Sheet metal forming at elevated temperature is not much used in industries but it is going to be a very important process in the future. The present work is aimed to investigate the formability of austenitic stainless steel 316 at elevated temperatures. Limiting drawing ratio and thickness of the drawn cup are the indicators of formability in deep drawing. In the present investigation circular blanks are deep drawn at room temperature, 150 °C and 300 °C using a 20 ton hydraulic press coupled with a furnace. Finite element simulations are carried out using Dynaform with LS-Dyna solver. Simulations and experimental results show an increase in the limiting drawing ration as the temperature increases and a decrease in the thickness of the drawn cup without any fracture. An artificial neural network model is developed for the prediction of the cup thickness at different locations. Based on the input variables, such as distance from the center of the cup, temperature and LDR, a back propagation neural network model to predict the thickness as output was develop. The comparison between these sets of results indicates the reliability of the predictions. It was found that there is a good agreement between the experimental and predicted values.

Experimental and numerical investigation of formability for austenitic stainless steel 316 at elevated temperatures

Finite Element Simulation Studies of AISI 304 for Deep Drawing at Various Temperatures

Simulated re-entry tests of reusable thermal protection systems for spacecraft are being conducted in an arc-heated, high-enthalpy wind tunnel. The surface temperature is usually measured by remote pyrometers. Since the material is heated by the radiating plasma, signal disturbances are present when measuring through the plasma. Furthermore the normal spectral emittance is subject to changes, depending on plasma conditions. In order to avoid these drawbacks a new kind of pyrometer for the measurement of the rear side temperature was designed. This article describes the design and the application of the miniaturized pyrometer in the plasma wind tunnel

Linear pyrometer for investigations of thermal protection systems

When studying the radiative emission of material, the sample surface temperature provides essential data for the interpretation of emission spectra. Surface temperature measurement, however, often remains a complex metrological problem. Difficulties are increased when the surface temperature of semi-transparent scattering media at high temperature - between 1000 K and 2500 K - is required. In this work, the technique of pyrometry at the Christiansen frequency was used to determine the surface temperature of ceramics. The objective of the study was to quantify the accuracy of this measurement technique. The uncertainty of temperature was calculated. However, given the difficulty of this estimation, a reliability indicator was also determined, defined as the maximum discrepancy between temperatures measured by two different techniques, namely pyrometry at the Christiansen frequency and infrared thermography. Comparison of temperature measurements are presented for a sintered sample of yttria stabilized zirc...

Surface temperature measurement of semitransparent ceramics at high temperature Comparison between pyrometry at the Christiansen frequency and infrared thermography

O. Loesener

Papers

A new far-infrared pyrometer for radiation temperature measurement on semitransparent and absorbing materials in an arc-heated wind tunnel