The Testing Times

These grips are used to test seat belts and webbing up to 100mm thick. seat belts have interesting properties, they have to cushion the shock of a crash without injuring the passenger of the car at low speed stops. In a collision it has a precise elastic limit, meaning that it stretching slightly to diffuse the shock, goes beyond its elastic limit, becomes plastic then holding it's passenger without breaking, there is a great deal of force involved in this process (which is why these grips are rated to 100 kN ...) The testing can be quite explosive as the belt stores a great deal of energy before failing. By exerting a tensile force on the belt it is possible to see how it will behave. One of the important features of this grip is that it is self tightening. The specimen is feed through the grips in a specific manner as not to damage the belt. A damaged belt can dramatically affect its ability to protect the passenger, and once it has been stretched to it's elastic limit and ...

This grip is designed to meet the very strict guidelines set within the ASTM D143 standard. I have mentioned this standard before, it is one of the most demanding standards available for wood specimens. One of the most important tests when it comes to the structure of wood is how it reacts in tension. As wood can be very strong in tension it's is necessary to 'profile' the sample (cut the wood into a specific shape) so that the region undergoing test is uniform, in the middle and weaker than the grip or piece of wood the grip is holding onto. It also needs to be smaller to allow an extensometer to be added to measure the small changes in the length of the sample. This grip is essentially self-aligning, the sample slotting into the two fingers.

Articulated 4 Point Bend Test for Ceramic Samples. Used for testing the smallest ceramic samples 1.5mm x 2.0mm x 20mm. The test calls for articulated anvils that are free to move as the sample deforms. The problem is how to hold the anvils in place before loading the sample. The answer is it’s all done by magnets. The anvil is attracted towards the end of the bar magnet. The magnets are positioned so that the anvil will return to the start position as soon as load is removed. In case you loose the odd one, we supply a bag of spares!

A flexural test tells the tester how much force a specimen can withstand in the middle when supported at a distance (or its flexibility!). This test supports the specimen between two loose fitting ‘rollers’, the distance apart of which can be set for a specific test or specimen size. Once the sample is in place the anvil can be brought down just above the specimen. A variety of tests can then be performed. The specimen can be flexed a certain number of times to judge it’s elasticity or plasticity over a given time. The specimen could be flexed until it breaks, it could be flexed for a specific time and the responding force measured. This is a Heavy Duty system, which has been designed to suite the U-Series 100 kN System . It has a travel of 400mm from centre (800mm overall) and Ø10mm rollers. This can all be recorded in the software and multiple specimens can be tested.

Sylvia Hillier, the Textiles expert here at Tinius Olsen has her own blog, she is very knowledgable and a really nice person to boot! If you've got any textile related issues go here! http://www.testingtextiles.com/sylviablog.php

Some of the more destructive tests that our systems are designed to perform can be quite violent, the forces and materials used can have some explosive results. It is often important to guard the rest of the room or the user from flying shrapnel. We produce guards for these reasons, as the U-Series is over 2 metres tall and a large footprint; the U-Series needs to have a huge guard. We made the guard a close rectangular fit around the system; it is free standing although there are some mounting points to attach it to the system. aluminium section and composite sheet make the frame up, which is a very strong (and heavy) structure. It has two wrap around doors and polycarbonate windows that allow the user to see and control the test. For safety the control unit and an emergency stop have been placed on the right hand door. I can safely say that this is verging on architecture, rather than engineering!

Imagine trying to hold a piece of fibre insulation (the stuff in your roof that stops the heat escaping) in a clamp and then pulling it apart using a tensile test, how on earth do you do it? It’s fibrous, comes in different thicknesses, breaks of easily into chunks… Well the answer is Nails, and lots of them. This is the most effective way to distribute the load across and through this particular sample, this means that the test specimen isn’t overly damaged when you grip it. If the sample is ‘waisted’ properly (like an hour glass), it will break in the weakest spot, not by the grip. This is a technique used time and again with all kinds of samples. You want to see how the material will break under load, not how the grip breaks it, and then the load pull it apart. As there are a lot of nails it’s quite hard to push them through the top surface of the specimen (Imagine trying to nail 20 nails at once into something soft. It might be soft but there is a lot of friction to overcome). To ...

The Standard ASTM D143 outlines several methods for testing wood. As a building material it is essential to understand the structural integrity of timber this is what ASTM D143 is designed to find out… This is a heavy duty application (wood is an interesting substance in compressing and the jaws can get ‘gummed-up’ with the wood sap) and so for this particular application a Tinius Olsen H75KS system is used. The S0971 is designed to perform one of the tests in the ASTM D143 stable. It shears the wood between two vertically offset, horizontally parallel faces. This system uses a self adjusting blade to shear the sample against another supporting blade that is offset 3mm from the main cutting face. This distance can be adjusted using a simple shim. This simple modification could allow for future testing in these standards... ASTM D 143-94, ASTM D 905-98, ISO 6238 2001, JIS K 6802-1973, JIS Z 2117-1977, BS 373: 1957 and JAS 601-1974 testing standards. Features: This system uses a qui...

The Tinius Olsen S0616 is used to hold a standard syringe for testing fittings. It makes use of the end of the syringe, whilst holding it in place. The plunger cannot be used whilst in this grip; this is a method of testing the end fittings not the syringe. There are a variety of fittings that attach to a standard syringe, the most common of which is a standard Luer fitting. We do a few grips to hold Luer fittings, but it’s sometimes just as easy to hold the syringe and use that as the ‘grip’ end. The materials are correct, syringes are cheap, and it’s a real world test. If there is any damage to the syringe it can be easily replaced…

From the same stable as the S0984 this grip uses similar materials but holds the specimen in a different way. Designed to meet GOST23785 it is designed around the drawings given in the standards. The cord is wrapped around the Spiral Ebonite Bollards and held in place with a simple screw grip… This effectively distributes the load over a wider area on the cord. This means that delicate or multi-strand samples can be tested. One of the main problems with testing cord is the grips can create weak points in the sample if it pinches or nips the sample. This results in the test being void or can give misleading results. This grip is designed to avoid this... It has a 5/8" Nosepiece which means that it would fit on one of the smaller systems.

At first sight, one of less intricate but useful tests is compression tests. This is basically applying a force (measured in Newton’s) to the sample and measuring the effect the force has. There are a wide range of tools for doing this but in general platens are used to hold the sample and apply the force. Platens are large flat surfaces that can be used to compress a sample… The S0404 platens are big, very big. They fit on the 100 kN U-series Systems (they can apply a force of 100 kN to an object) Tinius Olsen produce… These behemoth platens are 350mm x 350mm and 35mm thick plough ground plate. I’m a big chap and I can’t lift one on my own… A brute force approach, but the feedback received through the Loadcell and Compressometer is very precise and can show how much force a sample can take and spring back or fail. The results gleaned from these tests can tell a great deal about the product under test, the 'intelligence' comes in the form of the Software, which can be use...

S0844 Tinius Olsen GOST 23785-1 Cord Grips The Russian Standards are called GOST , and we've recently had a few of these come through the doors. This grip is designed to meet the GOST 23785-1, they are designed for testing cord. Interestingly the GOST standard calls for Vulcanite to be used as the grip faces, a difficult material to machine but can be used to great affect. This grip simply holds the sample in a vice grip after being wrapped around the testing face. ГОСТ 23785.1-2001

Used on some of our smaller systems, the S0981 Tinius Olsen ASTM C736-00 Adhesion Test For Latex Sealants, quite a recent one, this grip design is used to test the strength of sealants and adhesives used in the production of windows. It's quite a complex process to prepare the samples, using a c shaped 'mold' the sealant is injected between a glass and aluminium plate. These are held together using (good ol ') G-clamps. It is then allowed to cure for a specific time... as it's nice to prepare a few of these samples to test, we provided a few kits (C section, and the aluminium and glass plates). It was odd, as you had to remember that the test specimen was a liquid that needed to cure, in a mold. I was something that I had to keep reminding myself. This test allows you to find the Adhesion strength of the Sealant between the desired structural material types. In this case glass and aluminium.

The 4 souls and I in the Design Department thought that the wider world might be a little interested in the projects that we engineer and the interesting and varied products that Tinius Olsen produces... There is plenty of time at lunchtimes to do this... and it's a healthy reminder of the projects we've done in the past...