scholarly journals Modular Test Stand for Fatigue Testing of Aeronautical Structures – Verification of Assumptions

2020 ◽  
Vol 2020 (12) ◽  
pp. 78-91
Author(s):  
Andrzej Leski ◽  
Wojciech Wronicz ◽  
Piotr Kowalczyk ◽  
Michał Szmidt ◽  
Robert Klewicki ◽  
...  
Keyword(s):  
Strain Gauge ◽  
Fatigue Testing ◽  
Local Buckling ◽  
Test Stand ◽  
Image Correlation ◽  
Design Stage ◽  
Strain Gauges ◽  
Complex Load ◽  
Assumed Strain ◽  
Skin Panels

Abstract The Modular Test Stand was developed and manufactured to decrease the cost of fatigue testing and reduce the time of its completion as well as to enable testing specimens under more complex load conditions. The stand consists of three connected sections, similar to a wing box, all being loaded in the same way. Thanks to that, several specimens can be tested simultaneously. This configuration requires that stress and strain distribution should be reasonably uniform, as assumed in the design stage. The structure can be loaded with bending or torsion. A whole section, selected structural node or a specimen mounted in the structure as well as a repair or a sensor can be a test object. Two stands, one for bending and one for torsion were prepared. This paper presents the verification of the assumed strain and stress distributions on the skin panels. The measurements were performed with the use of Digital Image Correlation (DIC) as well as strain gauges. DIC measurements were performed on one skin panel of the central section. Five strain gauge rosettes were installed on both panels of the one section. In addition, one rosette was applied to one skin panel in each of two other sections. Measurements were performed on the stand for torsion as well as on the stand for bending. The results of DIC analysis and strain gauge measurement during torsion show uniform shearing strain distributions on the panels. During bending, on the tensioned side, the strains obtained indicate quite uniform strain distributions. On the compressed side, local buckling of the skin panels results in high strain gradients. Strain levels obtained with the use of a DIC analysis and strain gauge measurements were similar. Moreover, horizontal displacements of markers in the spar axis during bending was determined based on a series of photographic. The deflection line obtained in this way has a shape similar to arc, which is characteristic of the constant bending moment. The stand was tested with torsional and bending loads in order to verify the design assumptions. The results of strain distributions on the skin panels with the use of DIC and strain gauges as well as the deflection line of the spar axis indicate that the Modular Test Stand performs as assumed and can be used for tests.

scholarly journals DIC (Digital Image Correlation) method in the research of RC beams strengthened with PBO-FRCM materials

2019 ◽  
Vol 97 ◽  
pp. 03008 ◽  
Author(s):  
Dorota Marcinczak ◽  
Tomasz Trapko
Keyword(s):  
Composite Materials ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Strain Gauge ◽  
Concrete Beam ◽  
Correlation Method ◽  
Reinforced Concrete Beam ◽  
Image Correlation ◽  
Strain Gauges ◽  
Reference Image

The article presents tests of a reinforced concrete beam strengthened in a shear with PBO-FRCM composite materials. Measurement of the deformation of the composite was carried out using two methods - with strain gauges and the optical DIC method (Digital Image Correlation). The DIC method consists in taking a series of photographs of the tested object before and during loading. The surface of the tested element must have randomly spaced spots that are applied to the object before measurement. During the study, the cameras monitor the shifting of spots against each other, which in comparison to the reference image before loading gives information about strains and stresses of the tested element. Measurements of deformation of composite materials using strain gauges are difficult to clearly analyse, because the strain gauge is in a specific, limited place, which does not correspond to the work of the entire composite. In addition, the strain gauge tends to break at the place of crack. The article discusses this problem by presenting the results of deformation of PBO-FRCM composite meshes measured in two mentioned ways, their comparison and discussion of results.

Metoda DIC

BUILDER ◽  
2019 ◽  
Vol 259 (2) ◽  
pp. 66-68
Author(s):  
Dorota Marcińczak
Keyword(s):  
Composite Materials ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Strain Gauge ◽  
Concrete Beam ◽  
Correlation Method ◽  
Reinforced Concrete Beam ◽  
Image Correlation ◽  
Strain Gauges ◽  
Reference Image

DIC (DIGITAL IMAGE CORRELATION) METHOD IN THE RESEARCH OF RC BEAMS STRENGTHENED WITH PBOFRCM MATERIALS. The article presents tests of a reinforced concrete beam strengthened in a shear with PBO-FRCM composite materials. Measurement of the deformation of the composite was carried out using two methods - with strain gauges and the optical DIC method (Digital Image Correlation). The DIC method consists in taking a series of photographs of the tested object before and during loading. The surface of the tested element must have randomly spaced spots that are applied to the object before measurement. During the study, the cameras monitor the shifting of spots against each other, which in comparison to the reference image before loading gives information about strains and stresses of the tested element. Measurements of deformation of composite materials using strain gauges are difficult to clearly analyze, because the strain gauge is in a specific, limited place, which does not correspond to the work of the entire composite. In addition, the strain gauge tends to break at the place of crack. The article discusses this problem by presenting the results of deformation of PBO-FRCM composite meshes measured in two mentioned ways, their comparison and discussion of results.

scholarly journals Comparison of Resistive and Optical Strain Measurement for Early Fracture Detection

2020 ◽  
Vol 6 (3) ◽  
pp. 196-199
Author(s):  
Alina Carabello ◽  
Constanze Neupetsch ◽  
Michael Werner ◽  
Christian Rotsch ◽  
Welf-Guntram Drossel ◽  
...  
Keyword(s):  
Surgical Training ◽  
Error Detection ◽  
Strain Measurement ◽  
Testing Machine ◽  
Image Correlation ◽  
Strain Gauges ◽  
Measurement Technology ◽  
Bone Surface ◽  
Fracture Detection ◽  
Local Strains

AbstractTo increase learning success in surgical training, physical simulators are supplemented by measurement technology to generate and record objective feedback and error detection. An opportunity to detect fractures following hip stem implantation early can be measurement of occurring strains on bone surface. These strains can be determined while using strain gauges, digital image correlation (DIC) or photoelasticity. In this research strain gauges and DIC were compared regarding their suitability as strain measurement tools for use in physical simulators. Therefore a testing method was described to replicate the implantation of a hip stem. Testing devices modelled on a realistic prosthesis were pressed into prepared porcine femora in a two-step procedure with a material testing machine. The local strains occurring on bone surface were determined using an optical measurement system for DIC and strain gauges. The initial fractures in the tested femora are located medial-anterior in most cases (73,6%). With increasing indentation depth of the test device, the strains on bone surface increase. Comparing the local strains determined by DIC and strain gauges consistencies in curves are noticeable. Maximal determined strains before fracturing amount to 0,69% with strain gauges and 0,75% with DIC. In the range of the fracture gap, strain gradients are determined by using DIC. However the detected surfaces are of low quality caused by gaps and motion artefacts. The results show strains on bone surfaces for early fracture detection are measurable with strain gauges and DIC. DIC is assessed as less suitable compared to strain gauges. Furthermore strain gauges have greater level of integration and economic efficiency, so they are preferred the use in surgical training simulators.

Optical strain measurements on fast moving fiber reinforced polymer rotors using diffraction gratings

2019 ◽  
Vol 86 (3) ◽  
pp. 175-183
Author(s):  
Julian Lich ◽  
Tino Wollmann ◽  
Angelos Filippatos ◽  
Maik Gude ◽  
Robert Kuschmierz ◽  
...  
Keyword(s):  
Rigid Body ◽  
Strain Measurement ◽  
Composite Structures ◽  
Dynamical Behavior ◽  
Image Correlation ◽  
Fiber Reinforced Polymers ◽  
Strain Gauges ◽  
Objective Lens ◽  
Fiber Reinforced ◽  
Body Movements

AbstractIn-situ measurements of the deformation and of the structural dynamical behavior of moving composite structures, such as rotors made of glass fiber reinforced polymers (GFRP), are necessary in order to validate newly developed simulation models. Local methods like strain gauges and fiber Bragg gratings lack spatial resolution, while contactless optical methods like image correlation or speckle interferometry suffer from noise effects in the presence of fast rigid body movements. A novel compact sensor – based on the diffraction grating method – is introduced for spatially and temporally resolved strain measurement. The use of a line camera allows the measurement of vibrations up to several tens of kHz. With a scanning movement, strain fields at submillimeter resolution can be recorded. The use of two diffraction orders and an objective lens reduces cross sensitivities to rigid body movements on the strain measurement by two to three orders of magnitude. A validation on a GFRP probe was conducted in a quasi-static tensile test with an optical extensometer up to 14500 µϵ. Furthermore, a strain measurement on a moving rotor at surface speeds up to 75 m/s was performed and the results were compared with those of strain gauges as a gold standard. The statistical standard deviation was around 10 µϵ and independent of the rotational speed.

scholarly journals Numerical Modeling and Digital Image Correlation Strain Measurements of Coated Metal Sheets Submitted to Large Bending Deformation

2013 ◽  
Vol 554-557 ◽  
pp. 2424-2431
Author(s):  
Laurent Duchêne ◽  
Amine Ben Bettaieb ◽  
Victor Tuninetti ◽  
Anne Marie Habraken
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Shell Element ◽  
Numerical Results ◽  
Image Correlation ◽  
Integration Scheme ◽  
Forming Process ◽  
Coated Metal ◽  
Assumed Strain ◽  
Assumed Natural Strain

The recently developed SSH3D solid-shell element [1], which is based on the Enhanced Assumed Strain (EAS) and the Assumed Natural Strain (ANS) techniques, is utilized for the modeling of a severe bending sheet forming process. To improve the element's ability to capture the through thickness gradients, a specific integration scheme was developed. In this paper, the performances of this element for the modeling of the T-bent process were assessed thanks to comparison between experimental and numerical results in terms of the strain field at the outer surface of the sheet. The experimental results were obtained by Digital Image Correlation. It is shown that a qualitative agreement between experimental and numerical results is obtained but some numerical parameters should be optimized to improve the accuracy of the simulation predictions. In this respect, the influence of the penalty coefficient of the contact modeling was analyzed.

Optimum Strain Gauge Application to Bladed Assemblies

2002 ◽  
Author(s):  
J. Szwedowicz ◽  
S. M. Senn ◽  
R. S. Abhari
Keyword(s):  
Strain Gauge ◽  
Element Model ◽  
Strain Gauges ◽  
Structural Components ◽  
Algorithm Optimization ◽  
Rotating Blades ◽  
Novel Approach ◽  
Present Technique ◽  
Optimization Function ◽  
Rotating Impeller

Optimum placements of the strain gauges assure reliable vibration measurements of structural components such as rotating blades. Within the framework of cyclic vibration theory, a novel approach has been developed for computation of the optimum gauge positions on tuned bladed discs regarding the determined sensitivity, orthogonality, gradient and distance criteria. The utilized genetic algorithm optimization tool allows for an effective numerical search of suitable solutions of the defined optimization function. A rotating impeller disc represented by a cyclic finite element model demonstrates the application of this method. The present technique can be easily applied to other structural components requiring optimal strain gauge instrumentation.

DESTRUCTIVE METHODS FOR DETERMINING RESIDUAL STRESSES (review)

2021 ◽  
pp. 95-104
Author(s):  
A.D. Monakhov ◽  
◽  
N.O. Yakovlev ◽  
V.V. Avtaev ◽  
E.A. Kotova ◽  
...  
Keyword(s):  
Digital Image Correlation ◽  
Residual Stresses ◽  
Speckle Interferometry ◽  
Image Correlation ◽  
Strain Gauges ◽  
Contact Method ◽  
Layer By Layer ◽  
Deep Hole ◽  
Destructive Methods

The paper presents an overview of methods for determining residual stresses. Methods such as splitting and segmentation, layer-by-layer removal, slitting (cutting, pliability), profiling, drilling holes (including a «deep» hole) are considered. The description of the methods for mea-suring the deformation used in the determination of residual stresses is given. The most common contact method using strain gauges, as well as non-contact methods: polarization-optical (photo-elasticity), optical speckle interferometry, digital image correlation.

Repeatability and Extended Time Stability Study of an Additively Printed Strain Gauge Under Different Load Conditions

2021 ◽  
Author(s):  
Pradeep Lall ◽  
Jinesh Narangaparambil ◽  
Tony Thomas ◽  
Kyle Schulze
Keyword(s):  
Strain Gauge ◽  
Printed Electronics ◽  
Performance Testing ◽  
Temperature Limit ◽  
Stability Study ◽  
Strain Gauges ◽  
Gauge Factor ◽  
Wearable Electronics ◽  
Strain Sensing ◽  
Sintering Conditions

Abstract Printed electronics has found new applications in wearable electronics owing to the opportunities for integration, and the ability of sustaining folding, flexing and twisting. Continuous monitoring necessitates the production of sensors, which include temperature, humidity, sweat, and strain sensors. In this paper, a process study was performed on the FR4 board while taking into account multiple printing parameters for the direct-write system. The process parameters include ink pressure, print speed, and stand-off height, as well as their effect on the trace profile and print consistency using white light interferometry analysis. The printed traces have also been studied for different sintering conditions while keeping the FR4 board’s temperature limit in mind. The paper also discusses the effect of sintering conditions on mechanical and electrical properties, specifically shear load to failure and resistivity. The data from this was then used to print strain gauges and compared them to commercially available strain gauges. By reporting the gauge factor, the printed strain gauge has been standardized. The conductive ink’s strain sensing capabilities will be studied under tensile cyclic loading (3-point bending) at various strain rates and maximum strains. Long-term performance testing will be carried out using cyclic tensile loads.

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