or “similarity”, based on a 2D information. Therefore, in this paper, a DIC initialization method is presented to estimate the surface deformation of metal sheets used in the bodywork automotive industry. The method starts with the 3D points reconstruction from a stereoscopic digital camera system. Due to the problem complexity, it is first proposed that the user indicates four points, belonging to reference marks of a “Circle grid”. Following this, an automatic search is performed among the nearby marks, as far as one desires to reconstruct it. After this, the local DIC is used to verify that those are the correct marks. The results show reliability by reason of the high coincidence of marks in experimental cases. We also consider that the quality of mark stamping, lighting, and the initial conditions also contribute to trustworthy effects. Full article

(This article belongs to the Special Issue Advances in Digital Image Correlation (DIC))

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13 pages, 5883 KiB

Open AccessArticle

Application of the Non-Contact Video Gauge on the Mechanical Properties Test for Steel Cable at Elevated Temperature

by Yong Du and Zhang-ming Gou

Appl. Sci. 2019, 9(8), 1670; https://doi.org/10.3390/app9081670 - 23 Apr 2019

Cited by 20 | Viewed by 4099

Abstract

As the limit of traditional contact measurement, it is difficult to precisely measure the steel cables twisted by a branch of wires especially at elevated temperature. In this paper the strain-stress relationships of S355 and S690 structural steel, 1860 MPa steel cable twisted [...] Read more.

As the limit of traditional contact measurement, it is difficult to precisely measure the steel cables twisted by a branch of wires especially at elevated temperature. In this paper the strain-stress relationships of S355 and S690 structural steel, 1860 MPa steel cable twisted by seven wires have been measured by the strain gauge, extensometer and non-contact video gauge at ambient temperature and elevated temperature, respectively. Comparison of the stress-strain curves gotten by different measuring technology, it indicates that the non-contact video gauge can provide a more efficient and reliable database than the strain gauge as well as extensometer, especially at an elevated temperature. It is worth noting that the non-contact video gauge can capture not only the full range of stress-strain curves of steel cables, but is also efficient for the specimens with a complex shape. Full article

(This article belongs to the Special Issue Advances in Digital Image Correlation (DIC))

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17 pages, 3493 KiB

Open AccessArticle

Enhanced Digital Image Correlation Analysis of Ruptures with Enforced Traction Continuity Conditions Across Interfaces

by Yuval Tal, Vito Rubino, Ares J. Rosakis and Nadia Lapusta

Appl. Sci. 2019, 9(8), 1625; https://doi.org/10.3390/app9081625 - 18 Apr 2019

Cited by 14 | Viewed by 3295

Abstract

Accurate measurements of displacements around opening or interfacial shear cracks (shear ruptures) are challenging when digital image correlation (DIC) is used to quantify strain and stress fields around such cracks. This study presents an algorithm to locally adjust the displacements computed by DIC [...] Read more.

Accurate measurements of displacements around opening or interfacial shear cracks (shear ruptures) are challenging when digital image correlation (DIC) is used to quantify strain and stress fields around such cracks. This study presents an algorithm to locally adjust the displacements computed by DIC near frictional interfaces of shear ruptures, in order for the local stress fields to satisfy the continuity of tractions across the interface. In the algorithm, the stresses near the interface are extrapolated by local polynomials that are constructed using a constrained inversion. This inversion is such that the traction continuity (TC) conditions are satisfied at the interface while simultaneously matching the displacements produced by the DIC solution at the pixels closest to the center of the subset, where the DIC fields are more accurate. We apply the algorithm to displacement fields of experimental shear ruptures obtained using a local DIC approach and show that the algorithm produces the desired continuous traction field across the interface. The experimental data are also used to examine the sensitivity of the algorithm against different geometrical parameters related to construction of the polynomials in order to avoid artifacts in the stress field. Full article

(This article belongs to the Special Issue Advances in Digital Image Correlation (DIC))

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19 pages, 9059 KiB

Open AccessArticle

3D Strain Mapping of Opaque Materials Using an Improved Digital Volumetric Speckle Photography Technique with X-Ray Microtomography

by Lingtao Mao, Haizhou Liu, Ying Zhu, Ziyan Zhu, Rui Guo and Fu-pen Chiang

Appl. Sci. 2019, 9(7), 1418; https://doi.org/10.3390/app9071418 - 4 Apr 2019

Cited by 19 | Viewed by 3631

Abstract

Digital volumetric speckle photography (DVSP) method has been used to strain investigation in opaque materials. In this paper, an improved DVSP algorithm is introduced, in which a multi-scale coarse–fine subset calculation process and a subvoxel shifting technique are applied to increase accuracy. We [...] Read more.

Digital volumetric speckle photography (DVSP) method has been used to strain investigation in opaque materials. In this paper, an improved DVSP algorithm is introduced, in which a multi-scale coarse–fine subset calculation process and a subvoxel shifting technique are applied to increase accuracy. We refer to the new algorithm as Multi-scale and Subvoxel shifting Digital Volumetric Speckle Photography (MS-DVSP). The displacement and strain fields of a red sandstone cylinder exposed to uniaxial compression and a woven composite beam under three-point bending are mapped in detail. The characteristics of the interior deformation of the specimens are clearly depicted, thus elucidating the failure mechanism of the materials. Full article

(This article belongs to the Special Issue Advances in Digital Image Correlation (DIC))

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16 pages, 4463 KiB

Open AccessArticle

3D Strain and Elasticity Measurement of Layered Biomaterials by Optical Coherence Elastography based on Digital Volume Correlation and Virtual Fields Method

by Fanchao Meng, Xinya Zhang, Jingbo Wang, Chuanwei Li, Jinlong Chen and Cuiru Sun

Appl. Sci. 2019, 9(7), 1349; https://doi.org/10.3390/app9071349 - 30 Mar 2019

Cited by 17 | Viewed by 3844

Abstract

The three-dimensional (3D) mechanical property characterization of biological tissues is essential for physiological and pathological studies. A digital volume correlation (DVC) and virtual fields method (VFM) based 3D optical coherence elastography (OCE) method is developed to quantitatively measure the 3D full-field displacements, strains [...] Read more.

The three-dimensional (3D) mechanical property characterization of biological tissues is essential for physiological and pathological studies. A digital volume correlation (DVC) and virtual fields method (VFM) based 3D optical coherence elastography (OCE) method is developed to quantitatively measure the 3D full-field displacements, strains and elastic parameters of layered biomaterials assuming the isotropy and homogeneity of each layer. The integrated noise-insensitive DVC method can obtain the 3D strain tensor with an accuracy of 10%. Automatic segmentation of the layered materials is realized based on the full field strain and strain gradient. With the strain tensor as input, and in combination with the segmented geometry, the Young’s modulus and Poison’s ratio of each layer of a double-layered material and a pork specimen are obtained by the VFM. This study provides a powerful experimental method for the differentiation of various components of heterogeneous biomaterials, and for the measurement of biomechanics. Full article

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12 pages, 4350 KiB

Open AccessArticle

Experimental Study on the Fracture Process Zone Characteristics in Concrete Utilizing DIC and AE Methods

by Shuhong Dai, Xiaoli Liu and Kumar Nawnit

Appl. Sci. 2019, 9(7), 1346; https://doi.org/10.3390/app9071346 - 30 Mar 2019

Cited by 49 | Viewed by 4585

Abstract

The present work focuses on investigating the characteristics of the fracture process zone (FPZ) in concrete. The Single-edge notched (SEN) concrete beams under three-points bending are employed for conducting mode I fracture propagation. The displacement fields on the specimen surface and the internal [...] Read more.

The present work focuses on investigating the characteristics of the fracture process zone (FPZ) in concrete. The Single-edge notched (SEN) concrete beams under three-points bending are employed for conducting mode I fracture propagation. The displacement fields on the specimen surface and the internal AE signal of specimen are obtained simultaneously in real time by digital image correlation (DIC) and acoustic emission (AE) techniques. The experimental and analytical results indicated that the crack tip position, the crack extension length and the stress intensity factors (SIF) are obtained dynamically and quantitatively by DIC technique, and the length of FPZ is identified, respectively, by DIC and AE techniques in the crack extension process. The distribution of internal AE events is consistent with that of FPZ identified from surface deformation of specimens. Full article

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15 pages, 2653 KiB

Open AccessArticle

Application of 3D Digital Image Correlation for Development and Validation of FEM Model of Self-Supporting Arch Structures

by Krzysztof Malowany, Artur Piekarczuk, Marcin Malesa, Małgorzata Kujawińska and Przemysław Więch

Appl. Sci. 2019, 9(7), 1305; https://doi.org/10.3390/app9071305 - 28 Mar 2019

Cited by 8 | Viewed by 3775

Abstract

Many building structures, due to a complex geometry and non-linear material properties, are cumbersome to analyze with finite element method (FEM). A good example is a self-supporting arch-shaped steel sheets. Considering the uncommon geometry and material profile of an arch (due to plastic [...] Read more.

Many building structures, due to a complex geometry and non-linear material properties, are cumbersome to analyze with finite element method (FEM). A good example is a self-supporting arch-shaped steel sheets. Considering the uncommon geometry and material profile of an arch (due to plastic deformations, cross section of a trough, a goffer pattern), the local loss of stability can occur in unexpected regions. Therefore, the hybrid experimental-numerical methodology of analysis and optimization of arch structures have been proposed. The methodology is based on three steps of development and validation of a FEM with utilization of a digital image correlation (DIC) method. The experiments are performed by means of 3D DIC systems adopted sequentially for each measurement step conditions from small size sections, through few segment constructions up to full scale in situ objects. Full article

(This article belongs to the Special Issue Advances in Digital Image Correlation (DIC))

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14 pages, 5112 KiB

Open AccessArticle

Laboratory Observations of Repeated Interactions between Ruptures and the Fault Bend Prior to the Overall Stick-Slip Instability Based on a Digital Image Correlation Method

by Yan-Qun Zhuo, Yanshuang Guo and Sergei Alexandrovich Bornyakov

Appl. Sci. 2019, 9(5), 933; https://doi.org/10.3390/app9050933 - 5 Mar 2019

Cited by 4 | Viewed by 2732

Abstract

Fault geometry plays important roles in the evolution of earthquake ruptures. Experimental studies on the spatiotemporal evolution of the ruptures of a fault with geometric bands are important for understanding the effects of the fault bend on the seismogenic process. However, the spatial [...] Read more.

Fault geometry plays important roles in the evolution of earthquake ruptures. Experimental studies on the spatiotemporal evolution of the ruptures of a fault with geometric bands are important for understanding the effects of the fault bend on the seismogenic process. However, the spatial sampling of the traditional point contact type sensors is quite low, which is unable to observe the detailed spatiotemporal evolution of ruptures. In this study, we use a high-speed camera combined with a digital image correlation (DIC) method to observe ruptures during stick-slip motions of a simulated bent fault. Meanwhile, strain gages were also used to test the results of the DIC method. Multiple cycles of the alternative propagation of ruptures between the two fault segments on the both sides of the fault bend were observed prior to the overall failure of the fault. Moreover, the slip velocity and rupture speed were observed getting higher during this process. These results indicate the repeated interactions between the ruptures and the fault bend prior to the overall instability of the fault, which distinguishes the effect of the fault bend from the effect of asperities in straight faults on the evolution of ruptures. In addition, improvement in the temporal sampling rate of the DIC measurement system may further help to unveil the rupture evolution during the overall instability in future. Full article

(This article belongs to the Special Issue Advances in Digital Image Correlation (DIC))

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12 pages, 4306 KiB

Open AccessArticle

A Cross-Dichroic-Prism-Based Multi-Perspective Digital Image Correlation System

by Xizuo Dan, Junrui Li, Qihan Zhao, Fangyuan Sun, Yonghong Wang and Lianxiang Yang

Appl. Sci. 2019, 9(4), 673; https://doi.org/10.3390/app9040673 - 16 Feb 2019

Cited by 10 | Viewed by 4493

Abstract

A robust three-perspective digital image correlation (DIC) system based on a cross dichroic prism and single three charge-coupled device (3CCD) color cameras is proposed in this study. Images from three different perspectives are captured by a 3CCD camera using the cross dichroic prism [...] Read more.

A robust three-perspective digital image correlation (DIC) system based on a cross dichroic prism and single three charge-coupled device (3CCD) color cameras is proposed in this study. Images from three different perspectives are captured by a 3CCD camera using the cross dichroic prism and two planar mirrors. These images are then separated by different CCD channels to perform correlation calculation with an existing multi-camera DIC algorithm. The proposed system is considerably more compact than the conventional multi-camera DIC system. In addition, the proposed system has no loss of spatial resolution compared with the traditional single-camera DIC system. The principle and experimental setup of the proposed system is described in detail, and a series of tests is performed to validate the system. Experimental results show that the proposed system performs well in displacement, morphology, and strain measurement. Full article

(This article belongs to the Special Issue Advances in Digital Image Correlation (DIC))

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10 pages, 4721 KiB

Open AccessArticle

Measurement of Super-Pressure Balloon Deformation with Simplified Digital Image Correlation

by Kazuki Koseki, Takuma Matsuo and Shuichi Arikawa

Appl. Sci. 2018, 8(10), 2009; https://doi.org/10.3390/app8102009 - 22 Oct 2018

Cited by 8 | Viewed by 4261

Abstract

A super pressure balloon (SPB) is an aerostatic balloon that can fly at a constant altitude for an extended period. Japan Aerospace Exploration Agency (JAXA) has been developing a light-weight, high strength balloon made of thin polyethylene films and diamond-shaped net with high [...] Read more.

A super pressure balloon (SPB) is an aerostatic balloon that can fly at a constant altitude for an extended period. Japan Aerospace Exploration Agency (JAXA) has been developing a light-weight, high strength balloon made of thin polyethylene films and diamond-shaped net with high tensile fibers. Previous investigations proved that strength requirements on SPB members are satisfied even though the net covering the SPB sometimes becomes damaged during the inflation test. This may be due to non-uniform expansion, which causes stress concentration, however, no method exists to confirm this hypothesis. In this study, we tested a new method called Simplified Digital Image Correlation method (SiDIC) to check if it can measure the displacement of the SPB by using a rubber balloon. After measuring the measurement accuracy of the Digital Image Correlation method (DIC) and SiDIC, we applied both DIC and SiDIC to a rubber balloon covered just with the net. Interestingly, SiDIC entailed a smaller amount of data but could measure the deformation more accurately than DIC. In addition, assuming the stress concentration, one part of the net was bonded to the balloon to restrict the deformation. SiDIC properly identified the undeformed region. Full article

(This article belongs to the Special Issue Advances in Digital Image Correlation (DIC))

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