Study of the process of stems flattening during flax harvesting

BACKGROUND: When preparing flax straw using the dew retting method, uniformity of the raw material’s technological parameters along the length of the stems is not ensured, which reduces the yield and quality of the fiber. The excessive spread of values is due to differences in the mechanical properties of the stems along the length of freshly pulled plants. The middle and upper parts of the plant, when in contact with the working parts of flax harvesting machines, receive microdamage to their structure and dry out faster, activating tissue maceration in these areas of the stem. The lower part of the plants, having no such contacts, retains the integrity of their structure and remains viable, delaying the maturation process in this zone and increasing the non-uniformity of the parameters along the stem length. Maximum non-uniformity is observed during two-phase flax harvesting due to a long gap between the effects of the working parts on individual sections of the stems. The most effective solution to the problem is flattening the lower part of the plants when flax pulling. Many known scientific studies confirm the high efficiency of this technique. At the same time, flattening weakens the bending stiffness of the stems, which can complicate layer formation before flax straw processing and reduce the yield of long fiber. AIM: Study of the effect of flattening working bodies of flax harvesters on the bending stiffness of plants. METHODS: To study the influence of operation modes of flattening working bodies of flax harvesters on bending stiffness in consequent cross-sections of stems along the whole technological length of plants harvested using the two-phase technology with flattening of root ends at flax pulling, the TLP-1.5K (P) flax pulling machine with a two-roll flattening unit and the POL-1.5K gathering-and-combing machine with a comb stripping unit were used. A special device capable of estimating the bending stiffness of the stem by measuring the fracture force and the corresponding deflection has been developed. Conventional and partial methods of experiment conducting were used. RESULTS: It has been found that stems flattening during two-phase harvesting does not have a significant effect on the distribution of bending stiffness along the technical length of the plant. In all cases, the weakest part of the flattened stem is its middle part, flattened by the belts of the pulling sections. Therefore, the maximum probability of stems bending during layer formation is observed in the middle part, and the processes of thinning of the layer of flattened and non-flattened stems will not have significant differences. Processing of experimental lots of flax straw obtained during two-phase flax harvesting with flattening of the root ends of plants showed an increase in the yield of long fiber by an average of 2.37%. Thus, the categorical hypothesis about the harmful effect of plant flattening on the process of layer thinning and the yield of long fiber was not confirmed. CONCLUSION: To ensure high efficiency of the two-phase technology of flax harvesting, all machines intended for plants pulling should be equipped with flattening units. In addition, it has been found that it is necessary to process the tops of the stems with crushing rollers as well.