Operating Manual

Chapter 8: BoltMike Formulas
Guide to Ultrasonic Inspection of Fasteners Page 27
Chapter 8: BoltMike Formulas
The BoltMike uses the following collection of formulas
as a basis for all calculations and derived values. If us-
ing the formulas manually, be certain to convert all val-
ues to the units listed below, and to adhere to accepted
rounding practices and number of significant digits. Fi-
nally, keep in mind that all BoltMike calculations are per-
formed in metric units. When English units are displayed,
the conversion from metric to English takes place after
values are calculated.
Units
Temperature: Degrees C
Thermal Coefficient (Cp): 1 / Degrees C
Time of Flight (TOF): s (Seconds)
Acoustic Velocity (Vo): m/s (Meters per sec.)
All values of length: m (Meters)
Modulus of Elasticity (Eo): Pa (Pascal)
Stress Factor (K): m/s/Pa (meters per
second per Pascal)
Yield Strength (Y): Pa (Pascal)
Uncorrected Stress: Pa (Pascal)
Corrected Stress: Pa (Pascal)
Stress Offset: Pa (Pascal)
Cross-Sectional Area: m
2
(Square meters)
Load: kN (KiloNewton)
NOTE: The units of measurement listed above are
those units used in the following equations. These are
not in all cases the same units that are displayed by
the instrument, nor are they necessarily the same units
as listed in tables throughout this guide.
Measured Time of Flight (TOF)
TOF measured = Sound Path Duration
2
Reference Length (LREF)
LREF = TOF
measured
* V
Temperature Normalization
TOF
normal
= TOF
measured
* [1 + (Cp * Temp
measured
– 22.22 )]
Change in Ultrasonic Length
Change in Ultrasonic Length =
(V * TOF
normal-stressed
) – (V * TOF
normal-reference
)
Stress Calculation and Correction
Stress
uncorrected
=
V * (Change in Ultrasonic Length)
K (Change in Ultrasonic Length + Effective Length)
Stress
corrected
=
Stress
uncorrected
* (1 + Stress Ratio) + Stress Offset
100
Load
Load = Stress
corrected
* Cross-Sectional Area
Elongation
Elongation = Stress
corrected
* Effective Length
Eo



