Simulation of Nanoindentation Test Data

2011 ◽  
pp. 105-117
Author(s):  
Anthony C. Fischer-Cripps
Keyword(s):  
Test Data ◽  
Nanoindentation Test

Mechanical Properties of Ion-Irradiated Stainless Steel Determined by Nanoindentation Tests and Finite Element Analyses

2020 ◽  
Author(s):  
Jae Min Sim ◽  
Yoon-Suk Chang ◽  
Byeong Seo Kong ◽  
Changheui Jang
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Test Data ◽  
Radiation Effects ◽  
Ion Irradiation ◽  
Nanoindentation Test ◽  
Finite Element Analyses ◽  
Stress Strain ◽  
Term Operation ◽  
Constitutive Parameters

Abstract While austenitic stainless steels (ASSs) have been widely adopted for reactor vessel internals because of their excellent material properties, diverse ageing-related degradation may occur due to high temperature, corrosive and neutron radiation environments during operation. In particular, since the change of mechanical properties is a major concern in long-term operation but it is difficult to prepare and handle standard specimens influenced by neutrons, most of experimental researches for enhanced understanding of the radiation effects have been focused on high-energetic ion-irradiation and tests of small specimens. In this study, systematic finite element analyses were carried out to quantify changing mechanical properties based on both virgin and ion-irradiated nanoindentation test data of typical ASS material. First of all, numerical analysis was carried out to obtain unirradiated material constitutive parameters by using trial set along the miniature specimen and comparing test data, and then indentation stress-strain (ISS) curve was derived. Subsequently, ISS was converted into uniaxial stress-strain response taking into account simple correlation. Finally, with regard to the irradiated material, similar analytical procedures were established. 304 SS was irradiated with 2 MeV proton and radioactivity is being measured. Comparison between analysis result and experimental one will be carried out, of which details and key findings will be discussed.

Elastic recovery and reloading of hardness impressions with a conical indenter

2002 ◽  
Vol 750 ◽  
Author(s):  
A. C. Fischer-Cripps
Keyword(s):  
Residual Stress ◽  
Test Data ◽  
Elastic Recovery ◽  
Indentation Test ◽  
Nanoindentation Test ◽  
Instrumented Indentation ◽  
Specimen Material ◽  
Elastic Event ◽  
Instrumented Indentation Test ◽  
Elastic Unloading

ABSTRACTThe present work is concerned with the analysis of elastic unloading data in conventional methods of analysis of nanoindentation test data. Experimental and finite element results are used to show that the reloading of a residual impression with and without the presence of residual stress is an elastic event, and further shows that the estimation of modulus and hardness computed using established techniques is in error due to the assumption the sides of the residual impression are straight. This work calls into question the validity of commonly used methods of test and analysis of instrumented indentation test data that use the elastic unloading data as the basis for the calculation of modulus and hardness of the specimen material.

Use of combined elastic modulus in the analysis of depth-sensing indentation data

2001 ◽  
Vol 16 (11) ◽  
pp. 3050-3052 ◽  
Author(s):  
A. C. Fischer-Cripps
Keyword(s):  
Elastic Modulus ◽  
Test Data ◽  
Nanoindentation Test ◽  
Depth Sensing ◽  
True Value ◽  
Methods Of Analysis ◽  
Reduced Modulus ◽  
Unloading Stiffness ◽  
Depth Response

It is shown that the substitution of reduced modulus for specimen modulus in the analysis equations for nanoindentation test data is valid. The methods of analysis use the slope of the unloading force–depth response which is assumed to be elastic. Because of this utilization of the slope or unloading stiffness, it makes no difference whether or not the deflection of the indenter is accommodated explicitly or transferred to that occurring within the specimen by artificially reducing the specimen modulus from its true value to lower value, the reduced modulus.

Modeling Nanoscale Rheological and Mechanical Properties of Thin Film Asphalt Binder

2016 ◽  
Author(s):  
Hasan M. Faisal ◽  
Zafrul Hakim Khan ◽  
Rafiqul Tarefder
Keyword(s):  
Thin Film ◽  
Mechanical Properties ◽  
Elastic Modulus ◽  
Test Data ◽  
Asphalt Concrete ◽  
Asphalt Binder ◽  
Nanoindentation Test ◽  
Film Material ◽  
Macro Scale ◽  
Sdr Model

Traditionally, mechanical properties of asphalt concrete (AC) is evaluated through macro-scale testing. However, when aggregates are mixed with asphalt binder, it creates a thin film of 20μm to 40μm around the aggregate particles and the primary strength of AC is derived from the interaction between the binder and aggregates. Therefore, to understand the behavior of asphalt concrete it is necessary to study the binder properties in a nanoscale. Nanoindentation test has been adopted to examine the thin film material property. In a nanoindentation test, a loaded nanoindenter is used to indent the sample surface and measure the indenter displacement as a function of load. To this day, most researchers have used the Oliver-Pharr method to analyze the indentation test data and obtain Elastic modulus (E) and hardness (H) of the material. Generally, in a nanoindentation test, there is a loading and unloading phase. In an elasto-plastic material, loading phase has elastic and plastic response and unloading phase has only elastic response. In Oliver-Pharr method, elastic modulus is obtained through the slope of the unloading curve. Therefore, Oliver-Pharr method mostly applicable for the elasto-plastic metals because it does not incorporate any viscous effect. However, in case of visco-elastic material like asphalt, during the unloading phase, the slope of the unloading curve becomes negative due to the viscous flow. Therefore, using Oliver-Pharr (OP) method in this circumstances will yield an inaccurate value of modulus of elasticity. In the current study, the test data was modeled and analyzed using a well-established spring-dashpot-rigid (SDR) model for viscoelastic material to determine the elastic, plastic and viscous properties. The model assumes the indenter displacement is a function of a quadratic spring, a quadratic dashpot and a plastic rigid body. The loading phase of the nanoindentation test has three contributing parameters: elasticity (E), indentation viscosity (η) and hardness (H). During creep, only contributing parameter is indentation viscosity (η) and while unloading the contributing factors are found to be E and η. Nonlinear least square curve fitting technique was employed to model the nanoindentation test data to the SDR model to find out the contributing parameters E, η and H. In addition, the extended dwell time on the asphalt binder samples produced positive load displacement curves, which were further analyzed with Oliver-Pharr method. Comparison between two models results show traditional Oliver-Pharr model predicts the material properties 5 to 10 times lower than SDR model, as Oliver-Pharr does not consider the viscous behavior in the material.

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