Embedded Systems Conference
Breaking News
Comments
Newest First | Oldest First | Threaded View
ROV ENG
User Rank
Author
Instrumented Fasteners
ROV ENG   12/1/2013 11:15:13 AM
NO RATINGS
It's not difficult to put a strain gauge into the center of fasteners as small as 1/4" in diameter, we were doing this in the early 80's using proprietary techniques. The sensors were sealed inside the fastener and were suitable for use underwater. The two issues that limited widespread use were the cost and the reduction in strength of the fastener for smaller sizes. This only works for bolted fasteners unless you have a very well defined parting line between the two joined structural elements, which is where the sensor must be located. Accuracies of 0.1% were routinely achieved. Most customers were not so interested in measuring the tension in the fastener during installation, although that was useful information, they were more interested in measuring forces during operation of the machine.

Per ASME B18.2.1, a bolt is designed to be inserted through a hole and secured with a nut, while a screw is designed to be used in a threaded hole—sometimes along with a nut.

RJHonders
User Rank
Author
Re: reliability?
RJHonders   11/29/2013 4:59:44 PM
NO RATINGS
CookieJar, you hit the nail on the head. Hard to put sensors in small screws and get the signals out.

vapats
User Rank
Author
Re: torque
vapats   11/28/2013 8:39:39 PM
NO RATINGS
Torque is not a proper measure of screw/bolt tension;  you must measure the actual elongation (stretch) of the fastener.


Torque is a mere (and often highly inaccurate) approximation.

 

prabhakar_deosthali
User Rank
Author
Re:
prabhakar_deosthali   11/28/2013 6:50:02 AM
NO RATINGS
To ascertain that the screws are not overstressed while tightening them,  one can use the torque screw drivers where you can set the maximum torque that will be applied to the screw while it is tightened.

That will eliminated the possibility of the built-in sensor getting damaged by the screw tightening action.

vvc0
User Rank
Author
Re: reliability?
vvc0   11/27/2013 6:07:51 PM
NO RATINGS
Hmmm, many bolts don't have nuts, such as lag bolts (self tapping), and head bolts (inserted into a tapped hole in an engine head), to name a couple. Also, screws can have nuts, such as machine screws, and even sheet metal screws with tinnerman nuts. The differentiation is more based on the diameter than the fact it is used with/without a nut, but even this is somewhat nebulous.

Stephen_M
User Rank
Author
Re: reliability?
Stephen_M   11/27/2013 2:35:11 PM
NO RATINGS
A bolt is used with a nut to hold things together. A screw can be used without a nut; ex: sheet metal and wood screws, self tapping, self drilling screws.

cookiejar
User Rank
Author
reliability?
cookiejar   11/27/2013 12:48:47 PM
I assume the idea is to locate a load cell in the tip of a screw to measure force. 

Having worked with load cells, I found the major design challenge using load cells was to keep them from being overloaded and going into plastic deformation.  Just the thought of a applying a tightening torque to a screw makes me cringe as that would twist the delicate load cell structure.  If you build in a mechanism to stop rotation between the two ends of the load cell, the stop friction will affect your readings. 

Trying to do all this in the extremely limited room at the end of a screw would be a challenge as I've always thought of screws being less than 1/4" in diameter and bolts being 1/4" and larger.  But I suppose that may have been lost in translation.




Radio
LATEST ARCHIVED BROADCAST
As data rates begin to move beyond 25 Gbps channels, new problems arise. Getting to 50 Gbps channels might not be possible with the traditional NRZ (2-level) signaling. PAM4 lets data rates double with only a small increase in channel bandwidth by sending two bits per symbol. But, it brings new measurement and analysis problems. Signal integrity sage Ransom Stephens will explain how PAM4 differs from NRZ and what to expect in design, measurement, and signal analysis.

Datasheets.com Parts Search

185 million searchable parts
(please enter a part number or hit search to begin)
Most Recent Comments
HardwIntr
 
IJD
 
MWagner_MA
 
txicos
 
imadur
 
andybe
 
Bruzzer
 
Bruzzer
 
CB_EE
Like Us on Facebook
Special Video Section
The LTC®6363 is a low power, low noise, fully differential ...
Vincent Ching, applications engineer at Avago Technologies, ...
The LT®6375 is a unity-gain difference amplifier which ...
The LTC®4015 is a complete synchronous buck controller/ ...
10:35
The LTC®2983 measures a wide variety of temperature sensors ...
The LTC®3886 is a dual PolyPhase DC/DC synchronous ...
The LTC®2348-18 is an 18-bit, low noise 8-channel ...
The LT®3042 is a high performance low dropout linear ...
Chwan-Jye Foo (C.J Foo), product marketing manager for ...
The LT®3752/LT3752-1 are current mode PWM controllers ...
LED lighting is an important feature in today’s and future ...
Active balancing of series connected battery stacks exists ...
After a four-year absence, Infineon returns to Mobile World ...
A laptop’s 65-watt adapter can be made 6 times smaller and ...
An industry network should have device and data security at ...
The LTC2975 is a four-channel PMBus Power System Manager ...
In this video, a new high speed CMOS output comparator ...
The LT8640 is a 42V, 5A synchronous step-down regulator ...
The LTC2000 high-speed DAC has low noise and excellent ...
How do you protect the load and ensure output continues to ...