Engineering Articles

Engineering

Core concepts underlying pressure vessel analysis, materials behavior, and code frameworks — essential background for engineers working in design, analysis, or inspection roles.

• Description of Finite Element Analysis (FEA) for the Non-Engineer
  FEA is a digital model of the structure and the forces it experiences – mechanical loads, temperature changes, vibration, seismic events, or internal pressure. The software divides the model into thousands of small segments – called finite elements – and solves the physics across each one, producing a precise picture of where stress concentrates, where deformation occurs, and where failure is most likely to begin.
• Introduction to Fatigue Analysis
  An overview of fatigue as a failure mechanism — how cyclic stresses initiate and propagate cracks, why fatigue accounts for the majority of mechanical failures, and how S-N curves and damage accumulation methods are used in engineering practice.
• History of Fatigue Analysis
  From early railway axle failures in the 1800s to the development of ASME fatigue design curves, this article traces how the engineering understanding of fatigue evolved — including Dr. O’Donnell’s direct contributions to the ASME B&PV Code fatigue procedures.
• Introduction to Failure Analysis
  A practical introduction to failure analysis methodology — how engineers systematically investigate why a component failed, what evidence to collect, and how findings inform design improvements and litigation support.
• Introduction to Metallurgy
  Foundational metallurgy for engineers: material microstructure, mechanical properties, heat treatment effects, and how metallurgical factors influence fatigue life, fracture behavior, and corrosion resistance in pressure vessel applications.
• Introduction to Nondestructive Testing
  An overview of NDE methods — UT, RT, MT, PT, and ET — including how each technique detects different flaw types, applicable code requirements, and how NDE integrates with fitness-for-service evaluations and in-service inspection programs.
• Background to ASME B31 Pressure Piping Code
  An introduction to the ASME B31 piping code family — covering the scope of B31.1 (Power Piping), B31.3 (Process Piping), and related sections, design by formula requirements, and how piping analysis connects to pressure vessel system design.
• Background to API 579 / ASME FFS-1
  An introduction to the API 579-1 / ASME FFS-1 fitness-for-service standard — what it covers, how it differs from original construction codes, and when FFS assessment is the appropriate engineering response to in-service damage or degradation.
  

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Pressure Vessel Design & Analysis

Technical articles on ASME code-compliant pressure vessel design and analysis — from foundational stress analysis through advanced design-by-analysis methods and fatigue evaluation per ASME Section VIII.

• Stress Analysis of Thin-Walled Pressure Vessels
  Covers the fundamental membrane stress equations for cylindrical and spherical shells under internal pressure — hoop stress, axial stress, and the assumptions underlying thin-wall theory, with worked examples applicable to ASME Section VIII Division 1 design by formula.
• Description of Finite Element Analysis
  (FEA) is a powerful computational method used to predict how structures and components respond to mechanical loads, thermal conditions, vibration, and other real-world forces. By dividing a complex structure into thousands of small elements and solving governing equations across the entire system, FEA reveals stress distributions, deformation patterns, and potential failure modes that would be impossible to quantify through hand calculations alone.
• Introduction – FEA for Pressure Vessels
  ASME Boiler & Pressure Vessel Code Section VIII Division 2 — the Design by Analysis (DBA) path — requires FEA for vessels with complex geometry, combined loading, or operating conditions that exceed the assumptions underlying the simpler Design-by-Rule formulas of Division 1.
• Basics of Pressure Vessel Design & Analysis
  A comprehensive introduction to pressure vessel design — components, loading conditions, material selection, wall thickness calculation, head configurations, and nozzle reinforcement — oriented toward ASME B&PV Code compliance.
• FEA Stress Classification and Linearization | ASME Section VIII Division 2
  Before results can be compared to code allowables, the total stress at a location must be decomposed into meaningful categories: primary membrane, primary bending, secondary, and peak.
• Design by Analysis vs. Design by Rule
  Explains the fundamental difference between ASME Section VIII Division 1 (design by rule / formula) and Division 2 (design by analysis) — when each approach is appropriate, what Division 2 requires in terms of FEA and stress classification, and how the choice affects vessel economics and code documentation.
• What is a Primary Stress?
  A focused explanation of stress classification under ASME VIII-2 — distinguishing primary membrane, primary bending, and secondary stresses, why the classification matters for code compliance, and common misclassifications that lead to non-conservative designs.
• Overview of ASME B&PV Design by Analysis
  A detailed look at the ASME design-by-analysis framework — elastic and elastic-plastic analysis methods, stress linearization, limit load and plastic collapse assessment, and the role of finite element analysis in meeting Part 5 requirements of ASME Section VIII Division 2.
  
• Understanding ASME B&PV Code Requirements
  A guide to navigating the ASME Boiler & Pressure Vessel Code — how the sections are organized, what Section VIII Divisions 1, 2, and 3 cover, how to identify applicable requirements for a given vessel, and common compliance pitfalls.
• Performing Fatigue Analysis on Pressure Vessels
  A comprehensive guide to pressure vessel fatigue evaluation per ASME Section VIII Division 2 — defining load cycles, performing FEA stress analysis, calculating equivalent stress ranges, evaluating against material fatigue curves, and applying Miner’s Rule for cumulative damage assessment.
• Common Mistakes in Pressure Vessel Analysis
  Practical guidance drawn from decades of code compliance reviews and failure investigations — the most frequently encountered errors in stress analysis, FEA modeling, fatigue evaluation, and ASME documentation that lead to non-conforming designs or missed failure modes.
• Introduction to ASME Code Design Approval
  Explains the ASME design approval process — what the Manufacturer’s Design Report must contain, the role of the Authorized Inspector, U-stamp certification requirements, and how design-by-analysis documentation differs from design-by-rule submittals.
  

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Fitness-for-Service & Failure Analysis

Articles covering in-service assessment, remaining-life evaluation, and the investigation of mechanical failures — topics where OCE’s combination of ASME code expertise and forensic engineering experience is most directly applied.

• Introduction to Fracture Mechanics
  Covers the fundamentals of linear elastic fracture mechanics (LEFM) — stress intensity factors, fracture toughness (K_IC), crack growth under cyclic loading, and how fracture mechanics principles are applied in fitness-for-service assessments per API 579-1 / ASME FFS-1 Part 9.
• Introduction to Fatigue Analysis
  Fatigue is the leading cause of equipment failures. This article introduces the mechanisms of fatigue crack initiation and propagation, cycle counting methods, and the fatigue life concepts that underpin both new vessel design and fitness-for-service remaining-life assessments.
• Introduction to API 579 / ASME FFS-1 Fitness-for-Service
  A practical introduction to the FFS standard — the Level 1, 2, and 3 assessment framework, damage mechanisms addressed (corrosion, cracking, creep, fire damage), how remaining life is calculated, and when FFS evaluation allows continued safe operation of equipment that would otherwise require retirement or repair.

 

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Have a Pressure Vessel Engineering Challenge?

OCE’s engineers bring decades of hands-on experience in ASME code compliance, finite element analysis, fatigue evaluation, and fitness-for-service assessment to every project. If you’re working through design issues, in-service damage assessment, or a failure investigation, we are available to discuss it.

Call Tom O’Donnell, PE: (412) 835-5007

Email: info@odonnellconsulting.com