How do you perform indentation testing on materials?

The first step in indentation testing is to choose an appropriate indenter shape and size for the material and the property of interest. The most common indenters are spherical, conical, pyramidal, and cylindrical, each with different advantages and limitations. For example, spherical indenters are suitable for measuring elastic modulus and plastic deformation, while conical and pyramidal indenters are more sensitive to hardness and fracture toughness. Loading mode comes as the second step.

Performing indentation testing on materials involves selecting an appropriate method (e.g., Vickers, Rockwell), preparing the material surface by ensuring cleanliness and, if needed, polishing. Calibrate the testing machine using a known force on a reference material. Choose the indenter and load, apply the load gradually, and measure indentation dimensions like diameter. Calculate hardness using the method-specific formula. Repeat tests in various locations for accuracy. Record and analyze results, comparing them with relevant standards. Consider factors like temperature and humidity. Always follow specific method guidelines and consult experts for accurate and meaningful results.

The most commonly used indenter for nanoindentation is Berkovich Indenter due to its sharp three-sided pyramid shape. It is suitable for measuring a wide range of materials, including metals, ceramics, polymers, and thin films. The Berkovich indenter is preferred for its ability to produce well-defined, reproducible indentations. The conical indenter has a smooth, rounded tip and is suitable for measuring elastic modulus and hardness of soft materials, such as polymers and biological tissues. It is less commonly used in nanoindentation but can be advantageous for certain applications. I have used both of these indenters in most of my studies

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We apply a controlled force (with an AFM or dedicated nanoindenter) to an indenter for a set period and then measuring the size of the indentation left on the material. Common indenters include spherical (ball), conical (Berkovich, Vickers), and pyramidal (Knoop) shapes ( it depends on the penetration depth) Hardness values are calculated based on the size of the indentation and the applied force. Vickers Hardness : the applied load and the surface area of the indentation. Knoop Hardness (HK): Vickers but using different geometric Nanoindentation: continuous measurement of hardness and elastic modulus as a function of penetration depth. Be careful the sample needs usaually to be polished ; sensitive to the T(°C) and the RH.

The type of loading mode is considered after carefully listing out the purpose of the testing: Static mode is generally sufficient for basic hardness and mechanical properties; it's easier to control, is fast, and measures force accurately while neglecting minute errors due to dynamic changes such as vibrations. However, it's not suitable for real-world applications and might take many tests to replicate these. In dynamic testing, the load is applied rapidly, like oscillations, and it measures the rate-dependent behavior of materials like strain-rate sensitivity and viscoelasticity for real-world applications while taking vibrations into account. However, the setup is often complex, time-consuming, and unsuitable for brittle samples.

Evtl. müssen je nach Fragestellung die Kapitelüberschriften überdacht werden. Da hier wom?glich nach Eindringverfahren (Penetrant Testing, PT) gefragt wurde, g?ben die einzelnen Kapitel generell keine Antwort auf die Frage.

Did you know? when loading with an indenter over graphite and your load force is high enough (and your loading speed is fast enough) the pressure at the tip of the indenter is enough to phase change the graphite into diamond and you can see that in the indenter loading force curve.

One big mistake here. Simple quasi static loading can be the constant increase over time of either the load (load control)or the penetration depth (displacement control) or a (dP/dt)/P (constant strain rate) toward a maximum value (load or penetration). Dynamic loading is understood, at least in micro-nano indentation as the superposition of a sinusoidal signal on top of the quasi static ones described above. The amplitude of this signal might be of few nm and provide access to the complex elastic modulus . But that is not it, out of one indentation curves it provides the evolution of H, E with depth every period of the sinusoidal. In this aspect it is much faster and rich than the static partial unloading schema.

we need to create loading force vs time as an input file before indentation. I have used single indents and multiple loading and partial unloading segments for my reserch

En suivant ces stratégies proposées , on peut effectuer des tests d'indentation sur des matériaux de manière efficace et obtenir des données précises sur leur propriétés mécaniques. ??Je voulais ajouter un point très important qui manque ici, c'est: ??La Répétabilité et La Validation, en répétant les tests pour assurer la reproductibilité des résultats et en validant les conclusions par la comparaison des résultats par autres techniques de caractérisation. Cordialement ??

FE-SEM, in particular, offers higher resolution imaging compared to traditional SEM and vastly superior to optical microscopy methods. This is crucial for accurately assessing the residual impression and crack lengths at the nanometer scale, which is often required in indentation testing of materials with fine microstructures.

Beim Farbeindringverfahren (DPT) reicht ein Abgleich des Kontrasts zwischen Eindringmittel (bspw. in roter Farbe) und einem wei?en Entwickler, der Risse deutlich herausstellt. Da wie in den zuvor genannten Punkten nicht klar ist, ob die PT-Verfahren gemeint sind oder doch die H?rteverfahren, macht eine weitere Erg?nzung an dieser Stelle (noch) keinen Sinn.

using AFM for indentation: you acquire height data and force data. during loading and unloading. first at a hard (no deformation at the forces you are applying) calibration sample (to find out the tip response to known forces) and then you repeat the procedure at the target samples or positions. ending up with one calibration loading/unloading curve on a hard sample and one for each target unknown hardness location. on an AFM system after indentation you can scan the topography of the sample to find out the actual deformation of your sample from the indentation.

1. Use a suitable measurement device to acquire indentation data during the test. 2. Common methods include using a microscope or displacement sensor. 3. Measure the depth of indentation accurately as the load is applied and removed. 4. Ensure the measurement device is calibrated and aligned properly. 5. Record the indentation data, including load and corresponding depth values, for analysis. 6. Follow standardized procedures and guidelines for data acquisition in indentation testing. The specific equipment and techniques for data acquisition may vary depending on the indentation testing setup and the material being tested.

The seven points given are basic steps to estimate accurate material strength but to obtain least uncertainty in the measurement two more steps are of paramount interest : 1. Controlled Environmental conditions during the measurement and 2. Equipment used capabilities for the test performed.

the analysis of indentation data can involve various techniques and considerations depending on the specific testing method and material being studied. Analyze the indentation data to determine material properties. 1. Calculate the hardness value using appropriate formulas or methods (e.g., Vickers, Rockwell, or Brinell hardness). 2. Consider the load-displacement curve to assess material behavior. 3. Evaluate other parameters such as elastic modulus, yield strength, and creep resistance if applicable. 4. Compare the results with known material properties or reference values. 5. Interpret and report the findings accurately and comprehensively.

Selection of indenter, load function, data analysis and interpretations are necessary. But the surface finish of the sample also plays major role in measuring the mechanical properties. If the sample is not well polished, the values will be unreliable. Also, if the sample is tapered from the surface or bottom, there is higher possibility of compliance factor. Thus load displacement will be influenced. Thus the requirement for indentation is to reduce the roughness of sample's surface below the tip diameter.

Interpreting indentation data requires expertise and knowledge of material behavior and nanomechanics. 1. Interpret the indentation data in relation to the material's mechanical properties. 2. Consider the hardness value as an indicator of material resistance to deformation or wear. 3. Assess the indentation size effect, which relates indentation size to material behavior at the nanoscale. 4. Analyze the load-displacement curve to understand material response, including elastic and plastic deformation. 5. Compare the obtained results with reference values or established material property databases. 6. Draw conclusions about the material's mechanical properties, such as hardness, elastic modulus, and plasticity.

Actually, fracture toughness of brittle materials can be calculated through the crack propagation while indentation. But this still needs to be investigated more in detail, however the dwell time has serious effect on crack propagation. Obviously, fracture toughness will vary in brittle materials due to the dwell time.

regarding nano-indentation, when dealing in the nano-meter scale remember that your samples resembles more a bunch of balls connected to each other (size of an hydrogen atom is around 0.1nm) than a continuous medium.