During the visual inspection, the metallurgist views the material under increasing magnifications to look for stress or fatigued related evidence such as plastic deformation, tearing, brittleness and necking. Necking is found in ductile metals or flexible metals where an extreme stress has been applied.
Material failure investigations, including analysis of excessive stress and fatigue, have helped CED properly determine whether material failure is a contributing factor or the main cause of an accident.
Twitter Facebook LinkedIn. June 14, About CED Marketing. FATco6 Discuss the typical appearance of a fatigue failure surface in a metallic component and explain how the source of the fatigue failure is commonly identified.
FATco7 Discuss the observed relationship between endurance limit and static tensile strength for steels and explain why this relationship does not hold for welded steels. FATco13 Discuss the effects of corrosion on fatigue life and highlight how this is typically handled in relevant standards and codes of practice.
FATco14 Discuss the term Fatigue Strength Reduction Factor in relation to stress concentrations and explain how this has traditionally been handled in relevant design standards and codes of practice.
FATco15 Discuss the concept of cumulative damage and explain how this is commonly handled. FATco16 Explain why a multiaxial stress field can complicate an analysis and discuss approaches to handling this. FATco17 Discuss the significance of the choice of equivalent stress used in the fatigue assessment of welded joints FATco18 Outline a conservative approach to situations where the directions of principal stresses vary during a stress cycle.
FATco21 Discuss why weld toe grinding can be beneficial and explain how a design standards and codes of practice will typically allow for this improvement. FATco25 Reflect on why fatigue is such a long-standing and persistent cause of failure. FATco26 Discuss the nature of and typical locations for, stress singularities in a finite element model and explain how they would typically be handled in a fatigue analysis. FATco30 Explain Neuber's Rule and its limitations and why corrections to the elastic strain range from an elastic analysis may be necessary.
FATco33 Explain why corrections for mean strain are often unnecessary for low cycle fatigue. FATco35 Discuss the term endurance limit for many non-ferrous metals, steels in a corrosive environment and the possible effects of load sequencing.
FATco37 Reflect on how variable amplitude load sequencing can affect the prediction of damage accumulation and fatigue life. FATap1 Employ a fatigue diagram, consisting of Modified Goodman and Langer lines, to assess fatigue performance of components.
FATap6 Employ a finite element analysis system for the fatigue analysis of a component or structure. FATsy1 Prepare a fatigue analysis specification, highlighting any assumptions relating to geometry, loads, boundary conditions and material properties. FATsy2 Plan a fatigue analysis, specifying necessary resources and timescale. FATsy3 Prepare quality assurance procedures for fatigue analysis activities within an organisation. FATev1 Assess the significance of neglecting any feature or detail in any idealisation being used for fatigue assessment.
FATev2 Assess the fatigue significance of simplifying geometry, material models, loads or boundary conditions. BMPSap2 Employ appropriate techniques to retrieve hot-spot and other stress quantities for the assessment of welds.
MASco8 Explain, in metallurgical terms, how fatigue cracks form and grow in metallic materials. MASco11 Discuss the terms elastic-perfectly plastic, kinematic hardening, isotropic hardening, Bauschinger effect, hysteresis loop. MASco19 Discuss common material characteristics and typical manufacturing related flaws in welding. MASco20 Discuss common material characteristics and typical manufacturing related flaws in hot and cold rolled plate and tubes.
MASco21 Discuss common material characteristics and typical manufacturing related flaws in forgings. MASco22 Discuss common material characteristics and typical manufacturing related flaws in castings.
MASap2 Determine whether any allowance needs to be made to the material data for the effects of environment and variability.
Five-Session Online Training Course 2. Sketch a sinusoidal stress variation and show the maximum stress, minimum stress, mean stress, alternating stress or stress amplitude , stress range and stress ratio.
Discuss the statistical nature of fatigue and explain how this is handled in relevant design standards and codes of practice. Discuss the salient features of an S-N diagram for steels and explain the terms endurance limit, infinite life and low cycle fatigue. Discuss the typical appearance of a fatigue failure surface in a metallic component and explain how the source of the fatigue failure is commonly identified.
Discuss the observed relationship between endurance limit and static tensile strength for steels and explain why this relationship does not hold for welded steels. Discuss the effects of corrosion on fatigue life and highlight how this is typically handled in relevant standards and codes of practice. Discuss the term Fatigue Strength Reduction Factor in relation to stress concentrations and explain how this has traditionally been handled in relevant design standards and codes of practice.
Such cracks can originate in many ways. For example, they may be introduced as cracks or as incipient cracks during manufacture of structural parts; they may grow from defects in the parent metal, from incomplete welds, from shrink cracks or other imperfections in weldments; or they may nucleate and grow in structure under fatigue loading. It is the role of fracture mechanics to determine when these cracks become critical, that is, when they will reach a size at which the crack will grow catastrophically at an operational stress well below the yield strength.
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