This work presents results from oedometric compression of coarse granular material. Coarse granular media exhibit significant deformations making it complicated to predict the settlement of structures. In this paper, a measurement technique was developed for the analysis of two‐dimensional (2‐D) images of a deforming coarse granular medium to investigate its deformation. This was achieved by realising

Cumulative plastic damage caused during the low cycle fatigue (LCF) regime may seriously undermine the safety of the steel members and even lead to serious industrial accidents. Magnetic memory method (MMM), as a novel nondestructive testing technology, has been developed to evaluate the fatigue damage for the ferromagnetic material, but there is the lack of a quantitative description exists for the

The dynamic compression deformation of an in‐house cast concrete (average aggregate size of 2–2.5 mm) was modelled using the finite element (FE), element‐free Galerkin (EFG) and smooth particle Galerkin (SPG) methods to determine their capabilities of capturing the dynamic deformation. The numerical results were validated with those of the experimental split Hopkinson pressure bar tests. Both EFG and

In order to demonstrate the safety of engineered barriers for radwaste geological repositories, rich characterisations of bentonite hydro‐mechanical behaviour are essential. X‐ray computed tomography was used as the single input to measure both the full displacement field and water content in a heterogeneous bentonite sample resaturated in quasi‐isochoric conditions. Since large texture changes do

No abstract is available for this article.

Concrete has a tendency to spall, that is, to eject layers when subjected to high temperatures. This is an erratic phenomenon, and our understanding of the underlying physical process is still limited. A driving process is moisture transfer, whose experimental investigation has so far mostly been limited to macroscopic or point‐wise observations, limiting both our understanding and the validation of

The image‐based inertial impact (IBII) test has shown promise for measuring properties of composites at strain rates where existing test methods become unreliable due to inertial effects (> 102 s−1). Typically, the IBII tests are performed with a single camera, and therefore, to use surface measurements for material property identification, it is necessary to assume that the test is two‐dimensional

No abstract is available for this article.

Full‐field optical measurements like digital image correlation or the grid method have brought a paradigm shift in the experimental mechanics community. While inverse identification techniques like finite element model updating or the virtual fields method have been the object of significant developments, current test methods, inherited from the age of strain gauges or linear variable displacement

Response of dry stack stone masonry walls under mechanical loading is complex and difficult to determine, mainly due to heterogeneous and discrete nature of the components of the stone wall. In this paper, reflection photoelasticity is used on scaled down models of stone masonry wall under uniaxial compression. Two walls are tested, and the methods to obtain near perfect dry stack masonry for reflection

The ability to characterise residual stress distribution accurately and over different length scales, particularly deep into an engineering part, plays a significant role in assessing structural integrity. Two most commonly used techniques to measure residual stress fields deep into engineering components include neutron diffraction (ND) and deep‐hole drilling (DHD). As the measurements depend on several

No abstract is available for this article.

In this paper, the use of the virtual fields method for the identification of a strongly asymmetric compression–tension response of rock‐like materials under dynamic tensile loading is investigated. The photomechanical spalling set‐up is used, which induces an indirect tensile load in a non‐balanced sample, and the inertial component of the test is directly related to the measured dynamic stress with

This paper proposes an approach to defining the path of a curved crack in a single‐edge notched specimen with gray level residuals extracted from digital image correlation, followed by the calibration of the parameters of a cohesive zone model. Only the experimental force is used in the cost function minimized via finite element model updating. The displacement and gray level residual fields allow

Deformation of a weldment is governed by the mechanical properties of its base metals and fusion zone. In a weldment, the base metals and fusion zone exhibit changing microstructural features with various phases present along the weldment. Specifically, the heat affected zone of a base metal exhibits a heterogeneous microstructure generated during weld thermal cycles and by post‐weld heat treatment

We present a new approach to assess the two‐dimensional motion of rigid bodies in granular materials. Although it was adapted from digital image correlation technique, the heart of the presented technique relies on specific treatments related to the discrete nature of grain‐displacement fields. The code called Tracker has been developed to process the digital images and measure the in‐plane displacement

In order to study the residual stress induced by foreign object damage (FOD), the distribution of residual stress caused by the impact of a hard spherical body was measured via the sin2ψ technique, using synchrotron X‐ray. A steel sphere was impacted onto a flat surface of a Ti‐6Al‐4V alloy from an angle of either 90° or 45°, at a velocity of 180 m/s. The same sphere was also quasi‐statically pressed

For the protection of a fragile optical fibre with a fibre Bragg grating (FBG) sensor, the encapsulating method of embedding the FBG sensor in a longitudinal groove set in the central wire of the steel strand is presented. According to the theoretical analysis of the strain transfer and sensing capacity between the embedded FBG sensor and substrate, the requirements for the cross‐sectional size of

Design codes include serviceability limit state (SLS) provisions for stress, crack, and deflection control in concrete structures, which may limit the structural design. When drawing on reinforced ultra‐high performance fibre‐reinforced concrete (R‐UHPFRC), the process of cracking differs significantly from traditional concretes. Thus, it remains unclear whether the traditional provisions are applicable

An energy‐based spherical indentation (ESI) model according to equivalent energy principle is developed to determine the stress–strain relation, tensile strength and hardness of steels. Several parameters in the model are determined with finite element analysis (FEA). For a wide range of homogeneous and isotropic materials in power stress–strain law, a large number of FEA calculations are carried out

Peening processes can be used as a fatigue enhancement treatment for metallic structures by locally introducing compressive residual stresses. A combined experimental–numerical study on a single‐impact process with a drop tower on the aluminium alloy AA5754, representing the elementary process of mechanical peening, has been performed to investigate different impact parameters on the residual stress

No abstract is available for this article.

Clay fine soils are characterised by an ability to change volume when subjected to suction. Soil cracking due to desiccation is a phenomenon of great importance in the environmental geotechnical engineering domain. Aiming to understand shrinkage mechanism, and conditions that lead to appearance of drying cracks, a new experimental testing coupled device digital image correlation‐ clay ring test (DIC‐CRT)

Measuring accurate deformation distribution of large‐scale structures inexpensively and efficiently is a crucial challenge of structural health monitoring. Phase‐based imaging technique has great potential for accurate and robust multipoint displacement measurement in the field. In this study, the sampling Moiré method—one of the promising optical techniques—was applied to the displacement measurement

Particle image velocimetry (PIV), or digital image correlation (DIC), is a widely used technique to measure soil displacements and strains in small‐scale geotechnical models. Arrays of single‐board computers (SBCs) produced by Raspberry Pi, and their associated 8‐MP cameras, are being used at the University of Cambridge to capture the images required for DIC analysis. This alternative to more expensive

Full‐field data from digital image correlation (DIC) provide rich information for finite‐element analysis (FEA) validation. However, there are several inherent inconsistencies between FEA and DIC data that must be rectified before meaningful, quantitative comparisons can be made, including strain formulations, coordinate systems, data locations, strain calculation algorithms, spatial resolutions and

The problem of thermal and shrinkage cracking in concrete has been long recognised by researchers and engineers as it can jeopardise the intended serviceability of a concrete structure. This has led researchers to develop testing devices which aim to simulate the behaviour of concrete under restrained deformations. Such devices are discerned in passive and active, depending on how concrete's movement

This study reports on the Heaviside‐based digital image correlation (H‐DIC) procedure and its application in fracture analysis. This improved DIC procedure was proposed to solve the uncertainty problems at the vicinity of the crack and to evaluate the opening and shear movements of crack lips and the orientations of cracks in the subset. Some tests were conducted to demonstrate the performance of the

This paper introduces a method for dynamic 3D registration of female pelvic organs using 2D dynamic magnetic‐resonance images (MRIs). The aim is to provide a better knowledge and understanding of pathologies such as prolapsus or abnormal mobility of tissues. 2D dynamic MRI sequences are commonly used in nowadays clinical routines in order to evaluate the dynamic of organs, but due to the limited view

For the last decades, new reparation or fabrication processes have been studied to replace traditional rebar by roving of different mineral or organic fibres to avoid corrosion issues. Such materials refer to the family of cementitious composite. Their tensile strength would directly depend on the proportion of reinforcement and strongly on the interfacial mechanical properties between fibres and cementitious

Two‐dimensional digital image correlation (2D‐DIC) is an experimental technique used to measure in‐plane displacement of a test specimen. Real‐time measurement of full‐field displacement data is challenging due to enormous computational load of the algorithm. In order to improve the computational speed, the focus of recent research works has been on the approach of parallelization across subsets within

One main limitation of conventional digital image correlation (DIC) methods is their incapacity to treat with large, discontinuous displacements. This paper seeks to resolve this issue using a variational method. Specifically, the objective function is written in a form of L1‐norm instead of L2‐norm for discontinuity preservation. This convex, non‐differentiable objective function is resolved by a

A new automated digital image‐based method for tracking both the position and shape of the crack front of delaminations in translucent glass fibre‐laminated test specimens is proposed. The method is applicable to both fracture toughness tests and fatigue tests. The digital image‐based algorithm identifies the newly formed crack area by the change in reflected light and then extracts both the crack

No abstract is available for this article.

The goal of this study is to characterise the piezoresistive capabilities of self‐sensory carbon roving reinforcements by means of integrative gauge factors (GFs). The correlation between the measured integrative electrical resistance of the carbon rovings and the distributed strain is experimentally investigated by two different textile reinforced concrete beams under monotonic flexural loading. Because

The identification of crack growth models requires the knowledge of the crack path geometry and, in particular, of the crack tip position. The objective of the present paper is to provide a criterion for the detection of the crack tip position regardless of the loading conditions or the material behavior. The novelty of the proposed approach is its ability to provide a good estimation of the crack

The measurement error of the finite‐element‐based Digital Image Correlation is reduced along the borders of an object by using the precise measurement, obtained by Virtual Image Correlation (VIC). The proposed method is called Virtual and Digital Image Correlation (VDIC). The boundary, identified by the VIC with a subpixel precision, is used firstly to create an adapted mesh and secondly to create

Diffraction of high‐energy X‐rays produced at synchrotron sources can provide rapid strain measurements, with high spatial resolution, and good penetrating power. With an uncollimated diffracted beam, through‐thickness averages of strain can be measured using this technique, which poses an associated rich tomography problem. This paper proposes a Gaussian process (GP) model for three‐dimensional strain

No abstract is available for this article.

The application of digital image and volume correlation techniques to obtain displacement fields from images has become ubiquitous in experimental fracture mechanics. In this paper, a procedure to extract the J‐integral (J) from three‐dimensional displacement fields obtained using digital volume correlation is presented. The procedure has been specially adapted to allow for experimental noise and errors

In this paper, a new inverse identification method of constitutive parameters is developed from full kinematic and thermal field measurements. It consists in reconstructing the heat source field from two different approaches by using the heat diffusion equation. The first one requires the temperature field measurement and the value of the thermophysical parameters. The second one is based on the kinematic

Optical measurements from high‐speed, high‐definition video recordings can be used to define the full‐field dynamics of a structure. By comparing the dynamic responses resulting from both damaged and undamaged elements, structural health monitoring can be carried out, similarly as with mounted transducers. Unlike the physical sensors, which provide point‐wise measurements and a limited number of output

The study presented in this paper aims to adapt and calibrate two strain measurement techniques used for textile reinforced cementitious matrix composites (TRCMCs): distributed optical fibres and 2D digital image correlation (DIC). These composites exhibit tensile behaviour characterised by a succession of transverse cracks along specimens. During the tensile test, out‐of‐plane parasitic displacements

No abstract is available for this article.

Biaxial tests are commonly used to investigate the mechanical behaviour of anisotropic soft biological tissues such as cardiovascular tissues. However, there is still no clear understanding of the influence that the biaxial test set‐up conditions may have on the computing material stress of the experimental results. The aim of the present study is to further investigate the accuracy of calculated material

Digital image correlation (DIC) is more and more popular to monitor fatigue crack growth and to determine the stress intensity factors. However, the posttreatment of the recorded displacement fields becomes tricky when the crack faces are not stress‐free and when crack tip plasticity becomes significant. Several posttreatment methods to locate the crack tip and measure the effective stress intensity

The strain path may change in actual sheet metal‐forming processes, so the determination of formability of sheet metal should consider the nonlinear strain path. For identifying the forming limit (FL) strains under nonlinear strain path, a conventional two‐step procedure with unloading is classically used to produce the strain path change, which results in no continuous measure of strain. The in‐plane

No abstract is available for this article.

Stereo correlation in digital image correlation (DIC) involves an optimisation problem that is sensitive to initial guess. In practice, this problem is circumvented by manually selecting a pair of points in the two stereo images that guarantees convergence and provides stereo mapping parameter estimates that are used as initial guesses at neighbouring subsets. However, such an approach is not always

Digital image correlation (DIC) is of vital importance in the field of experimental mechanics, yet producing suitable DIC patterns for demanding in‐situ (micro)mechanical tests remains challenging, especially for ultrafine patterns, despite the large number of patterning techniques reported in the literature. Therefore, we propose a simple, flexible, one‐step technique (only requiring a conventional

Several recent methods for tomographic reconstruction of stress and strain fields from Bragg‐edge neutron strain images have been proposed in the literature. This paper presents an extension of a previously demonstrated approach based on Gaussian process regression that enforces equilibrium in the method. This extension incorporates knowledge of boundary conditions, primarily boundary tractions, into

With the development of image processing technology, optical methods based on fringe patterns, for example, the grid method, electronic speckle pattern interferometry, moiré techniques (including moiré interferometry and digital moiré), and coherent gradient sensing, have become useful techniques for measuring the full‐field deformation of materials and structures. An important application of these

A single‐camera special stereo‐DIC (SS‐DIC) is proposed for accurate virtual fields method (VFM) identification. The single‐camera SS‐DIC allows accurate surface 3D deformation measurements using a single colour camera and a specially designed colour separation device. It not only effectively eliminates the unavoidable out‐of‐plane movement/rotation due to unideal in‐plane loading but also delivers

In this research, the correlation between the stress concentration and the residual magnetic field (RMF) of 30Cr steel was investigated. Tensile tests were carried out to measure the RMF signals on the surface of U‐shaped defect specimens. It was found that the tangential RMF signal at the defect area is correlated to the applied load and the stress concentration factor. A new method based on magnetic

No abstract is available for this article.

The main cause of failure of the hip acetabular component is aseptic loosening. Preclinical test methods currently used to assess the stability of hip acetabular implants rely on crude simplifications. Normally, either one component of motion or bone strains are measured. We developed a test method to measure implant 3D translations and rotations and bone strains using digital image correlation. Hemipelvises

A novel method for measuring and calculating volumetric strain in circular cylindrical uniaxial tension samples made from polymeric materials is proposed. It is shown that special considerations must be taken when calculating volumetric strain when a sample is in a postnecking state. Solely based on surface data, the key feature of the proposed correction is that it allows for an inhomogeneous distribution

The fatigue life of aerospace components depends greatly on the mechanical properties of the finished surface layer. However, no independent strength test of this layer has been reported because of the lack of suitable samples. Therefore, a direct method of assessing the surface tensile strength using film samples with thicknesses of approximately 40 μm is proposed in this paper. The immediate objective

To investigate the mechanical properties, damage characteristics, and fracturing behaviour of specimens with a cavity formed by intersecting excavations, a series of uniaxial compression tests were conducted incorporating digital image correlation (DIC) and acoustic emission (AE) techniques. PFC2D modelling was conducted to further study the failure modes and crack evolution under biaxial loading.

Standard material parameters identification strategies for constitutive equations generally use an extensive number of classical tests for collecting the required experimental data. Recently, new specimen geometries for heterogeneous tests were designed to enhance the richness of the strain field and capture supplementary strain states using full‐field measurement techniques. The butterfly specimen