How to Calculate Shaft Diameter for Fluctuating Loads

TL;DR

To calculate the shaft diameter under fluctuating loads, first find the mean and amplitude values of the bending and torsional moments. Apply the Goodman criteria using these values to determine the safe amplitude stress, leading to an approximate shaft diameter of 33.29 mm.

Transcript

click the bell icon to get latest videos from akira hello friends welcome back to a subject of machine design WA we are right now learning or we are light now working on the numerical which are depicting the combined stresses and how to solve it so today let us look at such an example where multiple loadings are given let's quickly read out and try... Read More

Key Insights

• 🎰 Combined stresses in machine design involve considering multiple loadings such as bending moments and torsional moments.
• ❓ Mean and amplitude values for stresses can be determined by converting the respective moments and employing suitable formulas.
• 🥳 The Goodman criteria is utilized to determine the safe amplitude stress, taking into account the ratio between the amplitude stress and the mean stress, as well as material properties.

Questions & Answers

Q: What is the main objective of this video?

The main objective of this video is to solve a numerical problem in machine design involving combined stresses, specifically addressing a shaft carrying a pulley with varying bending and torsional moments.

Q: What are the factors given to solve the problem?

The problem provides the bending moment (ranging from 200 Nm to 600 Nm), torsional moment (ranging from 70 Nm to 200 Nm), material properties (ultimate strength, yield strength, and endurance limit), and a factor of safety.

Q: How are the mean and amplitude values for stress determined?

The mean and amplitude values for stress are obtained by converting the bending and torsional moments into stress values using suitable formulas.

Q: What criteria is used to determine the safe amplitude value?

The Goodman criteria is used to determine the safe amplitude value, considering the ratio between the amplitude stress and the mean stress, along with the yield strength and endurance limit.

Q: How is the shaft diameter calculated?

By using the obtained values for the safe amplitude stress and the given design aspects of fluctuating loads, the shaft diameter is calculated using the Goodman criteria.

Summary & Key Takeaways

• The video addresses a numerical problem involving a shaft carrying a pulley with two bearing ends, where the bending moment varies between 200 Nm and 600 Nm, and the torsional moment varies between 70 Nm and 200 Nm.

• The material properties, such as ultimate strength, yield strength, endurance limit, and factor of safety, are provided, and the goal is to determine the shaft diameter.

• The video explains the process of finding the mean and amplitude values for the bending and torsional moments, converting them into stresses, and using the Goodman criteria to determine the safe amplitude value.

• Ultimately, the shaft diameter is calculated to be approximately 33.29 mm using the given design aspects of fluctuating loads.