Papers by Edmund Wittbrodt
Ocean engineering & oceanography, 2013
ABSTRACT In numerous technical applications the supporting structure of a device is assumed to be... more ABSTRACT In numerous technical applications the supporting structure of a device is assumed to be subjected to stresses within the limits of proportionality, i.e. where the Hooke’s law is applicable. It is also the case with offshore cranes. In the installation process of underwater pipelines with the reel method, however, the pipes are commonly deformed plastically when they are wound onto the reel. Furthermore, material exposed to prolonged deformation may show a tendency to creep. Hence, the present chapter which briefly introduces these models of construction materials: elasto-plastic and visco-elastic.
WIT Transactions on the Built Environment, Sep 20, 1999
The SN characteristic which is applied in the fatigue investigations-Wohler curve-determines the ... more The SN characteristic which is applied in the fatigue investigations-Wohler curve-determines the number of cycles necessary for the entire destruction of an investigated element as a function of the load amplitude. The estimation of a crack propagation during a fatigue process can be described by the Paris equation and presented in a form of coordinates: the crack growth rate as a function of a stress intensity factor range depending on an exterior load and the exterior geometry of the investigated element, as well as on the geometry of a crack* In this paper the transformation method of the Paris curve into the Wohler curve, in the range of line fracture mechanics, FM, is presented. The obtained FM-SN curves make it possible to compare the fatigue crack propagation results with the SN curves. In the given example, concerning the fatigue crack calculations of the container hatch corners, the FM-SN curves were presented in comparison with the SN standard ones.
ABSTRACT This is a monograph on the foundations of engineering mechanics. Namely, the authors tre... more ABSTRACT This is a monograph on the foundations of engineering mechanics. Namely, the authors treat the dynamics of flexible multibody systems by the rigid finite element method. Flexible multibody systems have been studied by analysts for several decades. Still, there is no agreed upon approach to the subject. The difficulty is that traditional multibody dynamics analysis uses rigid bodies to model physical systems. Although physical systems are not composed of rigid components, the rigid body modelling enables the derivation of exact equations of motion which may be solved numerically. Alternatively, flexible multibody systems provide a more accurate modelling of physical systems, but then the ensuing equations are only approximate. To consistently combine these two methods required ingenuity by the analysts. In this book the authors demonstrate such ingenuity by their detailed presentation of the rigid finite element method where flexible components are modelled by rigid members connected by appropriately chosen springs and dampers. The authors state that this approach has fine principal advantages: (1) it is conceptually simple; (2) it provides a uniform modelling of physical systems; (3) it is numerically efficient; (4) it can be used to study both small and large deformation problems; and (5) it is broadly applicable to many systems of interest and of practical importance. The book itself is divided into seven chapters. Following a brief introductory chapter, the second chapter is a concise review of classical mechanics where the notation is established. In the third and fourth chapters the authors outline the modelling method. Illustrative applications and solution methods are presented in the fifth chapter. Chapter six provides a verification of the method. The authors conclude with a rather extensive chapter on potential real world applications. The reader is assumed to have a knowledge of theoretical and analytical mechanics on the level of mechanical engineering graduate studies. The book is well written and should be of interest and use to students and practitioners in this ever broadening field of computational mechanics.
The aim of the study is elaboration of a method for creating irregular scaffolds that can be used... more The aim of the study is elaboration of a method for creating irregular scaffolds that can be used to model the behaviour of trabecular bone placed in the proximal epiphysis of the femur. The scope of the study encompasses creating six numerical models of irregular scaffolds (two solid irregular scaffolds, two shell irregular scaffolds and two shell irregular scaffolds with fortification) and performing numerical analysis of the proposed numerical models applying a finite element method.
Acta of Bioengineering and Biomechanics, 2003
Two-dimensional motion of a rope fixed at one end is considered. The Rigid Finite Element Method ... more Two-dimensional motion of a rope fixed at one end is considered. The Rigid Finite Element Method (RFEM) is reviewed and applied to obtain a model of the rope, including its elastic and dissipative properties. Equations of motion are derived without the small displacement assumption, using the Lagrange equations. The resulting model is compared to another one, being derived within the framework of standard analytical mechanics methods and the Lagrange formalism. Advantages of the RFE approach are discussed from a computational point of view. The presented, alternative model can be a basis for e cient numerical simulations, which seem to be useful in further, comparative studies of the rope dynamics.
Foundations of Engineering Mechanics
Instytut Wydawniczy EuroPrawo, 2019
Wydawnictwo Politechniki Łódzkiej, 2019
Polska Akademia Nauk, 2019
In the paper, the authors describe and solve the problem of optimum control of selected vibration... more In the paper, the authors describe and solve the problem of optimum control of selected vibration forms in mechanical systems. Two illustrative examples have been used to present the procedure for determination of the optimum controller coefficients. In the first example, a simplified mechanical system is considered, while in the second one – a rotor with magnetic bearing. In both cases, the integral performance indices have been defined in order to minimize the vibration level at selected points of the structures. The system with the magnetic bearing is structurally unstable. For this reason, the authors present the way of finding the weight coefficients of integral performance index for unstable, multi-degrees-of-freedom system. In that way, the selected modal forms attain the previously assumed dynamic properties and the performance index takes the minimum value. The results of numerical analysis show that the proposed way is efficient and makes it possible to control selected fo...
The aim of this paper is to analyze the operating of mechanisms (hoisting gear and crane radius c... more The aim of this paper is to analyze the operating of mechanisms (hoisting gear and crane radius change mechanism) and wave effects influences on the pontoon crane dynamics. Allowances were also made for pontoon rolling, hydrodynamic force reactions and rope system flexibilities. For discretization of the pontoon crane system the rigid finite element method is employed. The equations of motion are derived. Calculations for a typical pontoon crane are carried out and the results obtained are discussed in detail.cranes
Foundations of Engineering Mechanics
The paper discusses the relations between various aspects of human activities performed in space,... more The paper discusses the relations between various aspects of human activities performed in space, taking into consideration the past, present and future contexts. Interdisciplinarity and integrity of technological issues combined with legal and management issues were emphasized. Consequently, it was recognized that it is necessary to build a network of universities, research-and-development companies and engineering companies. A particular attention was dedicated to the current situation in Poland and conditions necessary to achieve a European level.
The purpose of this study is to create a new mathematical model of pennate striated skeletal musc... more The purpose of this study is to create a new mathematical model of pennate striated skeletal muscle. This new model describes behaviour of isolated flat pennate muscle in two dimensions (2D) by taking into account that rheological properties of muscle fibres depend on their planar arrangement. A new mathematical model is implemented in two types: 1) numerical model of unipennate muscle (unipennate model); 2) numerical model of bipennate muscle (bipennate model). Applying similar boundary conditions and similar load, proposed numerical models had been tested. Obtained results were compared with results of numerical researches by applying a Hill-Zajac muscle model (this is a Hill type muscle model, in which the angle of pennation is taken into consideration) and a fusiform muscle model (a muscle is treated as a structure composed of serially linked different mechanical properties parts).
Advances in Mechanism and Machine Science, 2019
Dynamics analysis of a system composed of a parallel manipulator and of an elastic beam is presen... more Dynamics analysis of a system composed of a parallel manipulator and of an elastic beam is presented in the paper. Classic 3RRR parallel manipulator is considered and used to deform the beam. Elasto-plastic deformations are investigated. Rigid-finite-elements technique is employed to deal with dynamics of the beam. A multibody structure is associated with the introduced hybrid system in order to model its dynamics. Idea of the corresponding numerical model is presented. Then numerical tests are performed in order to observe behaviour of the tested system. The tests have validated that the parallel manipulator can be successfully used for plastic deformations of beams in order to form them into the industry required shapes. The tests proved that resistances of the beam deformations are the dominant loads for such application. Influence of the platform dynamics is of the secondary order. Longitudinal slip at the platform’s gripper is significant during such processes and should not be locked.
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Papers by Edmund Wittbrodt