MATERIAL TESTING LABORATORY

The Poulter Laboratory of SRI International has extensive facilities for the characterization of the constitutive and failure properties of materials at loading rates ranging from 10^-6 to 10⁶ per second and at temperatures of up to 2000 ^oC. Advanced metallography and microscopy facilities with chemical diagnostic equipment are also available.

Facilities for the mechanical characterization of materials include three computerized MTS servohydraulic tension/compression testing systems (100 kips, 20 kips, and 5 kips) and a MTS servohydraulic 50 kips-tension/compression, 20 kips-inch-torsion independently controllable multiaxial testing system. The axial displacement range for the four systems is 3 inches, and the rotation range for the torsional unit is 50 degrees. The 100-kip system is capable of intermediate strain rate testing with a stroke rate of up to about 10 inches/second. The other three systems operate at quasi-static strain rates. A fully equiped machine and weld shop is available for preparation of specimens.

We have a Physical Acoustics Corporation LOCAN 320 acoustic emission (AE) workstation with the capacity to record AE characteristics from up to 6 sensors and a transient recorder to record and analyze the digitized waveforms from a single sensor. The workstation also performs three-dimensional source location and post-test data filtering. We have a Questar long distance microscope with a magnification range from 35X at a working distance of 22 inches to 13X at 60 inches with attachments for video recording equipment.

The split Hopkinson torsional bar possesses unique capabilities for testing high-strength materials at high strain rates. Strain rates of 10⁴ per second are achieved. Strain levels imposed during a test can be varied up to a maximum shear strain of about 6 for high-strength materials. For performing tests at temperatures up to 800 ^oC, the Hopkinson bar is arranged to accommodate an infrared, four-element, 2-kW radiant heating furnace.

The high-temperature friction and wear testing apparatus is a tribometer of the pin-on-disk type, with the capability to contain and recirculate solid lubricant powders. It has been used to study wear and lubrication of ceramic diesel engine parts at temperatures between 20 and 800 ^oC. Sliding speeds of at least 2 m/s can be achieved, and normal loads in the range of 100 g to 10 kg can be applied to the wear pin.

High-temperature particle impact experiments are performed with a pneumatic gun consisting of a cylinder that is filled with nitrogen gas to a desired pressure, a set of 150-mm-long interchangeable stainless steel gun barrels having internal diameters ranging from 0.48 to 1.06 mm, and a quick opening valve. Particle velocities up to 400 m/s are attained.

A pneumatic launcher and a pendulum impact machine are available for dynamic fracture testing using the SRI-developed one-point-bend impact test technique. With this technique we can measure dynamic fracture initiation, propagation, and arrest properties at loading rates in excess of 10⁸ MPa-m^1/2/s.

High strain rate and high pressure impact testing is also available in our shock physics laboratory.

Dr. Donald A. Shockey Associate Lab Director

Phone (650) 859-2587 e-mail: dshockey@unix.sri.com

Dr. Richard W. Klopp Research Engineer

Phone (650) 859-6482 e-mail: rwklopp@unix.sri.com