What Is Rotor Balancing and Why Is It Essential?
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Rotors are a critical component used to convert electric or electromagnetic energy into rotational motion. For rotors to operate reliably, they must maintain even weight distribution across the rotational axis. Too much weight on one side creates uneven mass distribution known as “unbalance”.
Rotating parts in any mechanical assembly can become unbalanced. Uneven weight distribution of a rotating component causes the part’s rotational center to be out of alignment with the geometric axis. When unbalance occurs, the operational efficiency and safety of the system in which the rotor operates are compromised. Rotor balancing can help to prevent issues caused by unbalance, reducing noise and vibration and extending the life of your system.
What Are the Various Rotor Groups?
Rotors are grouped into two categories: rigid and flexible. Rigid rotors can be balanced at lower speeds, as long as there is sufficient centrifugal force to detect the unbalance. Flexible rotors, on the other hand, deflect outward from the rotational axis, and the center of rotation moves away from the rotational axis as the speed increases. Unlike rigid rotors, flexible rotors must be balanced in stages, starting with lower speeds and slowly working up to operating speed.
Why Is Rotor Balancing Essential?
High levels of vibration caused by unbalance can cause equipment to operate less reliably, which results in increased energy usage, decreased operational efficiency, and reduced equipment service life. The force exerted by the dynamic load from an unbalanced rotor will cause wear to the rotor itself, the bearings and mountings holding it in place, and the machine’s structural support. Although the severity of the dynamic load varies depending on the degree of unbalance and the rotation speed, any unbalance can cause problems.
Vibration from an unbalanced rotor creates excessive noise and resonance, which will ultimately compromise the structural integrity of the equipment that supports the rotor assembly. The damage caused by unbalance is especially apparent in bearings, suspension equipment, support housing, and the equipment foundation. These components are typically exposed to the highest level of stress caused by the excess dynamic load due to unbalance. With ongoing exposure, these components will be more likely to suffer premature wear.
In addition, the high vibration caused by unbalance can loosen fasteners such as screws, nuts, and bolts, rendering the structure less stable. Pipes, electrical cables, wiring, electrical connections, and switches can also be negatively affected. With extended exposure to high levels of vibration, even nearby equipment and structures can be compromised, creating the potential for greater damage and injury.
What Are the Various Types of Unbalance?
When balancing your rotor, it is critical to understand the different types of unbalance. There are three types of unbalance, including:
- Static Unbalance: This type of unbalance occurs when the mass axis is displaced parallel to the shaft axis. Static unbalance is corrected only in one axial plane.
- Couple Unbalance: Couple unbalance occurs when the mass axis intersects with the running axis. This type of unbalance is typically corrected in two axial planes.
- Dynamic Unbalance: Dynamic unbalance is typically a combination of static and couple unbalance and occurs when the mass axis does not intersect with the rotational axis. This can usually be repaired by correcting the balance along two axial planes.
Contact Test Devices by SCHENCK
At Test Devices by SCHENCK, we are dedicated to providing our customers with expert balancing solutions for rotating and oscillating equipment in a wide range of applications and industries. With more than 50 years of experience, we have the knowledge, equipment, and skill necessary to provide superior balancing services for everything from modular drills to industrial crankshafts and wind power turbines. We are skilled in servicing equipment of all sizes, from miniature dental motors of only a few ounces to 400-ton steam turbine rotors.
Our expertise extends to dynamic balancing, static balancing, couple balancing, and much more. With an international team of over 900 experts, we work tirelessly to design, research, develop, and produce actionable balancing solutions for customers in the automotive, aerospace, electrical, and mechanical engineering industries. In addition, we offer maintenance services and quality control testing to ensure that your rotor equipment is operating within applicable industry standards and regulatory guidelines.
We are committed to providing superior rotor balancing services to our customers around the world. To learn more, contact us today.
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Test Devices by SCHENCK Sponsors Award-Winning WPI Rocket Team
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As part of our commitment to promote STEM, Test Devices by SCHENCK has been a proud sponsor of the Worcester Polytechnic Institute (WPI) High Power Rocketry Club. This student organization runs educational workshops on topics such as rocketry and robotics and also enters intercollegiate engineering competitions. Recently, the team has been winning impressive awards and gaining visible results.
What is the WPI HPRC?
The WPI HPRC is Worcester Polytechnic Institute’s High Power Rocketry Club, a student organization dedicated to rocket engineering and STEM education. A large portion of the club’s time is devoted to pursuing hands-on learning as they design, build, test and launch sounding rockets. The HPRC also believes that taking part in high-level competitions is an important aspect of cultivating technical expertise in the next generation of engineers.
Participating in rocketry competitions allows this group to develop a more in-depth knowledge of the engineering design process. HPRC members come from diverse backgrounds and disciplines and are able to channel their unique experiences into engaging collaborative projects. Over the years, club interest has grown and today the HPRC includes a member base of over 200 students. Every member actively participates in managerial or technical tasks, fostering an inclusive and engaged educational environment. An important aspect of the HPRC is to cultivate leadership skills as they work as a team in a professional and intense goal-oriented atmosphere for students to navigate.
WPI’s Competition Journey
WPI’s High Power Rocketry Club originated in 2018 with the founding of the WPI University Student Launch Initiative (USLI). That year, WPI’s team competed in NASA’s annual USLI competition. Enthusiastic student response led to the first competition rocketry launch the following year with Project G.O.A.T.S. The goal for this launch was a target apogee of 4,094 ft.; however, failure occurred at 800 ft.
After a year of delays due to the COVID-19 pandemic, WPI re-entered the competition scene in 2021 with a new and improved rocket for Project Sirius and Polaris. This project’s test bed launch was instrumental in preparing for the team’s most demanding competition yet, the 2022 Spaceport America Cup’s Intercollegiate Rocket Engineering Competition. Hosted by the Experimental Sounding Rocket Association, 158 teams from 24 countries participated in the world’s largest intercollegiate rocket engineering competition.
At this event, nearly 2,000 students from around the globe gathered to share their passion for high-power rocketry. In 2022, WPI’s rocket team experienced launch failure at this event, they used lessons learned from the setback to improve their rocket design and came back with more skill than ever before in 2023.
Today, with only five years of operational experience, WPI has obtained advanced technical aptitude and emerged as a leading competitor in the world’s most challenging rocketry competitions, like the SAC IREC. In 2024, the team plans to compete in the 10K Solid Commercial Off-the-Shelf Division at the SAC IREC. Their mission is to launch the team’s high-power rocket and payload system to an apogee of 10,000 ft. with another successful recovery.
Competition Success and Awards
Throughout HPRC’s history, they have experienced many impressive achievements and awards. Each year as they participate in challenging international competitions, they demonstrate an impressive dedication to engineering excellence. The team has attended the Spaceport America Cup’s Intercollegiate Rocket Engineering Competition (SAC IREC) annually since 2021, collecting new awards each year. Their past competition successes include:
- SAC IREC 2022 Team Sportsmanship Award
- SAC IREC 2023 3rd Place Payload Challenge Award, Space Dynamics Laboratory
- SAC IREC 2023 Jim Furfaro Award for Technical Excellence
Most recently, in 2023, the club obtained 2.64% within their 10,000 ft. target apogee. This feat allowed them to beat out over 100 internationally competing teams to win two awards for technical achievement. As a platinum-level sponsor, Test Devices by SCHENCK is proud to support the WPI HPRC and its efforts to foster engineering excellence in our local community.
Learn More About Test Devices by SCHENCK: Leading the Way in Rotational Parts
At Test Devices by SCHENCK, we’re passionate about innovative technology and work continuously to advance the science of rotational testing. Taking part in community outreach programs is an important part of this mission. In addition to supporting WPI’s rocketry team, we also host local students for aerospace industry events. Here, we share knowledge about our work, promote STEM education, and inspire the next generation of scientists and engineers. Explore our website to learn more about what we do and contact us with any questions. If you have a project you’d like to work with us on, request a quote today.
The Value of Fatigue Testing
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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 this testing service.
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
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.