Life Prediction & Fitness for Service

From coronary stents to aircraft engines, ship hulls to buried pipelines, steam turbines to microelectronics, the design, maintenance, or life extension of most engineered structures involves some form of life prediction or fitness-for-service (FFS) evaluation. Virtually all engineered structures suffer from some type of time-dependent degradation that can limit their useful life. In many instances, multiple mechanisms can act to limit the safe life of components and structures. Exponent engineers and scientists quantitatively analyze the effects of numerous damage mechanisms such as fatigue, creep, wear, and corrosion on the structural integrity and serviceability of mechanical components to develop life predictions and assess compliance with applicable codes. Whether for assessment of new designs, life extension of existing equipment, or evaluation of damaged components, Exponent maintains cutting-edge analysis tools and expertise needed to perform reliable life predictions and fitness-for-service evaluations.

Exponent engineers and scientists have developed both deterministic and probabilistic life simulation programs to help clients establish appropriate damage control programs for new designs and life extension of existing hardware. Exponent routinely applies state-of-the-art life prediction analysis techniques to assist clients developing or maintaining assets and products. The NASCRAC™ Software is one such tool developed by Exponent engineers to calculate crack propagation life for fatigue, creep, and stress-corrosion cracking mechanisms. Reliable life prediction is critical in establishing appropriate re-inspection intervals for life-limited components. A high degree of reliability can often be achieved by designing a re-inspection interval that provides for multiple inspections within the time necessary for damage to progress from a detectable level to a critical level. Exponent aids clients in developing and improving programs for integrity management and for safe operation of systems that comply with industry best practices and standards of care.

Fitness-for-service evaluation typically refers to condition assessment and future life prediction for existing structures or components in which some type of damage has been identified through in-service inspection. While fitness-for-service evaluation methodologies have been published in standards and recommended practices such as British Standard BS 7910 and American Petroleum Institute (API) Recommended Practice RP 579, application of such methodologies can be challenging. Exponent engineers have extensive experience applying these and other evaluation techniques for determining the serviceability of damaged components.

Services


  • Medical devices assessments - fatigue, corrosion
  • Steam turbines assessments - fatigue, creep crack growth, corrosion, temper embrittlement, foreign object damage (FOD) 
  • High-temperature piping assessments - creep, creep crack growth, corrosion  
  • Transmission pipelines assessments - fatigue crack initiation and growth, stress-corrosion cracking (SCC), general corrosion, impact damage  
  • Boiler and Pressure Vessel assessments – fatigue, corrosion, SCC 
  • Offshore structures assessments - fatigue, corrosion  
  • Electronic component assessments - thermal and mechanical fatigue
  • Aircraft airframes assessments -  fatigue, corrosion, impact damage  
  • Compliance review with applicable design or in-service standards and regulations
  • Review of operations and integrity management programs (IMP)
  • Development of inspection programs and establishing re-inspection intervals
  • Root cause analysis of failures
  • Failure mode and effects analysis (FMEA)
  • Expert witnesses
  • Modeling and simulation of damaged structure behavior using techniques such as Finite Element Analysis (FEA)
  • Nondestructive evaluation (NDE) and structural health monitoring
  • Defect sizing and tolerancing

Professionals

Knowledge