On the relation between fluid dynamic pressure and the formation of pores in laser keyhole welding

1996 ◽  
Vol 8 (4) ◽  
pp. 183-190 ◽  
Author(s):  
John Dowden ◽  
Phiroze Kapadia ◽  
Andy Clucas ◽  
R. Ducharme ◽  
W. M. Steen
Keyword(s):  
Fluid Dynamic ◽  
Dynamic Pressure ◽  
Keyhole Welding ◽  
Laser Keyhole Welding

scholarly journals Study of the effect of inter-pass temperature on weld overlap start-stop defects and mitigation by application of laser defocusing

2021 ◽  
Vol 114 (1-2) ◽  
pp. 117-130
Author(s):  
Wai Jun Lai ◽  
Supriyo Ganguly ◽  
Wojciech Suder
Keyword(s):  
Thermal Cycle ◽  
Laser Initiation ◽  
Thick Section ◽  
Keyhole Welding ◽  
Run Off ◽  
And Control ◽  
Laser Keyhole Welding

AbstractLaser keyhole initiation and termination-related defects, such as cracking and keyhole cavities due to keyhole collapse, are a well-known issue in laser keyhole welding of thick section steels. In longitudinal welding, run-on and run-off plates are used to avoid this problem. However, such an approach is not applicable in circumferential welding where start/stop defects remain within the workpiece. These issues can hinder industry from applying laser keyhole welding for circumferential welding applications. In this paper, the effect of inter-pass temperature on laser keyhole initiation and termination at the weld overlap start-stop region was investigated. This study has identified that defects occurring within this region were due to laser termination rather than laser initiation because of keyhole instabilities regardless of the thermal cycle. The laser termination defects were mitigated by applying a laser defocusing termination regime to reduce the keyhole depth gradually and control the closure of the keyhole.

scholarly journals Accurate Prediction of the Weld Bead Characteristic in Laser Keyhole Welding Based on the Stochastic Kriging Model

Metals ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 486 ◽  
Author(s):  
Xiongfeng Ruan ◽  
Qi Zhou ◽  
Leshi Shu ◽  
Jiexiang Hu ◽  
Longchao Cao
Keyword(s):  
Kriging Model ◽  
Accurate Prediction ◽  
Weld Bead ◽  
Stochastic Kriging ◽  
Keyhole Welding ◽  
Laser Keyhole Welding

Dynamic Stability Analysis of a Flexible Rotor Filled With Liquid Based on Three-Dimensional Flow

2018 ◽  
Vol 141 (5) ◽  
Author(s):  
Guangding Wang ◽  
Huiqun Yuan
Keyword(s):  
Dynamic Stability ◽  
Numerical Technique ◽  
Fluid Dynamic ◽  
Dynamic Pressure ◽  
Three Dimensional ◽  
Frequency Equation ◽  
Fourier Series Expansion ◽  
Flexible Rotor ◽  
Three Dimensional Flow ◽  
Dimensional Flow

This paper deals with the dynamic stability of a flexible liquid-filled rotor. On the basis of three-dimensional flow, the fluid perturbation motion is analyzed and the fluid–structure interaction equation is established, combining with continuity equation, the expression of fluid force exerted on rotor is derived in terms of Fourier series expansion. Considering the complex nonlinear relationship between fluid dynamic pressure and the rotor deformation function, they are expanded in terms of the eigenfunction of a dry rotor. The whirling frequency equation of a flexible rotor partially filled with liquid is obtained based on the rotor static equilibrium equation. Finally, the numerical technique is used to analyze the dynamic stability of the rotor system, and the influences of system parameters on unstable region are discussed.

Investigation of Fluid Flow and Heat Transfer in 3D Dual-Beam Laser Keyhole Welding

2010 ◽  
Author(s):  
Jun Zhou ◽  
Hai-Lung Tsai
Keyword(s):  
Heat Transfer ◽  
Laser Welding ◽  
Welding Process ◽  
Solidification Process ◽  
Melt Flow ◽  
Single Beam ◽  
Keyhole Welding ◽  
Beam Laser ◽  
Dual Beam ◽  
Laser Keyhole Welding

Dual-beam laser welding has become an emerging joining technique. Studies have demonstrated that it can provide benefits over conventional single-beam laser welding, such as increasing keyhole stability, slowing down cooling rate and delaying the humping onset to a higher welding speed. It is also reported to be able to improve weld quality significantly. However, due to its complexity the development of this promising technique has been limited to the trial-and-error procedure. In this study, mathematical models are developed to investigate the heat transfer, melt flow, and solidification process in three-dimensional dual-beam laser keyhole welding. Effects of key parameters, such as laser-beam configuration on melt flow, weld shape, and keyhole dynamics are studied. Some experimentally observed phenomena, such as the changes of the weld pool shape from oval to circle and from circle to oval during the welding process are analyzed in current study.

scholarly journals Effect of Surface Topography Parameters on Friction and Wear of Random Rough Surface

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2762 ◽  
Author(s):  
Ruimin Shi ◽  
Bukang Wang ◽  
Zhiwei Yan ◽  
Zongyan Wang ◽  
Lei Dong
Keyword(s):  
Surface Topography ◽  
Fluid Dynamic ◽  
Dynamic Pressure ◽  
Functional Characterization ◽  
Three Dimensional ◽  
Measuring System ◽  
Height Distribution ◽  
Worn Surface ◽  
The Relationship

In order to explore the relationship between the surface topography parameters and friction properties of a rough contact interface under fluid dynamic pressure lubrication conditions, friction experiments were carried out. The three-dimensional surface topography of specimens was measured and characterized with a profile microscopy measuring system and scanning electron microscope. The friction coefficient showed a trend of decreasing first and then increasing with the increase in some surface topography parameters at lower pressure, such as the surface height arithmetic mean Sa, surface height distribution kurtosis Sku, surface volume average volume Vvv, and surface center area average void volume Vvc, which are the ISO 25178 international standard parameters. The effects of surface topographic parameters on friction were analyzed and the wear mechanism of the worn surface was presented. The wear characteristics of the samples were mainly characterized as strain fatigue, grinding, and scraping. The results provide a theoretical basis for the functional characterization of surface topography.

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