What is buckling instability or simply buckling?
A slender structural member (generally termed strut) undergoes a large sideways deflection when the applied load reaches a critical value that is much lower than the compressive strength of the strut material
Book 1 page 120
What are the four basic modes of failure?
- Excessive elastic deformation or deflection
- Buckling instability
- Plastic deformation
- Fracture
Book 1 page 121
What three factors is the response of a component to stress dependent on?
- Type of loading
- Type of material
- Environmental conditions
Book 1 page 122
What are the most common reasons for instability in a long and slender structural member?
- The load may not be applied exactly along the longitudinal axis of the member
- The member may not be perfectly straight
- The material properties of the member vary across its cross-section
Book 1 page 125
About which axis will a strut tend to bend under a compressive load?
About the axis for which the second moment of area of the cross-section is a minimum
Book 1 page 126
What is second moment of area, I?
Geometrical expression that provides a measure of the effectiveness of the particular geometry of a beam to resist bending
Book 1 page 126
What is the expression commonly used to predict the critical load for buckling?
Euler formula
Book 1 page 130
Why is a factor K introduced into the Euler equation to give a general expression for the buckling of struts?
To cover cases where the end conditions are other than those assumed in the analysis
Book 1 page 133
What is the generalised Euler formula?
Book 1 page 134
What argument is made to justify the use of maximum shear stress to predict yielding?
Many failures in uniaxial tensile testing occur at approximately 45° to the direction of loading which corresponds to the plane of maximum shear stress
Book 1 page 136
What expression is used to give maximum shear stress in 3 dimensions?
Book 1 page 137
How can the following expression be described in words?
Under any stress state, yield failure will occur if the difference between the maximum and minimum principal stresses is equal to the measured uniaxial yield stress for the particular material
Book 1 page 137
What is the Von Mises yield criterion expression?
Book 1 page 139r
What is the expression used to summarise the effect of a stress raiser?
Book 1 page 143
How can stress raisers be avoided?
By smoothly varying cross-sections, avoiding notches and sharp internal corners (including holes)
Book 1 page 142
What are the characteristics of brittle fracture?
No visual trace of plasticity on the broken surfaces of the specimen
Load-deflection trace is linear until the fracture
Book 1 page 148
What is one of the major issues in fracture mechanics as it pertains to brittle fracture?
A specimen that fails in a ductile manner in a small section can fail in a fast, brittle fashion in larger sections
Book 1 page 148
What is the expression used in the Linear Elastic Fracture Mechanics equation and describe the terms?
Also where a is the length of the crack or one-half the length of an embedded crack
Book 1 page 155
When is LEFM deemed to be applicable?
The size of the plastically deformed zone at the crack tip is sufficiently small compared to the crack length?
Book 1 page 156
Which expression is used to calculate the critical crack length at fracture?
Book 1 page 160
What is plastic collapse?
When the reduced cross-sectional area caused by a crack means the component reaches its yield stress and collapses by plastic deformation at this reduced area
Book 1 page 161
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Week 1: Introduction8
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Week 2: Shear stress and torsion20
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Week 3: Complex stress20
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Week 4: Failure21
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Week 5: Pressure vessels19
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Week 6: Application of stress analysis to aircraft wing structures10
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Week 8: Kinematic analysis of motion5
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Week 9: Momentum, forces and impulse12
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Week 10: Rotation and plane motion11
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Week 11: Waves and sinusoids11
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Week 12: Resonance and chaotic motion8
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Week 14 - Characteristic engineering environments24
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Week 15 - Fatigue and creep36
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Week 16 - Corrosion of metals24
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Week 17 - Resisting plasticity28
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Week 18 - Making the most of materials (and microstructures)16
