Fatigue testing plays a critical role in understanding how materials and components perform under repeated loading over time. Because real-world applications rarely involve a single static load, fatigue testing systems must accurately replicate cyclic conditions across a wide range of forces, displacements, and frequencies.
Selecting the right system requires careful evaluation of these parameters, along with considerations around control, durability, and measurement accuracy. This guide outlines the key factors that influence system performance and will help you choose a fatigue testing solution aligned with your application requirements.
What Factors Come Into Play When Choosing a Fatigue Testing Setup?
Force Requirements Determine Frame Design and Measurement Needs
- High cyclic forces can induce stress, vibration, and deflection in the frame, leading to a loss of accuracy, or premature failure of the machine itself. In order to prevent this, a fatigue testing system must have sufficient frame stiffness to ensure forces are accurately transferred to the specimen without mechanical degradation or loss of measurement integrity.
- Fatigue testing requires the system to operate across a defined load range, not just a maximum force. The machine must reliably achieve both minimum and maximum loads throughout each cycle, as defined by the stress ratio (R-value).
- 0<R<1 for Tension-to-Tension
- R>1 for Compression-to-Compression
- R<0 for Tension-to-Compression
- R=-1 for Fully Reversed Loading
The load cell must be capable of accurately measuring the full range of forces present in the test while remaining properly sized for the required resolution. Selecting a load cell with sufficient capacity prevents sensor damage or failure under peak loads, while an oversized load cell can reduce measurement sensitivity and compromise the ability to capture smaller dynamic load variations.
Why ADMET?
ADMET systems feature high-stiffness load frames that minimize deflection under cyclic loading, while maintaining accurate force transfer across the full load range to ensure reliable R-value control.
Force, Stroke Length, and Test Frequency Determine Actuator Design
- For forces less than 20 kN an electromechanical actuator may be used. Forces greater than 20 kN require a hydraulic actuator. Frequencies greater than approximately 20 Hz require a linear motor or hydraulic actuator.R=-1 for Fully Reversed Loading
- The distance (or displacement) traveled in one fatigue cycle is central in designing the drive train for a fatigue testing machine:
- Higher displacement amplitudes, particularly at elevated frequencies, require the actuator to move faster, which significantly increases power consumption. As a result, hydraulic systems may demand higher flow rates, while electromechanical systems may require higher-torque motors.
Why ADMET?
With ADMET, both electromechanical and servo-hydraulic systems are engineered to align the actuator design to your exact stroke and displacement. This ensures motion that matches real-world conditions, so your tests perform precisely as your materials will in the real world.
Maximum Frequency and Displacement Amplitude Determine Max Speed
- As speed and power increase, so does heat generation in the actuator and specimen. Without proper system design and cooling, this can impact measurement accuracy, reduce component life, or lead to premature specimen failure unrelated to true fatigue behavior.
- High-cycle fatigue tests (10⁶–10⁷+ cycles) can take impractically long at low frequencies. Increasing test frequency allows these tests to be completed in days instead of months, but only if the system can deliver the required speed and power without sacrificing control or accuracy.
- Max Speed = Amplitude* 2 *(π*frequency) → Max Force and Max Speed determine required power (Power = Force * Speed)
Why ADMET?
ADMET sizes actuator speed and power to meet your desired test frequency, with capabilities up to 100 Hz. Actuator sizing, control electronics, and system mechanics are selected to achieve the target frequency under full load while maintaining measurement accuracy and reducing system wear for extended operating life.
Material Type and Dimensions Determine Fixturing Approach
- With elevated test speeds, fatigue tests can be especially susceptible to invalid failures caused by sample slippage, misalignment, and stress concentration.
- Design factors related to clamping mechanism, clamping force, jaw surface texture, alignment, and articulation can all be adjusted to ensure failure occurs within the specimen gauge section.
- Depending on specimen type, customized grips or fixtures are often required to ensure failures are valid and results are accurate.
Why ADMET?
ADMET applies a diagnostic approach to fatigue testing, engineering gripping solutions and accessories based on your material properties and specimen geometry. Through this engineer-led process, each system is configured to ensure precise alignment, accurate results, and compliance with relevant test standards.
Maintenance and Calibration Ensure Machine Longevity
- Regular calibration is essential to maintain data integrity over long-duration fatigue tests. High-cycle testing introduces component wear. Periodic calibration ensures measurements remain accurate and reliable.
- Fatigue tests can run for days or weeks, and unexpected failures can interrupt testing and result in lost time. Periodic maintenance and inventorying of critical spare parts are key in minimizing downtime.
Why ADMET?
ADMET configures fatigue testing systems for long-term performance, supported by an established network for calibration, preventative maintenance, and service. This ensures measurement accuracy, minimizes downtime, and extends machine longevity, no matter where your facility is located.
By: Hazel Salazar | Published on: May 20, 2026 | Last Updated: June 25, 2026
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