Crawler Track Research Articles

Mechanical and Fatigue behavior of G22NiMoCr5-6 and G18NiMoCr3-6 used in heavy-duty crawler track plates

G22NiMoCr5-6 and G18NiMoCr3-6 steels are commonly used in the manufacturing of crawler track plates of heavy-duty equipment due to their enhanced mechanical properties which allow them to be suitable for this particular application. This research aims to investigate the mechanical and fatigue behavior of both material grades to evaluate their performance in the manufacturing of heavy-duty crawler track plates. In the present work, experimental investigations were carried out including chemical composition, tensile, hardness, Charpy impact, and low-cycle fatigue tests. Also, metallographic examination was conducted to show the microstructure of both materials. Based on the experimental analysis results, the bainitic structure of G18NiMoCr3-6 was found to have longer fatigue life and higher toughness than the tempered-martensitic structure of G22NiMoCr5-6 which qualifies G18NiMoCr3-6 to be more suitable for manufacturing of heavy-duty crawler track plates than G22NiMoCr5-6 steel.

Failure investigation of fractured crane crawler track plate

A repetitive failure of crawler track plate made of G22NiMoCr5-6 of heavy-duty crane is observed to be occurring with an average rate of one track plate fractured every 100 working hours, presenting a great problem that may impose hazard on personnel and raising direct and indirect costs required for maintenance, spare parts, and downtime costs. The objective of this research is to investigate the cause of track plate failure. An experimental investigation is carried out including chemical composition, tensile test, impact toughness, hardness test, and metallographic observation along with fractography analysis. Also, working stresses are defined by applying the finite element method. Based on the results of the experimental and computational analysis, the fracture of track plate made of G22NiMoCr5-6 predominantly resulted from deficiency in the track plate geometry design which increases stress concentration within the fracture region, in addition, slight deviation of material properties compared to those prescribed by the standard may have played a role in exacerbating the problem.

Assessment of the compaction effect and operational characteristics of a crawler tractor based on a rheological approach

BACKGROUND: At considering the issues of crawler tractors interaction with soil the determining factor is the time-varying impact of loads on the soil layer, its stressed and strained state, which, in turn, directly depends on its stress-strain properties. The properties assessment should be carried out with a rheological approach, which allows to explain many phenomena and processes and to develop new high technologies in terms of the criterion of minimizing the impact on the soil.
 AIMS: Studying the compacting ability of a crawler tractor in a configuration in various machine-tractor units, obtaining a curve for the effect of the traction load on the tractor hook, tractor speed and tractor mass redistribution over the lower track wheels on changes in soil compaction due to developing deformations, the coefficient of running resistance and skidding of the crawler-mounted mover.
 METHODS: The evoluation method for compaction impact of crawler-mounted mover on the soil layer was developed on the base of the previously constructed a general mathematical model for determining ways of reducing the compacting impact of crawler-mounted movers on the bearing surface, computer calculation programmes and the carried out assessment for the deformation development and changes of soil compaction under the crawler track.
 RESULTS: There are presented the simulation results of the process with an assessment of the developing dependences of the crawler tractor rut depth and its sliding on the travelling speed and on the displacement of the center of pressure at different loads on the hook, that obtained with the developed metod of analysis and the well-known theory of hereditary creep of elastic-visco-plastic materials. At the same time, the development of vertical and shear deformations of the soil layer in the area of lower track wheels impact is separately analyzed.
 The analysis of the constructed dependencies allows to identify a number of patterns for changes of compacting effect indicators of a crawler tractor on the soil with an assessment of the influence of the main design and technological parameters on them. It is established that taking into account the rheological characteristics of the soil layer and its state parameters permit significantly improve the accuracy of calculations for vertical and shear deformations of the soil layer and its final compaction after successive passes of the crawler lower track wheels. At the same time, the desired indicators behavior is ambiguously at passes of various lower track wheels.
 CONCLUSION: The conducted studies contribute to the optimal selection of parts for various machine-tractor units based on a specific crawler tractor, which perform the appropriate technological operations in certain conditions of work at specific parameters of the soil state.

Vibration-dependent cutting marks and redesign of crawler track of a multiblade saw

ABSTRACT High-speed wood sawing results in an uneven surface were evaluated. Machine structure was redesigned to reduce noise and unevenness of such sawing. A crawler track is driven by an auxiliary wheel. The roller seat on top of the board saw stabilises chain pieces. Investigations revealed some influencing mechanical factors, including static deformation, resonance excitation, and rigid body collision. A complete chain feed model was constructed to analyse related acoustic noise. Quantitative analysis enabled a successful redesign of chain feed elements. Chain feed simulation enabled the reduction of conflicting factors and revealed the optimal shape for chain links. The structural deformation of die casting indicated the possibility of variation in the chain shape. The flatness of the chain surface was reduced, and noise generated during the collision of links was minimised. Simplified modelling enabled identification of problems in the multi-blade system.

Investigation of strength and deformability of the deep-water clay base of the ferromanganese nodules collection unit

The article considers methods, instruments and equipment for laboratory and field studies of bottom soils of the Clarion-Clipperton region of the Pacific Ocean. The characteristics of the physical and mechanical properties of the bottom sediments of the upper part of the first (cover) engineering and geological complex are presented. The features of deformation of the bottom soil under load are revealed. A general view is shown and the design parame-ters of a model sample of a deep-sea unit for collecting ferromanganese nodules are presented. A design scheme for transferring the load from the unit to the base has been compiled. The type of equation of state of the bottom soil for the condition of placing the unit on the bottom is chosen. The dimensions of the crawler track of the unit are determined. The prediction of the deformation of the water-saturated clay base of the aggregate was carried out using the methods of the theory of linear deformation of the soil.

Prevention of injury when using mobile means of mechanization in AIC in the case of starting their engines with the engaged gear transmission

It is informed about the importance of the structures of the agro-industrial corps in world civilization and in the country in terms of food supply for the population. Attention is drawn to the need for a variety of food products, which is ensured by the versatility of agricultural enterprises and a variety of types of work. The mechanization of agricultural production is based on a variety of agricultural machinery and equipment used in order to increase productivity, production efficiency and facilitate labor. It is noted that in the fleet of agricultural equipment used, the determining share of mobile machines with internal combustion engines (cars, tractors, combines, bulldozers, excavators, scrapers and other machines) on a wheeled or crawler track is drawn. According to the regulatory and legal framework, all types of work activities should not lead to injury and illness of workers. At the same time, many of them, for one reason or another, are accompanied by severe and fatal injuries. One of the reasons is the ability to start their engines when the gear is engaged in the transmission. In order to eliminate such situations, an innovative solution has been proposed - a device for blocking the possibility of starting the engines of mobile machines if the gear shift lever is not set to the neutral position before starting. This prevents the possibility of injury to operators and persons servicing the unit.

Ground Pressure Changes Caused by MHT 8002HV Crawler Harvester Chassis

Ground contact pressures exerted by elements of the machine chassis on the ground in the forest are associated with the machine impact on the soil during its operation. In the case of a crawler system, determining the ground contact pressure appears simple, which is not entirely true. The aim of the study was to analyze the loads on the ground (forest soil) exerted by the MHT 8002HV crawler harvester chassis. The measurements were made in Forest School Enterprise in Kostelec nad Černými Lesy, Central Bohemia Region in the Czech Republic, on brown soil made of clay on stony formations, fresh mixed mountain forest (FMMF), with the use of a hydraulic scale when extending the harvester crane forward along and perpendicular to the longitudinal axis of the machine. The calculations were carried out with a simulated load of the crane on the tree in question, assuming that the impact on the ground of the crawler system is heterogeneous and that the point impact comes from the crawler support wheels. As it was shown, the average ground contact pressures under the crawler track of the analyzed harvester generally do not exceed 70 kPa. The crane extension with a simulated load, which would have caused the crawler track to act on the ground with an average pressure exceeding 70 kPa, was limited by machine stability. On the other hand, high ground contact pressures may occur under a more loaded section of the crawler track if the active length of the crawler track is shortened. As it was shown in the case of a weak track tension, the course of ground contact pressures exerted on the soil deviates from the assumed usually homogeneous impact over the entire length of the crawler.

The Analysis of Filler Material Effect on Properties of Excavator Crawler Track Shoe after Welding Regeneration

The Analysis of Filler Material Effect on Properties of Excavator Crawler Track Shoe after Welding Regeneration

Fundamental Contact Dynamics Model of a Crawler-Type Vehicle Simulation

In this paper, I established a single crawler model with a dynamic contact force considered. I modeled each crawler track using dynamic contact model. By modeling each crawler track, I hope to be able to analyze trafficability of a crawler type vehicle in various road surfaces. First, I think that I established a single crawler model. I modeled a single crawler using Hunt-Crossley model and Coulomb model that handle a nonlinear contact force model. And also, I built a prototype single crawler for comparing the experimental examination with the simulation examination. In advance, the running over limit of the prototype single crawler was analyzed geometrically, and I bore out that it could run over to 163 mm. Therefore, I conducted the experiment examination with step height of 160 mm and 165 mm and obtained trajectory data that were allowed to run over and were not allowed to run over. From the result of both the experimental examination and the simulation examination, I bore out the validity of our single crawler model. I described about our single crawler model, the simulation examination and the experimental examination in this paper.

Optimal weight and power parameters of crawler tractors to reduce pressure on the soil

Crawler and wheeled vehicles are used in a variety of soil and climatic conditions. In the Krasnoyarsk region crawler tractors have a number of advantages. They have a higher traction efficiency, low fuel consumption, and low pressure on the soil. Reducing the pressure on the soil helps to preserve its structure and fertility. This fact is relevant for the agro-industrial complex of Siberia. At present, the vehicle fleet of general-purpose crawler tractors is being reduced. This is due not only to economic reasons, but also the lack of justification for their operation. The paper shows the optimal weight and power parameters. The use of triangular crawler track increases traction efficiency by 3.0% and significantly expands the traction range of effective use of the tractor. For tractors of 4 and 5 classes, the optimal range of change in operating power is 140…175 kW, it corresponds to the optimal range of change in weight 8.5…9.5 tons. For tractors of 5 and 6 classes, optimal interval of changing the operating power is 155…210 kW, it corresponds to the interval of weight change 10, 5…12, 0 tons. Regulation of operating parameters is produced with a change in the coefficient of engine adaptability from 1.2 to 1.4.

Climbing Performance of the Flexible Spiked Crawler Track

Climbing Performance of the Flexible Spiked Crawler Track

Calculation of Hydraulic System of Movable Rigid Barrier Crawler Track

The load, speed and working requirements of a hydraulic system are analyzed and the load of its walking mechanism is calculated according to the composition of the hydraulic system of a movable rigid barrier crawler track, so the related parameters of the main components of the hydraulic system can be obtained. The type of the hydraulic components and driving components is selected according to the calculation results to satisfy the working requirements of the hydraulic system. Finally the type selection results are validated by verifying motion of the key function components of the hydraulic system, so it lays the foundation for system engineering implementation.

Multibody Dynamic Stress Simulation of Rigid-Flexible Shovel Crawler Shoes

Electric shovels are used in surface mining operations to achieve economic production capacities. The capital investments and operating costs associated with the shovels deployed in the Athabasca oil sands formation are high due to the abrasive conditions. The shovel crawler shoes interact with sharp and abrasive sand particles, and, thus, are subjected to high transient dynamic stresses. These high stresses cause wear and tear leading to crack initiation, propagation and premature fatigue failure. The objective of this paper is to develop a model to characterize the crawler stresses and deformation for the P&H 4100C BOSS during propel and loading using rigid-flexible multi-body dynamic theory. A 3-D virtual prototype model of the rigid-flexible crawler track assembly and its interactions with oil sand formation is simulated to capture the model dynamics within multibody dynamics software MSC ADAMS. The modal and stress shapes and modal loads due to machine weight for each flexible crawler shoes are generated from finite element analysis (FEA). The modal coordinates from the simulation are combined with mode and stress shapes using modal superposition method to calculate real-time stresses and deformation of flexible crawler shoes. The results show a maximum von Mises stress value of 170 MPa occurring in the driving crawler shoe during the propel motion. This study provides a foundation for the subsequent fatigue life analysis of crawler shoes for extending crawler service life.

Rigid multi-body kinematics of shovel crawler-formation interactions

Large capacity shovels are deployed in surface mining operations for achieving economic bulk production targets. These shovels use crawler tracks for effective terrain engagement in these environments. Shovel reliability, maintainability, availability and efficiency depend on the service life of the crawler tracks. In rugged and challenging terrains, crawler wear, tear, cracks and failure are extensive resulting in prolonged downtimes with severe economic implications. In particular, crawler shoe wear, tear, cracks and fatigue failures can be expensive in terms of maintenance costs and production losses. No fundamental research has been undertaken to understand the crawler-formation interactions in challenging and rugged terrains in surface mining operations. This study forms the foundations for providing long-term solutions to crawler failure problems. The kinematic equations governing the crawler-formation interactions have been formulated to characterise the crawler motions during shovel production. These equations capture the motions governing the link pin joint, oil sand terrain joint and driving constraints based on the multi-body rigid theory. Crawler propel is achieved by using prescribed velocities along a translational degree of freedom (DOF) and a translational and rotational DOF. The crawler kinematic solutions show that the 3-D crawler–terrain model results in 132 DOFs and requires dynamic modelling to obtain the unknown degrees of freedom. A 3-D virtual prototype model is built to capture the crawler-formation interaction in MSC ADAMS based on the rigid body crawler kinematics. The virtual prototype simulator is supplied with mass properties of crawler shoe, mass, stiffness and damping characteristics of oil sand and external loads due to machine weight and contact forces to obtain the time variation of position, velocity and acceleration for the crawler–terrain engagement for given driving constraints. The results from the driving constraints yield a non-linear longitudinal motion of the crawler track assembly. The crawler track lateral and vertical displacements during translation-only motion fluctuates with maximum magnitudes of 0.7 and 3.6 cm. Similarly the fluctuating longitudinal, lateral and vertical velocities and accelerations have maximum magnitudes of 0.22, 0.046 and 0.56 m/s and 7.41, 1.73, and 34.9 m/s2, respectively. This research provides a strong foundation for further study on developing flexible crawler track model for predicting crawler shoes dynamic stress distributions, cracks development and propagation and fatigue analysis during shovel operations.

Contact and Joint Forces Modeling and Simulation of Crawler-formation Interactions

Cable shovels are used in surface mining operations to achieve economic bulk production capacities. The service life of the rawlers and their shoes define shovel reliability, maintainability, availability and efficiency. The crawler track-terrain interaction generates high time-fluctuating contact forces that result in stress buildup, crack and fatigue failure of wler shoes. In addition, the link pins that connect two crawler shoes can exert large fluctuating pin loads on shoe lugding to shoe breakage. This paper addresses fundamental research into contact forces acting on crawler shoes, joint forces generated in the link pin and total deformation of the formation during shovel propel. During propel, the crawler track is controlled by two drive constraints that cause the crawler to follow straight or turning motions. A virtual prototype simulator of the crawler-terrain interaction dynamics is developed and simulated within the MSC ADAMS environment. The simulation results show that the average penetration depth for different crawler shoes is within the range of 5.9 and 6.7 cm for both types of driving constraints. During translation, the maximum magnitude of contact forces along vertical, longitudinal and lateral directions have respective values of 5.9 × 105 N, 5.5 × 105 N and 1.7 × 105 N. During turning, the crawler track experiences varying bouncing and rolling motions causing maximum magnitude of vertical and lateral contact forces on the crawler shoes to increase 1.15 and 1.42 times the maximum translation values. The total deformation of oil sand terrain for the two motions fluctuates between -0.24 and 0.26 cm and between -1.03 and 1.33 cm, respectively. This study provides solid foundation for further studies on dynamic stress and fatigue failure analysis of crawler shoes during shovel propel and loading operations.

A detailed single-link track model for multi-body dynamic simulation of crawlers

Currently available models for dynamic simulation of tracked vehicles do not include the necessary detail required of a high-fidelity model of crawlers. The rapid increase in computing speed enables the utilization of more complex models, which may include many bodies and force elements. A three-dimensional multi-body simulation model for simulating the dynamic behavior of a crawler was developed using the LMS-DADS simulation program. The model incorporates detailed description of the track, the suspension system, and the dynamic interaction among its components. Three-dimensional contact force elements are used to describe the interaction of the track links with the vehicle’s rollers, sprocket, and idler. User-defined force elements are used to describe the interaction between each track link and the soil. The normal and tangential forces are calculated using classic soil mechanics equations, such as Bekker and Janosi correlations. The grousers, which are a significant part of any crawler track link, were modeled using McKeys’ approach. The model includes new elements, such as the plasticity and viscosity properties of the soil. Sinkage and slip are calculated separately for each track link. Simulation results were compared with the experimental results. In some ride conditions, the simulation results indicate forward motion of a track link while in contact with the soil. The existing theories consider backward motion of a track link when the vehicle moves forward and the link is in contact with the soil. This phenomenon was verified in the experimental work. It was concluded that the influence of the track dynamics and the soil-link interaction on the vehicle dynamics can be better predicted with the newly developed model.

Effect of cold deformation on the abrasive resistance of coatings with applications in the mining industry

Machinery components of the mining industry are often involved in severe wear processes. This is the case of the support wheels of the crawler track of the excavators in the open cast mine. Surface coating technologies are essential to improve the surface performance of such components. In this work, the effect of cold deformation on the wear resistance of several Fe–Cr–Mn alloys welding coated over a steel substrate is studied. After being coated, the specimens were pressed by means of a block hammer which produced surface distortion and thickness variation. This deformation process generates micro structural changes and material which may improve the abrasive wear resistance. Abrasion wear tests were carried out based on the standard test method for conducting wet sand/rubber wheel abrasion tests (ASTM G105-89).

Design and Control of a Mobile Robot with an Articulated Body

Mobile robots having good terrain adaptability, sufficient payload capability, and high mobility are now urgently in de mand. In this paper, design of a practical mobile robot is attempted, with an inspection task in a nuclear reactor as a concrete objective for development. The configuration of the mobile robot is first discussed. A wheel with crawler track, legs, and a snake-like articulated body are shown to be three fundamental configurations. A hybrid configuration consist ing of an articulated body and a crawler track is most ade quate for the nuclear reactor robot because of its excellent terrain adaptability, sufficient payload capability, and high mobility. Design of the joint structure of the articulated body is discussed. Basic control problems such as signal process ing for tactile sensors and control of statically indeterminant forces are also investigated. A mechanical model KR I, a robot with six articulated body segments, 16 degrees of free dom, length 1391 mm, and weight 27.8 kg, is constructed and several experiments are done to demonstrate the basic mobility of the robot and to show the validity of introducing force control.

Experimental field gantry for leaf vegetable production: Specification, design and evaluation

An experimental gantry for leaf vegetable production has been designed and built at AFRC Engineering and evaluated over two seasons. The objectives of the work are to develop and demonstrate practical gantry based systems of crop production. The machine has a 9 m wide working width between two hydraulically driven crawler track units. The upper surface of a 0·6 m deep space frame beam forms the working platform and the beam has a 0·9 m ground clearance. The gantry may be raised off its tracks by jacking down wheels at both ends, it then qualifies under the Road Traffic Regulations as a trailed agricultural appliance when towed on the road by a tractor. A pallet handling system for six pallets has been provided, and the gantry has the facility to carry and power conveyors for harvesting. Various standard or experimental implements may be mounted on a three-point linkage assembly which can be traversed along the beam. A commercial gantry based on the experimental machine has also been built. The cost of this was comparable with self-propelled wheel based field packhouses of similar load capacity. In its first season the farmer has demonstrated substantial advantages over the latter, largely due to reduced crop damage and improved vehicle flotation.

TECHNIQUES FOR MEASURING CHANGES IN THE PACKING STATE AND CONE RESISTANCE OF SOIL AFTER THE PASSAGE OF WHEELS AND TRACKS

SummaryMethods are described for measuring the changes in the horizontal and vertical distribution of packing state and cone resistance following the passage of wheels and tracks over prepared beds of soil. A gamma‐ray transmission system was employed with automatically controlled scanning in a 2 × 2 cm grid in soil sections of 1.08 m length by 0.3 m depth, using a scintillator/photomultiplier detector assembly with stabilized pulse‐height analysis and magnetic tape recording. Changes in cone resistance were measured in a 2 cm (vertical) by JO cm (horizontal) grid in a section 1.4 m length by 0.5 m depth using an electrically driven penetrometer with load and displacement simultaneously recorded on an XY plotter and magnetic tape. Results were analysed and displayed graphically by computer with packing state expressed by a number of optional properties (dry bulk density, total porosity, air‐filled porosity, void ratio, or specific volume).Pronounced differences in packing state and soil strength were observed as a result of the passage of a two‐wheel‐drive tractor, with and without cage wheels, and a crawler tractor. Adding a cage wheel decreased slightly the compaction below the rubber tyre, but formed a partially compacted zone below the cage wheel. Increases of dry bulk density and soil strength were recorded below the crawler track but the values for these properties did not reach the maximum values found below the rubber tyre.