Creation of a New Generation of Testing Instruments: Part 2

Last week, we introduced a little bit of history into our blog by discussing the need to develop a testing instrument that could accurately test the new thermoplastic material of parachutes back in the 1940's .... Below, we finish the conversation by talking about the technology developed more than 50 years ago. Missed Part 1? Read it here ...

Part 2

These goals were accomplished with technology that was new at that time and primarily developed to meet other application needs. The strain gage initially invented at Caltech in 1936 was also, independently, developed at MIT in 1938. Its intended use was in the field of stress analysis and originally thought not precise enough to be used for accurate force measurement. The two research engineers working on the test machine project disproved that conjecture and developed a number of load cells with a broad range of capacities that could be used interchangeably in the test machine to achieve the necessary broad force measuring range. Another key technology was the invention of the amplidyne power drive system at GE around 1940. Its primary application was in the control of gun turrets on Navy ships. In the testing machine it enabled precise control of position of the crosshead and subsequently, constant rates of crosshead motion independent of the force being applied to the specimen. This, in combination with manually set change gears, enabled a speed range of 1000 to 1.

Finally, a chart recorder was synchronized to the crosshead position giving a measure of specimen elongation for materials of low compliance compared to the testing machine components.

All these systems used together created a new generation of material testing machines that could meet the needs of many of the new materials that would follow the introduction of nylon. When the war ended, Harold Hindman and George Burr commercialized the instrument they had developed and founded Instron Corporation in 1946. They always claimed that they grew their business “one application at a time”.

Do you find yourself faced with new testing challenges like Hindman and Burr? Leave us a comment on what you're testing.

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Creation of a New Generation of Testing Instruments

Not too long ago, Joe Amaral presented at the ASTM week on the creation of testing systems and how Instron came to be. Taking his generous synopsis, I've broken it down into 2 parts. We'd enjoy hearing from you and your first experience testing on a system.

1946 (Part 1)

The developments of test methods or instruments usually follow a need created by a new material, application, or problem with an existing material. To meet such a need, during the early 1940s a closed-loop tensile testing instrument with a wide load range was developed at MIT.

The DuPont chemical company created a research laboratory in the late 1920s to develop “artificial” materials. This effort was headed by Dr. Wallace Carothers, a chemist, who left his position at Harvard to join in the DuPont initiative. One of the first commercial products was the production of nylon in 1935. Coincidently, the US relationship with Japan, its greatest supplier of silk, had diminished in the years before WWII creating the need for a replacement fiber for this versatile natural material. Nylon was targeted to fulfill this need. Hence, material characterization had to be done to ensure it could meet some of the demanding applications for which it was intended. The most notable was the fabrication of parachutes, both the fabric and the shrouds.

The test requirements were broad. Not only was it necessary to characterize the fiber strength, but also the fiber woven structures. This new material was a thermoplastic and had properties more affected by the rate of loading during the test than most conventional materials.

During WWII, MIT was funded to do many research projects in support of the US military. The effort to do a proper evaluation of these new polymer materials was one of those projects. The goal was to build a testing instrument that had a very broad load range, a precise control of the rate of testing as the specimen was loaded and a direct measurement of sample elongation. With the anticipation of a wide commercial demand, it had to be portable enough to manufacture and deliver to laboratories around the US.

Stayed tune to learn more about how these goals were accomplished ..... Read more

Race Ahead of Strain Measurements!

In the composites community, getting accurate strain readings is especially important. To properly assess the strength and material properties of a given carbon fiber laminate, strain measurements must be done properly and accurately.

The importance of accurate strain measurements can be seen in the Formula 1 race car industry. Nowadays, F1 race car chassis are made of composite materials. This advancement began in the 1980s when the processes to manufacture automotive parts became simpler. Composite chassis proved to be stronger and much lighter than the aluminum chassis that were used before this time. To protect the driver, F1 manufacturers need to be sure of the material properties of the composite materials they use when building the car.

As Lorenzo had previously mentioned, testing composite materials can prove to be difficult when measuring strain. Measuring strain on certain specimens various standards calls for strain gauges to be bonded to each specimen. An example of utilizing technologies to measure strain on a composite laminate specimen can be seen here.

With so much info on composites and testing various composite specimens, we have began to develop a section on our site specific to composites testing solutions - feel free to check it out and let us know what else you'd like to hear about. Read more

What's the Impact on an Airplane Wing?

Imagine this: You are sitting on a plane getting ready to take off and you see a mechanic working on the wing of the plane you are in. The mechanic is making some last minute checks when he or she accidentally drops a wrench on the wing that puts a sizable dent on the surface of the wing. It's instances like this that Compression After Impact (CAI) testing is done. After performing this type of test, a composite manufacturer can fully understand the structural affects that any impact would on a given material.

Seen in this video is an CAI test in accordance to ASTM D7137/7137M. This test is used to determine the residual strength of multi-directional composite laminate plates that have been subjected to quasi-static indentation. This particular test requires a CAI Fixture that is designed in accordance to the standard.

For more on this test, read Lorenzo Majno’s blog post.

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Sometimes You Never Know Where this Job will Take You

Have you ever seen or tested on an Instron 8150 frame? Well, if not, they are huge.

While doing a repair on a 8150 frame at a customer site, our Service technicians had to go to the roof of the building to perform the service .... Yes, the roof. Why? Because during installation the frame was so large that the only way they could get it into the customer lab was to cut a hole in the roof and lower it down.

After seating the frame it still protruded through the roof. So our team had to build a make-shift roof around the top of the frame with a removable top. Some of the electronics and pneumatics are seated in the “top can” of the frame, so that's why during this service call, the roof was the place of action.

According to the Regional Service Manager, this was his first time ever having to get on a roof to work on anything. And he quoted someone as saying, “I can see Russia from here”.... that must have been one high roof.

Think you have a testing challenge for our engineers? Leave us a comment below - we're up for anything. Read more

Tennis and Composites – What’s the Connection?

Can you imagine playing tennis with a heavy wooden racquet? Well, back in the 14^th century, when the first tennis racquets were used, this is exactly what players had to use. With a limited “sweet spot” and a heavier weight overall, these racquets were cumbersome to use.

Luckily, through the years, tennis racquets have become lighter and have a larger area for contact. This revolution has been greatly influenced by the composite industry, in particular carbon fiber. Carbon fiber tows play a large role in manufacturing the lighter and easier to use tennis racquets today.

A carbon fiber tow is a bundle of thousands of small fibers and can be difficult to test. Carbon fiber tows are weaved together to create larger sheets of carbon fiber, which eventually can be molded into various components.

Watch a video of carbon fiber tow testing using one of our tensile frames with an Advanced Video Extensometer (AVE). Read more

A How-To Lesson with Dan Raynor

Watch as Dan explains how to eliminate load string compliance in a tensile test.
Leave questions for Dan below - try and stump our expert!

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