Christian Schindler

Investigation of Tire-Soil Interaction with Analytical and Finite Element Method#

This article is devoted to the modeling of tire–soil interaction with the analytical and finite element method (FEM). Different from the traditional tire–soil interaction models in which the contact between tires and soils is described by nonlinear springs in the normal direction, the new analytical model added dampers accounting for the soil damping effects. A nonlinear three-dimensional tire–soil interaction model with the FEM, which takes into consideration the tire treads and belt/carcass layers, was validated by measuring tire vertical stiffness and contact stress. The conversion of the Modified Drucker-Prager/Cap soil model to the analytical soil model was demonstrated as well. The simulations for investigating the dynamic behavior of a bias tire running on the soft soil were performed. Good agreement was observed based on the simulation results obtained from these two tire–soil interaction models. However, experimental validation is necessary before the models can be further applied in the prediction of off-road vehicle dynamics.

Assessment of wheel loader vibration on the riding comfort according to ISO standards

Vibration accelerations were measured on a compact wheel loader during 11 operations with two drivers and with/without the activated boom suspension system (BSS). Two standards, ISO 2631-1 (1985) and ISO 2631-1 (1997), were used to assess the effect of wheel loader vibration on comfort. The assessment results of ISO 2631-1 (1985) showed that vibration in the frequency range from 4 to 20 Hz in the vertical direction and in the frequency range from 1.6 to 3.15 Hz in the vertical and driving directions plays an important role in comfort assessment. The overall total values of vibration measured on the wheel loader in all operations exceeded the ‘uncomfortable’ boundary specified in ISO 2631-1 (1997). The speed had a larger influence on the vibration intensity than the bucket load, the BSS or the driver biodynamic response during driving. During driving and V-cycle, the difference of vibration intensity with two drivers in the z-direction is larger than that in the x- and y-direction.

Three-dimensional finite element and analytical modelling of tyre–soil interaction

Tyre–soil interaction models were developed for the investigation of tyre dynamic behaviours with two different approaches: finite element method and analytical method. In the finite element model the 3D tyre was modelled as a non-linear solid assembly consisting of tread block, belt and carcass layers, sidewall, beads and rim, and the soil modelled as a 3D object was attributed with the elasto-plastic mechanical behaviour. In the analytical model the contact between deformable tyre and soft soil is described by non-linear springs and dampers in the radial direction and shear stress-displacement model in the tangential direction. The equations accounting for the analytical model were integrated in the multi-body simulation software-ADAMS. Simulations with these two different tyre–soil interaction models were carried out to study the longitudinal slip-longitudinal force and slip angle-lateral force relationship.

Surface Erosion of Carbon Steel 1045 During Waterjet Peening

The present study investigates the effect of waterjet treatment on the surface characteristics of the carbon steel 1045. The effect of waterjet treatment parameters namely number of jet passes and pressure was investigated. An increase in the number of jet passes as well as pressure leads to a higher roughness and more erosion of the surface. The damage features consist of various fracture mechanism modes occurred at the initial and evolved damage stage. The ferrite phase experienced more damage than the pearlite phase. However, the damage was more concentrated along the grain boundaries. The shearing force from the jet lateral flow raised the circumferential rim and created lateral cracks and sub-tunnels which might eventually be removed in the subsequent jet passes. The hardness of the treated specimens increased with an increase in the number of jet passes and pressure.

Integration of digging forces in a multi-body-system model of an excavator:

The digging process using an excavator bucket was modelled, with the objective of introducing the interaction with the environment into the multi-body-simulation method. With today’s software tools, the dynamic behaviour of complex machinery can be effectively simulated. However, interaction with the environment, especially with soil is very challenging. This paper aims to contribute to meeting the challenges in this field of simulation. The given implementation makes use of analytical approaches originating from classical soil mechanics. After an analysis of the digging process, excavating tools, digging mechanisms and existing force calculation methods, approaches based on the ‘fundamental earthmoving equation’ and the ‘cavity expansion theory’ were used to model bucket filling, soil transport and bucket emptying along with accompanying forces throughout the described process. The simulation results are compared with experimental data available in publications. The main finding of this paper is a co-simulation, with a multi-body-simulation model capable of estimating the digging forces dynamically, with very high accuracy for low cohesion soil. Furthermore, the model also visualises the geometry of the soil surface, and the bucket contents, during the excavation cycle, in 2D, and can be extended for use in 3D.

Structural safety of trams in case of misguidance in a switch

Tram vehicles mainly operate on street tracks where sometimes misguidance in switches occurs due to unfavourable conditions. Generally, in this situation, the first running gear of the vehicle follows the bend track while the next running gears continue straight ahead. This leads to a constraint that can only be solved if the vehicles articulation is damaged or the wheel derails. The last-mentioned situation is less critical in terms of safety and costs. Five different tram types, one of them high floor, the rest low floor, were examined analytically. Numerical simulation was used to determine which wheel would be the first to derail and what level of force is needed in the articulation area between two carbodies to make a tram derail. It was shown that with pure analytical simulation, only an idea of which tram type behaves better or worse in such a situation can be gained, while a three-dimensional computational simulation gives more realistic values for the forces that arise. Three of the four low-floor tram types need much higher articulation forces to make a wheel derail in a switch misguidance situation. One particular three-car type with two single-axle running gears underneath the centre car must be designed to withstand nearly three times higher articulation forces than a conventional high-floor articulated tram. Tram designers must be aware of that and should design the carbody accordingly.

Entwicklungsprozess für cybertronische Produktionssysteme

Kurzfassung Die zunehmende Vernetzung in der Produktion eröffnet neue Möglichkeiten zur Steigerung der Flexibilität von Produktionssystemen. Hierzu leisten cybertronische Systeme einen wichtigen Beitrag. Um ihr Potenzial vollständig auszuschöpfen, müssen cybertronische Produkte und Produktionssysteme integriert entwickelt werden. Dieser Beitrag zeigt die einzelnen Entwicklungsschritte auf, die innerhalb eines solchen, integrierten Entwicklungsprozesses aus Perspektive der Produktionssystemplanung notwendig sind.

Investigation of the effect of safety belt on the seat transmissibility

Seat transmissibility is used to evaluate the vibration attenuation performance of seats. Because the seat and the driver interact with each other, the seat transmissibility is affected by the dynamic characteristics of the driver. The constraint on the movement of the driver caused by the safety belt results in the change of the seat–driver dynamics and the seat transmissibility. Vibration accelerations were measured on the seat cushion and at the seat base on a medium size wheel loader when the driver wore a lap belt or a four-point seat harness. The seat effective amplitude transmissibility value and the seat transmissibility derived from the cross spectral density method were analysed to investigate the effect of safety belt on the seat transmissibility. Two multi-body models of the seat–driver system were built in MATLAB and their parameters were identified in cases where the driver wore the lap belt or the four-point seat harness. Based on the analysis of these parameters, the way how the safety belt affects the seat–driver dynamics and the seat transmissibility is studied.

Application of analytical and finite element method in tyre-soil modelling

This paper describes the development of tyre-soil interaction models to investigate the dynamic behaviour of a tyre rolling on soil. An analytical tyre-soil model is integrated into a Multiple Body System (MBS) software interface with the application of corresponding subroutines. It is flexible enough to define the properties of different tyres and soils such as tyre stiffness and dimensions of soil ground in the respective property files. The Finite Element Method (FEM) is used to compare the respective forces and velocities in the SAE tyre coordinate system under different combined conditions of loads and sinkages. The relations between soil sinkage, velocity, vertical load, drawbar pull and slip ratio are analysed based on the simulation results.

Multiscale Finite Element Modeling of Wheel–Rail Rough Normal Contact Measurements Using Pressure Measurement Film

ABSTRACT This article presents a multiscale modeling approach for reproducing the measurement of the wheel–rail contact area using pressure measurement film when the roughness of the mating surfaces cannot be neglected. The microscopic contact behavior between the film and test bodies was investigated with the aid of the finite element method based on scanned surface data and was later implemented in a macroscopic model that reproduced the contact area measurement procedure. The validity of the modeling technique was confirmed by the consistency between simulated results and experimental measurements. It was also demonstrated that the response of the pressure measurement film to roughness variations is consistent with the governing contact mechanics.