Feasibility study of partial recrystallisation in multi-pass hot deformation process and application to calculation of mean flow stress

A feasibility study for handling the partial recrystallisation in multi-pass hot deformation where the heterogeneity of microstructure of deformed austenite is inherently accompanied is presented. The proposed model is based on modification of the conventional model in which the microstructure of deformed austenite at each pass is simply taken as being homogeneous during the multi-pass deformation. The usefulness of the modified model has been demonstrated by applying it to a four-pass oval–round (or round–oval) rod rolling sequence. The recrystallised fraction, austenite grain size (AGS) and mean flow stress at each pass computed from the modified model has been compared with those from the conventional model. The result showed that the recrystallisation behaviour and evolution of AGS at a given pass were dependent on the modelling method of the partial recrystallisation in the multi-pass rolling for the case studied. As the rolling speed increased, the difference between the mean flow stresses calculated by the conventional model and the proposed model was gradually larger in accordance with the contribution of partial recrystallisation.

Interlink decision making index (IDMI) : a simple tool/concept to assist decision making for sustainability part 2 : calculation and examples of IDMI

There is an apparent gap between the LCA or other assessment's outcomes and its effective application in the decision making process. It is needed to provide to the decision makers a simple, less human interfered mechanism that integrates all the key criteria (environmental, economic, technical and safety etc.). The proposed index: Interlink Decision Making Index (IDMI) has all these features: simple, interlink (all criteria) and automatically and quantified influence of critical criteria (ie. no human weighting needed) and is able to assist the multi-criteria decision making for sustainability based on the outcomes of specific assessments (eg. LCA, BIA etc.). The index represents a pure numerical value and does not necessarily have any physical meanings, but it reflects the total merits of a particular option once the normal decision making criteria and (up to two) critical criteria (Ce) have been chosen. Then, without arbitrarily weighting process, the comparison and selection of the best possible option, ie. decision can be made based on the derived IDMI results. Two hypothetical examples are presented in the part 2 of the paper to demonstrate the application of the IDMI concept and it's differences with the traditional "tabular method" in the decision making process.