Younger readers may be surprised to hear that the word plastic was once synonymous with cheap. Maybe that’s why Dustin Hoffman’s character was famously given the career advice to get into plastics in the movie “The Graduate.” It was, as they say in some quality circles, a target rich environment. Today, however, the quality of plastics and other materials are advancing at a rapid pace. Materials are becoming stronger, harder, lighter, and in many cases less expensive. The method of manufacture is also rapidly changing. Three-dimensional (3D) printing has become a viable option in many applications, and not just for plastics. The cost of 3D printing of metals, while still prohibitive in many cases, has been falling steadily. As materials and manufacturing methods advance, characterization and quality are as important as ever. Manufacturers have many reasons to pursue designs which are smaller, lighter, less expensive, and with less environmental impact. At the same time, customers’ expectations relentlessly increase.
One of the main tools in the quality toolbox is tensile testing. In tensile testing, a sample is subjected to a pull force. The test objectives vary from application to application, and can include measuring the breaking force, the force at a pre-defined elongation, elongation at break, as well as some scientific calculations, such as Young’s modulus. Test results can inform the designer or quality control engineer whether the material or sample has been designed and manufactured appropriately. But, as with any testing, the data is only as good as the test methodology allows.