Numerical modelling of heat transfer in a tube furnace for steel wire annealing

In order to relieve stresses from cold drawing and to regain ductility, steel wires are annealed in furnaces under prolonged exposure to an appropriate temperature termed as ‘soaking’. This ensures the attainment of the required product quality. Literature suggests that the annealing processes are still determined by trial and error approach due to a lack of standards and also due to the proprietary nature of furnace designs. This paper investigates the heat transfer mechanism in a 12-metre long tube furnace filled with an inert gas and through which a cold-rolled steel wire travels at a specified speed. The length of the furnace is divided into three regions i.e. heating zone, soaking zone and cooling zone of which the heating and the cooling zones are given special attention. The methodology involves the use of Computational Fluid Dynamics by coupling both solid (steel wire) and gaseous zones (Hydrogen or Nitrogen). Radiation has been incorporated via a suitable model and convection taken care of by considering laminar flow of gases. The results suggest that the time needed in the heating zone is influenced by the choices of the surrounding atmosphere, speeds of gas and of the wire. These factors have an impact on the wire drawing speed and eventually on the overall productivity. It is also implied that the proposed numerical method may be used to shorten the ‘soaking’ time and hence to reduce energy consumption. The work demonstrates the usefulness of CFD in understanding and optimisation of the transfer process as well as highlights the challenges associated with numerical results

Temperature Dependent Mechanical Behavior of a Locally Restrained Graphite-Aluminum Laminated Plate under Bi-axial Loading

AbstractTemperature-dependent mechanical behavior of a locally restrained metal-matrix composite plate is investigated under uniform bi-axial compression. Thin rectangular plates of angle-ply and cross-ply laminate composed of Graphite-Aluminum composite are considered for the analysis. The plates are assumed to be locally restrained at their corner regions. Temperature-dependent me- chanical properties of the metal-matrix composite are used in the displacement-potential analysis of the elastic response. Results of deformed shapes as well as stress distributions are demonstrated as a function of temperature and fiber-orientation of the laminate

Thermal Ageing Effect on Electro-Mechanical Properties of Work Hardened High Conductive Copper Based Material

High conductive materials may undergo work hardening in the process of manufacturing and utilization as machine parts. Moreover, these materials face various thermal conditions at operational environment. As a consequence, the electro-mechanical properties of these materials get changed, which in turn affect their operational ability as these materials need to maintain high conductivity along with desirable mechanical properties. It gratifies to investigate the effect of thermal ageing on the electro-mechanical properties and microstructure of high conductive copper based material. In this work, the samples are prepared from copper ingot and alloy collected from local market. From the bulk material, long bars are taken, and they are at first homogenized and solution treated, and then they have been work hardened at different level in two conditions i.e., at room temperature and near recrystallization temperature. Thereafter, a series of experiments are carried out to determine the changes in conductivity, micro-hardness, strength, elongation and microstructure of samples as a function of thermal ageing temperature. Most of the mechanical properties after thermal ageing are found to be influenced quite significantly by work hardening.  &nbsp

Measurement of Potential Drop Distribution by Scanning the Closely Coupled Probes Sensor for Sensitive NDE of Shallow Surface Cracks

Highly sensitive nondestructive evaluation of shallow surface cracks is realized through the distributions of d-c potential drop obtained by scanning the closely coupled four-point-probes sensor around the crack. A methodology is developed for evaluating the depth and length of a three-dimensional surface crack from the potential drop profiles measured across and along the crack, where the experimental result is compared with the corresponding prediction of finite element analysis. The highly sensitive characteristic of the measured profiles is also extended to the potential drop imaging for identifying the location of cracks in a clear pictorial form. It is verified that the method is a powerful tool for characterizing very small fatigue cracks (sub-millimeter depth) on the surface of metallic structures