[L1] 1 High-Strength Bolt Fastening and Tightening Methods [L2] 1) High-Strength Bolt Fastening [L4] - A fastening method that uses the tensile force generated by tightening high-strength bolts and the friction occurring between the joined materials. [L4] - High-strength bolts have high tensile strength and are used for securing aggregate sections, among other applications. [L4] - There is no noise during construction, and fewer restrictions on the working environment. [L4] - Compared to welding, it requires less skill during work and offers higher productivity. [L2] 2) Fastening Methods [L3] ① Classification by Bolt Deformation Type [L4] - Elastic Region Tightening [L4] - Plastic Region Tightening [L3] ② Classification by Bolt Tightening Method [L4] - Torque Method (torque control method) [L4] - Angle Method (angle control method) [L1] 2 Tightening Methods [L2] 1) Torque Method (Elastic Region Tightening) [L4] - A tightening method that utilizes the linear relationship between tightening torque and clamping force. [L4] - A method of applying a specified torque using a torque wrench or nut runner. [L4] - Applied when aiming to maintain uniform tightening quality. [L4] - Work by referring to the bolt manufacturer's torque chart. Generally, the clamping force is around 60-70% of the yield point. [L5] * Generally, a friction coefficient of 0.12 is assumed and applied. [L4] - Clamping force scatter varies depending on thread dimensional accuracy, surface roughness of the mating part, and lubrication status. [L2] 2) Yield Region Tightening (Plastic Region Tightening) [L4] - Applied when aiming to achieve maximum axial force by tightening just before the yield point. [L4] - Approximately 80% of the yield strength. [L4] - Requires a higher degree of control compared to Elastic Region Tightening. Highly reliable equipment must be used. [L4] - Bolt selection criteria for plastic region application: [L5] a. Select bolts made of materials with low scatter in the yield point. [L5] b. Select products where the slope of the elastic region graph leading to the yield point is small, resulting in a larger tightening angle up to the yield point. [L5] c. Select products where the angle to reach maximum axial force from the yield point is large (those with high elongation). [L5] d. Use full-thread bolts. [L2] 3) Angle Method (torque angle method) [L4] - A method where the bolt is tightened until its head is fully seated against the fastening surface (snug point), and then further tightened by a specified angle. [L4] - Applicable to both elastic region tightening and plastic region tightening. [L5] a. Elastic Region Tightening: Can reduce clamping force scatter by ensuring a consistent amount of deformation. [L5] b. Plastic Region Tightening: Can achieve high clamping force. [L4] - Tools used: Rotation angle detection - Angle division scale plate (protractor). [L2] 4) Torque Gradient Method (or yield controlled tightening) [L4] - A method where torque and angle are measured during tightening to ensure the clamping force remains between the proportional limit and the yield point. [L4] - Offers excellent reliability and clamping force, but high-cost equipment is used to maintain high quality. [L4] - Applied in the assembly of automobile engine cylinder heads. [L2] 5) Other Tightening Methods [L4] - Elongation measurement method: A method of tightening while measuring the bolt's deformation (strain). [L4] - Loading method: Tightening is performed while a specified tensile load is applied to the bolt. [L4] - Heating method: A method of tightening by heating the bolt to expand its length.