As part of an effort to measure impact damage-related physical properties, a precision 3-m (9.8-ft)instrumented pendulum was developed to record force and contact area profiles for normal impactsof whole fruit or vegetable specimens onto an essentially rigid, fiat anviL The specimen is attached tofour adjustable suspending lines (music wire and Kevlar{sup}*) to form a pendulum. The anvilagainst which it strikes is fitted with a force transducer and with a contact area sensor of the authors'design. Two precisely spaced infrared beams (beams interrupted by sample) allowed approach andrebound velocities to be measured. An accelerometer attached to the trailing end of the commoditymeasures deceleration during impact and free vibrations during rebound. Impact profile data aretypically sampled at 10 kHz per channel, sufficient to capture the required data while conserving datastorage space. Operating procedures include single impacts, constant-height multiple-impacts(CHMI) (for determining bruise resistance), increasing-height multiple-impacts (IHMI), and pairedincreasing-height multiple-impacts (PIHMI) (for determining bruise threshold in apples). Thesemethods are ideally suited for studying impact failure in commodities exhibiting compression failure.Those failing primarily in shear, such as potato tubers, can also be studied. The design, calibration,and operating procedures are described.
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