Category Archive: Spin Testing

Spin Testing Additively Manufactured or 3D-Printed Parts

Additive manufacturing (AM) is the process of building 3D workpieces layer by layer. Rather than traditional processes such as machining, which create forms by removing the material from stock material, additive manufacturing “prints” layers into a part from a computer model created with Computer Aided Design (CAD) software.

The AM technique has been around for some time. With recent advancements in technology, it has been gaining more popularity and relevance. The AM techniques are also known as:

  • 3D Printing
  • Rapid Prototyping (RP)
  • Direct Digital Manufacturing (DDM)
  • Layered Manufacturing
  • Additive Fabrication

With the ongoing improvement on the quality of parts made with AM method, it is also becoming increasingly cost-effective. Many industry leaders believe that AM will soon become an integral part of new products and future manufacturing processes. AM technology is in the midst of a revolution, and manufacturers continue to see new benefits from new methods as they enter the market.

Why 3D Print High-Speed Rotor Parts?

Leading turbomachine OEMs are looking into a possibility of additively manufacturing high-speed rotor parts. Within the AM technologies for printing metal parts, one of the immediate areas of application for the AM parts is the replacement of (or enhancement of) traditionally cast parts.

There remain many challenges ahead of where we are today. Many manufacturers have begun to weigh the benefits of additively manufacturing the rotors with airfoils, cooling channels, and many intricate features. The potential benefits of AM for OEMs include:

  • Equivalent or stronger than min-property cast parts
  • Consolidation of multiple parts – Reduced manufacturing cost
  • Enabling new designs which cannot be made with traditional manufacturing techniques

GE and other industry leaders have waylaid some of these concerns by building functional turbine engines using 3D printing. The electron beam from one machine can fabricate many static engine parts, and recent demonstrators showed a possibility to manufacture a blade from titanium aluminide powder, a material so brittle that it could previously only be fabricated using expensive molding processes.

Along with challenges in achieving higher dimensional accuracy and better surface finish, one of the challenges in additively manufacturing a high-speed rotor is that the parts must be reliably made and validated. It is understood that the AM process has not resolved the problems related to internal defects such as material porosity, discontinuity, and directionality.

High-Speed Spin Testing is Critical for Development

Test Devices (TDI) has been spin testing cast rotors for years. With the emergence of additive manufacturing, we are starting to work with some customers to spin test their rotors. High-speed spin tests can be used to stress the parts and verify their structural integrity.

Looking further, TDI is evaluating the benefit of pre-spinning the casted or additively manufactured rotors to achieve the following benefits:

  • Stabilizing the material and minimizing the in-operation change in unbalances
  • Application of pre-spinning process to the rotors to bake-in advantageous residual stress state
  • Improving engine efficiency through controlling the rotor growth behavior and improving tip clearance

Spin Test Additively Manufactured Rotor Parts with Test Devices, Inc.

TDI continues to look into advancing and improving our spin testing technologies and services. We strive to be your “One-stop Shop” and offer comprehensive services to meet your spin testing and manufacturing needs (pre-spin, pre, and post-spin machining, balancing).

TDI offers fully compliant operation in accordance with AS9100/ISO9001 (+ OEM QPR) certified processes, backed by the demonstrated capabilities:

  • Handling high-volume loads of 6,000+ units
  • Managing 30+ manufacturing spin operations consisting of different parts of varying designs and sizes
  • Fast turn-around and guaranteeing high-quality work achieved by in-house inspections/quality assurance, machining, and balancing capabilities

Spin testing can contribute to enhancing the safety and the performance of additively manufactured rotors. Contact TDI today to learn more about spin testing 3D printed parts.

Spin Testing for Manufacturing 101

In the quest to produce stronger, more durable, and cost effective rotating parts, manufacturers are turning to spin tests to help achieve these goals. Spin tests for manufacturers can be used to validate the stability and integrity of a part, or to enhance the desirable properties of the material. We will explore the differences between traditional spin testing and spin testing for manufacturing purposes. We will also discuss the benefits of spin-testing your rotating parts, the subtle but important factors necessary to run successful manufacturing spin operations, and the importance of finding the correct spin testing service provider for your specific needs.

Jet engines, power turbines, turbochargers, electric motors — all of these high-speed rotating parts are critical for a wide range of modern high-performance machines and key infrastructures. In order to ensure optimal reliability, durability, and quality, these components must undergo rigorous engineering and testing processes.

Spinning at high speed, a machine part, such as a jet engine disk, stores a significant amount of rotational kinetic energy. In the event of a part failure, this stored kinetic energy is released, and the end result can be catastrophic. To prevent this, a spin test is conducted to evaluate the structural integrity and robustness of high-speed rotating parts. The data collected from this test allows engineers to better understand rotors’ failure behavior and improve the design as needed. Introduced more than half a century ago, spin testing techniques have been integral to the evolution of high-speed rotating machines.

While there are a variety of spin tests available, most of them can be grouped into one of two major categories: Spin Testing for Research and Development and Design Validation, or Spin Testing for Manufacturing.

Spin Testing for R&D and Design Validation

  • Custom-designed engineering tests used to validate the rotor design and/or certify the part
  • Typically involve a prototype, first article, or purpose-designed test rotor assembly
  • Design, build, and execution of the test should be carried out as a carefully managed engineering project
  • Test rig designs aim to maximize measurability of engineering data, and create realistic conditions during the test to simulate the relevant operating environment of the machine
  • Some examples of R&D and Design Validation spin testing include: Overspeed Certification Tests, Low Cycle Fatigue (LCF) Tests, High Temperature and Thermal Gradient Spin Tests, and Dynamic Spin/High Cycle Fatigue (HCF) Tests

Spin Testing for Manufacturing

  • Involve processing batches or a large volume of parts to specified operation and inspection steps
  • A quality-controlled manufacturing operation is streamlined to produce consistent, quality products
  • Timeliness, quality, and efficiency are the key drivers of a successful manufacturing spin operation

Achieving Repeatable Success in Manufacturing Spin Tests

While manufacturing spin tests may appear simple and uninvolved in comparison to the more complex and sophisticated R&D spin tests, the success and usefulness of all tests depends on the expertise of the team you choose to partner with. Experienced technicians and engineers will have carefully planned quality processes in place to ensure smooth testing and reliable results.

In order to deliver products to customers’ specifications both cost-effectively and on time, manufacturing spin tests must make use of robust, high-quality manufacturing systems capable of achieving success over thousands (and sometimes millions) of iterations. In order to achieve this repeatability, a holistic approach that considers the details of each step in the operational workflow must be employed.

Manufacturing spin tests can be further broken down into two categories:

  1. Overspeed Test

Overspeed tests are conducted to validate the stability of rotor balance and part integrity in a high-speed environment. Final machined parts, such as turbocharger impellers and turbines, are spun to a customer specified rotational speed to validate the parts’ integrity.

  1. Forging Pre-Spin

The forging pre-spin method involves a material conditioning process for aero-engine and power turbine disks. Semi-finished or un-machined forgings are spun to a specified speed to yield the material. There are several benefits of pre-spinning forgings and disks, but typically this work is done to enhance the stability and durability of the material and final products. Forgings are carefully inspected and monitored at each step of the pre-spin process to ensure proper material conditioning.

Manufacturing Spin Operation at a Glance

  1. Inspection: Examine the parts for any damage or anomalies; some customers also require part inspections for dimensional conformance
  2. Assemble the part with spin tooling
  3. Check rotor balancing, and perform corrections if necessary
  4. Perform a spin test; monitor rotor balance and rotor dynamic stability over the test speed
  5. Record and report the result
  6. Disassemble the part from the spin tooling
  7. Perform post-test inspections, and ship the part to the customer

Specific to forging pre-spin operations, customers also often require a “pilot run” during the earlier phase of process implementation; the pilot run is typically performed prior to launching a full-scale manufacturing spin operation. A series of pre-spin tests is performed to validate the tooling design performance and try out the handling equipment, operational processes, and documentation flow. These pre-spin tests also allow clients to confirm the material behavior (forging growth to a speed).

Several factors can disrupt successful pre-spin operations, however, including:

Poorly Designed Spin Tooling — Performing an efficient, repeatable operation requires well-designed tooling and handling equipment. Poorly engineered spin tooling can lead to unstable rotor behavior, rotor dynamics issues, and limited reusability in the tooling — ultimately resulting in incipient, recurring issues in pre-spin operation. Successful spin tooling design depends on:

  • Tooling and handling equipment design performed by an experienced engineering team that understands the ins and outs of spin operation.
  • Years of experience designing and routinely testing different types of spin tooling for different test disks.
  • Comprehensive engineering work, from the selection of suitable materials to detailed stress and dynamics analyses of the rotor assembly. Careful engineering ensures reusability and high performance of the tooling in the manufacturing environment.

Balancing and Severe Vibration Issues — A critical step in rotating machine construction, proper rotor balancing helps ensure no time is wasted troubleshooting rotor dynamics and vibration issues. –

  • Balancing is often overlooked and performed without a real understanding of its importance. Specific to pre-spin operations, the forgings coming off the production line typically have unfinished contours and are often severely unbalanced. Adding extra steps for machining and balancing forgings, however, results in added costs and downtime. In some cases, forgings may not be able to be easily balanced. (TDI’s high-performance damper system is specifically designed to manage vibration and rotor instability problems.)

Bad Quality Processes and Material Handling — For professionals working within the strict requirements of the aerospace standard, quality processes must be kept in mind throughout the entire operation. Here’s what to look for when sourcing for aerospace standard processes:

  • Services based on the AS9100/ISO9001 quality standard, backed by experience with leading aeroengine OEMs.
  • A culture of quality that ensures every step of the spin tooling process is performed to stringent standards. Through closely monitored parts tracking and receiving to meticulous inspection and pre-spin work, there should be a guarantee that all processed parts are of the highest possible quality and reliability.
  • Highly trained staff, state-of-the-art spin rigs, CMM machines, and climate-controlled inspection rooms.

Inaccurate Speed Measurement and Control — Measuring and controlling rotational speed is critical for successful spin test operations, but this step is also often overlooked.

  • Inaccurate speed data and spin test operational records can lead to catastrophic field accidents. Whether done intentionally or unintentionally, rotors spun to an incorrect speed severely compromise the integrity of the parts and the machines.
  • In a nonconformance case with an exceeded speed target, the rotor may have sustained damage that is undetectable to inspectors.
  • In a nonconformance case with an undershot speed target, there are two likely causes: 1) The rotor was not tested properly to the requirement, or 2) The rotor may not have achieved the required material conditioning at the specified target speed.
  • Measuring, recording, and ensuring the accuracy of spin test speed is one of the most important steps in spin test operations, directly affecting the quality of the part. Plus, it’s very difficult and time consuming to examine the aftermath of an incorrectly executed spin test.

Rotor Bursts — Accidents can happen even in the most diligently planned and managed manufacturing environments. During spin testing, it’s important to take preventative measures to manage the risk of disk bursts, since rotors spinning at high speeds store a large amount of rotational kinetic energy that can be released in the event of a part failure, leading to catastrophic damage.

  • The first priority in managing the risk of a disk burst is ensuring optimal safety. Spin pit containment alone is not enough; facilities must take necessary measures to protect spin pit operators and surrounding equipment from unexpected containment failures. Ideally, spin pits should be placed in a purpose designed test cell with a separate operator room so that workers are not at risk.
  • Downtime in any manufacturing process can cause client dissatisfaction and added expenditures, so it’s critical to establish a practical contingency plan that will allow you to quickly respond to and recover from accidents, should they occur.
  • Specific to forging pre-spin work, operators should carefully manage the risk of disk bursts. Forgings are heavy and typically spun to a relatively high speed, which means they can cause great destruction in the event of a burst.

Learn More

For over 40 years, Test Devices Inc. (TDI) has been a leading provider of spin testing services and equipment, developing and advancing the science of centrifugal, vibratory, and thermal stress testing. Whether you’re interested in setting up your own manufacturing spin operation or looking to outsource the work, you’ll need a dependable partner to ensure optimal performance, quality, and reliability.

Since first introducing pre-spin testing services to our range of capabilities ten years ago, TDI has become a trusted partner for various leading OEMs in the development, innovation, and implementation of their pre-spin operations. As a leading expert in spin testing and related applications, our team has a deep understanding of the many small details that can affect successful pre-spin operation design and implementation. Our equipment designs and engineering solutions embody 40 years of pragmatic innovation gained from hands-on experience performing spin tests and industrial spin operations in forging pre-spin work:

  • TDI offers a high-performance drive control system built based on the latest PLC technology and TDI’s 1160 Precision Digital High-Speed Tachometer. The 1160 tachometer, built on a 16-bit digital technology platform, allows for fast and reliable speed measurement — thereby ensuring accurate control of rotors in high-rpm spin operations.
  • TDI has performed numerous burst tests for different types and sizes of rotors. With years of experience and an accident-free record for many decades, we’re proud to offer the industry’s most robust risk mitigation services against high-energy disk bursts.

For help designing a facility, production processes, and spin tooling, contact us today. Our team can provide the necessary training and expert assistance needed to implement a highly successful operation.

Test Devices 2018 Year in Review

2018 has been a banner year for Test Devices, with expansions in both our facilities and our services, allowing us to better serve our customers as a “dependable partner” and a convenient “one stop shop”. Some of our new and expanded service offerings include in-house machining, eDrive spin testing, and expanded balancing capabilities – thanks to the acquisition of a new Schenck balancing machine.

Facility Updates 

Test Devices’ latest facility upgrade brought significant improvements to our shipping and receiving departments and upgrades to our climate-controlled precision inspection room, which includes the expansion of our Quality Inspection team and the acquisition of a new larger CMM (coordinate measuring machine).

The redesigned facility layout, added floor space, and new equipment allowed us to streamline our workflow and enables us to work more efficiently than ever before. The new shipping and receiving departments are now located to the front of the building with an expanded floor space, and optimally equipped handling areas with additional cranes and staged operations. This new layout minimizes unnecessary movement, creates easier access and an unobstructed flow of materials.

We have also expanded our equipment build area and relocated it to a new section of our facility. This move allowed for a more efficient staging of equipment builds and assembly operations capable of preparing three to four machines simultaneously.

Semi-Finish Machining

As of June, Test Devices now offers in-house semi-finish machining services for aerospace turbine disks. For over a decade, TDI has served leading jet engine OEMs who require forging pre-spinning services—a vital part of producing nascent engine disks that offer the highest performance. While a seemingly simple process, this service is deeply specialized, demanding the highest knowledge and skill level to produce a seamless operation. This newly added machining capability will vertically integrate operational steps and allow TDI to offer more expeditious and higher quality services. By the end of 2018, TDI is on track to ship over 100 semi-finished forgings.

Expanding Aerospace Grade Balancing Services

In 2018, Test Devices grew our balancing capabilities by acquiring a new HM 20 Schenck Horizontal Balancing Machine to support the growing demand for these operations. This high precision, state-of-the-art machine allows TDI to service a broader range of customers with varying rotor balancing needs.

Among the primary benefits of the HM 20 is its hard-mounted bearing design, ensuring rapid changeovers between rotors, which allows Test Devices handle significantly higher volumes of balancing jobs and increase the efficiency of our operational capabilities. The HM 20’s modular design also allows it to be easily modified.

Growth in eDrive Spin Testing Systems

The successful completion of an increasing number of proof and burst tests and 130,000 LCF cycles in 2018 attests to the growing demand for eDrive testing.

We are continuing to enhance our testing and engineering offerings to support eDrive customers in 2018, including advanced rotor growth mapping, high-resolution, high-speed video imaging, expedited fatigue, LCF tests (with RT-CDS and growth mapping), heated spin tests, unbalance budgeting and rotor design engineering support.

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2019 and Beyond

Test Devices Inc. continues to build our services and capabilities in 2019 and we look forward to offering better services for new and existing clients in the aerospace, automotive, and other highly technical industries. We will keep leading the industry by offering the latest services and technology.

To learn how our spin testing, balancing, and other services can help your R&D efforts, prototyping, or manufacturing operation, contact us or request a quote.

The Value of Fatigue Testing

Fatigue Testing

Fatigue testing is a crucial procedure used by engineers and technicians to help predict the durability of a part or component under its operating conditions. To appreciate the value of fatigue testing, it is essential to first understand the phenomenon.

Fatigue is a type of structural damage prevalent in cyclically loaded structures. The fatigue is characterized by an initiation and growth of cracks that will eventually result in a catastrophic fracture of a material. Unlike the structural failure caused by an overload, fatigue damage develops under the magnitude of the stresses below the material’s yield strength, and therefore tends to covertly manifest without deforming or showing obvious “warning signs”. The rate at which a fatigue crack grows is dependent on the material’s properties as well as the intensity and cycle frequency of the applied load.

Fatigue testing is used to evaluate a material’s (and component’s) structural durability by testing and analyzing its ability to withstand cyclic loading conditions.

Fatigue Testing Methods

There are different types of fatigue testing machines with various capabilities, ranging from automated material specimen tensile test machines to large full-scale structural test rigs. In a rotating structure, such as gas turbine disks and blades, accurately capturing the loading conditions in fatigue-prone features can be a complicated challenge. Rotors often have intricate geometries to serve its intended functions and these features are subject to varying degree of multiaxial stresses caused by the CF load, which also changes over the course of the operating cycle of the machine as rotor speed changes. These loading conditions are difficult, if not impossible, to capture in test methods other than spin testing.

Within the rotor specific testing techniques, Test Devices Inc. is specialized in performing different variants of LCF (Low Cycle Fatigue) and HCF (High Cycle Fatigue) tests.

The LCF regime is characterized by a higher load application, within the material’s elastic-plastic range, at low frequency (or cycle rate). For example, the take-off and landing cycle of an airplane. Typically, the HCF regime is characterized by the application of a very high-frequency load which results in a rapid accumulation of fatigue damages in a short span of time. These conditions are found in the vibrating vanes or blades subject to resonance.

Both LCF and HCF are common issues in the operation and safety of critical rotating components. Unexpected failure of rotors, such as high-speed impellers and turbine engines, which operate under high centrifugal forces often end in a catastrophic effect.

Benefits of Spin Fatigue Testing

Fatigue testing is performed to generate the data needed to validate and/or refine a probabilistic model of the components’ life in its operational environment. The way the fatigue damage initiates and develops in a material can be influenced by various factors including the loading field cycle pattern, axiality, temperature and environmental factors (e.g. oxidation and corrosion).

The result of the fatigue test data helps to define the maintenance and repair cycle requirements and the safe operating life of machines. These will have a significant impact on the cost of ownership of the equipment as well as safety-related issues.

Test Devices specializes in providing the most relevant test data to our customers who design and develop the advanced machines that are critical to our transportation, infrastructure, and national defense.

Spin fatigue testing can be used in any industry or application where the durability and integrity of a rotor and rotating component matters. Some industries that regularly use fatigue testing and fatigue testing machines include:

  • Automotive – turbochargers, tires, and wheels
  • Aerospace – jet engine components, turbine rotors, wing materials
  • Medical – prosthetics, implants,
  • Apparel – athletic shoes, textiles
  • Construction – bolts, fasteners, reinforcement bars

Learn More From Test Devices, Inc.

At Test Devices Inc., we offer both low-cycle and high-cycle fatigue spin testing services for clients who work with high-speed rotating components in demanding environments. We are capable of testing various complex and cutting-edge machinery parts for jet engines, electric motors, turbomachinery, and energy storage systems.

Our qualified and experienced engineers are willing to assist you in fatigue testing your unique part or component. If you would like to learn more about our testing services, feel free to contact our support team today.

Spin Testing for eDrive Components

Propelled by political, technological, and economic factors, growing global demand for electric vehicles (EV) has accelerated the pace of development of eDrive systems. Automotive part suppliers are developing an increasing number of sizes and varieties of eDrive systems to meet the rising number of EV models offered by all major automotive manufacturers across the international market. This development and validation of reliable electric motors is a critical part of the eDrive system.

Offering a full range of spin testing services (outlined below) to meet clients’ developmental testing needs, Test Devices is an integral partner to our eDrive spin testing customers.

As part of a developmental test program for a major eDrive manufacturer, we recently concluded 50,000+ heated cycles on a series of electric motor rotors in an effort to verify cyclic fatigue life. In addition to cyclic fatigue testing, the test program also involved a series of overspeed and burst tests to validate structural integrity.

Spin Testing from Test Devices, Inc.

With an eye on quality services and constant innovation across everything we do, our Test Devices team consistently strives to provide timely and efficient services to better meet our customers’ needs. An industry-leading provider of spin testing and balancing services, we look forward to working with customers developing eDrive systems.

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For more information on our eDrive spin testing services, or to discuss how we can help with your specific testing needs, contact the team today. We’re on hand to answer any questions you may have.

TDI On Track for Growth in eDrive Spin Testing Systems

As the race for improved electric drives for electric vehicles, drones, and hybrid drive/propulsion systems accelerates, the need for testing of rotors used in high-speed electric motors is also on track for growth.

Test Devices Inc. (TDI) is pleased to begin offering detailed rotor growth testing as well as a variety of other types of spin tests and expert services to aid in the accelerated development of your high-speed eDrive motors.

Why Spin Test with Test Devices Inc?

The engineering challenges faced by the high-speed electric motor industry parallel those of the jet engine industry. The need to understand rotor stresses and expansion behavior in order to accurately engineer reliable and dependable machines is a problem both sectors face. For more than 40 years, TDI has played an important role in helping industry-leading aerospace companies devise the proper tests required to study and better understand the growth of turbines and compressor disks.

In tandem with detailed rotor growth testing, additional spin test options and expert support may also assist in the development of your high-speed motors:

  • Detailed rotor growth mapping

This advanced growth measurement technique developed by Schenck is now available at TDI. This method maps the detailed contour of high-speed rotors, accurately capturing variations in a rotor’s geometry as it deforms under spinning conditions. See Figure-1 above for an example.

  • Burst test and high-speed video imaging

These tests enhance understanding of the failure limit and failure mode of the rotor. Accurate growth measurement and high-speed video data helps engineers calculate the structural stability of the rotor and its failure mode.

  • Fatigue, LCF test (with RT-CDS and growth mapping)

Fatigue and Low Cycle Fatigue (LCF) tests are useful in studying operational cycle fatigue and rotor durability. TDI’s proprietary Real-Time Crack Detection System (RT-CDS) immediately detects fatigue cracks as they happen and halts the test to preserve the damaged rotor before it disintegrates. RT-CDS enables customers to know the exact location and timing of fatigue damage, alleviating the need for painstaking failure investigation work.

  • Heated spin test

Thermal management is one of the key concerns in high-speed motor designs. Operating temperature affects material strength as well as the size of the air gap necessary for cooling airflow and accommodating rotor growth due to thermal expansion. Depending on the materials used to construct the rotors, their behavior may vary dramatically when operated at room temperature versus an elevated temperature.

  • Imbalance budgeting

TDI offers an expert design analysis service to estimate the range of imbalance levels presented by a given rotor design. This process involves analyzing the effect of the geometric tolerances of a given part and then estimating the influence on the imbalance of the rotor using a mathematical model to simulate the manufacturing process, while also comparing it to more than 10,000 different combinations of tolerance variations. The output from this analysis provides a probability model of the imbalance in the rotor, which can then be used to tune the design, minimize scatter, and avoid surprises at later stages of your fabrication processes.

Learn More

The recent merger of Test Devices Inc. (TDI) and Schenck Corporation combines the expertise of two of the most advanced leaders in spin testing, balancing, and high-speed rotor engineering. Download our eBook to learn more about why spin testing matters for eDrive systems.

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To learn how our spin tests and other services can help your R&D efforts, prototyping, or manufacturing operation, contact us or request a quote.

Optical Strain Measurement Vs. Traditional Strain Gauging

In mechanical engineering, “strain” refers to the degree and the way a structure deforms under a load. An understanding of the strain behavior, combined with the knowledge of the failure mechanisms of structural materials, allows intricate yet robust designs of modern, high-performance aerospace machines, including rocket and jet engines.

High-speed rotors, such as jet engine parts, are subject to very high stress induced by centrifugal force. The need to lighten the parts to enhance the performance of the engine must be balanced with its durability and structural integrity. Engineers must, accurately and confidently, know the stress/strain state of the rotor to make the critical design decisions.

What Is Traditional Strain Measurement?

Strain gauges are the traditional instruments employed for measuring strain. With this approach, a gauge is attached to the material being tested using an appropriate adhesive. For the purposes of spin testing, the test parts must be modified, and special tooling has to be designed to allow lead wire passages and slip rings or telemetry systems pass data from the rotating parts to the data acquisition system. Strain gauges are laborious to implement and prone to premature failure during the test, resulting in higher overall test costs, schedule overrun and less reliable test data.

Further limitation of the strain gauges is that it is a point measurement and is blind to the behavior of the surrounding strain field behaviors. The readings from a gauge placed on a certain position of a test rotor must be interpreted accurately to perform a meaningful comparison against an FEA model.

Optical Strain Measurement Applications in the Aerospace Industry

Test Devices Inc. has been interested in a non-destructive test and manufacturing process – the Rotating Optical Strain System (ROSS) – for some time. The ROSS is a non-contact strain measurement system which eliminates limitations, is less costly and provides more complete data, possibly allowing the measurement at higher temperatures needed for fully understanding the engine parts.

The ROSS will unlock a wealth of new information for material and component designers. The data is valuable for validating (or refining) the numerical models used in designing jet engine parts and gas turbine rotating parts as well as understanding the details of the failure mechanisms limiting the performance of existing parts.

Combined with advanced spin testing capabilities, Test Devices provides a unique testing resource for civil and military jet engine/propulsion system developers. The ROSS can accelerate the development of advanced materials and manufacturing capabilities across the gas turbine industry. It can provide the most relevant data to reduce risks in currently active turbine engine development programs.

Learn More

Optical strain instruments have been on the market for years, commonly used to measure strain in static objects. But in recent years, they’ve been steadily rising in popularity as more and more industry professionals begin to use them to measure strain in high-speed spin tests.

To learn more about how these optical strain gauges can benefit your testing and production processes, reach out to the team at Test Devices today.

Exciting Facility Updates at Test Devices

As the rate of jet engine part production has rapidly increased and our clients continue to forecast further growth, we’ve become a trusted spin testing & spin process provider. To keep up with rising demand and continue to offer the most cutting-edge services available, Test Devices, Inc. has completed multiple facility expansions in recent years.

So, what’s new at Test Devices, and what do our latest expansions mean for our customers?

Facility and Capability Expansion

Our latest expansion incorporates improvements in both the shipping and receiving department and the equipment build area. We’ve also recently acquired a new coordinate measuring machine (CMM)!

  • Spin Rig Assembly AreaShipping and receiving — To re-engineer the flow of parts coming into and out of our building, we relocated the shipping and receiving department to the front of the building to allow for expanded storage and handling areas along with additional cranes. In addition, the new area includes both plenty of space for trucks to back-in and an adjustable loading dock, allowing our forklifts to directly unload trailers. The relocation and improvements make unloading and loading operations significantly more efficient, contributing to reductions in turn-around time of customer parts.
  • New coordinate measuring machine — To support the needs of our growing forging pre-spin business, we remodeled our climate-controlled precision inspection room, expanded the Quality Inspection team, and added a new larger Zeiss CMM machine.
  • Equipment build area — Because of the volume of recent spin rig orders, the equipment build & assembly area was relocated to a new section of the building. This update allows for new capabilities including improved setup and staging of the equipment builds and the ability to build three to four machines simultaneously. The improved build area also features an updated air supply and electrical supply for building and testing advanced machines.

Learn More

With an eye on quality services and constant innovation across everything we do, our Test Devices, Inc. team consistently strives to provide timely and efficient services to better meet our customers’ needs.

An industry-leading provider of spin testing and balancing services, Test Devices is thrilled to announce these new facility updates, which will allow us to better serve our ever-expanding client base.

For more information on these changes, or to discuss how we can help with your specific testing needs, contact the team today. We’re on hand to answer any questions you may have.

Low Cycle Fatigue Rigs vs. Dynamic Spin Rigs

To validate the integrity of rotating parts against centrifugally loaded conditions, spin testing is a critical step to ensure rotor product quality. While the principle of the spin testing appears straightforward, it’s very easy to miss the important subtleties of the testing mechanics. In fact, since the early days of the spin testing, millions of dollars have been wasted and many perfectly good parts have been needlessly destroyed due to subpar testing practices.

Successful spin testing requires participants to:

  1. Focus on the overall test objective – Which rotor features will the test assess, and under what conditions?spin rig comparison
  2. Understand the test part – How is the test part being assembled in relation to adjoined parts in the actual operating environment? How will it interact with those related components, how will those interactions mechanically or structurally constrain the test part while under assessment, and how is the spin tooling designed to accurately represent the condition?
  3. Recognize what to test for and what results will indicate – What measurements must be taken? How should these measurements be captured so that the resulting data is useful in understanding the failure mode, validating the engineering models, and updating the part design accordingly?

Beyond the basics, spin testing can also be used to validate the durability of the rotors in more a realistic environment. Doing fatigue assessment in spin testing allows engineers to study part durability by using actual production parts (or modified versions), which would be more representative test specimens than coupons in terms of geometry, size and manufacturing process. Additionally, the loading condition resulting from the spinning would create realistic stress conditions, specifically related to the multi-axial loading field and the loading cycle.

Test Devices, Inc. (TDI) and Schenck offer two different types of spin rigs for advanced fatigue assessment tests: a Low Cycle Fatigue Rig (LCF) and a Dynamic Spin Rig (DSR). Each style of rig is designed to accommodate specific testing requirements.

  • Low Cycle Fatigue Rigs are designed to perform various low cycle fatigue (LCF) tests, which are typically used to evaluate the overall durability of parts in terms of usage or operational cycles. For example, for a jet engine for a commercial airliner, this would be based on the number takeoff and landing cycles for a specified flight path.
  • Dynamic Spin Rigs, on the other hand, are designed to test the dynamic properties of the rotor parts and its high cycle fatigue (HCF) related failure modes. The HCF is a fatigue failure mode driven by the resonance of a part; for example, turbine blades may have resonances within an operating speed range that have modeshapes tied to incipient and rapid fatigue damages/failures.

Low Cycle Fatigue (LCF) Rigs for Dependable and Realistic Testing

test devices and schenck logosTDI offers unmatched performance and reliability in its advanced LCF test spin rigs. Featuring robust armor cylinders to ensure safety, a drive system with the rapid cycle time to expedite test schedules, and accurate cycle speed control system to hit cycle targets, the rigs have been continuously proven over Test Devices’ more than 40 years of testing experience.

Combined with various automated testing features, Test Devices’ LCF rigs boast the highest-productivity drive systems available. These rigs typically incorporate a range of standard features, including:

  • Custom data acquisition system to record all test data
  • TDI’s proprietary crack detection system technology
  • Containment chamber designed to withstand high-energy burst failures
  • Vacuum system to eliminate aerodynamic losses and friction heat
  • Automated control system to perform various LCF test speed profiles
  • High performance drive systems with RPM capabilities of up to 250,000 rpm

In addition to these features, LCF rigs can also be equipped with elevated temperature test capabilities, such as:

  • Isothermal – Uniform temperature on the test rotor
  • Thermal gradient – Capability to map the realistic “engine-like” rim-to-the bore temperature profile on the rotor

Dynamic Spin Rig (DSR) for Advanced Turbine System Research

High cycle fatigue (HCF) failure typically occurs during the critical phase of an aircraft’s operations, such as during the take-off for commercial airliners or rapid throttle changes in military aircraft. While the duration of an HCF-inducing condition exposure could be brief, the damage often develops rapidly before reaching a critical level. In most cases, there is no opportunity for correction once the condition reaches this point.

DSR was developed to allow engineers to test and validate the dynamic property of bladed rotors at the component level, therefore minimizing test costs while still retaining the realism in the test. DSR are equipped with the capability to excite the bladed rotor with a desired dynamic load (of an Engine Orders, or EOs). The spin testing condition incorporates the effect of the centrifugal load on the test parts, which is known to affect its damping and resonance properties – this unique test element cannot be accurately replicated by traditional table-top methods.

Test Device’s DSRs are equipped with unique testing capabilities, which include but are not limited to:

  • Proprietary high-precision tachometer & the rpm control system to “lock on” to the target resonances
  • Oil-jet and aero-pulse blade excitation systems
  • Multi-point strain gage & slip ring (or telemetry) systems
  • No-contact Stress Measurement System (NSMS), which is also known as the Blade Tip Timing system

Testing Rigs from Test Devices

With years of experience working with cutting-edge spin test rigs, Test Devices, Inc. is proud to provide testing services utilizing both low cycle fatigue and dynamic spin rigs to customers. To learn more about our LCF and DSR spin rigs, or to discuss options for your specific application, request a quote from the team today.

Two Things to Look for in Your Spin Testing Service Provider

test devices inc control roomNot All Spin Tests Are Created Equal – Know the Risks

Spin Testing has been used in research & development to validate the design and the integrity of rotating components, as well as in manufacturing to process a large volume of rotating components before delivery to customers. These two applications of spin testing are vastly different in terms of set-up, output, and end goals, but there are some key common threads across all spin tests.

No matter what kind of spin testing you’re doing, there can be HUGE negative business repercussions if they are not carried out carefully, under the correct supervision, and with the correct knowledge base behind the test.

In this blog, we’ll cover two major areas that a spin test end user needs to be aware of when evaluating a potential spin testing service provider.


Control of Rotational Speed

Controlling speed is a critical component of a successful spin test, but the importance of achieving a precise test speed is not always immediately obvious to many end users.  While achieving a target rotational speed in a spin test may sound like a simple “given”, the truth is that it requires diligent work and attention to the detail.

What Happens When Rotational Speed is Inaccurate?

The data measured from engineering tests, such as a spin test, will be used to make some important decisions on the integrity and the durability of safety critical parts. The consequences of decisions made on erroneous data are serious.  In the event speed data is collected incorrectly, the overall integrity of the part can be at risk.

In most cases, bad engineering data could lead to incipient issues such as non-conformances, but it could also lead to a more serious scenario. For example, in a development of aviation jet engine, spin test results have been used to validate the cyclic fatigue durability of the rotating components.  A low cycle fatigue test (LCF) involves executing a specific rotor speed cycles over tens of thousands of iterations. The relationship between the stress caused by the centrifugal load and the fatigue life of a disk material is logarithmic, meaning a small difference in the stress (the speed) multiplies to a much larger difference, often an order of magnitude, in the resulting fatigue life values. The consequence of the difference could affect the decisions made regarding schedule and the requirements for the parts maintenance and replacement cycles, and in a more serious scenario, a premature failure of the parts when erroneously optimistic conclusions were drawn on the durability of parts.

The criticality of accurate speed data is equally important in a production environment. When a part is spun to an incorrect speed, it is often impossible to catch that via a post-test inspection. The quality of the output must be guaranteed and validated at the process step. An erroneous spin process could not only falsely “validate” parts, but also subject the component to damage.

What Can You Do to Ensure Rotational Speed is Correct?

Ensuring accurate and consistent control of spin test speed is of paramount importance for Test Devices. Designing a precise speed control system starts with being able to measure its performance precisely. Test Devices has designed and developed high-resolution precision tachometers for high-speed spin testing. Many commercially available tachometers lack the resolution, preciseness, and consistency necessary for many spin testing applications.

As a designer and a developer of the most advanced spin testing equipment, Test Devices understands the properties of spin testing equipment, including high-speed drives, to a minute detail. Combining the expertise with over four decades of spin testing experience, we developed and continue to evolve our spin test speed measurement and control solutions.

Further to the use of cutting-edge technology, Test Devices audits the test data, of all tests, to ensure its quality conformance. Understanding the importance of the engineering information we provide, as a part of our operational process Test Devices records and reports the results of the spin test (or manufacturing spin process) for every part we handle.


Quality Control and Part Handling

Spinning a part is only a step in the whole process involved in testing (or in a manufacturing spin process). The handling of your rotating components is another area that end users may often underappreciate. The mishandling of parts, and the lack of proper records of incidents can have a catastrophic impact on customer businesses overall.

What can happen?

Test Devices, Inc has seen a fair share of rotating parts that enter our facilities toting obvious signs of mishandling from previous testing services. When a part is mishandled, there is the obvious risk of the part being damaged beyond repair, and need to be scrapped. However, some damage can be so subtle, that it can go undetected and either:

1) Result in erroneous test results bad data, leading to  inaccurate conclusions about the capabilities of the component

2) Lead to total part failure later on in subsequent use after the part is assembled into the final product

spin pit debris

What Can You Do To Ensure Quality?

At the very minimum, customers should look for spin testing service facilities that conform to the up-to-date standards of AS9100 and ISO9001. It is also highly recommended that customers conduct an independent audit of vendor processes to make sure they are properly controlled according to standards. Customers should also ask potential vendors about their experience with similar projects, do research on staff experience & credentials, and review their quality processes and systems before entering into a contract.

Learn More

Interested in learning more about what other factors can disrupt your spin testing operations? Download our ebook, “Spin Testing for Manufacturing 101” for a full breakdown of what you need to know about spin testing in the manufacturing realm.