Tensile testing is a type of destructive engineering and materials science test, involves applying controlled tension to a sample until it completely fails. It is a popular mechanical testing method. This test is implemented to determine the strength of a material and the extent to which it can be stretched before it fails.
You can use this test method to find out the yield strength, tensile strength, ductility, strain hardening characteristics, Young’s modulus, and Poisson’s ratio.
Well, in this reading, we’ll explore what a tensile test is, its purpose, procedure, diagram, application, properties, and standards.
Let’s get started!
What Is a Tensile Test?
A tensile test is a mechanical test that measures a material’s strength and ductility by applying a controlled tensile (pulling) force until it breaks, providing insights into its ability to withstand external forces.
A tensile test, also known as a tension test, measures a material’s reaction to tensile (or pulling) stress by applying force to a specimen of the material.
With the help of this kind of testing, product designers can acquire knowledge about a material’s mechanical properties and decide when, where, and how to utilize it.
Why Conduct A Tensile Test?
Tensile testing and figuring out what a material is made of are very important for researchers and producers in every field. Researchers have to make sure that a material can handle the mechanical forces it will face in its final use before they choose it for a new product or use.
The primary purpose of a tensile tests evaluate materials’ ductility, hardness, yield strength, and tensile strength. You must know the materials’ durability before choosing them for a prototype or final product.
Knowing the strength of your materials can help you avoid using something that will break under stress.
Tire rubber, for instance, needs to be stretchy enough to handle uneven road surfaces, while surgical sutures need to be strong enough to hold live tissue together. Also, materials and goods can be subjected to mechanical forces for a short or long time, through cyclical or repeated use, and in a wide range of temperature and environmental conditions.
While surgical sutures, even though they are only used once, must retain a constant tensile strength for the duration of the body’s healing process, automobile tires are anticipated to last a specific amount of miles in all kinds of weather conditions.
Tensile testing is important for research and development and for quality assurance teams to ensure complete product batches meet tensile property requirements. This is important for safety and business because faulty products cause product delays, revenue losses, and reputational damage.
Procedure For Conducting A Tensile Test
To conduct tensile testing, follow these steps:
- Identify the closest test method for your material, using international standards like ASTM and ISO.
- Prepare test samples according to the test standard’s shape and size. Dogbone-shaped samples are common in tensile testing.
- Set up a Universal test machine with upper and lower tensile grips, jaw inserts, an extensometer, and a load cell sized for your application.
- Use a test machine control system with data analysis software, which should be easy to use and not older than ten years.
- Load the test sample in the grips, aligning it to the center axis of the loading frame to avoid bending forces that could skew results. Contact us for advice on self-aligning grips.
Diagram Of Tensile Testing
Application Of Tensile Test
Tensile tests can help you choose the strongest textiles, metal alloys, paper pulp, and other raw materials. The following are some common applications for tensile testing:
Manufacturing/Product Development:
Thin film packaging, toys, consumer products, and automobile parts require plastic and polymer tensile strength and flexibility testing. Testing the tensile bond strength of adhesives and bonding agents between materials and the durability and tear resistance of clothes, furniture, and technical fabrics is also crucial. Assessing electrical wire, cable, and rope tensile strength.
Auto/Aerospace:
Components such as titanium, high-strength steel, aluminum alloys, and fuselages are frequently subjected to tensile testing in the aviation and automotive industries. Testing carbon fiber composites with fiberglass as lightweight, strong structural components. Screws, rivets, and bolts must be tested for strength before use.
Research & Development:
Tensile tests assess new experimental alloys, composites, ceramics, and other materials. Through the analysis of fracture spots and deformation patterns, these tests aid in the identification of the underlying reasons for material failures. Daily activities include studying how heat treatment and shaping affect tensile characteristics.
Infrastructure/Construction:
Concrete steel rebar is tested for strength and ductility. A variety of construction components, including steel I-beams, girders, and cables and wire rope utilized in suspension structures, undergo tensile material tests.
Medical:
All biomaterials and tissue engineering components utilized in implants, prosthetics, and sutures must undergo rigorous testing to ensure their strength and appropriateness. Analysis of bone and soft tissue tensile properties aids damage processes and treatment. Tests ensure catheters, tubing, and other medical equipment are safe and reliable.
Related: What is Polymer? its Properties and Additives
Tensile Test Properties
A tensile test measures a material’s response to pulling forces, providing key mechanical properties, including:
Yield Strength:
The point at which plastic deformation under stress takes place is known as the yield strength. Extensometers are used to measure the length of a gauge during tests to find this out. In non-contact situations like elevated temperature testing, devices may be mechanical clip-on or video.
Tensile Strength:
The highest stress a specimen experiences during testing is the UTS. This could be different from the specimen’s breaking strength based on whether it is brittle, ductile, or possesses both qualities. The environment can alter these material qualities, such as in extremely hot or cold temperatures.
Ductility:
Ductility is associated with a tensile test’s elongation. The maximum gage length is divided by the initial gage length to get the percentage of elongation. It is frequently explained
Modulus of Elasticity:
Young’s modulus, sometimes referred to as the modulus of elasticity, measures how stiff a material is and how quickly it will return to its initial state when a load has been removed. If the material exhibits permanent deformation and can no longer be stretched back to its original length, then Hooke’s Law is no longer valid. This is referred to as the yield strength or the elastic or proportional limit.
Strain Hardening:
A material becomes stronger when it undergoes plastic deformation under stress, a process called strain hardening. After yielding, dislocation density rises, making deformation difficult. The stress-strain curve shows this as the area where stress increases prior to necking.
Standards For Conducting Tensile Test
There are various standards for conducting tensile tests, such as ASTM E8 (for metals) and ASTM D638 (for plastics). Here’s a more structured and detailed list of tensile test standards:
Metals
- ASTM E8/E8M-24: Standard Test Methods for Tension Testing of Metallic Materials
- ISO 6892-1: Metallic materials—Tensile testing—Part 1: Method of test at room temperature
- ISO 6892-2: Metallic materials—Tensile testing—Part 2: Method of test at elevated temperature
- JIS Z 2241: Metallic materials—Tensile testing—Method of test at room temperature
- MPIF Standard Test Standard 10: Method for Determination of the Tensile Properties of Powder Metallurgy (PM) Materials
Flexible and Polymeric Materials
- ASTM D638: Standard Test Method for Tensile Properties of Plastics
- ASTM D828: Standard Test Method for Tensile Properties of Paper and Paperboard Using Constant-Rate-of-Elongation Apparatus
- ASTM D882: Standard Test Method for Tensile Properties of Thin Plastic Sheeting
- ISO 37: Rubber, vulcanized or thermoplastic—Determination of tensile stress–strain properties
Composites
- ASTM D3039/D3039M: Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials
FAQs
How do you measure tensile strength?
One way to determine a sample’s tensile strength—also called ultimate tensile strength—is to divide its peak tension force by its cross-sectional area. A tensile tester is used to determine tensile strength. The tensile tester is equipped with a load cell to measure tensile force.
What is the standard tensile test?
The ASTM E8/ASTM E8M standard outlines the uniaxial tensile testing of metals at room temperature and the calculation of characteristic values such as tensile strength, strain at break, yield strength, yield point, and yield point elongation.
What is the formula for tensile testing?
The tensile strength, also called the ultimate tensile strength, can be calculated from the curve as follows: a) σ max = P max /A 0, where P max = maximum load, A 0 = original cross-sectional area; b) the ultimate tensile strength (U.T.S.) is calculated by dividing the load at failure by the original cross-sectional area.
How is a tensile test done?
A machine grips the material at both ends and progressively pulls it lengthwise till it cracks. The pulling force, also known as a load, is shown against the displacement, or change in material length.