The Influence of Sheet Metal Anisotropy on Laser Forming Process

2004 ◽  
Vol 127 (3) ◽  
pp. 572-582 ◽  
Author(s):  
Peng Cheng ◽  
Y. Lawrence Yao
Keyword(s):  
Sheet Metal ◽  
Electron Backscatter Diffraction ◽  
Plastic Anisotropy ◽  
Development Theory ◽  
Laser Forming ◽  
Uniaxial Tensile ◽  
Rolled Sheet ◽  
Forming Process ◽  
Anisotropy Index ◽  
Cold Rolled

Cold-rolled sheet metal that is often used in laser forming exhibits anisotropic properties, which are mostly caused by preferred orientations of grains developed during the severe plastic deformation such as cold rolling. In the present study, the textures of cold-rolled mild steel sheets are characterized and the influence of the plastic anisotropy on laser forming process is investigated. Deformation textures are measured in terms of pole figures and orientation distribution function (ODF) plots obtained through electron backscatter diffraction (EBSD). The anisotropy index (R-value) of the material with different rolling reductions is obtained by uniaxial tensile tests. Both are compared and agree with the texture development theory. Effects of the plastic anisotropy on bending deformation during the laser forming process are investigated experimentally and numerically. Various conditions including different laser power, scanning speed, and number of scans for sheets of different rolling reductions are considered and results are discussed. The simulation results are consistent with the experimental observations.

Estimation of Residual Stress in Cold Rolled Iron-Disks Using Magnetic and Ultrasonic Methods and Neutron Diffraction Technique

1994 ◽  
Vol 376 ◽  
Author(s):  
V.L. Aksenov ◽  
A.M. Balagurov ◽  
G.D Bokuchava ◽  
J. Schreiber ◽  
Yu.V. Taran Frank
Keyword(s):  
Residual Stress ◽  
Neutron Diffraction ◽  
Sheet Metal ◽  
Diffraction Method ◽  
Calibration Procedure ◽  
Rolled Sheet ◽  
Forming Process ◽  
Practical Applications ◽  
Ultrasonic Methods ◽  
Cold Rolled

ABSTRACTVariation of internal stress states in cold rolled sheet metal can essentially influence the result of forming processes. Therefore it is important to control the forming process by a practicable in line testing method. For this purpose magnetic and ultrasonic nondestructive methods are available. However, it is necessary to calibrate these techniques. This paper describes a first step of such a calibration procedure making use of the neutron diffraction method. On the basis of the diffraction results an assessment of the magnetic and ultrasonic methods for the estimation of residual stress in the cold rolled iron-disks was made. Reasonable measuring concepts for practical applications to forming processes with cold rolled sheet metal are discussed.

Forming Limit Diagram of the AMS 5599 Sheet Metal

2013 ◽  
Vol 58 (4) ◽  
pp. 1213-1217
Author(s):  
W. Fracz ◽  
F. Stachowicz ◽  
T. Trzepieciński ◽  
T. Pieją
Keyword(s):  
Mechanical Properties ◽  
Sheet Metal ◽  
Plastic Anisotropy ◽  
Experimental Studies ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Uniaxial Tensile ◽  
Strain Hardening Exponent ◽  
Uniaxial Tensile Test ◽  
Anisotropy Ratio

Abstract Formability of sheet metal is dependent on the mechanical properties. Some materials form better than others - moreover, a material that has the best formability for one stamping may behave very poorly in a stamping of another configuration. For these reasons, extensive test programs are often carried out in an attempt to correlate material formability with value of some mechanical properties. The formability of sheet metal has frequently been expressed by the value of strain hardening exponent and plastic anisotropy ratio. The stress-strain and hardening behaviour of a material is very important in determining its resistance to plastic instability. However experimental studies of formability of various materials have revealed basic differences in behaviour, such as the ”brass-type” and the ”steel-type”, exhibiting respectively, zero and positive dependence of forming limit on the strain ratio. In this study mechanical properties and the Forming Limit Diagram of the AMS 5599 sheet metal were determined using uniaxial tensile test and Marciniak’s flat bottomed punch test respectively. Different methods were used for the FLD calculation - results of these calculations were compared with experimental results

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.

Characterizations on Microscale Laser Dynamic Forming of Metal Foil

2006 ◽  
Author(s):  
Gary J. Cheng ◽  
Daniel Pirzada
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Electron Backscatter Diffraction ◽  
Laser Forming ◽  
Metal Foil ◽  
Laser Shock ◽  
Forming Process ◽  
High Shock ◽  
Shock Peening

Laser dynamic forming (LDF) is a unique hybrid forming process, combining the advantages of laser shock peening, laser forming and metal forming, with an ultra high strain rate forming utilizing laser shock waves. In this paper, a hybrid forming technique based on laser dynamic forming will be demonstrated. The feasibility of laser dynamic forming will be discussed through experiments. The mechanical and microstructure of the formed 3D structures will be characterized. The grain microstructure and misorientation will be investigated quantitatively with Electron backscatter diffraction (EBSD). The residual stress distributions are measured using X-ray diffraction. We will describe the important factors that lead to improved micro-formability at high strain rate induced by high shock pressure. It is concluded that with further development, this may be an important microforming technology for various materials. LDF has great potential for meso-, micro- and nano scale forming since the laser provides high precision, highly-localized heating intensity, high repeatability, fast setup and superb flexibility.

Directionality of Fatigue Properties in Some Textured Sheet Metals

1970 ◽  
Vol 92 (1) ◽  
pp. 115-120 ◽  
Author(s):  
I. Le May ◽  
K. D. Nair
Keyword(s):  
Cold Rolling ◽  
Sheet Metal ◽  
Fatigue Properties ◽  
Rolled Sheet ◽  
Sheet Metals ◽  
Rolled Material ◽  
Pole Figures ◽  
Cold Rolling And Annealing ◽  
Cold Rolled

The fatigue properties of some face-centred cubic sheet metals with cold rolling and annealing textures are reported. The observed differences between fatigue properties measured in the transverse and longitudinal directions in cold-rolled material are discussed and are related to the pole figures for the material. The study emphasizes that considerable directionality of fatigue properties can occur in rolled sheet metal.

Fatigue Life Prediction After Laser Forming

2005 ◽  
Vol 127 (1) ◽  
pp. 157-164 ◽  
Author(s):  
J. Zhang ◽  
D. Pirzada ◽  
C. C. Chu ◽  
G. J. Cheng
Keyword(s):  
Fatigue Life ◽  
Sheet Metal ◽  
Low Carbon Steel ◽  
Laser Forming ◽  
Primary Concern ◽  
Low Carbon ◽  
Forming Process ◽  
Proposed Model ◽  
Life Model ◽  
Residual Stresses And Strains

Analysis of the laser forming process has been focused on geometry, yield strength, and microstructure change in the past. However fatigue life has been the primary concern for engineering components in many applications. For laser forming to become a practical rapid prototyping tool, research has to be done to predict fatigue life of sheet metal after laser forming. Microstructure as well as the distribution of residual stresses and strains changes during laser forming process. The current models cannot predict the fatigue life after laser forming accurately because of differences in assumptions. This work presents a model to predict fatigue life of sheet metal after laser forming. Results from microstructure integrated finite element modeling of laser forming are incorporated in the fatigue life model. Low carbon steel is used in this work to validate the model. It is shown that the proposed model can predict the fatigue life of sheet metal after laser forming with good accuracy. The predictions from the model are consistent with experimental results. Effects of laser forming conditions on fatigue life of sheet metal are under investigation.

Comparison of Predicted Forming Limit Curves with Measured Experimental Data on Hot-Dip Zinc-Coated Cold-Rolled Steel by Incremental Forming Process

2019 ◽  
Vol 821 ◽  
pp. 256-262 ◽  
Author(s):  
Ramil Kesvarakul ◽  
Khompee Limpadapun
Keyword(s):  
Experimental Data ◽  
Incremental Forming ◽  
True Strain ◽  
Single Point ◽  
Forming Limit ◽  
Rolled Sheet ◽  
Single Point Incremental Forming ◽  
Forming Process ◽  
Cold Rolled ◽  
Forming Limit Curves

Single Point Incremental Forming (SPIF) is a die-less forming process with advantages of high-flexibility, low-cost and short lead time. The high local strains that are applied to the metal sheet, often exceeding the conventional formability limit. This paper is focused on comparison of predicted forming limit curves with measured experimental data on Hot-Dip Zinc-Coated Cold-Rolled sheet, with 0.20 mm thick is studied in single point incremental forming. Truncated square pyramid and cone are formed to study the formability of blank sheets at room temperature. It was found that both Formulation of plastic instability criteria and Keeler’s formula gives the lowest FLC. FLDs have predicted failures in forming process consistently with the real experiments. The experimentally obtained cracking limit differ from analytical one and empirical one by about 3.398 and 2.135 true strain respectively at FLD0, the corresponding plane strain values.

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