1st Exercise Lesson Flashcards
(22 cards)
What are the pros of using bolted joints?
You can join dissimilar materials
You can disassemble faster/easier
No heat treatment required
What are the cons of using bolted joints?
Large space is required
Joint might get loose due to vibrations
Heavy solution. Multiple components are required
What are the pros of using welded joints?
It is a lighter joint
Small space is required
It doesn’t get loose
What are the cons of using welded joints?
Heated affected zone
Not all materials can be welded
It is a permanent joint
What are the classification of the joints?
Nominal Pinned
Semi - rigid
Rigid
What is the difference between these joints?
The angle of rotation depending on the applied load
What is the key characteristic of a friction joint?
The shank of the bolt is not in contact with the plate. The head and the nut and the surfaces in contact bear the whole load
What is the key characteristic of the shear joint?
The bolt shank or even the thread is in contact with the plates. The bolt is being subjected to shear stress
Note: it is better to have only the shank section in contact with the plates in order to increase the contact area
Describe the behavior of a joint subjected to tensile load
- Load Ft is transmitted through friction only. No shear
- When the friction force is overpassed, the slippage starts with a constat slope alfa
- This phase starts when the plate and bolt get in contact. The load-displacement curve will have a constant slope. The angle is the same as the one depicted on the stress-strain diagram in the elastic region.
- The plastic deformation starts. This region is not of our interest.
What are the three failure modes of a bolted joint?
Shearing failure of the bolt
Bearing failure of the plate due to plastic deformation
Tensile failure of the plate due to tearing of the plate in the minimum cross-section
Is the geometry a factor in the failure of the plate?
Yes. The main parameters are the diameter of the hole, the distance between holes center and the distance from the hole center to the edge
How the nomenclature of the bolt class works?
Class A.B.
UTS = A x 100 Mpa
YS = AB10 Mpa
Why is it preferable to use symmetric layout in joints?
For the even distribution of the applied loads in the number of bolts
What are the two different load combinations which a joint can be subjected to?
Shear and torsion
Shear and bending
What is the difference between a Low Stiffness flange and a High Stiffness flange?
The Low Stiffness one (LS) keeps the neutral axis hypothesis
The High Stiffness one (HS) rotates about the edge of the flange
What is the meaning of Ares?
Tensile stress area
What is the purpose of Ares?
The calculation of the shear stress when we have thread contact (instead of shank contact
What is the friction coefficient for an untreated surface and a sandblasted surface?
0.3 for untreated
0.45 for sandblasted
How V cero is produced?
It is a consequence of torque. When tightening, the head is held and the nut is rotated.
What is the purpose of the torque?
To balance the friction loads generated at the contact surface between the bolt head and the plate and at the (M’s) and the bolt thread and nut (M’’s)
How the total torque is obtained?
It is the sum of both M’s and M’’s torques
