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Overview
Fatigue Spin Test Rigs are designed to expose rotating components to operating loads under realistic conditions. This enables rotor manufacturers to validate the predicted life (in numbers of cycles) of designated critical rotating components.
Test Devices’ Fatigue Rigs utilize the highest productivity drive systems in the industry. Our higher power drive systems are specifically designed for Low Cycle Fatigue (LCF) testing, enabling customers to "fast cycle" their test components. Fast cycling shortens program durations, cuts costs, and reduces the risk of damaging test assets.
Standard Modules
- Data Acquisition: All test data (e.g., temperature, speed, vibration, strain) are recorded on a custom digital data acquisition system.
- Containment Chamber: Industry leading containment capability designed for high energy applications.
- Vacuum System: Includes the pump/blower set, providing a vacuum level below 400 milliTorr, together with controls and level gauge.
- Cyclic Controller: Provides accurate control of speed for low cycle fatigue test protocols, including complex (mission profile) cycles. See Figure 1.
- Drive Systems: Test Devices offers a range of drive options for both air turbine drive systems and direct electric motor drive systems, covering the speed range up to 160,000 rpm. Our 700 Series turbines are designed specifically to perform LCF tests very rapidly, providing good data faster.
Key Features & Benefits
Armor Cylinder – Primary Containment
A robust armor cylinder is mandatory for long-term safety of the machine and the operator. The steel armor cylinder Test Devices uses for the primary containment of an uncontrolled burst is typically forged and heat treated. The single piece forging eliminates welds, reducing stress concentration and strength issues. It is designed to yield only under overload conditions, with an 18% elongation.
Test Devices designs armor cylinders to be fully elastic in both shear and tension, and they are reinforced at the top and bottom by a retention ledge. This feature strengthens the ends of the cylinder and prevents the extrusion of the soft lead inner liner against the covers.
Casing
The casing is fabricated from high strength steel. It encloses the entire test chamber and sustains a vacuum using airtight seals. The inside of the casing is larger than the outside diameter of the armor cylinder to allow the inner safety liner to expand if overloaded. This extra room allows the containment cylinder to stretch and absorb energy without ruining the vacuum chamber during an exceptionally high energy burst.
Overview
Proof/Burst Spin Test Systems are used to perform a few specific spin tests. Proof tests (also known as "over-speed" and "pre-spin" tests) are typically run to prove component integrity following preliminary machining or component repair, or for pre-stressing rotors prior to final machining. Burst tests are run to establish the operation safety margin for components and understand the mechanism by which components fail (failure analysis).
Test Devices' Proof/Burst Spin Test Systems incorporate all basic spin pit capabilities in an efficient and cost-effective system to perform proof or burst tests of high speed rotating components to meet R & D or production requirements.
Standard Modules
- Containment Chamber: Industry leading containment capability designed for high energy applications.
- Vacuum System: Includes the pump/blower set, providing a vacuum level below 400 milliTorr, together with controls and level gauge.
- Drive Systems: Test Devices offers a range of drive options for both air turbine drive systems and direct electric motor drive systems, covering the speed range up to 160,000 rpm. Our 600 Series turbines are designed specifically for proof and burst testing applications.
Key Features & Benefits
Armor Cylinder – Primary Containment
A robust armor cylinder is mandatory for long-term safety of the machine and the operator. The steel armor cylinder Test Devices uses for the primary containment of an uncontrolled burst is forged and heat treated. The single piece forging eliminates welds, reducing stress concentration and strength issues. It is designed to yield only under overload conditions, with an 18% elongation.
Test Devices designs armor cylinders to be fully elastic in both shear and tension, and they are reinforced at the top and bottom by a retention ledge. This feature strengthens the ends of the cylinder and prevents the extrusion of the soft lead inner liner against the covers.
Casing
The casing is fabricated from high strength steel. It encloses the entire test chamber and sustains a vacuum using airtight seals. The inside of the casing is larger than the outside diameter of the armor cylinder to allow the inner safety liner to expand if overloaded. This extra room allows the containment cylinder to stretch and absorb energy without ruining the vacuum chamber during an exceptionally high energy burst.
Advanced Spin Testing
Advanced Spin Testing incorporates non-traditional tests that either include variation of standard test parameters or provide additional data. Dynamic Spin Rigs can run advanced spin tests, including Radial Growth Testing and Thermal Gradient Testing.
Radial Growth Testing Detail
Dynamic Spin Rigs can measure the diametrical or radial growth of high speed rotating components in real time. Because the centrifugal forces on rotating components grow alarmingly fast as rotational speeds increase, measuring the growth at speed can be very valuable. Test Devices has used its radial growth testing during several Federal Aviation Administration overspeed/burst certification tests with great success. Growth data taken at the speed at which a component goes plastic can be very important for 3D model verification.
Thermal Gradient Testing
Dynamic Spin Rigs provide a thermal environment that more accurately simulates the engine stress environment by including both the mechanical (centrifugal) and thermal stresses. Traditional spin rigs only provide for component testing at either ambient or isothermal elevated temperatures. While isothermal elevated temperatures add an additional thermal stress component to the mechanical stress (centrifugal force), they do not apply the correct stress field across the component. Test Devices' Dynamic Spin Rigs can perform overspeed, burst and LCF testing with radial and axial temperature gradients.
Standard Spin Testing
Standard spin testing equipment typically performs overspeed, burst, and low cycle fatigue testing. Dynamic Spin Rigs can provide additional valuable test data from these routine test protocols.
Overspeed/Burst Testing
Dynamic Spin Rigs allow for the capture of valuable test data from burst events by recording with high speed camera equipment. The safety view ports installed on the bottom of the machine provide a clear view for the high speed camera, mounted underneath the test chamber, a clear view of the complete rotating assembly.
Low Cycle Fatigue (LCF) Testing
Test Devices spin test systems have long been recognized for their ability to perform rapid cycling with high power density drives, resulting in shorter schedules for LCF testing programs. Dynamic Spin Rigs include this capability as well as the ability to simulate mission profiles by dwelling at multiple speeds, for set periods of time, during a single cycle. Additionally, the Dynamic Spin Rig includes very accurate speed control to satisfy tightly toleranced speed requirements.
Crack Detection
A cracked rotor, with pristine crack surfaces, is much more valuable for analysis purposes than component shrapnel which have impacted the spin chamber containment. Because of the advantage of preserving cracked test components, each Dynamic Spin Rig includes Test Devices' patented crack detection monitoring system. The system compares the change in the vibration vector for each cycle to all of the previous completed cycles, in order to detect the initiation and growth of cracks. Test Devices has halted many LCF tests prior to component failure due to cracks detected by this unique system, and preserved numerous customer components.
Strain Survey Testing
Test data recorded during strain survey spin testing is often used to correlate 3D design models. Strain gauges mounted to the rotating assembly, in areas of peak stress, record strain throughout the spin test, up to component failure. Information gathered in these tests can be used to test complex parts, understand assembly stresses and determine the properties of materials (including composites) when exposed to operational strain under realistic conditions.
High Speed Balancing
When balancing a rotating assembly on a standard balance machine becomes impractical, or when high speed balancing is required, Dynamic Spin Rigs allow the operator to precisely measure the unbalance of the rotating assembly at speed in the spin chamber. Test Devices often uses its high speed balancing system to precisely balance large, complex test components prior to carrying out spin test protocols. Rather than having large bladed rotor assemblies rotating at high speed on standard balance equipment on the shop floor, the rotor is safely contained within the robust spin chamber of a Dynamic Spin Rig.
Overview
To avoid failures during engine test stand or flight testing, spin testing of new parts and components must begin early in a jet engine development program. For customers who choose to perform testing operations in-house, Test Devices offers the next generation of spin testing equipment. Our exclusive Dynamic Spin Rig™ more closely duplicates the reality of an operating jet engine. Advanced mechanical, thermal, material utilization and vibration stress tests can be performed with one machine that more fully accounts for conditions experienced by the real-world component. As a result, test data is much more robust and relevant than can be achieved using conventional spin test equipment.
Why It Matters
The cost of finding design problems late in development or during fielding can be high in risk to personnel, wasted dollars and missed deadlines. Component testing early and often is safer and less expensive in the long run.
Standard spin rigs are designed to test discs, but they do not have the capability to test blades and dampers; those must be tested on a shaker table. Resonance in a Blisk/IBR is highly influenced by the total component, so testing a segment on a shaker table gives limited results at best. IBR/Blisk tuning and repair can cause different blades to vibrate with different – perhaps catastrophic – mode shapes. Validation is essential before fielding components.
What You Can Do
Test Devices' Dynamic Spin Rig enables discs to be tested in real time, with the blades installed. Components are tested under centrifugal load, at operational speeds, with realistic temperature gradients, and with representative HCF engine orders and mode shapes. Resonance can be held at speed to gather realistic data. Other component parameters, such as stresses and elastic/plastic radial growth, can be measured in real time. Such advanced capabilities help to reduce engineering redesigns, lower the risk of in-service component failure, speed project completion, and reduce total cost.
Dynamic Spin Rigs are also capable of performing conventional spin tests such as overspeed, burst and low cycle fatigue (LCF) tests, as well as Advanced Spin Testing™ and Dynamic Spin Testing (high cycle fatigue - HCF) protocols.
Significantly, the ability to test discs with the blades installed and under centrifugal load is unique to Test Devices, and only Test Devices offers all of these capabilities in one system.
Dynamic Spin Rig Capabilities Include...
| Precise speed control to allow for "on resonance" dwelling in order to accumulate HCF cycles and evaluate the life of blades under realistic operating conditions. |
| Elevated temperature testing with axial and radial thermal gradients accounts for both mechanical and thermal stresses. This leads to more accurate prediction of component hot spots. |
| Extremely safe containment developed from burst testing high energy rotors, such as fully assembled turbine rotors. |
| Detection of cracks in rotating assemblies with a patented system that automatically shuts down a test when a crack has been detected, saving the flawed component for analysis. |
| Measurement of the growth of components at speed to allow for correlation with elastic/plastic material models. |
| Excitation of resonant vibrations in bladed rotors to evaluate blade/damper design performance and HCF life by simulating excitation force imparted by engine stators. |
| These capabilities and others are described in more detail below. |
Blade Testing
Managing resonant vibration of bladed jet engine rotors represents a technical challenge for engine programs. During operation, engine blades are subjected to bending and twisting modes, caused by resonant vibration, resulting in blade failure in extreme cases. To address this issue, blade, disk, and stator geometry can be modified, and dampers introduced to minimize vibration amplitudes.
Dynamic Spin Rigs simulate engine dynamic loads (centrifugal stress), thermal stresses (elevated temperature thermal gradients), and excitation forces. During testing, blades and dampers undergo actual centrifugal stress at operational speeds, replicating operational component loads. Thermal gradients can also be applied in order to test at engine operating temperatures and thermal stresses. The excitation force used to produce resonant blade vibrations simulates the impact force resulting from blade/stator passage, causing blade distortion. Both high frequency flexural and torsional modes can also be excited with engine orders (EO) of up to 100.
Dynamic Spin Rigs can carry out the following tests to evaluate the performance of complete blade/damper/rotor stage assemblies.
Damper Evaluation
Dynamic Spin Rigs provide a convenient way to evaluate the performance of damper designs installed in "engine ready" hardware. Complete rotors can be assembled with dampers installed and blade resonant vibrations excited for critical modes to determine the effect of various damper designs on vibration amplitudes. Dynamic Spin Rigs are very flexible and several different damper designs or EO configurations can be tested during the same day, with little down time between tests.
High Cycle Fatigue
Speed can be held at resonance for long periods of time and blade cracking can be detected to measure time to crack. Resonance dwell testing is important for measuring the reduction in fatigue life that results from various kinds of blade damage from foreign object impacts.
Blade Characterization
Characterization of the resonant vibration modes and amplitudes of engine blades is critical for design optimization. Slow resonance crossing enables calculation of blade amplification factors for measuring the severity of various modes and the risk they present.
The Test Devices line of Air Turbine Drives produces high power at high speed, using standard shop air as the power source. Our Air Turbine Drives are the only drives that provide the combination of high power and high speed often necessary for test drives.
To create such high power, Test Devices Air Turbine Drives consume large quantities of air. As a result they require a large air compressor and their operating cost varies directly with the customer's cost to produce sufficient compressed air.
The innovative construction of Test Devices Air Turbine Drives enables a flexible range of configurations. By changing rotor diameter and flow nozzle size, for example, it is possible to supply a wide variety of speed and power capabilities.
600 Series Turbines
The 600 Series turbines are designed for low cost and high reliability. While designed as spin pit drives, they also find applications on special test machines where their small size and mechanical simplicity outweigh their performance limitations.
Test Devices uses the 600 Series turbines for proof testing, where reliability and moderate cost are more important than short cycle time. The 600 Series turbines have similar cycle time to industry standard turbines but are substantially more reliable because of Test Devices' superior damper and spindle system.
Figure 1 shows a 602 turbine. It is shown with its axis oriented vertically, but it will operate in any orientation.
700 Series Turbines
The 700 Series turbines are the most powerful and efficient compressed air drives available for high speed applications. They are designed to provide the shortest possible cycle times in Low Cycle Fatigue (LCF) testing. These turbines have two separate rotors on a common shaft, most commonly mounted in opposite directions so each can provide torque in the opposite direction from the other. In this configuration, one rotor provides acceleration and the other braking.
Although the two rotors are normally mounted in opposition, it is possible to mount both in the same direction to double the drive power. This can be useful for test drive applications where braking is not necessary.
The 700 series turbine damper assembly includes a thrust bearing and spindle connection. The turbine section can be removed completely, leaving the test article fully supported in the spin pit. This design removes the thrust loads from the rotor bearings and increases the reliability of the rotor bearings in very long cyclic applications.
Turbine Performance Data
Test Devices uses a model number system to indicate the basic performance numbers of the turbine. The digit following the series number indicates rotor diameter, so a 706 is a 700 Series turbine with a 6" rotor tip diameter. The dash number following indicates the flow capacity of the nozzle, so a 706-45 has a drive nozzle whose total cross section is 0.45 square inches. A 706-68 has a 50% larger nozzle, at 0.68 square inches.
The entire Test Devices Air Turbine family is based on the 706-45, and all performance data are scaled from that model.
Model 706-45 Turbine Performance Data
| Maxium Operating Speed | 40,000 rpm |
| Aerodynamic Design Speed | 26,000 rpm |
| Supply Pressure | 90 psig |
| Airflow at 90 psig | 772 scfm |
| Drive Torque at Zero Speed | 251 in-lb |
| Drive Torque at Design Speed | 125.5 in-lb |
| Brake Torque at Zero Speed | 251 in-lb |
| Brake Torque at Design Speed | 376.5 in-lb |
Testing Equipment
Production/Proof ("Burst") Rigs
Test Devices offers a complete range of turnkey spin rigs for proof (burst) testing targeted at R&D applications, and over-speed (pre-spin) testing for production requirements. Many options are available to customize machines for specific needs.
Fatigue Rigs
These high-performance, rapid cycling drive systems substantially shorten test program durations to provide data sooner. An optional crack detection system identifies cracks in the test rotor during a low cycle fatigue (LCF) test, so a test can be stopped prior to rotor fatigue failure.
Dynamic Rigs
Only Test Devices offers Dynamic Spin Rigs that excite resonant vibration in fully bladed engine rotor stages. Dynamic Spin Rigs include the excitation, speed control and data acquisition systems necessary to carry out vibratory characterization, damper evaluation, and high cycle fatigue (HCF) testing programs.
Drive Systems
The direct drive systems offered by Test Devices are ideal for vertical spin rig and other test rig applications. These drives are designed to provide unparalleled performance and reliability.
Accessories/Spare Parts
For customers with existing spin test equipment, Test Devices provides upgrades and replacement parts. Critical spare parts are in inventory at our facility to shorten lead times when it matters most.
Spin Test Equipment Comparison
