Menu Call Search


(Not) Cracking Under Pressure: Unveiling Mechanical and Thermal Failures in Non-Metallic Bearings

(Not) Cracking Under Pressure: Unveiling Mechanical and Thermal Failures in Non-Metallic Bearings

(Not) Cracking Under Pressure: Unveiling Mechanical and Thermal Failures in Non-Metallic Bearings

Non-metallic self-lubricating bearing materials, including polymers like Thordon SXL and ThorPlas-Blue, are prized for their durability and minimal maintenance needs. However, to guarantee their long-term reliability, it is essential to understand their mechanical and thermal failure modes. This blog examines

Mechanical Failure Modes

Thermal stability in bearings. Impact and Fatigue Failures

Wear & Abrasion

Wear and abrasion are common failure modes where material loss occurs due to frictional forces. This is particularly critical in applications with continuous motion, such as conveyor systems or linkage connections. Over time, repeated contact with other surfaces causes the polymer bushing material to wear down, leading to increased clearances, reduced performance, and eventual failure. 

How To Reduce Wear & Abrasion

  • Material Selection: Choose polymers with high wear resistance
  • Surface Treatments: Apply surface coatings or treatments to reduce friction and wear. 
  • Proper Lubrication: Ensure that self-lubricating properties are maintained through regular checks and appropriate environmental conditions. 

Creep and Deformation Under Load

Creep occurs when a material deforms permanently under a constant load over time. Low quality plastics are particularly susceptible to creep, especially at elevated temperatures. This deformation can lead to misalignment, increased friction, and ultimately, bearing failure. 

How to Limit Creep Deformation

  • Load Management: Design bearings to operate within the material’s load limits. 
  • Material Reinforcement: Use high-strength polymers that exhibit lower creep rates. 
  • Temperature Control: Maintain operating temperatures within the material’s optimal range to reduce the rate of creep. 

Impact and Fatigue Failures

Thermal stability in bearings. Impact and Fatigue Failures

Impact failures occur due to sudden forces or shocks, while fatigue failures result from repeated stress cycles. Both types of failures can lead to cracking, chipping, or complete material breakage. 

Strategies to Minimize Impact & Fatigue Failures:

  • Material Toughness: Select materials with high impact resistance and fatigue strength. 
  • Design Considerations: Incorporate features that distribute stress evenly and avoid stress concentrations. 
  • Preventive Maintenance: Regularly inspect bearings for signs of fatigue or impact damage and replace them as needed. 

Thermal Failure Modes

Thermal Degradation

Thermal Degradation

Thermal degradation involves the breakdown of polymer chains due to high temperatures, leading to a loss of mechanical properties and eventual failure. This can be accelerated by oxidative environments or repeated thermal cycling. 

How to Limit Thermal Degradation

  • Heat-Resistant Polymers: Use materials with high thermal stability. 
  • Thermal Barriers: Implement cooling water systems to manage operating temperatures.

Thermal Expansion and Contraction

Polymers expand and contract with temperature changes. Excessive thermal expansion can cause misalignment, increased friction, and wear, while contraction can lead to loose fittings and reduced performance. 

Mitigation of Thermal Effects

  • Material Selection: Choose materials with low coefficients of thermal expansion (CTE). 
  • Design Tolerance: Design bearings with appropriate clearances to accommodate thermal expansion and contraction. 
  • Temperature Management: Maintain stable operating temperatures to minimize thermal cycling effects. 

Thermal Fatigue

Thermal fatigue occurs due to repeated heating and cooling cycles, leading to the formation of cracks and eventual material failure. This is common in applications with fluctuating temperatures. 

Reducing Thermal Fatigue Effects

  • Thermal Cycling Tests: Perform thermal cycling tests during material selection to ensure durability. 
  • High-Performance Polymers: Use polymers specifically designed for high thermal cycling resistance. 
  • Stress Relief: Design bearings to minimize thermal stresses by avoiding sharp corners and incorporating stress-relief features. 

Understanding the mechanical and thermal failure modes of non-metallic self-lubricating bearing materials is crucial for ensuring their longevity and performance. By selecting the right materials, implementing appropriate design strategies, and maintaining optimal operating conditions, these failures can be mitigated effectively. In the next part of this blog series, we will explore environmental failure modes and strategies for mitigating these issues. 

Thordon bearings SXL bearings

Stay tuned for Part 3: Surviving the Elements: Mitigating Environmental Failures in Non-Metallic Self-Lubricating Bearings