Experimental Study Of Mechanical Properties And Their Influencing Factors For Oolong Tea Shape-making Leaves

Shape-making is an important technology of tea processing, the quality of shape-making has strongly related to the mechanical properties of the tea leaf being processed and the acting force of shape-making machine,the mechanics indexes of tea include some parameters such as modulus of elasticity,stress,stain,elasticity,plasticity,flexibility and volume-weight, etc. basicly reflect the difficulty level and the shape-making quality of tea. The mechanics characteristic of Oolong Tea is still a blank field at present, taking the research on the mechanics characteristic of Oolong Tea, is of great importance to controlling rolling acting force reasonably,mastering the opportunity of rolling,reducing the wastage of break in tea processing,improving tea quality,mproving productivity and economic benefit.The article using HD-609computerized simple columnar tension testing machine to determine the stretch mechanics characteristic parameters of some Oolong tea varieties tea leaf of different season, the mechanical characteristics change rule of Oolong tea shape-making leaf being processed was discussed deeply under different water content、 different leaves position and different leaves temp conditions. The article proving the influence mechanism of Oolong tea mechanics characteristic to rolling quality, providing scientific theory basis for further research of Oolong tea rolling technology and developing new equipment of rolling, through the mechanics characteristic research of the rolling leaf using two different rolling technology, the elasticity,plasticity,flexibility and volume-weight difference under different Oolong tea rolling technology was also proved. Experimental study are as follows:(1) The crude fiber content of Tie-Guan-Yin、MaoXie、HuangDang、Fudingdabaicha and RouGui of diffenent season,different leaf position is in the scope of10.3±0.21%～25.44±0.51%.Crude fiber content of tea is strongly related to the mechanical properties of tea. The maximum stess,breaking stess and the modulus of elasticity increases with the increasing of crude fiber content;the maximum strain and breaking strain decreases with the increasing of crude fiber content.(2) The experiment about the crude fiber content and mechanics characteristic of Oolong tea leaf shows the elastic modulus of Tie-Guan-Yin、MaoXie、HuangDang、Fudingdabaicha and RouGui is within the scope of4158.88～14849.11Kpa, the maximum stess is within the scope of870.00～1842.97Kpa, the fracture stress is within the scope of673.33～1639.62Kpa, the influence of leaf position to modulus of elasticity,maximum stess and breaking stress is highly significant. First leaf>second leaf>third leaf. The maximum strain of tea leaf is within the scope of10.61%18.36%, the fault strain is within12.19%～26.95%, the leaf position has a highly significant effects on the maximum stain and bteaking stain, third leaf>second leaf>first leaf, there are some differences between different varieties.(3)The research on the mechanics characteristic of the Oolong tea leaf under different water content condition shows the leaves modulus of elasticity and stress increases with the water content decreasing, while strain appears " low-high-low" trend, the elastic modulus in different water content is within the scope of5068.62-22841.84Kpa;the maximum stess is within the scope of1003.47-2715.60Kpa, the fracture stress is within the scope of824.66-1724.60Kpa; The maximum strain of tea leaf is within the scope of14.18%-28.06%, the fault strain is within13.78%-29.46%. In the early stage of shape-making the water content level is higher,the resiliency and plasticity level is lower, its easily to produce flat tea strips and tea block mass, the shape-making dynamics must be control well; the water content level decreases in the middle stage of shape-making, the resiliency and plasticity level of tea become higher, enhance the shape-making dynamics appropriately still not easy to produce fait tea strips; in the later stage of shape-making the water content level is lower, the resiliency of tea is increases while the plasticity level of tea is decreases, in this stage the pressing and rolling dynamics should be decrease, the shape-setting dynamics should be the main dynamics in this stage, these is good reduce the percentage of broken tea.(4) The results of the experiment on mechanical characteristic of different leaves position of Oolong tea shows the modulus of elasticity and stess of being processed tea leaves increases while leaf position sequence raising; the strain appears an opposite trend, the elastic modulus is within the scope of3407.79-22713.97Kpa;the maximum stess is within the scope of871.72～2560.61Kpa, the fracture stress is within the scope of757.49～1602.02Kpa; The maximum strain of tea leaf is within the scope of10.97%～40.78%, the fault strain is within15.83%～45.3%.the shape of tender leaf could easily change under smaller force, but the old leaf shows an contray trend.(5) The results of the experiment on mechanical characteristic of different leaves temprature of oolong tea shows in the process of tea rolling(include early rolling leaf、first drying leaf、again drying leaf), the mechanical characteristic change while the temperature change, the modulus of elasticity and stress decreases while the temperature increasing; the strain shows an opposite trend.the elastic modulus is within the scope of3880.87～13990.77Kpa;the maximum stess is within the scope of818.60～1877.79Kpa, the fracture stress is within the scope of618.30-967.34Kpa; The maximum strain of tea leaf is20.74%～29.57%within the scope of, the fault strain is within22.85%-32.85%the flexibility、 elasticity and plasticity of rolling leaf enhance greatly though increasing the temperature of being processed leaves, tha shape would make greatly change under a smaller force. This is good to improve productivity greatly.(6) The results of the experiment on mechanical characteristic of different shape-make proccessing of oolong tea shows that the water content level and volume-weight change continually during rolling and pressing process. The volume-weight increases gradually while the water content level decreasing; the flexibility and plasticity of being proecssed leaf decreases gradually with the development of shape-making, the elasticity raises firstly then tend to recede with the rolling times increasing. The first3-5rolling make being processed tea leaf from first flat sheets to rolling ball shape, the volume-weight and elasticity increases gradually; with being processed tea leaf become particle shape after first drying, the shape setting gradually, with the water content decreases, the shape of tea being Set better, the elasticity decreases gradually, the volume-weight increases gradually.