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.

Study of Edge Effects in Laser Bending

1999 ◽  
Author(s):  
Jiangcheng Bao ◽  
Y. Lawrence Yao
Keyword(s):  
Edge Effects ◽  
Material Properties ◽  
Laser Forming ◽  
Temperature Dependency ◽  
Rate Dependency ◽  
Laser Bending ◽  
Angle Variation ◽  
Bending Angle ◽  
Numerical Studies ◽  
Strain Rate Dependency

Abstract Laser forming has not been widely used due to limited understanding of its mechanism and immaturity of processing technology. In the study of single axis laser bending of plates, edge effects affect accuracy of the bending. Experimental and numerical studies are carried out to study the mechanism of the edge effects. Temperature dependency of material properties and strain-rate dependency of yield stress are considered in numerical simulation. Numerical results match well with experimental results. Patterns of edge effects are examined in terms of bending angle variation and curved bending edge under different conditions. A more complete explanation for the mechanism of the edge effects is given.

Analysis of Residual Stresses in Pipe Seam Welds and a Proposed Residual Stress Profile Estimation Method

2015 ◽  
Author(s):  
Shaopin Song ◽  
Pingsha Dong
Keyword(s):  
Residual Stress ◽  
Wall Thickness ◽  
Functional Form ◽  
Estimation Method ◽  
Thickness Ratio ◽  
Stress Profile ◽  
Stress Distributions ◽  
Residual Stress Profile ◽  
Wide Range ◽  
Profile Estimation

A recent comprehensive investigation into residual stress distributions in pipe and vessel longitudinal seam welds is presented in this paper, covering component wall thickness from 1/4” (6.35mm) to 10” (254mm), component radius to wall thickness ratio from 2 to 10, and linear welding heating input from low (50 J/mm) to high (6000 J/mm). Through the use of a residual stress decomposition technique, two key parameters that govern through-thickness residual stress distributions in terms of their membrane and bending content have been identified. One is component radius to wall thickness ratio (r/t) and the other is a characteristic heat input density (Q̂) having a unit of J/mm3. With these two parameters, a unified functional form for representing through-thickness residual stress profile behaviors in seam welds is proposed along with its solution procedure for applications in weld region. The simplicity of the proposed residual stress profile estimation scheme in functional form and demonstrated applicability for a wide range of r/t and Q̂ provides an effective framework for generating residual stress profile information for supporting defect assessment procedures in FFS codes and standards.

Heat Affected Zone Induced by Laser Forming

Volume 1 ◽  
2004 ◽  
Author(s):  
L. Casamichele ◽  
A. Gisario ◽  
V. Tagliaferri
Keyword(s):  
Mechanical Properties ◽  
Heat Affected Zone ◽  
Laser Scanning ◽  
Standard Condition ◽  
Laser Forming ◽  
Hole Drilling ◽  
Flexible Tool ◽  
Indentation Tests ◽  
Testing Complex ◽  
Scanning Path

Laser forming induces mechanical and structural modifications around the Laser Scanning Path. Various conventional methods are currently available to estimate properties of materials like X-ray and neutron diffraction, strain/curvature measurement, hole drilling, layer removal, chemical etching, etc. but their use is severely restricted due to measurement accuracy, applicability to different materials and geometrical configurations. An application of an experimental method to estimate mechanical properties associated with laser forming of metallic sheets is proposed. This method is based on an instrumented indentation technique which offers a more flexible tool to measure mechanical properties of Heat Affected Zone. The main advantage of this technique consists of testing complex geometric forms with a cheap system able to be used for on-line implementation. The experimental validation of the method was performed calibrating the procedure by using several indentation tests in standard condition. A full map of mechanical properties was subsequently traced employing systematic investigations focused on specimens zone closer to the laser heated scanning path.

Controlling Edge Effects in Laser Bending

2012 ◽  
Vol 271-272 ◽  
pp. 1521-1525
Author(s):  
Hong Shen ◽  
Jun Hu
Keyword(s):  
Plastic Strain ◽  
Sheet Metal ◽  
Edge Effects ◽  
Time History ◽  
Laser Forming ◽  
Spring Back ◽  
Laser Bending ◽  
Mechanical Process ◽  
New Strategy ◽  
Strain Dependent

Laser forming of sheet metal offers the advantages of requiring no hard tooling, no spring back and no external force. Thus this technology reduces cost, increases flexibility and accuracy. Laser forming is a complicated and transient thermo-mechanical process involving elastic and plastic strain dependent on time history. How to control and enhance the accuracy of the laser forming attracts much attention. This paper put forward a new strategy to control and reduce the edge effects in laser forming. Numerical simulations and experiments were also carried out to validate the presented strategy.

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.

Residual Stress in Coatings Produced by Cold Spray

2013 ◽  
Vol 772 ◽  
pp. 155-159 ◽  
Author(s):  
Vladimir Luzin ◽  
Kevin Spencer ◽  
Ming Xing Zhang ◽  
Neil Matthews
Keyword(s):  
Residual Stress ◽  
Cold Spray ◽  
Deposition Process ◽  
Stress Distributions ◽  
Coating Materials ◽  
Metal Coatings ◽  
Surface Corrosion ◽  
Wide Range ◽  
History Of ◽  
And Performance

Cold spray technology is used to produce metal coatings with a variety of functions, including surface corrosion protection, improvement of wear resistance, etc. Cold sprayed materials exhibit a wide range of behaviours resulting in large variation of spraying efficiency, coating properties, quality and performance in service. Residual stress, being a result and attribute of the deposition process, can be studied to test whether the coating is in tension/compression stress state and also to provide information about the thermo-mechanical history of the material during the deposition process. Residual stress distributions in a variety of coating materials have been studied by neutron diffraction. Through-thickness residual stress profiles show that the stress magnitude varies significantly and depends mainly on the mechanical properties of the coating material.

scholarly journals One-step preparation of antimicrobial silicone materials based on PDMS and salicylic acid: insights from spatially and temporally resolved techniques

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Luca Barbieri ◽  
Ioritz Sorzabal Bellido ◽  
Alison J. Beckett ◽  
Ian A. Prior ◽  
Jo Fothergill ◽  
...  
Keyword(s):  
Salicylic Acid ◽  
Laser Scanning ◽  
Pathogenic Bacteria ◽  
Pharmaceutical Products ◽  
Laser Scanning Microscopy ◽  
Wound Dressings ◽  
Confocal Laser ◽  
Vis Spectroscopy ◽  
Wide Range ◽  
One Step

AbstractIn this work, we introduce a one-step strategy that is suitable for continuous flow manufacturing of antimicrobial PDMS materials. The process is based on the intrinsic capacity of PDMS to react to certain organic solvents, which enables the incorporation of antimicrobial actives such as salicylic acid (SA), which has been approved for use in humans within pharmaceutical products. By combining different spectroscopic and imaging techniques, we show that the surface properties of PDMS remain unaffected while high doses of the SA are loaded inside the PDMS matrix. The SA can be subsequently released under physiological conditions, delivering a strong antibacterial activity. Furthermore, encapsulation of SA inside the PDMS matrix ensured a diffusion-controlled release that was tracked by spatially resolved Raman spectroscopy, Attenuated Total Reflectance IR (ATR-IR), and UV-Vis spectroscopy. The biological activity of the new material was evaluated directly at the surface and in the planktonic state against model pathogenic bacteria, combining confocal laser scanning microscopy, electron microscopy, and cell viability assays. The results showed complete planktonic inhibition for clinically relevant strains of Staphylococcus aureus and Escherichia coli, and a reduction of up to 4 orders of magnitude for viable sessile cells, demonstrating the efficacy of these surfaces in preventing the initial stages of biofilm formation. Our approach adds a new option to existing strategies for the antimicrobial functionalisation of a wide range of products such as catheters, wound dressings and in-dwelling medical devices based on PDMS.

scholarly journals Quantifying Understory Complexity in Unmanaged Forests Using TLS and Identifying Some of Its Major Drivers

2021 ◽  
Vol 13 (8) ◽  
pp. 1513
Author(s):  
Dominik Seidel ◽  
Peter Annighöfer ◽  
Christian Ammer ◽  
Martin Ehbrecht ◽  
Katharina Willim ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Structural Equation Models ◽  
Light Availability ◽  
Structural Complexity ◽  
Basal Area ◽  
Ecosystem Functions ◽  
Canopy Openness ◽  
Seasonal Precipitation ◽  
Wide Range ◽  
Precipitation And Temperature

The structural complexity of the understory layer of forests or shrub layer vegetation in open shrublands affects many ecosystem functions and services provided by these ecosystems. We investigated how the basal area of the overstory layer, annual and seasonal precipitation, annual mean temperature, as well as light availability affect the structural complexity of the understory layer along a gradient from closed forests to open shrubland with only scattered trees. Using terrestrial laser scanning data and the understory complexity index (UCI), we measured the structural complexity of sites across a wide range of precipitation and temperature, also covering a gradient in light availability and basal area. We found significant relationships between the UCI and tree basal area as well as canopy openness. Structural equation models (SEMs) confirmed significant direct effects of seasonal precipitation on the UCI without mediation through basal area or canopy openness. However, annual precipitation and temperature effects on the UCI are mediated through canopy openness and basal area, respectively. Understory complexity is, despite clear dependencies on the available light and overall stand density, significantly and directly driven by climatic parameters, particularly the amount of precipitation during the driest month.

Microstructure, Hardness, and Residual Stress Distributions in T-Joint Weld of HSLA S500MC Steel

2017 ◽  
Vol 48 (3) ◽  
pp. 1103-1110 ◽  
Author(s):  
Intissar Frih ◽  
Guillaume Montay ◽  
Pierre-Antoine Adragna
Keyword(s):  
Residual Stress ◽  
Stress Distributions
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