Design framework for DEM-supported prototyping of grabs including full-scale validation

Dingena Schott, Javad Mohajeri, Jovana Jovanova, Stef Lommen, Wilbert de Kluijver

Journal of Terramechanics, Volume 96, 2021, Pages 29-43, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2021.04.003.(https://www.sciencedirect.com/science/article/pii/S0022489821000379)

Abstract: The design ofmachinery for handling granular materials relies mainly on empirical methods and in-house engineering knowledge. This traditional approach provides incremental improvements that are often limited. Advancements in simulation and optimization can offer a promising alternative approach. Most of the research involved in improving or optimizing equipment design does not include the realistic performance of the new prototype and as such it is uncertain that the predicted performance is also guaranteed in practice. In this study, a design framework for a new generation of machinery handling granular materials, grabs, has been established that includes a full-scale validation step.This has been proven to lead to a breakthrough in equipment design. This design framework uses a co-simulation between Discrete Element Method (DEM) and Multi Body Dynamics (MBD), thus, capturing operational conditions in full-scale. The DEM simulation supported design step integrated as the main step to generate new prototypes. The performance of the prototype is evaluated by conducting full-scale experiments, thus validating the adequacy of the new design as well as the accuracy of the co-simulation. Through this a full design cycle has been fulfilled and a validated model has been achieved that is independent of specific design configurations.

Keywords: Grab; DEM-MBD co-simulation; (true) validation; On-site experiments; Design cycle; Industrial-scale

Theoretical analysis of the forces and torques acting on a tractor during ploughing

Martin Čermák, Stanislav Mitáš

Journal of Terramechanics, Volume 96, 2021, Pages 23-27, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2021.04.007.(https://www.sciencedirect.com/science/article/pii/S0022489821000410)

Abstract: This paper presents a physical model of a four-wheeled tractor during ploughing. In this model, the wheels are approximated by ideal non-oscillating harmonic oscillators. The velocity of the tractor is considered to be constant, i.e., the tractor is in an equilibrium state of forces and torques. The equilibrium state is described by Euler’s laws of motion. Finally, an infinite approximation of the wheel stiffness is performed and an exact solution of the forces is presented.

Keywords: Tractor; Three-point hitch; Ploughing; Euler’s laws of motion

Full-field and point strain measurement via the inner surface of a rolling large lug tyre

Megan S. Pegram, Theunis R. Botha, Pieter Schalk Els

Journal of Terramechanics, Volume 96, 2021, Pages 11-22, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2021.04.002.(https://www.sciencedirect.com/science/article/pii/S0022489821000367)

Abstract: Vehicle safety and performance can be dramatically improved if force or friction measurement of the tyre-terrain interface is known. Since the tyre-terrain interface is responsible for the majority of forces acting on the vehicle, this region has received a lot of attention in vehicle dynamics. Direct measurement of the tyre-terrain interface is difficult since it is hidden by the tyre and terrain. A lot of research has been conducted on the inside of tyre using accelerometers or strain gauges with research more focussed on passenger car tyres and very little work performed on agricultural tyres with larger lugs. This study performs strain measurements using point measurement, from strain gauges, and full field measurement, using a stereo camera measurement system, of the inside of an agricultural tyre on a drum test rig during vertical and lateral loading. Results show similar trends when compared to results on passenger car tyres, however the mounting of the strain gauge relative to the lug is shown to play a large role in the developed strain. Linear relationships between the applied tyre force and strain were obtained in different direction with R2 values above 0.97.

Keywords: Agricultural tyre; Contact patch; Stereovision; Strain; Digital image correlation; Rolling tyre

An instrumentation system to measure the loads acting on the tractor PTO bearing during rotary tillage

Sujit Hensh, V.K. Tewari, Ganesh Upadhyay

Journal of Terramechanics, Volume 96, 2021, Pages 1-10, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2021.04.004.(https://www.sciencedirect.com/science/article/pii/S0022489821000392)

Abstract: Application of rotary tillage has been increased due to less tillage passes required, reduced draft, and greater efficiency through reduction in wheel slippage. Early failure of the bearing of tractor power take-off (PTO) shaft was observed in tractors of power range 30–35 horsepower during rotary tillage. An instrumentation setup involving an extended octagonal ring transducer (EORT) was developed and installed at the bottom of the bearing to measure the axial load and the vertical component of the radial load. The horizontal component of radial load was measured by strain gauges. Based on measured loads, the bearing life was assessed. Independent variables were: operating depth, number of blades, gear setting, engine speed, and tyre size. The average axial and radial loads varied from 786–3869 N, and 134–430 N, respectively. However, bearing experienced very high peak loads during each trial. The peak axial and radial loads was recorded between 1081–7534 N and 566–1794 N, respectively. The estimated bearing life based on peak loads was 171.98–28341.39 h. Based on the findings, it may be concluded that the average loads were not sufficient to cause quick failure of PTO bearing, rather sudden peak loads might be the root cause of early failure.

Keywords: Extended octagonal ring transducer; PTO (power take-off); Axial load; Radial load; Bearing life

Analysis of soil flow and traction mechanics for lunar rovers over different types of soils using particle image velocimetry

Shoko Ono, Shohei Namikawa, Kazuya Yoshida

Journal of Terramechanics, Volume 95, 2021, Pages 89-100, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2021.01.001.(https://www.sciencedirect.com/science/article/pii/S002248982100001X)

Abstract: Grouser wheels have been used in planetary rovers to improve mobility performance on sandy terrains. The biggest difference between a wheel with and without grousers is the soil behavior beneath the wheel as the grousers shovel the soil. By analyzing the soil flow, we gain insight into the mechanics dominating the interaction between the wheel and the soil, directly impacting performance. As the soil flow varies depending on the soil properties, the effects of soil type on soil behavior and wheel-traveling performance should be studied. This paper reveals the difference in soil flow and wheel performance on cohesive and non-cohesive soils. We conducted a series of single wheel tests over different types of soils under several wheel-traveling conditions. Soil flow was visualized by using particle image velocimetry (PIV). The experimental results indicate that soil flow characteristics highly depend on the shear strength of the soil. The cohesive soil exhibited lower fluidity due to its higher shear strength. At the same time, the wheel displayed a higher traveling performance over the cohesive soil, that is, a lower slip ratio.

Keywords: Grouser wheel; Soil flow analysis; Particle image velocimetry; Traction mechanics; Cohesive soil

Numerical simulation and testing verification of the interaction between track and sandy ground based on discrete element method

Linxuan Zhou, Jingwei Gao, Cheng Hu, Qiao Li

Journal of Terramechanics, Volume 95, 2021, Pages 73-88, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2021.03.002.(https://www.sciencedirect.com/science/article/pii/S0022489821000239)

Abstract: Tractive effort of tracked vehicles plays an important role in military and agricultural fields. In order to solve the problem of low precision in numerical simulation of the interaction between track and sandy ground, a systematic and accurate discrete element modeling method for sandy road was proposed. The sandy ground was modeled according to the mechanical parameters measured by soil mechanics tests. The interaction coefficients of sandy soil were measured by the repose angle test and triaxial compression test combined with the corresponding simulation. On this basis, a discrete element interaction model of track-sandy ground was established, which can be used to test the tractive effort of track. Numerical simulation calculation of track model at different speeds was carried out, and the simulation results were compared with the results of indoor soil bin test for verification. The verification results show that the interaction between track and sandy ground based on DEM simulation is consistent with the actual soil bin test. The discrete element modeling method in this paper can be used to model the track and sandy ground accurately, and the simulation model can be used to test the tractive effort of tracked vehicle.

Keywords: Track; Sandy ground; Tractive effort; Discrete element method simulation; Soil bin test

Methodology for determining six components of loads arising during the operation of tillage tools in soil using a strain gauge plate transducer

J. Marcinkiewicz, M. Spadło, Ż. Staszak, J. Selech

Journal of Terramechanics, Volume 95, 2021, Pages 59-72, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2021.03.005.(https://www.sciencedirect.com/science/article/pii/S0022489821000252)

Abstract: This paper presents issues of shaping design features of load transducers allowing for identification of all six components of loads generated during operation of agricultural tools in soil. Particular attention was paid to the problem of the influence of the tool stiffness on the values measured by the transducer. Guidelines were presented on how to shape the form of this type of transducers in order to maximise their sensitivity to external forces and, at the same time, to minimise the impact of tool stiffness. The presented methods will enable the construction of measuring devices that are universal and can be used in variety of applications. An original method of determining the load values based on the measurement of stresses using the strain gauge technique and appropriate processing of the collected data is also described. Attention was also paid to the process of determining the load capacity of the transducer. These works were carried out on the basis of strength analyses using the Finite Element Method. The article also presents the procedure of the transducer calibration process and a description of a specialised test stand that is to be constructed as a part of the current project. The solutions presented in this paper are being used at the Poznan University of Technology for development and construction of a test stand in the form of a soil bin.

Keywords: FEM; Force transducer; Sensor; Soil channel; Plate transducer; Transducer calibration; Measuring sensitivity; Strain gauge

Laboratory experimental study of tire tractive performance on soft soil: Towing mode, traction mode, and multi-pass effect

Rui He, Corina Sandu, Mohit N. Shenvi, Hoda Mousavi, Justin Carrillo, Javier E. Osorio

Journal of Terramechanics, Volume 95, 2021, Pages 33-58, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2021.02.001.(https://www.sciencedirect.com/science/article/pii/S0022489821000136)

Abstract: Tire tractive performance, soil behavior under the traffic, and multi-pass effect are among the key topics in the research of vehicle off-road dynamics. As an extension of the study (He et al., 2019a), this paper documents the testing of a tire moving on soft soil in the traction mode or towing mode, with a single pass or multiple passes, and presents the testing results mainly from the aspects of tire tractive performance parameters, soil behavior parameters, and multi-pass effect on these parameters. The influence of tire inflation pressure, initial soil compaction, tire normal load, or the number of passes on the test data has been analyzed; for some of the tests, the analysis was completed statistically. A multi-pass effect phenomenon, different from any phenomenon recorded in the available existing literature, was discovered and related to the ripple formation and soil failure. The research results of this paper can be considered groundwork for tire off-road dynamics and the development of traction controllers for vehicles on soft soil.

Keywords: Terramechanics; Tractive performance; Tire test; Soil compaction; Multi-pass effect; Tire inflation pressure; Rolling resistance; Tire off-road dynamics; Rolling radius

Fuzzy logic based automatic slip control system for agricultural tractors

Serhat Soylu, Kazım Çarman

Journal of Terramechanics, Volume 95, 2021, Pages 25-32, ISSN 0022-4898

https://doi.org/10.1016/j.jterra.2021.03.001.(https://www.sciencedirect.com/science/article/pii/S0022489821000197)

Abstract: In this study, a fuzzy-based automatic slip control system was developed for agricultural tractors. The developed system continuously measures the amount of slip that occurs during the tillage activities and automatically changes the operation depth of tillage equipment according to the amount of increase in the slip value. The amount of slip occurring on the driving wheels was applied as a separate input to the designed fuzzy control system (FCS) and at the fuzzy rule base, it was decided how much the depth of tillage would be reduced. The system was mounted on an agricultural tractor and trials were carried out in actual field conditions. The results of the tillage trials performed with the developed FCS were compared separately with the results of the tillage trials performed with an operator control (OC) without using any automatic control system. As a result of the trials, compared to the operator control, it was determined that in the tillage activities carried out with FCS, there were 42% decreases in slip values, 30% decreases in draft force values, 44% decreases in fuel consumption values and 5% increases in field work performance values. It was also observed that there were 10% changes in tillage depth.

Keywords: Agricultural machinery; Automatic control system; Fuel efficiency; Fuzzy; Wheel slip