Civil engineering and bolt
tension Over 50 web pages on
torque, tension, & bolted joints.
engineering often teaches a civil engineer to design bolted joints by calculating bolt
tension, not bolt torque. Civil engineers may need to measure these bolt tension errors.
There is a new technology to more reliably measure tension,
not just torque. Also, see web's best bolted joint
Update says: " SureBolt outperformed the one-point bolt gauges
on every bolt and every test in reliability and accuracy."
Many civil engineering classes include bolted joint
design. As a refresher, here are some facts, and links, a civil engineer (or
civil engineering lab) would find useful:
1. What causes many bolt failures. What does civil engineering say the number one
reason for bolt
failures is? A lack of proper pre-load tension. How
many factors are involved in pre-load
2. Bolt tension is not bolt torque.
Tension not torque. You want to put a known amount of tension
into your nut and bolt combination, not just a known amount of torque. Your
structural analysis often relies on proper pre-load tension.
3. Measure Tension errors. How can a
civil engineer measure torque wrench errors?
Do these bolt tension errors matter? These errors often
affect a civil engineer's structural analysis.
4. Bolt gauge. Your joint's stress analysis
can be verified using a bolt gauge (or gage). What is an ultrasonic bolt gage? See an animated demonstration of
an ultrasonic echo inside of a bolt. Civil engineering labs
rarely have enough resources to let each civil engineer learn ultrasonics.
Are bolt gages reliable? Are they easy to use? New
patented technology has finally made ultrasonic bolt gages reliable and easy
5. Friction. Civil engineers know
that bolt and nut friction consume over 80% of the torque measurement.
But, how does the actual tension vary bolt to bolt?
What if you use the same type of bolt? This may affect a civil engineer's structural analysis.
6. Stress, strain & yield. A stress strain curve can be plotted using SureBolt. Stress strain
and yield. SureBolt can help a structural engineer verify
his bolted joint
design. Did his bolt reach yield?
7. Flanges. Flange joints sometimes leak. Why does the tension in a flange bolt
vary so much, bolt to bolt? How can you tighten each flange bolt to closer tolerances?
How can you use SureBolt on a flange?
8. SureBolt. How does SureBolt differ from any other ultrasonic bolt
gauge? What is the difference between a one-point bolt gage and SureBolt's
patented whole echo method? Are the prices similar? (Yes)
9. Civil Engineers. Some engineers use a strain gauge to measure bolt tension because
they know a torque wrench is not directly measuring tension.
Yet their structural analysis software may assume a limited amount
of error (+- 25%) when calculating bolt tension from bolt torque.
10. Tension errors. What are some of the tension errors associated with using a torque
wrench? Does your stress analysis software let you enter the
tension error ranges?
11. Civil engineering. This site is a
civil engineering resource for torque versus
tension in bolted joints.
SureBolt is a nondestructive testing - NDT - method of measuring bolt tension.
Non destructive testing includes the use of ultrasonics.
SureBolt's Whole Echo
patented technology greatly increases reliability by using the whole echo
instead of just one point. All other bolt gages use just "One
Point" (one zero crossing), that leaves you susceptible to peak
jumping (20% or more error). Surebolt is a more reliable bolt gage due to
a new patented technology. See comparison table.
Bolt gages have been around for over 20
years. Their "Peak Jumping"
problems have kept them from being widely used. When your bolted joint
fails or flange leaks, then you find out your bolt gage may have
With a lot of training and laboratory testing, NASA has used bolt
gages for years. NASA physically takes Polaroid pictures of the echoes
before and after tensioning. Then they use their trained human
experience to determine if the echo has distorted
"too-much". Even after all
this, they have to throw away approximately one third of the ET
measurements because they are not reliable. When NASA used the
SureBolt prototype, no measurements had to be thrown away.
SureBolt gives you a 13.3" TFT, portable PC
(Panasonic Toughbook Model 72). The ultrasonic pulser and digitizer are built into the CD ROM
and PCMCIA slots. Click here to see
the actual SureBolt screens. See the animated DEMO page
to see how an ultrasonic bolt gage can measure tension. SureBolt has been used
on special high strength titanium bolts to standard "off the shelf"
Time". See animation below of how to ultrasonically
measure the change in bolt tension using echo time.
This animation requires FLASH
(version 4 or higher).
FAST-DAQ Let us know how we can help you.
1022 Antelope Trail, Winter Springs, FL 32708, USA
Send your email to
comments about how we can help. Contact us here,
or type in the email address shown above (Due to spam, we have replaced the text
email address, with the image email address shown above).
Note: Privacy. We will NOT give your contact information to
No more guessing as to
which "one point" is the right point.
The FIRST whole
echo method (patented DSP Technique).
Built into a
Visitors Since 1-22-02
September 27, 2011