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MPM Pendulum Machine |
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MPM Drop Tower |
Introduction
Impact tests are performed to measure the response of a material to dynamic
loading. The most common laboratory test configurations are the
Pendulum Machine and
the Drop Tower. However,
other test geometries and loading configurations can be used (see our
Beverage Can Tester
and
Double
Pendulum Dynamic Tear web
pages).
Types of Test Machines
MPM manufactures several impact test systems which can perform a wide variety
of impact tests including:
- Charpy pendulum and drop tower impact testing (ASTM E23)
- Drop tower nil-ductility transition temperature (NDTT) impact
testing (ASTM E208)
- Drop weight tear (DWT) impact testing (ASTM E 436)
- Dynamic tear (DT) impact testing (ASTM E604)
- Plastic Charpy impact testing (ASTM D256)
- Miniature Charpy pendulum impact testing (ASTM E2248)
- Beverage can impact testing
Options
The impact test equipment can be provided with several options:
- Optical encoder for velocity and energy
measurement (pendulum machines only)
- Instrumented striker system
- Automatic pendulum return system (pendulum
machines)
- Automatic rail cart positioning system (drop
tower machines)
- In-situ heating & cooling system
- Automatic specimen transfer system
- Image analysis system for percent shear
determination
Energy And Impact Velocity
Energy and impact velocity are two key measurements made
during an impact test. These measurements can be made using various
technologies depending on the type of test machine. Drop tower test machines
measure energy using an instrumented striker system (see the
Instrumented Impact Testing page). The impact velocity is obtained
using an infrared detector mounted to the test machine
frame.
MPM pendulum impact test machines measure the energy
absorbed in fracturing a test specimen using an optical encoder with 36,000
divisions per revolution. This is the finest division encoder ever used in
Charpy testing and is capable of resolving energy to a much finer resolution
than can be achieved with a dial. For example, the MPM encoder resolves
energy to within 0.03 ft-lbs on 400 ft-lb pendulum machines. Experience at MPM has shown that it is not possible to resolve a
dial indicator to within better than about 0.25 ft-lbs. Therefore, the 100
year-old dial has been eliminated from the MPM test machines. The encoder
data is acquired by the ImpactTM v 4.3 software and used to
determine the absorbed energy by calculating the height of the striker contact
point before release and the maximum height attained after impact. In
addition, the velocity of the striker is recorded from release up to
termination of the impact event. Therefore, the exact velocity at impact is
recorded in the test record for each test. The software provides a printed
test record which includes key information such as the test specimen ID, the
date of the test, name of the operator, test temperature, impact velocity,
measured energy, etc. A sample output is shown in the Figure below.
| Click below to enlarge and enhance photo |
 |
Input Test Results Showing
Instrumented
Striker and Optical Encoder Data |
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