How to simulate Indentation Size Effect (ISE) using Finite Element Method (FEM)?

Your work on Indentation Size Effect (ISE) using Finite Element Method (FEM) in ABAQUS sounds intriguing and challenging. The phenomenon of ISE that you are observing (or rather, not observing) could potentially be attributed to several factors.

To simulate the ISE using FEM in ABAQUS, you should consider the following:

Material Hardening: In many indentation studies, it has been seen that classical elastoplastic constitutive laws, such as the von Mises yield criterion, fail to reproduce the ISE due to strain gradient hardening not being accounted for. The ISE typically becomes observable in materials with strain gradient plasticity. It might be beneficial to incorporate strain gradient plasticity into your model.

Model Scale: The length scale of the model might be affecting your simulation results. If the scale is not in the nanometer range, you may not see ISE.

Mesh Sensitivity: It seems you've already refined your mesh near the indenter tip, which is a good step. However, it's still worth rechecking your mesh sensitivity. If the mesh isn't fine enough, it might not be able to capture the material behaviour accurately.

Contact Interaction: Check the contact definitions again. Problems in the definition of contacts, such as contact stiffness and overclosure, can lead to abnormal results.

Indentation Load: Be aware of the possibility that the load you are applying might be too high. Plastic deformation might be the dominant deformation mode if the load is too large, and you may not observe ISE.

Influence of Material Model Parameters: Check whether the material model parameters are accurate. Wrong input parameters can greatly affect the simulation results.

Remember that the simulation of ISE using FEM is a complex task due to the involvement of various scale-dependent phenomena. It might take several iterations of refining and validating your model to get it right finally. Good luck with your research!

The Indentation Size Effect (ISE) is a phenomenon observed in materials science where the hardness of a material appears to increase as the size of the indentation (or, equivalently, the load of the indenter) decreases. In other words, smaller indentations result in higher hardness values. This trend contradicts the classical definition of hardness, which is expected to be a constant material property, independent of the indenter size or load.

The ISE is often explained by the strain gradient plasticity theory, which accounts for the influence of the geometrically necessary dislocations on the deformation behaviour of the material. This theory suggests that the plastic deformation beneath the indenter is not uniform but instead exhibits a gradient, with higher strain (and thus, higher dislocation density and hardness) near the surface, and lower strain deeper in the material.

Consequently, when you conduct indentation tests at varying depths or loads, you should observe that the hardness decreases as the indentation depth or the load increases. This decrease should follow a specific trend, often modelled by Meyer's law or the proportional specimen resistance (PSR) model.

However, remember that the ISE might not be observable in all materials or under all conditions. Factors such as the type of material, the nature of the indenter, the scale of the test, and the specific methodology can all influence whether and to what extent the ISE is observed.

Dzevad Hadzihafizovic

I can still offer some suggestions to help you address the issue you're facing with the Indentation Size Effect (ISE) in your ABAQUS simulations.

Here are a few potential reasons why you might not be observing the expected trend of decreasing hardness with increasing indentation depth:

Material model: Verify that the material model you have assigned to the specimen accurately represents the behavior of the material under consideration. Ensure that the material properties, such as elastic modulus and yield stress, are appropriate for the specific material you are simulating. Consider consulting literature or experimental data to validate the material model.

Mesh refinement: Although you mentioned that you have refined the mesh near the indenter tip, it's important to ensure that the mesh is adequately refined throughout the entire contact region and beneath the indenter. The mesh should be able to capture the stress concentration accurately and provide sufficient resolution for accurate results. Try increasing the mesh density in the region of interest and re-run the simulations.

Convergence criteria: Check the convergence criteria you have set for your simulations. Ensure that the convergence criteria are stringent enough to achieve accurate results. Tightening the convergence criteria may improve the accuracy of the simulation results.

Indenter geometry and mesh: Confirm that the geometry and mesh of the indenter are accurately represented in your simulation. Ensure that the indenter semi-angle of 70.3° is correctly defined in the model. Additionally, double-check the mesh quality around the indenter tip and make sure it is appropriate for capturing the stress concentration accurately.

Contact behavior: Review the contact interaction settings between the indenter and specimen. Confirm that the settings accurately represent the desired behavior, such as frictionless tangential contact and hard normal contact. Any inaccuracies in the contact behavior could affect the simulation results.

Loading conditions: Verify the loading conditions you have applied to the simulation. Ensure that the loading rate and magnitude are appropriate for the indentation test you are trying to simulate. Consider comparing your loading conditions with experimental data or established standards to ensure consistency.

Post-processing and analysis: Double-check your post-processing procedure, especially the implementation of the Oliver-Pharr Method for determining hardness. Confirm that you are correctly extracting the indentation depth and load values from the simulation results and accurately applying the method to calculate hardness.

It is worth noting that the Indentation Size Effect (ISE) can be influenced by various factors, including material properties, strain gradient effects, and surface roughness. It is possible that other mechanisms or phenomena are counteracting the expected trend in your specific simulation. Additional considerations may be necessary to capture these effects accurately.

How can I measure MMP-1 protein activity or protein level from liver tissue?

Binary Logistic Generalized Linear Mixed model in SPSS. Is it doable?

Looking for Materials with high thermal expansion coefficient and high temperature resistance?

Guidelines for survey (question type) analysis?

What are the values needed for gabor filter's parameter for cifar10 data?

Can we block unwanted images during the x-ray prediction?

No title

What techniques can I use to determine the miscibility of polymer blends?

Sample dilution for quantitative analysis using ELISA?

The procedure compute?

MD MOE RMSD

MD MOE RMSD

fatal error

fatal error

fatal error

fatal error

How to compare two groups with only two measurements?

Enhanced Yellow Fluorescent Protein (Aequorea victoria) DNA sequence?

What kind of fluid could I use for a pitfall trap that also does not invalidate molecular testing?

What's the best way to measure growth rates in House sparrow chicks from day 2 to day 10?