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Maintenance manuels of today's civil aviation aircraft(from both Boeing(e.g.B-737) and Airbus(e.g.A320)) have special charpter to describe "standard torque value" for fasteners and connections. These values are determined by material, size, etc.
I wonder where and how these values come from. Could anyone provide me with detail about this issue? Thanks in advance.

The standardized values are related to the yield strength and elasticity of the fastner. Bolts in normal tolerance holes are effectively spring clamps (bolts in close tolerance holes can be better thought of as spring clamps + shear pins) and when you are tightening a bolt you are using a spiral wedge, the threads, to force the bolt to stretch to clamp the parts together.

You want to be able to stretch the bolt to apply as much clamping force as possible without exceeding its yield, or permanent deformation threshold. It's like stretching a spring too far, so that when unloaded, it is longer than before. You would say that the spring is ruined if that happens. Same with a bolt. If you overtorque it and exceed its yield strength, it will be a bit longer than before when loosened and will have lost some of its ultimate strength after being permanently elongated.

So the standard torque tables are limits on how much the bolt can be stretched, converted to the equivalent rotational force applied to the spiral wedge of the threads. The values are those that keep the axial tension force below the yield threshold, with some safety margin. The standard limits are a function of the material strength and elasticity of the material that a particular bolt is made from.

A lot of the time torque values are given that differ from the standard values because the designer wanted to customize the clamping force for some other purpose, such as to limit clamping force on the base material or gasket or washer, or limit shear loads on parent material threads (like a steel bolt in an aluminum casting). The normal engineering practice is to quote a torque value on the engineering drawing (and hence in the Maintenance Manual procedure) when it differs from the standard tables.

So as a general rule, when a torque value is from the standard torque tables, it's a limit for the bolt itself and is related to its tensile yield limit. When a special torque value is given, it's a limit to control force applied to something other than the bolt itself for various other reasons.

Fasteners have been standardized by the ISO. These standards cover e.g. bolt sizes, thread pitch, and material grades.

This ensures that bolts made in factory A fit nuts made in factory B, for all factories worldwide. It also ensures that when you buy a bolt, you can expect it to behave a certain way: a bolt of size X and grade Y will be capable of at least force Z.

ISO 898 defines material grades (called "property classes"):

For metric bolts strength is according ISO 898 Mechanical properties of fasteners made of carbon steel and alloy steel described by "property classes" with designations 4.6, 4.8, 5.8, 8.8, 9.8, 10.9 and 12.9.

This property class is usually embossed on the bolt head. Each property class has requirements for the amount of load a bolt can handle, etc.

The tightening torque tables are derived from these requirements: the torque in the table is typically calculated for bolts that are loaded to 75% of their tensile strength.