Mechead.com Forum - Recent Posts

Answer to: Converting Force Measurement to Pressure

özgün — Thu, 22 Dec 2022 19:30:48 +0000

Suppose you have a belt under tension T wrapped around a rigid cylinder of radius R. Let P be the normal force per unit area exerted by the cylinder on the belt. A force balance on the region of the belt between angular locations θ and θ+dθ gives PRdθw=Tdθ where w is the width of the belt from this it follows that P=TRw

RE: True and engineering stress

taasnikya — Mon, 19 Dec 2022 12:30:23 +0000

Hi,
In theoretically, we consider the section of the tensile sample does not change against increased strain values. However, in reality, it is obvious that the sample's section is going to be reduced because it is elongating.

I agree plus I would say during the tensile test, the width and thickness shrink as the length of the test sample increases. Although these dimensional changes are not considered in determining engineering stress, they are of primary importance when determining true stress. At any load, the true stress is the load divided by the cross-sectional area at that instant.

You can maybe check the Holloman calculation.

RE: True and engineering stress

nevofam — Mon, 19 Dec 2022 08:11:32 +0000

Converting Force Measurement to Pressure

huion_4156 — Thu, 15 Dec 2022 12:15:48 +0000

A zip-tie like structure squeezes an elastic part. I can measure a force that is related to the squeezing pressure. I need to create a calibrator that would allow me to correlate the force to the squeezing pressure. I have a zip-tie like structure, which when pulled, squeezes an elastic part. Think of it like a having a zip-tie around your finger. I can measure a force that is related to the squeezing pressure. This relationship between force and pressure is quite linear. I would now need to create a calibrator that would enable me to correlate between the measured force (N) to the pressure (Pa) that is imposed to the elastic part. The diameter of the zip-tie is about 22mm and it squeezes to about 17mm diameter. Now, I first started to think that I would have some inflatable balloon with fixed pressure. The zip tie wouldn't move when the pressures match. I would prefer to keep this calibrator relatively simple at first stage, so any crazy, easily built ideas are welcome ;-).

Acoustic vibrations for musical instruments?

johngriter — Thu, 15 Dec 2022 12:12:31 +0000

Hi,
I am looking for examples of acoustic vibration simulations for musical instruments. Particularly, I would like to do some geometrical optimisation for a guitar case.

RE: Recommendation for helical gear contact

johngriter — Thu, 15 Dec 2022 12:09:34 +0000

what type of gear you want to model? you can solidworks maybe its easier

True and engineering stress

johngriter — Thu, 15 Dec 2022 12:08:40 +0000

I am a student in mechanical engineering and we graph a stress strain curve. I know what these values are and I even know how to calculate it given the engineering stress and strain, but I just don't understand why it is necessary in the first place to calculate the true stress and strain. Can anyone help?

RE: Stress or Stain life method in fatigue analysis

özgün — Thu, 15 Dec 2022 12:06:25 +0000

Hi,
What about these articles, I guess it would be useful to understand the difference between stress and strain life.

https://www.mechead.com/understanding-of-fatigue-life-theories/

https://www.mechead.com/choose-your-side-stress-or-strain/

https://www.mechead.com/ansys-workbench-fatigue-module/

RE: Stress or Stain life method in fatigue analysis

johngriter — Thu, 15 Dec 2022 12:03:05 +0000

Fatigue problems are relatively complicated compared to static analysis. First, you may want to start to understand whether your experiment can be done with standard fatigue tests. If not you would need to focus on a special-purpose fatigue test configuration.

Probably in the special purpose test configuration, you aim will be to replicate real boundary conditions and loading conditions.

If it is a full-scale test you won't have any problem finding out the test force, ,it will be the exactly the same with the reality
But it is a small scale, you should integrate actual loading parameters into your small scale by keeping your real boundaries.

RE: Recommendation for helical gear contact

özgün — Thu, 15 Dec 2022 11:56:00 +0000

It depends what sort of analysis you would like to do. If you want to simulate a single contact between the gears, I would choose static structural.

As for the contact types, to make it more realistic you would definitely need a frictional contact (ps this is one of the hardest in terms of setting up and solution) . If you are new in Ansys workbench maybe starting with nonfrictional contact. You can check the contact type article for more information.

https://www.mechead.com/contact-types-and-behaviours-in-ansys/

Hope these help