Week 2: Shear stress and torsion Flashcards
What is the expression for shear stress?
Book 1 page 26
What is the main disadvantage of a single-shear lap joint?
Introduces bending stress under load and can lead to peeling of the two parts of the joint
Book 1 page 28
What is the mechanism which causes bending stresses in single-shear lap joints?
Vertical offset between the tensile forces
Book 1 page 29
What types of force are present in a bolted joint?
- Bolt is in tension
- Joined plates are in compression
Book 1 page 33
Why does ignoring friction in bolted and riveted joints introduce a factor of safety?
Friction acts against the applied loads which cause shear stress, thus reducing the effect of the loading
By ignoring friction we are discounting the positive effects it has on that loading and preparing for the worst case scenario
Book 1 page 34
How does the shear force act differently between a bonded joint and a mechanically fastened joint?
Riveted and bolted joints - Shear force acts in the cross-sectional area of the fastener
Bonded joint - Shear force acts in the cross-sectional area of the adhesive
Book 1 page 35
What is the expression which relates shear stress (τ) to shear strain (γ)?
Book 1 page 38
Why is the shear stress in a transmission shaft under torque considered to be pure shear?
Because there are only shear stresses as a result of applied torque, and no normal stresses
Book 1 page 42
What is the right-hand screw rule as it pertains to torque?
If an axle is held in the right hand, and the fingers curl around in the direction of the applied force, then the thumb is oriented in the positive torque direction
Book 1 page 42
What is the angle θ used for in relation to torque on shafts which undergo deformation?
Angle of twist measured in radians
One end of a shaft has rotated relative to the other by the angle
Book 1 page 45
What is the angle γ used for in relation to torque on shafts which undergo deformation?
Angle between a line which had previously been parallel to the shaft’s axis under no load, but which has now rotated by this angle
Measured in radians
Shear strain and is defined as the angular deformation due to an applied torque
Book 1 page 45
What is the expression which relates shear strain and angle of twist in a shaft under torque?
Book 1 page 45
What is the expression which relates shear stress in terms of angle of twist and what does this tell us about the variation of shear stress within the component?
Shear stress varies linearly with radial position over the cross-section of the bar
Book 1 page 47
Describe in words the difference between polar coordinates and cartesian coordinates?
Polar defines the position of a point using a radius and an angle instead of two orthogonal axes x and y
Book 1 page 48
What is the expression which relates torsion in a circular shaft to torque, polar second moment of area, shear stress, radius of a shaft, shear modulus, angle of twist and length of the shaft and what should be noted about the polar second moment of area for different shafts?
The polar second moment of area for different shafts expression is different for:- thin-walled tubes, thick-walled tubes and solid cylinders
Book 1 page 53
What expressions are used for maximum stress in a shaft and power transmitted by a shaft?
Book 1 page 55
