METALLURGICAL & MECHANICAL Characterization

Professor Jeff Shield, Faculty Supervisor
Interim Specialist

855 N. 16th Street
Jorgensen Hall, Rooms 009 & 011
University of Nebraska
Lincoln, NE 68588-0298

phone: (402) 472-2378
email: jshield2@unl.edu
website: http://ncmn.unl.edu/mech_charact/

 

 

 

 

 

 

 

 

This facility contains a large variety of equipment to characterize the mechanical and physical properties of a wide range of materials. The facility focuses on using the many materials characterization aspects to perform failure analyses on components. Samples can be analyzed to determine the failure mode, and solutions to prevent further problems. Samples can be also prepared for the Electron Microscopy or X-ray Diffraction Facilities, if necessary.

Metallography utilizes various types of equipment to prepare and examine the microstructure of all types of materials. Available equipment includes a large fluid-cooled band saw, a water-cooled abrasive cut-off saw, and a diamond sectioning saw for sample sectioning; two hot presses for use with bakelite-type materials for mounting of samples, as well as facilities for cold-mounting of materials; a belt grinding station and two hand lapping stations for rough and coarse grinding; four variable speed stations for use with aluminum oxide and diamond compound for fine polishing. 'Leica DM 2500 M Optical Microscope', which includes differential interference contrast capabilities is available for sample viewing, and image analysis capabilities. Photographs may be taken as computer image, 35mm, or via thermal image printing.

Mechanical testing facilities include hardness testing equipment such as regular and superficial Rockwell, Knoop, and Vickers testers. Other testing facilities include a MTS 20,000 lb. servo-hydraulic material testing system, an Instron 10,000 lb. tensile testing machine, Satec 100,000 and 400,000 lb. machines, and Tinius-Olson instrumented Charpy impact and torsion testers.

Metallography is the art and science of preparing materials for examination in the microscope. The metallography lab contains equipment to section, mount, polish, and etch materials to enable the user to observe the microstructure of the material of interest, which can then be observed using light or electrons as the imaging method. Mechanical testing utilizes various equipment, which is usually designed to physically pull a material to failure. This may involve static or slowly applied loads such as are obtained with the presses, or a dynamic load such as is obtained with the Charpy impact testing machine. Both machines record load during testing in order to measure and determine the strength parameters of the material. Hardness testing involves using a known load and a known indenter shape which is then pressed into a material. The depth of penetration of the indenter is proportional to the hardness of the material. Hardness data can be used to infer other mechanical properties of the material. The hardness testers available include both macrohardness and microhardness testers which produce indentations which are fairly large (.20" in diameter) to extremely small (a thousandth of an inch).

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