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 tension errors?

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 to use.

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.

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" bolts.

For more information, see the main SureBolt^TM navigation screen.

"Echo 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).

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 No more guessing as to which "one point" is the right point.

The FIRST whole echo method (patented DSP Technique).

Built into a 
Panasonic Toughbook

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Last Modified: September 27, 2011