Shear Stress Measurement for Bolt

Hi, you have 3 possible solutions.

In both solutions the bolt has to be equipped with strain gages so that the strains can be measured and the loads which are applied.

The first solution is to use sliding contacts -rotary- so that the contact between the bridge and supply and acquisition can be maintained during rotation.

This approach allows a continuous supply of the bridge so that your measurements are not limited in time.

The second solution is to use a module for the acquisition supply with batteries which rotates and transmits wireless the signals to a stationary receiver.

The 3rd solution is to use a module as well with a battery supply but which is able to save the obtained data in a RAM and transfer them to a PC for instance after the tests. Since there is no wireless transmission the power used is less so that the test time could be longer.

Of course the prices are different so that the solution depends on the budget you can obtain. 1st is the less expensive. For the sliding contacts depending on the signal and on the accuracy you need you can either use usual sliding contacts metal to metal or contacts with mercury (mercotact) with a lower noise level.

thanks for your valuable suggestions.the rotary equipment is big enough and i want to measure the stress at different positons.So i will prefer a non contact option.ofcourse the budget will go high.i am looking for staring the data in a ram.Can you suggest any kind of ram(usb storage device) that i can use.basically what kind of data does this ram store? If you can suggest any such storage device brand,i must look or contact for detail function in web.Once again thanks for your reply.

1- any data logger with a high enough acquisition frequency which pends on the dynamics of the investigated system will do the job. You should consider that the device band pass should be 3x to 5x the highest frequency which could load the system.

2-I cannot suggest any source as long as i do not know where you are, under which conditions the device will work (environment) and how long the tests have to be.

3- If you have several bolts to analyse on same structure it is possible to use a data logger and a scanner to get the signals from several bolts one at a time and record them in the data base.

Hi,

i am in us.i would like to use your option for collecting the data there it self in the rotary equipment.Can i use any kind of usb storage device for data collection?Pl let me know if some kind of such storage device you can suggest.

thanks

What sort of RPM and physical sizes are you talking about?

rpm will be of 300 and size will be 30 to 40 ft

To whom it may concern,

As an alternate solution to an actual test perhaps a CAD program with FEA analysis, such as Pro-Engineer wildfire can make the prediction you are looking for very accurately. The shear strength of a bolt is generally known and listed by the manufacturer of the bolt as it is a function of the grade of steel used to manufacture that bolt and the manufacturing processing methods ie. hardening / stress relieving etc. A sample drawing in 3D can likely be created of your assembly in a few hours, the constraints and loads are applied, and a simulation is run. Your answers should then be just a part of a print out.

Mirco.

It is very dangerous to base all on simulations since the results depend on the given assumed inputs. As you say loads are to be introduced but what do you do when the load is unknown and it has to be determined? How can you do it by CAD?

It was said the structure was large 30-40ft?, it would seem more dangerous for something to fly apart then to anticipate the loads and use CAD, measuring shear implies failure of the bolt. Loads can be introduced very accurately as anticipated until failure. Finite element analysis and the knowledge of the material type of the bolt. An Engineer with Finite Element Analysis capability can predict this failure, a strain gauge is good until failure, and seems a good solution if this experiment can be done safely. After failure all other variable loads need to be tested again? Maybe we need some more explanation of what this device is actually to do.

Mirco

I do not know since when you use simulation techniques, i do it since more than 30 years and what i can say is that only the users who do NOT believe blindly in the results are successful.

Of course soft has improved and i work with very modern programmes but never the less a simulation is based on assumptions which could be wrong and ONLY a measurement can determine the RIGHT value of a load. It is not necessary to go to destruction it is enough to make measurements at lower loading and with the results validate the model and go by simulation to the destruction limit on the model without any danger or money loss. In some cases this economical approach is NOT possible and the test has to be brought to the limit in the real world.

Ok in the case of having to take an actual measurement, check out http://omega.com/

They have a lot available and also take mail orders, for strain and test gauges. Some strain gauges can simply be glued on and wired up to an encoder or voltmeter, which can then be related to the application.

Best of luck.

Mirco.