A dynamic testing machine performs repeated loading mechanical testing. Where a tensile testing machine would apply a quasi-static load to measure the yield stress and ultimate tensile strength until the specimen reaches its break or rupture point, a dynamic testing machine usually stresses a material within its elastic region with cyclic loads until the specimen fails due to fatigue. The typical types of testing include high cycle fatigue, low cycle fatigue, fracture mechanics including pre-cracking, thermo-mechanical fatigue, and simulated tests such as athletic footwear, auto-injectors or stents. Dynamic testing machines utilize various technologies including servo hydraulic actuators, servo electric motors and linear electric motors.
DYNAMIC TESTING MACHINE
Components and Parts
Fatigue tests are performed on dynamic testing machines. A dynamic testing machine consists of a test frame that is equipped with a load cell, testing software, and application-specific grips and accessories, such as extensometers. The type of material being tested will determine the type of accessories needed, and a single machine can be adapted to test any material within its force range by simply changing the fixturing.
|Dynamic Testing Machine
Dynamic testing machine load frames can come as either Servo-hydraulic, Servo-electric or Linear-Electric depending on their force capacity and dynamic performance.
Test software is where operators can setup the machine, create test methods, run the test and export the results.
The load cell is a transducer that measures the force applied to the test specimen. Instron’s patented Dynacell’s also incorporate accelerometers to remove the errors in load introduced by inertia from high speed dynamic testing.
|Grips and Fixtures
A wide range of specimen grips and fixtures are available for specimens of different materials, shapes, and sizes.
Some test methods require measurement of a specimen’s elongation under load. Instron supplies several contacting and non-contacting devices suitable for dynamic strain measurement and control.
Dynamic testing machines are available in a variety of different sizes, force capacities ranging from 1000 N to 5 MN, and dynamic performance from 1 Hz to 100 Hz. Most low force dynamic testing is performed on a linear electric motor machine, while higher force applications require Servohydraulic frames and actuators. Instron's ElectroPuls systems are available in capacity ranges from 1000 N to 20 kN and can perform a wide range of different test types, including tension-tension, tension-compression, compression-compression, bend fatigue, and a wide array of biomedical standards. Instron’s Servohydraulic systems are designed for higher capacity testing from 25 kN to 5 MN for testing stronger materials and larger components such as high strength steels and advanced composites.
DYNAMIC TESTING STANDARDS
Standards for Testing Plastics, Elastomers, and Metals
Most dynamic testing is performed on established standards published by standards organisations such as ASTM and ISO. Testing standards prescribe acceptable test parameters and results for different types of raw materials such as metals, plastics, elastomers, textiles, and composites, as well as for finished products such as medical devices, automotive parts and consumer electronics. These standards ensure that materials and products entering the supply chain display predictable mechanical properties and are not likely to fail in their expected end use. Since the cost and safety implications of product failure cannot be overstated, companies and encouraged to invest in high-quality, accurate testing equipment that is designed to help them easily determine whether or not their products meet applicable standards.
Less Setup, More Testing
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