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Choosing a Universal Testing Machine

vicky.nguyen's picture

I am in the process of buying a universal testing machine, and have found the process to be quite confounding.  My main area of expertise is computational mechanics, but I decided to add a materials testing capabiity to my program to support my constitutive model development efforts.  I am surprised that, given how expensive these machines are, that there's isn't a user generated comparison website or online forum relating experiences or comments regarding these machines, their software, accessories, etc....  

Perhaps iMechanica is a good place to start one.  I invite those experimental mechanician (particularly those testing soft tissues and polymers) to help me out and post comments regarding the machines you use.  Any comment would be appreciated.

 Vicky Nguyen, Assistant Prof, ME, Johns Hopkins U.

Vicky,

Once upon a time, test machines were"universal" meaning you could do a number of things with them; this is no longer an appropriate description. The plethora of test machines exist because they are tailored for a specific performance range. The selection of test machines depends on maximum force level, maximum elongation, rate of elongation, control options, resolution, etc. So, my suggestion would be to develop a range of requirements that you anticipate and then use to narrow down the options. Many experimentalists end up owning a few "test machines" so that they can cover various needs.

Post your specifications and I am sure a number of people will give their input re advantages and disadvantages of different machines.

Ravi.

Vicky,

As I know,SHPB experimental technology has been widely extend to many fileds,for example polymer, chinaware,concrete and so on.Meanwhile, we can know material's stress-strain curve under high strain rates using SHPB.so I advise you cosidering SHPB bar,while its cost is not expensive with convenienct operating.

MichelleLOyen's picture

Chris,

Which instrument are you using for this work?  How are you holding the samples?  Gripping is probably the number one issue I get asked about in the context of small-scale mechanical testing.

Back to Vicky's question... 

I suspect there is no "universal" testing machine but flexibility is key for maximum usefulness.  However, in this context I would prioritize the following:

1.  changeable load and displacement ranges and sensitivities

2.  fully programmable such that any test type could be used (including feedback/PID controller for alternative loading modes)

3.  flexibility in terms of set-up for hydration and temperature control (when soft tissues are involved)

4.  flexibility and options for gripping the samples

 

I have not yet seen a "nano" range testing instrument that fulfills my own requirements in these areas, and as such would stick with a "micro"-to-"milli" type universal testing machine based on the scaling down of a traditional UTM.  Of course, for soft tissues and soft polymers there is a need for low-loads and larger displacements, which is also not traditionally the regime for which many instruments have been optimized.    

 

Hi, Vicky. If you are interested in nanoscale testing, there might be several experimental setups as suggested by Li in above reply. We are currently using atomic force microscopy for bioassay (sensing biomolecular behavior) implying the single-molecule experiments that have been broadly employed by biophysicians. Also, microcantilever in AFM has been used as a micromechanical resonator for sensing molecules. AFM will be a well established experimental set up for nanoscale studies.

Kilho

hi Vicky ,

First i know what is your bewilderment,and how to say , i do not want to take this spam for your academe , but i think we can help you for this practical problem.

i think you need the computer controlled universal testing machine , The machine adopt dual space door type structure, in general, tension test is executed at the upper space, compression and bending test are applied at the lower space, the test space can be exchanged with customer’s preference. The loadframe is consisted of four-column, ballscrew, upper crosshead, middle crosshead and worktable, and the adjustable speed system is installed underside of the worktable. High accuracy, wide range and stable Japan Panasonic AC servo motor drive the ballscrew pair rotating through syn-deceleration system, the ballscrew pair drive middle crosshead, make the tension clamp(compression, bending) move up and down, then realize load and offload to the specimen. This structure has enough stiffness to apply high efficiency and stable moving. Key parts are processed on the processing center to ensure the accuracy of the load frame. Ballscrew is E5 class.
Standard grips: wedge tension, compression and bending clamp each one set.
if you want to more details ,give me email by equipment@timegroup.com.cn call me owlet
or another question about the using method ,no problem call us

vicky.nguyen's picture

Thank you all for your replies and inputs.    I've found for my needs that screw-driven electromechanical machines will meet the low force, large elongation, and elongation rate requirements for static testing and they are relatively inexpensive. I'm planning on purchasing a dual column machine rated for max load of 5kN-10kN but outfit it with a 1kN and smaller load cells. These machines are capable of large elongations and fair elongation rate.  And I think the dual column, aside from increased frame stiffness, will  provide more room to fit an environmental chamber and mount samples.

I  agree with Michele that versatility and flexibility is very important, especially for someone like me who has a few different interests, namely testing soft tissues, polymers, adhesion testing, but regards experiments as a complementary component to my primary modeling work.  Most machines from the bigger manufactures will allow you to buy  a variety of gripping options, and change out load cells.   So if you can afford it, get a  stiffer machine than you will initially need.    Michelle's third point about fully programmable with feedback control and ability to controll using external signals is also important.  This feature isn't always described in the brochures/specs so you'll have to ask.

 

Thao (Vicky) Nguyen
Assistant Professor
Mechanical Engineering Department
Johns Hopkins University
http://me.jhu.edu/~tnguy108

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