Michael Evans Graham

Laser Forming of Varying Thickness Plate—Part I: Process Analysis

Laser forming (LF) is a non-traditional forming process that does not require hard tooling or external forces and, hence, may dramatically increase process flexibility and reduce the cost of forming. While extensive progress has been made in analyzing and predicting the deformation given a set of process parameters, few attempts have been made to determine the laser scanning paths and laser heat conditions given a desired shape. This paper presents a strain-based strategy for laser forming process design for thin plates with varying thickness, which is utilized in determining the scanning paths and the proper heating conditions. For varying thickness plates, both the in-plane membrane strain and the bending strain need to be accounted for in process design. Compared with uniform thickness plate, the required bending strain varies with not only the shape curvature but also with the plate thickness. The scanning paths are determined by considering the different weight of bending strain and in-plane strain. A thickness-dependent database is established by LF finite element analysis simulation, and the heating conditions are determined by matching the ratio of bending strain to in-plane strain between the required values and the laser forming values found in the database. The approach is validated by numerical simulation and experiments using several typical shapes.

Effects of Scanning Schemes on Laser Tube Bending

Four laser scanning schemes for tube bending, including point-source circumferential scanning, pulsed line-source axial procession, and line-source axial scanning without and with water cooling are investigated in numerical simulation. The coupled thermomechanical model established using the finite element method is validated and applied to predict the bending deformation and help better understand bending mechanisms under different schemes. The influence of important parameters such as beam coverage, scanning velocity and cooling offset on the deformation is investigated in detail. Parametric studies are carried out to determine proper processing windows at which the largest bending can be obtained. The deformation characteristics, including the wall thickness variation and the cross-section distortion produced by different scanning schemes are analyzed, along with the processing efficiency. DOI: 10.1115/1.2113047

Laser forming: Industrial applications

Laser forming is currently a laboratory technique that is beginning to see industrial applications. In this paper, we discuss practical concerns and review the progress of laser forming at GE Global Research. Two applications, 3D shape tuning and precision tube bending, are presented. Topics include considerations for industrial applications, methods for qualifying a process window, materials characterization, path planning, and system integration.Laser forming is currently a laboratory technique that is beginning to see industrial applications. In this paper, we discuss practical concerns and review the progress of laser forming at GE Global Research. Two applications, 3D shape tuning and precision tube bending, are presented. Topics include considerations for industrial applications, methods for qualifying a process window, materials characterization, path planning, and system integration.

Large diameter and thin wall laser tube bending

Large diameter and thin wall tube bending is challenging for mechanical methods. Although laser tube bending has been used for <2” diameter tubes, larger diameter laser tube bending is not thoroughly studied yet. This paper reports the challenges and our progress in large diameter laser tube bending. Special issues such as cooling, surface non-uniformity, beam shape and cross section deformation were investigated in comparison with small diameter tube bending.Large diameter and thin wall tube bending is challenging for mechanical methods. Although laser tube bending has been used for <2” diameter tubes, larger diameter laser tube bending is not thoroughly studied yet. This paper reports the challenges and our progress in large diameter laser tube bending. Special issues such as cooling, surface non-uniformity, beam shape and cross section deformation were investigated in comparison with small diameter tube bending.

Effects of scanning schemes on laser tube bending

Four laser scanning schemes for tube bending, including point-source circumferential scanning, pulsed line-source axial procession, line-source axial scanning without and with water cooling are investigated in numerical simulation. The coupled thermo-mechanical model established using the finite element method is validated and applied to predict the bending deformation and help better understand bending mechanisms under different schemes. The influence of important parameters such as beam coverage, scanning velocity and cooling offset on the deformation is investigated in detail. Parametric studies are carried out to determine proper processing windows at which the largest bending can be obtained. The deformation characteristics, including the wall thickness variation and the cross-section distortion produced by different scanning schemes are analysed, along with the processing efficiency.Four laser scanning schemes for tube bending, including point-source circumferential scanning, pulsed line-source axial procession, line-source axial scanning without and with water cooling are investigated in numerical simulation. The coupled thermo-mechanical model established using the finite element method is validated and applied to predict the bending deformation and help better understand bending mechanisms under different schemes. The influence of important parameters such as beam coverage, scanning velocity and cooling offset on the deformation is investigated in detail. Parametric studies are carried out to determine proper processing windows at which the largest bending can be obtained. The deformation characteristics, including the wall thickness variation and the cross-section distortion produced by different scanning schemes are analysed, along with the processing efficiency.

Thermal forming process design

Thermal forming metallic components with laser energy is evolving into a viable manufacturing technology with commercial applications spanning diverse domains such as high-volume automotive part production, microelectronic device fabrication and shape tuning turbomachinery airfoils. Research activities are concentrated on quantifying the underlying mechanisms and resulting strain fields and in devising thermal forming strategies and schedules to yield a desired part shape. In this paper we outline a generalized empiric-numeric approach to determine thermal forming induced strain fields and demonstrate results with the nickel-based alloy 718, widely used in aerospace applications. The resulting strain field transfer functional is central to devising thermal forming treatments. Path planning strategies and results of thermal forming a turbomachinery compressor airfoil—a thin freeform 3D shape—are also demonstrated.Thermal forming metallic components with laser energy is evolving into a viable manufacturing technology with commercial applications spanning diverse domains such as high-volume automotive part production, microelectronic device fabrication and shape tuning turbomachinery airfoils. Research activities are concentrated on quantifying the underlying mechanisms and resulting strain fields and in devising thermal forming strategies and schedules to yield a desired part shape. In this paper we outline a generalized empiric-numeric approach to determine thermal forming induced strain fields and demonstrate results with the nickel-based alloy 718, widely used in aerospace applications. The resulting strain field transfer functional is central to devising thermal forming treatments. Path planning strategies and results of thermal forming a turbomachinery compressor airfoil—a thin freeform 3D shape—are also demonstrated.