I have a question about building a tensile tester

[christyu]

For the sake of knowledge, I'd like to ask few questions.

Although not now, I'm thinking of building my own cheap tensile testing machine that isn't used for testing on ones with such heavy loads like commercial machine.

1. For the uper body, I'm just planning to start by connecting with extrusions but when buliding the machines, what materials should each parts be made out of to keep the machine stable? Could I get detailed information of why such materials should be chosen?

2. Any other things I need to consider when approaching such project?

 

[Dr.D]

Decide what maximum load you wish to be able to apply, then analyze the structure subject to that load. It must not deform plastically, and it must not fail (fracture). You will also probably want to limit the deflection, so decide what you will allow and check that also.

 

[christyu]

Decide what maximum load you wish to be able to apply, then analyze the structure subject to that load. It must not deform plastically, and it must not fail (fracture). You will also probably want to limit the deflection, so decide what you will allow and check that also.

what about material? Aluminum, steel...etc?

 

[Dr.D]

It is not possible to make a choice of materials until you specify a max load and begin to analyze. If the max load is small enough, plastic spoons might provide sufficient strength. If the max load is extremely high, you may have to really scratch to find a material that will work. The max load is an essential parameter.

Most testing machines are rated in terms of their max load. Thus a particular machine might be rated at 2 million pounds, indicating that the frame and the power system are adequate to apply that load.

Why would you want to begin with a material selection up front?

 

[RogueOne]

what range of loads? I built one using an inexpensive hydraulic press and a load cell.

 

[Dr.D]

what range of loads? I built one using an inexpensive hydraulic press and a load cell.

That would indicate that the maximum load for RogueOne's tester is whatever the hydraulics can deliver, unless of course the load cell is crushed or the frame collapses. The whole idea of design is to match strength in all the components, so that no part is undersized and no part is radically oversized and too expensive.

 

[RogueOne]

That would indicate that the maximum load for RogueOne's tester is whatever the hydraulics can deliver, unless of course the load cell is crushed or the frame collapses. The whole idea of design is to match strength in all the components, so that no part is undersized and no part is radically oversized and too expensive.

Its also important to know min/max loads so that you can correctly size your load cell and hydraulic jack. Assuming the load cell data would be digitized, you want the min/max load cell voltage to fit as closely to the ADC's min/max voltage input range as you can make it.

I don't think that the frame's size is going to be the only major factor in cost for a project like this. Whether or not you can get something off-the-shelf that will suffice for a load frame will be a major factor as well.

You can get a hydraulic press from harbor freight for $100. If your component's maximum load is far less than the cheapest hydraulic press' load frame's maximum load, would it actually be cheaper to build a smaller hydraulic press? My guess is that it would not be cheaper to custom build one.