ASTM D7791 is used to determine the fatigue limits of rigid and semi-rigid plastic materials under repeated uniaxial stress. It is no surprise that plastic materials behave differently in service than metals. One aspect is largely due to the service temperature and the behavior that temperature can have on the mechanical properties. Plastics will fail at stress levels well below their tensile (Procedure A) or compressive (Procedure B) strengths when subjected to cyclic loading. Understanding the typical fatigue life of plastics in normal or ambient service conditions are often tested with accelerated service conditions to get end results sooner. A lot of energy is absorbed by the material and without the ability to remove that heat properly will cause the temperature to rise leading to results that might not be equitable to normal service conditions. 

Plastic manufacturing requires the confidence that your incoming raw materials and your outgoing product have the proper strength and ductility needed to manufacture products that meet your advertised competitive specifications and give a competitive advantage. You need accurate, repeatable data you can rely on. A robust, reliable, low maintenance test system that consistently delivers the stress-strain tensile properties you need will go a long way in providing comfort and efficiency in your manufacturing processes. Your business counts on cost-effective solutions to simplify and standardized results. TestResources delivers affordable systems, software, control electronics, grips and fixtures.

TestResources is your long-term partner to provide complete solutions for your testing needs. We are not just another machine supplier. Our application engineers make every effort to learn the details of your particular testing needs so they can propose the most budget-friendly solution. We strive to deliver a completely integrated system that meets ALL of your immediate and long-term technical and budgetary requirements.

We are committed to our customers immediate and long-term testing success. Our application engineers have extensive testing knowledge that you can rely on as you decide what system is right for your needs. By working with our application engineers, you can be confident that TestResources will solve your technical challenges and save you money.

Contact an experienced applications engineer today

ASTM D7791 Test Procedure

  1. To perform the test, start by preparing the specimen in accordance with the standard.
  2. Measure and record the sample’s dimensions.
  3. Load the sample into the test machine and place the extensometer on the sample.
  4. Select the frequency and program the test machine for a dynamic load and. We recommend a frequency of 5 Hz or less is used. Use extreme caution from cycling more than 5 Hz and the standard test method is important to evaluate your material property.
  5. Make sure you conduct the test at the same temperature and humidity each time, as prescribed by the test standard. We recommend using a temperature chamber and or humidity chamber for non-ambient temperature and humidity levels.
  6. Run your tests in displacement or load control to the desired levels and create an s-n or r-n curve.
  7. Use TestResources' software to control the feedback inputs and consistently deliver with confidence your test method.

TestResources has the test equipment that you need in order to perform ASTM D7791 effectively. Our expert engineers will help you find the right equipment for your test and budget. We offer fatigue test machines, grips, fixtures and other accessories that are designed in strict accordance with ASTM D7791. Contact us to find the solution that is right for you.

Common Industries where Dynamic Fatigue Testing of Plastic is used:

Recommended Test Equipment for ASTM D7791

TestResources offers electrodynamic machines capable of testing at the recommended 5 Hz service level and below for a versatile solution to handle both static D638 as well as dynamic fatigue characterization of the materials per D7791.

Our electrodynamic machines provide a cost-effective, low maintenance solution that crosses over with high resolution monotonic or quasi-static test capability and cyclic fatigue testing. Traditional servohydraulic machines are messy, loud and perform at much too high of forces to perform tests in accordance with ASTM D7791.

If you need versatility or have a need for multiple test stations running at once, we recommend you ask the applications engineer how to affordably scale up the test system for higher throughput.

Give our test engineers a call today for help configuring the best test machine and accessories according to ASTM D7791. We have the broadest range of standard and custom solutions to choose from in recommending the most cost-effective systems on the market.

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