Food mechanics: A new device for testing fruits and vegetables

The new mechanical device developed is capable of performing compression tests but also bending, torsion and tensile tests. Its measurement system has the following components: a load cell (0 to 9800 N), a strain gauge signal conditioning board, a plug-in general purpose data acquisition board, and a displacement sensor (0 to 29.7 mm). These components Lire connected to a personal computer that has specially developed software. The load cell consists of four extensometers, which (ire sensible to compressive load. The signal conditioning board filters and amplifies the signal, which is acquired by the AD converter, making this information available to be processed by the software. The device is powered by a DC motor (12 to 24 Volts). By setting the motor voltage, it is possible to control its rotation. The displacement sensor was made with a sliding potentiometer, which is pushed by the mobile component of the device while the tests are performed. Finally, the software provides the stress-strain diagram for each test. In order to guarantee reliable results, tests are made with cylindrical samples with same dimensions (radius and length). For the first set of tests, potatoes were studied. The test results for compressive showed an average value of 897.64 kPa. This value seems to be compatible to the ones from the literature. The device proves to be reliable. Moreover, its flexibility allowed testing a variety of fruits and vegetables under compression, tension, torsion and combined loads.