High-Efficiency Fatigue Testing: Resonant Versus Servohydraulic
Fatigue strength testing for components and materials—a crucial requirement in a wide variety of industries—is traditionally supported using a servohydraulic testing machine. While they can get the job done, this equipment design is associated with high energy usage and substantial maintenance needs.
Electromagnetic resonant testing provides an effective alternative across a broad range of use cases. More and more organizations are adopting this technology because it can offer lower energy consumption and dramatically streamlined maintenance. And while resonant fatigue testing solutions were confined to dynamic testing in the past, the ZwickRoell Vibrophore can also be used for static testing.
In this blog, we explain what Vibrophores are, how they work, and the crucial advantages they offer over servohydraulic testing equipment. Finally, we explore few key features that differentiate Vibrophores from other resonant fatigue testing solutions.
What is a Vibrophore? High-Efficiency Resonant Fatigue Testing Machines
A Vibrophore is a type of resonant fatigue testing machine which utilizes a mechanical resonator paired with electromagnetic drive which generates a dynamic load using this oscillation system. In the past, resonant testing machine applications have been limited to dynamic materials testing (i.e. determining the finite life and long life fatigue). But today, the latest generation of Vibrophores provide static testing as well. The electromagnetic drive of a Vibrophore provides large force amplitudes from a low energy input, allowing them to operate more efficiently than conventional equipment (see below).
Why is electromagnetic resonance so valuable for fatigue testing versus servohydraulic equipment?
Dynamically stressed components in the majority of industries are not only subject to strongly fluctuating, but often also periodic load applications throughout their service life. Representative examples include:
- Drive chains, crankshafts, connecting rods, and timing chains in automotive engines.
- Turbine blades.
- Component testing for casting, forgings, bolts, screws, and studs.
- Concrete and reinforcing steel.
In these types of application, fatigue strength of the component is a crucial criteria. The properties of the materials used are one of the most important drivers of component performance. These properties are tested using a high-cycle fatigue test in tensile, compression, pulsating and alternating load ranges. Additionally, fracture mechanics tests are performed on CT (compact tension) and SEB (single edge bending) specimens. This testing regimen is rounded out with tests for:
- Extended temperature ranges
- Liquid media
- Dynamic torsion and flexure
Traditionally, these requirements have been met using a servohydraulic testing machine. Servohydraulic machines have been used in these applications for decades. And while capable of fulfilling the testing requirements discussed above, servohydraulic machines suffer from several important drawbacks compared to resonance-based testing machines.
Vibrophores provide:
- Dramatically improved energy efficiency: Vibrophores only require about 2% the energy consumption of servohydraulic systems, which reduces costs and environmental impact.
- Simplified installation, with no need for ancillary equipment like hydraulics, or air/water compressors.
- Reduced maintenance: the electromagnetic drive system is virtually wear free, and does not require oil, cooling, water, or complex maintenance procedures.
What makes ZwickRoell Vibrophores different from other resonant fatigue testing machines?
ZwickRoell Vibrophores are available in eight series with test loads ranging from 15 to 1,000 kN (you can learn more about these series on our product page here). Test frequencies up to 285 Hz, ensuring short test times and high specimen throughput. ZwickRoell is the only manufacturer to offer a Vibrophore/resonant fatigue testing solution that goes up to 1,000 kN with an electromagnetic drive.
The key feature of the Vibrophore is the load frame concept. The extremely stiff load frame uses four columns to achieve excellent guidance properties. The controlled average force on the test specimen is applied via the movement of the upper crosshead and two lead screws. The dynamic load is applied via the separately controlled electromagnetic drive. Frequencies from 35 to 285 Hz (eight frequency steps) are achieved by activating/deactivating weights. Operation is convenient and simple using the included testXpert R testing software, with features adapted specifically to electromagnetic fatigue testing precisely adapted to the test tasks. Vibrophores combine full-fledged static testing capabilities with their dynamic testing features—ideal for a laboratory with diverse testing needs or frequently changing test requirements.
For instance, our case study here explores how DEKRA, one of the leading testing services companies in Europe, uses a 2H0 kN Vibrophore for testing concrete-reinforcing steel. Or, if you need help determining the best solution for your fatigue testing needs, we encourage you to reach out to our testing experts using the form below.