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Certain roll over protective structures, ROPS, require resistance to the propagation of brittle fractures at low temperatures. It is demonstrated that the Charpy test is not suitable for characterizing crack propagation resistance. A drop weight test of thin wall tubular specimens was developed which uses a brittle crack starter weld. This test provides an indication of the temperature transition from low to high crack propagation resistance. Because of toughened heat affected zones which can occur in cold formed steel this test is reliable only for hot formed tubes. The temperature transition to high propagation resistance can be determined with precracked Charpy and Dynamic Tear Energy, DT, specimens applicable to cold or hot formed steel. A weld joint simulation specimen was developed to determine energy absorption capacity and low temperature fracture behavior of ROPS joint designs and material.

INDUCTION heating, the authors show, has been successfully applied to the hardening of many types of gears. Over a million transmission gears have been produced with its aid and thousands of induction-hardened final-drive gears and pinions are giving satisfactory field service. It has resulted in lower costs (due to the substitution of carbon for alloy steel, fewer machining operations, and lower heat-treating costs) and improved quality (due to a lack of distortion and better stress distribution). The first part of this paper, by Mr. Kincaid, covers the equipment and methods used in handling various gear jobs. Then Mr. Knowlton covers the engineering tests and service performance of various types of induction-hardened gears.