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Interfaces have been reported to significantly strengthen and toughen metallic materials. However, there has been a long-standing question on whether interface-affected-zone (IAZ) exists, and how it might behave. Here we report in situ high-resolution strain mapping near interfaces in a copper–bronze heterogeneous laminate, which revealed the existence of IAZs. Defined as the zone with strain gradient, the IAZ was found to form by the dislocations emitted from the interface. The IAZ width remained largely constant with a magnitude of a few micrometers with increasing applied strain. Interfaces produced both back stress strengthening and work hardening, which led to both higher strength and higher ductility with decreasing interface spacing until adjacent IAZs started to overlap, after which a tradeoff between strength and ductility occurred, indicating the existence of an optimum interface spacing for the best mechanical properties. These findings are expected to help with designing laminates and other heterogeneous metals and alloys for superior mechanical properties.

Nanobeam electron diffraction strain mapping has been used to measure the strain evolution in stainless steel under in situ deformation. As the amount of deformation increases, the leading dislocation of a planar slip band leaves behind a residual strain in the form of a small lattice expansion. Dislocation analysis confirmed that the dislocations involved were type. While the characteristic residual strain of planar slip has often been observed, it has never before been directly measured. Our results provide a view into the dynamic mechanisms of planar slip, and showcase the possibilities of multidimensional in situ imaging.

Achilles tendinopathy remains one of the most prevalent overuse injuries in elite as well as recreational athletes. Regardless of the fact that the aetiology of tendinopathy has not been fully understood, therapeutic mechanical loading programs have emerged as being the treatment of choice. In this light, mechanical properties of the tendon and their response to changes in loading or unloading have been the subject of many previous investigations. One of these properties often investigated is strain, a measure of relative deformation. By means of a systematic review, an overview was given of research in this field, with a primary objective to list the methods used and secondary aim to synthesize data on strain mapping in the Achilles tendon. Following the guidelines of the PRISMA statement, 47 articles were found appropriate for qualitative assessment. Achilles tendon strain has been investigated across a variety of contexts, including the response to exercise, walking, unloading, ageing, hormonal changes and weight. Only three studies investigated the effect of the presence of tendinopathy on strain. Ultrasound was the most often used imaging modality to measure or estimate strain. Further methodological parameters, e.g. the location of measurement, differed greatly between all different studies. Nearly all studies considered global strain. Some studies investigated the transverse strain response of the Achilles tendon. Recently, however, the role of local - intratendinous - strain distribution has been found to be of critical importance and further studies should focus on imaging modalities to investigate these local changes.

Inter-pass deformation is an effective method for refining the coarse β-grain structure normally produced in high-deposition-rate additive manufacturing processes, like wire-arc additive manufacturing. The effectiveness of applying contoured surface rolling deformation tracks to each added layer has been studied by developing, and applying, a large-area SEM-based strain mapping technique. This technique is based on calibration of the average point-to-point Local Average Misorientation (LAM) of α-phase lamellar variants in EBSD orientation data to the local effective plastic strain. Although limited in the strain range that can be measured, the technique has proven to be very effective for identifying the size and depth of the plastic zone induced by surface rolling, as well as the local strain distribution, up to a saturation limit of ~12%. The strain fields mapped showed a close correlation to the region and level of recrystallization that occurred in the deformation zones during rapid re-heating through the β transus. The β recrystallization identified was consistent with the local strain distribution within the plastic zones measured by the LAM method and previous work on the recrystallization mechanisms operating in WAAM inter-pass deformation processes.

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.

The analysis by diffraction of polycrystalline materials can determine the full tensor of the elastic strains within them. Point-by-point maps of elastic strain can thus be obtained in fine-grained engineering alloys, typically using synchrotron X-rays or neutrons. In this paper, a novel approach is presented to calculate the elastic strain energy release rate of a loaded crack from two-dimensional strain maps that are obtained by diffraction. The method is based on a Finite Element approach, which uses diffraction data to obtain the parameters required to calculate the J-integral via the contour integral method. The J integral is robust to uncertainties in the crack tip position and to poor definition of the field in the crack vicinity, and does not rely on theoretical assumptions of the field shape. A validation of the technique is presented using a synthetic dataset from a finite element model. Its experimental application is demonstrated in an analysis of a synchrotron X-ray diffraction strain map for a loaded fatigue crack in a bainitic steel.

Cross correlation techniques applied to EBSD patterns have led to what has been termed “high-resolution EBSD” (HR-EBSD). The technique yields higher accuracy orientation and strain data which is obtained by comparing a given EBSD pattern with either a real or a simulated reference pattern. Real reference patterns are often taken from a “central” position in a given grain, where it is hoped that the material is “strain-free”, and they enable the determination of relative changes in orientation and strain from that present in the lattice at the reference position. Simulated patterns, on the other hand, enable comparison of the sample lattice with that of a perfect lattice, resulting in a measure of absolute strain and orientation. However, the simulated pattern method has several drawbacks, including the need to accurately specify microscope geometry, the lower fidelity/detail of simulated patterns compared with real patterns, and the potential for microscope-specific bias in the measured patterns (such as due to optical distortion). These drawbacks have led to much debate about the utility of the cross-correlation technique using simulated patterns. This paper is the first to assess the accuracy of the simulated pattern method relative to the real pattern approach in a setting where accuracy can be reasonably determined, thus providing a fair assessment of the potential of the simulated pattern technique. Based upon recent developments towards a standard material for assessing strain mapping techniques, this paper assesses the overall accuracy of the simulated pattern technique. Mismatch strains are calculated using both the real and simulated pattern techniques for a SiGe film deposited on a Si substrate. While the simulated pattern technique is not as accurate or precise as the real pattern technique for providing relative strains, it provides an estimate of absolute strain that is not available via the real pattern approach.

We proposed a quantitative method to detect atomic position in atomic intensity images from experiments such as high-resolution transmission electron microscopy, atomic force microscopy, and simulation such as phase field crystal modeling. The evaluation of detection accuracy proves the excellent performance of the method. This method provides a chance to precisely determine atomic interactions based on the detected atomic positions from the atomic intensity image, and hence to investigate the related physical, chemical and electrical properties.

A practical framework is developed in this work for extracting high-fidelity quantitative strain information from three-dimensional digital image correlation (3D-DIC) experiments. The framework is applicable for continuum-scale deformation in elastic and plastic regimes in the presence of macroscopic strain gradients. The framework is developed, demonstrated, and validated by conducting 3D-DIC experiments and corresponding finite element analysis (FEA) on polycrystalline aluminum tensile specimens with and without macroscopic strain gradient subjected to uniaxial tensile deformation in both elastic and plastic regimes. The developed framework is expected to be applicable for continuum-scale deformation in other classes of materials.

A procedure for determining three-dimensional grain boundary geometry and its change under external loading is proposed for evaluating crystallographic deformation behaviours in polycrystalline materials, and the feasibility of this approach is confirmed for an aluminium alloy. X-ray microtomography has been combined with gallium-enhanced microscopy, in which grains are visualized in three dimensions by decorating grain boundaries with liquid gallium. Grain boundary particles are then extracted by comparing tomographic images with and without the gallium application. Three-dimensional reconstruction of grains is achieved using a connection scheme based on triplets of non-aligned points on grain boundaries. The deformation of the closed polygonal grains is visualized by combining the above technique with a microstructural tracking technique, in which the paths of particles are reconstructed by matching each pair of particles in consecutive images. This process also enables high-density four-dimensional strain mapping by tracking particles located in grains, providing direct interpretation of localized deformation caused by interaction between neighbouring grains.

Strain mapping using the geometric phase analysis (GPA) technique was applied to Al–GP II (Guinier–Preston) nanoscale precipitates, using both high resolution transmission electron microscopy (HRTEM) micrographs as well as the exit wave function (EWF) obtained by focal series reconstruction. The experimental strain results were compared with strain maps obtained from an atomic model which consisted of an Al supercell containing a GP II precipitate. It was built as a reference from literature data. The experimental results demonstrate a complex strain distribution and larger fluctuations than the reference strain maps. These differences were found to be partly a consequence of image artifacts produced by the technique as well as complex microstructural events which were present at the development stage studied.

Summary Objective To examine the functional behavior of the surface layer of the meniscus by investigating depth-varying compressive strains during unconfined compression. Design Pairs of meniscus and articular cartilage explants ( n =12) site-matched at the tibial surfaces were subjected to equilibrium unconfined compression at 5, 10, 15, and 20% compression under fluorescence imaging. Two-dimensional (2D) deformations were tracked using digital image correlation (DIC). For each specimen, local compressive engineering strains were determined in 200μm layers through the depth of the tissue. In samples with sharp strain transitions, bilinear regressions were used to characterize the surface and interior tissue compressive responses. Results Meniscus and cartilage exhibited distinct depth-dependent strain profiles during unconfined compression. All cartilage explants had elevated compressive engineering strains near the surface, consistent with previous reports. In contrast, half of the meniscus explants tested had substantially stiffer surface layers, as indicated by surface engineering strains that were ∼20% of the applied compression. In the remaining samples, surface and interior engineering strains were comparable. 2D Green's strain maps revealed highly heterogeneous compressive and shear strains throughout the meniscus explants. In cartilage, the maximum shear strain appeared to be localized at 100–250μm beneath the articular surface. Conclusions Meniscus was characterized by highly heterogeneous strains during compression. In contrast to cartilage, which consistently had a compliant surface region, meniscal explants were either substantially stiffer near the surface or had comparable compressive stiffness through the depth. The relatively compliant interior may allow the meniscus to maintain a consistent surface contour while deforming during physiologic loading.

SINQ is a continuous spallation neutron source, driven by PSI's 590 MeV proton accelerator. Receiving a stable proton current of 1.3 mA, SINQ is the presently most powerful accelerator-driven facility worldwide. Besides the primary designation of SINQ to serve as user facility for neutron scattering and neutron imaging, PSI seeks to play a leading role in the development of the facility, focusing on spallation targets and materials research for high-dose radiation environments. Accompanying these activities, SINQ has established several projects serving a more general, profound development towards high-power spallation targets: the most prominent ones being SINQ Target Irradiation Program (STIP) and megawatt pilot experiment for a liquid metal target (MEGAPIE), complemented by LiSoR and VIMOS. Within the user program, SINQ is aspiring to attract an appropriate contingent of industrial applications. The paper highlights the potential for industrial applications by means of selected examples from strain mapping and neutron imaging.

Four fundamental models, based on slip-line theory, are compared to experimental results obtained from deforming scribed billets in a single pass of equal-channel angular pressing (ECAP). Two ECAP die configurations, having sharp and round corners, are used to determine the experimental flow-line fields for Pb, pure Cu and pure Al billets. Two different types of deformation behavior are observed when using the die with a sharp-corner: (a) for the Cu and Al billets a gap develops at the outer corner of the die so that the material flows without filling the outer corner and (b) for Pb billets a “dead-metal” zone is formed which fills with material in the outer corner of the die. Strain mapping is used to delineate different spatial strain distributions for sharp-corner and round-corner dies.

A technique based on high-speed digital photography and image correlation for direct whole-field strain mapping of Portevin–Le Chatelier deformation bands is described. Results for a type B band show that the deformation band was formed within a few milliseconds and remained stationary as no motion of the band was detected.

A strain mapping technique, namely digital photogrammetry, was used to investigate the tensile strain field of woven fabric composites in the presence of stress concentrations caused by geometrical defects consisting of circular or elliptical holes. Plain woven fabrics were used. The strain mapping technique clearly revealed the strain concentrations near the singularity. The strain concentrations are influenced by the tensile loading direction and the hole dimension relative to the size of the unit cell of the plain woven fabrics. A preliminary comparison of stresses approximately calculated from the strain field and theoretical stresses calculated from existing models such as Lekhnitskii’s model is also presented.

The accuracy of strain profiles obtained by a quantitative analysis of lattice fringe spacings from high-resolution micrographs is discussed. Focusing on highly lattice mismatched GaAs/InAs/GaAs heterostructures the local strain distribution of the layers is calculated by finite element simulations to determine the atom positions in elastically relaxed transmission electron microscopy specimens. By analysing simulated images a significant decoupling between the layer structure and the contrast pattern motifs is found for relevant imaging conditions, which may result in an incorrect determination of strain profiles and layer compositions when examining experimental micrographs.

A number of isolated single CVD (chemical vapour deposition) diamond crystals were mapped using confocal Raman microscopy at a spatial resolution of 1 μm. Both square and triangular faceted crystals were included. It was found that, in general, regions of both types of crystals which corresponded to (111) growth sectors showed an overall shift of the diamond peak to low wavenumber, while the regions which corresponded to (100) growth sectors showed a shift to high wavenumber. This is interpreted as deriving from the presence of high concentrations of defects in the (111) growth sectors resulting in an overall tensile strain in these regions, and a compressive stress where these low density regions border the higher quality diamond from (100) growth sectors.

Two-dimensional microcomposites, comprising regular arrays of Kevlar 49 fibres embedded in an epoxy resin, were fabricated and subjected to incremental tensile loading up to fracture. The strain along individual fibres at different levels of applied load was monitored using a laser Raman spectroscopic technique. A strain magnification of 80% maximum was measured in an intact fibre as a result of a fibre fracture in an adjacent fibre. The exact distribution of the strain increase within the transfer length of the broken fibre was obtained. The experimental stress concentration factor is compared with that derived from existing analytical models.

ontributions that were presented at the sixth Size and Strain conference held in Presqu'ile de Giens, France, from 17 to 20 October, 2011. The Size-Strain conference is devoted to the analysis of the microstructure of materials by diffraction. Diffraction (X-rays, neutrons) was recognized very early as a very sensitive tool for analyzing deviations from perfect periodicity in crystals. Indeed, point, line, or planar defects yield distinct signatures in diffraction patterns. In the same way, displacement fields and surfaces induce characteristic features in diffracted intensities. In the field of powder diffraction, Line Profile Analysis (LPA) is an important method to extract microstructural information (size, strain, stacking fault, or dislocation density, etc.) from diffraction lines. More recently, the advent of nanobeams on 3rd generation synchrotrons has opened theway to very local investigations, which go beyond the statistical information given by LPA and bring new insights into the models used for LPA. Coherent X-ray diffraction is also a very promising method, which in the near future should allow strain mapping at the nanoscale. Size-Strain VI is the sixth conference in a series. The previous conferences were held in the following places: 1995 Liptovsky Mikulas (Slovakia), 1998 Freiberg (Germany), 2001 Trento (Italy), 2004 Prague (Czech Republic), and 2007 Garmisch-Partenkirchen (Germany). In close relation to the previous Size-Strain conferences, SS-VI focuses on methodologies for the study of lattice defects, residual stress, and texture in thin films, surfaces, and nanostructures, line-broadening analysis, line-profile fitting, and modeling based on fundamental parameters for applications in materials science problems. Newdevelopments for localmeasurements such asmicrobeam diffraction or coherent diffraction are also of special interest. During the summer of 2011,we received the sad news that Professor Robert Snyder passed away. Bob was a member of our scientific committee and a pioneer of this conference. A special tribute was dedicated to him and his career during the conference. Size-Strain VI gathered 102 attendees from 15 different countries. Sunny weather, a lively atmosphere, and a very good scientific program made this conference a very pleasant experience. Finally, the organizing committee has been instrumental in making things work. We really would like to warmly thank Cathy Paitel, Vanessa Coulet, Stephanie Escoubas, Sophie Girardin, and Stephane Labat for their dedication.Without them, the conference would certainly not have been such a great success.