Mohammad Jahazi, École de technologie supérieure

Professor Mohammad Jahazi is expert in forming and joining of high strength materials used in the energy and transportation industries. In particular, he has carried out extensive research on experimental and modeling of the influence of thermomechanical processing parameters on microstructure evolution during processing of high strength alloys. Since 2012, he is the holder of the industrial research chair in forming technologies of high strength materials, CM2P. Professor Jahazi’s research projects are based on industrial needs and in their vast majority are conducted in partnership with industry. During the last 25 years he has trained more than 100 graduate students and published over 400 articles in peer reviewed journals and conferences.

A Thermal-Metallurgical-Mechanical analysis of the quenching process of a high strength steel: application to an aircraft landing gear main fitting

Landing gear is one the most solicited components of an aircraft and within the landing gear assembly, the main fitting supports the most complex loading conditions of the entire aircraft. The main fitting is made of forged ultra high strength steel and its manufacturing process includes machining, heat treatment and surface treatment processes. The quench and temper (Q&T) heat treatment, required to yield the highest mechanical properties, is core to the manufacturing process. However, the complex geometry of the part, characterized by significant thickness changes from one point to another, results in different cooling rates and phase proportions during the quench process. The combination of non-uniform temperature distribution and phase transformation results in part distortion that requires rework and, in some cases, even part rejection. The trial-and-error practice, still widespread in industry, is not anymore viable due to economical and environmental prerogatives and therefore predictive capabilities based on scientific methodologies are needed. However, a comprehensive analysis of the quench process requires considering the mutual influences/interactions between thermal, metallurgical, and mechanical fields; therefore, accurate determination of the heat transfer as a function of location, temperature, and rate of cooling is essential. On the other hand, the thermal cycle including the heating, holding and cooling phases influences the kinetics of phase transformation. At the present time, the existing simulation models for quenching suffer from lack of precision due to the use of very simplified models. Hence, a more fundamental understanding of the interactions between thermal, metallurgical, and mechanical phenomena occurring during the hardening process needed to be developed in order to develop a reliable prediction model of the resultant distortion.

The project in collaboration with SAFRAN Landing Systems was defined around four main objectives:

1. Identification and simulation of heat transfer models for the quench hardening process

2. Development of a comprehensive TMM model, which can accurately describe the thermo-metallurgical loading conditions

3. Integrated Numerical Chain Simulation of the Quench hardening Process for Large Landing Gear Main Fittings including local microstructural and physical characteristics.

4. Development of a methodology to calculate the level of uncertainty for both the numerical predictions and the component inspections.

In the presentation, an overview of the project, the developed methodology, and some of the results will be presented.

Team:

Safran: Jean-Sebastien Lemyre-Baron, René Billardon, Nicolas Binot

ETS : Morteza Sadeghifar, Romain Alcaras, Jia-Hong Liu, Gamaliel Salazar, Daniel Olvera-Joseph, Chokri Delly, Baptist Portet, Ali-Aidibe, Henri Champliaud, Antoine Tahan, Mohammad Jahazi