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 (original) (raw)
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ACTA IMEKO, 2019
In this paper, the experimental procedure and calculation model for the measurement of the indentation modulus by using the primary hardness standard machine at INRiM in the macro-scale range at room temperature is described. The indentation modulus is calculated based on the Doerner-Nix linear model and from accurate measurements of indentation load, displacement, contact stiffness, and hardness indentation imaging. Measurements are performed with both pyramidal (Vickers test) and spherical indenters (Brinell test). Test force is provided by a dead-weight machine, and the occurring displacement is measured by a laser-interferometric system. The geometrical dimensions of both the Vickers and Brinell indentations are measured by means of a micro-mechanical system and optical microscopy imaging techniques. Applied force and indentation depth are measured simultaneously, at a 16 Hz sampling rate, and the resultant loading-unloading indentation curve is obtained. Preliminary tests are performed on metal and alloy samples. Considerations and comments on the accuracy of the proposed method and analysis are discussed.
MEASUREMENT OF MACRO-SCALE INDENTATION MODULUS USING THE PRIMARY HARDNESS STANDARD MACHINES AT INRIM
In this paper it is described the experimental procedure and the statistical method for the measurement of indentation modulus by using the primary hardness standard machine at INRIM, in the macro-scale range. Indentation modulus is calculated on the basis of Doerner-Nix linear model and from accurate measurements of indentation load, displacement, contact stiffness and Vickers hardness impression imaging. Load is provided by dead-weight masses and displacement is measured by a laserinterferometric system, perpendicular with respect to the Vickers pyramid vertex. The geometrical dimension of the Diamond Pyramid Hardness (DPH) impression is measured by means of a micro-mechanical system and optical microscopy imaging technique. Applied force and indentation depth are measured simultaneously, 16 Hz of sampling rate, and the resulting indentation curve is obtained. Preliminary tests are performed on metals and alloys samples. Considerations and comments on the accuracy of the proposed method and analysis are discussed.
The method we introduced in 1992 for measuring hardness and elastic modulus by instrumented indentation techniques has widely been adopted and used in the characterization of small-scale mechanical behavior. Since its original development, the method has undergone numerous refinements and changes brought about by improvements to testing equipment and techniques as well as from advances in our understanding of the mechanics of elastic-plastic contact. Here, we review our current understanding of the mechanics governing elastic-plastic indentation as they pertain to load and depth-sensing indentation testing of monolithic materials and provide an update of how we now implement the method to make the most accurate mechanical property measurements. The limitations of the method are also discussed.
Determination of the hardness and elastic modulus from continuous vickers indentation testing
Journal of Materials Science, 1996
Continuous Vickers (Hv) indentation tests were performed on different materials (ion crystals, metals, ceramics, silica glass and plastic). Load-indentation depth curves were taken during the loading as weil as during the unloading period by a computer controlled hydraulic mechanical testing machine (MTS 810). The indentation work measured both the loading and the unloading periods, and these were used for the evaluation of parameters characterizing the materials. It was found empirically that there were linear connections between the maximum load to the power 312 and the indentation work. These connections were used to relate the conventional hardness number, Hv, and Young's modulus, E, with the work performed during loading and unloading. This work can be determined with great accuracy from the measurements.
Instrumented indentation test for hardness and materials parameter from millinewtons to kilonewtons
2002
The ISO/DIS 14577 Metallic materials - Instrumented indentation test for hardness and materials parameters Part 1-3 (IIT) concerns test forces up to 30 kN. The paper reports on IIT at test forces ranging from 0.002 N to 1000 N on non magnetizable steel X8 CrMnN 18- 18 (1.386) with well polished surface using Vickers indenter and four hardness machines of different design (Nano Indenter XP, Fischerscope H 100, Zwick Z005 with Universal hardness head and a laboratory four-column set up materials testing machine) according to the standard. Using mostly identical test parameters the results of the different machines are almost in good agreement. Estimated small differences are caused by the different uncertainties of the used machines and by different methods of mathematical analysis of the detected raw data.
Effect of Loading Rate and Duration Time on Indentation Hardness Measurements
Previews studies on the effect of loading rate on the micro and nano indentation hardness showed that both of them affect hardness measurements. Such effect has been included in micro and nano hardness measurements. ISO/FDIS 14577-1 standard determine the loading rate of the indenter for micro hardness showed not exceed 2 μm/sec and for nano hardness should be less then 10 nm/sec. The present study is a trial to reveal the effect of both loading rate and duration time on the macro indentation hardness applied on standard hardness test blocks. A modern Zwick hardness tester that could vary loading rates and duration time over a broad range was used to preform this study. The study showed that a safe loading rate should not exceed 10 μm/sec. It also showed an obvious effect of duration time on the hardness value. It is recommended that the duration value should be stated clearly in such hardness measurement.
Mechanics of Materials, 2016
Instrumented indentation is performed on various metals and alloys. Frame compliance of the instrument is taking into account for accurate measurements. A new relationship between the elastic recovery energy to the total work-of-indentation ratio and the applied load to the square of the contact stiffness ratio is proposed. A proportionality factor has been found by both finite elements method and inverse analysis for the material presenting an intermediate mechanical behavior. The values of elastic modulus obtained from the new relationship are in a very good agreement with the theoretical values given in literature.
Computational Materials Science, 2014
The work-of-indentation approach employed to extract the hardness of a material from the loaddisplacement data is often misinterpreted and improperly compared with the Oliver and Pharr method. A theoretical basis is presented to show that the hardness values evaluated using these two methods are fundamentally different, but are interrelated. As such, an expression that relates one type of hardness to another is derived by considering an energy-based relationship between the contact and the maximum penetration depths for an ideally sharp Berkovich indenter. This modified work-of-indentation approach is first validated using the load-displacement data obtained from the finite element simulation of the indentation contact performed with a Berkovich equivalent conical indenter on materials having a wide range of elastic recovery. The real load-displacement data -with and without dwelling -from ceramics oxides and metals corresponding to a peak indentation load lying in the range 20-120 mN are also considered to validate the proposed method. It has been found that a correction due to the amount of work done during dwelling is required if the load-displacement data also feature a dwelling phase. The hardness value so obtained is found to be in close agreement with its Oliver and Pharr analogue for each material considered thereby indicating that the modified approach, in the present form, is applicable even for blunt indenter when the tip radius is very small as compared to the maximum penetration depth. Further refinement of this methodology is, however, required to take the effect of material's pile-up, sink-in, and tip bluntness on the measured hardness into account.
Measurement of Macro-Scale Indentation Modulus
2017
In this paper it is described the experimental procedure and the statistical method for the measurement of indentation modulus by using the primary hardness standard machine at INRIM, in the macro-scale range. Indentation modulus is calculated on the basis of Doerner-Nix linear model and on the basis of a new non-linear model, and from accurate measurements of indentation load, displacement, contact stiffness and Vickers hardness impression imaging. Load is provided by dead-weight masses and displacement is measured by a laser-interferometric system, perpendicular with respect to the Vickers pyramid vertex. The geometrical dimension of the impression is measured by means of a micro-mechanical system united with optical microscopy imaging technique.
Journal of Mechanical Engineering and Sciences, 2021
Instrumented indentation technique gives the possibility to determine the mechanical properties for small specimens and material in service. Several researchers have attempted to evaluate this approach experimentally and investigated the factors that affect it by using different indenter’s geometries for different engineering materials. In this work, the instrumented indentation technique was used to evaluate the mechanical properties experimentally and numerically using finite element simulation to understand the contact mechanics between the indenter surface and the substrate for two types of steel alloys namely ASTM516-G70 and AISI1010 steel. Two shapes of indenters, blunt (spherical) and sharp (Vickers) were used. The results were then compared with the experimental results extracted from the instrumented indentation test. The results have demonstrated a good agreement between the experimental and the finite element simulation results with error bound a ±5 % for young’s modulus ...