Recently, a city government’s engineering department approached us with a need to test large plastic sewer pipe liners for flexural modulus and strength according to ASTM D790. Our normal recommendation would be a dual column eXpert 2600 universal testing machine with our MTESTQuattro software as this would provide the necessary force, size, and software to be able to run the test properly and calculate the modulus automatically. However, the customer had a limited budget which made our original recommendation not affordable. We were tasked with configuring a system that met their budget without sacrificing any accuracy in the test data. Our first idea was to use our eP2 touchpanel controller rather than MTESTQuattro software. While our MTESTQuattro software automatically calculates flexural modulus, our eP2 digital controller does not. The eP2 allows you to export the test data to your computer which can then be opened in Microsoft Excel or a similar program. This worked because our customer was willing to calculate modulus using the exported data. The second idea was to use our 5kN single column eXpert 5603 instead of the dual column eXpert 2600. However, single column machine designs have tolerances that can adversely affect the data used to calculate flexural modulus. These tolerances are column flexure, screw backlash, load cell deflection, etc. Therefore, we added a displacemnt transducer in place of crosshead position which makes the tolerances of the machine irrelevant. The transducer mounts directly to the flex fixture base and directly reads the top loading nose. This provides an extremely accurate displacment reading. To add greater stability to the system, we used a “pancake” style fatigue rated load cell in place of a normal “S” shaped load cell. The final configuration of the machine ended up being our most accurate and least expensive testing system we have developed for testing large samples according to ASTM D790. This is what the machine looked like:
