State of the art thermal analysis of GaAs/InGaP HBT

2005 ◽  
Author(s):  
P.J. van der Wel ◽  
J.A. Bielen ◽  
T. Henderson ◽  
J. Middleton
Keyword(s):  
Thermal Analysis ◽  
State Of The Art

Weld Microstructure and Hardness Prediction for In-Service Hot-Tap Welds

2004 ◽  
Author(s):  
Wentao Cheng ◽  
Yong-Yi Wang ◽  
William Amend ◽  
Jim Swatzel
Keyword(s):  
Thermal Analysis ◽  
State Of The Art ◽  
High Heat ◽  
Analysis Software ◽  
Prediction Module ◽  
Future Version ◽  
Calculation Algorithms ◽  
Hardness Prediction ◽  
Extensive Experimental Data ◽  
Measured Hardness

Welding onto an in-service pipeline is frequently required to repair damaged areas and for system modifications. There are often significant economic and environmental incentives to perform in-service welding, including the ability to maintain operations during welding and to avoid venting the contents to the atmosphere. Welds made onto in-service pipelines tend to cool at an accelerated rate. These welds are likely to have high heat-affected zone (HAZ) hardness which increases their susceptibility to hydrogen cracking. Accurate prediction of HAZ hardness is critical in developing successful welding procedures for in-service hot-tap welds. The present PRCI thermal analysis software for hot-tap welding uses an empirical-formula-based HAZ hardness prediction procedure. This paper describes an effort funded by PRCI to produce a significantly improved HAZ hardness prediction procedure over the procedure in the current PRCI thermal analysis software. A markedly improved hardness prediction procedure was developed and systematically validated using extensive experimental data of actual welds. The underlying hardness calculation algorithms were based on the proven state-of-the-art phase transformation models. Although on the average the procedure under-predicts the measured hardness by a small amount, the new hardness prediction procedure is a significant improvement in overall accuracy over the procedure in the current PRCI thermal analysis software. The procedure developed here lays the foundation for a much more accurate hardness prediction module in the future version of the PRCI thermal analysis software.

scholarly journals The State-of-the-art of thermal analysis

1980 ◽  
Author(s):  
Oscar Menis ◽  
Harry L Rook ◽  
Paul D Garn
Keyword(s):  
Thermal Analysis ◽  
State Of The Art ◽  
The State

An Updated Cooling Rate and Microstructure Model for Pipeline In-Service Hot-Tap Welds

2006 ◽  
Author(s):  
Yaoshan Chen ◽  
Yong-Yi Wang ◽  
David Horsley
Keyword(s):  
Thermal Analysis ◽  
Cooling Rate ◽  
State Of The Art ◽  
Analysis Software ◽  
Mesh Generator ◽  
New Model ◽  
Accurate Temperature ◽  
Calculation Algorithms ◽  
Finite Element Procedure ◽  
Microstructure Model

This paper describes an improved numerical model for the predictions of cooling rate and heat-affected-zone (HAZ) hardness for welding onto an in-service pipeline. Compared to the current PRCI thermal analysis software, the improvements in this new model include a new mesh generator for the heat transfer finite element procedure and a dynamically-coupled microstructure model that features a state-of-the-art phase transformation and hardness calculation algorithms. The new mesh generator is capable of producing finer mesh than that in the current PRCI thermal analysis software, particularly in the HAZ region so more accurate temperature field can be captured for the hardness calculation. To validate the implementation of these improvements in the model, previous measurements by Battelle and EWI have been collected and compared to the predicted results by the new model. These measurements include cooling times from 800°C to 500°C (t8/5) for both sleeve and branch configurations, and hardness in the HAZ for some of the sleeve configurations.

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