Damage Forms of Fastener Bolt Threads and Criteria for Determining Continued Use
Q1: What are the common damage forms of fastener bolt threads?
A1: Mainly including crest wear, profile deformation, thread slipping, corrosion pits, local chipping, bending deformation, etc. Among them, thread slipping and severe corrosion are the most dangerous.
Q2: Can slightly worn threads continue to be used?
A2: Slight wear of a single thread, basically complete profile, and normal torque reaching the design value can be used temporarily, but the inspection cycle needs to be shortened with key monitoring.
Q3: What kind of damage requires immediate bolt replacement?
A3: Thread slipping of 2 or more consecutive threads, profile defect exceeding 1/3, dense severe corrosion pits, thread bending or obvious deformation must be replaced immediately.
Q4: What impact does thread damage have on preload retention capacity?
A4: Damage reduces the engagement area, causes uneven stress, decreases preload retention capacity, is easy to loose under vibration, and even fails instantly after tightening.
Q5: How to quickly judge whether the thread status is qualified on site?
A5: Visually inspect the profile integrity; test fit with nuts to feel the smoothness of screwing; check for corrosion, deformation and thread slipping; judge the fastening reliability combined with torque detection.