FATIGUE TESTS

Fatigue Test: How To Do It?

Fatigue testing involves loading a specimen into the fatigue testing machine, applying a predetermined stress, and then unloading it to zero load in the opposite direction until the end of the test. The time for which the test is performed may be predefined by cycles or to the failure of the specimen, as specified by the test parameters.

Fatigue Testing Is Carried Out For Several Purposes.

The principal purpose of a fatigue test is typically to determine the service life expected in a material under cyclic loading. Besides this, fatigue strength and resistance against cracking are other significant parameters. Fatigue life refers to the cumulative number of cycles a material is capable of resisting under one specific load regime. A fatigue test is also useful to determine the maximum load a specimen can endure for a given number of cycles. All these attributes are of immense importance in industries where materials are subject to fluctuating, rather than constant, forces.

Fatigue of understanding and testing has become very important from car chassis in formula 1 to dental implants while designing the components subjected to cyclic loads. Fatigue tests have helped make predictions regarding the service life and assess the durability of the component through related levels of applied stress, providing assurance about the reliability of materials used across applications.

Materials Under Various Application Types.

• There are several kinds of fatigue test High cycle fatigue test: Standard fatigue test carried out at frequencies ranging approximately between 1 and 5000 Hz.
• HCF (DIN 50100) High cycle fatigue test: Standard fatigue test carried out at frequencies ranging approximately between 1 and 5000 Hz.
• Bending fatigue test on rotating bars, DIN 50113.
• Tensile-compression fatigue tests. Testing strength (fatigue strength) against cyclic stresses using tension, unloading and compression.
• Giga-cycle fatigue test: A fatigue test in which at least 1 x 10^9 cycles or more are applied in a very short time with ultrasonic vibrations, etc.
• Fatigue crack propagation test machine: A machine meant to study the rate of crack propagation under cyclic stresses.

LCF Low Cycle Testing

HCF High Cycle Testing

Most Widely Used Fatigue Tests

• ASTM D3479 – Tension-Tension Fatigue of Polymer Matrix Composite Materials
• ASTM D7774 – Flexural Fatigue Test Equipment for Plastic Materials
• ASTM E2207 – Equipment for Testing Axial-Torsion Fatigue in Thin-Walled Tubular Materials
• ASTM E2368 – Thermomechanical Fatigue Test Equipment
• ASTM E466 – Controlled-Load, Constant-Amplitude Fatigue Testing of Metals
• ASTM E467 – Constant Force Axial Fatigue Test System – Testing Machines
• ASTM E606 – Strain-Controlled Fatigue Testing at High and Low Cycles
• DIN EN 6072 – Aerospace Series – Metallic Materials – Test Methods – Constant Amplitude Fatigue Testing
• DIN 50100 – Controlled Load Fatigue Tests – Performance and Evaluation of Cyclic Tests with Constant Load Amplitude on Metal Specimens and Components
• ISO 1099 – Metallic Materials – Fatigue Tests – Controlled Axial Force Method
• ISO 7206 – Testing of Hip Implants
• ISO 14801 – Equipment for Fatigue Testing of Dental Implants
• ISO 15024 – Testing Machines – Interlaminar Fracture toughness Testing of Plastic Composite Materials
• ISO 22675 – Facilities for Fatigue Testing of Protective Ankle and Foot Devices