Comments on �Similarities and Differences Between Control Systems in Engineering and Biology�: State Variable Approach to the Analysis of Biological Systems

2015 ◽  
pp. 7-13 ◽  
Author(s):  
A. Ann�
Keyword(s):  
Control Systems ◽  
Biological Systems ◽  
State Variable ◽  
Variable Approach ◽  
Similarities And Differences

Constitutive Equations for the Thermomechanical Response of Rene´ 80: Part 2—Effects of Temperature History

1993 ◽  
Vol 115 (4) ◽  
pp. 358-364 ◽  
Author(s):  
V. S. Bhattachar ◽  
D. C. Stouffer
Keyword(s):  
Constitutive Equations ◽  
Temperature History ◽  
Nickel Base Superalloy ◽  
State Variable ◽  
History Effects ◽  
Variable Approach ◽  
Effects Of Temperature ◽  
Nickel Base ◽  
Nonisothermal Conditions ◽  
Base Superalloy

The unified constitutive equations for Rene´ 80 developed by Bhattachar and Stouffer (1992) are used to predict the thermomechanical fatigue (TMF) response of a Nickel base superalloy Rene´ 80 between 649°C and 1093°C. Predictions using these equations suggest that temperature history effects are significant during TMF, and that the TMF response of Rene´ 80 cannot be predicted completely using only isothermal parameters. It is postulated without metallurgical observations that the two deformation mechanisms in Rene´ 80, planar slip at low temperatures and dislocation climb at high temperatures, produce characteristic microstructures which interact under nonisothermal conditions to produce extra hardening that is not present during isothermal deformation. A state variable approach has been used to model this interaction. The nonisothermal model with temperature history effects could successfully predict the initial and saturated TMF response, and block isothermal response of Rene´ 80 from several tests between 649°C and 1093°C.

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