How do you measure and reduce friction losses in mechanical systems?

1 Measuring friction losses

To measure friction losses, you need to know the friction coefficient and the normal force between the surfaces. The friction coefficient is a dimensionless number that depends on the material properties, surface roughness, and lubrication conditions of the contact. The normal force is the perpendicular force that presses the surfaces together. The friction force is the product of the friction coefficient and the normal force. The friction power is the product of the friction force and the sliding velocity. The friction losses are the friction power divided by the input power.

2 Reducing friction losses

There are several ways to reduce friction losses in mechanical systems, such as selecting materials with low friction coefficients, improving the surface finish, using lubricants or additives, optimizing the geometry and alignment of components, and designing for lower or variable speeds. Applying coatings or treatments to modify surface properties and reducing the surface roughness can also minimize contact area and asperity interactions. These measures can reduce the friction coefficient and the wear rate, as well as the friction power and heat generation.

3 Lubrication regimes

Lubrication is a key factor in reducing friction losses in mechanical systems. Depending on the lubricant film thickness and the surface roughness, there are three main lubrication regimes: boundary, mixed, and hydrodynamic. When the lubricant film is very thin and the surface asperities are in direct contact, boundary lubrication occurs and the friction coefficient is high, depending on the surface properties and the lubricant additives. Mixed lubrication happens when the lubricant film partially supports the load and the surface asperities are in partial contact, leading to a moderate friction coefficient that depends on both the surface properties and the lubricant viscosity. Lastly, hydrodynamic lubrication is when the lubricant film is thick enough to completely separate the surfaces and support the load; this leads to a low friction coefficient that depends mainly on the lubricant viscosity and sliding velocity.

4 Lubricant selection

When selecting the right lubricant for a mechanical system, you must take into account several factors, such as the operating conditions that impact the lubricant performance and stability, the compatibility with the materials, seals, and other fluids that affect the lubricant effectiveness and durability, and the environmental impact that influence the lubricant sustainability and safety.

5 Lubricant maintenance

To ensure the lubricant quality and functionality, regular checks and actions should be taken. This includes monitoring the lubricant level, temperature, pressure, and flow to guarantee proper lubrication and cooling. Additionally, analyzing the lubricant condition, such as viscosity, acidity, contamination, and wear particles is necessary to detect any signs of degradation or damage. Lastly, it is important to replace or replenish the lubricant according to the manufacturer's recommendations or condition-based indicators in order to prevent excessive friction losses or failures.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?