Ring Core Method

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Alexander M Korsunsky - One of the best experts on this subject based on the ideXlab platform.

  • an analysis of macro and micro scale residual stresses of type i ii and iii using fib dic micro Ring Core milling and crystal plasticity fe modelling
    International Journal of Plasticity, 2017
    Co-Authors: Enrico Salvati, Alexander M Korsunsky
    Abstract:

    Abstract Mechanical failure frequently initiates at the grain level, at which intra-granular stresses are of paramount importance. Under cyclic loading conditions regions within grains that experience high values of tensile residual stress are more prone to damage processes that lead to the formation of slip bands, defects, micro-voids and fissures that induce crack nucleation and propagation. For these reasons, the knowledge and understanding of residual stress across the scales (Types I, II and III) is crucial for improving the accuracy of mechanical failure prediction. The present study was carried out with the purpose of revealing the presence and nature of inter- and intra-granular residual stresses (known as Type II and III) that were present in an Aluminium alloy sample as consequence of plastic deformation. To this end, a well-defined macroscopic residual stress field was introduced in a miniature four-point bent beam. Following sample microstructure mapping by EBSD, the evaluation of Type II & III residual stress at the grain level was conducted using FIB-DIC micro-Ring-Core Method. The combination of two calibrated models at different length scales enabled the simulation of stress across the scales, from the continuum large scale down to the crystal level (CP-FEM). As the outcome of this multi-scale modelling, the RS simulation predictions at all scales (Type I, II & III) were obtained and compared with the experimental results using a statistical approach. A key significance of the finding was that the Standard Deviation of the local residual stress values (95% confidence interval half width) amounted to as much as 2/3 of the macroscopic Type I value. This highlights the importance of including the information about Type II+III stresses in predictive design for structural integrity and the avoidance of failure. Error propagation due to measurement uncertainty was accounted in the analysis. By consideRing Schmid factor at locations of residual stress measurement, a modest correlation was found with Type II & III residual stresses.

  • Microscale Methods of Residual Stress Evaluation
    A Teaching Essay on Residual Stresses and Eigenstrains, 2017
    Co-Authors: Alexander M Korsunsky
    Abstract:

    Owing to the importance of micro- and nanoscale residual stress evaluation Methods in the context of current research and technology, this separate chapter is devoted to this topic. It begins with an overview of microfocus diffraction techniques with X-ray and electron beams, and spectroscopic Methods, e.g., Raman. The rest of the chapter is devoted to the history of the development and illustration of use of the Focused Ion Beam—Digital Image Correlation (FIB-DIC) technique, with particular attention paid to the microscale Ring-Core Method. FIB-DIC spatially resolved residual stress profiling is classified into sequential and parallel approaches, and case studies exemplifying the use of these approaches are described.

  • uncertainty quantification of residual stress evaluation by the fib dic Ring Core Method due to elastic anisotropy effects
    International Journal of Solids and Structures, 2016
    Co-Authors: Enrico Salvati, Tan Sui, Alexander M Korsunsky
    Abstract:

    Abstract Elastic anisotropy can have a significant effect on the reliability and precision of residual stress evaluation, due to the uncertainty in the elastic constants multiplied by the measured strains. For the focused ion beam – digital image correlation (FIB–DIC) Ring-Core Method taken as an example, a Mathematica package was developed to evaluate the complete in-plane residual stress state from the measured strain relief values using known material orientation and anisotropic elastic properties for materials displaying cubic symmetry. However, in many practical situations the underlying material orientation is unknown, and nominal isotropic continuum elastic constants are used. This leads to a systematic error in the stress calculation. The present analysis focuses on the statistical evaluation of the uncertainty in stress evaluation due to the unknown material orientation as a function of its degree of anisotropy. We demonstrate an experimental application of this procedure to a real case of micron scale residual stress analysis in a nickel-base superalloy.

  • the effect of eigenstrain induced by ion beam damage on the apparent strain relief in fib dic residual stress evaluation
    Materials & Design, 2016
    Co-Authors: Enrico Salvati, Tan Sui, Alexander J G Lunt, Alexander M Korsunsky
    Abstract:

    Abstract FIB milling using Ga ions is known to be accompanied by implantation, multiplication of material defects, material property modification (e.g. amorphisation), inelastic shrinking/swelling and residual stress generation. These processes affect the reliability of the micro-Ring-Core Method for residual stress evaluation. Safe use of this technique requires formulating approaches that provide quantitative criteria of the Method's validity. In the present study this task is accomplished by proposing a numerical model based on eigenstrain. Parametric simulations were performed to identify the extent to which the FIB-DIC micro-Ring-Core measurements are affected. As an example of a real and relevant material system, the procedure was applied to silicon material. The curvature of an AFM cantilever due to FIB damage was monitored, and the eigenstrain magnitude determined by matching the model to observations. Using the resulting eigenstrain profile, parametric analysis was performed in terms of the pillar radius, and the elastic strain field calculated at the pillar surface that is monitored in the FIB-DIC micro-Ring-Core Method. An important property of the model is its versatility that allows it to be adapted to different milling conditions and geometries to determine the ultimate spatial resolution limits of the FIB-DIC Method.

  • Uncertainty quantification of residual stress evaluation by the FIB–DIC Ring-Core Method due to elastic anisotropy effects
    International Journal of Solids and Structures, 2016
    Co-Authors: Enrico Salvati, Tan Sui, Alexander M Korsunsky
    Abstract:

    Abstract Elastic anisotropy can have a significant effect on the reliability and precision of residual stress evaluation, due to the uncertainty in the elastic constants multiplied by the measured strains. For the focused ion beam – digital image correlation (FIB–DIC) Ring-Core Method taken as an example, a Mathematica package was developed to evaluate the complete in-plane residual stress state from the measured strain relief values using known material orientation and anisotropic elastic properties for materials displaying cubic symmetry. However, in many practical situations the underlying material orientation is unknown, and nominal isotropic continuum elastic constants are used. This leads to a systematic error in the stress calculation. The present analysis focuses on the statistical evaluation of the uncertainty in stress evaluation due to the unknown material orientation as a function of its degree of anisotropy. We demonstrate an experimental application of this procedure to a real case of micron scale residual stress analysis in a nickel-base superalloy.

František Menda - One of the best experts on this subject based on the ideXlab platform.

Edoardo Bemporad - One of the best experts on this subject based on the ideXlab platform.

  • Design, fabrication and characterization of multilayer Cr-CrN thin coatings with tailored residual stress profiles
    Materials & Design, 2016
    Co-Authors: Marco Renzelli, Muhammad Zeeshan Mughal, Marco Sebastiani, Edoardo Bemporad
    Abstract:

    Abstract Compressive residual stress in hard coatings can improve adhesion and in-service toughness, since they can inhibit crack nucleation and propagation. However, the role of through thickness residual stress profile is not fully understood. This is because of (a) lack of knowledge of stress evolution mechanisms and (b) limitations of experimental techniques used for stress profiling. The present work deals with design, deposition and characterization of Cr-CrN multilayer coatings, produced by Magnetron SputteRing Physical Vapour Deposition (MS-PVD), with the purpose to understand the effect of through thickness residual stress profile on coating adhesion. An automated optimisation algorithm was used to determine the desired residual stress through-thickness profile for a range of contact loading situations. On the basis of modelling activities, three different Cr-CrN multilayers were produced, with the aim of obtaining different stress gradients, as measured by incremental micro-scale focused ion beam (FIB) Ring-Core Method, while keeping the same average stress value and same average hardness in the film. Results show a significant correlation between the observed residual stress profiles and scratch adhesion, where different optimal stress profiles are identified for different loading conditions. This is a major step with respect to previous literature, where scratch adhesion in hard coatings was only correlated to the average stress in the film, but not to the stress gradient within the film thickness. Here, we show that a lower interfacial compressive stress and a reduced through thickness stress gradient gives improved scratch adhesion, when using 10 μm and 200 μm sphero-conical indenters.

  • Residual micro-stress distributions in heat-pressed ceramic on zirconia and porcelain-fused to metal systems: Analysis by FIB-DIC Ring-Core Method and correlation with fracture toughness
    Dental materials : official publication of the Academy of Dental Materials, 2015
    Co-Authors: Marco Sebastiani, Federico Massimi, G. Merlati, Edoardo Bemporad
    Abstract:

    Abstract Objectives The production of fixed partial dentures (FPDs) induces complex residual stress profiles, due to both the thermal expansion coefficient mismatch between the veneeRing ceramic and the framework and to the thermal gradients occurRing duRing the final cooling. Detailed knowledge of residual stress distributions in the veneeRing ceramics is important to understand the interface phenomena with the framework and the consequences of the different fiRing systems. The first objective of this study was to analyse the residual stress distribution in heat-pressed ceramic on zirconia Core with micrometer spatial resolution, with also a focus on the stress at the interface versus porcelain-fused-to-metal samples. The second purpose was to correlate the residual stress with the fracture toughness. Methods The micron-scale focused ion beam (FIB) Ring-Core Method was used to map the residual stress over the cross-sections of the veneeRing ceramics. The Methodology is based on FIB micro-milling of annular trenches, combined with high-resolution in situ scanning electron microscope (SEM) imaging, a full field strain analysis by digital image correlation (DIC) and numerical models for residual stress calculation. Fracture toughness was evaluated by using high load Vickers indentation and hardness/modulus were measured by nanoindentation testing also across the interfaces. Results Both prosthetic systems showed a compressive stress at the ceramic surface on a micron-scale. The stress profile for porcelain fused to metal (PFM) showed a transition to tensile stress at the half of the layer, whilst the stress in proximity of the interface was more compressive in both the cases. Residual stress on a micron scale are higher in magnitude than the corresponding macro-scale values reported in the literature, due to the stress relaxation given, at larger scales, by micro-voids and cracks. The stress field was directly correlated with the indentation fracture toughness, which was higher in those areas where the compressive stress is greater. Stress analysis in correspondence of interfacial porosity for the zirconia sample also showed that micro-defects could induce local modifications of the residual stress field, which may even locally generate a tensile stress state. Significance The interfacial stress in dental systems was analysed on a micron scale and can give further insights into the process/property/performance correlation for this class of materials. In particular, interfacial and/or local modifications of the residual stress are expected to have a significant influence on crack nucleation mechanism in correspondence of micro-defects. A direct correlation between residual stress distribution and fracture toughness was proposed. It is noteworthy that the Method can be used to study real crowns and bridges. In fact, complex geometries can be easily analysed by this procedure.

  • discussion on interfacial residual stress analysis of thermal spray coatings by miniature Ring Core cutting combined with dic Method by j g zhu et al experimental mechanics doi 10 1007 s11340 012 9640 2
    Experimental Mechanics, 2014
    Co-Authors: Marco Sebastiani, Edoardo Bemporad, Alexander M Korsunsky, C Eberl, G M Pharr
    Abstract:

    The purpose of this discussion is to point out some similarities between a paper that was recently published by J.G. Zhu et al. [1] and a paper that we published earlier on the same subject [2]. The micro-scale FIB-DIC Ring Core technique was first proposed in 2009 [3]. The attraction of this Method lies in its compatibility with well-established experimental facilities and interpretation procedures, and its applicability to stiff and compliant, crystalline and amorphous materials alike. The technique utilizes a combination of material removal and imaging capabilities of focused ion beam and dual-beam microscopes. This allows highly spatially resolved residual stress measurements to be performed with sub-micron lateral spatial resolution [4] and depth profiling with a resolution of ~100 nm [2]. In the recent paper by J.G. Zhu et al. [1], the micro-Ring Core Method (μRCM) was applied to thermal spray coatings. It is gratifying to see that the Method is being adopted by others around the world. This demonstrates the Method’s flexibility and capability, and paves a way for its further evolution and development. However, as the technique becomes more widely used, we feel that it is important for the origins of the ideas and techniques to remain transparent and clearly identified. In the paper by J.G. Zhu et al., several aspects of the procedure correspond in detail to the Methodology described in our previous publication [2]. Specifically:

  • Discussion on “Interfacial Residual Stress Analysis of Thermal Spray Coatings by Miniature Ring-Core Cutting Combined with DIC Method” by J.G. Zhu et al., Experimental Mechanics DOI:10.1007/s11340-012-9640-2
    Experimental Mechanics, 2014
    Co-Authors: Marco Sebastiani, Edoardo Bemporad, Alexander M Korsunsky, C Eberl, G M Pharr
    Abstract:

    The purpose of this discussion is to point out some similarities between a paper that was recently published by J.G. Zhu et al. [1] and a paper that we published earlier on the same subject [2]. The micro-scale FIB-DIC Ring Core technique was first proposed in 2009 [3]. The attraction of this Method lies in its compatibility with well-established experimental facilities and interpretation procedures, and its applicability to stiff and compliant, crystalline and amorphous materials alike. The technique utilizes a combination of material removal and imaging capabilities of focused ion beam and dual-beam microscopes. This allows highly spatially resolved residual stress measurements to be performed with sub-micron lateral spatial resolution [4] and depth profiling with a resolution of ~100 nm [2]. In the recent paper by J.G. Zhu et al. [1], the micro-Ring Core Method (μRCM) was applied to thermal spray coatings. It is gratifying to see that the Method is being adopted by others around the world. This demonstrates the Method’s flexibility and capability, and paves a way for its further evolution and development. However, as the technique becomes more widely used, we feel that it is important for the origins of the ideas and techniques to remain transparent and clearly identified. In the paper by J.G. Zhu et al., several aspects of the procedure correspond in detail to the Methodology described in our previous publication [2]. Specifically:

  • Residual stress measurement in thin films at sub-micron scale using Focused Ion Beam milling and imaging
    Thin Solid Films, 2012
    Co-Authors: Xu Song, Edoardo Bemporad, Marco Sebastiani, Kong Boon Yeap, Jing Zhu, Jonathan P Belnoue, Kaiyang Zeng, Alexander M Korsunsky
    Abstract:

    Abstract Residual stress evaluation in thin films at the sub-micron scale was achieved in the present study using a semi-destructive trench-cutting (Ring-Core) Method. Focused Ion Beam was employed to introduce the strain relief by milling the slots around an “island” and also to record the images for strain change evaluation by digital image correlation analysis of micrographs. Finite element simulation was employed to predict the curves for strain relief as a function of milling depth, and compared with the experimental measurements, showing good agreement. An empirical mathematical description of the curves was proposed that allows efficient data analysis for residual stress evaluation.

Patrik Šarga - One of the best experts on this subject based on the ideXlab platform.

Marco Sebastiani - One of the best experts on this subject based on the ideXlab platform.

  • Design, fabrication and characterization of multilayer Cr-CrN thin coatings with tailored residual stress profiles
    Materials & Design, 2016
    Co-Authors: Marco Renzelli, Muhammad Zeeshan Mughal, Marco Sebastiani, Edoardo Bemporad
    Abstract:

    Abstract Compressive residual stress in hard coatings can improve adhesion and in-service toughness, since they can inhibit crack nucleation and propagation. However, the role of through thickness residual stress profile is not fully understood. This is because of (a) lack of knowledge of stress evolution mechanisms and (b) limitations of experimental techniques used for stress profiling. The present work deals with design, deposition and characterization of Cr-CrN multilayer coatings, produced by Magnetron SputteRing Physical Vapour Deposition (MS-PVD), with the purpose to understand the effect of through thickness residual stress profile on coating adhesion. An automated optimisation algorithm was used to determine the desired residual stress through-thickness profile for a range of contact loading situations. On the basis of modelling activities, three different Cr-CrN multilayers were produced, with the aim of obtaining different stress gradients, as measured by incremental micro-scale focused ion beam (FIB) Ring-Core Method, while keeping the same average stress value and same average hardness in the film. Results show a significant correlation between the observed residual stress profiles and scratch adhesion, where different optimal stress profiles are identified for different loading conditions. This is a major step with respect to previous literature, where scratch adhesion in hard coatings was only correlated to the average stress in the film, but not to the stress gradient within the film thickness. Here, we show that a lower interfacial compressive stress and a reduced through thickness stress gradient gives improved scratch adhesion, when using 10 μm and 200 μm sphero-conical indenters.

  • Residual micro-stress distributions in heat-pressed ceramic on zirconia and porcelain-fused to metal systems: Analysis by FIB-DIC Ring-Core Method and correlation with fracture toughness
    Dental materials : official publication of the Academy of Dental Materials, 2015
    Co-Authors: Marco Sebastiani, Federico Massimi, G. Merlati, Edoardo Bemporad
    Abstract:

    Abstract Objectives The production of fixed partial dentures (FPDs) induces complex residual stress profiles, due to both the thermal expansion coefficient mismatch between the veneeRing ceramic and the framework and to the thermal gradients occurRing duRing the final cooling. Detailed knowledge of residual stress distributions in the veneeRing ceramics is important to understand the interface phenomena with the framework and the consequences of the different fiRing systems. The first objective of this study was to analyse the residual stress distribution in heat-pressed ceramic on zirconia Core with micrometer spatial resolution, with also a focus on the stress at the interface versus porcelain-fused-to-metal samples. The second purpose was to correlate the residual stress with the fracture toughness. Methods The micron-scale focused ion beam (FIB) Ring-Core Method was used to map the residual stress over the cross-sections of the veneeRing ceramics. The Methodology is based on FIB micro-milling of annular trenches, combined with high-resolution in situ scanning electron microscope (SEM) imaging, a full field strain analysis by digital image correlation (DIC) and numerical models for residual stress calculation. Fracture toughness was evaluated by using high load Vickers indentation and hardness/modulus were measured by nanoindentation testing also across the interfaces. Results Both prosthetic systems showed a compressive stress at the ceramic surface on a micron-scale. The stress profile for porcelain fused to metal (PFM) showed a transition to tensile stress at the half of the layer, whilst the stress in proximity of the interface was more compressive in both the cases. Residual stress on a micron scale are higher in magnitude than the corresponding macro-scale values reported in the literature, due to the stress relaxation given, at larger scales, by micro-voids and cracks. The stress field was directly correlated with the indentation fracture toughness, which was higher in those areas where the compressive stress is greater. Stress analysis in correspondence of interfacial porosity for the zirconia sample also showed that micro-defects could induce local modifications of the residual stress field, which may even locally generate a tensile stress state. Significance The interfacial stress in dental systems was analysed on a micron scale and can give further insights into the process/property/performance correlation for this class of materials. In particular, interfacial and/or local modifications of the residual stress are expected to have a significant influence on crack nucleation mechanism in correspondence of micro-defects. A direct correlation between residual stress distribution and fracture toughness was proposed. It is noteworthy that the Method can be used to study real crowns and bridges. In fact, complex geometries can be easily analysed by this procedure.

  • discussion on interfacial residual stress analysis of thermal spray coatings by miniature Ring Core cutting combined with dic Method by j g zhu et al experimental mechanics doi 10 1007 s11340 012 9640 2
    Experimental Mechanics, 2014
    Co-Authors: Marco Sebastiani, Edoardo Bemporad, Alexander M Korsunsky, C Eberl, G M Pharr
    Abstract:

    The purpose of this discussion is to point out some similarities between a paper that was recently published by J.G. Zhu et al. [1] and a paper that we published earlier on the same subject [2]. The micro-scale FIB-DIC Ring Core technique was first proposed in 2009 [3]. The attraction of this Method lies in its compatibility with well-established experimental facilities and interpretation procedures, and its applicability to stiff and compliant, crystalline and amorphous materials alike. The technique utilizes a combination of material removal and imaging capabilities of focused ion beam and dual-beam microscopes. This allows highly spatially resolved residual stress measurements to be performed with sub-micron lateral spatial resolution [4] and depth profiling with a resolution of ~100 nm [2]. In the recent paper by J.G. Zhu et al. [1], the micro-Ring Core Method (μRCM) was applied to thermal spray coatings. It is gratifying to see that the Method is being adopted by others around the world. This demonstrates the Method’s flexibility and capability, and paves a way for its further evolution and development. However, as the technique becomes more widely used, we feel that it is important for the origins of the ideas and techniques to remain transparent and clearly identified. In the paper by J.G. Zhu et al., several aspects of the procedure correspond in detail to the Methodology described in our previous publication [2]. Specifically:

  • Discussion on “Interfacial Residual Stress Analysis of Thermal Spray Coatings by Miniature Ring-Core Cutting Combined with DIC Method” by J.G. Zhu et al., Experimental Mechanics DOI:10.1007/s11340-012-9640-2
    Experimental Mechanics, 2014
    Co-Authors: Marco Sebastiani, Edoardo Bemporad, Alexander M Korsunsky, C Eberl, G M Pharr
    Abstract:

    The purpose of this discussion is to point out some similarities between a paper that was recently published by J.G. Zhu et al. [1] and a paper that we published earlier on the same subject [2]. The micro-scale FIB-DIC Ring Core technique was first proposed in 2009 [3]. The attraction of this Method lies in its compatibility with well-established experimental facilities and interpretation procedures, and its applicability to stiff and compliant, crystalline and amorphous materials alike. The technique utilizes a combination of material removal and imaging capabilities of focused ion beam and dual-beam microscopes. This allows highly spatially resolved residual stress measurements to be performed with sub-micron lateral spatial resolution [4] and depth profiling with a resolution of ~100 nm [2]. In the recent paper by J.G. Zhu et al. [1], the micro-Ring Core Method (μRCM) was applied to thermal spray coatings. It is gratifying to see that the Method is being adopted by others around the world. This demonstrates the Method’s flexibility and capability, and paves a way for its further evolution and development. However, as the technique becomes more widely used, we feel that it is important for the origins of the ideas and techniques to remain transparent and clearly identified. In the paper by J.G. Zhu et al., several aspects of the procedure correspond in detail to the Methodology described in our previous publication [2]. Specifically:

  • Residual stress measurement in thin films at sub-micron scale using Focused Ion Beam milling and imaging
    Thin Solid Films, 2012
    Co-Authors: Xu Song, Edoardo Bemporad, Marco Sebastiani, Kong Boon Yeap, Jing Zhu, Jonathan P Belnoue, Kaiyang Zeng, Alexander M Korsunsky
    Abstract:

    Abstract Residual stress evaluation in thin films at the sub-micron scale was achieved in the present study using a semi-destructive trench-cutting (Ring-Core) Method. Focused Ion Beam was employed to introduce the strain relief by milling the slots around an “island” and also to record the images for strain change evaluation by digital image correlation analysis of micrographs. Finite element simulation was employed to predict the curves for strain relief as a function of milling depth, and compared with the experimental measurements, showing good agreement. An empirical mathematical description of the curves was proposed that allows efficient data analysis for residual stress evaluation.

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