Mechanistic modelling of 5-axis milling using an adaptive depth buffer
Mechanistic modelling of surface machining with a toroidal end mill is presented in this work for 5-axis machining. A graphical representation of tool movements (using tooth swept sectors or the swept surface of the tool) is rendered using a widely available rendering engine, whereby the in-process chip geometry and tool edge contact length are determined by an adaptive and local depth buffer. Owing to the chip geometry being highly dependent on the feedrate, a detailed derivation of the relative tool-workpiece velocity is presented based on the kinematics of a tilt-rotary table configuration. The mechanistic modelling is verified with experimental results and found to agree to within 7% of the peak-to-peak forces.
A System for Monitoring the Machining Operation by Referring to a Predicted Cutting Torque Pattern
Summary A system for predicting the cutting torque by using a geometric modelling system, and its application to verification of NC data and monitoring of the cutting process are described in the paper. The cutting process is simulated geometrically in a modelling system. Based on data obtained from the geometrical simulation and on technological data of the NC program, the cutting torque is estimated, by using an empirical equation, as a linear combination of the volume of the removed material and of the tool-workpiece contact surface area. The torque measured in the experiments was in good agreement with the preliminarily estimate. The system also proved to be applicable when machining a cast part with geometrical inaccuracies within a few millimeters.
Evolution of carbide precipitates in Hastelloy N joints during welding and post weld heat treatment
Abstract The effects of welding and post weld heat treatment (PWHT) on the morphology, composition and lattice parameter of the precipitates in the welding joints of Hastelloy N alloy have been investigated. Joint samples were prepared using a gas tungsten arc welding process with ERNiMo-2 fillers, and then solid-solution treated at 1100 °C for 20 min. After welding, eutectic M6C carbides can be observed in the heat affected zones (HAZ) and weld zones (WZ). These eutectic M6C carbides become spheroidized during the following PWHT. The concentration of Si decreases during the transformation from the primary ones to eutectic ones, and then increases during the spheroidizing process. The total concentration of Si + Cr in M6C carbides remains stable during welding and PWHT. At the same time, the heat leads to the outward diffusion of Mo from the M6C carbides, which results in a decrease of the lattice parameter.