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How Does Tensile Testing Work?

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Tensile testing, also known as tension testing, is a type of mechanical test used to determine how a material responds to a stretching force. This test helps evaluate the mechanical properties of an object, such as metals, polymers, composites, and various other materials.

Performing a tensile test applies a load to specimen, and gradually increasing the load sometimes until failure or destruction. The tensile data is analyzed by using a stress-strain curve.

Interface stain gage load cells are commonly used in tensile testing due to their high precision and sensitivity. They work by measuring the strain in a material, which is directly related to the applied force. This strain data is then converted into force measurements. Learn more in Tension Load Cells 101.

Tensile testing is fundamental in test and measurement. It is used by researchers, testing labs, and engineers across industries including infrastructure, medical, manufacturing, aerospace, consumer goods, automotive, energy, and construction.

How Tensile Testing Works

Tensile testing is essential in materials science and engineering to understand the material’s behavior under tension and to ensure its suitability for specific applications.

First, a specimen of the material is prepared with a specific shape and dimensions. This sample is carefully controlled to meet testing standards based on the test plan.

Interface supplies a variety of load cells for these tests. The load cell is typically mounted in a tensile testing machine. The tensile test machine has two separate jaws, one of which will move away from the other at a controlled rate during the test. As it moves away, it is pulling on the material, stretching it until it the test is complete, or it breaks. This is also referred to as testing to failure or destruction. The controlled rate is called the strain rate, and materials will behave differently under different strain rates.

The specimen is then securely mounted in a testing machine, which is usually called a tensile testing machine or universal testing machine. The load cell is positioned in such a way that it bears the load applied to the specimen during the test.

Load cells are commonly used in tensile testing to measure and record the force or load applied to a specimen during the test. These sensor devices are crucial for accurately determining the mechanical properties of materials under tension.

The testing machine applies a pulling force (tensile force) to the specimen along its longitudinal axis. The force is gradually increased at a constant rate, causing the specimen to elongate.

As the tensile testing machine applies a pulling force to the specimen, the load cell measures the force in real-time. This force measurement is typically displayed on a digital instrumentation device or recorded by a data acquisition system.

The recorded data, including the applied force and the corresponding elongation or deformation of the specimen is usually plotted on a stress-strain curve for analysis. The stress-strain curve provides valuable information about the material’s mechanical properties, including its ultimate tensile strength, yield strength, Young’s modulus, and elongation at break.

Engineering Checklist for Tensile Test Plans

  • Identify the Purpose of the Tensile Test
  • Select the Material and Test Standard
  • Define the Mechanical Properties
  • Determine the Specific Mechanical Properties for Evaluation
    • Common properties include tensile strength, yield strength, modulus of elasticity (Young’s modulus), elongation, reduction in area, stress-strain curve characteristics
  • Establish Test Conditions
    • Include temperature, strain rate and testing environment
  • Define Sample and Specimen Requirements
  • Determine Measurement Accuracy Requirements
  • Prepare Instrumentation and Equipment
  • Plan for Data Recording and Reporting
  • Review Compliance Requirements and Safety Standards
  • Document Test Plan
  • Publish Verification and Validation Processes
  • Report Results

Defining measurement requirements for tensile tests by specifications is a crucial step in ensuring that the tests accurately and reliably assess the mechanical properties of materials.

Tensile Testing Terms to Know

Stress: Stress is the force applied per unit cross-sectional area of the specimen and is usually denoted in units of pressure. Stress is calculated by dividing the measured force by the cross-sectional area of the specimen. The load cell’s force measurement ensures that the stress values are accurate and precise. Simply, stress is the amount of force applied over a cross-cross-section.

Strain: Strain represents the relative deformation of the material and is the change in length (elongation) divided by the original length of the specimen. Strain is the amount of elongation in a sample as it is stretched or squashed.

Elastic Region: In the stress-strain curve, the initial linear region where stress is directly proportional to strain is known as the elastic region. Here, the material returns to its original shape when the load is removed.  As soon as a material is placed under any load at all, it deforms. Visually, the deformation may not be noticeable, but right away, the material is deforming. There are two types of deformation: elastic (not permanent) and plastic (permanent).

Yield Point: The yield point is the stress at which the material begins to exhibit permanent deformation without an increase in load. It marks the transition from elastic to plastic deformation.

Ultimate Tensile Strength (UTS): UTS is the maximum stress the material can withstand before breaking. It is the highest point on the stress-strain curve. If the material is loaded to its UTS, it will never return to its original shape, but it can be useful in engineering calculations, as it shows the maximum, one-time stress a material can withstand.  Load cells can detect the exact moment of specimen failure, such as fracture or breakage. This information is crucial for determining the ultimate tensile strength and other mechanical properties of the material.

Elongation at Break: Elongation at break is the amount the specimen stretches before it breaks, expressed as a percentage of the original length.

Load cells can also be used for real-time monitoring and control during the test. Test operators can set specific load or strain rate parameters to control the testing machine’s operation and ensure the test is conducted within specified conditions.

Load cells play a safety role by providing feedback to the testing machine’s control system. If the load exceeds a certain threshold or if the load cell detects an anomaly, the testing machine can be programmed to stop or take corrective actions to prevent damage to the equipment or ensure operator safety.

To discuss Interface products and experience in tensile testing, be sure to reach out to our global representatives in the field or contact us. We are always here to help!

Tension Load Cells 101

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A tension load cell is a type of force sensor used to measure tensile forces in materials, structures, or machines. It is used to measure the maximum load that a material can support without fracture when being pulled or stretched under the applied load. A strain gage manufactured inside the load cell sensor measures the deformation and converts it into an electrical signal.

The main difference between a tension load cell and a compression load cell is the direction in which they measure the force being pushed or pulled. Though most Interface high performance load cells are designed for both tension and compression, specific load cells are calibrated in tension only to measure forces that pull or stretch a structure. As the load cell stretches, it measures the resulting force.

It is customary practice for most labs to use tension and compression load cells, then determine its specific tension use case based on the requirements of a test project or product design. Tension and compression load cells are easily used for tension only but will measure both. Load cells can be calibrated in either tension or compression, and both tension and compression. The combined is more economical for test labs and most use cases.

Benefits of Tension Load Cells

Load cells that measure tension are preferred over other types of load cells when the force being measured is tensile in nature. They are accurate, reliable, and can be calibrated to suit different applications and environments. Additionally, they are easy to use and require minimal maintenance.

Accurate measurement of tensile forces: Tension-only load cells are specifically designed to measure tensile forces accurately, without being influenced by compressive or bending forces. This makes them ideal for applications where the force being measured is purely tensile, such as in the testing of cables, wires, ropes, or chains used in lifting applications and equipment. Interface Tension Links are preferred for these types of lifting and weighing use cases.

High sensitivity and resolution: Tension-only load cells typically have high sensitivity and resolution, meaning they can detect slight changes in the applied force. This makes them useful in applications where precise measurements are required, such as in the testing of materials with low tensile strength.

Easy installation: Tension-only load cells are typically easy to install and use, requiring minimal setup time and equipment. They are often designed with attachment points or hooks for attaching to the load being measured, which makes them convenient for use in the field or in a testing lab.

Durability and reliability: Tension-only load cells are often constructed from durable materials, such as stainless steel, which makes them resistant to corrosion and wear over time. They are also designed to provide reliable and consistent measurements, ensuring accuracy and consistency in test results.

Tension Load Cell Applications

Tension load cells are standard and their versatility in application use makes them popular in test and measurement. Tension load cells are used for test and measurement industry applications including in manufacturing, automotive, energy, aerospace, and infrastructure. For example, the transportation sector uses load cells to measure the tension in cables, wires, ropes, and chains. They are used in a diverse range of testing equipment to measure the strength and durability of materials. They are designed to provide accurate and reliable measurements of tensile loads and can be calibrated to suit different applications and environments.

Tension load cells are commonly used in applications for material testing to evaluate the tensile strength and elasticity of varied materials, such as metals, plastics, and composites. Tension testing is a valuable tool in materials science and engineering, as it provides valuable information about the tensile properties of a material. Some examples of tension testing include:

  • Determining the strength of a material: Tension testing provides a way to measure the maximum load a material can withstand before it breaks or fails. This information is crucial in determining the strength of a material and its suitability for different applications.
  • Understanding the ductility of a material: Tension testing can also be used to measure the amount of deformation a material can undergo before it breaks. This information is important in determining the ductility of a material and its ability to withstand bending and stretching without breaking.
  • Identifying defects or weaknesses in a material: Tension testing can help identify defects or weaknesses in a material that may cause it to fail under stress. By subjecting a material to increasing levels of tension, engineers can pinpoint the point at which the material fails and investigate the cause of the failure.
  • Comparing the properties of varied materials: Tension testing can also be used to compare the tensile properties of different materials. This information is useful in selecting the best material for a specific application and designing structures that can withstand the required loads.

Tensile Testing For 3D Materials

A customer wants to conduct a tensile force test on different 3D printing materials until failure. These different 3D printing materials being tested included PLA, PETG and ASA to see how they performed. The customer wanted to test the materials quality, strength, ductility, and stiffness. Interface recommended using our 1200 Standard Precision LowProfile™ Load Cell be installed into the customer’s test frame. The tensile test is conducted, and force results captured by the load cell are synced through the INF-USB3 Universal Serial Bus Single Channel PC Interface Module. These results can be displayed on the customer’s computer with supplied software.

Tension load cells are used in structural testing to measure the tension in structures used in construction, aerospace, maritime, and infrastructure. For example, tension load cells are commonly used for bridges, buildings, and towers, to ensure they can withstand the forces in their design and application.

Tension load cells are often used within manufacturing machines and equipment for monitoring and real-time force measurement. For example, in a facility they are used to measure the tension in cables or wires during production, to ensure they meet the required specifications and are safe for use.

Research and development for all types of applications need to assess the tensile properties of new materials or structures, to assess their suitability for different applications, from medical devices to product simulations.

If your next project needs an accurate tension load cell, contact our application experts to see which model best fits your exact requirements.

ADDITIONAL RESOURCES

Interface Solutions for Material Testing Engineers

Tensile Testing for 3D Materials App Note

Testing Lab Essentials Webinar

Bolt Tension Monitoring

Mooring Line Tension Testing App Note

Tension Links 101

Interface Solutions for Material Testing Engineers

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Force measurement inherently is part of all types of engineering throughout the entire development process of products, structures, consumer goods, and the materials used to construct them.

In the beginning of the design and development processes, material testing engineers utilize sensor technologies and instrumentation to measure the durability, fatigue, safety, and quality of the materials used for their projects.

The role of a materials engineer is to develop, process, combine, and test materials to be used in production. Based on data gathered, combined with their expertise, the materials engineer will identify and recommend the appropriate materials for specific applications. Ultimately, they are the foundation of product development because it is their responsibility to select materials based on the use of the product, its ability to perform its task and function, and durability of materials to hold up over time. They also test for environmental impact and exposure considerations.

Five Categories of Material Testing

  • Mechanical testing
  • Testing for thermal properties
  • Testing for electrical properties
  • Testing for resistance to corrosion, radiation, and biological deterioration
  • Nondestructive testing (NDT)

Force measurement is most often used is in the material testing category of mechanical testing. This applies to testing materials used in all types of industries, including infrastructure, aerospace, automotive, industrial automation, manufacturing of consumer goods and in the machines used to assemble products. In mechanical testing, Interface sensors are commonly used to conduct:

  • Hardness Testing
  • Tensile Testing
  • Impact Testing
  • Fracture Toughness Testing
  • Creep Testing
  • Fatigue Testing
  • Nondestructive Testing

Interface Material Test Engineer Solutions

Material testing has been around since the first invention, to determine quality, durability and resilience of products and parts. What has changed over the centuries and decades is the sophistication of force testing and measurement. Interface’s robust line of load cells, torque transducers, multi-axis sensors, and instrumentation are used in about every industry for material testing. If it must be measured, Interface has a solution.

Interface’s force measurement products are being used to gather data from testing materials in applications used for industrial automation, structures, medical devices, vehicles on the ground and in the air, packaging, sports equipment and more. Material testing engineers ensure reliability and safety of the chosen materials. Here are examples of how material testing engineers use our products.

Tensile Testing of 3D Printing Materials

Interface was contacted by a test engineering team in search of a solution for conducting a tensile force test on different 3D printing materials until failure. They wanted to test several types of material types. The 3D printing materials to be tested to see how it performed included PLA, PETG and ASA.  The test of the materials was to assess strength, quality, ductility, and stiffness. Interface supplied our most popular load cell, the 1200 Standard Precision LowProfile™ Load Cell, to install into the engineer’s test frame. The tensile test gathered the force results from the load cell that was synced through Interface’s instrumentation solution, the INF-USB3 Universal Serial Bus Single Channel PC Interface Module. The results were displayed on their computer with supplied software from Interface. Read more about this material testing application solution here.

Bike Frame Fatigue Testing

Fatigue testing is a critical material test used to ensure the materials used in a product hold up over time. A bike manufacturing company wanted to perform a fatigue test on their bike frames to analyze the strength of their frames, ensure durability and high-quality standards. Interface suggests installing Model 1000 Fatigue-Rated LowProfile™ Load Cell to the customer’s bike frame fatigue tester. This load cell will provide the customer highly accurate results through the fatigue cycling. Results are collected using the INF-USB3 Universal Serial Bus Single Channel PC Interface Module and displayed on the customer’s computer with Interface’s provided software. The bike manufacturing company successfully had their bikes undergo fatigue frame testing, receiving highly accurate results with Interface’s load cell and instrumentation. Watch the fatigue testing of the bike frame in this animated app note.

Spring Compression Testing

A customer wanted to evaluate the performance of their springs, but also the functionality of their spring test stand with a wireless solution. Interface suggested using one of their WTS-5200XYZ 3-Axis Force Moment Load Cell which has three integral WTSAM-1E Wireless Transmitters and installing it into the customer’s spring compression frame. The WTS-5200XYZ 3-Axis Force Moment Load Cell measured the force compression of the spring. The integral WTS-AM-1E Wireless Strain Bridge Transmitter Modules transmitted and displayed the information wirelessly to the LCCAXXX Wireless Instrument Enclosure. Using Interface’s solution, the customer was able to wirelessly get compression results on the spring being tested. They were also able to verify their spring compression test stand was working effectively.

Selecting the right material is critical to product develop and material testing engineers rely on Interface due to the accuracy and reliability of our solutions. If you have questions on what products are best suited for your material testing applications, please contact us.

ADDITIONAL RESOURCES

Tensile Testing for 3D Materials

Furniture Fatigue Cycle Testing

Bike Handlebar Fatigue Testing App Note

Aircraft Wing Fatigue App Note

Material Tensile Testing

Why Civil Engineers Prefer Interface Products

Beam Stress Test