In-Vacuum Cyclic Fatigue Behavior of Vanstar-7 at Elevated Temperatures

One possibility to improve the fatigue life and strength of metallic materials is shot peening. However, at elevated temperatures, the induced residual stresses may relax. To investigate the influence of shot peening on high-temperature fatigue behavior, isothermal fatigue tests were conducted on shot-peened and untreated samples of gamma TiAl 48-2-2 at 750 °C in air. The shot-peened material was characterized using EBSD, microhardness, and residual stress analyses. Shot peening leads to a significant increase in surface hardness and high compressive residual stresses near the surface. Both effects may have a positive influence on lifetime. However, it also leads to surface notches and tensile residual stresses in the bulk material with a negative impact on cyclic lifetime. During fully reversed uniaxial tension-compression fatigue tests (R = −1) at a stress amplitude of 260 MPa, the positive effects dominate, and the fatigue lifetime increases. At a lower stress amplitude of 230 MPa, the negative effect of internal tensile residual stresses dominates, and the lifetime decreases. Shot peening leads to a transition from surface to volume crack initiation if the surface is not damaged by the shots.

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Tensile and fatigue behavior of polymer supported silver thin films at elevated temperatures

Materials Letters ◽

10.1016/j.matlet.2017.01.111 ◽

2017 ◽

Vol 193 ◽

pp. 81-84 ◽

Cited By ~ 6

Author(s):

Yong-Seok Lee ◽

Gi-Dong Sim ◽

Jong-Soo Bae ◽

Ji-Young Kim ◽

Soon-Bok Lee

Keyword(s):

Thin Films ◽

Elevated Temperatures ◽

Fatigue Behavior ◽

Polymer Supported ◽

Silver Thin Films

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Thermal Stability of Residual Stresses in Differently Deep Rolled Surface Layers of Steel SAE 1045

Journal of Materials Engineering and Performance ◽

10.1007/s11665-021-05798-x ◽

2021 ◽

Author(s):

Stephanie Saalfeld ◽

Thomas Wegener ◽

Berthold Scholtes ◽

Thomas Niendorf

Keyword(s):

Thermal Stability ◽

Elevated Temperature ◽

Residual Stresses ◽

Elevated Temperatures ◽

Fatigue Behavior ◽

Decisive Role ◽

Deep Rolling ◽

Material Conditions ◽

The Stability ◽

Thermal Stability Of

AbstractThe stability of compressive residual stresses generated by deep rolling plays a decisive role on the fatigue behavior of specimens and components, respectively. In this regard, deep rolling at elevated temperature has proven to be very effective in stabilizing residual stresses when fatigue analysis is conducted at ambient temperature. However, since residual stresses can be affected not only by plastic deformation but also when thermal energy is provided, it is necessary to analyze the influence of temperature and time on the relaxation behavior of residual stresses at elevated temperature. To evaluate the effect of deep rolling at elevated temperatures on stability limits under thermal as well as combined thermo-mechanical loads, the present work introduces and discusses the results of investigations on the thermal stability of residual stresses in differently deep rolled material conditions of the steel SAE 1045.

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Fatigue behavior of a 22Cr_20Ni_18Co_Fe alloy at elevated temperatures Krukemyer, T.H., Fatemi, A. and Swindeman, R.W. J. Eng. Mater. Technol. (Trans. ASME) (Jan. 1994) 116 (1), 54–61

International Journal of Fatigue ◽

10.1016/0142-1123(95)90077-2 ◽

1995 ◽

Vol 17 (1) ◽

pp. 74

Keyword(s):

Elevated Temperatures ◽

Fatigue Behavior ◽

Trans Asme

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Isothermal Fatigue Behavior and Damage Modeling of a High Temperature Woven PMC

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.483176 ◽

1999 ◽

Vol 122 (1) ◽

pp. 62-68 ◽

Cited By ~ 1

Author(s):

A. L. Gyekenyesi

Keyword(s):

Compressive Strength ◽

Elevated Temperature ◽

Elevated Temperatures ◽

Fatigue Behavior ◽

Stiffness Degradation ◽

Fatigue Properties ◽

Residual Compressive Strength ◽

Stiffness Reduction ◽

Fatigue Damage Accumulation ◽

Strength Tests

This study focuses on the fully reversed fatigue behavior exhibited by a carbon fiber/polyimide resin woven laminate at room and elevated temperatures. Nondestructive video edge view microscopy and destructive sectioning techniques were used to study the microscopic damage mechanisms that evolved. The elastic stiffness was monitored and recorded throughout the fatigue life of the coupon. In addition, residual compressive strength tests were conducted on fatigue coupons with various degrees of damage as quantified by stiffness reduction. Experimental results indicated that the monotonic tensile properties were only minimally influenced by temperature, while the monotonic compressive and fully reversed fatigue properties displayed greater reductions due to the elevated temperature. The stiffness degradation, as a function of cycles, consisted of three stages; a short-lived high degradation period, a constant degradation rate segment covering the majority of the life, and a final stage demonstrating an increasing rate of degradation up to failure. Concerning the residual compressive strength tests at room and elevated temperatures, the elevated temperature coupons appeared much more sensitive to damage. At elevated temperatures, coupons experienced a much larger loss in compressive strength when compared to room temperature coupons with equivalent damage. The fatigue damage accumulation law proposed for the model incorporates a scalar representation for damage, but admits a multiaxial, anisotropic evolutionary law. The model predicts the current damage (as quantified by residual stiffness) and remnant life of a composite that has undergone a known load at temperature. The damage/life model is dependent on the applied multiaxial stress state as well as temperature. Comparisons between the model and data showed good predictive capabilities concerning stiffness degradation and cycles to failure. [S0742-4795(00)01001-2]

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