scholarly journals Nondestructive Monitoring Techniques for Crack Detection and Localization in RC Elements

2020 ◽  
Vol 10 (9) ◽  
pp. 3248 ◽  
Author(s):  
Marco Domaneschi ◽  
Gianni Niccolini ◽  
Giuseppe Lacidogna ◽  
Gian Paolo Cimellaro
Keyword(s):  
Crack Detection ◽  
Visual Observation ◽  
Image Correlation ◽  
Bending Test ◽  
Nondestructive Monitoring ◽  
Integrated Monitoring ◽  
Four Point Bending ◽  
Initiation And Propagation ◽  
Detection And Localization ◽  
Good Agreement

This paper presents the structural and damage assessment of a reinforced concrete (RC) beam subjected to a four-point bending test until yielding of reinforcing steel. The deterioration progress was monitored using different nondestructive testing (NDT) techniques. The strain was measured by distributed fiber optic sensors (FOSs), embedded prior to concrete pouring. The initiation and propagation of cracks were monitored by acoustic emission (AE) sensors attached to the surface of the material. The recorded AE activity results in good agreement with FOS strain measurements. The results of the integrated monitoring system are confirmed by visual observation of the actual crack pattern. At different loading steps, digital image correlation (DIC) analysis was also conducted.

scholarly journals Modeling of Bimodular Bone Specimen under Four-Point Bending Fatigue Loading

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 474
Author(s):  
Yufan Yan ◽  
Xianjia Meng ◽  
Chuanyong Qu
Keyword(s):  
Compressive Strain ◽  
Fatigue Loading ◽  
Degradation Process ◽  
Neutral Axis ◽  
Image Correlation ◽  
Bending Test ◽  
Correlation Technique ◽  
Fatigue Process ◽  
Four Point Bending ◽  
Bone Properties

The fatigue damage behavior of bone has attracted significant attention in both the mechanical and orthopedic fields. However, due to the complex and hierarchical structure of bone, describing the damage process quantitively or qualitatively is still a significant challenge for researchers in this area. In this study, a nonlinear bi-modulus gradient model was proposed to quantify the neutral axis skewing under fatigue load in a four-point bending test. The digital image correlation technique was used to analyze the tensile and compressive strains during the fatigue process. The results showed that the compressive strain demonstrated an obvious two-stage ascending behavior, whereas the tensile strain revealed a slow upward progression during the fatigue process. Subsequently, a theoretical model was proposed to describe the degradation process of the elastic modulus and the movement of the neutral axis. The changes in the bone properties were determined using the FEM method based on the newly developed model. The results obtained from two different methods exhibited a good degree of consistency. The results obtained in this study are of help in terms of effectively exploring the damage evolution of the bone materials.

Modeling of Deformation and Fracture of Concrete Structures with FRP Reinforcement

2015 ◽  
Vol 752-753 ◽  
pp. 685-688
Author(s):  
Andrey Benin ◽  
S.G. Semenov ◽  
Artem S. Semenov
Keyword(s):  
Image Correlation ◽  
Bending Test ◽  
Four Point Bending ◽  
Reinforced Plastic ◽  
Deformation And Fracture ◽  
Different Types ◽  
Loading Case ◽  
Frp Reinforcement ◽  
Four Point Bending Test ◽  
Frp Bars

Carrying capacity and fracture modes of concrete beams reinforced by different types of fiber reinforced plastic (FRP) bars are analyzed experimentally and numerically. The four-point-bending test is used as a typical loading case for this purpose. Synchronous registration of loading level, displacements and strains is performed by using InstronTM servohydraulic machine, LVDT sensors, strain gauges and digital image correlation Vic3DTM system. The experimental data and results of finite element simulations are compared and discussed.

scholarly journals In Situ Scanning Electron Microscopy Observation of Crack Initiation and Propagation in Hydroxide Films Formed by Steam Coating on Aluminum-Alloy Sheets

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1238
Author(s):  
Hongmei Li ◽  
Naoki Takata ◽  
Makoto Kobashi ◽  
Ai Serizawa
Keyword(s):  
Crack Initiation ◽  
Amorphous Layer ◽  
Image Correlation ◽  
Bending Test ◽  
Al Alloy ◽  
Crack Initiation And Propagation ◽  
Surface Normal ◽  
Initiation And Propagation ◽  
Hydroxide Film

Hydroxide film was formed on 6061 Al-alloy (Al-1.00Mg-0.62Si(wt.%)) sheets by steam coating with the temperature of 220 °C for 24 h. During bending test of the coated specimens, the crack initiation and propagation processes in the hydroxide film were investigated using in situ SEM observations. The hydroxide film formed exhibited a dual-layer structure composed of an inner amorphous layer and an outer polycrystalline γ-AlO(OH)-phase layer. On the compressively strained surface, lateral cracks are preferentially initiated inside the inner amorphous layer, and propagate either inside this layer or on its interface with the outer γ-AlO(OH) layer. Digital image correlation analyses of the in situ observed SEM images suggested that the concentrated tensile strain along the surface normal localized at some parts of the amorphous layer could contribute to the crack initiation. On the tensile-strained surface, a number of cracks were initiated inside the inner amorphous layer along the surface normal and propagate into the outer γ-AlO(OH) layer. No cracks were found along the interface of the amorphous layer with the Al-alloy substrate. As a result, the anticorrosion hydroxide film adhered on the Al sheet after bending deformation. Such strong adhesion contributes to the excellent corrosion resistance of the Al-alloy parts provided by the steam coating.

scholarly journals Detection and Measurement of Matrix Discontinuities in UHPFRC by Means of Distributed Fiber Optics Sensing

Sensors ◽  
2020 ◽  
Vol 20 (14) ◽  
pp. 3883
Author(s):  
Bartłomiej Sawicki ◽  
Antoine Bassil ◽  
Eugen Brühwiler ◽  
Xavier Chapeleau ◽  
Dominique Leduc
Keyword(s):  
Fiber Optics ◽  
Health Monitoring ◽  
High Performance ◽  
Crack Detection ◽  
Measurement Techniques ◽  
Image Correlation ◽  
High Performance Fiber ◽  
Industrial Use ◽  
Opening And Closing ◽  
Detection And Localization

Following the significant improvement in their properties during the last decade, Distributed Fiber Optics sensing (DFOs) techniques are nowadays implemented for industrial use in the context of Structural Health Monitoring (SHM). While these techniques have formed an undeniable asset for the health monitoring of concrete structures, their performance should be validated for novel structural materials including Ultra High Performance Fiber Reinforced Cementitious composites (UHPFRC). In this study, a full scale UHPFRC beam was instrumented with DFOs, Digital Image Correlation (DIC) and extensometers. The performances of these three measurement techniques in terms of strain measurement as well as crack detection and localization are compared. A method for the measurement of opening and closing of localized fictitious cracks in UHPFRC using the Optical Backscattering Reflectometry (OBR) technique is verified. Moreover, the use of correct combination of DFO sensors allows precise detection of microcracks as well as monitoring of fictitious cracks’ opening. The recommendations regarding use of various SHM methods for UHPFRC structures are given.

scholarly journals Detection of Multiple Cracks in Four-Point Bending Tests Using the Coda Wave Interferometry Method

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 1986 ◽  
Author(s):  
Xin Wang ◽  
Joyraj Chakraborty ◽  
Antoine Bassil ◽  
Ernst Niederleithinger
Keyword(s):  
Fiber Optics ◽  
Large Scale ◽  
Early Stage ◽  
Image Correlation ◽  
Bending Test ◽  
Coda Wave ◽  
Multiple Cracks ◽  
Rc Structures ◽  
Four Point Bending ◽  
Coda Wave Interferometry

The enlargement of the cracks outside the permitted dimension is one of the main causes for the reduction of service life of Reinforced Concrete (RC) structures. Cracks can develop due to many causes such as dynamic or static load. When tensile stress exceeds the tensile strength of RC, cracks appear. Traditional techniques have limitations in early stage damage detection and localisation, especially on large-scale structures. The ultrasonic Coda Wave Interferometry (CWI) method using diffuse waves is one of the most promising methods to detect subtle changes in heterogeneous materials, such as concrete. In this paper, the assessment of the CWI method applied for multiple cracks opening detection on two specimens based on four-point bending test is presented. Both beams were monitored using a limited number of embedded Ultrasonic (US) transducers as well as other transducers and techniques (e.g., Digital Image Correlation (DIC), LVDT sensors, strain gauges, and Fiber Optics Sensor (FOS)). Results show that strain change and crack formation are successfully and efficiently detected by CWI method even earlier than by the other techniques. The CWI technique using embedded US transducers is undoubtedly a feasible, efficient, and promising method for long-term monitoring on real infrastructure.

Mechanical Properties of Fiber Reinforced Lime-Based Mortars Evaluated from Four-Point Bending Test

2016 ◽  
Vol 821 ◽  
pp. 526-531
Author(s):  
Michal Přinosil ◽  
Petr Kabele
Keyword(s):  
Thermal Effects ◽  
High Performance ◽  
Correlation Method ◽  
Image Correlation ◽  
Bending Test ◽  
Fiber Reinforced ◽  
Four Point Bending ◽  
High Performance Fiber ◽  
Bending Behavior ◽  
Four Point Bending Test

In the study, the bending behavior of high-performance fiber reinforced lime-based mortars is experimentally investigated using four-point bending test. From the experimental data, the influence of the mortar’s composition on its stiffness, cracking strength and ultimate strength are investigated. It is also studied, whether the response has strain-softening or strain-hardening character and whether the material exhibits multiple cracking. Such behavior is very important for the durability of the material, because it allows carrying load during imposed deformations (due to thermal effects, movements of foundations, seismicity, etc.). The number of formed cracks is examined using digital image correlation method. The mortar composition is considered with two types of binder (pure lime, lime-metakaolin), with two types of polyvinyl alcohol fibers in four volume fractions (0.5÷2.0%). As the reference, we consider two sets of specimens made of plain mortar without fiber reinforcement.

Inverse characterisation of gradient distribution of the modulus of bamboo using a four-point bending test

Holzforschung ◽  
2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Xianzhi Gao ◽  
Guangyan Liu ◽  
Lu Wang ◽  
Yanan Yi ◽  
Guang Lin ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Model Updating ◽  
Volume Fraction ◽  
Image Correlation ◽  
Bending Test ◽  
Uniaxial Tensile ◽  
Gradient Distribution ◽  
Outer Skin ◽  
Four Point Bending ◽  
Four Point Bending Test

AbstractAs a natural graded material, bamboo has gradually increasing elastic modulus along the radial direction from the inner to the outer skin. Accurate measurement of the modulus distribution plays an important role in bamboo-based structural design. However, it is difficult to characterise this modulus distribution by using conventional testing approaches on bamboo slices. A more effective method was developed in this study for the inverse identification of gradually varying material properties. The method is based on the digital image correlation and finite element model updating techniques. The radial distribution of the elastic modulus of bamboo was obtained through only one four-point bending test. The inversely identified modulus distribution was verified through uniaxial tensile tests on sliced bamboo strips and microscopic observation of the volume fraction distribution of its vascular bundle. The results showed that the elastic modulus of the bamboo material decreased from the outer skin (20 GPa) to the inner skin (2 GPa), which is in good consistence with the tensile test results on sliced specimens.

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