DYNAMIC PROPERTIES FOR MODELING AND SIMULATION OF MACHINING: EFFECT OF PEARLITE TO AUSTENITE PHASE TRANSITION ON FLOW STRESS IN AISI 1075 STEEL

• Published in: Machining science and technology Vol. 15; no. 1; pp. 1 - 20
• Main Authors: Burns, Timothy J., Mates, Steven P., Rhorer, Richard L., Whitenton, Eric P., Basak, Debasis
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA Taylor & Francis Group 01.01.2011; Taylor & Francis
• Subjects: AISI 1075 steel; Applied sciences; Computer simulation; Condensed matter: structure, mechanical and thermal properties; Dynamics; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Flow stress; Fundamental areas of phenomenology (including applications); High-speed machining; Johnson-Cook model; Measurement and testing methods; Mechanical engineering. Machine design; Microstructure; Phase transformations; Physics; Solid mechanics; Solid-solid transitions; Specific phase transitions; split-Hopkinson pressure bar; Structural and continuum mechanics; Yield strength; Constitutive equation; Austenitic stainless steel; Heat treatment; Kolsky bar; Machining; AISI 1075 steel; Dynamic properties; High temperature; Cutting speed; Test bar; Modeling; Phase transitions; Dislocation; high-speed machining; Johnson-Cook model; Inelasticity; Dynamic measurement; Austenitic steel; split-Hopkinson pressure bar; High speed; Dynamic model; Strain rate; Plastic flow; Thermomechanical properties; Experimental study; Heat source; Thermal activation; Carbon steel; Pulse heating; Flow stress
• DOI: 10.1080/10910344.2011.557943
• ISSN: 1091-0344

The Pulse-Heated Kolsky Bar Laboratory at the National Institute of Standards and Technology (NIST) has been developed for the measurement of dynamic properties of metals. With this system, a small sample can be pre-heated from room temperature to several hundred degrees C in less than a second, prior to rapid loading in compression at strain rates up to the order of 10 4 per second. A major focus of this research program has been on investigating the influence of the heating rate and time at temperature on the flow stress of carbon steels, for application to the modeling and simulation of high-speed machining operations. The unique pulse heating capability of the NIST Kolsky bar system enables flow stress measurements to be obtained under conditions that differ significantly from those in which the test specimens have been pre-heated to a high temperature more slowly, because there is less time for thermally activated microstructural processes such as dislocation annealing, grain growth, and solid state phase transformations to take place. New experimental results are presented on AISI 1075 pearlitic steel samples that were pulse-heated up to and beyond the austenite formation temperature of the material (723 °C). The data show that the flow stress decreased by about 50 % due to a phase transformation in the microstructure of the material from the stronger pearlitic phase to the weaker austenitic phase. As a result, the constitutive response behavior of the material cannot be modeled by a fixed-parameter constitutive model, like the Johnson-Cook flow stress model that is widely used in computer simulations of high-speed machining processes.