(Dr. Thomas Kurfess, advisor)
"High Temperature Compression Testing of Hard Steels for Plastic Behavior Modeling"
A hard turning operation involves machining had-to-cut steels with the final objective of eliminating the grinding process by finishing the parts in a lathe. The advantages of this process include high productivity, low production cost, and flexible tooling among others. Recently, Finite Element Modeling (FEM) has extended its use to the field of machining operations to help in the optimization of these processes by providing forecasts through simulation. But the results from these simulations are only as good as the material data supplied to their cutting model. One of the major drawbacks of simulation is that occasionally there is not sufficient flow stress data about the workpiece material being modeled at the appropriate conditions. This thesis will address the deficiency of scarce material properties for AISI 52100, 1070 and 1053 steels by determining their flow stress behavior to large strains at elevated temperatures. This information is obtained by performing high temperature compression tests on specimens of these materials at temperatures ranging from 25°C to 800°C, which are typical in turning operations. Since the testing machine used was not properly equipped for this type of test, the compression test components had to be designed and manufactured. The data acquired from these tests is used to find a constitutive model that describes the flow stress of these materials with respect to temperature. This constitutive model may be used in conjunction with a machining model that describes the interaction between the workpiece and the cutting tool. These two models can be incorporated into a FEM software to simulate more realistically the effects on the workpiece and the cutting tool under various cutting conditions.