Germain, Guenaël (2006) A contribution towards the optimisation of Laser Assisted Machining. PhD thesis Mécanique, matériaux et procédés, ENSAM 2006ENAM0051.
Abstract
Laser assisted machining (LAM) is a machining process that consists of heating the workpiece via a laser beam, upstream of the cutting tool. The mechanical properties of the workpiece, in the locally heated zone, are greatly reduced, which translates as an increased machinability. This work investigates the influence of laser assistance on the machiniability and the surface integrity of several materials: 42CrMo4 steel, 100Cr6 steel (heat treated to 57 HRc), and titanium alloy Ti6Al4V. The measurement of the cutting force is used to quantify the increase in machinability of the materials, as a function of the laser power and the cutting parameters. In certain configurations, the cutting force is decreased by 50 % for 100Cr6 and up to 40 % for the Ti6Al4V. The surface roughness is relatively insensitive to the laser power. However, the residual stresses tend towards positive values (tension) with the increase of the surface temperature. This modification of the residual stresses causes, for example, a decrease of 30MPa in the push-pull fatigue limit of the titanium alloy. At the same time the fatigue limit changes with the heat treatment caused by the laser at the cut surface during LAM. For the titanium alloy, the laser heat treatment creates a needle-shaped microstructure which is catastrophic in terms of fatigue. On the other hand, for the 100Cr6 steel, a thin layer of martensite(with strong compressive residual stresses) is created on the surface which increases the fatigue limit by approximately 70MPa. Numerical simulations of LAM and conventional machining have been undertaken in order to understand the role of the laser heat input on chip formation. The results show a decrease in the cutting force as laser power is increased. This is in agreement with the experimental work. The results obtained permit the optimization of the cutting parameters and to determine the mechanical and thermal loads on the cutting tool.
| Item Type: | PhD Thesis (PhD) |
|---|
| Thesis Supervisor: | L'Huillier, Jean-Pierre |
|---|
| Date: | December 2006 |
|---|
| Board of examiners: | Vannes, André Bernard and Dudzinski, Daniel and L'Huillier, Jean-Pierre and Poitou, Arnaud and Lebrun, Jean-Lou and Chabot, Jean-François and Auger, Stéphane and Lhuillier, François |
|---|
| Ecole Doctorale: | ED 432 ECOLE DOCTORALE SCIENCES DES METIERS DE L'INGENIEUR |
|---|
| Discipline: | Mécanique, matériaux et procédés |
|---|
| Collection (Fonds): | ENSAM |
|---|
| Institution: | ENSAM |
|---|
| Subjects: | 4. Materials Science, Mechanics and Mechanical Engineering |
|---|
| Uncontrolled Keywords: | Laser Assisted Machining, Machinability, Surface Integrity, Residual Stresses, Fatigue Strength, Numerical Simulation., Usinage Assisté Laser, Usinabilité, Intégrité de surface, Contraintes résiduelles, Tenue en fatigue, Simulation numérique. |
|---|
Statistiques de consultation
Repository Staff Only: edit this item
