The cutting, gripping, feeding, fine cutting, and
throwing operation in Napier grass harvesting is the process
that should be taken into account in the design of
harvesting machines. In addition, the cutting and fine
cutting operation is closely related to the shear properties of
forage grass stem. According to previous studies, this study
evaluated the shearing strength and energy of crop stem
using a texture analyzer to determine the forcedisplacement
curve obtained from the shearing process.
The measurement of shear velocity using a texture analyzer
in a stem shearing test may not reflect the actual shear
velocity of a forage grass harvester. The test results may be
distorted and produce errors. Therefore, this study used a
single pendulum impulse-cutting device to simulate the
shearing conditions of cutting Napier grass stem in
different harvest periods. The strength-time curve of forage
grass stem was obtained from the impact shearing test, and
the shear force and shear impulse per unit area were
calculated. The moisture content of Napier grass stem was
measured. The harvest period, bevel angle, and shear
velocity were changed. The process of shear failure was
analyzed according to the force-time diagram, and its effect
on the shear strength and shear impulse of Napier grass
stem was discussed as a reference frame for designing a
Napier grass harvester.