AFM University | Nanomechanical e-Seminars

Nanomechanical e-Seminars

These recorded seminars feature researchers and experts presenting various nanomechanical principles, technologies, applications, and performance-optimizing tips.

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Sticky, Stressful Things

Running time: 50 minutes
April 21, 2010
Speakers: Holger Pfaff, Ph.D, Agilent Technologies; Marco Sebastiani, Ph.D. University of Rome “Roma Tre

Topic 1: Sticky Shapes — Testing the Adhesion of Biomimetic Attachment Devices
The ability of animals like geckos and spiders to walk along ceilings and walls has inspired fundamental researchers as well as engineers. Increased interest in biomimetics has led to ongoing efforts to understand the underlying mechanisms of these clinging capabilities and to transfer the working principles to technical products. Thorough comprehension of the underlying physics requires mechanical experiments on biomimetic structures over different load scales, ranging from nanonewtons to millinewtons. We will present experiments that help verify the influence of contact element shape/size and contribute to a better understanding of the attachment and detachment mechanisms of bio-inspired fibrillar attachment.

Topic 2: Residual Stress Effect on Nanomechanical Characterization of Thin Hard Coatings
A novel procedure is presented for the determination of surface elastic residual stress by instrumented sharp indentation, based on nanoindentation testing on focused ion beam (FIB) milled micro-pillars. Finite element modeling (FEM) of strain relief after FIB milling of annular trenches demonstrates that full relaxation of pre-existing residual stress state occurs when the depth of the trench approaches the diameter of the remaining pillar. Under this assumption, the average residual stress present in the coating can be calculated by comparing two different sets of load-depth curves: the first obtained at the center of stress-relieved pillars, the second on the undisturbed (residually stressed) surface. The effect of residual stress on fracture toughness and deformation modes of a TiN coating is analyzed and discussed here.

How Firm Is My Film

Running time: 1 hour 5 minutes
March 25, 2010
Speakers: Erik Herbert, Ph.D. (University of Tennessee-Knoxville; Bryan Crawford, Agilent Technologies

Topic 1: Characterizing the Mechanical Behavior of LiPON Films via Nanoindentation
Lithium phosphate oxynitride’s adequate ionic conductivity and stability against the Li/Li+ reference enables the operation of solid-state batteries. Because LiPON films experience significant mechanical stress during charge and discharge cycling, characterizing the mechanical behavior of these films is critical. Nanoindentation data provide the experimental evidence needed to determine hardness and modulus as a function of depth in a manner consistent with the body of literature that has examined nanoindentation on film/substrate systems.

Topic 2: Nanoindentation on Thin Films and the Examination of Rules-of-Thumb
Following a brief overview of nanoindentation, the quasi-static and dynamic indentation test methods will be discussed and some results from testing thin low-k dielectric materials and diamond-like carbon (DLC) films will be presented. Next, several general “rules-of-thumb” for indentation will be examined, including the 10% rule for maximum indentation depth on thin films, the 5% surface roughness criterion for obtaining repeatable measurements, and the 20x to 30x separation distance between indents.

I Know I Can, But Should I

Running time: 53 minutes
March 16, 2010
Speakers: Jenny Hay, Agilent Technologies, Jing-Jiang Yu, Agilent Technologies

AFM and Nanoindenting: The Pros and Cons of Stretching Functionality
AFMs are specially designed for high-resolution imaging, and Nanoindenters (NI) are specially designed for measuring mechanical properties. However, because AFMs and NIs share some operating principles, their functions have some degree of crossover. We will address the pros & Cons of using one type of instrument to perform the intended function of the other.

Application-based Tip Selection; Beyond Berkovich: Fabricating and Measuring with Custom Indenter Tips

Running time: 57 minutes
February 16, 2010
Speakers: Jenny Hay, AgilentTechnologies; Graham Cross PhD, Trinity College, Dublin Ireland

Topic 1 - Application-based Tip Selection
Although Berkovich diamonds are the most commonly used tips for instrumented indentation, many other tips are commercially available, including spheres, cones, flat punches, and other pyramids. In this presentation, we will explain how to choose the right tip for a particular application.

Topic 2 - Beyond Berkovich: Fabricating and Measuring with Custom Indenter Tips
The horizons of nanomechanical testing are being expanded by the high-resolution, high-precision manufacturing of custom nanoindentation tips. Novel tip geometries generate stress-field topologies tailored to test specific nano-object shapes and simulate emerging mechanical mass-nanofabrication methods. In this presentation, we will explain how to use a focused ion beam (FIB) to fabricate diamond and silicon tips as well as elaborate on issues critical to their use in nanoindention measurements. We will also provide special focus on flat-punch geometries as a successful method to access both small- and large-strain properties in ultrathin films of advanced materials such as block copolymers

Introduction to Scratch and Wear Testing; Micropillar Compression and Scratch Testing

Running time: 57 minutes
January 19, 2010
Speakers: Bryan Crawford, Agilent Technologies; Nikhilesh Chawla, FASM, Arizona State University

Topic 1 - Introduction to Scratch and Wear Testing
Scratch and wear testing provides important insight into mimicking product failures and applications. Multiple scratch and wear techniques are available for testing thin films, coatings, and bulk materials under different conditions. The scratch and wear processes along with failure modes and examples will be reviewed in this presentation.

Topic 2 - Micropillar Compression and Scratch Testing of Metal-Ceramic Nanolaminates
Metal-ceramic multilayered materials at the nanoscale have and excellent combination of strength toughness. Micropillars machined by focused ion beam (FIB) can be compressed with a nanoindenter to obtain uniaxial stress-strain behavior at small volumes. In addition, scratch testing of these materials, to quantify hardness and adhesion was conducted and will be described.

Obtaining Shear Relaxation Modulus and Creep Compliance of Linear Viscoelastic Materials by Instrumented Indentation

Running time: 60 minutes
November 5th, 2009
Speakers: Dr. Y.T. Cheng, University of Kentucky; and Jennifer Hay, Agilent Technologies

Obtaining Shear Relaxation Modulus and Creep Compliance of Linear Viscoelastic Materials by Instrumented Indentation
A novel method will be presented for determining two viscoelastic properties of polymers by indentation: shear relaxation modulus and creep compliance. Dr. Cheng will present his analysis and Dr. Oliver will present supporting experimental evidence. Having these properties allows the engineer to predict how a particular polymer will respond to expected stresses in a mechanical structure.

The Stress Field around an Elastoplastic Indentation/Contact -- Practical Tip Area Calibrations for Nanomechanical Testing

Running time: 61 minutes
October 22, 2009
Speakers: Gang Feng, Ph.D., Villanova University; Bryan Crawford, Agilent Technologies

The Stress Field around an Elastoplastic Indentation/Contact
For many common indenter geometries (e.g., cones and spheres), closed-form solutions are available for purely elastic indentation of a half space. These solutions are widely used in analyzing contact-induced phenomena (e.g., fractures and delaminations). Due to strong stress concentration, however, the materials under the indentation may deform plastically and the associated stress field may significantly deviate from that of purely elastic contact. Thus, rigorous closed-form solutions are not available for elastoplastic contacts. In this presentation, we will provide a simple closed-form approximation that matches finite element analysis nearly perfectly. The model can be used to analyze elastoplastic-contact-induced phenomena and provide valuable physical insights.

Practical Tip Area Calibrations for Nanomechanical Testing
This presentation will focus on fundamental tip calibrations using two methods for determining the tip area functions. The first method of calibration that will be covered is the use of the nominal tip area function for a specified tip geometry. This method utilizes geometry to determine the theoretical contact area as a function of penetration. Secondly, methods for determining the area function using reference materials with known mechanical properties will be discussed.

Instrumented Indentation Data Analysis; The ISO Standard for Indentation Testing

Running time: 70 minutes
October 6, 2009
Speakers: Dr. Warren C. Oliver, Nano Mechanics, Inc.and Jennifer Hay, Agilent Technologies

First, we will present the fundamentals of analyzing load displacement data from instrumented indentation experiments. We will discuss the basic challenges to acquiring accurate data, calibrating indenter geometries, and determining material properties. Next, we will address the challenges and benefits of the ISO standard 14577 for instrumented indentation testing. This standard is intended to dramatically increase the reproducibility of the hardness and modulus of materials determined at different laboratories.

Measurements of Mechanical Properties of Nanoscale Double-Clamped Beams

Running time: 61 minutes
August 7, 2009
Speakers: Dr. Jeffrey Kysar, Columbia University; Dr. Erik Herbert, University of Tennessee

As electronic and micro-electrical-mechanical systems become progressively smaller, it becomes more difficult to measure or otherwise characterize the mechanical properties of the constituent materials. One method that has recently emerged is to fabricate nanoscale specimens of the desired material into double-clamped beams suspended above a substrate using standard lithographic methods in a clean room environment. A nanoindenter can then be used to mechanically load the specimens in order to measure the force-displacement response, from which the mechanical behavior of the material can be inferred. We will show examples of two different materials that we have fabricated to free-standing double clamped beams with length of 7 microns, thickness 100 nm and width between 250 nm and 30 nm. We will then show results of the force-displacement data obtained and discuss the interpretation of the results to extract the mechanical properties.

Instrumented Indentation Testing of Bone

Running time: 64 minutes
July 9, 2009
Speakers: Dr. Sarandeep Huja, Ohio State University; Jennifer Hay, Agilent Technologies

Knowing the mechanical properties of bone is fundamental to predicting its performance and longevity. Instrumented indentation testing may be used to measure the elastic modulus and hardness of bone, but testing bone is more complex than testing traditional engineering materials. Special attention must be paid to the experimental protocol and analysis in order to achieve useful results. In this presentation, Ms. Jennifer Hay and Dr. Sarandeep Huja will explain the unique challenges of testing bone and discuss recent results.