Understanding Static Load vs. Dynamic Load in Bearings

Bearings play a vital role in machinery by ensuring smooth motion and reducing friction.

Understanding load capacities, specifically static load vs dynamic load, is essential for optimal bearing performance.

This blog will explain these load types and their importance in selecting the right bearing for your applications and custom bearing solutions, helping ensure reliable and efficient operations.

Understanding Bearing Loads

Static Load

Static load refers to the load exerted on a bearing when it is stationary or under slow movement.

• Static load capacity is the maximum load a bearing can endure without incurring permanent deformation.
• It is crucial for applications where the bearing may experience shock loads or heavy weights while not in motion.
• For example, the 608 Metric Ball Bearing is designed to handle static loads efficiently, ensuring minimal deformation under heavy weights while maintaining reliable performance. It's an ideal choice for applications requiring both compactness and durability.

Dynamic Load

Dynamic load refers to the load that a bearing supports during continuous movement, including both radial and axial loads.

• Dynamic load capacity is the maximum load a bearing can handle. It measures this load over a specific number of rotations or travel distance without fatigue.
• It determines the bearing's rated life, often referred to as L10 life, which is the life at which 90% of a group of identical bearings will still be operational under a given load and speed.
• Understanding dynamic load capacity is essential for applications involving constant rotation or oscillation, as it helps predict the bearing’s lifespan and reliability.

The Importance of Load Capacities

Understanding static and dynamic load capacities ensures the longevity and reliability of bearings.

Properly selected bearings can handle the expected loads without failure, reducing maintenance costs and downtime.

This knowledge is vital for engineers and technicians in designing and maintaining efficient machinery.

Static Load vs. Dynamic Load

Nature of Load:

• Static Load: Applied when the bearing is stationary or moves slowly.
• Dynamic Load: Applied during continuous movement.

Capacity Measurement:

• Static Load Capacity: Typically higher than dynamic load capacity, measured in force (Newtons or pounds).
• Dynamic Load Capacity: Focuses on bearing fatigue life under moving conditions.

Impact on Bearing Life:

• Exceeding Static Load Capacity: Can cause immediate, permanent damage such as brinelling.
• Exceeding Dynamic Load Capacity: Leads to increased bearing wear and reduced lifespan because of fatigue.

Static and Dynamic Loads for Rolling Element Linear Bearings

Rolling element linear bearings include round shafts, bushings, profiled rail guides, crossed roller slides, and ball screws.

They have two main load capacity specifications: dynamic load capacity and static load capacity. 

Understanding these specifications is crucial for accurately sizing and selecting bearings.

Measurement of Static Load

Static loads often arise from unexpected shocks that are challenging to measure.

To address this, manufacturers of linear bearings and ball screws recommend using a static safety factor.

This factor is the ratio between the basic static load rating and the maximum combined static load.

It varies based on the application and operating conditions.

For environments with low vibration risk, a factor of 2 is suggested.

For conditions with potential severe shocks, factors of 5 or 6 are advised to ensure reliability and prevent damage.

S₀ =C₀/F_0max​​​

Where:

S₀: the static load safety factor

C₀: the static load capacity

F_0max: the maximum combined static load

Measurement of Dynamic Load

Dynamic load capacity (C) is a crucial parameter for determining the lifespan and reliability of rolling element linear bearings under continuous motion.

This capacity is derived through empirical testing, where a bearing is subjected to a constant load magnitude and direction.

The bearing must reach a specific travel distance or number of revolutions without showing fatigue.

Fatigue appears as flaking on the rolling elements or raceways.

• Dynamic Load Capacity (C): This is the load a bearing can support during continuous motion. It must handle this load for a specified distance or number of revolutions without experiencing fatigue. This measurement is crucial for applications that involve constant movement, such as in linear guides and ball screws.
• Rated Life (L₁₀): The L₁₀ life is a statistical measure used to indicate the reliability of bearings. It represents the distance or number of cycles that 90% of identical bearings can achieve without failing. This is under specified conditions. The L₁₀ life calculation is standardized by ISO 14728-1 for linear bearings and ISO 3408-5 for ball screws.

For linear bearings using balls:

L₁₀=(C/F)³×100,000

For linear bearings that use rollers:

L₁₀=(C/F)^10/3×100,000

Where:

L₁₀: calculated (rated) life of the bearing in meters

C: basic dynamic load capacity (N)

F: applied load (N)

Conversion for Travel Distance:

If comparing bearings rated for different travel distances, use the following conversion:

• Divide the 50,000 m load capacity by 1.26, or
• Multiply the 100,000 m load capacity by 1.26

Factors Influencing Load Capacities

• Material Quality: High-quality materials can withstand higher bearing loads and reduce the risk of deformation.
• Bearing Lubrication: Proper lubrication minimizes friction and wear, enhancing load capacity.
• Operating Environment: Conditions such as temperature, contamination, and moisture can affect load capacities.
• Mounting and Alignment: Correct installation ensures even load distribution and maximizes bearing life.
• Application Type: Different applications impose varying load conditions, influencing the choice of bearing capacity.

Get Your Bearings at LILY Bearing

LILY Bearing offers a wide selection of high-quality industrial bearings suitable for various applications.

Our expert team can help you choose the right bearings based on static and dynamic load capacities, ensuring optimal performance and longevity for your machinery.

Visit our website to explore our range of products and find the perfect bearing solution for your needs.

Conclusion

Understanding static load vs dynamic load in bearings is essential for choosing the right bearing for your needs.

Get your bearings at LILY Bearing, LILY Bearing offers a wide selection of high-quality industrial bearings suitable for various applications.

Our expert team can help you choose the right bearings based on static and dynamic load capacities, ensuring optimal performance and longevity for your machinery.

Visit our website to explore our range of products and find the perfect bearing solution for your needs.