Joint Design & Load Calculations Flashcards
7 cards from real CFS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Joint Design & Load Calculations flashcards as text
The 'separation load' (Ps) in a preloaded bolted joint is the external tensile load at which:
Answer: The joint faces begin to separate (clamp load = 0)
Separation occurs when the external load reduces the compressive stress between joint members to zero, eliminating clamping force.
Using the Shigley joint diagram approach, what percentage of an external tensile load is carried by the bolt in a well-designed preloaded joint?
Answer: A small fraction determined by Kb/(Kb+Km)
The bolt takes only the fraction Kb/(Kb+Km) of the external load because the compliant clamped material absorbs most of it.
Which thread form has a 60° flank angle and is the most common in US industrial fastener applications?
Answer: Unified National (UN/UNC/UNF)
The Unified National thread with its 60° flank angle is the dominant fastener thread form in the United States for clamping applications.
In a bolted joint subjected to fatigue loading, which design change most effectively reduces the alternating stress in the bolt?
Answer: Decreasing bolt stiffness (longer grip, reduced shank diameter)
A more compliant bolt takes a smaller fraction of the alternating external load, reducing the amplitude of cyclic stress and improving fatigue life.
What does the 'k factor' (nut factor) represent in the torque-tension equation T = k × F × d?
Answer: An empirical coefficient combining all frictional and geometric effects
The nut factor k ≈ 0.1–0.2 for typical lubricated bolts is an empirical constant that lumps thread friction, under-head friction, and geometry into a single multiplier.
A fastener in a structural steel connection is said to be in 'double shear' when:
Answer: The fastener passes through three members creating two shear planes
Double shear occurs when a fastener has two shear planes (e.g., a clevis pin), effectively doubling its shear capacity compared to single shear.
What is the primary purpose of a prevailing-torque nut (e.g., nylon insert or all-metal distorted thread) in joint design?
Answer: Resist loosening due to vibration or transverse movement
Prevailing-torque nuts create a resisting torque that must be overcome during both installation and removal, preventing self-loosening under dynamic loads.