30 Years of Nanoindentation with the Oliver-Pharr Method and Beyond: Main Session - 30 years of Nanoindentation with the Oliver-Pharr Method
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Nanomechanical Materials Behavior Committee
Program Organizers: Verena Maier-Kiener, Montanuniversitaet Leoben; Benoit Merle, University Of Kassel; Erik Herbert, Michigan Technological University; Samantha Lawrence, Los Alamos National Laboratory; Nigel Jennett, Coventry University
Monday 8:30 AM
February 28, 2022
Room: 259A
Location: Anaheim Convention Center
Session Chair: Benoit Merle, University Of Kassel; Samantha Lawrence, Los Alamos National Laboratory
8:30 AM Introductory Comments
8:40 AM Invited
Measurement of Hardness and Elastic Modulus by Depth Sensing Indentation: Improvements to the Technique Based on Continuous Stiffness Measurement: Warren Oliver1; Phani Sudharshan2; George Pharr3; 1KLA; 2ARCI; 3Texas A&M University
The method to measure hardness and elastic modulus of small volumes of material by instrumented indentation presented in the seminal works of Oliver and Pharr in 1992 and 2004, has revolutionized the field of small scale nanomechanical testing. Several recent advances in measurement electronics have enabled testing over a wider range of test conditions (speeds) using methodologies that were developed earlier, which requires a critical assessment. In the backdrop of the latest developments in instrumentation and test methodologies, we present an overview of the various factors affecting the precision and accuracy of the nanoindentation test results at different test conditions with specific focus on Continuous Stiffness Measurement (CSM) technique.
9:05 AM Invited
Nanoindentation's Top Ten Unexpected and Unusual Applications: George Pharr1; 1Texas A&M University
When Warren Oliver and I were doing our initial work on the development of nanoindentation testing in the late 1980's, it was quite clear what the initial applications would be. That was a time when thin film technology was rapidly developing for semiconductors, optics, and hard coatings, with each having pressing needs for small-scale mechanical characterization. However, what was not apparent was a plethora of unforeseen applications spanning a wide range of scientific, engineering, and non-technical fields. In this presentation, we discuss some of those, with an emphasis on the applications that have proven technically important as well as some that are truly unusual. The examples are drawn from fields as disparate and wide-ranging as biology, geology, space science, archaeology, anthropology, food science, fine art, medicine, cosmetics and personal care products.
9:30 AM Invited
On the Generality of the Contact Stiffness Relationship in Frictional Contact of Dissimilar Elastic Solids: Yanfei Gao1; Allan Bower2; 1University of Tennessee-Knoxville; 2Brown University
From a similarity analysis, the classic Sneddon relationship between contact stiffness and contact size is valid for axisymmetric, frictionless contact, in which the two contacting solids are approximated by elastic half-spaces. Deviation from this result critically affects the accuracy of the Oliver-Pharr methodology. When finite Coulomb friction exists between an elastic half-space and a flat-ended rigid punch with circular or noncircular shape, the correction factor is found to be a function of the friction coefficient, Poisson’s ratio, and the contact shape, but independent of the contact size. Analytical solutions based on Dundurs parameters are derived. For non-circular punch contact, the results can be represented using the equivalence between the contact problem and bi-material fracture mechanics. The correction factor is found to be a product of that for the circular contact and a multiplicative factor that depends only on the punch shape.
9:55 AM Break
10:15 AM Invited
From Instrumented Indentation to Nanoindentation and Beyond: Jean-Luc Loubet1; 1LTDS UMR CNRS 5513
In the eighties, intensive developments in instrumented indentation led in the eighties to the birth of instrumented nanoindentation. Several decades after, it is clear that these pioneering works gave rise to a success story that makes possible today to investigate small-scale mechanical properties under very extreme conditions (high temperature, high strain rate, severe environment …). We present here an historical overview of the key-developments that made nanoindentation one of the greatest tool to conduct research in material and mechanical sciences including tribology that lies in-between. We conclude this talk with a comparison between different contact models that aim at addressing one of the main issue of nanoindentation testing: pile-up or sink-in? Does it really matter?
10:40 AM Invited
Nanoindentation: From the 1-D Original to 2 Dimensions: John Pethica1; 1Trinity College Dublin
The talk will first describe the historical background and development of understanding of elastic relaxation of indents, why it became significant in the early 80s, and also its role in the creation of other techniques, especially AFM. The main part of the talk will present recent results on simultaneous normal and lateral indentation. The combination is important for basic understanding of friction and tribology when any plasticity is involved. We show the following: Static friction can be understood from the lateral deformation mechanism that follows initial plastic indentation, and depends on sink-in. The further development of lateral sliding and the limiting of junction growth is controlled and determined by interface friction and tip geometry, with good agreement with classical models. At sufficiently small normal loads and smooth tips, the purely interface sliding and largely wear-free friction seen in AFM and SFA can be observed.
11:05 AM Invited
10% Rule of Thumb for Indentation Mechanical Behavior: Fact or Fiction: Megan Cordill1; 1Erich Schmid Institute of Materials Science
One of the most common methods to measure the elastic modulus and hardness of thin films is to use nanoindentation and the well-known “10% rule of thumb”. The 10% rule of thumb has evolved to the understanding that elastic modulus and hardness can be measured at 10% of the film thickness with no or little influence from the substrate, even though only hardness was stated in the original Bueckle paper. While this guideline may hold true for some film-substrate systems and film thicknesses (greater than 1000 nm), it cannot and should not, be applied universally. Using several examples of hard-on-soft and soft-on-hard material systems of various thicknesses and finite element simulations, it will be demonstrated that the 10% rule of thumb, an outdated and misused guideline, should not be applied to evaluate the elastic modulus of thin films because it is a long-range property, substantially influenced by the substrate.
11:30 AM
Nucleation, Activation, and Looking for Perfection: Yield Points in Nanoindentation: David Bahr1; Michael Maughan2; Alexandra Burch3; 1Purdue University; 2University of Idaho; 3Los Alamos National Laboratory
Indentation testing of relatively defect free solids can produce yield point discontinuities in nanoindentation load-depth curves. The elastic-plastic transition (pop-in, excursion, load drop, etc.) can indicate either the activation of a pre-existing dislocation source or the nucleation of a dislocation source (which may or may not be itself a dislocation). This presentation addresses extracting information about both the strength and the sub-surface defect density from yield point distributions in metallic and molecular organic materials. Despite order of magnitude differences in mechanical properties, the distribution of yield shows striking similarities, allowing separating measurements that are tied to source activation from those related to dislocation nucleation. This then allows comparisons to computational simulations of “perfect” and defect-containing crystals to be used to validate models needed to predict an array of mechanical deformation mechanisms.