Fatigue Deformation

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B. Ramaswami - One of the best experts on this subject based on the ideXlab platform.

  • Interface sliding, migration, and cracking during Fatigue Deformation of a superplastic aluminum-zinc eutectoid alloy
    Metallurgical Transactions A, 1990
    Co-Authors: J. W. Bowden, B. Ramaswami
    Abstract:

    A superplastic aluminum-zinc eutectoid alloy was Fatigue tested at 100 °C and 200 °C at different constant plastic strain amplitudes and strain rates. During Fatigue Deformation, the average peak stress increased with increasing strain rate and grain size and decreasing temperature. It was almost independent of the plastic strain amplitude. To detect interfacial sliding, interphase boundary migration, and intergranular cracking, selected areas on surfaces were examined before Fatigue Deformation and re-examined after Fatigue Deformation. Interface sliding, which was almost reversible, occurred on (Al)/(Al) and (Zn)/(Zn) grain boundaries and on (Al)/(Zn) interphase boundaries. Grains appeared to slide in groups. Cracks followed grain and interphase boundaries. Along an intergranular crack, most interfaces were (Zn)/(Zn) grain boundaries and (Al)/ (Zn) interphase boundaries. Grains deformed to accommodate interfacial sliding. The absence of slip lines suggested that diffusional creep made a significant contribution to Deformation in grains of the zinc-rich phase. Deformation of the aluminum-rich phase involved the glide and climb of dislocations.

  • The effect of Fatigue Deformation on microstructural evolution in a superplastic aluminum-zinc eutectoid alloy
    Metallurgical Transactions A, 1990
    Co-Authors: J. W. Bowden, B. Ramaswami
    Abstract:

    The microstructure of a superplastic aluminum-zinc eutectoid alloy that had been Fatigue tested at 100 °C and 200 °C was examined. At 100 °C, in the aluminum-rich phase, precipitate-free zones (PFZs) formed beside (Al)/(Zn) interphase boundaries because of interphase boundary migration. Interphase boundary migration was due to phase growth, which proceeded more rapidly during Fatigue Deformation than during annealing. At 100 °C and 200 °C, PFZs beside (Al)/(Al) grain boundaries were asymmetrical owing to grain boundary migration. The precipitation of the equilibrium zinc-rich phase in the aluminum-rich phase proceeded more rapidly during Fatigue Deformation than during annealing.

J. W. Bowden - One of the best experts on this subject based on the ideXlab platform.

  • Interface sliding, migration, and cracking during Fatigue Deformation of a superplastic aluminum-zinc eutectoid alloy
    Metallurgical Transactions A, 1990
    Co-Authors: J. W. Bowden, B. Ramaswami
    Abstract:

    A superplastic aluminum-zinc eutectoid alloy was Fatigue tested at 100 °C and 200 °C at different constant plastic strain amplitudes and strain rates. During Fatigue Deformation, the average peak stress increased with increasing strain rate and grain size and decreasing temperature. It was almost independent of the plastic strain amplitude. To detect interfacial sliding, interphase boundary migration, and intergranular cracking, selected areas on surfaces were examined before Fatigue Deformation and re-examined after Fatigue Deformation. Interface sliding, which was almost reversible, occurred on (Al)/(Al) and (Zn)/(Zn) grain boundaries and on (Al)/(Zn) interphase boundaries. Grains appeared to slide in groups. Cracks followed grain and interphase boundaries. Along an intergranular crack, most interfaces were (Zn)/(Zn) grain boundaries and (Al)/ (Zn) interphase boundaries. Grains deformed to accommodate interfacial sliding. The absence of slip lines suggested that diffusional creep made a significant contribution to Deformation in grains of the zinc-rich phase. Deformation of the aluminum-rich phase involved the glide and climb of dislocations.

  • The effect of Fatigue Deformation on microstructural evolution in a superplastic aluminum-zinc eutectoid alloy
    Metallurgical Transactions A, 1990
    Co-Authors: J. W. Bowden, B. Ramaswami
    Abstract:

    The microstructure of a superplastic aluminum-zinc eutectoid alloy that had been Fatigue tested at 100 °C and 200 °C was examined. At 100 °C, in the aluminum-rich phase, precipitate-free zones (PFZs) formed beside (Al)/(Zn) interphase boundaries because of interphase boundary migration. Interphase boundary migration was due to phase growth, which proceeded more rapidly during Fatigue Deformation than during annealing. At 100 °C and 200 °C, PFZs beside (Al)/(Al) grain boundaries were asymmetrical owing to grain boundary migration. The precipitation of the equilibrium zinc-rich phase in the aluminum-rich phase proceeded more rapidly during Fatigue Deformation than during annealing.

Andreas Klenk - One of the best experts on this subject based on the ideXlab platform.

Weizhe Wang - One of the best experts on this subject based on the ideXlab platform.

Raghu Sandhya - One of the best experts on this subject based on the ideXlab platform.

  • A comparative assessment of Fatigue Deformation behavior of 316 LN SS at ambient and high temperature
    Materials Science and Engineering: A, 2017
    Co-Authors: Sunil Goyal, Raghu Sandhya, Sujoy Mandal, P. Parameswaran, C.n. Athreya, K. Laha
    Abstract:

    Abstract In this study, the low cycle Fatigue Deformation of 316 LN stainless steel has been assessed and compared for relatively low and high temperatures. Low cycle Fatigue tests were carried out on the steel at 298 K and 873 K employing strain amplitudes ranging from ±0.3% to ±1.0% at a strain rate of 3×10 −3  s −1 . At both the temperatures, the material exhibited initial hardening followed by gradual softening to the saturation stage and final failure. Comparison of hysteresis loops at saturation revealed that the material exhibited Masing behavior at lower strain amplitudes and non-Masing behavior at relatively higher strain amplitudes at 298 K whereas a reverse trend was observed at 873 K. Manifestation of Masing and non-Masing behavior was reflected in the dual slope cyclic stress- strain relationship. The change from Masing to non-Masing behavior and vice versa depending on the temperature and strain amplitude has been corroborated with the transmission electron microscopic and electron backscattered diffraction investigation. The dislocation substructure was found to depend on the temperature and strain amplitude. At 298 K, pile-up in the planar slip and tendency to develop cell structure was observed at lower and higher strain amplitudes, respectively. However, dislocation pinning resulting from DSA and well developed cell structure was observed at lower and higher strain amplitudes, respectively at 873 K. The Fatigue life has been predicted based on the hysteresis energy approach considering both the Masing and non-Masing behavior and it was observed that the non-Masing analysis predicts the Fatigue life more accurately than the Masing analysis.

  • Strain controlled Fatigue Deformation and fracture of nitrogen alloyed 316LN austenitic stainless steel
    Transactions of The Indian Institute of Metals, 2010
    Co-Authors: G.v. Prasad Reddy, M. Valsan, Raghu Sandhya, S. Sankaran
    Abstract:

    In this paper, Low cycle Fatigue (LCF) behavior of 316LN austenitic stainless steel alloyed with 0.078 and 0.22 wt% nitrogen, designated as N078 and N022 steels respectively, is compared in the temperature range 300–873 K by strain controlled Fatigue tests at ± 0.6% strain amplitude. Interestingly, N022 steel showed continuous decrease in Fatigue life with temperature in contrast to N078 steel which showed maximum in Fatigue life at 573 K. Drastic reduction in Fatigue life is observed in both the steels in the temperature range 673–873 K and has been attributed to the occurrence of dynamic strain aging. Both steels exhibited manifestations (for ex.: decrease in plastic strain and anomalous stress response with increase in temperature) corresponding to the occurrence of Dynamic Strain Ageing (DSA) in the above temperature range. Under all testing conditions, fracture surfaces revealed transgranular crack initiation and transgranular crack propagation.

  • on dual slope linear cyclic hardening of hastelloy x
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010
    Co-Authors: G Prasad V Reddy, P Harini, Raghu Sandhya, R.k. Paretkar
    Abstract:

    In low cycle Fatigue Deformation of Hastelloy X, a unique dual-slope linear cyclic hardening is observed, with transition region in between, followed by non-linear hardening till failure. Though both temperature and accumulated strain can enhance the carbide precipitation, interestingly it is observed that transition region is found to be more sensitive to change in applied strain amplitude rather than changes in temperature.

  • An anomalous cyclic stress evolution in reduced activation ferritic/martensitic steel
    Materials Science and Engineering: A, 2010
    Co-Authors: G.v. Prasad Reddy, Raghu Sandhya, K. Laha, M.d. Mathew
    Abstract:

    Abstract An anomalous cyclic stress response characterized by decrease in cyclic stress with increase in strain amplitude is observed in 9Cr–1W reduced activation ferritic/martensitic steel, during low cycle Fatigue Deformation at 823 K. It is suggested that differences in reduction of internal and effective stress components delineate the nature of cyclic stress response.

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