Thermal Defocussing Criteria for a Laser Welding Process

2004 ◽  
Author(s):  
Gregory J. Kowalski ◽  
Richard A. Whalen
Keyword(s):  
Laser Beam ◽  
Laser Welding ◽  
Phase Change ◽  
Heat Affected Zone ◽  
Solid Phase ◽  
Welding Process ◽  
Index Of Refraction ◽  
Simulation Code ◽  
Collimated Beam ◽  
Laser Welding Process

A numerical simulation code is developed to study the significance of refraction effects (beam self-focussing or defocussing) of a laser during a laser welding process. Relationships between the size of the heat affected zone (HAZ), the melt zone and the laser beam parameters are investigated for a short pulsed laser welding process. The solution method includes the thermally stimulated nonlinear optical effects caused by the temperature dependent index of refraction, as well as the step change in surface reflection that occurs due to the liquid and solid phase change. The interaction of these parameters is investigated to better control the laser manufacturing processes. Difficulties of numerical modeling and the tradeoff between using small nodes to reduce the sawtooth behavior in the phase change model and computer run times that are consistent with real time control are discussed. The results indicate that there are no significant refraction affects of the laser beam and that the heat affected zone is approximately 6% larger for a collimated beam input as compared to a gaussian beam input. Peak temperatures are lower for the collimated beam.

Intense X-Ray Measurement of Transient Hydraulic Phenomena in Molten Pool During Laser Welding Process

2012 ◽  
Author(s):  
Tomonori Yamada ◽  
Takahisa Shobu ◽  
Susumu Yamashita ◽  
Takemitsu Ogawa ◽  
Kenta Sugihara ◽  
...  
Keyword(s):  
Temperature Distribution ◽  
Laser Welding ◽  
Phase Change ◽  
Molten Pool ◽  
Welding Process ◽  
In Situ Observation ◽  
Interface Shape ◽  
X Ray ◽  
Laser Welding Process

Spatial temperature distribution during the laser welding process has a huge effect on any residual stress distribution. Therefore, understanding of the transient hydraulic phenomena which affect the temperature distribution in the molten pool is very important. In this work, intense X-ray measurement at the Super Photon ring-8 GeV (SPring-8) facility well carried out to document the transient hydraulic phenomena in the molten pool during the laser welding process. Based on in-situ observation of inside material, the experimental results confirmed that the molten pool shapes, hydraulic condition such as flow velocity, etc.. In the case of laser power is 330W and spot diameter is 1mm, we observed the steady flow which consisted of downward flow and upward flow. The flow velocities were about 19.5 mm/s and 9.0 mm/s, respectively. Moreover, the rate of phase change was obtained from molten pool shape during laser welding. The rate of phase change was not constant during laser welding. Thus the interface shape might change at all time. Therefore, to evaluate the temperature distribution, it is necessary to consider not only convection but also the interface shape. These results indicate that the intense X-ray measurement during laser welding is very effective for the understanding the molten pool phenomena.

Study of heat-affected zone and mechanical properties of Nd-YAG laser welding process of thin titanium alloy sheet

2016 ◽  
Vol 1 (2) ◽  
pp. 51-58 ◽  
Author(s):  
Grzegorz Krolczyk ◽  
Aleksandar Sedmak ◽  
Uday Kumar ◽  
Somnath Chattopadhyaya ◽  
A. K. Das ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Titanium Alloy ◽  
Laser Welding ◽  
Heat Affected Zone ◽  
Welding Process ◽  
Alloy Sheet ◽  
Yag Laser ◽  
Laser Welding Process

Numerical Modeling of Thermoplastic Films in a Laser Welding Process

2005 ◽  
Author(s):  
Richard A. Whalen ◽  
Gregory J. Kowalski
Keyword(s):  
Laser Welding ◽  
Welding Process ◽  
Surface Cooling ◽  
Simulation Code ◽  
Transmission Laser Welding ◽  
Lap Welding ◽  
The Relationship ◽  
Thermo Physical Properties ◽  
Laser Welding Process ◽  
Moving Layers

A numerical simulation code is used to investigate the size of the heat affected zone (HAZ) and the onset of thermal damage in a short pulsed transmission laser welding process. The welding process involves the lap welding of two thin 30 microns thick, moving layers, of thermoplastic films. The investigated welding conditions are transparent material over a semi-transparent or opaque material and two transparent materials over a reflective backing. The results provide temperature profiles that illustrate the relationship between; surface cooling, laser intensity, velocity feed rates and material thermo-physical properties.

Numerical Simulation of Thermoplastics in a Short Pulsed Laser Welding Process

2006 ◽  
Author(s):  
Richard A. Whalen ◽  
Gregory J. Kowalski
Keyword(s):  
Numerical Simulation ◽  
Laser Welding ◽  
Laser Intensity ◽  
Welding Process ◽  
Thin Layers ◽  
Simulation Code ◽  
Transmission Laser Welding ◽  
Lap Welding ◽  
Thermo Physical Properties ◽  
Laser Welding Process

A numerical simulation code is developed and used to investigate the differences in thermal behavior and the size of the heat affected zone (HAZ) in a short pulsed transmission laser welding process (>0.5 ps (1/e2)). The numerical model uses both a Fourier and Hyperbolic thermal model. The welding process involves the lap welding of two thin layers of thermoplastic films. The investigated welding conditions are transparent material over a semi-transparent or opaque material. The results provide temperature profiles that illustrate the differences between the predicted temperatures of the two thermal models as well as the effects of laser intensity and material thermo-physical properties.

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