Digital image correlation (DIC) techniques have been widely used for experimentally characterizing the mechanical behavior of polymer materials. However, practical applications of DIC for tensile ...testing of polymers often face serious image decorrelation caused by crazing and excessive deformation. In this work, a fluorescent three-dimensional digital image correlation (3D-DIC) with an adaptive incremental calculation strategy is proposed to realize reliable large deformation measurement of polymers by eliminating or mitigating the image decorrelation caused by these issues. The proposed technique first utilizes fluorescent 3D-DIC to eliminate image decorrelation caused by the crazing effect. Then, an adaptive incremental calculation strategy that can automatically update reference images is adopted to mitigate image decorrelation due to excessive deformation. The effectiveness and practicality of the proposed technique were demonstrated by measuring the full-field deformation in chloroprene rubber samples subjected to large tensile deformation. Also, the proposed method was applied to investigate the mechanical behavior of a specific waterproof coating material. Experimental results indicate that the combination of fluorescent 3D-DIC and adaptive incremental calculation strategy can effectively address image decorrelation problems in large deformations of polymers, yielding high-accuracy displacement and strain measurements. This technique holds potential for broader applications in studying the mechanical behavior of other materials or structures undergoing large or super-large deformations.
•Propose a fluorescent 3D-DIC with an adaptive incremental calculation strategy to measure large deformations in polymers.•Fluorescent stereovision imaging effectively avoids decorrelation problem caused by "crazing" in strained polymers.•Adaptive incremental calculation strategy mitigates image decorrelation problem caused by large deformation.
The unique geologic features of raised ridges and polygonal cracks filled with multiple layers of cement observed in Gale and Jezero craters on Mars have origins that remain uncertain due to limited ...knowledge and measurement techniques. This study hypothesizes that these cracks result from the volumetric shrinkage of clay fabric due to dehydration and salinity fluctuations in ancient Martian lakes. The research aims to quantify the shrinkage of terrestrial simulants with varying mineral compositions analogous to those found at Gale Crater and Jezero Crater under diverse desiccation conditions. By simulating Martian regolith using the Rocknest soil simulant and examining historical aqueous conditions through sedimentary rock analogs, this study provides new insights into Martian geological structures. The extent and rate of shrinkage in simulant samples were quantified using ImageJ, while strain localization and propagation were measured using the Digital Image Correlation (DIC) technique until full desiccation crack patterns developed. Laboratory testing revealed that desiccation cracks tend to form polygonal patterns, which are patently similar to the polygonal patterns observed in some regions of Mars. However, not all simulants produced visible cracks, with some producing linear rather than polygonal patterns. Key findings indicate that higher temperatures result in wider and deeper cracks, while lower temperatures decrease crack density and length. Increased initial water content leads to more extensive cracking, with higher crack density and length per unit area. Sodium chloride and sodium sulfate significantly impact desiccation cracking, with low concentrations stabilizing the soil and high concentrations promoting extensive cracking. Smectite-rich samples exhibit extensive cracking, and tensile strain distribution during evaporation is non-uniform, influencing crack development based on sample properties and drying conditions. These insights enhance our understanding of polygonal crack formation on Mars, improving Mars sample return missions and informing the design of robust exploration equipment.
•The study designed a specialized setup to mimic desiccation on Mars and study crack growth in Martian regolith simulants.•Physical and tensile properties of simulants were monitored using ImageJ and DIC setup combined with desiccation test.•Laboratory testing revealed polygonal crack patterns like those found on Mars, providing new insights for Mars missions.
•Fracture characteristics in concrete members have been investigated using DIC technique.•Both monotonic and fatigue loading have been considered.•A systematic approach has been proposed to determine ...the size of fracture process zone in concrete.•DIC measurements has been used to predict fracture parameters accurately.
In this work, an attempt has been made to understand the evolution of fracture process zone in plain concrete member utilizing Digital Image Correlation (DIC) technique. Series of experiments have been performed in centre point bending under the action of monotonic and repetitive loadings and DIC technique is used during the entire test process. A systematic procedure has been developed to monitor the evolution and propagation of the fracture process zone and traction free crack. Size of fully developed FPZ has been found to be approximately equal in both static and fatigue loading cases. It has been also seen that traction free crack propagation has occurred only in medium and large size beams. DIC analysis results have been compared with the measured CMOD values through validation study and both are found to be in good agreement. An analysis has been performed for evaluating the resolution and standard uncertainty in the DIC measured displacements and strains.
This paper presents a mixed numerical–experimental method for the identification of the four in-plane orthotropic engineering constants of composite plate materials. A biaxial tensile test is ...performed on a cruciform test specimen. The heterogeneous displacement field is observed by a CCD camera and measured by a digital image correlation (DIC) technique. The measured displacement field and the subsequently computed strain field are compared with a finite element simulation of the same experiment. The four independent engineering constants are unknown parameters in the finite element model. Starting from an initial value, these parameters are updated till the computed strain field matches the experimental strain field. Two specimen geometries are used: one with a centered hole to increase the strain heterogeneity and one without a hole. It is found that the non-perforated specimen yields the most accurate results.
The damage tolerance of Carbon Fibre Reinforced Polymer (CFRP) to Barely Visible Impact Damage (BVID) is a critical design limiter for composite structures. This study investigated the key driving ...mechanisms and damage evolution of the compressive failure of laminated composites containing BVID using compression after impact and indentation (CAI) tests. Experiments were carried out on two similar quasi-isotropic laminates: 452/902/02/−4522S and 45/90/0/−454S. Matrix cracking and delaminations were introduced by either low-velocity impact or quasi-static indentation tests prior to the CAI tests. The full-field displacement during CAI as well as the moment of rupture was captured by 3D Digital Image Correlation (DIC). The effect of ply-blocking and influence of factors, such as impact energy, delamination area and surface indentation, on compressive failure was studied. Previously validated high-fidelity finite element (FE) numerical models for the indentation and impact events were then used to investigate the damage evolution during CAI failure.
•The impact of MWCNT on properties of regular and high-performance concrete was tested.•Self-sensing as stress detection in regular and HP concrete was compared using cyclic compression.•Crack ...detection was evaluated by combining wedge splitting test with digital image correlation.•The MWCNT addition enhanced stress detection and enabled microcracking detection.
Concrete is the worldwide most utilized construction material because of its very good performance, forming ability, long-term durability, and low costs. Concrete is a brittle material prone to cracking. Extensive cracking may impact durability and performance over time considerably. The addition of a small amount of carbon nanotubes (CNT) increases the concrete’s overall electrical conductivity, enabling internal structure condition monitoring (self-sensing). This article presents the mechanical and self-sensing properties of regular and high-performance concrete (HPC) with multi-wall carbon nanotubes (MWCNT). The stress detection was investigated in cyclic compression, while damage detection was assessed by means of wedge splitting tests combined with the digital image correlation (DIC) method. The results proved that a small addition of MWCNT (0.05% and 0.10%) enhances the stress detection capabilities and enables the monitoring of microcracking.
•Effectiveness of digital image correlation method for determining the deflection of reinforced concrete beams.•A proposed model to evaluate the correlation between crack width and deflection of ...reinforced concrete beams, idealizing the curvature distribution and considering the shear contribution to the deflection.•A linear relationship between the sum of crack widths and the deflection of reinforced concrete beams depending on reinforcement ratio and concrete cover thickness.•Simplified serviceability evaluation based on the sum of crack width data without requiring the concept of effective moment of inertia.
An experimental study was conducted to investigate the correlation between crack propagation and deflection of reinforced concrete beams. A four-point loading test was performed on specimens having varying reinforcement ratios and concrete cover thicknesses. Digital image correlation (DIC) and traditional measuring instruments were used to evaluate and compare the deflection and crack width results. The DIC method accurately measured the deflection and single crack width progression. However, the total crack width was overestimated owing to elastic deformation. The experimental data revealed a linear relationship between the sum of the crack widths and the deflection of beams. Curvature idealization was utilized to propose a model that estimates the deflection based on the crack width measurements obtained by using the DIC method for serviceability evaluation. The results of the proposed model were comparable with the experimental results; the maximum error between them was 8.35%. The proposed model simplified the serviceability evaluation for deflection.
•The projection points tracking method for motion-induced error reduction is proposed.•The digital image correlation method is introduced to fringe projection profilometry.•Fringe patterns for 3D ...shape measurement are corrected at sub-pixel level.
Fringe projection profilometry is a significant method for three-dimensional measurement due to its non-contact and high accuracy. However, the motion-induced error will lead to the loss of measurement accuracy in dynamic scenes due to the disruption of the phase measurement process. In this paper, we introduce a novel motion error model that considers object motion causes the misalignment of the projection points on the camera, and propose the projection points tracking method to reduce the motion-induced error. First, the speckle pattern is added to projection sequences, after which the projection point displacements are determined using the digital image correlation (DIC) method between the adjacent speckle patterns. Finally, the fringe patterns are corrected using the image remapping method to calculate the 3D shape. Quantitative analysis and dynamic measurement experiments verify the feasibility of the proposed method. Different from 3D-DIC, we use one camera-projector system to realize high-accuracy measurement in dynamic scenes.
For the determination of the shear properties such as strength, strain and modulus of unidirectionally reinforced composites, nearly a dozen measurement techniques exist, several of which have found ...their way into standards. One non-standardized method for sheet materials is the 10° off-axis tensile test of unidirectional coupons. The current work focuses on the experimental investigation of tensile testing of CFRP-UD coupon specimens using the 10° off-axis test and DIC strain mapping to measure the full-field deformation response. A sensitivity analysis on the measured stresses, strains and moduli is performed by varying the aspect ratio of the specimens and the location of strain measurement. Test related uncertainties such as the loading angle and specimen preparation details are investigated and quantified with the help of these full-field DIC measurements.
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