Fatigue Analysis of Mining Equipment
Why understanding fatigue is critical to the long-term reliability of mining and industrial plant.
Mining equipment operates in one of the harshest engineering environments in the world. Unlike many structures that remain relatively static throughout their service life, mining equipment is subjected to thousands—or even millions—of repeated load cycles.
While a structure may appear perfectly adequate under a single static load, repeated loading over time can lead to fatigue cracking, often with little warning.
Understanding fatigue behaviour is therefore an essential part of designing reliable mining infrastructure.
What is Fatigue?
Fatigue is the progressive weakening of a material caused by repeated loading.
Importantly, fatigue failures can occur even when the applied stresses remain well below the material's ultimate strength.
Instead of a single overload event, microscopic cracks gradually develop over time before growing into larger structural defects.
Eventually, a component may fail suddenly despite appearing to have operated normally for many years.
Why Mining Equipment is Particularly Susceptible
Mining equipment rarely experiences constant loading.
Instead, structures are continually subjected to changing forces resulting from normal operation.
Typical examples include:
Vibrating screens
Crushers
Conveyors
Pump skids
Agitators
Stackers and reclaimers
Mobile plant
Process equipment
Pipe supports subjected to vibration
Every operating cycle contributes a small amount of fatigue damage.
Over years of continuous service, these cycles can accumulate into significant structural deterioration.
Where Fatigue Cracks Commonly Occur
Fatigue cracks almost always begin at locations where stresses become concentrated.
Typical locations include:
Weld toes
Weld terminations
Bolt holes
Cut-outs
Attachment brackets
Lifting lug connections
Stiffener terminations
Sharp corners
Changes in plate thickness
Poor weld transitions
These localised stress concentrations often determine the service life of the entire structure.
It's Rarely the Main Steel Member
One of the biggest misconceptions in structural engineering is that fatigue failures occur because the primary beam is too small.
In reality, the main member often remains well within its allowable stress limits.
Instead, fatigue failures usually begin in the details:
Small attachment plates
Gussets
Welds
Connection plates
Local reinforcements
Good detailing is often more important than increasing member size.
Static Design Doesn't Tell the Whole Story
Australian Standards such as AS4100 provide an excellent framework for structural design.
However, mining structures frequently experience loading conditions that extend well beyond simple static analysis.
Engineers may also need to consider:
Repeated cyclic loading
Dynamic amplification
Vibration
Equipment start-up and shutdown
Impact loading
Resonance
Fatigue life
Understanding how these operational loads affect the structure is essential for achieving long service life.
Common Causes of Fatigue Failures
Fatigue failures are rarely caused by a single issue.
Instead, they often result from a combination of factors such as:
Poor Detailing
Abrupt changes in geometry increase local stresses.
Simple improvements to plate transitions or weld profiles can significantly improve fatigue performance.
Unexpected Operating Conditions
Equipment often operates differently from its original design assumptions.
Changes in throughput, material density or operating speeds can alter loading conditions considerably.
Modifications
Additional pipework, platforms or equipment are frequently added during the life of a plant.
Even relatively small modifications can alter load paths and introduce new stress concentrations.
Vibration
Rotating equipment may introduce cyclic loading into nearby support structures.
Without careful design, vibration can accelerate fatigue damage.
The Role of Finite Element Analysis
Finite Element Analysis (FEA) has become an invaluable tool when assessing fatigue-sensitive structures.
Rather than simply calculating average stresses, FEA allows engineers to investigate:
Local stress concentrations
Weld behaviour
Plate bending
Connection stiffness
Alternative reinforcement arrangements
Stress redistribution
Areas of peak stress
This provides valuable insight into where fatigue cracking is most likely to occur.
Designing for Long Service Life
Successful fatigue design is rarely achieved by making every component larger.
Instead, engineers seek to:
Reduce stress concentrations
Improve load paths
Optimise weld details
Minimise abrupt geometry changes
Improve stiffness where required
Eliminate unnecessary vibration
Simplify load transfer
Often, relatively small design refinements can dramatically increase fatigue life.
Inspection Remains Critical
Even well-designed equipment should be inspected throughout its operating life.
Regular inspections can identify:
Early cracking
Weld defects
Corrosion
Loose connections
Distortion
Changes in structural behaviour
Detecting fatigue damage early allows repairs to be undertaken before more significant failures develop.
Fatigue Engineering is About Understanding the Whole System
Effective fatigue analysis requires more than structural calculations.
Engineers must understand:
How the equipment operates
How loads are transferred
Fabrication methods
Weld quality
Maintenance activities
Future modifications
Operational constraints
This broader engineering perspective helps identify the root causes of fatigue rather than simply repairing the symptoms.
How Trang Imagineering Can Help
Trang Imagineering provides structural and mechanical engineering services for mining and industrial facilities throughout Australia.
Our experience includes fatigue assessment and structural analysis of:
Equipment support structures
Conveyor systems
Pump stations
Heavy fabrication
Process plant
Storage tanks
Lifting equipment
Temporary works
Mechanical infrastructure
Using a combination of engineering calculations, Finite Element Analysis (FEA) and practical fabrication knowledge, we help clients identify fatigue risks and develop solutions that improve reliability, maintainability and asset life.
Looking Beyond Compliance
Fatigue failures rarely result from a single design error. More often, they arise from the interaction of repeated loading, fabrication details, operational changes and environmental conditions over many years of service.
By considering fatigue early in the design process—and reassessing it whenever equipment is modified—operators can significantly reduce the risk of unexpected failures, improve asset reliability and extend the service life of critical mining infrastructure.