A Crystallographic Model for the Tensile and Fatigue Response for Rene´ N4 at 982°C

1990 ◽  
Vol 57 (1) ◽  
pp. 25-31 ◽  
Author(s):  
M. Y. Sheh ◽  
D. C. Stouffer
Keyword(s):  
Stress State ◽  
Single Crystal ◽  
Back Stress ◽  
Flow Equation ◽  
Stress Effect ◽  
State Variables ◽  
State Variable ◽  
Crystallographic Slip ◽  
Anelastic Behavior ◽  
Nickel Base

An anisotropic constitutive model based on crystallographic slip theory was formulated for nickel-base single crystal superalloys. The current equations include both drag stress and back stress state variables to model the local inelastic flow. Specially designed experiments have been conducted to evaluate the existence of back stress in single crystals. The results showed that the back stress effect of reverse inelastic flow on the unloading stress is orientation dependent, and a back stress state variable in the inelastic flow equation is necessary for predicting anelastic behavior. Model correlations and predictions of experimental data are presented for the single crystal supperalloy Rene´ N4 at 982°C.

Anisotropic Constitutive Modeling of a Single Crystal Superalloy at Elevated Temperature

1990 ◽  
Vol 43 (5S) ◽  
pp. S345-S352 ◽  
Author(s):  
D. C. Stouffer ◽  
M. Y. Sheh ◽  
L. T. Dame
Keyword(s):  
Stress State ◽  
Single Crystal ◽  
Back Stress ◽  
Flow Equation ◽  
Single Crystal Superalloy ◽  
Test Results ◽  
State Variables ◽  
State Variable ◽  
Crystallographic Slip ◽  
Nickel Base

An anisotropic constitutive model based on crystallographic slip theory was formulated for nickel-base single crystal superalloys. The current equations include both drag stress and back stress state variables in the inelastic flow equation for slip in each slip system. Experiments were conducted to evaluate the need of back stress in the model. The test results showed the effect of reverse inelastic flow on unloading is orientation dependent, and that a back stress state variable in the inelastic flow equation is necessary for predicting the anelastic behavior. Model correlations and predictions with experimental data are presented for the single crystal superalloy Rene’ N4 at 760C and 982C.

A Phenomenologically Based Constitutive Model for Rene´ 95

1992 ◽  
Vol 114 (4) ◽  
pp. 340-347 ◽  
Author(s):  
J. A. Sherwood ◽  
D. C. Stouffer
Keyword(s):  
Constitutive Model ◽  
Damage Accumulation ◽  
Evolution Equations ◽  
Internal State ◽  
Cyclic Hardening ◽  
Back Stress ◽  
Flow Equation ◽  
State Variables ◽  
State Variable ◽  
Internal State Variables

A unified constitutive model incorporating internal state variables based upon the deformation phenomena that are observed to occur at the microstructural level has been developed and applied to Rene´ 95. Material hardening is modeled using dragstress and back-stress state variables, while the reduction in the material’s load-carrying capability is described by using a damage-accumulation state variable. Application of the model to the tensile, cyclic, and creep loadings of Rene´ 95 at 650°C demonstrated that the model is capable of capturing cyclic hardening, damage accumulation, and tertiary creep by using one inelastic flow equation in concert with the state-variable-evolution equations.

Constitutive Equations for the Thermomechanical Response of Rene´ 80: Part 1—Development From Isothermal Data

1993 ◽  
Vol 115 (4) ◽  
pp. 351-357 ◽  
Author(s):  
V. S. Bhattachar ◽  
D. C. Stouffer
Keyword(s):  
Constitutive Model ◽  
Arrhenius Equation ◽  
Flow Equation ◽  
Dislocation Climb ◽  
Deformation Mechanisms ◽  
Nickel Base Superalloy ◽  
State Variables ◽  
Material Parameters ◽  
Nickel Base ◽  
Base Superalloy

This work describes the development of a unified nonisothermal constitutive model to predict the thermomechanical fatigue (TMF) response of a Nickel base superalloy, Rene´ 80. Nonisothermal deformation mechanisms are modeled using state variables. The flow equation of the Ramaswamy-Stouffer model was rewritten in the form of an Arrhenius equation with explicit temperature dependence. The isothermal predictions were correlated with the test data at four test temperatures between 538°C and 982°C. Material parameters were verified using nonisothermal tensile calculations. This verification showed that modeling the transition between planar slip and dislocation climb accurately is crucial for obtaining reliable TMF predictions. The revised constitutive model could successfully predict Rene´ 80 response from several TMF tests between 760°C and 982°C.

The Effect of Tensile Stress on Oxidation Behavior of Nickel-Base Single Crystal Superalloy

2021 ◽  
pp. 109737
Author(s):  
Hai-Qing Pei ◽  
Meng Li ◽  
Ping Wang ◽  
Xiao-Hu Yao ◽  
Zhi-Xun Wen ◽  
...  
Keyword(s):  
Tensile Stress ◽  
Single Crystal ◽  
Oxidation Behavior ◽  
Single Crystal Superalloy ◽  
Nickel Base

scholarly journals Exploring the Limits of Floating-Point Resolution for Hardware-In-the-Loop Implemented with FPGAs

Electronics ◽  
2018 ◽  
Vol 7 (10) ◽  
pp. 219 ◽  
Author(s):  
Alberto Sanchez ◽  
Elías Todorovich ◽  
Angel de Castro
Keyword(s):  
The State ◽  
Floating Point ◽  
Hardware In The Loop ◽  
State Variables ◽  
Numerical Resolution ◽  
Digital Devices ◽  
State Variable ◽  
Simulation Step ◽  
Field Programmable ◽  
The Difference

As the performance of digital devices is improving, Hardware-In-the-Loop (HIL) techniques are being increasingly used. HIL systems are frequently implemented using FPGAs (Field Programmable Gate Array) as they allow faster calculations and therefore smaller simulation steps. As the simulation step is reduced, the incremental values for the state variables are reduced proportionally, increasing the difference between the current value of the state variable and its increments. This difference can lead to numerical resolution issues when both magnitudes cannot be stored simultaneously in the state variable. FPGA-based HIL systems generally use 32-bit floating-point due to hardware and timing restrictions but they may suffer from these resolution problems. This paper explores the limits of 32-bit floating-point arithmetics in the context of hardware-in-the-loop systems, and how a larger format can be used to avoid resolution problems. The consequences in terms of hardware resources and running frequency are also explored. Although the conclusions reached in this work can be applied to any digital device, they can be directly used in the field of FPGAs, where the designer can easily use custom floating-point arithmetics.

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