Influences of stress on the measurement of mechanical properties using nanoindentation: Part II. Finite element simulations

1996 ◽  
Vol 11 (3) ◽  
pp. 760-768 ◽  
Author(s):  
A. Bolshakov ◽  
W. C. Oliver ◽  
G. M. Pharr
Keyword(s):  
Finite Element ◽  
Elastic Modulus ◽  
Contact Area ◽  
Cylindrical Specimen ◽  
Preceding Paper ◽  
Indentation Load ◽  
The Finite Element Method ◽  
Indentation Process ◽  
Plastic Indentation ◽  
Area Determination

The finite element method has been used to study the behavior of aluminum alloy 8009 during elastic-plastic indentation to establish how the indentation process is influenced by applied or residual stress. The study was motivated by the experiments of the preceding paper which show that nanoindentation data analysis procedures underestimate indentation contact areas and therefore overestimate hardness and elastic modulus in stressed specimens. The NIKE2D finite element code was used to simulate indentation contact by a rigid, conical indenter in a cylindrical specimen to which biaxial stresses were applied as boundary conditions. Indentation load-displacement curves were generated and analyzed according to standard methods for determining hardness and elastic modulus. The simulations show that the properties measured in this way are inaccurate because pileup is not accounted for in the contact area determination. When the proper contact area is used, the hardness and elastic modulus are not significantly affected by the applied stress.

Analysis of sharp-tip-indentation load–depth curve for contact area determination taking into account pile-up and sink-in effects

2004 ◽  
Vol 19 (11) ◽  
pp. 3307-3315 ◽  
Author(s):  
Yeol Choi ◽  
Ho-Seung Lee ◽  
Dongil Kwon
Keyword(s):  
Finite Element ◽  
Elastic Modulus ◽  
Contact Area ◽  
Indentation Depth ◽  
Indentation Load ◽  
Real Contact Area ◽  
Elastic Deflection ◽  
Contact Depth ◽  
Real Contact ◽  
Pile Up

Hardness and elastic modulus of micromaterials can be evaluated by analyzing instrumented sharp-tip-indentation load–depth curves. The present study quantified the effects of tip-blunting and pile-up or sink-in on the contact area by analyzing indentation curves. Finite-element simulation and theoretical modeling were used to describe the detailed contact morphologies. The ratio f of contact depth, i.e., the depth including elastic deflection and pile-up and sink-in, to maximum indentation depth, i.e., the depth measured only by depth sensing, ignoring elastic deflection and pile-up and sink-in, was proposed as a key indentation parameter in evaluating real contact depth during indentation. This ratio can be determined strictly in terms of indentation-curve parameters, such as loading and unloading slopes at maximum depth and the ratio of elastic indentation energy to total indentation energy. In addition, the value of f was found to be independent of indentation depth, and furthermore the real contact area can be determined and hardness and elastic modulus can be evaluated from f. This curve-analysis method was verified in finite-element simulations and nanoindentation experiments.

scholarly journals Integrating the Finite Element Method with a Data-Driven Approach for Dam Displacement Prediction

2020 ◽  
Vol 2020 ◽  
pp. 1-16 ◽  
Author(s):  
Chenfei Shao ◽  
Chongshi Gu ◽  
Zhenzhu Meng ◽  
Yating Hu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Elastic Modulus ◽  
Random Coefficient ◽  
Arch Dam ◽  
Data Driven ◽  
The Finite Element Method ◽  
Random Coefficient Model ◽  
Proposed Model ◽  
Element Method

Both numerical simulations and data-driven methods have been applied in dam’s displacement modeling. For monitored displacement data-driven methods, the physical mechanism and structural correlations were rarely discussed. In order to take the spatial and temporal correlations among all monitoring points into account, we took the first step toward integrating the finite element method into a data-driven model. As the data-driven method, we selected the random coefficient model, which can make each explanatory variable coefficient of all monitoring points following one or several normal distributions. In this way, explanatory variables are constrained. Another contribution of the proposed model is that the actual elastic modulus at each monitoring point can be back-calculated. Moreover, with a Lagrange polynomial interpolation, we can obtain the distribution field of elastic modulus, rather than gaining one value for the whole dam in previous studies. The proposed model was validated by a case study of the concrete arch dam in Jinping-I hydropower station. It has a better prediction precision than the random coefficient model without the finite element method.

Numeric Loading Simulation of Titanium Implant Manufactured Using 3D Printing

2018 ◽  
Vol 284 ◽  
pp. 380-385 ◽  
Author(s):  
Anton I. Golodnov ◽  
Yu.N. Loginov ◽  
Stepan I. Stepanov
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Titanium Alloy ◽  
Elastic Modulus ◽  
Titanium Implant ◽  
Finite Element Method Simulation ◽  
Medical Implants ◽  
The Finite Element Method ◽  
Simulation Data

The problem of medical implants honeycomb structures loading has been stated. The problem was solved using simulation by the finite element method. Simulation revealed that it is possible to change the elastic modulus of the material more than three times with respect to the bulk titanium alloy. The quality of the simulation was estimated based on the convergence of the simulation data.

Effects of Free Damping Layers on Harmonic Response of Rotating Blades

1989 ◽  
Author(s):  
T. H. Young ◽  
T. N. Shiau ◽  
S. H. Chiu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Elastic Modulus ◽  
Loss Factor ◽  
Harmonic Excitation ◽  
The Finite Element Method ◽  
Harmonic Response ◽  
Rotating Blades ◽  
Rotating Blade ◽  
Triangular Elements

This paper studies the forced vibration of a rotating blade with free damping layers to harmonic excitation by means of the finite element method. The damping layers are made of viscoelastic material with complex elastic modulus, and the excitation may be either distributed or concentrated. Triangular elements with totally 15 d.o.f. are used to allow for a great variety of shapes and boundary conditions. The effects of various parameters, such as loss factor, storage modulus and thickness of damping layers, are investigated. The results show that the vibration amplitudes near resonances can be significantly reduced by the free damping layers.

Modelling of ballraceway contacts in a slewing bearing with non-linear springs

2011 ◽  
Vol 225 (4) ◽  
pp. 827-831 ◽  
Author(s):  
X H Gao ◽  
X D Huang ◽  
H Wang ◽  
J Chen
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Contact Area ◽  
The Finite Element Method ◽  
Simple Method ◽  
Slewing Bearing ◽  
Combined Loads ◽  
Non Linear ◽  
The Difference ◽  
Supporting Structures

During the operation, a slewing bearing is always subjected to a set of combined loads. It is the source of deformation of ballraceway contacts, rings, and even supporting structures. In practice, deformation of rings and supporting structures is often neglected for simplification, that is, they are supposed to be ideally stiff. To take elasticity of rings and supporting (fixed) structures into consideration, the finite-element method (FEM) is applied. Due to hundreds of contact pairs and the difference in the scale of contact area and rings or supporting structures, it is difficult to simultaneously model both local ballraceway contacts and the global slewing rings in a slewing bearing. The article developed a simple method to solve the problem, where the contacts are replaced by non-linear springs.

Overview of methods to identify the static normal wheel-rail contact

2021 ◽  
pp. 095440972110424
Author(s):  
Ina Stratmann ◽  
Jannik Goersch ◽  
Christian Schindler
Keyword(s):  
Finite Element ◽  
Contact Area ◽  
High Pressures ◽  
Contact Point ◽  
Element Model ◽  
Carbon Paper ◽  
The Finite Element Method ◽  
Element Analysis ◽  
Detailed Assessment ◽  
Shape And Size

Determining the shape and size of a wheel-rail contact area is required to calculate fatigue and wear of wheel and rail. Fatigue and wear are influenced by high pressures of up to 1000 MPa that act on the small contact area of approximately 1 cm². One problem in identifying the contact patch is the inaccessibility of the contact point. Therefore, numerical and experimental methods have been applied to identify the shape and size of the contact area in the static wheel-rail contact. Here, we summarize and compare methods to identify the static wheel-rail contact area, in particular the Hertzian calculation, the use of carbon paper, the use of pressure measurement film, the finite element method, the use of ultrasonic testing, and a semi-Hertzian method called STRIPES. Our review revealed that several methods exist to determine the static wheel-rail contact, which were introduced as well as results of some research projects. However, the partly incomplete description of methods studied impeded a detailed assessment of the results. Furthermore, due to the non-comparable parameters applied in the different studies, it was impossible to contrast the results and methods presented in the different publications. Hence, it is recommended that future results in the field of static wheel-rail contact should be directly contrasted with a detailed finite element model. This proceeding will allow to directly compare different methods on the bases of finite element analysis and thus the identification of a method for each situation.

scholarly journals Determining the elastic modulus and hardness of an ultra-thin film on a substrate using nanoindentation

2009 ◽  
Vol 24 (3) ◽  
pp. 1114-1126 ◽  
Author(s):  
Han Li ◽  
Joost J. Vlassak
Keyword(s):  
Thin Film ◽  
Elastic Modulus ◽  
Contact Stiffness ◽  
Indentation Load ◽  
Analysis Procedure ◽  
Bulk Materials ◽  
Data Analysis Procedure ◽  
Plastic Indentation ◽  
Improved Accuracy ◽  
Layered Half Space

A data analysis procedure has been developed to estimate the contact area in an elasto-plastic indentation of a thin film bonded to a substrate. The procedure can be used to derive the elastic modulus and hardness of the film from the indentation load, displacement, and contact stiffness data at indentation depths that are a significant fraction of the film thickness. The analysis is based on Yu's elastic solution for the contact of a rigid conical punch on a layered half-space and uses an approach similar to the Oliver-Pharr method for bulk materials. The methodology is demonstrated for both compliant films on stiff substrates and the reverse combination and shows improved accuracy over previous methods.

The Correction Factor in Elastic Modulus Determining by Indentation

2014 ◽  
Vol 887-888 ◽  
pp. 997-1000 ◽  
Author(s):  
P.M. Ogar ◽  
V.A. Tarasov ◽  
D.B. Gorokhov
Keyword(s):  
Finite Element ◽  
Elastic Modulus ◽  
Correction Factor ◽  
Indentation Load ◽  
Hardening Material ◽  
Finite Element Study ◽  
Plastic Hardening ◽  
Elastic Modules ◽  
Displacement Diagram ◽  
Element Study

The expression for the correction factor β, improving the accuracy of elastic modules measurement by sphere indentation is determined. It is shown that to determine β it is necessary determine the exponent in the equation of the loading curve, in additional to the previously determined parameters of the indentation load-displacement diagram. The computed exponent value of the unloading curve is given. It is shown that to analyze β can be used the results of finite element study of the sphere indentation in elastic-plastic hardening material.

Effect of Matching Performance on J-Integral of Inhomogeneous Welded Joints

2012 ◽  
Vol 503-504 ◽  
pp. 568-571
Author(s):  
Bo He ◽  
Hong Cai Zhang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Elastic Modulus ◽  
Yield Strength ◽  
Engineering Design ◽  
Welded Joints ◽  
Welded Joint ◽  
J Integral ◽  
The Finite Element Method ◽  
Matching Performance

In this paper, J-integral of 3-zone inhomogeneous welded joint is calculated by use of the finite element method, and the impacts of yield strength matching factor and elastic modulus matching factor on J-integral are studied as well. The analysis results show that the yield strength matching factor affects J-integral value greatly, that is, low matching of inhomogeneous welded joint of same steel can help to improve the ductility of the welded joint and the influence of yield strength matching factor on J-integral is much greater than that of elastic modulus matching factor, so it plays a very important role in the engineering design.

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