Laser bending of high strength alloys

Abstract

Laser bending has emerged as a candidate process for bending sheet metal. The dimensional accuracy of parts produced by bending processes is a topical issue. As the dimensions of a laser bent part depend on the temperature field induced in the workpiece, the correct laser processing parameters are essential. This work reports on an investigation into the factors influencing the dimensions of laser formed thin plates of an α-β titanium and an AlCuMg aluminum alloy. The influence of the energy input on the bend angle is examined empirically and compared with an analytical model. Results show that the plastic strain is critically dependent on the energy supplied to the workpiece surface. The decreasing bend rate with increasing irradiations over the same track is evident. This is attributed to an increase in the sample section modulus due to the thickening of the material along the bending edge. Edge effects are apparent in the samples. These effects can be minimized by varying the line energy supplied to the plate surface with the in plate location. The conclusions drawn are that the dimensions of the final part and the rate of bending can be controlled primarily from the temperature field. In addition, the increase in the section modulus and the edge effects influence the dimensional accuracy.

The forming of mild steel plates with a 2.5 kW high power diode laser

“…4 are in general agreement with the findings of a number of workers [6,27,28] who have observed the existence of a linear relationship between laser bending angle and the number of irradiations. Yet such findings are in contrast to those of other researchers [22,23] who have reported a decaying increase in the bending angle with an increasing number of irradiations. This significant difference between the findings of this study and those of the latter workers is believed to be due to different degrees of local thickening and strain hardening of the 07 M20 mild steel sheet during HPDL bending.…”

“…It is known that strain hardening only becomes manifest for relatively thick sheets of typically more than 1 mm in thickness [22]. Moreover, if the sheet is relatively thin, as was the case in this study, the influence of strain hardening and material thickening along the bend edge can be considered to be almost insignificant when the number of irradiations is small [28].…”

A comparative investigation of the efficacy of CO2 and high-power diode lasers for the forming of EN3 mild steel sheets

“…However, such ®ndings are at odds with those of other researchers [24,25] who have reported a decaying increase in the bending angle with an increasing number of irradiations. This signi®cant di V erence between the ®ndings of this study and those of the latter workers is believed to be due to di V erent degrees of local thickening and strain hardening of the EN3 mild steel sheet during HPDL bending.…”

“…In more recent times the technique has been advanced through the development of a number of numerical [12±15], analytical [16] and ®nite element method (FEM) [17±21] mathematical models for various aspects of the laser forming process. Additionally, Hennige et al [22], Hennige [23] and Magee et al [24] have conducted studies to improve the dimensional accuracy of parts produced using laser forming, while similarly, both Sprenger et al [25] and Li and Yao [26] studied the e V ects of stress and strain on the quality of laser bends. Both Arnet and Vollersten [27] and Vollersten et al [28] have successfully demonstrated the technique's ability to form complex shapes.…”

An approach to form the dome shape by 3D laser forming

“…Though, similar to other studies [12,19] empirical based scanning strategies were executed experimentally. Figure 3 (a) shows result of a fundamental experiment with arbitrary concentric path.…”