Experimental determination of the critical depth of cutting of blocked soil cutting by cutters and the length of the ploughshare of chain excavators

The development of civil and industrial construction and the growing trend of construction of underground communications have led to an increase in the volume of work on the laying of gas and oil pipelines, water mains, sewerage systems, power cables and communication cables. Much of the excavation work in the construction of these communications is performed by trench excavators.

Determination of kinematic and geometric parameters of multi-scraper chain trange excavators on the basis of the semi-blocked critical depth regime of soil cutting

Trench excavators with a chain-scraper working body became widespread in the construction of linearly extended objects. Increasing workloads and rising energy prices call for optimizing the parameters of construction machinery. The most important component of the process of digging the soil with a chain-scraper working body is cutting the soil with scrapers (knives).When calculating the cutting forces, the working body is taken as a complex mechanical system of traction chains and transverse beams, on which in a certain order are arranged and fixed scrapers-knives with known angular parameters. Separation of chips from the soil is carried out by each scraper in the conditions of blocked, semi-blocked and free cutting of the soil. It should also be borne in mind the change in resistivity and energy consumption of soil cutting with a change in chip thickness. The minimum energy consumption of soil destruction takes place at a critical depth of cut. To reduce the energy consumption of the soil destruction process, a method of calculating the parameters of chain-scraper working bodies of trench excavators is proposed, which is based on critical depth cutting of soils. The initial data for the calculation are: technical productivity, m3 / h; maximum trench depth, m; trench width, m; physical and mechanical characteristics of soils (coefficient of adhesion, specific gravity, angles of internal and external friction). The proposed calculation method allows to determine the technological and geometric parameters of the chain-scraper working body with critical depth cutting of soils.

Mathematical model for determining characteristic points on the radial knife of the geokhod executive body

The article presents a mathematical model for determining the values of the characteristic points of the knife executive body (EB) of the geokhod. For this, the boundary conditions for determining the characteristic points on the radial knife of the geokhod executive body are indicated. The result of the work are the obtained expressions for determining: P a.c is the the projection of the component of the soil cutting force, depending on the cutting width, onto the main axis of rotation of the geokhod, R e.a.c is the projection of the component of the cutting force of the soil on the plane, which is located perpendicular to the main axis of rotation of the geokhod. Based on the work carried out, tasks for further research were identified.

Biomimetic Rotary Tillage Blade Design for Reduced Torque and Energy Requirement

A rotary cultivator is a primary cultivating machine in many countries. However, it is always challenged by high operating torque and power requirement. To address this issue, biomimetic rotary tillage blades were designed in this study for reduced torque and energy requirement based on the geometric characteristics (GC) of five fore claws of mole rats, including the contour curves of the five claw tips (GC-1) and the structural characteristics of the multiclaw combination (GC-2). Herein, the optimal blade was selected by considering three factors: (1) the ratio ( r ) of claw width to lateral spacing, (2) the inclined angle ( θ ) of the multiclaw combination, and (3) the rotary speed ( n ) through the soil bin tests. The results showed that the order of influence of factors on torque was n , r , and θ ; the optimal combination of factors with the minimal torque was r = 1.25 , θ = 60 ° , and n = 240 rpm . Furthermore, the torque of the optimal blade (BB-1) was studied by comparing with a conventional (CB) and a reported optimal biomimetic blade (BB-2) in the soil bin at the rotary speed from 160 to 320 rpm. Results showed that BB-1 and BB-2 averagely reduced the torque by 13.99% and 3.74% compared with CB, respectively. The field experiment results also showed the excellent soil-cutting performance of BB-1 whose average torques were largely reduced by 17.00%, 16.88%, and 21.80% compared with CB at different rotary speeds, forward velocities, and tillage depths, respectively. It was found that the geometric structure of the five claws of mole rats could not only enhance the penetrating and sliding cutting performance of the cutting edge of BB-1 but also diminish the soil failure wedge for minimizing soil shear resistance of BB-1. Therefore, the GC of five fore claws of mole rats could inspire the development of efficient tillage or digging tools for reducing soil resistance and energy consumption.

Comparison of soil and corn residue cutting performance of different discs used for vertical tillage

High amount of corn (Zea mays L.) residue left in the field interferes with seeding operations, which hinders the viability of conservation agriculture. Vertical tillage is a promising practice in dealing with heavy crop residue, but its effectiveness largely depends on the design and use of tillage machines. In this study, three vertical tillage discs with different shapes, namely notched, plain, and rippled, were tested in a soil bin at two different working depths, shallow (63.5 mm) and deep (127 mm). Corn residues were spread on top of the soil as surface residue. soil cutting forces, soil displacement, and residue mixing with soil, as well as residue cutting were measured. The results showed that the working depth had a stronger effect on the performance of discs as compared to the disc type. No difference in residue cutting was found between the treatments. The deep working depth resulted in 5.1% higher residue mixing, 53.4% greater soil cutting forces, and 34.9% larger soil displacements, as compared to the shallow depth. The rippled disc resulted in the largest soil displacements with the greatest demand in soil cutting forces. Overall, the rippled disc was the most aggressive among the three discs with regard to the performance indicators measured. The results suggested that varying working depth would be an effective approach in changing the soil dynamics and residue cutting performance of the discs for vertical tillage.

The influence of hardening on the operational properties of soil-cutting tools

Today, soil cutting tools are mainly made from carbon steels, which are heat treated to provide high hardness and strength. However, at present, the durability of such a hardened soil-cutting tool of both domestic and foreign manufacturers is far from perfect. One of the reasons for the insufficient resistance to abrasive wear of a soil-cutting tool subjected to hardening by heat treatment may be its heating by frictional force in contact with the soil. As a result of such heating, the steel undergoes additional tempering, which leads to a decrease in the surface hardness of the cutting edge of the tool by almost 2 times - 49-50 HRC to 22-34 HRC, de-pending on the intensity of metal heating. This circumstance was established during metallographic studies of samples cut from the shares of the KB-01 body of the PBS-4 plow. One of the ways to solve this problem is to obtain a wear-resistant layer on the surface of the soil-cutting tool, which is not subject to the negative effects of reheating during operation, for example, from alloyed white cast iron by the method of plasma-powder surfacing. Metallographic studies showed that the deposited layer has a hardness of more than 62 HRC. At the same time, such types of heat treatment as hardening, normalization or annealing do not have a noticeable effect on the hardness of the deposited layer. Metallographic studies of the deposited metal after operation also showed the absence of notice-able changes in its microstructure and hardness. This indicates that reheating from the action of fric-tion forces does not have a significant effect on the properties of a soil-cutting tool strengthened by plasma-powder surfacing, which contributes to an increase in its duration of operation.

Parameters of tillage working bodies

This article notes that most of the soil-cutting working bodies wear out their socks a lot, as a result of which their limiting state is reached. Despite the fact that other parts of the working body are still workable and the stock of metal for wear is still sufficient, the working body is completely rejected. In this regard, it is emphasized that increasing the durability of the nose parts leads to an increase in the durability of the entire working body. To determine its parameters, the condition for leveling the resources of socks and other parts of the soil-cutting working bodies is considered. When determining the length of the nose of the bits, an analytical dependence is recommended, taking into account the geometric parameters of the bit and the plowshares welded to it. To obtain self-sharpening in the process of bit nose wear, it is recommended to use a new two-faceted profile. The rational values of the length, the angle of the wedge and the sharpening of the nose are determined, equal to 90 mm, 100 and 350-400, respectively. Based on the condition of rational combinations of strength and self-sharpening characteristics of the toes of bits, the thickness and width of the latter were determined, equal to 22.3 mm and 30 mm, respectively.