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Publications (27)
Simple and computationally efficient drill string models running real-time describing motion in all axes in directional wells are important for the implementation of closed-loop control and assisted monitoring during drilling operations. This paper proposes a new simplified three-dimensional model based on a parametric curve and lumped-parameter mo...
In this study, the Absolute Nodal Coordinate Formulation (ANCF) is examined in the framework of the Arbitrary Lagrangian–Eulerian (ALE) formulation for cable simulation. The objective is to determine the stability, efficiency, and accuracy in different frequency domains for two different numerical time integration methods. The methods being compare...
This study presents a theory describing surge and swab pressure when a drillstring is hanging in the slips of a heaving vessel. Downhole pressure measurement shows high pressure pulses in these instances, higher than can be explained with simple steady-state calculation. Several factors and parameters affect this pressure, such as annulus geometry,...
A unique dovetail-based test fixture for fretting fatigue was designed and is demonstrated with a combined experimental and numerical campaign. Fretting fatigue damage is analysed and correlated with numerical analyses using a modern Ruiz formulation and Findley critical plane parameter with the Theory of Critical Distances. Initial test results sh...
Fretting and fretting fatigue are important considerations to be made in the design and development of medium‐speed reciprocating engines. Predictive capabilities for safe‐life design often rely on very simple empirical parameters and experience. Practices are briefly reviewed and opportunities for more sophisticated methodologies are highlighted....
Multiaxial fatigue and the application of critical plane criteria are briefly reviewed. Methods to increase the efficiency of such criteria are discussed. A simple methodology is also presented where the critical plane search space is discretised using triangular elements and adaptively refined. It is shown to increase accuracy in the damage search...
This paper presents a multidiscipline dynamic simulation tool for fatigue testing. A non-linear finite element formulation embedding control system modeling is augmented to include fatigue analysis based on a mathematical representation of virtual brittle lacquer and strain rosettes. A new efficient method for rosette strain calculations based on s...
Rotor stator interaction in high-head Francis turbines has led to several failures in recent years. Increasing efficiency demands require design optimization of the turbine components, which may lead to thinner profiles. Not only can component not withstand the given loads; quite often one or more of their natural frequencies coincide with that of...
The ability to predict a francis runners dynamic response to the exciting forces is paramount to avoid unwanted disintegration of the turbines components. In this article, each of the principal factors contributing to the dynamic response of the runner; eigenfrequency, mode shape, damping and pressure force, is individually examined and compared to...
Rotor stator interaction in high-head Francis turbines has led to several failures in recent years. Increasing efficiency demands require design optimization of the turbine components, which may lead to thinner profiles. Not only can component not withstand the given loads; quite often one or more of their natural frequencies coincide with that of...
he importance to correctly predict the natural frequency of a turbine runner have been demonstrated several times. It is now common practice to include the added mass effect of the surrounding water when calculating the natural frequencies. In this paper the added mass effect of water on a simplified low specific speed francis turbine runner is exp...
The progress in fretting fatigue understanding and predictability is reviewed, with engineering applications in mind. While industrial assessments often relies on simple empirical parameters, research in fretting fatigue should allow the design engineer to improve confidence in the fretting fatigue analysis.
Fretting fatigue cracks often form in mu...
High head Francis runners are subject to pressure pulsations caused by rotor stator interaction. To ensure safe operation of such turbines, it is important to be able to predict these pulsations. For turbine manufacturers it is often a dilemma whether to perform very advanced and time consuming CFD calculations or to rely on simpler calculations to...
As a result of stresses induced by rotor-stator interaction, a number of high head Francis turbines have failed in the past 15 years. This paper uses the methods described by Seidel et al. and Monette et al. to calculate the dynamic stresses and pressures of three different high head Francis turbines, and compares the results with prototype measure...
A method for performing modal analysis of undamped active flexible multibody systems with collocated sensors and actuators in a finite element environment was recently developed by the authors. In this paper, the theory is further expanded to include systems with non-collocated sensors and actuators, damping and steady-state error elimination. The...
In low-permeability and low-porosity reservoirs, oil is trapped in the rock and cannot be extracted by conventional recovery. In this case, well stimulation techniques such as fracturing can be used to increase the permeability of the rock. One way of well stimulation is matrix acidizing. In matrix acidizing, acid is injected into the rock and reac...
Simulation and prediction of eigenfrequencies and mode shapes for active flexible multibody systems is an important task in disciplines such as robotics and aerospace engineering. A challenge is to accurately include both controller effects and flexible body dynamics in a multidisciplinary system model appropriate for modal analysis. A method for p...
When performing modal analyses of active flexible multibody systems, both controller effects and flexible body dynamics should be included in a multidisciplinary system model. This paper deals with the theory of solving the closed-loop eigenvalue problem for active flexible multibody systems with multiple-input multiple-output proportional-integral...
Screw extrusion of aluminum is a new process for production of aluminum profiles. The commercial potential could be large. Little experimental and numerical work has been done with respect to this process. The material flow of hot aluminum in a screw extruder has been analyzed using finite element formulations for the non-Newtonian Navier-Stokes eq...
In this study we present a new approach to analyse cracked shell structures subjected to large geometric changes. It is based on a combination of a rectangular assumed natural deviatoric strain thin shell finite element and an improved linespring finite element. Plasticity is accounted for using stress resultants. A power law hardening model is use...
This paper presents a unified theoretical framework for the corotational (CR) formulation of finite elements in geometrically nonlinear structural analysis. The key assumptions behind CR are: (i) strains from a corotated configuration are small while (ii) the magnitude of rotations from a base configuration is not restricted. Following a historical...
Many structural applications require nonlinear finite element analyses in order to assess response and capacity. Plastic deformations may be accounted for by means of thickness integration or stress resultants. The stress resultant model employed herein is based on Ilyushins' linear yield criterion for thin shells. The corners present with this cri...
Due to the very non-linear behaviour of thin shells under collapse, numerical simulations are subject to challenges. Shell finite elements are attractive in these simulations. Rotational degrees of freedom do, however, complicate the solution. In the present study a co-rotated formulation is employed. The deformation of the shell is decomposed in t...
This paper starts a sequence of three articles that follow an unconventional approach in finite element research. The ultimate objective is to construct high-performance elements and element-level error estimators for those elements. The approach takes off from our previous work in high-performance elements and culminates with the development of fi...
This article presents a survey of the Core-Congruential Formulation (CCF) for geometrically nonlinear mechanical finite elements
based on the Total Lagrangian (TL) kinematic description. Although the key ideas behind the CCF can be traced back to Rajasekaran
and Murray in 1973, it has not subsequently received serious attention. The CCF is distingu...
This paper is the first of a three-part series that studies the formulation of 3-node, 9-dof membrane elements with normal-to-element-plane rotations (the so-called drilling freedoms) within the context of parametrized variational principles. These principles supply a unified basis for several advanced element-construction techniques; in particular...