Measurement And Statistical Analysis Of Mechanical Behaviors Of Paddy Stem With Optical Method

China is one of the major agricultural countries around the world. The lodging of paddyis a serious issue which considerably limits the rice yield. Paddy lodging is directly relatedwith the mechanical properties of paddy stem. Accurately description of the mechanicalproperties of paddy stem is important for the analysis of their resistance to lodging. The paddystem, which is composed of heterogeneous biomaterial, is a kind of soft structure withirregular cross section. It’s difficult to obtain an accurate measure of the mechanical propertieswith traditional method. How to reliably and accurately measure paddy related mechanicalproperties and give statistical rule, is the base of reasonably estimated the paddy yield andscientific breeding.The thesis explores the image analysis methods to realize non-contact and accuratelymeasurements of cross section dimension of paddy stem, tensile deformation，and the elasticmodulus and bending stiffness, The main research methods and achievements are as follows.(1)The Digital Image Correlation method（DIC）is for the first time employed for thenon-contact and accurate measuring of longitudinal deformation of paddy stem, and contrastthe tensile strains were measured with strain gauges. The experimental results show that theelastic moduli measured with strain gauge scattered in a wide range, whereas the distributionof elastic modulus and flexural stiffness obtained by the digital image analysis methoddemonstrates quite small deviation, accurately reflecting the mechanical properties of paddystem.(2) For the first time, living single paddy is used as the sample in order to measure itsbending deformation under equivalent loading-unloading, According to which the elasticmodulus of paddy stem is estimated and compared with the elastic modulus of paddy stemmeasured by DIC method in laboratory. The feasibility of evaluating the mechanicalproperties of paddy sample in field using the testing results in laboratory has been studied.(3) The mechanical properties of paddy stem have been analyzed combining experimentsand finite element modeling. The transverse elastic modulus and transverse ultimate strengthof paddy stem is estimated, laying the base for the finite element analysis of lodgingresistance of paddy under natural condition.