Alternate to standard tensile for determining young's modulus & yield

[j_mcdaniel]

Hi All,

I have been working on a product development project and have run into a snag that I was hoping I could get some advice on. We need to determine the mechanical properties of a thin-walled nickel tube. Specifically young's modulus and yield strength.

The current wall thickness of the tubes we are working with is approximately 0.010 inches but we will eventually be producing and testing tubes with wall thicknesses closer to 0.0015 inches. We have been experimenting with different means of measuring the mechanical properties of the tube and have recent heard about the use of nano-indentation testing. From what I've read, it is widely accepted that the sample young's modulus can be determined by this method but stress-strain data and properties like yield strength are not as commonly mentioned.

Does anyone know of someone/somewhere that specialises in nano-indentation testing? Or is there other potential methods that will let us obtain the properties we need?

Any input on the subject would be greatly appreciated. Regards,

Jesse McDaniel

 

[Astronuc]

Try these examples for now.

http://www.microphotonics.com/nht.html

http://www.csm-instruments.com/frames/nanohard.html

http://www.csm-instruments.com/frames/bullet/nhtapp.html


I have some contacts who have done testing of tensile properties using microscale specimens. So I will try to get some more information.

 

[Astronuc]

Sorry about the long delay. Finding the useful stuff takes a while.

A good source is a journal Experimental Mechanics.

For example - http://exm.sagepub.com/cgi/content/abstract/43/3/228 , Experimental Mechanics.2003; 43: 228-237.

William N. Sharpe, Jr.
Department of Mechanical Engineering, Johns Hopkins University, Baltimore, Maryland. sharpe@jhu.edu

Abstract

The measurement of mechanical properties using specimens whose minimum dimensions are of the order of micrometers is an important new area of experimental solid mechanics. One obvious application is in the area of microelectromechanical systems (MEMS) where the final product is on the millimeter or micrometer scale.

This paper describes techniques developed at Johns Hopkins University for tensile testing of materials used in MEMS. Polycrystalline silicon is currently the most widely used material; its modulus has been measured as 158 ±10 GPa, and 0.01, with fracture strengths ranging from 1.2 to 3.0 GPa depending upon the manufacturer. The properties of silicon nitride, silicon carbide, and electroplated nickel have also been measured and are presented. In addition to the quasi-static tensile tests, new techniques and procedures formeasuring strengths at stress concentrations in brittle thin-film materials, fatigue testing, and high-temperature testing are described.

Many new and important areas of research and technology are being led by disciplines other than mechanical and civil engineering, which have historically been closely related to experimental mechanics. Electrical engineers have led the development of MEMS, and chemical engineers and biologists are leading mechanical studies at the cellular level. These exciting new areas offer excellent opportunities to those with expertise in experimental mechanics, and some of these are presented.

Key Words: Tensile-testing • experimental mechanics • polysilicon • silicon nitride • Young’s modulus • MEMS

See also - http://www.atc-ssm.com/PDF/MTA-14A.pdf (Fahmy M. Haggag and Glenn E. Lucas, "Determination of Lüders Strains and Flow Properties in Steels from Hardness / Microhardness Tests", METALLURGICAL TRANSACTIONS A,VOLUME 14A, AUGUST 1983, 1607) It's rather dated though.

Another possible source - Journal of Materials Engineering and Performance

Also, Google on { "small specimen","tensile testing" }

 

[j_mcdaniel]

Thanks for the input. I had already contacted some nano-indenter manufacturers but some of the three you suggested weren't on my original list. I have actually been in contact with Fahmy Haggag, the author of one of the papers you cited. Based on some discussions I've had I am growing concerned about the validity of getting stress data from ball indentation tests. A lot of people seem to be just curve fitting hardness data to traditional unaxial tension data of known samples. The lead from Johns Hopkins may prove fruitful, thank you.

Jesse