Abstract
Creep and relaxation characteristics of stem for rice seedlings grown in plastic cell tray were studied by static tensile testing, in order to determine the relationship between characteristic parameters (rheological model parameters, stress components and strain components) and test levels (stress levels and strain levels). Rice seedling stem specimen used in the test was 40 mm in length. And the applied test values for the creep and relaxation test ranged from 1.0-3.0 MPa and 1.5%-3.5%, respectively, each for 5 levels. The results indicated that elastic modulus in the creep and relaxation model was not affected by test levels. However, except that viscosity coefficient ηkv was a constant and ηm1 decreased with the increase of test levels, other viscosity coefficient and rheological time nonlinearly increased as the test levels increased. And strain components in the creep model and stress components in the relaxation model significantly increased as the test levels increased. Keywords: model parameters, rheological property, stress relaxation, creep property, rice seedling stem, plastic cell tray DOI: 10.25165/j.ijabe.20201304.5673 Citation: Xiao J Q, Ma R J, Chen Y. Effects of test levels on creep and relaxation characteristics parameters of stem for rice seedling grown in plastic cell tray. Int J Agric & Biol Eng, 2020; 13(4): 19–28.
Highlights
Rice (Oryza sativa L.) is widely cultivated in China[1]
The following conclusions can be drawn: 1) Creep and relaxation tests of stem for rice seedlings grown in plastic cell tray at different test levels can be described by the Burgers 4-element model and the Maxwell 5-element model, respectively
3) Whether creep test or relaxation test on rice seedling stems, there were no significant relationships between the elastic modulus and the test levels
Summary
Rice (Oryza sativa L.) is widely cultivated in China[1]. It is the principal food crop in China. Rice potted-seedling throwing transplanting is one of the three principal agronomic patterns to plant rice in China[4]. When the proposed two-degree-of-freedom manipulator type transplanter working in the field[5], rice seedlings were pulled up from the cell tray with clamp-shaped grippers. Rice seedling stem is a kind of biological material and agricultural fiber material with vascular bundle structure[6], composed of cellulose, lignin, hemicellulose and other macromolecules[7,8]. It is necessary in order to understand the rheological properties of stem for rice seedlings using static tensile testing
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