New Frontiers in Precision, Control for Tight Thermal Gradient and Real-Time Spin Testing

September 19, 2011

Hudson, Mass. – The research and development efforts that Massachusetts-based Test Devices, Inc. has invested in advanced spin testing paid off twice recently when customers presented unique challenges to the firm.

Test Devices received a request to design a difficult high temperature test environment for a proprietary Low Cycle Fatigue test. This project required a rim-to-bore gradient of more than 250&Deg;F/121°C. The challenge for Test Devices was to design hardware capable of generating and controlling the temperature gradient within the spin test chamber. The test required a very specific temperature profile and very tight tolerances. The company was able to hold this profile to +/- 5°F/2°C while cycling between the high and low operating speeds to simulate engine conditions. A separate test conducted on the hardware demonstrated that the system is capable of generating the thermal gradient of 400°F/382°C from the rim to the bore of an appropriately sized test disk. This test was designed to enable the generation of a multi-axial stress field driven by the thermal gradient and centrifugal load; generate a multi-axial stress field in the disk’s critical features and allow the OEM to evaluate the durability of the part in more realistic conditions.

Test Devices employed a unique thermal chamber designed to deliver and hold the temperature conditions required by the customer. The design of the chamber was based on both relevant past experience within Test Devices and extensive computational analysis to understand and evaluate the thermodynamic behavior of the test rig.

Another successful aspect of this project was the Test Devices’ patented Crack Detection System that acts as a health monitoring system during cyclic tests. The system was able to detect the existence of emerging cracks within the test assembly, and alert the testers of a potential problem before any destructive damage (burst) occurred. In this case, crack detection indicated the emerging faults in the disk much earlier than typical inspection methods (such as FPI) could confirm its presence: The damage was confirmed by careful expert examination under microscope. The successful crack detection prevented the test piece from catastrophic failure prior to the planned inspection interval, saving time and money.

In the second test scenario, Test Devices was contracted to conduct another proprietary thermal gradient test to evaluate a unique failure mode driven by a multi-axial stress field in elevated temperature conditions. Test Devices’ customer was interested in confirming the material behavior under high-speed and elevated temperature conditions. Traditionally this type of test involves several runs at progressive incremental speeds and thermal conditions. Each of these test increments is followed by disassembly, inspection, measurements and evaluation of the dimensional change on the test disk, and re-assembly for the next increment. This effort and iterative approach is a major contributor to the cost of such testing.

Test Devices has devised an advanced measurement technique to monitor the growth of the disk in-situ, at the high-test temperature conditions. This in-situ laser-based growth measurement technique was installed in the spin pit, and successfully recorded growth of the test piece throughout the required speed range and up to the eventual burst conditions. Because the in-situ technique was employed, the customer was able to get seamless critical material data for the part without the interruptions and inconsistencies known to result in the traditional incremental method. The new technology also allowed Test Devices to complete the test in significantly shorter time and less expense for the customer.

In each of these situations, demanding OEM’s turned to Test Devices as the one of a few companies in the world that has the ability to conduct these tests to exacting specifications. Test Devices has devoted significant research and development efforts into the design and implementation of its advanced spin testing capability in elevated temperature environments. This capability is attractive to testers that need to generate and maintain range of temperature profiles on the test piece to a very precise tolerance. “We’ve made these technological advances in response to industry trends wherein gas turbine engines are exposed to hotter, harsher and more demanding environments; maintaining the integrity of these engines requires testing that genuinely validates that spinning components are up to the job. We also recognize the importance of developing the in-situ test methods for customers wanting realistic testing done on time and in as cost effective a manner as possible,” says Robert Murner, President at Test Devices.

About Test Devices
For over 30 years, Test Devices, Inc. has been the world’s premier source for rotational testing equipment and services. Test Devices provides advanced technology spin testing services to customers in a wide variety of industries. The company works with developers and producers of high-speed rotational components of jet engines, gas turbines, medical centrifuges, machine tools, industrial compressors, and high-speed electric motors, among others. For more information contact David Woodford at +1-978-562-4923,, or visit