High Resolution Digital Image Correlation Research Articles

Nanoscale speckle patterning for combined high‐resolution strain and orientation mapping of environmentally sensitive materials

AbstractScanning electron microscopy‐based high‐resolution digital image correlation (HRDIC) is now an established technique, providing full‐field strain and displacement measurement at the microscale. Techniques for generating speckle patterns for sub‐micron strain mapping can often be either substrate dependent or rely on applying aggressive conditions which may alter the microstructure of interest or damage the substrate in highly sensitive materials. We detail a modification of a methodology successfully applied in the literature to allow its use with metallic materials that are particularly sensitive to the corrosive media, such as copper‐base alloys. Nanometre‐thick silver films, applied with physical vapour deposition, are remodelled using NaBr in non‐aqueous isopropanol, replacing the aqueous solution of NaCl in the original method, forming a uniform dispersion of silver islands highly suitable for digital image correlation (DIC) measurement. The entire procedure is performed at ambient temperature. We find that the DIC pattern is suitably electron transparent to allow electron backscatter diffraction (EBSD) measurements without pattern removal, producing diffraction patterns of sufficient quality for cross‐correlation based high‐angular resolution EBSD. This property facilitates simultaneous EBSD and DIC mapping experiments, providing deeper insights into the kinematics of plastic deformation in crystalline materials. Sub‐100 nm islands are achieved through control of the sputter coating parameters, resulting in DIC cross‐correlation subwindows of 140 nm with a 50% overlap. This resolution is sufficient to capture the fine detail of strain localisation phenomena during plastic deformation, demonstrated here with a case study in CuCrZr, a precipitation‐hardened heat sink material for application in nuclear fusion components. Here, we extract full‐field displacement data with DIC and corresponding orientation information using EBSD without the need for pattern removal.

Micro-mechanics investigation of heterogeneous deformation fields and crack initiation driven by the local stored energy density in austenitic stainless steel welded joints

This work investigates the heterogeneous deformation and failure of HR3C austenitic stainless steel welded joints at room and typical service temperatures. Such types of welded joints are widely used in the new generation of fossil fuel power stations and are known to suffer from premature high temperature failure. Observation of in-service failures revealed that cracks may nucleate either in the heat affected zone or in the weld metal. The main objective of this work is to identify the local microstructural conditions and stress–strain fields responsible for both ductile failure and micro-crack nucleation within the weldment at low and high temperatures, respectively. To that purpose, a novel multi-scale micromechanics-based modelling framework is proposed. It relies on representative weld microstructure models digitally reconstructed from electron backscatter diffraction measurements, and dislocation density-based crystal plasticity models to describe the behaviour of individual grains in each weld region. A novel thermo-dynamically consistent relation for the configuration stored energy per unit volume is derived from the crystal plasticity framework.The single crystal models are calibrated and validated from a combination of uniaxial tensile tests on cross-weld specimens using high resolution digital image correlation techniques, representative volume elements of the polycrystals at the macro-scale, as well as micropillar compression tests at the scale of the individual grains. Predictions of heterogeneous inelastic deformation fields within the weldment at both 22 °C and 665 °C, and of micropillar compression behaviour of the individual weld single crystal phases are consistent with experimental data. The experimentally observed ductile failure of the weld metal at room temperature is successfully predicted using a Gurson-type void nucleation, growth and coalescence constitutive model. The suitability of the stored strain energy density and the accumulated plastic strain as crack initiation/creep failure indicators is investigated. It was found that predicted creep lifetimes with either indicator were very similar, and that they were relatively accurate for low stress levels.

Strain partitioning in dual-phase eutectic high-entropy alloy: Dependence on phase boundary morphology

Strain partitioning in dual-phase eutectic high-entropy alloy, AlCoCrFeNi2.1, is investigated under uniaxial tension with in situ high-resolution digital image correlation (DIC) in a scanning electron microscope (SEM). Nanoscale speckles are fabricated on the sample surface. Three regions with different phase morphologies at different applied strains are characterized by SEM for DIC analysis. Strain localization tends to form at softer face-centered cubic (FCC) rather than body-centered cubic phase domains, and the degree of strain localization in a lamellar structure is much lower than in a bimodal structure. Transmission electron microscopy is conducted to characterize the phase interaction at the nanoscale. A straight phase boundary in a lamellar structure allows more geometrically necessary dislocations to pile up at the phase boundary and form a wide interface affected zone (IAZ) in the soft FCC domain. The IAZ strengthens the soft FCC and better accommodates the deformation of the two phases, resulting in a relatively uniform strain partitioning.

Analysis of slip transfer across grain boundaries in Ti via diffraction contrast tomography and high-resolution digital image correlation: When the geometrical criteria are not sufficient

High-resolution digital image correlation was employed to analyze the occurrence of slip transfer across grain boundaries in pure Ti. The microstructure was characterized in 3D through diffraction contrast tomography and electron backscatter diffraction. The prismatic slip activity was captured in the shear strain maps at different strains, and the grain boundaries were classified according to the occurrence/absence of slip transfer. Different geometrical slip transfer criteria were tested, and, in general, the slip transfer likelihood increased when the slip systems across the boundary were well-aligned. Nevertheless, a detailed analysis of selected grain boundaries revealed that slip transfer could be triggered or impeded depending on the local stresses acting on the neighborhood, regardless of the alignment between the slip systems. The microstructural and deformation patterns where the geometrical criteria are not enough to predict slip transfer are assessed.

Strain localization in the Alloy 718 Ni-based superalloy: From room temperature to 650 °C

Irreversible deformation in relation to the microstructure was investigated for a polycrystalline Ni-based superalloy (Alloy 718) from room temperature to 650 °C using high-resolution digital image correlation (HR-DIC) techniques. Interrupted tensile tests were performed under a protective atmosphere to ensure the stability of the speckle pattern to track kinematics fields from surface analyses. In-plane strain localization was captured using HR-DIC on scanning electron microscopy (SEM) images. A statistical analysis of different strain localization events in relation to the microstructural features was conducted, i.e., intragranular slip localization, slip localization parallel to and near Σ3-twin boundaries (Σ3-TB), and grain boundary sliding (GBS). Alloy 718 exhibited slip localization at room temperature and 350 °C. Intense strain localization develops parallel and in the vicinity of Σ3-TB from the onset of the microplasticity. Few intense slip stimulated-grain boundary sliding events were found due to slip localization on both grains adjacent to the grain boundary. At 650 °C, Alloy 718 experienced grain boundary sliding at the onset of the yield without particular slip localization in adjacent grains. At lower temperatures, strain localization parallel to and near Σ3-TB was intense, and intragranular slip localization intensified with increasing macroscopic deformation. Particular microstructural configurations were found at 650 °C leading to premature damage: (i) sub-surface cavitation at grain boundaries, and (ii) grain boundary cracking due to intense shearing near a Σ3-TB.

High‐resolution strain mapping in a thermionic LaB6 scanning electron microscope

AbstractThe high source stability and brightness of field emission gun equipped scanning electron microscopes (SEM) makes them ideal for high‐resolution digital image correlation (HRDIC). However, their high initial capital cost can be prohibitive for research organisations and groups. Conventional thermionic SEMs using either a tungsten hairpin or LaB6 filament are far more widespread due to their lower cost. Whilst it is understood that overall performance and ultimate resolution are lower than field emission SEMs, we propose that there is no fundamental reason why these instruments are unsuitable for HRDIC. We investigate the use of a LaB6 SEM as a viable tool for HRDIC. We detail the subtleties of performing HRDIC using a LaB6 thermionic source SEM, providing technical recommendations for best practices in using these instruments for strain mapping. The effects of instrument parameters on strain measurement noise are examined, with a focus on parameters of key relevance to in situ and ex situ mechanical testing. Errors in focus and image pixel size are found to be the primary contributors to the strain noise floor values, with stage accuracy being of secondary importance. We present a case study in oxygen‐free high‐conductivity copper, OFHC‐Cu, which is used in the designs of nuclear fusion components as a heat sink interlayer. Heterogeneous strain patterns are observed in this material, with high levels of strain localisation at grain boundaries. Active slip systems are identified using the relative displacement ratio method, demonstrating the quality of these data and the suitability of LaB6 instruments for HRDIC strain mapping, achieving performance approaching that expected of a field emission SEM.

Quantifying cracking and strain localisation in a cold spray chromium coating on a zirconium alloy substrate under tensile loading at room temperature

The mechanical and cracking behaviour of a Cr coating, deposited on an Optimized ZIRLOTM substrate using the Cold Spraying (CS) technique, was investigated by in-situ scanning electron microscopy (SEM) tensile testing at room temperature. To achieve this, curved micro-tensile samples were machined from cladding tubes, and a styrene-assisted gold remodelled pattern was applied on the coating surface. The macroscopic crack density of the coating with applied axial strain was quantified through automated SEM image processing, whilst the localisation of strain was monitored with High Resolution Digital Image Correlation (HRDIC). Like with most brittle thin films deposited on ductile substrates, under applied external stress, parallel crack channelling appeared on the coating surface, perpendicular to the loading direction. The first crack was captured at 0.5% axial strain, whilst saturation was observed at 1.5%. Single crack formation in the coating was found to cause relaxation of local strains and redistribution towards the uncracked segment's midpoint. The local fracture strain of the coating was found to increase with the decreasing crack spacing, whilst shear bands appeared on the coating's surface at 35° and 145° with respect to the loading direction, which is evidence of plastic deformation. The crack density of the curved sample geometry was correlated with the tubes using a modified shear-lag model, considering the residual stresses in the coating measured by X-ray Diffraction (XRD). The CS Cr coating showed high levels of bonding and mechanical interlocking with the substrate, even after 3% axial strain.

Micro-strain and cyclic slip accumulation in a polycrystalline nickel-based superalloy

This work provides a comprehensive characterization and analysis of deformation and fatigue damage mechanisms in a nickel-based superalloy during ambient temperature fatigue and points to a fundamental deformation mechanism that results in the onset of crack nucleation. Strain and slip irreversibility are investigated at the nanometer scale using high-resolution digital image correlation and high-resolution electron backscatter diffraction, highlighting distinct deformation mechanisms contributing to crack nucleation. It is observed during early fatigue cycling at relatively low applied stress, the formation of intense slip events that induce grain boundary shearing. This results in intense micro-scale strain in the neighboring grains, producing localized plasticity and stresses. Such stresses facilitate fatigue extrusion–intrusion mechanisms during subsequent cycling, resulting in preferred crack nucleation. Finally, the configurations within the microstructure that promote such deformation and damage mechanisms sequence are highlighted.

High-Resolution Digital Image Correlation Analysis of Layered α/β Two-Phase Ti–12Mo Alloy under Compressive Condition

High-Resolution Digital Image Correlation Analysis of Layered α/β Two-Phase Ti–12Mo Alloy under Compressive Condition

Evolution of in-plane strain fields onset of a plastically deforming crack in zirconium

Understanding the fracture behaviour of a material is essential for the sustainable design of structural components. The complex nature of microscale mechanical testing techniques makes identifying the fracture behaviour experimentally challenging at a microscopic scale. Validating microscale simulations with experimental studies can be difficult using traditional experimental techniques. High-resolution digital image correlation combined with electron backscatter diffraction describes the total in-plane deformation field at a microstructural scale, which can be compared against finite element models for verification. The present study determines the in-plane strain distribution ahead of a plastically deforming crack during an in-situ experiment. A crystal plasticity-based finite element model is used to simulate the experimental crack tip behaviour, after which quantitative and qualitative comparisons are made. A concentration of normal strains ahead of the crack tip is observed in both experimental and simulated results, defining the fracture process zone. Slip localization behaviour around the crack is also evaluated using Schmid factor analysis. A good correlation between the experimental slip bands and theoretical predictions has been observed. The strain path dependence on slip activation is also identified. Strain localization in deforming zirconium is initially limited with dense and low-intensity slip occurring up to a maximum in-plane shear strain of 0.2. Formation of well-defined equidistant slip bands occurs with further deformation. Equidistant slip bands are observed for prismatic <a> and pyramidal <c+a> slip systems, having an interplane distance of ∼0.60±0.05 µm and ∼0.46±0.04 µm, respectively.

The role of strain rate in microstructure evolution, deformation heterogeneity and cracking mode of high-pressure die-casting Al7Si0.2Mg alloy

The quasi-static and dynamic deformation behaviours of high-pressure die-casting (HPDC) Al7Si0.2 Mg alloy were studied in this work. Competing effects among porosities, α-Al(Fe/Mn)Si phase, eutectic phase and α-Al dendrites on strain concentration and crack propagation at different strain rates were investigated using X-ray computed tomography (CT), scanning electron microscopy (SEM), in-situ electron backscattering diffraction (EBSD), and high-resolution digital image correlation (HR-DIC). The results indicate that yield strength and ductility of Al7Si0.2 Mg alloy were improved at high strain rates compare to quasi-static loading. Weak zones, including porosities and particle interfaces, primarily contributed to deformation heterogeneity under quasi-static tension, whereas both weak zones and Al matrix played a role under dynamic loading. Moreover, crack propagation was hardly observed on porosities during dynamic deformation, thereby reducing the sensitivity of ductility to porosity. The slip and rotation of α-Al dendrites became more pronounced during dynamic deformation. As a result, the area fraction of fractured eutectic phase increased dramatically and surpassed the area fraction of α-Al(Fe/Mn)Si phase, which became the dominant factor of crack propagation during dynamic deformation.

Three-dimensional configuration of crystal plasticity in stainless steel assessed by high resolution digital image correlation and confocal microscopy

In polycrystalline austenitic stainless steels, a comprehensive three-dimensional configuration of crystal plasticity in relation to microstructure is required to elucidate the deformation behaviors during mechanical loading. In the present work, a combination of backscattered electron image (BSE) based high-resolution digital image correlation (HR-DIC) and laser scanning confocal microscopy (LSCM) was employed to simultaneously investigate in-plane and out-of-plane deformations at the sub-grain scale in 316 stainless steel. The high spatial resolution and precise alignment provided by the three-dimensional deformation assessment enable the identification of specific slip and twinning systems. This is achieved through the minimization of the residual L2 norm between the in-plane components of experimental and theoretical strain tensors. Dominant slip and few mechanical twinning activities are initiated at the early-stage of yielding, and their frequency and intensity increase with the applied load. The hierarchical networks formed by nanotwins, along with the presence of grain and annealing twin boundaries, serve as obstacles for slip glide, leading to substantial twin–slip interaction and grain boundary strengthening. As a consequence of wide mechanical twins formed by parallel nanotwins coalescence and strain localization at the twin boundary, slip transmission occurs, resulting in an effective accommodation of external stress. Furthermore, the consistent observation of out-of-plane roughness, in alignment with twinning Burgers vector predictions, offers valuable insights into the significant deformation gradient occurring in the vicinity of boundaries. This deformation gradient is influenced by the neighboring mechanical twinning activities, indicating strong obstacle to twin transmission and high back-stresses resulting from the highly misoriented grain boundary.

Exploring the hydride-slip interaction in zirconium alloys

Hydrogen pick-up and hydride precipitation can lead to embrittlement and fracture strength reduction of nuclear fuel cladding tubes made of Zircaloy. Plastic deformation of hydride packets and its interaction with local plasticity in the zirconium matrix is a key linkage of microstructure feature to structural integrity of hydrided polycrystalline bulk Zircaloy. This work focuses on explicit representation of hydride packets from high spatial resolution electron backscatter diffraction onto a crystal plasticity finite element model for capturing and understanding slip localisation near hydride-matrix phase boundaries, based on the extracted material property of hydrides. The mechanisms behind slip evolution including slip nucleation, slip transfer, and slip inhibition are studied by combined high-resolution digital image correlation and crystal plasticity results. Through assessing various slip transfer parameters, new slip transfer criterion is proposed for α/δ phase boundaries. Prior to slip transfer criterion, local micromechanical quantities, specifically shear stress and stored energy density, are necessary to drive and provide pathway for subsequent slip transfer at α/δ phase boundaries.

Revealing the effect of misorientation on the deformation behavior of a Mg-Y alloy from the perspective of local strain

The addition of rare earth (RE) elements in magnesium alloys may significantly enhance the ductility of magnesium alloys, which is generally attributed to the decrease of stacking fault energy, the reduced critical resolved shear stress (CRSS) differences among different deformation modes and the weakening of basal texture. Rare earth elements also change the misorientation between adjacent grains of magnesium alloy, whose effects on the deformation behavior and thus the ductility of magnesium alloy were not emphasized before. In this work, ex-situ high-resolution digital image correlation (HR-DIC) coupled with electron backscatter diffraction (EBSD) was used to reveal the effect of the misorientation on the deformation behavior of a Mg-Y binary alloy from the perspective of local strain. It is shown that the heterogeneity of local strain is largely dependent on the misorientation between adjacent grains. For the intergranular deformation, three scenarios are observed, namely strain transfer, strain concentration and suppressed deformation, which mainly occurs at low misorientation, moderate misorientation and high misorientation, respectively. In addition, much more non-basal slip is found to be activated near the grain boundaries with moderate misorientation angles due to the high geometric compatibility factor (m’B-Pr/Py), which is favorable for the intergranular deformation compatibility, thus reducing the strain concentration near grain boundaries and achieving high ductility. For the intragranular deformation, a wide range of misorientation between adjacent grains in the Mg-Y alloy causes multiple basal slip systems to be activated within a grain, which also facilitates work hardening, thus contributing to improving ductility. Therefore, tailoring the misorientation between adjacent grains may be an effective way to improve the ductility of magnesium alloys.

The role of hydrides and precipitates on the strain localisation behaviour in a zirconium alloy

In service, zirconium alloys undergo aqueous corrosion and hydrogen is absorbed, which can lead to the formation of hydrides. Hydrides, as well as the precipitates in zirconium alloys, affect the mechanical performance, though their contribution to plasticity is not yet well understood. This study uses a combination of high-resolution digital image correlation and electron backscatter diffraction to quantify the strain partitioning between the different phases. Following uniaxial tensile deformation, it was found that the average strain within the δ-ZrH and Zr(Fe,Cr)2 was lower than in the α-Zr. Shear bands in the α-Zr matrix were observed to interact with small and medium sized hydride in multiple ways, such as terminating at the interface, cracking and shear around the interface or causing plastic slip in the hydride. Large hydrides showed a particularly detrimental effect on deformation behavior, with large strain localizations and cracking observed at interfaces, which are typically precursors to failure. In contrast, the Zr(Fe,Cr)2 precipitates remained undeformed and forced the expected metal-matrix lattice rotation. The importance of these observations in context of fuel cladding integrity is discussed.

Role of gradient heterogeneous interfaces in synergetic strengthening and toughening of layered CuCrZr/Cu composites

Layered CuCrZr/Cu composites with different densities of gradient heterogeneous interfaces were designed and prepared by powder metallurgy combined with rolling and aging. The prepared layered CuCrZr/Cu composites achieved better comprehensive properties than the homogeneous CuCrZr alloy. The evolution of local strain was analyzed by high resolution digital image correlation (DIC). A strain-transfer from CuCrZr layer to adjacent Cu layers appears at the gradient heterogeneous interface, which relieves the strain localization of CuCrZr layers in layered CuCrZr/Cu composites. The incompatible deformation between the gradient heterogeneous microstructures across the layer interface leads to the generation and accumulation of geometrically necessary dislocations (GNDs), which results in extra work hardening and hetero-deformation induced (HDI) strengthening. The increase in the density of gradient heterogeneous interfaces can enhance the interface constraint behavior and produce a greater HDI strengthening effect, which tends to improve the work hardening ability and HDI stress of layered CuCrZr/Cu composites. Furthermore, various crack propagation modes of crack deflection, multiple cracks and crack blunting caused by uneven stress/strain partition at the gradient heterogeneous interface of layered CuCrZr/Cu composites were characterized by in-situ tensile tests.

Study on the semi-circular bend method for characterizing the mixed mode I/II fracture toughness of sandstone: A micro-perspective

Manufacturing and precracking specimens for semi-circular bend (SCB) tests are simple processes and do not require complicated loading devices. They have been used to conduct mode I, mode II and mixed mode I/II fracture tests on brittle materials. However, characterizing mode I and mode II fractures from a microcosmic and quantitative perspective has never been thoroughly evaluated. In this paper, high-resolution digital image correlation (DIC) and moment tensor inversion are first used to quantitatively measure micron-level displacement and analyse microfailure types. The DIC results indicate that SCB specimens with a notch inclination angle exhibit both opening displacement and sliding displacement, resulting in a mixed mode I/II fracture. A quantitative analysis of three typical classification methods based on moment tensor inversion suggests that SCB specimens with mixed loads are mainly tensile mechanisms. Some tensile sources are not pure tensile cracks, and shear components also play an important role. It is also observed that the moment tensor components, nature of sources and Hudson k value are associated with the notch inclination angle, which sheds new light on the mechanism of mixed mode I/II fractures.

INTERFERENCE AND KEEL DESIGN SIGNIFICANTLY INFLUENCE SAGITTAL MICROMOTION IN CEMENTLESS UNICOMPARTMENTAL KNEE ARTHROPLASTY

AbstractIntroductionIn cementless UKR, early post-operative tibial fractures are 7x more common in very small tibias. A smaller keel has been shown to reduce this fracture risk, but its effect on fixation is unassessed. This mechanical study assesses the effect of keel interference and size on sagittal micromotion of the tibial component in physiological loading positions.MethodA high-resolution Digital Image Correlation setup was developed and validated to an accuracy of 50 micrometres. Variants of tibial components were 3D-printed: standard, no-interference, no-keel, and a new small keel. Components were implanted into bone-analogue foam which was machined to a CT-reconstructed small tibia, using surgical technique. Tibias were loaded to 200N in physiological loading positions: 8mm (step-up) and 15mm (lunge) posterior to midpoint, and micromotion was assessed.ResultsIn all tests, anterior lift-off was the largest micromotion observed. In ‘step-up’, a standard keel moved more than the no-interference and no-keel variants (340μm-vs-63μm-vs-30μm, p=0.002). In ‘lunge’ loading, the no-interference and no-keel variants moved more than the standard (826μm-vs-1003μm-vs-521μm, p=0.039).The small keel experienced less micromotion in ‘step-up’ (245μm-vs-340μm p=0.233, overall p=0.009) and ‘lunge’ (378μm-vs-521μm p=0.265, overall p=0.006) than the standard keel.ConclusionThe keel protects against large tibial micromotion during lunge movement. Counterintuitively, interference increases micromotion during step-up movement, likely due to implant pivoting around the bone-keel interface. Results suggest patients should be advised against lunge movements early post-operatively. The new smaller keel fixes similarly or better than the standard keel, making it viable for replacing the standard keel to potentially reduce fracture risk.

Effect of micro-texture and orientation incompatibility on the mechanical properties of Ti60 alloy

In this work, the effects of no-micro-texture regions (no-MTR, weak texture) and strong-MTR on the mechanical properties of Ti60 alloy engine blisk materials were investigated. It has been shown that MTR has a small effect on the room temperature strength of the alloy, but strongly affects plasticity, which reaches 18.5% for no-MTR alloy is twice as high as for MTR alloy. In contrast to no-MTR alloys, MTR alloys have only two-stage strain hardening behavior and fracture before meeting the instability criterion. Based on digital image correlation (DIC), high-resolution DIC and in-situ tensile analyses show that no-MTR alloys produce more uniform strains in deformation than MTR alloy. MTR exacerbates the slip deformation and local strain inhomogeneity in the hardening stage. Prevent premature fracture by eliminating MTR, thereby substantially increasing no-MTR alloy plasticity and triggering excellent work-hardening ability due to the uniformity of local deformation and dislocation multiplication. Meanwhile, the unique deformation characteristics of the combination of (0001) and (10 1‾ 0) soft orientations are proposed and elucidated. The incompatibility of the two orientations causes stronger slip deformation incompatibility, resulting in local strains and dislocation slips clustered mainly at the grain or MTR boundaries of the (0001) and (101‾ 0) soft orientation features, which further exacerbates the alloy failure at the microscopic level.

Crystal Plasticity simulations of in situ tensile tests: A two-step inverse method for identification of CP parameters, and assessment of CPFEM capabilities

As the computational capability of modern computers increases, the Crystal Plasticity Finite Element Method (CPFEM) becomes more and more popular in materials science to model the mechanical behaviour of polycrystals. Indeed, such analysis provides extensive information about local mechanical fields (such as plastic strain and stress), which can be useful for understanding the behaviour of bulk materials. However, estimating the parameters of the CP constitutive laws is still challenging because they are not directly related to the macroscopic behaviour of the polycrystalline aggregates. Thus, one way to identify such parameters is by inverse analysis from CPFEM simulations. However, such approach is usually extremely time consuming. This paper proposes a two-step optimization scheme to determine these coefficients. The first step is based on a simple model, similar to that proposed by Sachs back in 1928. The second step is based on CPFEM simulations, to be compared with experimental data acquired by an in situ tensile test and full-field measurements made by High-Resolution Digital Image Correlation (HRDIC). The uniqueness of the solution found by inverse analysis is studied and ways to solve the local minima issues are provided. Finally, the ability of CPFEM to replicate an in situ tensile test is assessed.