You need to design a metallic glass for use in industry. The glass transition temperature of the metallic glass is 250°C. While in use, the sample will be subjected to a permanent tensile stress for tuse=6 years and at a temperature of Tuse=230°C. You need to do the necessary creep experiment in the lab to predict the performance of this material by applying the same stress at different temperature and different time. The creep test will be carried out for tiab=6 hours. At what temperature, Tiab, can this test be performed in the lab under the same tensile stress? [Hint: Use WLF and VFT equations for two cases: 1) Tref#T =250 °C and 2) Tre=260 °C.]
Design Against Fluctuating Loads
Machine elements are subjected to varieties of loads, some components are subjected to static loads, while some machine components are subjected to fluctuating loads, whose load magnitude tends to fluctuate. The components of a machine, when rotating at a high speed, are subjected to a high degree of load, which fluctuates from a high value to a low value. For the machine elements under the action of static loads, static failure theories are applied to know the safe and hazardous working conditions and regions. However, most of the machine elements are subjected to variable or fluctuating stresses, due to the nature of load that fluctuates from high magnitude to low magnitude. Also, the nature of the loads is repetitive. For instance, shafts, bearings, cams and followers, and so on.
Design Against Fluctuating Load
Stress is defined as force per unit area. When there is localization of huge stresses in mechanical components, due to irregularities present in components and sudden changes in cross-section is known as stress concentration. For example, groves, keyways, screw threads, oil holes, splines etc. are irregularities.
![Problem#3:
You need to design a metallic glass for use in industry. The glass transition
temperature of the metallic glass is 250°C. While in use, the sample will be subjected
to a permanent tensile stress for tuse=6 years and at a temperature of Tuse=230°C.
You need to do the necessary creep experiment in the lab to predict the
performance of this material by applying the same stress at different temperature
and different time. The creep test will be carried out for tiab=6 hours. At what
temperature, Tlab, can this test be performed in the lab under the same tensile
stress? [Hint: Use WLF and VFT equations for two cases: 1) Tref=Tg =250 °C and 2)
Tr=260 °C.]](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F7f60502e-4aef-4bdc-aaa4-2eb4e0ea72a4%2Fbade7d97-9f2b-42b7-853e-087747f3af5f%2Fx8bga5q_processed.jpeg&w=3840&q=75)
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