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The direct tension indicators shall conform to required chemical composition, compression load, and dimensional values." [5] Like other fastener components, DTIs are covered by the Fastener Quality Act of 1999 in section 3: Definitions (6), [6] where a DTI is described as "a load-indicating washer, that is through-hardened".
These bolts, usually tension control bolts or compressible washer tension indicating type bolts, are tensioned to a minimum required amount to generate large enough friction forces between the faying surfaces such that the shear (or tension) load is transferred by the structural members and not by the bolts (in shear) and the connection plates ...
A plain washer and a spring washer are placed on a bolt between the nut (on the threaded end) and the bolt head. The American National Standards Institute (ANSI) provides standards for general use flat washers. Type A is a series of steel washers at broad tolerances, where precision is not critical.
Multiple techniques exist for preload control to ensure that the tension in the bolt is close to the one specified in the design (some bolt-to-bolt statistical variations are inevitable): [1] torque-controlled tightening is a simple and most popular approach: the fastener is tightened until the torque limit is reached.
These practices are not a means of obtaining or maintaining torque, rather a safety device to prevent the disengagement of screws, nuts, bolts, snap rings, oil caps, drain cocks, valves, and parts. Three basic methods are used in safetying; safety-wire, cotter pins, and self-locking nuts. Retainer washers and pal nuts are also sometimes used. [2]
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1. Bolts, screws and studs with specified property classes – Coarse thread and fine pitch thread [2] 2. Nuts with specified proof load values – Coarse thread [3] 3. Flat washers with specified property classes [4] 5. Set screws and similar threaded fasteners not under tensile stresses [5] [6] 6.
ASTM A490 and ASTM A490M are ASTM International standards for heavy hex structural bolts made from alloy steel.The imperial standard is officially titled Standard Specification for Structural Bolts, Alloy Steel, Heat Treated, 150 ksi Minimum Tensile Strength, while the metric standard (M) is titled Standard Specification for High-Strength Steel Bolts, Classes 10.9 and 10.9.3, for Structural ...