Repository: UIHistories Project: Book - Research on Campus (1949) [PAGE 14]

EXTRACTED TEXT FROM PAGE:

Materials and Structures

S H O W N on the preceding page is the giant compression-tension testing machine at the Talbot Laboratory of the University. Second largest in the world, and largest in this part of the country, it can apply a force of more than 3 million pounds to a test specimen clamped in its mighty jaws. It is one of a battery of machines that engineers at Illinois use in the testing of the metals on whose strength and reliability our industrial civilization rests. O n e of the most annoying and mysterious types of metal failure is that due to fatigue. A metal part subjected to millions of on-and-off cycles of repeated stress will finally break, though it has never had to withstand any single force big enough to cause immediate failure. T h e machine shown above right is a fatigue-test machine used in engineering studies being carried on at Illinois. T h e bolted joint mounted between the machine's jaws will be carried through hundreds of thousands of carefully controlled stress cycles, until it fails. All types of riveted, bolted, welded, and brazed joints are undergoing study. Not all of the research in structural engineering involves experiments with testing machines and instruments. M u c h important work is done with pencil, paper and calculating machines to develop the theories of behavior of buildings, bridges, airplanes and other structures. Many important problems are so complicated that they cannot be solved by formal mathematical techniques. For these problems, numerical methods of computation are being used and developed by engineers and mathematicians. Metallurgists, civil engineers, and applied mathematicians work together to determine the best materials for a given purpose, the best design for a given structure, and the reliability of various structures in actual service use. In addition, the physicists are supplementing these extensive engineering studies by taking u p fundamental work in the theory of the solid state. T h e empirical tests and measurements of engineers must ultimately rest upon a foundation in the basic theory of crystal structure and the properties of solid materials. Today, however, extensive tests which reproduce the

conditions of service use are essential to the design of practical devices. Shown at the far left is a special testing machine which rolls a railroad car wheel back and forth on a short section of track, applying loads u p to 50,000 pounds: twice the load on each wheel of a fully loaded coal car. Sidewise forces like those which occur when a train goes around a curve can also be applied. From studies with this machine, Illinois engineers are designing better wheels and rails. I n the picture above a concrete bridge is being tested. Studies of bridge floor slabs have been going on since 1936 under the direction of Professors N. M. Newmark and F. E. Richart. These studies have resulted in notable contributions to highway bridge design. T h e picture shows one phase of this work — tests of a model of a two-span I-beam bridge. These studies, analytical and experimental, have recently been honored by selection as one of the three outstanding research developments in Civil Engineering during the past ten years. At right, Professor Kenneth J. Trigger is measuring the wear of metal-cutting tools at various speeds and depths of cut. Contrary to what might be supposed, the lightest cut does not produce least wear on the tool; as cuts are made heavier, the work warms up, is softer, and thus is cut more readily. Tool wear is least at intermediate feeds and speeds; when the rate of cutting is too great, the tool wears rapidly.

Page 24

Page 25