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Instrumented Indentation Test: An Aiding Tool for Materials Science and Industry

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Materials Simulation and Design".

Deadline for manuscript submissions: closed (20 December 2022) | Viewed by 31836

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Prof. Dr. Giovanni Maizza

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Guest Editor

Department of Applied Science and Technology, Politecnico di Torino, 10129 Torino, Italy
Interests: instrumented indentation testing; contact mechanics; micro–macro modeling of the multiphysical processing of materials; microstructure design of materials; microstructure–property–process parameter relationships
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Prof. Dr. Dongil Kwon

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Co-Guest Editor

Seoul National University
Interests: instrumented indentation testing; residual stress measurement; reliability assessment

Special Issue Information

Dear Colleagues,

It is believed that the instrumented indentation test (IIT) will revolutionize the industry in the next two decades, while continuing to lead to new elucidations about the nature and behavior of materials. It shares the same mechanical fundamentals as a conventional indentation test (IT), but it also permits a multitude of indentation properties, other than hardness, to be extracted in a quick, easy, and nondestructive manner. As such, it can be used either in offline or online manufacturing processes to assess the final mechanical performances of a part or to optimize the most relevant process parameters. IIT is particularly suitable for additive manufactured products, welded joints, and microelectromechanical devices, which generally lack a standard structural assessment. Although IIT can virtually be performed over nano-, micro- and macrodimensional scales, over the last decade, research into IIT has been dominated by nano-IIT studies, which have had a great impact on the progress of materials science and the thin film and coating industry. However, even greater impacts may be expected in the industrial sectors if macro-IIT comes into play, provided that appropriate guidelines are available. Macro-indentation properties correlate more naturally with the familiar tensile-like properties than nano-IIT ones do; thus, the macro-instrumented indentation test will offer an unprecedent viable nondestructive means of measuring tensile-like elastoplastic properties at a local scale in a wide range of metals and engineering alloys. The primary goal of this Special Issue is to present the recent advances in IIT research, with particular attention to macro-IIT achievements. The secondary goal is to provide comprehensive fundamental knowledge on IIT methodologies along with useful guidelines that are not covered by any available national or international standard, to permit IIT techniques to be exploited in new research and engineering fields.

Prof. Giovanni Maizza
Prof. Dongil Kwon
Guest Editors

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Keywords

Instrumented indentation
Indentation theory and modeling
Residual stress measurement
Field-assisted indentation
Materials: conventional bulk as well as nanocrystalline and porous metals and alloys
similar and dissimilar welded joints
Materials behavior: elastoplatic, superplastic, superelastic, recrystallization, creep, anisotropic
New in situ and ex situ inspection methodologies aiding materials characterization during indentation

Published Papers (12 papers)

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21 pages, 4123 KiB

Open AccessArticle

Nanoscale and Tensile-Like Properties by an Instrumented Indentation Test on PBF-LB SS 316L Steel

by Giovanni Maizza, Faisal Hafeez, Alessandra Varone and Roberto Montanari

Materials 2024, 17(1), 255; https://doi.org/10.3390/ma17010255 - 03 Jan 2024

Viewed by 874

Abstract

The mechanical properties of a defect-free laser melting (PBF-LB) deposit of an AISI 316L steel alloy were assessed by means of an instrumented indentation test (IIT), at both the macro- and nano-scales. The inherent non-equilibrium microstructure of the alloy was chemically homogenous and consisted of equiaxed grains and large-elongated grains (under the optical microscope) with irregular outlines composed of a much finer internal cell structure (under the scanning electron microscope). Berkovich and Vickers indenters were used to assess the indentation properties across individual grains (nano) and over multiple grains (macro), respectively. The nano-indentation over the X-Y plane revealed nearly constant indentation modulus across an individual grain but variable on average within different grains whose value depended on the relative orientation of the individual grain. The macro-indentation test was conducted to analyze the tensile-like properties of the polycrystalline SS 316L alloy over the X-Y and Y-Z planes. The macro-indentation test provided a reliable estimate of the ultimate tensile strength (UTS-like) of the alloy. Other indentation properties gave inconsistent results, and a post factum analysis was, therefore, conducted, by means of a new approach, to account for the presence of residual stresses. The already existing indentation data were supplemented with new repeated indentation tests to conduct a detailed analysis of the relaxation ability of compressive and tensile residual stresses. The developed methodology allows the effect of residual stresses and the reliability of measured macro-indentation properties to be examined as a function of a small group of indentation parameters. Full article

(This article belongs to the Special Issue Instrumented Indentation Test: An Aiding Tool for Materials Science and Industry)

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10 pages, 2133 KiB

Open AccessArticle

Effect of Equibiaxial Pre-Stress on Mechanical Properties Evaluated Using Depth-Sensing Indentation with a Point-Sharp Indenter

by Takashi Akatsu, Yoshihide Tabata, Yutaka Shinoda and Fumihiro Wakai

Materials 2023, 16(2), 528; https://doi.org/10.3390/ma16020528 - 05 Jan 2023

Cited by 1 | Viewed by 765

Abstract

This study examined the effect of an imposed equibiaxial pre-stress (EBPS) on the evaluation of mechanical properties, using the depth-sensing indentation method with a point-sharp indenter, through a numerical analysis of indentations simulated with the 3D finite element method. The predicted elastic modulus, E^*, and yield stress, Y^*, were used as elastic and plastic deformation resistances under the indentation, respectively. It was found that both increased nominally with the increase in compressive EBPS and decreased with the increase in tensile EBPS, even though the induced change in the piling-up or sinking-in around the indentations was not significant. The effect of EBPS on E^* was described by the Hooke’s law for an isotropic elastoplastic material, whereas that on Y^* was accounted for by the change in the von Mises stress due to EBPS. Full article

(This article belongs to the Special Issue Instrumented Indentation Test: An Aiding Tool for Materials Science and Industry)

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22 pages, 5130 KiB

Open AccessEditor’s ChoiceArticle

Accurate Estimation of Yield Strength and Ultimate Tensile Strength through Instrumented Indentation Testing and Chemical Composition Testing

by Martin Scales, Joel Anderson, Jeffrey A. Kornuta, Nathan Switzner, Ramon Gonzalez and Peter Veloo

Materials 2022, 15(3), 832; https://doi.org/10.3390/ma15030832 - 22 Jan 2022

Cited by 12 | Viewed by 3470

Abstract

Federal rule changes governing natural gas pipelines have made non-destructive techniques, such as instrumented indentation testing (IIT), an attractive alternative to destructive tests for verifying properties of steel pipeline segments that lack traceable records. Ongoing work from Pacific Gas and Electric Company’s (PG&E) materials verification program indicates that IIT measurements may be enhanced by incorporating chemical composition data. This paper presents data from PG&E’s large-scale IIT program that demonstrates the predictive capabilities of IIT and chemical composition data, with particular emphasis given to differences between ultimate tensile strength (UTS) and yield strength (YS). For this study, over 80 segments of line pipe were evaluated through tensile testing, IIT, and compositional testing by optical emission spectroscopy (OES) and laboratory combustion. IIT measurements of UTS were, generally, in better agreement with destructive tensile data than YS and exhibited about half as much variability as YS measurements on the same sample. The root-mean squared error for IIT measurements of UTS and YS, respectively, were 27 MPa (3.9 ksi) and 43 MPa (6.2 ksi). Next, a machine learning model was trained to estimate YS and UTS by combining IIT with chemical composition data. The agreement between the model’s estimated UTS and tensile UTS values was only slightly better than the IIT-only measurements, with an RMSE of 21 MPa (3.1 ksi). However, the YS estimates showed much greater improvement with an improved RMSE of 27 MPa (3.9 ksi). The experimental, mechanical, and metallurgical factors that contributed to IIT’s ability to consistently determine destructive UTS, and the differences in its interaction with composition as compared to YS, are discussed herein. Full article

(This article belongs to the Special Issue Instrumented Indentation Test: An Aiding Tool for Materials Science and Industry)

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11 pages, 3676 KiB

Open AccessArticle

Pop-In Identification in Nanoindentation Curves with Deep Learning Algorithms

by Stephania Kossman and Maxence Bigerelle

Materials 2021, 14(22), 7027; https://doi.org/10.3390/ma14227027 - 19 Nov 2021

Cited by 9 | Viewed by 2082

Abstract

High–speed nanoindentation rapidly generates large datasets, opening the door for advanced data analysis methods such as the resources available in artificial intelligence. The present study addresses the problem of differentiating load–displacement curves presenting pop-in, slope changes, or instabilities from curves exhibiting a typical loading path in large nanoindentation datasets. Classification of the curves was achieved with a deep learning model, specifically, a convolutional neural network (CNN) model implemented in Python using TensorFlow and Keras libraries. Load–displacement curves (with pop-in and without pop-in) from various materials were input to train and validate the model. The curves were converted into square matrices (50 × 50) and then used as inputs for the CNN model. The model successfully differentiated between pop-in and non-pop-in curves with approximately 93% accuracy in the training and validation datasets, indicating that the risk of overfitting the model was negligible. These results confirmed that artificial intelligence and computer vision models represent a powerful tool for analyzing nanoindentation data. Full article

(This article belongs to the Special Issue Instrumented Indentation Test: An Aiding Tool for Materials Science and Industry)

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13 pages, 3249 KiB

Open AccessArticle

Instrumented Nanoindentation Tests Applied to Bulk Metallic Materials: From Calibration Issue to Pile-Up Phenomena

by Marcello Cabibbo

Materials 2021, 14(21), 6360; https://doi.org/10.3390/ma14216360 - 24 Oct 2021

Cited by 3 | Viewed by 1644

Abstract

Instrumented nanoindentation tests have reached an effective level of theoretical and practical knowledge to become an interesting and useful tool for determining hardness, H, and local elasticity (reduced Young’s modulus), E_r, of a variety of materials, from coatings and thin films to bulk metallic materials. Nanoindentation instruments are equipped with analysis software for raw data for hardness and reduced Young’s modulus evaluation, generally based on the Oliver and Pharr analysis method. On the other hand, it is widely known and recognized that prior data acquisition, a tip-dependent calibration procedure of compliance, and area function are needed. With this in view, an accurate and sound calibration protocol is here reported. Hardness and local elastic modulus is measured on different bulk metallic materials, showing the distinctive strengths of using nanoindentation. Finally, a local elastic-plastic phenomenon mostly induced by the nanoindentation tip on ductile metallic material (i.e., pile-up) is also reported and modelled. This manuscript is thus intended to favor and account for the importance of using the instrumented nanoindentation tests for H and E_r measurements of metallic materials. Full article

(This article belongs to the Special Issue Instrumented Indentation Test: An Aiding Tool for Materials Science and Industry)

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17 pages, 3330 KiB

Open AccessArticle

Indentation Modulus, Indentation Work and Creep of Metals and Alloys at the Macro-Scale Level: Experimental Insights into the Use of a Primary Vickers Hardness Standard Machine

by Alessandro Schiavi, Claudio Origlia, Alessandro Germak, Andrea Prato and Gianfranco Genta

Materials 2021, 14(11), 2912; https://doi.org/10.3390/ma14112912 - 28 May 2021

Cited by 10 | Viewed by 2859

Abstract

In this work, the experimental method and the calculation model for the determination of indentation moduli, indentation work, and indentation creep of metallic materials, by means of macroscale-level forces provided by a primary hardness standard machine at the National Institute of Metrological Research (INRIM) at the at room temperature were described. Indentation moduli were accurately determined from measurements of indentation load, displacement, contact stiffness and hardness indentation imaging and from the slope of the indentation unloading curve by applying the Doerner-Nix linear model; indentation work, representing the mechanical work spent during the force application of the indentation procedure, was determined by calculating the areas under the loading–unloading indentation curve, through fitting experimental data with a polynomial law. Measurements were performed with a pyramidal indenter (Vickers test). The applied force was provided by a deadweight machine, and the related displacement was measured by a laser interferometric system. Applied forces and the occurring indentation depths were simultaneously measured: the resulting loading–unloading indentation curve was achieved. Illustrative tests were performed on metals and alloy samples. Discussion and comments on the suitability of the proposed method and analysis were reported. Full article

(This article belongs to the Special Issue Instrumented Indentation Test: An Aiding Tool for Materials Science and Industry)

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13 pages, 7176 KiB

Open AccessArticle

Application of Macro-Instrumented Indentation Test for Superficial Residual Stress and Mechanical Properties Measurement for HY Steel Welded T-Joints

by Junsang Lee, Kyungyul Lee, Seungha Lee, Oh Min Kwon, Won-Ki Kang, Jong-Il Lim, Hee-Keun Lee, Seong-Min Kim and Dongil Kwon

Materials 2021, 14(8), 2061; https://doi.org/10.3390/ma14082061 - 19 Apr 2021

Cited by 15 | Viewed by 3003

Abstract

HY-80 and HY-100 steels, widely used in constructing large ocean vessels and submarine hulls, contain mixed microstructures of tempered bainite and martensite and provide high tensile strength and toughness. Weld integrity in HY steels has been studied to verify and optimize welding conditions. In this study, the T-joint weld coupons, HY80 and HY100, were fabricated from HY-80 and HY-100 steel plates with a thickness of 30 mm as base metals by submerged-arc welding. Flux-cored arc welding was performed on an additional welding coupon consisting of HY-100 to evaluate the effect of repair welds (HY100RP). Microstructures in the heat-affected zones (HAZ) were thoroughly analyzed by optical observation. Instrumented indentation testing, taking advantage of local characterization, was applied to assess the yield strength and the residual stress of the HAZ and base regions. The maximum hardness over 400 HV was found in the HAZ due to the high volume fraction of untempered martensite microstructure. The yield strength of the weld coupons was evaluated by indentation testing, and the results showed good agreement with the uniaxial tensile test (within 10% range). The three coupons showed similar indentation residual stress profiles on the top and bottom surfaces. The stress distribution of the HY100 coupon was comparable to the results from X-ray diffraction. HY100RP demonstrated increased tensile residual stress compared to the as-welded coupon due to the effect of the repair weld (323 and 103 MPa on the top and bottom surfaces). This study verifies the wide applicability of indentation testing in evaluating yield strength and residual stress. Full article

(This article belongs to the Special Issue Instrumented Indentation Test: An Aiding Tool for Materials Science and Industry)

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19 pages, 5716 KiB

Open AccessFeature PaperArticle

Flat-Top Cylinder Indenter for Mechanical Characterization: A Report of Industrial Applications

by Roberto Montanari and Alessandra Varone

Materials 2021, 14(7), 1742; https://doi.org/10.3390/ma14071742 - 01 Apr 2021

Cited by 4 | Viewed by 1982

Abstract

FIMEC (flat-top cylinder indenter for mechanical characterisation) is an instrumented indentation test employing a cylindrical punch. It has been used to determine the mechanical properties of metallic materials in several applications of industrial interest. This work briefly describes the technique and the theory of indentation with a flat-ended punch. The flat indentation of metals has been investigated through experimental tests, and an equation has been derived to calculate the yield stress from the experimental data in deep indentation. The approach is supported by many data on various metals and alloys. Some selected case studies are presented in the paper: (i) crank manufacturing through pin squeeze casting; (ii) the evaluation of the local mechanical properties in a carter of complex geometry; (iii) the qualification of Al billets for extrusion; (iv) stress–relaxation tests on CuCrZr heat sinks; (v) the characterization of thick W coatings on CuCrZr alloy; (vi) the measure of the local mechanical properties of the molten-zone (MZ) and the heat-affected zone (HAZ) in welded joints. The case studies demonstrate the great versatility of the FIMEC test which provides information not available by employing conventional experimental techniques such as tensile, bending, and hardness tests. On the basis of theoretical knowledge and large amount of experimental data, FIMEC has become a mature technique for application on a large scale in industrial practice. Full article

(This article belongs to the Special Issue Instrumented Indentation Test: An Aiding Tool for Materials Science and Industry)

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23 pages, 11611 KiB

Open AccessArticle

Correlation Between the Indentation Properties and Microstructure of Dissimilar Capacitor Discharge Welded WC-Co/High-Speed Steel Joints

by Giovanni Maizza, Renato Pero, Frediano De Marco and Takahito Ohmura

Materials 2020, 13(11), 2657; https://doi.org/10.3390/ma13112657 - 11 Jun 2020

Cited by 19 | Viewed by 2980

Abstract

The welding of cemented carbide to tool steel is a challenging task, of scientific and industrial relevance, as it combines the high level of hardness of cemented carbide with the high level of fracture toughness of steel, while reducing the shaping cost and extending the application versatility, as its tribological, toughness, thermal and chemical properties can be optimally harmonised. The already existing joining technologies often impart either insufficient toughness or poor high-temperature strength to a joint to withstand the ever-increasing severe service condition demands. In this paper, a novel capacitor discharge welding (CDW) process is investigated for the case of a butt-joint between a tungsten carbide-cobalt (WC-Co) composite rod and an AISI M35 high-speed steel (HSS) rod. The latter was shaped with a conical-ended projection to promote a high current concentration and heat at the welding zone. CDW functions by combining a direct current (DC) electric current pulse and external uniaxial pressure after a preloading step, in which only uniaxial pressure is applied. The relatively high heating and cooling rates promote a thin layer of a characteristic ultrafine microstructure that combines high strength and toughness. Morphological analysis showed that the CDW process: (a) forms a sound and net shaped joint, (b) preserves the sub-micrometric grain structure of the original WC-Co composite base materials, via a transitional layer, (c) refines the microstructure of the original martensite of the HSS base material, and (d) results in an improved corrosion resistance across a 1-mm thick layer near the weld interface on the steel side. A nano-indentation test survey determined: (e) no hardness deterioration on the HSS side of the weld zone, although (f) a slight decrease in hardness was observed across the transitional layer on the composite side. Furthermore, (g) an indication of toughness of the joint was perceived as the size of the crack induced by processing the residual stress after sample preparation was unaltered. Full article

(This article belongs to the Special Issue Instrumented Indentation Test: An Aiding Tool for Materials Science and Industry)

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12 pages, 3467 KiB

Open AccessArticle

Nano-Indentation Properties of Tungsten Carbide-Cobalt Composites as a Function of Tungsten Carbide Crystal Orientation

by Renato Pero, Giovanni Maizza, Roberto Montanari and Takahito Ohmura

Materials 2020, 13(9), 2137; https://doi.org/10.3390/ma13092137 - 05 May 2020

Cited by 13 | Viewed by 4146

Abstract

Tungsten carbide-cobalt (WC-Co) composites are a class of advanced materials that have unique properties, such as wear resistance, hardness, strength, fracture-toughness and both high temperature and chemical stability. It is well known that the local indentation properties (i.e., nano- and micro-hardness) of the single crystal WC particles dispersed in such composite materials are highly anisotropic. In this paper, the nanoindentation response of the WC grains of a compact, full-density, sintered WC-10Co composite material has been investigated as a function of the crystal orientation. Our nanoindentation survey has shown that the nanohardness was distributed according to a bimodal function. This function was post-processed using the unique features of the finite mixture modelling theory. The combination of electron backscattered diffraction (EBSD) and statistical analysis has made it possible to identify the orientation of the WC crystal and the distinct association of the inherent nanoindentation properties, even for a small set (67) of nanoindentations. The proposed approach has proved to be faster than the already existing ones and just as reliable, and it has confirmed the previous findings concerning the relationship between crystal orientation and indentation properties, but with a significant reduction of the experimental data. Full article

(This article belongs to the Special Issue Instrumented Indentation Test: An Aiding Tool for Materials Science and Industry)

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10 pages, 2431 KiB

Open AccessArticle

Relationship of Stiffness-Based Indentation Properties Using Continuous-Stiffness-Measurement Method

by Wai Yeong Huen, Hyuk Lee, Vanissorn Vimonsatit and Priyan Mendis

Materials 2020, 13(1), 97; https://doi.org/10.3390/ma13010097 - 24 Dec 2019

Cited by 7 | Viewed by 2880

Abstract

The determination of elastic modulus (E) and hardness (H) relies on the accuracy of the contact area under the indenter tip, but this parameter cannot be explicitly measured during the nanoindentation process. This work presents a new approach that can derive the elastic modulus (E) and contact depth (h_c) based on measured experiment stiffness using the continuous-stiffness-measurement (CSM) method. To achieve this, an inverse algorithm is proposed by incorporating a set of stiffness-based relationship functions that are derived from combining the dimensional analysis approach and computational simulation. This proposed solution considers both the sink-in and pile-up contact profiles; therefore, it provides a more accurate solution when compared to a conventional method that only considers the sink-in contact profile. While the proposed solution is sensitive to Poisson’s ratio (ν) and the equivalent indentation conical angle (θ), it is not affected by material plasticity, including yield strength (σ_y) and work hardening (n) for the investigated range of 0.001 < σ_y/E < 0.5. The proposed stiffness-based approach can be used to consistently derive elastic modulus and hardness by using stiffness and the load-and-unload curve measured by the continuous-stiffness-measurement (CSM) method. Full article

(This article belongs to the Special Issue Instrumented Indentation Test: An Aiding Tool for Materials Science and Industry)

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Review

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30 pages, 6497 KiB

Open AccessReview

Pop-In Phenomenon as a Fundamental Plasticity Probed by Nanoindentation Technique

by Takahito Ohmura and Masato Wakeda

Materials 2021, 14(8), 1879; https://doi.org/10.3390/ma14081879 - 09 Apr 2021

Cited by 24 | Viewed by 3310

Abstract

The attractive strain burst phenomenon, so-called “pop-in”, during indentation-induced deformation at a very small scale is discussed as a fundamental deformation behavior in various materials. The nanoindentation technique can probe a mechanical response to a very low applied load, and the behavior can be mechanically and physically analyzed. The pop-in phenomenon can be understood as incipient plasticity under an indentation load, and dislocation nucleation at a small volume is a major mechanism for the event. Experimental and computational studies of the pop-in phenomenon are reviewed in terms of pioneering discovery, experimental clarification, physical modeling in the thermally activated process, crystal plasticity, effects of pre-existing lattice defects including dislocations, in-solution alloying elements, and grain boundaries, as well as atomistic modeling in computational simulation. The related non-dislocation behaviors are also discussed in a shear transformation zone in bulk metallic glass materials and phase transformation in semiconductors and metals. A future perspective from both engineering and scientific views is finally provided for further interpretation of the mechanical behaviors of materials. Full article

(This article belongs to the Special Issue Instrumented Indentation Test: An Aiding Tool for Materials Science and Industry)

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