Showing papers in "Journal of Engineering for Industry in 1979"

Ductile Fracture in Axisymmetric Extrusion and Drawing—Part 1: Deformation Mechanics of Extrusion and Drawing

Abstract: Abstract : This investigation applies theories on flow and fracture in metalworking processes to prediction of workability of materials in axisymmetric bar extrusion and drawing, with special reference to central bursting. Part 1 deals with the determination of deformation mechanics in extrusion and drawing. The matrix method is used as the method of analysis and is shown to be an efficient numerical method which provides useful information on the detailed deformation characteristics for various process variables. In part 2 the validity of a theory on ductile fracture was examined by experimental data found in the literature. Then, combining the formulation of fracture criteria with the deformation mechanics found in Part 1, the workability of materials in extrusion and drawing was determined. Workability in extrusion was examined for aluminum alloy 2024-T351, using data found in the literature, and experiments of workability in drawing were attempted for SAE 1144 colddrawn steel to test the prediction. The results of validation were inconclusive. Conclusive validation of the present workability theory in extrusion and drawing awaits more extensive and systematic experimental investigations, as well as theoretical calculations. (Author)

Flow stress model in metal cutting

Abstract: A model for the plastic deformation that occurs in metal cutting, based on dislocation mechanics, is presented. The model explains the fundamental deformation structure that develops during machining and is based on the well known Cottrell-Stokes Law, wherein the flow stress is partitioned into two parts; an athermal part which occurs in the shear fronts (or shear bands); and a thermal part which occurs in the lamella regions. The deformation envokes the presence of a cellular dislocation distribution which always exists in the material ahead of the shear process. This 'alien' dislocation distribution either exists in the metal prior to cutting or is produced by the compressive stress field which operates in front of the shear process. The magnitude of the flow stress and direction of the shear are shown to be correlated to the stacking fault energy of the metal being cut. The model is tested with respect to energy consumption rates and found to be consistent with observed values.

Reliability Analysis of Cutting Tools

Abstract: This paper is concerned with the reliability analysis of tool life based on the tool-wear values obtained from metal cutting experiments. From experimental results, a statistical distribution of tool wear was decided, and the distribution of tool life and the reliability function of cutting tools were derived. Further, it was shown that the reliability of cutting tools at a certain time was easily calculated from machining parameters and tool-wear limits by the use of reliability function.

Hydrazine Monopropellant Reciprocating Engine Development

Abstract: A hydrazine fueled piston engine for providing 11.2 kW was developed to satisfy the need for an efficient power supply in the range from 3.7 to 74.6 kW where existing nonair-breathing power supplies such as fuel cells or turbines are inappropriate. The engine was developed for an aircraft to fly to 21.3 km and above and cruise for extended periods. A remotely piloted aircraft and the associated flight control techniques for this application were designed. The engine is geared down internally (2:1) to accommodate a 1.8 m diameter propeller. An alternator is included to provide electrical power. The pusher-type engine is mounted onto the aft closure of the fuel tank, which also provides mounting for all other propulsion equipment. About 20 hrs of run time demonstrated good efficiency and adequate life. One flight test to 6.1 km was made using the engine with a small fixed-pitch four-bladed propeller. The test was successful in demonstrating operational characteristics and future potential.