Bearings Combined Loading and Equivalent Load - Example 1

Introduction

This tutorial aims to guide you through the concepts of bearings under combined loading conditions, specifically focusing on how to calculate equivalent loads and understand key factors influencing bearing performance. This information is essential for mechanical engineers and anyone involved in machinery design.

Step 1: Understand Basic Terminology

Before diving into calculations, familiarize yourself with the key terms:

• Radial Load: The force applied perpendicular to the shaft's axis.
• Axial Load: The force applied parallel to the shaft's axis.
• Equivalent Radial Load: A calculated load that combines both radial and axial loads into a single radial load for analysis.
• C0: Basic static load rating, the maximum load a bearing can withstand without permanent deformation.
• C: Basic dynamic load rating, the load that a bearing can endure for a specified number of revolutions.

Step 2: Calculate the Equivalent Radial Load

To compute the equivalent radial load, follow these steps:

1. Identify Loads: Determine the radial and axial loads acting on the bearing (Fr and Fa).

2. Use the Formula: Apply the following formula to calculate the equivalent radial load (Fe):

   [ Fe = Fr + Y \cdot Fa ]

   Where Y is a factor that depends on the bearing type and load conditions. Common values for Y can be found in bearing manufacturer tables.

3. Interpret Results: The calculated equivalent load helps evaluate bearing performance under the combined loading scenario.

Step 3: Assess Bearing Life

Once you have the equivalent radial load, you can evaluate the bearing's expected life using the formula:

[ L_{10} = \left( \frac{C}{Fe} \right)^3 ]

Where:

• (L_{10}) is the bearing life in millions of revolutions.
• (C) is the basic dynamic load rating.
• (Fe) is the equivalent radial load calculated in the previous step.

Practical Tip

Always refer to the manufacturer's load rating tables to ensure you have the correct values for (C) and (Y).

Step 4: Consider the Influence of Load Rotational Factor

The load rotational factor (V) accounts for variations in load during operation. To calculate it:

1. Assess Load Variability: Determine if the loads are constant or fluctuate during operation.

2. Apply the Factor: Modify your equivalent load calculation by including the rotational factor as follows:

   [ Fe_{adjusted} = V \cdot Fe ]

3. Use Adjusted Load for Life Calculation: Repeat the bearing life calculation using the adjusted equivalent load.

Conclusion

Understanding how to calculate equivalent radial loads and assess bearing life under combined loading is crucial for reliable machinery design. Ensure to consider both static and dynamic load ratings, along with rotational factors, for accurate predictions. As a next step, explore specific bearing types and their load ratings to apply these concepts in real-world scenarios. For further learning, check out related videos on axial loading and bearing reliability linked in the video description.