Fatigue data of steel is showed in the following stress-cycle curve. Write down the values of steel endurance limit and steel fatigue strength at 10^5 cycles in the spaces provided below. Steel Endurance Limit: _____ ksi teel Fatigue Strength at 10^5 cycles: _____ ksi
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.
Fatigue data of steel is showed in the following stress-cycle curve.
Write down the values of steel endurance limit and steel fatigue strength at 10^5 cycles in the spaces provided below.
Steel Endurance Limit: _____ ksi
teel Fatigue Strength at 10^5 cycles: _____ ksi
![The image depicts an S-N curve, which is used to illustrate the relationship between stress and the number of cycles to failure in materials. The graph is plotted with stress (in ksi) on the y-axis and the number of cycles on the x-axis. The x-axis is logarithmic, ranging from 10^3 to 10^9 cycles.
- **Steel Curve (Blue Line):** This curve starts at a higher stress level around 45 ksi and shows a decline as the number of cycles increases. Around 10^6 cycles, it reaches a plateau, indicating that steel has a fatigue limit or endurance limit, where it can withstand a certain level of stress indefinitely without failure.
- **Aluminum Curve (Red Line):** This curve starts slightly lower, around 42 ksi. It continuously declines without plateauing, indicating that aluminum does not have a fatigue limit. The stress level decreases progressively with an increase in the number of cycles.
This S-N curve is important for understanding the fatigue behavior of materials and helps in predicting the lifespan of materials under cyclic loading. Steel, with its endurance limit, can be a more reliable material under certain loading conditions compared to aluminum, which does not exhibit such a limit.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F24fdef28-930d-4185-868c-e03c58dc0160%2F71c2b07b-6855-4612-8300-32627152af55%2Fq38qtnt_processed.png&w=3840&q=75)
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Given S-N curve
To find
1. Steel Endurance Limit: _____ ksi
2. steel Fatigue Strength at 10^5 cycles: _____ ksi
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