EXPERIMENTAL STUDY OF THE BENDING STRENGTH OF A LIGHTWEIGHT SPINDLE OF A VERTICAL-SPINDLE COTTON PICKING MACHINE

УДК 620.172

Abstract

This article discusses the bending strength of the lightweight vertical spindle design of a vertical-spindle cotton picking machine. Today, the use of resource-saving ecological technologies in agricultural machinery is considered one of the urgent issues of the time. The proposed new spindle is significant in that it differs from the currently used conventional spindles by its lightweight and strong construction. This leads to the fact that it catches cotton fibers in the opened boll without damaging them and does not cause serious damage to the driving mechanism during its variable reversible motion. The resistance of the spindle construction to the external forces acting on it can be determined theoretically, through experimental tests, and through virtual tests, that is, using CAE programs such as SolidWorks Simulation, ANSYS, KOMPAS-3D, and others. Below are presented the results of experimental tests carried out by mounting a spindle consisting of the assembly of four sectors on the two supports of the GUNT WP 300 device, designed for testing beams mounted on two supports for bending, and by hanging loads of different weights at 1/3 of its length.

Аннотация

В данной статье рассматривается прочность на изгиб конструкции облегчённого вертикального шпинделя вертикально-шпиндельной хлопкоуборочной машины. В настоящее время использование ресурсосберегающих экологических технологий в сельскохозяйственной технике считается одной из актуальных задач времени. Предлагаемый новый шпиндель имеет важное значение тем, что отличается от применяемых в настоящее время традиционных шпинделей своей лёгкой и прочной конструкцией. Это приводит к тому, что он захватывает хлопковые волокна в раскрытой коробочке без их повреждения и не наносит серьёзного вреда приводному механизму во время переменного реверсивного движения. Степень устойчивости конструкции шпинделя к воздействующим на неё внешним силам можно определить теоретическим путём, путём экспериментальных испытаний, а также путём виртуальных испытаний, то есть с помощью программ CAE, таких как SolidWorks Simulation, ANSYS, КОМПАС-3D и др. Ниже изложены результаты экспериментальных испытаний, проведённых путём установки шпинделя, состоящего из совокупности четырёх секторов, на две опоры установки GUNT WP 300, предназначенной для испытания на изгиб балок, установленных на двух опорах, и подвешивания грузов различной массы на участке, расположенном на 1/3 его длины.

Keywords: Vertical spindle, radial force, bending deformation, bending strength, cotton picking machine, lightweight construction, laboratory test, GUNT WP 300, indicator measurements, two-support beam, deformation diagram.

Ключевые слова: вертикальный шпиндель, радиальная сила, деформация изгиба, прочность на изгиб, хлопкоуборочная машина, облегчённая конструкция, лабораторное испытание, GUNT WP 300, измерения индикаторов, балка на двух опорах, диаграмма деформации.

Introduction

Although cotton cultivation is a process that requires a long period and a large amount of water resources, due to the high demand for natural fiber, it still constitutes a large part of agricultural crops in many countries today. Various types of harvesting machines are used to collect the grown crop, including cotton picking machines such as John Deere and Case, which are considered the most popular and efficient machines. Also, the role of the MX-1.8 cotton picking machine, which has been widely used in the Asian region, is incomparable. Although the harvesting rate of this type of machine is somewhat low, they are still used today due to their low cost and suitability for the climate and fields of the region. One of the main requirements for these machines is that their agrotechnical indicators and productivity should be high [1]. Since the vertical spindle is the main working part, research has mainly been carried out on the teeth of the spindle and its construction [3]. In this type of machine, during the cotton picking process, the cotton plant is compressed between the spindle drums within the working gap set according to yield and picking layer. As a result, the spindles are subjected to a radially non-uniformly distributed load along their length in proportion to the body of the cotton plant [2].

Figure 1. Scheme of the harvesting process with a vertical-spindle cotton picking apparatus.-forward speed of the machine. -angular velocity of the spindle drum. -angular velocity of the spindle. -width of the working gap.

At this time, the spindle rod participates simultaneously in complex deformation as a result of the resistance forces generated during the separation of fibers from the boll by the gripping teeth, the impact forces of the cotton plant stem, and the resistance forces formed by its branches. As a result of these forces, the spindle rod must not undergo plastic deformation and must retain its circular cross-sectional shape. Since the cotton plant stem does not have uniform stiffness along its length and has uneven branches, it is considered to act on the working length of the spindle with a non-uniformly distributed load. The maximum value of these forces corresponds to 1/3 of the spindle working part from its base.

Figure 2. Loading scheme generated in the spindle due to the compression of the cotton plant stem

Research methodology.

During the technological process, in order to experimentally determine the bending of the spindle under the action of the radial force generated by the compression of the cotton plant stems, we place it in a bending test device.

Figure 3. Scheme of the laboratory equipment assembled for testing the bending of the spindle under the action of a force directed perpendicular to the generator of the spindle sector fixed on two supports

Considering that the main force reaches its maximum at the branching point of the cotton plant stem, we assume that the maximum load corresponds to the 1/3 part of the working section of the spindle.

Figure 4. Laboratory equipment assembled for testing the bending of the spindle under the action of a force applied perpendicular to the generator of the spindle sector

The test experiment is carried out by gradually increasing the load, and the readings of indicators with a measurement accuracy of 0.01 mm are entered into the table.

Table of indicator readings when a load is suspended on the specified section of the spindle.

Table 1. Table of indicator readings when a load is suspended on the specified section of the spindle

To determine the variation of bending along the spindle length, the indicators are installed at the 1/3, 1/6, and 2/3 parts of the spindle.

The loads are initially applied perpendicular to the generator of the spindle sector and are varied from 5 N to 55 N. In this case, the first indicator installed at the 1/3 part of the spindle shows that the spindle bends from 0.05 mm to 0.611 mm.

The values indicated by the second and third indicators, installed at the 1/6 and 2/3 parts of the spindle, respectively, showing the bending of the spindle at these sections, are given in Table 1 above.

The same experiment is carried out by applying the load to the edge of the spindle sector. In this case as well, the indicator readings are given respectively in Table 1.

Results

The bending deformation of the vertical spindle was studied on the basis of experiments conducted using the GUNT WP 300 device. The spindle was mounted on two supports, and loads of different magnitudes, from 5 N to 55 N, were suspended at 1/3 of its length. The deformation was measured at three points, namely at the initial, middle, and end sections of the spindle, using indicators with an accuracy of 0.01 mm.

According to the data presented in Table 1, with an increase in load, the bending increased linearly in all sections of the spindle. For example, when the load increased from 5 N to 55 N:

Indicator 1, middle section of the spindle: from 0.05 mm to 0.611 mm, 12.2 times.

Indicator 2, initial section: from 0.04 mm to 0.43 mm, 10.75 times.

Indicator 3, end section: from 0.02 mm to 0.29 mm, 14.5 times.

Figure 5. Graph of the relationship between the change in spindle bending and the increase in the applied load at the 1/3 section of the spindle under the action of the applied load

Figure 6. Graph of the relationship between the change in spindle bending and the increase in the applied load at the 1/6 section of the spindle under the action of the applied load

Figure 7. Graph of the relationship between the change in spindle bending and the increase in the applied load at the 2/3 section of the spindle under the action of the applied load

Figures 5–7 present the load–bending relationship graphs. In all sections, a linear increase in bending is observed with an increase in load, which corresponds to Hooke’s law, with the material being in the elastic deformation zone. The greatest bending was observed in the middle section of the spindle (Indicator 1), which is explained by the fact that this point is closest to the load application point. The smallest bending was recorded at the far end of the spindle.

Conclusion

Based on the conducted experimental studies and theoretical calculations, the following conclusions were made:

The proposed lightweight spindle construction operates in the elastic deformation zone under radial loads of up to 55 N, that is, no plastic changes are observed.

The difference between the experimental and theoretical bending values is approximately 15–25%, which is explained by real operating conditions and theoretical simplifications.

It was determined that the weakest point of the spindle is the section closest to the load application point, namely the middle section.

The obtained results serve as a basis for optimizing the spindle construction, for example, by increasing the diameter or replacing the material.

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