What is the influence of sample shape on a tensile test?

Hey there! As a supplier of Tensile Testers, I've seen firsthand how the shape of a sample can have a huge impact on the results of a tensile test. In this blog, I'm gonna break down why sample shape matters and how it can affect your testing process.

First off, let's talk about what a tensile test is. Simply put, it's a way to measure how much force a material can withstand before it breaks. You take a sample of the material, put it in a tensile tester, and then pull on it until it snaps. The machine records the amount of force applied and how much the sample stretches, giving you valuable data about the material's strength and ductility.

But here's the thing: the shape of the sample can really mess with these results. Different shapes can distribute stress in different ways, which means you might get different numbers even if you're testing the same material. Let's take a closer look at some common sample shapes and how they can affect a tensile test.

Rectangular Samples

Rectangular samples are probably the most common shape used in tensile testing. They're easy to make and can give you a pretty good idea of a material's overall strength. However, the shape can cause some issues. For example, if the sample is too wide or too thick, it might not break in the middle where you want it to. Instead, it could break at the edges or corners, which can give you inaccurate results.

Another problem with rectangular samples is that they can have stress concentrations at the corners. When you pull on the sample, the stress gets concentrated in these areas, which can cause the material to fail prematurely. To avoid this, you can round the corners of the sample or use a special grip that distributes the stress more evenly.

Dog-Bone Samples

Dog-bone samples are designed to address some of the issues with rectangular samples. They have a narrow section in the middle where the stress is concentrated, which helps ensure that the sample breaks in the right place. This makes the results more accurate and reliable.

The shape of the dog-bone sample also helps to reduce stress concentrations at the edges and corners. By tapering the ends of the sample, the stress is distributed more evenly, which can prevent premature failure. Dog-bone samples are commonly used in materials testing because they provide a more consistent and accurate measure of a material's strength.

Circular Samples

Circular samples are often used for testing materials like wires and cables. The circular shape helps to distribute the stress evenly around the circumference of the sample, which can give you a more accurate measure of the material's strength. However, circular samples can be more difficult to prepare and test than rectangular or dog-bone samples.

One issue with circular samples is that they can be prone to slipping in the grips of the tensile tester. To prevent this, you might need to use a special grip or apply a coating to the surface of the sample to increase the friction. Circular samples also require a different testing setup than rectangular or dog-bone samples, which can add to the complexity and cost of the testing process.

Button Samples

Button samples are used for testing the strength of buttons and other small fasteners. These samples are typically round or oval in shape and are designed to mimic the way the button is used in real life. Button Tensile Tester is specifically designed to test these types of samples.

The shape of the button sample can have a significant impact on the test results. For example, if the button is too thick or too thin, it might not break in the way that it would in real life. The size and shape of the hole in the button can also affect the results, as it can change the way the stress is distributed.

Terminal Samples

Terminal samples are used for testing the strength of electrical terminals and connectors. These samples are typically small and have a complex shape, which can make them challenging to test. Terminal Force Tester is designed to handle these types of samples.

The shape of the terminal sample can affect the test results in several ways. For example, the shape of the contact area can change the way the stress is distributed, which can affect the strength of the connection. The size and shape of the terminal can also affect the results, as larger terminals might be able to withstand more force than smaller ones.

Electric Horizontal Hydraulic Samples

Electric Horizontal Hydraulic Testers are used for testing large and heavy samples, such as structural steel and concrete. These samples are typically rectangular or square in shape and require a lot of force to break. Electric Horizontal Hydraulic Tester is designed to provide the high levels of force needed for these types of tests.

The shape of the sample can have a significant impact on the test results when using an Electric Horizontal Hydraulic Tester. For example, if the sample is not properly aligned in the tester, it can cause uneven stress distribution, which can lead to inaccurate results. The size and shape of the sample can also affect the test setup, as larger samples might require a different type of grip or a more powerful tester.

So, as you can see, the shape of the sample can have a big impact on the results of a tensile test. When choosing a sample shape, it's important to consider the material you're testing, the type of test you're doing, and the equipment you have available. By choosing the right sample shape and preparing it properly, you can ensure that your test results are accurate and reliable.

If you're in the market for a Tensile Tester or have any questions about sample shape and tensile testing, don't hesitate to reach out. We're here to help you get the most accurate and reliable results possible. Contact us today to start the conversation about your testing needs.

References

ASTM International. (2019). Standard Test Methods for Tension Testing of Metallic Materials. ASTM E8/E8M - 19a.
ISO. (2019). Metallic materials - Tensile testing - Part 1: Method of test at room temperature. ISO 6892 - 1:2019.
BS EN. (2019). Metallic materials - Tensile testing - Method of test at room temperature. BS EN ISO 6892 - 1:2019.