The Development of Time Dependent Constitutive Laws of Jujube Flesh

摘要

The mechanical properties of jujube flesh were investigated by using ramp-hold tests to obtain the stress-time and strain-time relation of jujube fresh under compress load. Furthermore, CCD camera was used to measure the deformation of specimen during the tests. Linear viscoelastic constitutive models were used to describe the time dependent mechanical behavior of jujube flesh. The instantaneous and long-term elastic moduli of jujube fresh were obtained from the stress and strain relations at the beginning and end of ramp-hold tests. The relaxation coefficients of linear viscoelastic model were computed by using least square fitting procedure with fixed characteristic times. The results show that a linear viscoelastic model with three relaxation time constants can well describe the time dependent force behaviour of jujube fresh under unconfined compression. However, linear viscoelastic model cannot describe the lateral deformation of specimen under compression.