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CHAPTER ONE
INTRODUCTION
The Dakota Ultrasonics model MiniMax is used to measure the stretch (elongation,
load, stress and %strain) of a fastener under tension. This is accomplished
ultrasonically by sending an ultrasonic wave down the length of the fastener and
accurately measuring the change in transit time between an unloaded versus loaded
fastener/bolt, and calculating a physical stretch. The objective for using ultrasonics,
over conventional/mechanical methods is accuracy. Most conventional methods
refer to a torque value which has limited accuracy due to the coefficient of friction.
The coefficient of friction is difficult to determine, as it depends on the control and
application of lubrication.
The MiniMax avoids the coefficient of friction entirely, using the transit time of a
wave, Hooke's law, and Young's modulus to accurately calculate the stretch on a
bolt. Since the MiniMax cannot physically stretch a bolt, both
conventional/mechanical methods and the MiniMax are complimentary and used in
conjunction.
Dakota Ultrasonics maintains a customer support resource in order to assist users
with questions or difficulties not covered in this manual. Customer support may be
reached at any of the following:
1.1 General Disclaimer
The manual should be read and understood prior to using the MiniMax. This
operating manual provides the user with all the general information necessary to use
and adjust the designed features. However, this manual is not a certified
NDT/Bolting training course, nor is it intended to be one. Training, according to
company requirements, is recommended. The responsibility for proper use of the
instrument rests solely on the user.
1.2 Safety
Using the MiniMax while standing in water or in a wet environment can result in
serious electric shock, injury, and even death.
Operating the MiniMax with damaged or inadequate cables and power source can
result in serious electric shock, injury, and even death.
Dakota Ultrasonics Corporation
1500 Green Hills Road, #107
Scotts Valley, CA 95066 USA
Telephone: (831) 431-9722
Facsimile: (831) 431-9723
www.dakotaultrasonics.com
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