The paper presents recent method developments and activitiescarried out in the eld of load simulations and fatigue assessmentsat Volvo CE on the articulated hauler (AH) platform. Items discussedmor ...

A co-simulation scheme is developed that couples an MBS wheel loader model with the ITWM/DEM code for soil simulation, in order to realize a framework in which different loading maneuvers can be si ...

Articulated haulers are suited for any kind of transports in difficult terrain. The concept was developed from an agricultural tractor in the 1960’s by Volvo. The main features are the hydraulic steering, the individual front and rear frames connected with a rotational hitch joint, all-wheel drive and large tires. These features give the extraordinary terrain capability. Complete vehicle simulations support development of stability, handling and ride comfort properties during early development of the hauler. Complete vehicle simulations can also be utilized to extract design loads. This paper presents the current status in this field.The complete vehicle MBS simulation model includes flexible bodies, hydraulic system, tires and powertrain. A refined powertrain model in Simulink is used for the analysis presented. The environment is defined by the road and the driver. A comfort track road is used for comfort evaluations and a digitalized endurance test road for load predictions. The driver model aims to follow the given target path and velocity.Simulation and measurement signals are compared by means of relevant spectra; load ranges, level crossings and Power Spectral Density. A scalar measure is defined by the equivalent value to carry out comparisons between simulations and test. Fatigue load simulations need an accurate dynamic description of the vehicle, capturing low frequency excitation. The results shows that the load simulation captures the frequency peaks below 15 Hz, although there are some differences in magnitude and peak frequency. When simulated and measured equivalent values are compared most entities are in the range between 1/2 and 2 regarding estimated life. Further improvements are possible but the simulated load quality should also be related to other uncertainties in the fatigue evaluation process.

During the development of construction equipment, usage of virtual complete vehicle models has become an important tool for a rapid development process maintaining low risk. Many properties e.g. stability, handling and ride comfort are today simulated and secured early in the product development process with high accuracy. During the last years effort have been directed to also extract design loads for fatigue life calculations from the complete vehicle models. This paper gives an status overview regarding articulated haulers, see figure 1. This kind of vehicle have extra ordinary terrain capability which is accomplished by hydraulic articulated steering, stiff individual tractor and load frames connected with a rotational joint and allwheel drive together with large tires. The vehicles are also equipped with automatic differential locks, automatic powershift transmission and wet brakes with cooling for high gradeability. Figure 1: Articulated hauler in rough terrain application. To extract loads from the virtual models implies additional requirements compared to normal handling simulations especially concerning the ability to cover higher frequency content. Models with sufficient resolution have to be used for accurate representation of the road surface, the tires, the suspension system and the frames. To solve the vehicle dynamics but also to build and maintain several different levels of the subsystems models and how they are assembled, ADAMS/Car[1] have been used since several years. At present stage, the road surface of the endurance test tracks is obtained by laser scanning and converted to the OpenCRG[2] format. The tires make use of Ftire[3], a physical tire with high resolution. The hydraulic system (hydraulic suspension and steering) are modeled in Amesim[4] and the simulations are made in co-simulation mode together with ADAMS. The exchange of information between the two solvers are manage by a General State Equation (GSE) and a special interface block in Amesim. Some key components (frames, hitch and body) need to be flexible in order to account for the flexibility of the entire vehicle. For this purpose, the software makes use of Craig-Bampton reduction and an additional orthogonalization step. Figure 2 shows an assembled articulated hauler vehicle model and the Amesim hydraulic model executed in co-simulation mode. The ultimate target for the virtual models is to deliver accurate component loads extracted from the full vehicle models, as input to durability calculations. Fatigue life calculations of large welded structure Figure 2: Hauler vehicle model and Amesim hydraulic model. as e.g. the front and the rear frames, is continuously developed and is mature to use component loads directly in the time domain. This is accomplished through extensive usage of the detailed notch modeling of the weld, load superposition and time based fatigue evaluation using critical plane theory[5] applied to the notch stresses. Besides a detailed status description this paper presents comparison between fatigue loads from load measurements and virtual simulations. To compare the results in a quantity that is related to fatigue, range-pair information obtained from rainflow counting[6] together with the equivalent load range (a scalar value) defined as Rekv = ( kt 1000 N ∑ i=1 niRi )(1/m)

•Correlation between test and FE analysis of a full scale wooden structure.•The parameter evaluation showed large influence of wood beam material properties.•Tied connection was used to simulate screwed junctions.•Spring/dashpot elements were used to simulate elastomer junctions.•It was possible to capture the behaviour of the floor with the FE model.

Residential timber framed buildings have in some cases received complaints from inhabitants due to structure-borne sound at low frequencies, even if the building meets the regulations with respect ...

A moving rail vehicle may cause propagating waves to the surroundings potentially leading to detrimental effects for the track construction, nuisances for the surroundings and interference with delicate electronic equipment. A full computational model should be able to couple a correct simulation of the rigid body motion of the different train parts with accurate prediction of the solid wave propagation in the ground. This paper integrates the dynamics of the vehicle and the elastic soil into one monolithic system. Equations of motion for the train have been merged the system representing the FEM problem for the rest of the structure. Three models of modern high-speed locomotives were run over a solid finite element model of a rail structure.

The solution of linear systems of equations is the most time-consuming part in large-scale implicit FE computations of wave propagation problems. Traditionally, direct solvers have been used but recent developments of iterative solvers and precondition techniques may impose a change. In particular, preconditioning by multigrid seems to be favorable for finite element (FE) applications since it has a natural interpretation and substantially improves the rate of convergence of the conventional iterative solvers.The multigrid preconditioner uses a sequence of grids on which the fine-grid residual forces are prolongated to coarser grids and computed corrections are interpolated back to the fine grid such that the fine-grid solution successively is improved. By this technique, large 3D problems, invincible for solvers based on direct methods, can be solved in acceptable time and at low memory requirements.The proposed adaptive multigrid FE-method combines adaptivity and multigrid solution strategy in a sophisticated manner. The sequence of computational grids is successively refined (adapted) and generated according to the guidance of a posteriori error estimates until the solution fulfils a predefined accuracy specification. In contrast to standard adaptive procedures where rejected grids are deleted, the adaptive multigrid algorithm uses previous solution and generated grids to speed up the solution process.A refinement strategy based on element splitting and introduction of hanging nodes requires special care since the constraint equations of the hanging nodes are incorporated in the system by usage of Lagrange multipliers. The approach leads to indefinite systems and hence a special preconditioner that enforces the constraint equations to be fulfilled while iterating has been developed.The paper presents results using the adaptive multigrid procedure on an elasto-plastic wave propagation problem.

The displacement field in quasi‐brittle material is localized into narrow fracture zones during the process of decohesion. The numerical modelling of the physically propagating displacement discontinuities is considered to be inherently difficult. In this paper, the introduction of continuous discontinuities into the finite element formulation is based on the extended finite element method (X‐FEM). This paper extends the theory by further incorporating arbitrary discontinuities in the approximation and presenting numerical procedures to handle several fields of discontinuities. The discontinuous approximation is accomplished by usage of basis functions of very limited support; only non‐zero in the elements containing the crack. Moreover, the introduction of discontinuities in a continuum is discussed and a robust numerical procedure is proposed. Further, the mechanical behaviour of cracks in a quasi‐brittle material largely governs the overall mechanical response of the material, and the implementation of a cohesive crack model based on anisotropic damage coupled to plasticity is emphasized. Numerical examples for both static and dynamic, transient, loading show that the proposed X‐FEM format in combination with the cohesive crack model has a good performance and leads to an efficient implementation. Finally, the proposed forward method for propagation of cracks and introduction of new ones is robust and stable. Copyright © 2006 John Wiley & Sons, Ltd.

High-quality and efficient means of transport is of high priority in the modern society. Railway traffic is environment friendly and economically very competitive for both freight and personal transports at mid-range distances. Although the railway technology has been improved substantially during the last decades, generated vibrations still impose annoyances to the surroundings environment and leads to deterioration of the track structure.

Wave propagation in solid materials is of great interest in many engineering applications. The fact that the area of interest changes with time creates a number of computational problems such as the need for a mesh density varying in space and time. This means that the mesh must be continuously updated and controlled, rendering a large demand of computer effort.In certain applications like railway mechanics there are mobile loads. A load speed close to the natural speed in the underlying soil causes specific problems, shock waves being one of them. The transmitted waves have to leave the defined finite element domain without reflection, which imposes a need for certain modelling methods. The paper will deal with quality controlled FE-procedures for wave propagation including error estimation and mesh refinement/ coarsening. As an application an important problem from railway mechanics is considered. When a high-speed train approaches an area with decreasing thickness of underlying soft soil on a stiff rock it is expected that the reflection of the wave will increase the total amplitude of the wave. We will study this problem with the procedures described above in full 3D with partly absorbing boundaries. (c) 2005 Elsevier B.V. All rights reserved.

For finite element analysis of wave propagation in an elastic medium surrounded by an adjacent “infinite” region, the introduction of external boundaries introduces severe reflection problems, which may ultimately distort the solution. Analysis based solely on finite elements is not sufficient, as the boundary will add unwanted reflections to the grid. This paper explores the approach of introducing a virtual element layer to absorb the outgoing waves. The results indicate that reflections could be reduced to a large extent.