Temperature Gradient Mechanism on Laser Bending of Borosilicate Glass Sheet

2010 ◽  
Vol 132 (1) ◽  
Author(s):  
Dongjiang Wu ◽  
Guangyi Ma ◽  
Fangyong Niu ◽  
Dongming Guo
Keyword(s):  
Temperature Gradient ◽  
Borosilicate Glass ◽  
Fe Simulation ◽  
Glass Sheet ◽  
Laser Forming ◽  
Thickness Direction ◽  
Forming Process ◽  
Primary Defect ◽  
Laser Bending ◽  
Forming Mechanism

The present work is a research on the laser forming process of borosilicate glass sheet. The laser forming mechanism was analyzed, and the temperature gradient mechanism was considered as the main forming mechanism of glass bending. According to the experimental results, a thermomechanical finite element (FE)-simulation was applied for investigating the temperature distribution and thermal stress in the thickness direction of the specimen. Cracks, as the primary defect, were summarized to three kinds: “Y” cracks, straight cracks, and arc cracks, while their forming mechanisms were proposed.

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.

Numerical and experimental analysis on cold-forming and spring-back of hull plate

2018 ◽  
Vol 233 (3) ◽  
pp. 561-569 ◽  
Author(s):  
Wei Shen ◽  
Renjun Yan ◽  
Shuangying Li
Keyword(s):  
Three Dimensional ◽  
Dimensional Accuracy ◽  
Ship Hull ◽  
Laser Forming ◽  
Successive Approximation Method ◽  
Spring Back ◽  
Forming Process ◽  
Cold Forming ◽  
Thick Plates ◽  
Forming Mechanism

Ship hull structures are fabricated by curved thick plates before they are welded together. There are traditional methods such as, line heating and laser-forming methods for plate bending. However, it is recognized that the hot-forming technology causes a series of troubles on doubly or multiple curved plates. Multi-point forming mechanism with square press heads is a new forming process for three-dimensional ship hull plate. Cold-forming has a high dimensional accuracy but results in spring-back. The spring-back process of curved thick plates in the finite element method is analyzed and the predicted results are compared with the test results in the present paper. To ensure the forming precision, the successive approximation method is also developed and verified to control the spring-back.

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

2005 ◽  
Vol 128 (3) ◽  
pp. 634-641 ◽  
Author(s):  
Peng Cheng ◽  
Yajun Fan ◽  
Jie Zhang ◽  
Y. Lawrence Yao ◽  
David P. Mika ◽  
...  
Keyword(s):  
Process Analysis ◽  
Scanning Speed ◽  
Spot Size ◽  
Laser Forming ◽  
Thickness Variation ◽  
Complex Structures ◽  
Forming Process ◽  
Forming Mechanism ◽  
Varying Thickness ◽  
Wide Range

High-intensity laser beams can be used to heat and bend metal plates, but the mechanisms of the laser forming (LF) process are not well understood or precisely controllable. The objective of the National Institute of Standards and Technology sponsored project “Laser Forming of Complex Structures” is to develop technologies for a controllable, repeatable laser forming process that shapes and reshapes a wide range of complex structures such as compressor airfoils that are complex 3D geometries with large thickness variation. In order to apply laser forming to complex 3D geometries, the process analysis and process synthesis (design process parameters such as scanning paths and heating conditions for a desired shape) of LF of varying thickness plate are conducted in this paper. In this study, experimental, numerical, and analytical methods are used to investigate the bending mechanism and parametric effects on the deformation characteristics of varying thickness plates. A transition of the laser forming mechanism was found to occur along the scanning path when the thickness varies. The effect of scanning speed, beam spot size, and multiple scanning on the degree of bending was investigated. The proposed analytical model can predict the bending angle and angle variations for laser forming of varying thickness plate.

A Modified Shell Element Model Combined with Yld91 Yield Function in Simulating Aluminum Alloy Applied Hydroforming

2015 ◽  
Vol 639 ◽  
pp. 435-442 ◽  
Author(s):  
Fei Fei Zhang ◽  
Jun Chen ◽  
Jie Shi Chen ◽  
Xin Hai Zhu ◽  
Shi Jian Yuan
Keyword(s):  
Normal Stress ◽  
Fe Simulation ◽  
Applied Pressure ◽  
Shell Element ◽  
Material Model ◽  
Element Model ◽  
Yield Function ◽  
Element Formulation ◽  
Thickness Direction ◽  
Forming Process

Hydroforming has been used widely across many industrial fields. Large applied pressure during hydroforming makes it necessary to consider the influence of normal stress in the thickness direction, while in FE simulation, the use of traditional shell element based upon plane-stress assumption is not appropriate in such cases. Here, the traditional shell element is modified by changing the constitutive relation which took into account the normal stress in the thickness direction, and the modified shell element formula is combined with Yld91 yield function to simulate the forming process of Aluminium alloy. Then the element formulation and material model is implemented into the FE code Ls-Dyna by means of USER interface. Two examples are carried out and good correlations are obtained when compared to the traditional shell element and solid element.

Bending Mechanism Analysis for Laser Forming of Metal Foam

2017 ◽  
Author(s):  
Tizian Bucher ◽  
Adelaide Young ◽  
Min Zhang ◽  
Chang Jun Chen ◽  
Y. Lawrence Yao
Keyword(s):  
Temperature Gradient ◽  
Sheet Metal ◽  
Metal Foam ◽  
Numerical Models ◽  
Image Correlation ◽  
Laser Forming ◽  
Mechanism Analysis ◽  
Forming Process ◽  
Experimental Proof ◽  
Post Process

To date, the industrial production of metal foam components has remained challenging, since few methods exist to manufacture metal foam into the shapes required in engineering applications. Laser forming is currently the only method with a high geometrical flexibility that is able to shape arbitrarily sized parts. What prevents the industrial implementation of the method, however, is that no detailed experimental analysis has been done of the metal foam strain response during laser forming, and hence the existing numerical models have been insufficiently validated. Moreover, current understanding of the laser forming process is poor, and it has been assumed, without experimental proof, that the temperature gradient mechanism (TGM) from sheet metal forming is the governing mechanism for metal foam. In this study, these issues were addressed by using digital image correlation (DIC) to obtain in-process and post-process strain data that was then used to validate a numerical model. Additionally, metal foam laser forming was compared with metal foam 4-point bending and sheet metal laser forming to explain why metal foam can be bent despite its high bending stiffness, and to evaluate whether TGM is valid for metal foam. The strain measurements revealed that tensile stretching is only a small contributor to foam bending, with the major contributor being compression-induced shortening. Unlike in sheet metal laser forming, this shortening is achieved through cell wall bending, as opposed to plastic compressive strains. Based on this important difference with traditional TGM, a modified temperature gradient mechanism (MTGM) was proposed.

Temperature Gradient-Based Laser Bending of Full Plates and Plates With Cutout

2020 ◽  
pp. 270-305
Author(s):  
Paramasivan Kalvettukaran ◽  
Sandip Das ◽  
Sundar Marimuthu ◽  
Dipten Misra
Keyword(s):  
Laser Forming ◽  
Forming Process ◽  
Laser Bending ◽  
Bending Angle ◽  
Aisi 304 ◽  
Thermally Induced ◽  
Bending Process ◽  
Gradient Based ◽  
Different Dimensions ◽  
Different Shapes

The laser bending process, also called the laser forming process, consists of irradiating the surface of a sheet or a plate by means of a moving laser beam with a predefined scanning strategy to generate the desired shape through thermally induced residual stress. This chapter presents the mechanisms of a laser bending process and the technological aspects concerning laser v-bending of rectangular AISI 304 plates for full plates and plates with a central cutout at its middle to highlight the process fundamentals and how processing affects the final bending angle of the workpieces. Laser bending involving plates with a cutout will have numerous applications for car bodies, such as front and rear panels where bending is required to be performed on panels with cutout geometries. To investigate the effects of shape and size of the cutout on temperature distribution, stress distribution, and final bending angle, different shapes such as circular, ellipse, rectangular, and square, as well as different dimensions of cutouts have been chosen.

scholarly journals Recent Advances in the Laser Forming Process: A Review

Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1472
Author(s):  
Mehdi Safari ◽  
Ricardo Alves de Sousa ◽  
Jalal Joudaki
Keyword(s):  
Process Parameters ◽  
Optimization Technique ◽  
Laser Forming ◽  
Forming Process ◽  
Laser Bending ◽  
Heating Source ◽  
Fiber Metal ◽  
Local Softening ◽  
Doubly Curved ◽  
And Control

Laser forming is an emerging manufacturing process capable of producing either uncomplicated and complicated shapes by employing a concentrated heating source. The heat source movement creates local softening, and a plastic strain will be induced during the rise of temperature and the subsequent cooling. This contactless forming process may be used for the simple bending of sheets and tubes or fabrication of doubly-curved parts. Different studies have been carried out over recent years to understand the mechanism of forming and predicting the bending angle. The analysis of process parameters and search for optimized manufacturing conditions are among the most discussed topics. This review describes the main recent findings in the laser forming of single and multilayer sheets, composite and fiber-metal laminate plates, force assisted laser bending, tube bending by laser beam, the optimization technique implemented for process parameters selection and control, doubly-curved parts, and the analytical solutions in laser bending. The main focus is set to the researches published since 2015.

Bending Angle Estimated Based on Inherent Strain Theory during Laser Forming

2010 ◽  
Vol 663-665 ◽  
pp. 947-951
Author(s):  
Jing Zhou ◽  
Hong Shen
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Strain Theory ◽  
Laser Forming ◽  
Elastic Analysis ◽  
Forming Process ◽  
Bending Angle ◽  
Forming Mechanism ◽  
Inherent Strain ◽  
Element Method

Laser forming process analyzed under thermo-elasto-plastic finite element method can better understand the forming mechanism. However, it is very time consuming. This paper introduced the prediction of the deformation in laser forming based on the theory of inherent strain by finite element method (FEM). The relations between inherent strains and laser forming parameters based on some experimental curves and the thermo-elasto-plastic analysis can be determined, in which the inherent strains are assumed to be distributed in a rectangle shape. This method is much more convenient because only elastic analysis is involved. The effectiveness of the proposed method is demonstrated through the comparison with the experimental data.

Experimental and Numerical Analysis of Low Output Power Laser Bending of Thin Steel Sheets

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Vicente Stevens ◽  
Diego Celentano ◽  
Jorge Ramos-Grez ◽  
Magdalena Walczak
Keyword(s):  
Numerical Analysis ◽  
Output Power ◽  
Laser Forming ◽  
Element Formulation ◽  
Temperature Dependent ◽  
Forming Process ◽  
Laser Bending ◽  
Operating Variables ◽  
Steel Sheets ◽  
Thermal Boundary Conditions

This work presents an experimental and numerical analysis of a low output power single-pass laser forming process applied to thin stainless steel sheets. To this end, the proposed methodology consists in four stages respectively devoted to material characterization via tensile testing, estimation of thermal boundary conditions present in laser forming, realization of laser bending tests for two sets of operating variables, and finally, numerical simulation of this process carried out with a coupled thermomechanical finite element formulation accounting for large plastic strains, temperature-dependent material properties and convection–radiation phenomena. The numerical analysis, focused on the description of the evolution of the thermomechanical material response, is found to provide a satisfactory experimental validation of the final bending angle for two laser forming cases with different operating variables. In both cases, the predicted high temperature gradients occurring across the sample thickness show that the deformation process is mainly governed by the thermal gradient mechanism.

FE Simulation of Complex Contour Forming of Sheet Metals Based on Laser Bending

2008 ◽  
Vol 575-578 ◽  
pp. 696-701
Author(s):  
Yi Bin Chen ◽  
Jian Zhong Zhou ◽  
Shu Huang ◽  
Yue Qing Sun
Keyword(s):  
Numerical Simulation ◽  
Fe Simulation ◽  
Three Dimensional ◽  
External Heat ◽  
Forming Process ◽  
Laser Bending ◽  
Complex Contour ◽  
Analysis Technique ◽  
Flexible Forming Process ◽  
External Forces

Laser bending is a flexible forming process which forms sheet metal by means of stresses induced by external heat instead of external forces. In this paper, a three-dimensional coupled thermal-mechanical model for numerical simulation is established with finite element code ABAQUS. Some key problems about the simulation of laser bending are investigated in detail, and the reasonable solutions are presented. Taking AISI-1008 steel as an example, numerical simulations are carried out for the complex contour forming of sheet by using Sequentially Coupled Thermal-Stress Analysis technique. Then the corresponding experiments are performed to validate the simulation results. Good correlation between the numerical simulation and the experimental results was demonstrated.

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