An Energy-Based Axial Isothermal-Mechanical Fatigue Lifing Method

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
John Wertz ◽  
Todd Letcher ◽  
M.-H. Herman Shen ◽  
Onome Scott-Emuakpor ◽  
Tommy George ◽  
...  
Keyword(s):  
Strain Energy ◽  
Thermal Loading ◽  
Elevated Temperatures ◽  
Testing Procedure ◽  
Mechanical Fatigue ◽  
Full Life ◽  
Energy Dissipated ◽  
Life Predictions ◽  
Quasi Static Process

An energy-based fatigue lifing method for the determination of the full-life and critical-life of in-service structures subjected to axial isothermal-mechanical fatigue (IMF) has been developed. The foundation of this procedure is the energy-based axial room-temperature lifing model, which states: the total strain energy dissipated during both a quasi-static process and a dynamic (fatigue) process is the same material property. The axial IMF lifing framework is composed of the following entities: (1) the development of an axial IMF testing capability; (2) the creation of a testing procedure capable of assessing the strain energy dissipated during both a quasi-static process and a dynamic process at elevated temperatures; and (3) the incorporation of the effect of thermal loading into the axial fatigue lifing model. Both an axial IMF capability and a detailed testing procedure were created. The axial IMF capability was employed to produce full-life and critical-life predictions as functions of temperature, which were shown to have an excellent correlation with experimental fatigue data. For the highest operating temperature, the axial IMF full-life prediction was compared to lifing predictions made by both the universal slopes and the uniform material law prediction and was found to be more accurate at an elevated temperature.

An Energy-Based Axial Isothermal-Mechanical Fatigue Lifing Method

2012 ◽  
Author(s):  
John Wertz ◽  
Todd Letcher ◽  
M.-H. Herman Shen ◽  
Onome Scott-Emuakpor ◽  
Tommy George ◽  
...  
Keyword(s):  
Strain Energy ◽  
Thermal Loading ◽  
Elevated Temperatures ◽  
Testing Procedure ◽  
Mechanical Fatigue ◽  
Full Life ◽  
Energy Dissipated ◽  
Life Predictions ◽  
Quasi Static Process

An energy-based fatigue lifing method for the determination of the full-life and critical-life of in-service structures subjected to axial isothermal-mechanical fatigue (IMF) has been developed. The foundation of this procedure is the energy-based axial room-temperature lifing model, which states: the total strain energy dissipated during both a quasi-static process and a dynamic (fatigue) process is the same material property. The axial IMF lifing framework is composed of the following entities: (1) the development of an axial IMF testing capability; (2) the creation of a testing procedure capable of assessing the strain energy dissipated during both a quasi-static process and a dynamic process at elevated temperatures; and (3), the incorporation of the effect of thermal loading into the axial fatigue lifing model. Both an axial IMF capability and a detailed testing procedure were created. The axial IMF capability was employed to produce full-life and critical-life predictions as functions of temperature, which were shown to have excellent correlation with experimental fatigue data. For the highest operating temperature, the axial IMF full-life prediction was compared to lifing predictions made by both the Universal Slopes and the Uniform Material Law prediction and was found to be more accurate at elevated temperature.

An Energy-Based Axial Isothermal- Mechanical Fatigue Lifing Procedure

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
John Wertz ◽  
M.-H. Herman Shen ◽  
Onome Scott-Emuakpor ◽  
Tommy George ◽  
Charles Cross
Keyword(s):  
Strain Energy ◽  
Elevated Temperatures ◽  
Testing Procedure ◽  
Effect Of Temperature ◽  
Activation Temperature ◽  
Fatigue Process ◽  
Mechanical Fatigue ◽  
Fracture Event ◽  
Operating Temperatures ◽  
Total Strain Energy Density

An energy-based fatigue lifing procedure for the determination of full-life and critical-life of in-service structures subjected to axial isothermal-mechanical fatigue (IMF) has been developed. The foundation of this procedure is the energy-based axial room-temperature fatigue model, which states: the total strain energy density accumulated during both a monotonic fracture event and a fatigue process is the same material property. The energy-based axial IMF lifing framework is composed of the following entities: (1) the development of an axial IMF testing capability; (2) the creation of a testing procedure capable of assessing the strain energy accrued during both a monotonic fracture process and a fatigue process at various elevated temperatures; and (3), the incorporation of the effect of temperature into the axial fatigue lifing model. Both an axial IMF capability and a detailed testing procedure were created. The axial IMF capability was employed in conjunction with the monotonic fracture curve testing procedure to produce fifteen fracture curves at four operating temperatures. The strain energy densities for these fracture curves were compared, leading to the assumption of constant monotonic fracture energy at operating temperatures below the creep activation temperature.

An Energy-Based Axial Isothermal-Mechanical Lifing Procedure

2011 ◽  
Author(s):  
John Wertz ◽  
M.-H. Herman Shen ◽  
Onome Scott-Emuakpor ◽  
Tommy George ◽  
Charles Cross
Keyword(s):  
Strain Energy ◽  
Elevated Temperatures ◽  
Testing Procedure ◽  
Effect Of Temperature ◽  
Activation Temperature ◽  
Fatigue Process ◽  
Fracture Event ◽  
Operating Temperatures ◽  
Total Strain Energy Density

An energy-based fatigue lifing procedure for the determination of fatigue life and critical life of in-service structures subjected to axial isothermal-mechanical fatigue (IMF) has been developed. The foundation of this procedure is the energy-based axial room-temperature fatigue model, which states: the total strain energy density accumulated during both a monotonic fracture event and a fatigue process is the same material property. The energy-based axial IMF lifing framework is composed of the following entities: (1) the development of an axial IMF testing capability; (2) the creation of a testing procedure capable of assessing the strain energy accrued during both a monotonic fracture process and a fatigue process at various elevated temperatures; and (3), the incorporation of the effect of temperature into the axial fatigue lifing model. Both an axial IMF capability and a detailed testing procedure were created. The axial IMF capability was employed in conjunction with the monotonic fracture curve testing procedure to produce eight fracture curves at three operating temperatures. The strain energy densities for these fracture curves were compared, leading to the assumption of constant monotonic fracture energy at operating temperatures below the creep activation temperature.

Development of a Fatigue Damage and Lifing Assessment Method for Inconel 625 and Aluminum 6061-T6

2017 ◽  
Author(s):  
Dino Celli ◽  
M.-H. Herman Shen ◽  
Tommy George ◽  
Onome Scott-Emuakpor ◽  
Casey Holycross
Keyword(s):  
Fatigue Damage ◽  
Strain Energy ◽  
Room Temperature ◽  
Assessment Method ◽  
Fatigue Tests ◽  
Inconel 625 ◽  
Total Strain Energy ◽  
Mechanical Fatigue ◽  
Energy Dissipated ◽  
Good Agreement

An energy based fatigue damage and lifing assessment method is developed for a high temperature material, Inconel 625, and Aluminum 6061-T6. A newly developed experimental method is used for interrogating accumulated fatigue damage and evolution for low and high cycle fatigue (LCF/HCF) at continuum scales. The proposed fatigue lifing assessment method is based on assessing the total strain energy dissipated to cause fatigue failure of a material, known as the fatigue toughness. From the fatigue toughness and experimentally determined fatigue lives at two different stress amplitudes, the cyclic parameters of the Ramberg-Osgood constitutive equation that describes the hysteresis stress-strain loop of a cycle are determined. Stress controlled mechanical fatigue tests are performed to construct room temperature stress-life (S-N) curves and to determine damage progression based on accumulated fatigue damage. The predicted fatigue life obtained from the present energy based approach is found in good agreement with experimental data.

Experimental investigation on SFRC behaviour under elevated temperature

2017 ◽  
Vol 8 (3) ◽  
pp. 287-299 ◽  
Author(s):  
Vadims Goremikins ◽  
Lukas Blesak ◽  
Josef Novak ◽  
Frantisek Wald
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Elevated Temperatures ◽  
Bending Strength ◽  
Testing Procedure ◽  
Split Tensile Strength ◽  
Content Type ◽  
Steel Fibre Reinforced Concrete ◽  
Ultimate Bending Strength

Purpose This work aims to present an experimental study of steel fibre-reinforced concrete (SFRC) subjected to high temperature, especially focusing on residual behaviour. Design/methodology/approach Compressive strength and split tensile strength of SFRC cubes and ultimate bending strength of prisms were evaluated under ambient and elevated temperatures. The specimens were heated by ceramic heaters and then repacked for testing. Findings The results showed that a compressive strength of SFRC is reduced by 38 and 66 per cent, tensile strength is reduced by 25 and 59 per cent and ultimate bending force is reduced by 33 and 56 per cent in case of 400°C and 600°C, respectively, comparing with ambient temperature. Originality value The developed testing procedure could be used for determination of material properties of SFRC under elevated temperatures.

scholarly journals Research on the residual tensile strength of composite reinforcing bars exposed to elevated temperatures

2021 ◽  
Vol 1205 (1) ◽  
pp. 012011
Author(s):  
I Rozsypalova ◽  
J Prokes ◽  
Đ Cairović ◽  
F Girgle ◽  
P Danek ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Steady State ◽  
Analytical Approach ◽  
Elevated Temperatures ◽  
Reduction Rate ◽  
Testing Procedure ◽  
Reinforcing Bars ◽  
Gfrp Bars ◽  
Bar Diameter

Abstract Paper describes a testing procedure for the determination of tensile strength of the composite reinforcing bars subjected to elevated temperatures. Experimentally obtained results on GFRP bars with different diameter are presented and discussed. Moreover, a brief comparison with an analytical approach was included. Almost identical temperature reduction rate of tensile strength was observed for all tested specimens, regardless diameter of the bar. Therefore, it can be expected, that different bar diameter should not significantly affect the results especially if steady state conditions were assumed.

A Comparison of Constitutive Equations for the Energy-Based Lifing Method

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
John Wertz ◽  
Casey Holycross ◽  
M.-H. Herman Shen ◽  
Onome Scott-Emuakpor ◽  
Tommy George ◽  
...  
Keyword(s):  
Experimental Data ◽  
Dynamic Process ◽  
Constitutive Equations ◽  
Strain Energy ◽  
Endurance Limit ◽  
Predictive Accuracy ◽  
Total Strain Energy ◽  
Constitutive Relationships ◽  
Energy Dissipated ◽  
Quasi Static Process

Alternatives to quasi-static and dynamic constitutive relationships have been investigated with respect to a previously developed energy-based fatigue lifing method for various load profiles, which states: the total strain energy dissipated during both a quasi-static process and a dynamic process are equivalent and a fundamental material property. Specifically, constitutive relationships developed by Ramberg–Osgood and Halford were modified for application to the existing energy-based framework and were compared to the lifing method originally developed by Stowell. Extensive experimentation performed on Titanium 6Al-4V (Ti-64) combined with experimental data generated for Aluminum (Al) 6061-T6 at various temperatures were utilized in support of this investigation. This effort resulted in considerable improvements to the accuracy of the lifing prediction for materials with an endurance limit through application of a modified-Halford approach. Additionally, the relative equality in predictive accuracy between the modified-Stowell approach the modified-Ramberg–Osgood approach was demonstrated.

scholarly journals Chlorine-Functional Silsesquioxanes (POSS-Cl) as Effective Flame Retardants and Reinforcing Additives for Rigid Polyurethane Foams

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 3979
Author(s):  
Anna Strąkowska ◽  
Sylwia Członka ◽  
Karolina Miedzińska ◽  
Krzysztof Strzelec
Keyword(s):  
Flame Retardants ◽  
Elevated Temperatures ◽  
Bending Strength ◽  
Reaction System ◽  
Fire Retardant ◽  
Polyurethane Foams ◽  
Polymerization Reaction ◽  
Three Point Bending ◽  
One Step

The subject of the research was the production of silsesquioxane modified rigid polyurethane (PUR) foams (POSS-Cl) with chlorine functional groups (chlorobenzyl, chloropropyl, chlorobenzylethyl) characterized by reduced flammability. The foams were prepared in a one-step additive polymerization reaction of isocyanates with polyols, and the POSS modifier was added to the reaction system in an amount of 2 wt.% polyol. The influence of POSS was analyzed by performing a series of tests, such as determination of the kinetics of foam growth, determination of apparent density, and structure analysis. Compressive strength, three-point bending strength, hardness, and shape stability at reduced and elevated temperatures were tested, and the hydrophobicity of the surface was determined. The most important measurement was the determination of the thermal stability (TGA) and the flammability of the modified systems using a cone calorimeter. The obtained results, after comparing with the results for unmodified foam, showed a large influence of POSS modifiers on the functional properties, especially thermal and fire-retardant, of the obtained PUR-POSS-Cl systems.

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