FEC AFC1200 - Manual (Page 13)

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6.1.3.2 Area Yield Method
The Area Yield Method will be the primary controlling method on fasteners that do not have a
clearly definable yield point. These fasteners will exhibit a gradual change in torque rate as
the fastener is elongated. This calculation of the elongation area (EA) allows the System to
simulate the fastener as if it had displayed a clearly defined yield point. When the actual
elongation area (EA) is equal to or greater than the calculated/simulated elongation area the
proper bolt stretch (LENGTH) has been obtained.
SCREW PITCH
LENGTH
ANGLE
YIELD RATE
CONSTANT
A
B
AREA "EA"
A
B
AREA "EA"
ELGA
=
ELGA
ANGLE ANGLE
ACTUAL EQUIVALENT (SIMULATED)
THE FASTENING PROCESS
WILL STOP WHEN:
EA
2
A x B
ELGA
>
TORQUE TORQUE
= ELONGATION A NGLE
1ST
TORQUE / ANGLE
PRESET ITEMS
CONSTANT
AREA YIELD
METHOD START POINT
FIG. 6-1-3-2 Yield Control Function for Area Yield Method
w Area Yield Method Fastening
P After presetting the fastening sequence (Section 7.5 SET SEQUENCE) to perform
the desired number of steps, the System fastening parameters (Section 7.1
PARAMETER SET) must be configured according to the Engineered fastening
specification.
P Multiple-step fastening will be performed according to the Torque and Angle
Control Method procedures. Area Yield Control will begin when the fasteners attain
either CROSSOVER AREA torque, or (Threshold 2 torque + Crossover Area
angle). No incremental steps may be performed which will occur after the
commencement of the Area Yield Control (CROSSOVER AREA). It is therefore
highly recommended that Yield Control operations be restricted to no more than
two steps.
Chapter 6: Fastening Instructions
Page 6-13