Edwin A. H. Vollebregt

• PhD
• Senior Researcher at Vtech CMCC

This paper presents our new solver BCCG+FAI for solving elastic normal contact problems. This is a comprehensible approach that is based on the Conjugate Gradients (CG) algorithm and that uses FFTs. A first novel aspect is the definition of the "FFT-based Approximate Inverse" preconditioner. The underlying idea is that the inverse matrix can be app...

This paper proposes a new way of considering wheel–rail contact in multibody systems simulation that goes beyond the traditional planar constraint and elastic approaches. In this approach, wheel–rail interaction is modelled as a force element with pressures and shear stresses distributed over a contact area that may be curved, supporting conformal...

This paper surveys advances in the understanding and modelling of wheel–rail creep forces. The main focus is placed on tribological aspects, for which significant progress was made in the past two decades. We emphasise the role played by the surface conditions, i.e. the presence of liquid and solid layers, surface roughness, and near-surface plasti...

This report presents the results of a project undertaken to advance modeling of wheel-rail rolling contact with frictional creep forces. The research team established sub-models for the elastic and plastic shearing of third body layers, heating of the contacting surfaces, and the effects of these phenomena on the coefficient of friction. They also...

50 free online copies of the article: https://www.tandfonline.com/eprint/DDHR8IM23V8BRKYAVWYV/full?target=10.1080/00423114.2025.2480819

free online copies (first 50): https://www.tandfonline.com/eprint/WWQGHB3ZSQ4M6XJYCEAQ/full?target=10.1080/00423114.2023.2228438

Additional weighting factors are introduced into the smoothing spline, proportional to the sampling spacing, in agreement with a mathematicalphysical model for a thin elastic beam at small deflection. This improves the robustness of the spline with respect to variations in spacing of the data. The spline is then shown to correspond to a low pass (l...

Previous papers on wheel/rail contact analysis paid only limited attention to the smoothing of measured wheel and rail profiles. This may be unrightly so, because smoothing, or the lack thereof, may strongly affect the outcomes of a simulation. To improve smoothing procedures, this paper presents benchmark profiles for the evaluation of smoothing m...

The changes in wheel-rail traction coefficients under wet and oil-contaminated rail surfaces are evaluated using the state-of-the-art Virginia Tech-Federal Railroad Administration (VT-FRA) roller rig. This one-fourth scaled test rig provides a controlled environment to measure real-time contact forces under pre-defined conditions. In addition, the...

This paper presents a correction and an extension of the FASTSIM approach for the computation of the wheel-rail creep forces. The correction concerns the variants of FASTSIM using a single flexibility value. Kalker's formula for this gives up to 41% too large flexibility in situations with mixed creepage, underestimating the creep forces by 29%. Th...

Rail damage prediction is a complex task because it depends on numerous tribological parameters and the dynamic conditions produced by the vehicles operating at different speeds and configurations. Shakedown maps and Whole-Life-Rail-Model/T-Gamma have been used to predict rail damage, but they involve assumptions that may reduce their accuracy. Thi...

The exact contact theory is an efficient alternative to the more general yet computationally expensive Finite Element Method for the detailed study of elastostatic contact problems. For its application in conformal contact problems, the exact contact theory needs to be fed with influence coefficients (ICs) appropriate for non-planar solids. An anal...

The use of detailed wheel/rail contact models has long been frustrated by the complicated preparations needed, to analyse the profiles for the local geometry and creep situation for the planar contact approach. A new software module is presented for this that automates the calculations in a generic way. Building on many components developed by othe...

Locomotive-track interaction is a multidimensional task because it goes in many directions depending on the aim of the investigation. One such direction relates to wheel or track damage produced by traction and braking of locomotives under different train operational scenarios. The best option for performing wheel or track damage studies is to use...

This paper considers the problem of computing the stresses inside an elastic half-space for prescribed normal and shear surface tractions. It is shown that piecewise constant loading elements result in numerical artifacts near the element boundaries. This is resolved by approximating the surface loading using bilinear elements. Three different impl...

Friction is an interesting topic because of its important influence in wear during wheel-rail contact and vehicle system dynamics. To be able to reduce wear while maintaining safe and fast operation of the train network a better understanding of friction and the role of friction modifiers is key. Inspired by the approaches of Tomberger [1] and Meie...

There has been a mistake in the work presented in the paper ‘Solving conformal wheel–rail rolling contact problems’ [Vollebregt E, Segal A. Solving conformal wheel–rail rolling contact problems. Veh Syst Dyn. 2014;52(suppl. 1):455–468] on conformal contact analysis. This concerns the reference results for the Hertzian/planar test-case. The ‘effecti...

The ‘simple double-elliptical contact’ (SDEC) approach by Piotrowski et al. [The Kalker book of tables for non-Hertzian contact of wheel and rail. Vehicle Syst Dyn. 2017;55:875–901] generates a-symmetrical contact patches in an elegant way. This allows to extend the table-based approach for the wheel–rail creep force calculation towards non-Hertzia...

Common models for wheel/rail contact typically start from a prescribed creepage or imposed contact force. This excludes the dynamical interaction between the two where each one responds to the other. This paper introduces a different approach where friction is related to the local deformation in and around the contact patch. This leads to forward a...

Using the world-fixed grid, with time steps such that the wheel traverses less than a grid spacing per time step, the simulation doesn't reach a steady state but displays grid-dependent saw-tooth behavior instead. 2D Cattaneo to Carter test-case at fixed creepage cksi=0.024%.

In this report we discuss a difficulty of using finite element methods for problems with velocity-dependent friction. Using the penalty approach with explicit time-stepping, an auxiliary time-step restriction is found that's related to the strength of falling friction.

The CONTACT software created by Kalker and further developed by Vollebregt has recently been integrated in dynamical simulation software like RecurDyn and libraries usable in Matlab or C. When such larger packages impose small timesteps compared to the grid-size used, a wiggle-like phenomenon arises. Additionally, transient time-stepping appears to...

** Full text available(first 50): http://www.tandfonline.com/eprint/HfZjgfUPkJGTJRCCbhnm/full ** A novel approach is proposed in this paper to deal with non-Hertzian normal contact in wheel–rail interface, extending the widely used Kik–Piotrowski method. The new approach is able to consider the effect of the yaw angle of the wheelset against the ra...

The boundary element method (BEM) is widely used in fast numerical solvers for concentrated elastic contact problems arising from the wheel-rail contact in the railway industry. In this paper we extend the range of applicability of BEM by computing the influence coefficients (ICs) numerically. These ICs represent the Green's function of the problem...

This paper presents a simulation approach for forecasting the effect of track irregularities on rail damage development in the forms of rolling contact fatigue (RCF) and wear. This approach consists of a high resolution vehicle-track interaction model, a detailed non-Hertzian wheel/rail contact model and an accumulation procedure for the tangential...

The importance of the wheel/rail contact forces in railway engineering cannot easily be overstated, affecting safety, ride quality and economics of the railway system. This presentation reviews our understanding to date and describes recent developments in contact modelling.

Simulation results indicate that the frictional contact force between wheel and rail has a tendency to oscillate at frequencies in the range 100-300 Hz. This goes against the general idea that non-steady rolling effects die out quickly. The forward and angular velocities are oscillating at the same time with opposite phase, leading to the so-called...

Measured locomotive traction coefficients show deviations from Kalker’s original theories. These ”real-world effects” are discussed and modelled using the Extended CONTACT software. We describe the effects on vehicle dynamics response in different circumstances.

This paper presents a fast numerical solver for a nonlinear constrained optimization problem, arising from 3D concentrated frictional shift and rolling contact problems with dry Coulomb friction. The solver combines an active set strategy with a nonlinear conjugate gradient method. One novelty is to consider the tractions of each slip element in a...

In this paper we show that falling friction poses a principal difficulty for the FASTSIM algorithm. Using velocity-dependent μ leads to discontinuities in the tractions, displacements and slip velocity. These discontinuities are due to the local and instantaneous relations that are used. They are circumvented in different, unsatisfactory ways in th...

Railway track asset management may be improved by looking forward, understanding why rail damage occurs. This requires detailed insight in the forces and stresses exerted on rails during vehicle passing. New capabilities on this are presented using the Kalker CONTACT add-on to SIMPACK Rail.

Design of railway infrastructure is largely done on a basis of trial and error, with limited use of numerical simulation and structural analysis. Costs could be reduced by proper dimensioning and maintenance, along with the creation of a catalogue of degradation processes and failure mechanisms, consolidating and combining existing knowledge and so...

Numerical simulation of the behavior of rail vehicles requires a frictional contact model for the wheel–rail contact forces that must be fast and detailed. A comment on Kalker's original theories is that they describe well only the situation for scrupulously clean surfaces. Measured creep versus creep force curves show two important deviations: a r...

This paper presents a full multigrid (FMG) technique, which combines a multigrid method, an active set algorithm and a nested iteration technique, to solve a linear complementarity problem (LCP) modeling elastic normal contact problems. The governing system in this LCP is derived from a Fredholm integral of the first kind, and its coefficient matri...

The stresses between railway wheels and rails can be computed using different types of contact models: simplified methods, half-space-based boundary element approaches and finite element models. For conformal contact situations, particularly the contact between flange root and rail gauge corner, none of these models work satisfactorily. Finite elem...

This paper aims to develop a fast multigrid (MG) solver for a Fredholm integral equation of the first kind, arising from the 2D elastic frictional contact problem. After discretization on a rectangular contact area, the integral equation gives rise to a linear system with the coefficient matrix being dense, symmetric positive definite and Toeplitz....

Existing conjugate gradient (CG)-based methods for convex quadratic programs with bound constraints require many iterations for solving elastic contact problems. These algorithms are too cautious in expanding the active set and are hampered by frequent restarting of the CG iteration. We propose a new algorithm called the Bound-Constrained Conjugate...

In this paper the influence of a velocity-dependent friction law on the interactions inside the contact patch between a rolling wheel and a rail is presented, assuming that the quasi-static approach is still applicable. In the model, traction builds up until a critical configuration is reached, after which an instantaneous reset occurs. The system...

This paper presents an approach for assessing the accuracy of different frictional rolling contact theories. The main characteristic of the approach is that it takes a statistically oriented view. This yields a better insight into the behaviour of the methods in diverse circumstances (varying contact patch ellipticities, mixed longitudinal, lateral...

In this paper we present recent and ongoing developments with respect to Kalker's CONTACT software. One notable achievement concerns the extension of the model with respect to effects of roughness, contaminants and temperature. These are included in an indirect, parameterized way, by adding an interfacial layer and by refining the friction law. Wit...

Friction between sliding surfaces decreases as the velocity of sliding increases (‘falling friction’). This paper investigates the velocity-dependent friction relationships in non-Hertzian models of wheel-rail rolling contact. The effect of falling friction on tangential stress distribution and slip is examined. In otherwise steady rolling with con...

In this paper we consider the frictional (tangential) steady rolling contact problem. We confine ourselves to the simplified theory, instead of using full elastostatic theory, in order to be able to compute results fast, as needed for on-line application in vehicle system dynamics simulation packages. The FASTSIM algorithm is the leading technology...

In order to study the dynamic behaviour of railway vehicles, and to numerically assess wear and RCF, one must solve the frictional rolling contact problem. Drawbacks of the variational model "CONTACT" by Kalker [14] are its first order accuracy and its consequent high computation times. In this paper we present two important leads in pursuit of sec...

In his extensive career, Joost Kalker worked on many contact phenomena. For this, he developed various theories, which were accompanied by algorithms and computer programs. Most notably, these are the FASTSIM algorithm for quickly evaluating the nonlinear creep-force law in vehicle dynamic simulations, the CONTACT program for the exact theory of ro...

A new method for wetting and drying in two-dimensional shallow water flow models is proposed. The method is closely related to the artificial porosity method used by different authors in Boussinesq-type models, but is further extended for use in a semi-implicit (ADI-type) time integration scheme. The method is implemented in the simulation model WA...

The trend towards integrated modeling has been there for at least ten years and can be seen in many different areas. However, new possibilities for integrated modeling arise due to the rapid increase of computer speeds, for instance through parallel computing, and through the advent of new software development techniques. Whereas different models w...

The Dutch Rijkswaterstaat uses simulation models extensively in carrying out its various tasks, among which are the protection of the country from flooding and the management of shipping routes and ports. Different applications of the models lead to large scale computations. Furthermore the continuing increase in level of detail of the simulations...

The adjoint method has been derived and implemented for solving inverse 3D shallow water flow modelling problems. Attention is concentrated on estimating the harmonic constants in the open boundary conditions, the space varying friction parameter, the space varying viscosity parameter and the depth values in a 3D shallow sea model of the entire Eur...

This paper discusses the approach that is being taken for parallelising the WAQUA/Kalman software of the Dutch Institute for Coastal and Marine Management. This software is used for numerical simulation of flow and transport phenomena in coastal waters and incorporates a Kalman filtering procedure to assimilate observational data into the simulati...

This paper discusses the approach that is being taken for parallelising the WAQUA/Kalman software of the Dutch Institute for Coastal and Marine Management. This software is used for numerical simulation of flow and transport phenomena in coastal waters and incorporates a Kalman filtering procedure to assimilate observational data into the simulatio...

Frictionless rough contact problems have been studied in great detail by J. A. Greenwood and his co-workers. The only thing that actually seems missing is a simulated figure of the real contact between two rough bodies. Such a figure will be provided. Frictional rough elastic contact, on the other hand seems to be term incognita, and we intend to e...

this report we present and analyze performance measurements on two parallel computing platforms: a cluster of workstations and a Parsytec PowerXplorer. This shows how the performance is composed, which gives insight in the prospects of parallel computing for shallow water simulation. The parallelization strategy that is used for TRIWAQ is based on...

A problem with most present-day CFD packages is that they are difficult to port to parallel hardware. Another difficulty with large scientific packages arises when they must be integrated. The cause of these problems is loss of information, which could be avoided by recording the development trajectory and the design choices. In the current paper a...

. An important obstacle for an industrial break through of parallel computing is the complexity of parallel programming and of porting existing simulation packages to parallel computers. In the current paper a rigorous approach is worked out which simplifies the port of a package and parallel programming in general. The approach offers flexibility...

A formalism is proposed for describing finite difference calculations in an abstract way. The formalism consists of index sets and stencils, for characterizing the structure of sets of data items and interactions between data items (“neighbouring relations”). The formalism provides a means for lifting programming to a more abstract level. This simp...

Parallel software development must face the fact that different architectures require different implementations. Flexibility in modifying parallel methods and software is necessary because the efficiency of algorithms is dependent on the characteristics of the target computer. Furthermore different parallel computers require different implementatio...

Domain decomposition is a well known technique in parallel computing. It requires the decomposition of a problem domain into sub-domains. This involves also a decomposition of the data structures for the problem into substructures, one for each sub-domain. If the data structures are complex, then the decomposition of the data structures may be a co...

An iterative method is described that solves the constrained minimization of a convex function, when the constraintsg j(x 1,...,x n)≤0 are functions of only a few variables and can be partitioned in some way. A proof of convergence is given which is based on the fact that the function values that are generated decrease. The relation to the nonlinea...

Accurate predictions of flows and transport in the continental shelf region can be obtained using a numerical simulation of the three dimensional shallow water equations. As more powerful computers become available, the grids that are used in these simulations can be much finer, making the results more reliable. This article describes a first imple...

. An important obstacle for an industrial break through of parallel computingis the complexity of parallel programming and of porting existing simulation packagesto parallel computers. In the current paper a rigorous approach is worked out whichsimplifies the port of a package and parallel programming in general. The approach offersflexibility in m...

The numerical algorithm in the simulation package TRIWAQ is analysed for inherent parallelism. One equation solver that is used for the discretised momentum equations appears to be purely sequential. A comparison with alternative solvers for an advection diffusion test problem indicates however that it is extremely effective on a sequential compute...

In this paper, a short overview of project 3, “Advanced Flux Modelling”, in the NOWESP project of the MAST II programme is given. The computational requirements of large scale 3-D flow and transport models of the North-West European Shelf are considered. The possibilities and implications of massively parallel processors for the simulation of these...

The package TRIWAQ is used for simulation of flow and transport in shallow seas and estuaries. Parallelisation of TRIWAQ is needed to reduce the computing time that now puts a restriction to the accuracy of the simulations. Automatic parallelisation is unsuccessful for this package because the algorithms and data-structures that are used are inhere...