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

scholarly journals Control of Systems of Reservoirs with the Use of Risk Analysis

10.14311/538 ◽  
2004 ◽  
Vol 44 (2) ◽  
Author(s):  
P. Fošumpaur ◽  
L. Satrapa
Keyword(s):  
Risk Analysis ◽  
Flood Control ◽  
Water System ◽  
Water Reservoir ◽  
The Czech Republic ◽  
Run Off ◽  
Hydropower Plants ◽  
Basic Functions ◽  
And Control

A system of reservoirs is usually defined as a system of water management elements, that are mutually linked by inner and outer connections in a purpose-built complex. Combined elements consist of reservoirs, river sections, dams, weirs, hydropower plants, water treatment plants and other hydraulic structures. These elements also include the rainfall system, the run-off system, the ground water system, etc. A system of reservoirs serves many purposes, which result from the basic functions of water reservoirs: storage, flood control and environmental functions. Most reservoirs serve several purposes at the same time. They are so called multi-purposes reservoirs. Optimum design and control of a system of reservoirs depends strongly on identifying the particular purposes. In order to assess these purposes and to evaluate the appropriate set of criteria, risk analysis can be used. Design and control of water reservoir functions is consequently solved with the use of multi-objective optimisation. This paper deals with the use of the risk analysis to determine criteria for controlling the system. This approach is tested on a case study of the Pastviny dam in the Czech Republic.

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.

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
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