Bolted Joints Flashcards
(12 cards)
A screw is defined as an externally threaded headless fastener, where one end mates with a tapped component and the other with a standard nut
False
This describes a stud. A screw has either pre-formed or self-made internal threads.
Bolted joints are primarily used for permanent connections between components
False
Bolted joints are listed as a type of non-permanent joint, alongside screws, threaded and unthreaded fasteners, and setscrews.
Rivets are a type of threaded fastener commonly used in aircraft structures
False
Rivets are non-threaded fasteners. While rivets remain an important method of assembly for aircraft structures, they are specifically noted as non-threaded.
In the mechanical model of a pre-tensioned bolted joint, the resultant load on the bolt in tension decreases as the external load increases
False
The resultant load on the bolt in tension is given by the formula πΉπ = πΎπ / (πΎπ + πΎπ) * π + πΉπ. As the external load P increases, the term (πΎπ / (πΎπ + πΎπ) * π) increases, causing the resultant load on the bolt (Fb) to increase.
For a bolted joint, joint failure or separation occurs when the component in compression carries a positive resultant force
False
Joint failure or separation happens when the component in compression carries a zero or negative resultant force (πΉπ = πΎπ / (πΎπ + πΎπ) * π β πΉπ β€ 0). Too much external load P causes the joint to separate.
The derivation of the formula for calculating bolt stiffness (Kb) when there is an unthreaded portion is based on the concept of equivalent stiffness of springs in series
True
The derivation of the formula for Kb (πΎπ = π΄ππ΄π / (π΄πππ‘ + π΄π*ππ)) with an unthreaded portion is explicitly stated as being based on the concept of Equivalent Stiffness of springs in series.
Reducing bolt stiffness can be achieved by using long bolts or tie rods to make a βhardβ joint
True
A longer bolt is less stiff (Kb decreases). A βhardβ joint is one where the clamped members are very stiff compared to the bolt (Kc»_space; Kb). Using a longer, less stiff bolt (lower Kb) while keeping the clamped members the same (constant Kc) increases the ratio Kc/Kb, making the joint βharderβ. So, reducing bolt stiffness does make the joint βharderβ relative to the boltβs stiffness.
A reserve factor (n0) for a pre-tensioned bolted joint should typically be in the range of 1.5 to 2.0
True
Pre-tensioning a bolted joint increases the fluctuating stresses in the bolt under cyclic loading
False
Pre-tensioning is stated as the reason that it reduces the fluctuating stresses in the bolt, which is beneficial for cyclic loading.
For proper function of an βOβ ring, an interface fit is required with one of the mating parts
True
βOβ ring compression set is caused by permanent distortion due to an error made in the installation of the βOβ ring
False
While installation errors can cause damage, compression set is a specific failure mode related to permanent deformation over time under compression and temperature, not solely installation errors.
A radial lip seal can be used to provide a good level of sealing for a rotatory machine under low and high temperature conditions
True
