Dakota MAX II, Operation Manual

Page: 135 / 216

127
CHAPTER TWELVE
MEASUREMENT & WAVEFORM DISPLAY
12.1 Quantities of Measurement
The MAX II has the ability to measure in a number of measurement quantities: Time
(nanoseconds), Elongation, Load, Stress, and Strain (in terms of %). While there are
a number of quantity options available, the easiest and most fail safe quantities to
consider are Time and Elongation
. If Load, Stress, or Strain will be used on a regular
basis, a calibration of the bolts for the specific application is required.
The equations below outline the required factors and constants necessary for each
quantity. When measuring in terms of time and elongation, very little information is
required, as the measurement is simply a difference equation. The stress factor and
velocity will typically not vary more than 5%, in total, over the entire range of possible
steel fasteners. Therefore the worst case error is 5%. However, when measuring in
terms of load, stress, or strain, the error can be enormous if errors in effective length,
load factor, or cross sectional area are made. These factors will result in proportional
errors overall. Therefore, if the load factor is off by 10%, the load measurement will
be in error by the same 10% proportionally.
  
 
T V S X
F E
 
0
Elongation
X
E
= Elongation
S
F
= Sonic Stress Factor
V
0
= Material Velocity

T = Change in time.
  
o F E
L L X P
 
Load
P = Load
X
E
= Elongation
L
F
=
Load Factor
L
O
= Load Offset







A
P
S
Stress
S = Stress
P = Load
A =
Cross sectional error
100








E
E
N
L
X
S
%Strain
S
N
= %Strain
X
E
= Elongation
L
E
=
Effective Length