Myth busted: Not all cracks behave the same way

Debunking one of the costliest misconceptions in structural asset management

When managing critical steel infrastructure like port cranes, bridges, or production equipment, there is a persistent belief that once you understand how one crack behaves, you've seen them all. This assumption costs operators time, money, and sometimes even safety.

The reality? Crack behavior is far more complex than most realize.

The misconception

"All cracks in similar locations propagate at similar rates, so if we've monitored one, we know what to expect from others."

This logic seems reasonable. After all, if you're working with the same steel grade, similar loading conditions, and comparable stress points, shouldn't cracks behave predictably? Not quite.

Why this belief is wrong

Crack propagation depends on multiple interacting factors that vary significantly even within the same structure:

1. Loading patterns differ

Two seemingly identical welds on the same crane can experience vastly different stress cycles. One might face constant, predictable loads while another endures irregular stress spikes. Research published in Materials journal (2022) demonstrates that an increase in load ratio leads to an increase in fatigue crack growth rate with crack growth rates varying significantly depending on load frequency, amplitude, and sequence.

2. Material variations matter

Even within certified steel grades, microstructural differences at the weld zone create varying resistance to crack growth. Research on heat-affected zones shows that different microstructures within the same weld can exhibit dramatically different crack propagation thresholds and growth rates. Factors like residual stresses from welding, heat-affected zones, and material discontinuities mean that identical-looking cracks can propagate at completely different rates.

3. Environmental conditions play a role

Environmental conditions play a critical role in crack behavior. Corrosion, temperature cycles, and moisture exposure can create unpredictable crack growth patterns—for example, a crack in a sheltered location might remain stable for years, while an identical crack exposed to harsh environmental conditions could propagate rapidly. Research on stress corrosion cracking indicates that salt deposition significantly increases cracking density and accelerates corrosion in steel structures.

4. Crack geometry influences behavior

The Paris Law, a fundamental principle in fracture mechanics developed in the 1960s, shows that crack growth rate depends heavily on crack length and geometry. Small variations in initial crack size or shape lead to dramatically different propagation timelines.

The real-world impact

At steel production facilities, engineers have discovered that monitoring crack behavior on one crane doesn't guarantee similar behavior across their fleet. In one case, two cranes with similar cracks required completely different interventions—one remained stable for 18 months, while another required emergency repair within three months.

The assumption that "all cracks behave the same" leads to:

• Over-maintenance of stable cracks

• Under-monitoring of fast-growing cracks

• Inefficient inspection schedules based on assumptions rather than data

• Difficulty justifying major investments or safely deferring repairs

  
  

How continuous monitoring changes the game

Rather than treating all cracks as identical threats, continuous monitoring with systems like Villari's wireless sensors provides real-time insight into actual crack behavior for each specific location.

By monitoring fatigue-critical locations in real-time, operators gain insight into:

• Actual propagation rates for each specific crack, not generalized assumptions

• Early warning signals when crack behavior deviates from expected patterns

• Confidence to defer repairs on slow-growing cracks while prioritizing urgent ones

• Data to justify decisions about repairs, replacements, or continued operation

Villari's wireless crack detection system monitors structural behavior at key fatigue-sensitive locations continuously, without disrupting operations. This approach moves teams away from assumption-based maintenance toward condition-based decision-making grounded in real data.

Conclusion

Each crack exhibits unique propagation behavior—and assuming uniformity can compromise both safety and operational efficiency.

Ready to move from assumptions to data-driven decisions about your critical assets? Let's discuss how continuous monitoring can give you the visibility you need!