A Unified Constitutive Model for the Inelastic Uniaxial Response of Rene’ 80 at Temperatures Between 538C and 982C

1990 ◽  
Vol 112 (3) ◽  
pp. 280-286 ◽  
Author(s):  
V. G. Ramaswamy ◽  
D. C. Stouffer ◽  
J. H. Laflen
Keyword(s):  
Experimental Data ◽  
High Temperature ◽  
Constitutive Equation ◽  
Constitutive Model ◽  
Mean Stress ◽  
Torsional Loading ◽  
Creep Response ◽  
Cyclic Response ◽  
Mechanical Cycling ◽  
Starting Point

The objective of this research is to develop a constitutive equation for the uniaxial monotonic and cyclic response of Rene’80 between the temperatures of 538C and 982C. The constitutive equation is accompanied by experimental data for the evaluation of the material constants. Extensive verification is achieved through the successful correlation of tensile and creep response and prediction of mechanical cycling experiments including mean stress shifts. These results also serve as a starting point for reformulating the model for the prediction of the high temperature multiaxial response of Rene’80 that includes torsion, proportional, and nonproportional uniaxial and torsional loading histories.

Study on Damage Constitutive Model of Cemented Tailings Backfill under Uniaxial Compression

2013 ◽  
Vol 353-356 ◽  
pp. 379-383 ◽  
Author(s):  
Gen Bo Yu ◽  
Peng Yang ◽  
Ying Zhou Chen
Keyword(s):  
Experimental Data ◽  
Constitutive Equation ◽  
Constitutive Model ◽  
Evolution Equation ◽  
Uniaxial Compression ◽  
Damage Evolution ◽  
Damage Evolution Equation ◽  
Damage Constitutive Model

Under the premise of isotropic and continuum cemented tailings and damage proportional to the external doing work, the damage evolution equation and damage evolution constitutive equation were derived by using the strain equivalent principle. Under the consideration of the damage also transferring stress when uniaxial compression, the damage corrected parameter was introduced to obtain the damage evolution constitutive equation containing corrected parameter. Based on the experimental data from the uniaxial compression of cemented tailing, this article validates the theoretical curves consist with the experimental ones under certain damage corrected parameter.

scholarly journals Optimising the multiplicative AF model parameters for AA7075 cyclic plasticity and fatigue simulation

2018 ◽  
Vol 90 (2) ◽  
pp. 251-260 ◽  
Author(s):  
Dylan Agius ◽  
Mladenko Kajtaz ◽  
Kyriakos I. Kourousis ◽  
Chris Wallbrink ◽  
Weiping Hu
Keyword(s):  
Experimental Data ◽  
Stress Relaxation ◽  
Cyclic Plasticity ◽  
Model Parameters ◽  
Mean Stress ◽  
Multiobjective Optimisation ◽  
Simulation Accuracy ◽  
Content Type ◽  
Starting Point ◽  
Mean Stress Relaxation

Purpose This study presents the improvements of the multicomponent Armstrong–Frederick model with multiplier (MAFM) performance through a numerical optimisation methodology available in a commercial software. Moreover, this study explores the application of a multiobjective optimisation technique for the determination of the parameters of the constitutive models using uniaxial experimental data gathered from aluminium alloy 7075-T6 specimens. This approach aims to improve the overall accuracy of stress–strain response, for not only symmetric strain-controlled loading but also asymmetrically strain- and stress-controlled loading. Design/methodology/approach Experimental data from stress- and strain-controlled symmetric and asymmetric cyclic loadings have been used for this purpose. The analysis of the influence of the parameters on simulation accuracy has led to an adjustment scheme that can be used for focused optimisation of the MAFM model performance. The method was successfully used to provide a better understanding of the influence of each model parameter on the overall simulation accuracy. Findings The optimisation identified an important issue associated with competing ratcheting and mean stress relaxation objectives, highlighting the issues with arriving at a parameter set that can simulate ratcheting and mean stress relaxation for load cases not reaching at complete relaxation. Practical implications The study uses a strain-life fatigue application to demonstrate the importance of incorporating a technique such as the presented multiobjective optimisation method to arrive at robust parameters capable of accurately simulating a variety of transient cyclic phenomena. Originality/value The proposed methodology improves the accuracy of cyclic plasticity phenomena and strain-life fatigue simulations for engineering applications. This study is considered a valuable contribution for the engineering community, as it can act as starting point for further exploration of the benefits that can be obtained through material parameter optimisation methodologies for models of the MAFM class.

An Evaluation of Several Constitutive Model Structures for Transient Nonproportional Cyclic Plasticity

1986 ◽  
Vol 108 (3) ◽  
pp. 273-279 ◽  
Author(s):  
W. Sotolongo ◽  
D. L. McDowell
Keyword(s):  
Experimental Data ◽  
Constitutive Model ◽  
Constitutive Models ◽  
Plasticity Theory ◽  
Cyclic Plasticity ◽  
Multiaxial Loading ◽  
Torsional Loading ◽  
Integration Algorithm ◽  
Surface Theory ◽  
Model Structures

Four constitutive models for cyclic plasticity of different essential structure are evaluated under conditions of nonproportional, multiaxial loading. Drucker’s one-surface theory, McDowell’s two-surface theory, Krieg’s one-surface theory with Radial-Return Integration Algorithm, and Abrahamson’s Unified Creep-Plasticity theory are the constitutive models under consideration. Their transient hardening and stable loop responses are compared to experimental data for two nonproportional axial-torsional loading histories. Their computational efficiency is also analyzed.

Out-of-Phase and In-Phase Thermo-Mechanical Fatigue Response Simulations of Haynes 230

2014 ◽  
Author(s):  
Raasheduddin Ahmed ◽  
Paul R. Barrett ◽  
Tasnim Hassan
Keyword(s):  
High Temperature ◽  
Constitutive Model ◽  
Gas Turbines ◽  
Rate Dependence ◽  
Maximum Temperature ◽  
Large Set ◽  
Mean Stress ◽  
Stress Evolution ◽  
Haynes 230 ◽  
Mechanical Fatigue

Temperatures at critical locations in propulsion turbine engine combustor components can be as high as 982°C (1800°F). High temperature thermal gradients, and start-up and shut-down operations of gas turbines, induce thermo-mechanical fatigue (TMF) failure. Dwell periods at high temperatures accompanied by repeated loading cycles, eventually lead to failure of the components through creep-fatigue processes. In an effort to decipher the complex high temperature phenomena, a large set of isothermal and thermo-mechanical fatigue experiments have been carried out on the gas turbine combustor liner material, Haynes 230. The out-of-phase strain-controlled TMF experiments with compressive peak hold result in mean stress evolution in the tensile direction, whereas the in-phase TMF experiments with tensile peak hold result in mean stress evolution in the compressive direction. Experimental results indicate that the maximum temperature in the loading cycle influences the material property evolution with cycle. A unified viscoplastic constitutive model based on the Chaboche type nonlinear kinematic hardening rule was developed, including the added features of strain range dependence, rate dependence, temperature rate dependence, static recovery, mean stress evolution, and maximum temperature influence. The new constitutive model was validated against stress-strain responses of Haynes 230 under TMF loading. Paper published with permission.

scholarly journals Identification of Existing Challenges and Future Trends for the Utilization of Ammonia-Water Absorption–Compression Heat Pumps at High Temperature Operation

2021 ◽  
Vol 11 (10) ◽  
pp. 4635
Author(s):  
Marcel Ulrich Ahrens ◽  
Maximilian Loth ◽  
Ignat Tolstorebrov ◽  
Armin Hafner ◽  
Stephan Kabelac ◽  
...  
Keyword(s):  
High Temperature ◽  
Water Absorption ◽  
Industrial Sector ◽  
Heat Pumps ◽  
Working Fluid ◽  
Large Temperature ◽  
Future Trends ◽  
Ammonia Water ◽  
Starting Point ◽  
High Temperature Operation

Decarbonization of the industrial sector is one of the most important keys to reducing global warming. Energy demands and associated emissions in the industrial sector are continuously increasing. The utilization of high temperature heat pumps (HTHPs) operating with natural fluids presents an environmentally friendly solution with great potential to increase energy efficiency and reduce emissions in industrial processes. Ammonia-water absorption–compression heat pumps (ACHPs) combine the technologies of an absorption and vapor compression heat pump using a zeotropic mixture of ammonia and water as working fluid. The given characteristics, such as the ability to achieve high sink temperatures with comparably large temperature lifts and high coefficient of performance (COP) make the ACHP interesting for utilization in various industrial high temperature applications. This work reviews the state of technology and identifies existing challenges based on conducted experimental investigations. In this context, 23 references with capacities ranging from 1.4 kW to 4500 kW are evaluated, achieving sink outlet temperatures from 45 °C to 115 °C and COPs from 1.4 to 11.3. Existing challenges are identified for the compressor concerning discharge temperature and lubrication, for the absorber and desorber design for operation and liquid–vapor mixing and distribution and the choice of solution pump. Recent developments and promising solutions are then highlighted and presented in a comprehensive overview. Finally, future trends for further studies are discussed. The purpose of this study is to serve as a starting point for further research by connecting theoretical approaches, possible solutions and experimental results as a resource for further developments of ammonia-water ACHP systems at high temperature operation.

Theoretical determination of the structures of CaSiO3 perovskites

2006 ◽  
Vol 62 (6) ◽  
pp. 1025-1030 ◽  
Author(s):  
Razvan Caracas ◽  
Renata M. Wentzcovitch
Keyword(s):  
Crystal Structure ◽  
Experimental Data ◽  
Density Functional Theory ◽  
Density Functional ◽  
Theoretical Determination ◽  
Functional Theory ◽  
Starting Point ◽  
Atomic Coordinates ◽  
The Ideal

Density functional theory is used to determine the possible crystal structure of the CaSiO3 perovskites and their evolution under pressure. The ideal cubic perovskite is considered as a starting point for studying several possible lower-symmetry distorted structures. The theoretical lattice parameters and the atomic coordinates for all the structures are determined, and the results are discussed with respect to experimental data.

A Method for Predicting the Behavior of Plastics at Different Temperatures

2014 ◽  
Vol 1039 ◽  
pp. 107-111
Author(s):  
Yang Chen ◽  
Gui Qin Li ◽  
Bin Ruan ◽  
Xiao Yuan ◽  
Hong Bo Li
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Constitutive Model ◽  
Research And Development ◽  
Mechanical Behavior ◽  
Plastic Material ◽  
Different Temperatures ◽  
Plastic Parts

The mechanical behavior of plastic material is dramatically sensitive to temperature. An method is proposed to predict the mechanical behavior of plastics for cars, ranging from low-temperature low temperature ≤-40°C to high temperature ≥80°C. It dominates the behavior of plastic material based on improved constitutive model in which the parameters adjusted by a series of tests under different temperatures. The method is validated with test and establishes the basis for research and development of plastic parts for automobile as well.

A Cyclic Plasticity Modeling for Uniaxial and Multiaxial Ratcheting Simulation of Austenitic Steel

2012 ◽  
Author(s):  
Salim Meziani ◽  
Lynda Djimli
Keyword(s):  
Experimental Data ◽  
Stainless Steel ◽  
Constitutive Model ◽  
Data Base ◽  
Good Choice ◽  
Cyclic Plasticity ◽  
Strain History ◽  
Material Parameters ◽  
Plastic Shakedown

The first objective of this paper investigates the influence of the previous strain history on ratcheting of the 304 L stainless steel on ambient temperature. The identification is done using the Chaboche constitutive model. New tests were performed where different strain-controlled histories have been applied prior to ratcheting tests. It is demonstrated that under the same conditions, one can observe ratcheting, plastic shakedown or elasticity according to the prior strain-controlled history. The second objective points out the correlation between the experimental data base devoted to the identification of the material parameters and the quality of the predictions in cyclic plasticity. The results suggest that the choice of the tests should be closely linked to the capabilities of the model. In particular, the presence of non proportional strain-controlled tests in the data base may be not a good choice if the model itself is not able to represent explicitly such a character.

scholarly journals High temperatures during microsporogenesis fatally shorten pollen lifespan

2021 ◽  
Author(s):  
Maurizio Iovane ◽  
Giovanna Aronne
Keyword(s):  
Experimental Data ◽  
Heat Treatment ◽  
Heat Stress ◽  
High Temperature ◽  
Male Gametophyte ◽  
Crop Productivity ◽  
Anther Dehiscence ◽  
Optimal Temperature ◽  
Drastic Reduction ◽  
Crop Species

AbstractMany crop species are cultivated to produce seeds and/or fruits and therefore need reproductive success to occur. Previous studies proved that high temperature on mature pollen at anther dehiscence reduce viability and germinability therefore decreasing crop productivity. We hypothesized that high temperature might affect pollen functionality even if the heat treatment is exerted only during the microsporogenesis. Experimental data on Solanum lycopersicum ‘Micro-Tom’ confirmed our hypothesis. Microsporogenesis successfully occurred at both high (30 °C) and optimal (22 °C) temperature. After the anthesis, viability and germinability of the pollen developed at optimal temperature gradually decreased and the reduction was slightly higher when pollen was incubated at 30 °C. Conversely, temperature effect was eagerly enhanced in pollen developed at high temperature. In this case, a drastic reduction of viability and a drop-off to zero of germinability occurred not only when pollen was incubated at 30 °C but also at 22 °C. Further ontogenetic analyses disclosed that high temperature significantly speeded-up the microsporogenesis and the early microgametogenesis (from vacuolated stage to bi-cellular pollen); therefore, gametophytes result already senescent at flower anthesis. Our work contributes to unravel the effects of heat stress on pollen revealing that high temperature conditions during microsporogenesis prime a fatal shortening of the male gametophyte lifespan.

scholarly journals Multi-Scale Analyses and Modeling of Metallic Nano-Layers

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 450
Author(s):  
Zara Moleinia ◽  
David Bahr
Keyword(s):  
Experimental Data ◽  
Constitutive Model ◽  
Crystal Plasticity ◽  
Single Layer ◽  
Adaptive Boosting ◽  
Multi Scale ◽  
Nano Scale ◽  
Boosting Technique ◽  
Constitutive Parameters ◽  
Computational Processes

The current work centers on multi-scale approaches to simulate and predict metallic nano-layers’ thermomechanical responses in crystal plasticity large deformation finite element platforms. The study is divided into two major scales: nano- and homogenized levels where Cu/Nb nano-layers are designated as case studies. At the nano-scale, a size-dependent constitutive model based on entropic kinetics is developed. A deep-learning adaptive boosting technique named single layer calibration is established to acquire associated constitutive parameters through a single process applicable to a broad range of setups entirely different from those of the calibration. The model is validated through experimental data with solid agreement followed by the behavioral predictions of multiple cases regarding size, loading pattern, layer type, and geometrical combination effects for which the performances are discussed. At the homogenized scale, founded on statistical analyses of microcanonical ensembles, a homogenized crystal plasticity-based constitutive model is developed with the aim of expediting while retaining the accuracy of computational processes. Accordingly, effective constitutive functionals are realized where the associated constants are obtained via metaheuristic genetic algorithms. The model is favorably verified with nano-scale data while accelerating the computational processes by several orders of magnitude. Ultimately, a temperature-dependent homogenized constitutive model is developed where the effective constitutive functionals along with the associated constants are determined. The model is validated by experimental data with which multiple demonstrations of temperature effects are assessed and analyzed.

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