Head of Laboratory
Korsunsky, Alexander M
Publications
558
Citations
9 917
h-index
50
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Multi-laboratory collaborative research
- Small-angle X-ray scattering
- X-ray microtomography
- X-ray spectroscopy using synchrotron radiation
Alexander Korsunsky
Head of Laboratory
Research directions
Residual stress across the scales
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FIB-DIC micro-ring core drilling
Publications and patents
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Csüllög M., Korsunsky A.M., Liem N.Q., Hakim L.
Fujiwara A., Otrosh Y., Korsunsky A.M., Kaloop M.
Midani M., Liem N.Q., Hakim L., Korsunsky A.M.
Bazhenov V.E., Li A.V., Rogachev S.O., Bazlov A.I., Statnik E.S., Tavolzhanskii S.A., Komissarov A.A., Redko N.A., Korsunsky A.M., Shin K.S.
Uzun F., Daisenberger D., Liogas K., Wang Z.I., Chen J., Besnard C., Korsunsky A.M.
Polycrystalline diffraction is a robust methodology employed to assess elastic strain within crystalline components. The Extended Caking (exCaking) method represents a progression of this methodology beyond the conventional azimuthal segmentation (Caking) method for the quantification of elastic strains using Debye–Scherrer 2D X-ray diffraction rings. The proposed method is based on the premise that each complete diffraction ring contains comprehensive information about the complete elastic strain variation in the plane normal to the incident beam, which allows for the introduction of a novel algorithm that analyses Debye–Scherrer rings with complete angular variation using ellipse geometry, ensuring accuracy even for small eccentricity values and offering greater accuracy overall. The console application of the exCaking method allows for the accurate analysis of polycrystalline X-ray diffraction data according to the up-to-date rules presented in the project repository. This study presents both numerical and empirical examinations and error analysis to substantiate the method’s reliability and accuracy. A specific validation case study is also presented to analyze the distribution of residual elastic strains in terms of force balance in a Ti-6Al-4V titanium alloy bar plastically deformed by four-point bending.
Song X., Korsunsky A.M., Jia G., Le Bourhis E., Lunt A.J., Nguyen G.D., Sebastiani M., Zhai W.
Soyama H., Wong K.L., Eakins D., Korsunsky A.M.
This study demonstrates the improvement in the fatigue strength of additive manufacturing (AM) metals such as laser-based powder bed fusion of metals by post-processing. Titanium alloy samples manufactured by powder bed fused (PBF) Ti6Al4V produced through laser sintering (LS), treated by submerged laser peening (SLP), cavitation peening (CP), and shot peening accelerated via a water jet (SPwj), were subjected to torsional fatigue testing and compared with the as-built specimen. At SLP, the samples were treated by laser ablation (LA) and laser cavitation (LC) which was developed following LA. A cavitating jet was used for CP. For comparison, conventional post-processing using SPwj was also performed. To characterize the microstructural modification caused by the three post-processing methods, the cross-section of the treated surface was observed by electron backscatter diffraction. The fatigue strengths at 107 cycles were found to be 217, 361, 313, and 285 MPa for the as-built, SLP, CP, and SPwj specimens, respectively. The primary factors contributing to fatigue strength improvement by post-processing were surface smoothing and the introduction of compressive residual stress. The experimental observations were used to derive correlation formulas to estimate the fatigue life improvement due to post-processing as the function of the surface roughness and surface residual stress.
Uzun F., Korsunsky A.M.
The utilization of the focused ion beam digital image correlation (FIB-DIC) technique for measuring in-plane displacements and the employment of the height digital image correlation (hDIC) technique as two-step DIC for determining both in-plane and out-of-plane displacements within the region of interest are detailed in this paper. Consideration is given to the microscopy data’s measurement scale and resolution to confirming the capability of both techniques to conduct micro-scale correlations with nano-scale sensitivity, thereby making it suitable for investigating the residual elastic strains formed due to processing. The sequential correlation procedure of the FIB-DIC technique has been optimized to achieve a balance between accuracy and performance for correlating sequential scanning electron microscope images. Conversely, the hDIC technique prioritizes the accurate correlation of SEM images directly with the reference state without a sequential procedure and offers optimal computational performance through advanced parallel computing tools, particularly suited for correlating profilometry data related to large-scale displacements. In this study, the algorithm of the hDIC technique is applied as two-step DIC to evaluate the elastic strain relaxation on the surface of a ring-core drilled using focused ion beam. Both techniques are utilized to correlate the same scanning electron microscope images collected during the monitoring of the ring drilling process. A comparison of the correlation results of both techniques is undertaken regarding the quantification of the near-surface residual elastic strains, with the analysis conducted to discern the superior accuracy of the hDIC algorithm. Furthermore, the distinctions between the two techniques are delineated and discussed.
Ma L., Su F., Wen Y., Korsunsky A.M., Wiercigroch M.
In this paper, a generic model for interfacial inclusions embedded between dissimilar solids is proposed to address a wide range of problems in materials engineering. By virtue of the equivalent eigenstrain principle and line inclusion concept, the model is formulated in the framework of plane elasticity using the complex variable Green's function method. Explicit analytical solutions for the deformation field of the interfacial inclusions containing an internal eigenstrain distribution or subjected to far-field loading are derived. As a typical example, a lamellar semi-elliptical interfacial inclusion problem is analyzed, from which the robustness of the proposed interfacial inclusion model is validated through a direct FEM simulation. It is found that the internal eigenstrain distribution leads to a significant stress concentration in the vicinity of the endpoints of the major axis. Interfaces between an inclusion and substrates tends to debond due to the concentrated shear traction, while the bi-material interface outside the inclusion can detach as a result of the concentrated normal traction. The formulations established in this study provide a concise and convenient analytical solution for various interfacial inclusion problems encountered in material engineering.
Arhatari B.D., Paganin D.M., Kirkwood H., Tremsin A.S., Gureyev T.E., Korsunsky A.M., Kockelmann W., Hofmann F., Huwald E., Zhang S., Kelleher J., Abbey B.
Korsunsky A., Salimon A., Statnik E., Pisarev V., Eleonsky S.
The determination of residual stresses by combining blind hole drilling and optical interferometric measurement of relief deformation is re-visited to evaluate its applicability to aerospace structures. The experimental methodology involves drilling a deep blind hole and evaluating the hole diameter increments in the principal strain directions using electronic speckle-pattern interferometry (ESPI). This is followed by the determination of the principal residual stress components via the solution of the inverse correlation problem. The study presents the pathway to overcoming one of the primary obstacles in residual stress determination, namely, the optimization of the measurement and interpretation procedures to obtain reliable results. It can be concluded from the analysis of the problem that the formulae connecting the raw experimental data and to the sought residual stress component values lead to a well-posed inverse problem. This makes it possible to obtain estimations of the measurement uncertainty. High density fringe patterns from ESPI provide a rapid and reliable method for residual stress determination, as illustrated using examples of approximately 160 MPa stresses in irregular zones of thick-walled structures.
Stakhanova S.V., Krechetov I.S., Shafigullina K.E., Lepkova T.L., Berestov V.V., Statnik E.S., Zyryanova Z.E., Novikova E.A., Korsunsky A.M.
In this work, hierarchically porous composites were prepared in the form of activated carbon cloth (CC) Busofit T–1–055 filled with an electrically conductive polymer, polyaniline (PANI), for use as pseudocapacitive electrodes of electrochemical supercapacitors (SCs). CC fibers have high nanoporosity and specific surface area, so it was possible to deposit (via the chemical oxidative polymerization of aniline) a significant amount of PANI on them in the form of a thin layer mainly located on the inner surface of the pores. Such morphology of the composite made allowed the combining of the high capacitive characteristics of PANI with the reversibility of electrochemical processes, high columbic efficiency and cyclic stability rather typical for carbon materials of double-layer SCs. The highest capacitance of composite electrodes of about 4.54 F/cm2 with high cyclic stability (no more than 8% of capacity loss after 2000 charge–discharge cycles with a current density of 10 A/cm2) and columbic efficiency (up to 98%) was achieved in 3 M H2SO4 electrolyte solution when PANI was synthesized from an aniline hydrochloride solution with a concentration of 0.25 M. Trasatti analysis revealed that 27% of specific capacitance corresponded to pseudocapacitance, and 73% to the double-layer capacitance.
Uzun F., Lee T.L., Wang Z.I., Korsunsky A.M.
The reconstruction of welding residual stresses has been performed based on the assumption of continuous processing conditions, owing to the limitations of reconstruction methods. This assumption prevents the attainment of a comprehensive understanding of mechanical deformations in the entire weld zone. The voxel-based eigenstrain (inherent strain) reconstruction method emerges as an appropriate approach for the full-field reconstruction of residual stresses in finite length weldments without such assumption. The innovative reconstruction capability of this advanced method is presented in this study, aiming to comprehend all components of residual stresses and eigenstrains in finite length weldments with discontinuous processing properties using only a single component of experimental data belonging to a limited portion of the specimen. Numerical experiments were conducted to develop the tools. These tools were validated using a case study employing experimental data obtained through contact profilometry measurements from the surface of discharge machine cutting (minimally disturbing cutting) in a bead-on-plate weldment of Inconel alloy 740H designed for ultra-supercritical power generation. The reconstructed two components of normal residual stresses that do not align with the available experimental data were validated by independent neutron diffraction strain scanning quantifications. Furthermore, the reconstruction of residual stresses in the intact component prior to cutting was carried out using the eigenstrains associated with the post-cut state of the weldment.
Uzun F., Korsunsky A.M.
AbstractThis paper introduces the OxCM contour method solver, a console application structured based on the legacy version of the FEniCS open-source computing platform for solving partial differential equations (PDEs) using the finite element method (FEM). The solver provides a standardized approach to solving linear elastic numerical models, calculating residual stresses corresponding to measured displacements resulting from changes in the boundary conditions after minimally disturbing (non-contact) cutting. This is achieved through a single-line command, specifically in the case of availability of a domain composed of a tetrahedral mesh and experimentally collected and processed profilometry data. The solver is structured according to a static boundary condition rule, allowing it to rely solely on the cross-section occupied by the experimental data, independent of the geometric irregularities of the investigated body. This approach eliminates the need to create realistic finite element domains for complex-shaped, discontinuous processing bodies. While the contour method provides highly accurate quantification of residual stresses in parts with continuously processed properties, real scenarios often involve parts subjected to discontinuous processing and geometric irregularities. The solver’s validation is performed through numerical experiments representing both continuous and discontinuous processing conditions in artificially created domains with regular and irregular geometric features based on the eigenstrain theory. Numerical experiments, free from experimental errors, contribute to a novel understanding of the contour method's capabilities in reconstructing residual stresses in such bodies through a detailed error analysis. Furthermore, the application of the OxCM contour method solver in a real-case scenario involving a nickel-based superalloy finite-length weldment is demonstrated. The results exhibit the expected distribution of the longitudinal component of residual stresses along the long-transverse direction, consistent with the solution of a commercial solver that was validated by neutron diffraction strain scanning.
Wei S., Wuu D., Soh V., Lau K.B., Wei F., Liogas K.A., Zhang B., Zhu Q., Ng C.K., Korsunsky A.M., Wang P., Ramamurty U.
The role of the nitrogen atmosphere on the microstructure and tensile properties of laser powder bed fused (PBF-LB/M) Fe-xCr (x=0, 5, 10, 15, 24 wt.%, mixed using elemental Fe and pre-alloyed Fe-46 wt.% Cr powders) binary alloys was investigated and compared with those fabricated under an inert (argon) atmosphere. Microstructural characterization reveals the variations of grain morphology with the chemical composition and the distinct effects of nitrogen on grain refinement and texture. Additionally, PBF-LB/M performed under the nitrogen atmosphere leads to the formation of Cr and Fe nitrides in the alloy. Significant enhancements in strength were observed in Fe, Fe-5Cr, and Fe-10Cr fabricated under nitrogen atmosphere due possibly to the solid solution and precipitation strengthening caused by dissolved nitrogen and the nitrides, respectively. However, the Fe-15Cr and Fe-24Cr alloys processed under the nitrogen atmosphere are brittle and crack upon PBF-LB/M due to the residual stresses. The findings in this work enrich the understanding of the effects of fabrication atmospheres in additive manufacturing, insights of which can be extended to diverse categories of alloys.
Lab address
Wellington Square, Oxford OX1 2JD, United Kingdom
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