The Effect of Nonconventional Laser Beam Geometries on Stress Distribution and Distortions in Laser Bending of Tubes

2006 ◽  
Vol 129 (3) ◽  
pp. 592-600 ◽  
Author(s):  
Shakeel Safdar ◽  
Lin Li ◽  
M. A. Sheikh ◽  
Zhu Liu
Keyword(s):  
Laser Beam ◽  
Laser Scanning ◽  
Thermal Stresses ◽  
Laser Forming ◽  
Beam Diameter ◽  
Hydraulic Systems ◽  
Tube Bending ◽  
Laser Bending ◽  
Scanning Velocity ◽  
Laser Tube

Laser forming is a spring-back-free noncontact forming method that has received considerable attention in recent years. Compared to mechanical bending, no hard tooling, dies, or external force is used. Within laser forming, tube bending is an important industrial activity with applications in critical engineering systems such as heat exchangers, hydraulic systems, boilers, etc. Laser tube bending utilizes the thermal stresses generated during laser scanning to achieve the desired bends. The parameters varied to control the process are usually laser power, beam diameter, scanning velocity, and the number of scans. The thermal stresses generated during laser scanning are strongly dependent upon laser beam geometry. The existing laser bending methods use either circular or rectangular beams. These beam geometries sometimes lead to undesirable effects such as buckling and distortion in tube bending. This paper investigates the effects for various laser beam geometries on laser tube bending. Finite element modeling has been used for the study of the process with some results also validated by experiments.

Experimental and 3D Finite Element Studies of CW Laser Forming of Thin Stainless Steel Sheets

2000 ◽  
Vol 123 (1) ◽  
pp. 66-73 ◽  
Author(s):  
Guofei Chen ◽  
Xianfan Xu
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
Laser Scanning ◽  
Continuous Wave ◽  
Laser Forming ◽  
Beam Diameter ◽  
Element Analysis ◽  
Scanning Velocity ◽  
3D Finite Element ◽  
Steel Sheets

Laser forming as a springback-free and noncontact forming technique has been under active investigation over the last decade. Previous investigations are mainly focused on forming of large and thick workpieces using high power lasers, with less work on precision, micro-scale bending of small and thin sheets. In this work, a 4 W continuous wave argon ion laser is used as the energy source, and the laser beam is focused to a beam diameter of tens of micrometers to induce bending of thin stainless steel sheets. When the laser scanning velocity is above 8 mm/s, bending can be explained by the temperature gradient mechanism, while decreasing the scanning velocity leads to the buckling mechanism of bending. The bending angle is measured at various processing conditions. A fully 3D finite element analysis is performed to simulate the thermo-elasto-plastic deformation process during laser forming. Experimental measurements and computational results agree in trend, and reasons for the deviation are discussed.

scholarly journals Experimental Investigation of the Effects of Irradiating Schemes in Laser Tube Bending Process

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1123
Author(s):  
Mehdi Safari ◽  
Ricardo J. Alves de Sousa ◽  
Jalal Joudaki
Keyword(s):  
Laser Beam ◽  
Contact Process ◽  
Steel Tube ◽  
Thickness Variation ◽  
Tube Bending ◽  
Lateral Bending ◽  
Bending Angle ◽  
Laser Tube ◽  
Bending Process ◽  
Thickness Variations

The laser tube bending process (LTBP) process is a thermal non-contact process for bending tubes with less springback and less thinning of the tube. In this paper, the laser tube bending process will be studied experimentally. The length of irradiation and irradiation scheme are two main affecting process parameters in the LTBP process. For this purpose, different samples according to two main irradiation schemes (Circular irradiating scheme (CIS) and axial irradiating scheme (AIS)) and different lengths of laser beam irradiation (from 4.7 to 28.2 mm) are fabricated. The main bending angle of laser-bent tube, lateral bending angle, ovality, and thickness variations is measured experimentally, and the effects of the irradiating scheme and the length of irradiation are investigated. An 18 mm diameter, 1 mm thick mild steel tube was bent with 1100 Watts laser beam. The results show that for both irradiating schemes, by increasing the irradiating length of the main and lateral bending angle, the ovality and thickness variation ratio of the bent tube are increased. In addition, for a similar irradiating length, the main bending angle with AIS is considerably higher than CIS. The lateral bending angle by AIS is much less than the lateral bending angle with CIS. The results demonstrate that the ovality percentage and the thickness variation ratio for the laser-bent tube obtained by CIS are much more than the values associated with by AIS laser-bent tube.

Analysis and Prediction of Edge Effects in Laser Bending

2000 ◽  
Vol 123 (1) ◽  
pp. 53-61 ◽  
Author(s):  
Jiangcheng Bao ◽  
Y. Lawrence Yao
Keyword(s):  
Residual Stress ◽  
Edge Effects ◽  
Laser Scanning ◽  
Laser Forming ◽  
Stress Distributions ◽  
Rate Dependency ◽  
Laser Bending ◽  
Numerical Investigations ◽  
Wide Range ◽  
Scanning Path

Laser forming of sheet metal offers the advantages of requiring no hard tooling and thus reduced cost and increased flexibility. It also enables forming of some materials and shapes that are not possible now. In single-axis laser bending of plates, the bending edge is found to be somewhat curved and the bending angle varies along the laser-scanning path. These phenomena are termed edge effects, which adversely affect the accuracy of the bending and result in undue residual stress. Numerical investigations are carried out to study the process transiency and the mechanism of the edge effects. Temperature dependency of material properties and strain-rate dependency of flow stress are considered in the numerical simulation to improve prediction accuracy. Numerical results are validated in experiments. Patterns of edge effects and resultant residual stress distributions are examined under a wide range of conditions. A more complete explanation for the mechanism of the edge effects is given.

An Experimental Study on Bending Process of AISI 304 Steel Sheets by using Diode Laser Forming

2014 ◽  
Vol 1 (1) ◽  
pp. 14-30
Author(s):  
Alfonso Paoletti
Keyword(s):  
Laser Beam ◽  
Diode Laser ◽  
Process Parameters ◽  
Laser Forming ◽  
Laser Bending ◽  
Aisi 304 ◽  
Steel Sheets ◽  
Metal Sheets ◽  
Bending Process ◽  
Aisi 304 Steel

Laser bending is a promising technique utilised in order to deform metal sheets that offers the advantage of requiring no hard tooling and no external forces, thus reducing cost and increasing flexibility. Laser forming involves a complex interaction of many process parameters, ranging from those connected with the irradiation of the laser beam to those regarding the thermal and mechanical properties of the workpiece material. The present work is focused on the laser bending of AISI 304 steel sheets by using of a diode laser. The influence of process parameters, such as the power of laser beam and the scanning speed as well as the metal sheet thickness on the bending angle has been taken into account. The investigation has also analysed the effect of rolling direction of the metal sheets and the conditions of cooling on the bending process.

Effects of Scanning Schemes on Laser Tube Bending

2005 ◽  
Vol 128 (1) ◽  
pp. 20-33 ◽  
Author(s):  
Jie Zhang ◽  
Peng Cheng ◽  
Wenwu Zhang ◽  
Michael Graham ◽  
Jerry Jones ◽  
...  
Keyword(s):  
Line Source ◽  
Laser Scanning ◽  
Thickness Variation ◽  
Tube Bending ◽  
Thermomechanical Model ◽  
Processing Efficiency ◽  
Scanning Velocity ◽  
Parametric Studies ◽  
Wall Thickness Variation ◽  
Axial Scanning

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.

scholarly journals Effects of Forced Cooling In Laser Forming

2019 ◽  
Vol 8 (10) ◽  
pp. 3782-3787
Keyword(s):  
Numerical Model ◽  
Research Work ◽  
Three Dimensional ◽  
Weight Ratio ◽  
Laser Forming ◽  
Beam Diameter ◽  
Forming Process ◽  
Scanning Velocity ◽  
Cooling Conditions ◽  
Forced Cooling

This paper presents the numerical bending studies of the alloy sheet of Magnesium M1A to achieve the bigger bending angle in a single laser forming process. A three-dimensional model of finite elements was created and different simulations were performed for sheet laser bending. Magnesium alloys are difficult-to-form yet have huge applications in automobile and aerospace industries because of its high strength to weight ratio. To study the sheet bending method and effect of various process parameters including laser scanning velocity, beam diameter and laser power, a three-dimensional numerical model was developed. The developed numerical model was designed with ABAQUS Simulia and validated with the published numerical model. On the validated numerical model, a further number of simulations were performed to understand the effects of forced cooling conditions in single scan laser forming process. This research work concluded that forced cooling conditions in laser forming can be used to increase the bend angle in a single scan.

Research on the Mechanisms of Laser Forming for the Micro-Structural Element

2008 ◽  
Vol 575-578 ◽  
pp. 1145-1150
Author(s):  
Ying Jin ◽  
Jian Hua Wu ◽  
Yong Jun Shi ◽  
Hong Shen ◽  
Zheng Qiang Yao
Keyword(s):  
Thermal Stresses ◽  
Element Model ◽  
Laser Forming ◽  
Forming Process ◽  
Structural Element ◽  
Laser Bending ◽  
Forming Mechanism ◽  
Thermal Transfer ◽  
Conventional Analysis ◽  
The Finite Element Model

Laser forming of a micro-structural element involves a complex thermoplastic process. Numerous efforts had been made on the mechanisms of laser forming for macro-size elements, such as temperature gradient mechanism, buckling mechanism and upsetting mechanism, etc. It is found that the three mechanisms cannot depict fully the process of deformation in the macro-size element forming, let alone meet the needs of the micro-size one. Considering the laser inducing thermal stresses with size factors differing from the conventional analysis, it is essential to reveal the mechanisms dominating the forming process to accurately control the bending angle of a tiny plate. By studying the thermal transfer and elastic-plastic deformation of micro-structural element laser forming, the forming mechanism is explained within the micro size. The finite element model for laser bending is constructed for simulation. The stimulation results are agreement with the experimental data.

Model of Radiation and Heat Transfer in Laser-Powder Interaction Zone at Selective Laser Melting

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
A. V. Gusarov ◽  
I. Yadroitsev ◽  
Ph. Bertrand ◽  
I. Smurov
Keyword(s):  
Laser Beam ◽  
Selective Laser Melting ◽  
Metallic Powder ◽  
Single Line ◽  
Powder Layer ◽  
Width Ratio ◽  
Beam Diameter ◽  
Laser Melting ◽  
Scanning Velocity ◽  
Melt Pool

A model for coupled radiation transfer and thermal diffusion is proposed, which provides a local temperature field. Single-line scanning of a laser beam over a thin layer of metallic powder placed on a dense substrate of the same material is studied. Both the laser beam diameter and the layer thickness are about 50 μm. The typical scanning velocity is in the range of 10–20 cm/s. An effective volumetric heat source is estimated from laser radiation scattering and absorption in a powder layer. A strong difference in thermal conductivity between the powder bed and dense material is taken into account. The above conditions correspond to the technology of selective laser melting that is applied to build objects of complicated shape from metallic powder. Complete remelting of the powder in the scanned zone and its good adhesion to the substrate ensure fabrication of functional parts with mechanical properties close to the ones of the wrought material. Experiments with single-line melting indicate that an interval of scanning velocities exists, where the remelted tracks are uniform. The tracks become “broken” if the scanning velocity is outside this interval. This is extremely undesirable and referred to as the “balling” effect. The size and the shape of the melt pool and the surface of the metallurgical contact of the remelted material to the substrate are analyzed in relation to the scanning velocity. The modeling results are compared with experimental observation of laser tracks. The experimentally found balling effect at scanning velocities above ∼20 cm/s can be explained by the Plateau–Rayleigh capillary instability of the melt pool. Two factors destabilize the process with increasing the scanning velocity: increasing the length-to-width ratio of the melt pool and decreasing the width of its contact with the substrate.

Optimal Process Planning for Laser Forming of Doubly Curved Shapes

2004 ◽  
Vol 126 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Chao Liu ◽  
Y. Lawrence Yao ◽  
Vijay Srinivasan
Keyword(s):  
Process Planning ◽  
Laser Scanning ◽  
Industrial Applications ◽  
Laser Forming ◽  
Field Calculation ◽  
Heating Condition ◽  
Scanning Velocity ◽  
Optimal Approach ◽  
Doubly Curved ◽  
Practical Constraints

There has been a considerable amount of work carried out on two-dimensional laser forming. In order to advance the process further for industrial applications, however, it is necessary to consider more general cases and especially their process planning aspect. This paper presents an optimal approach to laser scanning paths and heating condition determination for laser forming of doubly curved shapes. Important features of the approach include the strain field calculation based on principal curvature formulation and minimal strain optimization, and scanning paths and heating condition (laser power and scanning velocity) determination by combining analytical and practical constraints. The overall methodology is presented first, followed by more detailed descriptions of each step of the approach. Two distinctive types of doubly curved shape, pillow and saddle shapes are focused on and the effectiveness of the proposed approach is validated by forming experiments.

On the Three-Dimensional Laser Bending of Metal Tubes

2012 ◽  
Vol 197 ◽  
pp. 297-301
Author(s):  
Nan Hai Hao ◽  
Yu Ling Gai
Keyword(s):  
Three Dimensional ◽  
Tube Bending ◽  
Laser Bending ◽  
Bending Angle ◽  
Laser Tube ◽  
Systematic Scheme ◽  
Helical Tube ◽  
Plastic Forming ◽  
High Flexibility ◽  
Adjacent Segments

Laser tube bending is a kind of plastic forming method with high flexibility, and is suitable for the low ductility material and thin thickness tube. This paper proposes a systematic scheme for three-dimensional tube bending, which forms the tube by varying the bending position and bending direction continuously. The bending part is simplified as a three-dimensional curve and then the curve is divided into segments and substituted with line sections. The scheme takes the angle between two adjacent segments as the laser bending angle at each bending position and the angle between two adjacent bending plane as the variation of bending direction. The effectiveness of proposed scheme is verified with the forming of a helical tube experimentally. The dimension errors of the formed helical tube are 6.25% in diameter and 7.59% in pitch respectively.

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