Hot working of aluminum alloy 7075
Large deformation, constant true strain rate, isothermal compression tests have been conducted on the aluminum alloy 7075 at strain rates which ranged from 103 to 1 sec1 and temperatures which spanned the practical forging temperature range of 3250C 4250 C. In this strain rate and temperature regime the stress-strain curves show very little strain hardening or softening, and the relationship between the (visco) plastic strain rate iP, the absolute temperature T, and the flow stress a can be represented well by the classical one-dimensional equation:
The Validity of Simulating Tests in Evaluating Lubricants for Deformation Processes
One of the most significant stumbling blocks in establishing correlation between theory and application in deformation processes has been the uncertainty attached to the magnitude of interface friction. Even the simplest theory must account for the effects of friction on forces, power requirements and material flow, and the magnitude of this friction must be known-together with the correct value of the flow stress-if the validity of a theory is to be checked. While there is still a great scarcity of data on flow stresses at relevant strain rates and temperatures, a beginning has, nevertheless, been made by determining flow stresses in plastometers. No comparable development occurred with regards to friction. There is no universal, basic method of determining friction under conditions applicable to deformation processing; instead, a numerical value representing friction (in the form of a coefficient of friction, or an interface shear strength) is usually derived from experimental data through the utilization of a theory, often at the same time when proof of the validity of the very same theory is sought. Under these circumstances, there is a danger of friction becoming an adjustable, variable “constant” chosen at convenience. It would be highly desireable, therefore, that friction should be determined in simple tests that are readily evaluated, rely on a minimum of theoretical or simplifying assumptions, yet simulate actual deformation processing conditions sufficiently to make the results relevant, and to allow lubricant evaluation with a measure of confidence. This paper aims at clarifying to some degree the suitability of some existing test techniques for these purposes.
Metal Deformation Processes: Friction and Lubrication
Abstract : The importance of friction and lubrication in deformation processes such as rolling, wire drawing, extrusion, forging, and sheet metalworking has long been recognized by those practicing these processes. The book presents a comprehensive treatment of the entire field, including friction and lubrication in the deformation processing of the more common materials.