What is the difference between fatigue testing and impact testing?

Fundamentals of impact testing and sensor requirements

Impact testing evaluates structural behavior and energy absorption under short-term, high-amplitude impact loads. Common methods include drop towers, pendulum impact tests (Charpy and Izod), ballistic penetration tests, and crash barriers.

In impact measurement technology, the focus is shifting from long-term cyclic load capacity to the precise acquisition of transient signals. The force transducer must be able to detect rapid rise times without oscillation, structural damping, or overload. Transducers in impact test rigs are frequently subjected to off-axis forces, strong deceleration shocks, and short-term overloads that far exceed their actual measuring range.

• Sensor selection: Force transducers, high-capacity Multi-axis sensors (e.g., 3-axis and 6-axis sensors), robust Miniature pressure measuring cells as well as high-frequency Force measuring discs are designed for high natural frequencies and the detection of peak forces.
• Requirements for measurement technology: High-speed data acquisition systems (such as the BX8 Multi-Channel DAQ) with sampling rates between 100 kHz and 1 MHz per channel and analog low-pass anti-aliasing filters to avoid spectral overlap.

More information can be found under Impact Testing for Millisecond Evaluations.

Industry applications compared: Fatigue versus impact testing

Automotive Industry

• Fatigue application: Wheel suspension links, stabilizers, and engine mounts are installed on multi-axle hydraulic fatigue test rigs that undergo millions of road load cycles. Engineers use fatigue-tested low-profile force transducers to continuously monitor tensile and compressive loads without calibration deviation.
• Percussive application: Front Crash barriersSide intrusion beams and bumper systems undergo high-speed collision tests. Engineers instrument the crash barrier with force transducers and high-speed data loggers to record force dissipation and energy transfer in the millisecond range.

Aerospace and defense

• Fatigue application: Wing-fuselage connection fittings and structural components of the Landing gear They undergo complete fatigue lifetime validations using fatigue-tested force transducers over hundreds of thousands of simulated flight hours.
• Percussive application: Wing leading edges, turbine cowlings, and cockpit windows are inspected for foreign object damage (FOD) and bird strikes. High-capacitance force transducers and multi-axis sensors measure the instantaneous impact forces during high-speed projectile impacts.

Medical Devices

• Fatigue application: Knee and hip joint implants undergo ISO 14243 and ISO 7206 wear and fatigue testing protocols at 1 to 5 Hz for 10 million cycles in physiological fluid. Sealed, fatigue-tested force transducers continuously measure changing axial and torsional loads.
• Percussive application: Surgical orthopedic instruments, bone nails and ceramic femoral heads are tested on drop towers to quantify their fracture strength under sudden drop or hammer impacts using high-frequency miniature force transducers.

Renewable energies

• Fatigue application: Fastenings of the wind turbinesRotor blade roots, pitch bearings, and tower foundation bolts are subjected to millions of alternating aerodynamic and rotational load cycles. High-capacity, fatigue-tested low-profile force transducers and bolt monitoring sensors measure continuous tensile-compression cycles through extensive structural validation tests.
• Percussive application: Yaw stops, emergency braking mechanisms, and wind-gust-induced blade deflection buffers must cope with abrupt, strong shock stops during sudden net heave or strong wind braking events. High-capacity pressure transducers and multi-axis force sensors detect these short-term peak load profiles to verify mechanical catch thresholds.

Heavy cargo, marine and shipping

• Fatigue application: Mooring lines, submarine supply lines and Crane systems at docks They are subjected to continuous cyclic tensile stress over many years due to constant wave action and sea state. Hermetically sealed, fatigue-tested tension members and underwater load bolts monitor the load profile to prevent corrosion-induced fatigue failure in seawater.
• Percussive application: Underwater anchor halyards, dynamic positioning winches, and collision protection systems on ship fenders are subjected to extreme, instantaneous shock loads during anchoring, recoil events, or docking. Robust, submersible, high-capacity Load bolt and pure pressure measuring cells They capture peak impact forces in the microsecond range to assess shear stress limits and prevent catastrophic structural failure.

Three practical considerations depending on the type of test

When configuring a test system, engineers must precisely match the sensor physics to the specific load profile. Interface presents the test types frequently associated with force and torque measurement in the categories "Types of Test Applications with Force Transducers" and " Further Test Types with Force Transducers ." The following are the most important considerations for each test profile.

#1 – Frequency response

Fatigue tests on servohydraulic or electrodynamic test frames typically run between 1 Hz and 100 Hz, where standard strain gauge excitation and filtering function reliably. Impact events occur in the sub-millisecond range and require sensors with a high resonant frequency to prevent the sensor's mass-spring dynamics from distorting the actual impact signal.

#2 – Mechanical overload protection

Impact testing devices require a sensor capacity significantly higher than the expected nominal peak value to handle unexpected impact peaks without permanently deforming the spring element. In fatigue tests, the sensor's permissible fatigue capacity must equal or exceed the maximum cyclic stress range to prevent premature internal failure.

#3 – Data Synchronization

Multi-channel fatigue monitoring relies on continuous recording, trend tracking, and threshold triggering. Impact detection, on the other hand, requires pre-trigger buffering, precise threshold activation, and synchronized analog-to-digital conversion across all strain, acceleration, and displacement channels simultaneously.

Conclusion: Fatigue versus impact in plain terms

Fatigue and impact testing require different approaches to sensor specification. Fatigue applications demand force transducers with low internal stress and measurement technology optimized for long-term zero-point stability over millions of continuous cycles. Impact test benches, on the other hand, prioritize high natural frequencies, transient overload capacity, and fast-sampling DAQ architectures that capture energy transfer in the millisecond range without distortion.

Precise matching of sensor design, natural frequency, and data acquisition speed to the specific mechanical load profile ensures measurement accuracy and protects the measuring equipment from premature structural failure. Contact our application engineers to find the right sensor and measuring technology for your testing project.