TestResources dogbone cutting die
Dogbone Sample Cutting Die for ASTM and
ISO standards

Dog bone tensile test samples are primarily used in tensile tests. The sample has a shoulder at each end and a gauge section in between. The shoulders are wider than the gauge section which causes a stress concentration to occur in the middle when the sample is loaded with a tensile force. This stress concentration ensures a higher probability that the sample will rupture away from the ends. When the rupture of a sample occurs in the midsection it is attributed to the material reaching its maximum tensile strength, whereas if the sample ruptures at one of the ends or in the grip itself the failure may be attributed to improper loading or a pre-existing defect in the material. Therefore, a dog bone sample is designed to ensure the highest probability that the sample will fail due to maximum tensile loading.

There are several different methods that may be used to create dog bone samples. Most of these methods fall into two categories: cutting and molding. 

To cut a sample from a sheet of material requires a cutting die manufactured with the appropriate dimensions. Depending on the hardness of the material the actual method of cutting the sample with the die may range from simply pushing it into the material like a cookie cutter into dough to stamping it with the aid of a hammer or mallet to pressing it through the material using a vice grip. All of these methods will produce a test sample with the shape and dimensions of the die cutter used.

Molding a test sample requires a slightly more complicated process and is generally more expensive than cutting test samples. The molding process requires the test sample to begin in a soft flexible state that usually means it is at a higher temperature than the testing temperature. The material is then either pressed or poured depending on its state into the mold of the desired sample shape and allowed to harden until it is deemed ready for testing. Specimens formed in this manner are usually stiffer than those created using the cutting method.

A dog bone test sample can be composed of any material that may be tested in tension, but are usually made from plastics, polymers, textile fabrics or rubber. The cutting method is used to create samples from flexible material as it is easier to push the cutter through them without cracking the sample due to their ductile nature. Metals and ceramics are generally more brittle and so are molded into test samples. A metal is heated until it liquefies and is then poured into the molded, whereas, ceramics are molded into dog bone shapes before they are cured. Follow this link to see our customizable dogbone tensile test sample cutting die