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Mechanical Tensile Testing Services

What Is Tensile Testing?

Testing measures material strength by exposing products or materials to controlled tension until failure. The most commonly used machine, pushes together or pulls apart the loaded material until it fails. The machine must be loaded linearly without bending the material so that the test accurately measures the tensile strength. If loaded and clamped at an angle, bending drastically alters the data, especially for brittle materials.
Universal testing machines must be able to produce adequate force capacity and speed while maintaining precision and accuracy. Force capacity describes the strength needed to fracture a material, and the machine’s speed must be quick or slow enough to mimic the real-life application of the material. Precision needs to be accurately monitored to measure the gauge length and forces applied. When done correctly tensile testing gives data for the modulus of elasticity (stiffness) of the material, its yield point, the flexural modulus of a material to resist bending, its ultimate tensile strength, its ability to elongate, and more.

Different Types of Tensile Testing

Certain materials, like ceramics, behave differently depending on if they’re being compressed or elongated. Depending on the purpose of the material, it either elongates, compresses, or flexes within the medical device. Tensile testing pushes these materials to failure to understand shortcomings or strengths of the materials used to craft mechanical components.

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Tension

Engineers manufacture tensile specimens that look like a dog bone. The two large ends get placed within the universal testing machine’s clamps vertically, while the thinner middle gets pulled until it reaches the material’s breaking point. This gives researchers readings on the ultimate tensile strength of a material, the breaking strength, and the maximum elongation and reduction in area which can be used to find Young’s modulus, Poisson’s ratio, yield-strength, and strain hardening caused by deformation.

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Compression

Compression tests pushes the device material coupons together until it buckles or gets crushed. This compression strength of the material tested comes from its internal resistance to failure. The maximum load as measured by the test machine if the maximum compression force a material can take before succumbing to the pressure.

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Flexure Testing

Flexure testing measures the force needed to bend a material to determine its resistance to bending. Researchers lay the material is laid horizontally over two points of contact and force is applied to the top from one or two force points. The testing machine exerts force down on the material until it gives way. Common materials tested during flexure include plastics, composites, concrete, and ceramics.

Types of Tensile Testing Machines

Determining what kind of testing machine you need requires a few preliminary questions
  • Are you testing a material or a product?
  • Do you need tension tests, compression tests, or both?
  • The most important question for both testers and clients remains, which regulatory agencies do the tests need to be reported to afterwards?
Once we know what we’re testing and where to report the data, we’ll determine the amount of force capacity needed to cause failure or given proof load, which is the limit a material can withstand without deforming. Empirical researchers also want to know the size of the test subject to quantify the vertical and horizontal requirements needed to run tests. Universal Testing machines come in all sorts of dimensions to fit different designs.

Hydraulic Testing Machines

Hydraulic machines are devices used to convert a fluid’s energy into mechanical energy. Their sturdy designs provide excellent load and position control. Compared to electromagnetic devices, they provide a cheaper option in terms of force capacity.

Types of Tensile Tester Designs

Within hydraulic and electromechanical testing machines lie three subcategories that apply force in different manners. The compression and tensile mechanisms rely on a solid frame that holds things in place as they push products and materials together or pull them apart. The window refers to the open spaces above or below the crushing/elongating mechanisms.
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These testers apply tension and compression below the moving crosshead and are usually screw driven.

These models provide tension testing in the upper window and compression testing in the lower window. They’re common in hydraulic setups, but can also be found on screw driven options.

These universal machines can test compression or tension in either of the available windows.

Standard Test Methods Used in Tensile Testing

Empirical Technologies Scope of Accreditation currently covers the following standards:
ASTM
ASTM F1147
ASTM F2193
ASTM F2276
ISO
ISO 9585
ISO 7206-4*
ISO 7206-6*
FDA/510(k)
We work with the test engineers to ensure the data that is needed to have a successful 510(k) process is gathered. Our consulting team ensures the necessary tests are performed, saving you time and money.
*Equipment for this test is calibrated to ASTM E4 but the dynamic verification of the equipment per ASTM E467 and/or ISO 4965 is not performed.

Why Is Tensile Testing Performed?

Tensile testing pushes materials and products to their limits to determine the amount of pressure needed to cause failure or given proof load. Tensile testing is an integral type of testing that allows end users to help determine if a product or device will last the duration of its life lifecycle.

Test Properties of Tensile Testing

Tensile testing services measure five different properties to determine a material or devices tensile strength:
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Yield Strength

A material or product’s yield strength refers to the resistance of a tested specimen to retain elasticity or undergo plastic deformation. Elasticity means the ability to bounce back and retain shape, while plastic deformation permanently deforms the specimen. Subjects to be tested get fixed in place and pulled apart until they deform or break.

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Ultimate Yield Strength (UTS)

Often referred to as tensile strength (TS), ultimate strength or, Ftu in equations, this property refers to the maximum stress a material or product can withstand while being pulled or stretched without breaking. This property becomes less important when judging ductile materials, but gives important feedback for brittle materials like alloys, wood, ceramics, plastics, and composite materials.

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Ductility

Ductility describes the malleability of materials to be drawn out or plastically deform without fracturing. This determines the softness of materials used to create components within mechanical devices. Adding different compounds to the materials can change the properties of existing materials to make them more or less malleable.

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Strain Hardening

Also called work hardening or cold-working, strain hardening makes metals harder through plastic deformation. As metal gets pushed past its yield point, additional stress becomes needed to cause additional plastic deformation, which suggests the metals became stronger and harder to deform.

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Modulus of Elasticity

This technical terminology measures a material’s elasticity. It quantifies the ability of material to resist non-permanent (elastic) deformation. On a graph, the modulus represents the slope of the straight line portion of an stress-strain curve and describes the change in stress divided by the change in strain. This means that objects made from the same material will have the same modulus, although bigger specimens require more force to deform. Brittle materials exhibit higher modulus value than malleable ones.

Advantages of Using Tensile Testing

Tensile testing gives researchers and manufacturers clear insight into the quality and integrity of materials used. It also helps determine whether individual parts within medical devices can withstand regular or strenuous clinical use. With a clear understanding of a material’s limitations, producers can determine the quality and capabilities of it, ensure regular consistency in manufacturing, and perhaps cut material costs to achieve desired results while saving money.

Common Industry Applications for Tensile Testing

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Understanding the Properties

Many industries utilize tensile testing to understand the properties of materials on different scales. When manufacturers understand the tensile properties of chosen materials, they can make better choices to cut costs, strengthen or redesign weak areas, and maintain consistent results as they mass-produce products.

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Developing Tests

When you make Empirical Technologies part of your team, we work to develop tests that fit your needs. If regulations call for specific tests, or your development team decides to test the tensile strength of specific mechanisms, let us know! Empirical Technologies goal to be the standard for medical testing means we dedicate our practice to making sure clients get transparent, speedy, and accurate results to help get devices to market as soon as possible.

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Frequently Asked Questions

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A materials strength means its capability to withstand loads of pressure without failing due to excessive stress or deformation. Researchers look at the ultimate tensile strength, point of fracture, offset yield strength, the reduction of area, and the percent of elongation a material or device can withstand.

Electromagnetic universal testing machines create extremely accurate data and can be adjusted easily, which gives them a wide range of applications. Hydraulic machines rely more on manual operation, but they can create force more easily for high capacity tests.

Improperly loading tested materials create inaccurate data. The specimen’s alignment ensures testing of the material’s tensile properties. If the material or product gets misaligned, this causes bending that can cause a specimen to fail at levels that don’t match the product’s purpose.