Seminar

1. Part I: Cyclic Loading and Fatigue of Engineering Materials & Structures – Introduction

a) The Dangerous Nature of Fatigue Deterioration of Materials and Structures
– The local character of fatigue failure,
– The progressive nature of fatigue damage,
– Factors influencing fatigue life,

b) Material Aspects – Resistance against Fatigue and Fracture
– Typical types of material failure,
– Fracture surface - macroscopic features,
– Fracture surface - microscopic features,
– Relations between fracture surface appearance, material properties and loading,

c) The Acquisition and Analysis Methods of Variable Amplitude Cyclic Loading/Stress Processes/Histories
– Loading in fatigue,
– Definitions (parameters characterizing loads and stresses in fatigue),
– Rainflow cycle counting method and its numerical representation,
– Presentation of representative loading/stress data for fatigue analyses,
– Assembling representative stress histories (database for service stress histories)

2. Part II: Overview of Contemporary Fatigue Analysis Methods – S-N, e-N and da/dN-DK methods

a) The Fatigue S-N method (Nominal Stress Approach)
– The principles of the S-N approach (the nominal stress method)
– The stress parameter used in the S-N fatigue analysis
– Fatigue material properties, S-N curves (the Wohler curve)

Fatigue damage accumulation
– Hypotheses
– Mean stress effect
– Physical interpretations

Significance of geometry (notches) and stress analysis in fatigue evaluations of engineering structures
– Stress concentration versus notch factor
– Welded structures

Fatigue life predictions in the design process
– Safety factor
– Probabilistic interpretation of fatigue data
– The use of fatigue software
– The aim and necessity of fatigue experiments

b) The local stress - strain approach to fatigue analysis (the e-N method)

Notch stress-strain approach to fatigue analysis
– The foundations of the ε-N approach
– The significance of notches and localised plastic yielding

Stress-strain behaviour of materials under cyclic loading
– Cyclic stress-strain properties (σ-ε), their significance and methods of determination,
– Material memory and cyclic loading,
– Rainflow counted cycles vs. material stress-strain response

Fatigue strain-life (eD-N) Properties;
–The Manson-Coffin strain-life curve, its significance and methods of determination

Fatigue damage accumulation
– The low cycle fatigue vs. high cycle fatigue,
– Mean stress effects (Morrow’s and SWT damage parameters)

Determination of the local notch tip strains and stresses
– Geometry effect (notches),
– Neuber's rule,
– Equivalent strain energy density concept (ESED),
– Plane stress vs. plane strain and the effect of the constraint,
– The necessity and the role of the Finite Element stress analysis method,
– Residual stress effect

Fatigue due to variable amplitude loading histories
– Calculation of the local notch-tip strain and stresses due to a variable amplitude loading
– The loading sequence effect
– Fatigue damage accumulation

c) Fracture mechanics and fatigue; the fatigue crack growth analysis

Basics of Linear Fracture Mechanics
– Stress state near the crack tip in linear elastic media,
– Classical crack-tip stress-strain solution;
– The stress intensity factor parameter K

Strength criteria in Fracture Mechanics
– Critical strain energy release rate G,
– Fracture toughness KIC,
– Determination of the critical crack size

Practical use of Stress Intensity Factor expressions
– Semi-elliptical surface crack and edge cracks in welded connections

Determination of Stress Intensity Factors
– General form of stress intensity factor expressions,
– Stress intensity factor handbooks,
– Superposition of stress intensity factors,
– Weight function method,
– Numerical methods,
– Experimental method
– Residual stress effect on the stress intensity factor

Fatigue Crack Growth Analysis
– Fatigue properties used in fracture mechanics
– Fatigue crack growth expressions
– Paris' law, Forman's law, etc.

3. Part III: Practical Remedies for Improvement of Fatigue Strength and Durability and Summary
– decrease of the stress concentration factor,
– decrease of the nominal stress and residual stress,
– material selection

4. Summary - Software tools (commercial and websites)

Presenter

Dr. Grzegorz Glinka - Mechanical and Mechatronics Engineering Professor - Univeristy of Waterloo

Dr. Glinka has been with the University of Waterloo since 1989. He has also lectured at the University of Metz, France and at the University College London, England. He holds a PhD and DSc from the Warsaw University of Technology. Dr. Glinka is a specialist in fracture and fatigue of steel structures. As well, he has acted as a United Nations expert. His research interests include fracture of materials, fatigue of structures, multiaxial fatigue and creep of engineering materials, computer aided design, and FEM-elastic-plastic stress-strain analysis. Dr. Glinka has published over 100 articles in technical journals and textbooks.

What Previous Participants have said about this Seminar:

• "The instructor was excellent. He was well prepared, relaxed,...fully capable of answering all questions."
• "Very clear presentation and he was very knowledgeable."
• "I appreciated his practical approach to subject matter. All information was valuable."

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