Surface Integrity Mastering for machined surfaces – MISU

The works performed in this project are experimental and numerical.

Experimental investigation have two functions: providing the nature and intensity of thermomechanical loads to be used in the models, allowing residual stress field measurments for the comparison with the numerical models.
Numerical models are dedicated to the application of thermomechnical sollicitations and parts rotation necessary for the obtention of residual stress fields.

Some improvements have been proposed for the 3 main objectives of the project.

The modeling of new processes allows to understand the physics of the phenomenom occuring in the process and leading to residual stresses generations,

The industrial environnement have been introduced in the turning simulations in ordrer to observe lubrification effect and tool wear. It appears that lubrification modes are not so important regarding the residual stresses generated. However, the tool wear is a critical aspect and can change drastically the results.

The students have obtained significant results and their models are starting to work. They will continue the improvements and the objective is to transfert their contribution in the software.

2 internationales conference with peer reviewed articles

The MISU project is related to the prediction of residual stresses induced by machining processes in order to master and improve the fatigue strength of highly loaded mechanical parts.
It contributes to the continuity of several works performed at the LTDS/ENISE since 2006. Former projects (3 PHD Thesis, 5 master of science) have led to the development of a new numerical method, called ‘hybrid method ‘, able to predict accurately the residual stresses fields. This method is based on equivalent thermomechanical loadings applied by the tool on the parts surfaces. It reproduces the residuals stress generation on real 3D parts. In this method, the chip formation and material flowing is not reproduced leading to fast computations.
This method has been set up for the finish turning operation featuring:
• Single cutting tool,
• Continuous cutting mechanisms,
• Low material removal rate,
• Open material removal operation (easy evacuation of the chip end heat),
• Revolving parts

This project is proposed to obtain a complete industrial solution for the prediction of residual stresses induced by finish turning. This implies a robust scientific approach, a dedicated software for non-expert people, a reliable and fast method to identify input data for the numerical models and output results leading to precise monitoring of the daily operation responsible of residual stress fields.
Another contribution of the project is the development of new numerical methods capable of reproducing more complex process like drilling, milling or reaming. This development will be integrated in the software gradually depending on their achievement levels.
At the end the software developed by ESI in his virtual machining suit will be released and disseminated to the industrial partners involved in the project (AIRBUS, CETIM, FRAMATOME, SAFRAN) and to the rest of enterprise concerned by surface integrity and fatigue life (automotive, medical prosthesis,…)