scholarly journals Detailed wheel/rail geometry processing with the conformal contact approach

2020 ◽  
Author(s):  
Edwin Vollebregt
Keyword(s):  
Multibody Systems ◽  
Tangent Plane ◽  
Shear Stresses ◽  
Coordinate Transformations ◽  
Geometry Processing ◽  
Force Element ◽  
Systems Simulation ◽  
Planar Contact ◽  
Conformal Contact ◽  
Selection Of

Abstract 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 contact situations. This by-passes the selection of the contact reference location and reference angle, which are delicate aspects of planar contact approaches. The idea is worked out introducing the curved reference surface as the new backbone for the computations, instead of the tangent plane used previously in planar contact approaches. The steps are described by which the curved reference is constructed in CONTACT, using generic facilities for markers, grids, and coordinate transformations, by which generic wheel/rail configurations can be analyzed in a fully automated way. Numerical results show the capabilities of the new method for measured, worn profiles, suppressing discontinuities in the forces when multiple contact patches split or merge. A further application concerns the evaluation of strategies used in planar contact approaches. There we find that the tangent plane’s inclination is of the biggest importance. This should be defined in an averaged way to achieve maximum correspondence to the more detailed curved contact approach.

scholarly journals Projected explicit and implicit Taylor series methods for DAEs

2021 ◽  
Author(s):  
Diana Estévez Schwarz ◽  
René Lamour
Keyword(s):  
Taylor Series ◽  
Multibody Systems ◽  
Optimization Problem ◽  
Automatic Differentiation ◽  
Taylor Coefficients ◽  
Integration Schemes ◽  
Consistent Initial Values ◽  
Taylor Series Methods ◽  
Systems Simulation ◽  
Derivative Array

AbstractThe recently developed new algorithm for computing consistent initial values and Taylor coefficients for DAEs using projector-based constrained optimization opens new possibilities to apply Taylor series integration methods. In this paper, we show how corresponding projected explicit and implicit Taylor series methods can be adapted to DAEs of arbitrary index. Owing to our formulation as a projected optimization problem constrained by the derivative array, no explicit description of the inherent dynamics is necessary, and various Taylor integration schemes can be defined in a general framework. In particular, we address higher-order Padé methods that stand out due to their stability. We further discuss several aspects of our prototype implemented in Python using Automatic Differentiation. The methods have been successfully tested on examples arising from multibody systems simulation and a higher-index DAE benchmark arising from servo-constraint problems.

Sedimentation in Storage Tank Structures

1994 ◽  
Vol 29 (1-2) ◽  
pp. 363-372 ◽  
Author(s):  
Virginia R. Stovin ◽  
Adrian J. Saul
Keyword(s):  
Numerical Models ◽  
Effective Means ◽  
Design Guidelines ◽  
Laboratory Model ◽  
Shear Stresses ◽  
Model Situation ◽  
Combined Sewer ◽  
Urban Watercourse ◽  
Storage Structures ◽  
Selection Of

Although storage tanks provide an effective means of reducing the magnitude and frequency of combined sewer overflow discharges, and thereby of alleviating urban watercourse pollution, poorly designed storage structures frequently suffer from maintenance problems arising from sedimentation. The development of design guidelines that optimise the self-cleansing operation of storage structures is clearly a priority for urban drainage research. This paper describes a system that has been developed to study sediment deposition in laboratory model-scale storage structures. The patterns of deposition resulting from a selection of flow regimes are described, and the need for time-varying and time series storm tests is highlighted. Sedimentation patterns are shown to predominantly depend on the flow field, and the critical bed shear stresses for deposition and erosion in the model situation are identified. Hence, the potential application of numerical models to the design problem is discussed.

Utilizing Modeling in a Reliability Study of ACA Joints in Humidity Tests

2013 ◽  
Vol 10 (1) ◽  
pp. 30-39 ◽  
Author(s):  
Kirsi Saarinen ◽  
Laura Frisk
Keyword(s):  
Radio Frequency Identification ◽  
Cost Savings ◽  
Experimental Tests ◽  
Shear Stresses ◽  
Cycling Test ◽  
Humidity Level ◽  
Anisotropic Conductive Adhesive ◽  
Frequency Identification ◽  
Identification Tags ◽  
Selection Of

Radio frequency identification tags (RFID) with anisotropic conductive adhesive (ACA) joints are used in various applications where the environmental conditions may impair their reliability. Thus the effects of different environmental stresses on reliability need to be investigated. The purpose of this work was to study whether a relatively simple shear stress model can be utilized in reliability prediction of anisotropically conductive paste (ACP) joints in an accelerated humidity test on the basis of the information obtained from another humidity test. If modeling gives accurate results when studying reliability, the need for actual testing would decrease and thereby time and cost savings could be achieved. In this study, finite element models were made to calculate shear stresses in ACP joints induced by two different humidity tests. Additionally, experimental tests were performed and the results were compared with those of modeling. The test samples were RFID tags whose microchips were attached with ACP. A constant humidity test was used to study the effects of high humidity level and a humidity cycling test was used to examine the effects of constantly varying humidity. In the modeling it was observed that the selection of the stress-free temperature has a significant effect on the results. With three different stress-free temperatures, three different sets of results were obtained. Although the tags saturated in the extreme conditions of the humidity cycling test, according to modeling, the change in relative humidity level in the humidity cycling test did not increase the harshness of the test. However, the temperature change in the humidity cycling test increased the harshness.

Mathematical modelling of shallow flows: Closure models drawn from grain-scale mechanics of sediment transport and flow hydrodynamicsThis paper is one of a selection of papers in this Special Issue in honour of Professor M. Selim Yalin (1925–2007).

2009 ◽  
Vol 36 (10) ◽  
pp. 1605-1621 ◽  
Author(s):  
Rui M. L. Ferreira ◽  
Mário J. Franca ◽  
João G. A. B. Leal ◽  
António H. Cardoso
Keyword(s):  
Sediment Transport ◽  
Mathematical Modelling ◽  
Conceptual Models ◽  
Numerical Solutions ◽  
Shear Stresses ◽  
Shallow Flows ◽  
River Modelling ◽  
Morphologic Evolution ◽  
Sediment Mixtures ◽  
Selection Of

Mathematical modelling of river processes is, nowadays, a key element in river engineering and planning. River modelling tools should rest on conceptual models drawn from mechanics of sediment transport, river mechanics, and river hydrodynamics. The objectives of the present work are (i) to describe conceptual models of sediment transport, deduced from grain-scale mechanics of sediment transport and turbulent flow hydrodynamics, and (ii) to present solutions to specific river morphology problems. The conceptual models described are applicable to the morphologic evolution of rivers subjected to the transport of poorly sorted sediment mixtures at low shear stresses and to geomorphic flows featuring intense sediment transport at high shear stresses. In common, these applications share the fact that sediment transport and flow resistance depend, essentially, on grain-scale phenomena. The idealized flow structures are presented and discussed. Numerical solutions for equilibrium and nonequilibrium sediment transport are presented and compared with laboratory and field data.

MODELING OF PUMP OPERATION CONDITIONS IN GRAVITY-PRESSURE COMBINED SYSTEMS

2017 ◽  
Vol 168 (48) ◽  
pp. 35-44
Author(s):  
Ireneusz Nowogoński ◽  
Ewa Ogiołda ◽  
Marlena Kubiszyn
Keyword(s):  
Working Conditions ◽  
Dynamical Analysis ◽  
Active Volume ◽  
Pump Operation ◽  
Operation Conditions ◽  
Pump Station ◽  
Pumping Stations ◽  
Pump Stations ◽  
Systems Simulation ◽  
Selection Of

The paper presents the problem of working conditions in gravitationalpressure systems simulation. The practical example takes into account the dynamical analysis of a system equipped with 10 pump stations with different functions. Both local press stations, local stations for shallowing network and transit pumping stations between the towns were used. The model allowed to optimize the active volume of the pump station tanks, the selection of pumps, including the frequency of power on and the time of holding the sewage.

On the Development of a 3D Printer for Combinatorial Structural Composite Research

2015 ◽  
Author(s):  
Seyed Allameh
Keyword(s):  
Mechanical Properties ◽  
3D Printing ◽  
Partial Slip ◽  
Shear Stresses ◽  
3D Printer ◽  
Dynamic Shear ◽  
Structural Composites ◽  
Structural Composite ◽  
The Right ◽  
Selection Of

Bioinspired materials have enabled the fabrication of tough lightweight structures for load- and impact-bearing applications of which an example is fiber-reinforced plastics use in aerospace. If applied to the field of construction, biomimicked composites can save lives, otherwise lost to earthquakes and other disasters that cause collapse of buildings. The main culprit is the low resistance of structures exposed to dynamic shear stresses, typical of earthquakes. Recent work on the application of biomimicry to structural composites has clearly shown the advantage of these materials in resisting dynamic shear. Adding natural or synthetic reinforcement fibers may alleviate the need for conventional steel rebars and make it possible to print buildings by conventional 3D printing technology. The main hurdles are to find the right type of composite that is compatible with 3D printing and the right process for deposition of such material. In the past, combination of carbon fiber, glue and concrete has been demonstrated to enhance the toughness of resulting structural composites. Inspired by the microstructure of oyster and mother of pearl, layering of these materials mitigates the localization of deformation by distributing the imposed displacement over a large area. The intricate structure of these layers, and the minute details of the interfaces are important for affecting good dynamic shear resistance. In nacre, a partial slip of sandwiched layers occurs before it stops and deformation is transferred to the adjacent area. This energy-absorption capability underlies the high-toughness behavior of nacre and similar structures. By mimicking nacre, bone and tooth, it is possible to benefit from their good properties, however, it is important to determine the type of material, layering scheme, geometry, and other factors that affect mechanical properties. A recently-developed medium-sized 3D printer was developed to deposit structural materials. These include cement, plaster, polymer and clay. Combinatorial structural composite research (CSCR) comprising the simultaneous fabrication and characterization of multiple specimens with different microstructures allows fair comparison of mechanical properties of various structural composites. Novel application of deposition techniques to the extrusion of plaster, cement and clay paves the way to layer these materials along with glue and fibers in desired schemes. Use of ANOVA tables in the selection of various types of ceramics, polymers and reinforcement materials for the fabrication of different composites will be discussed. In addition to selection of the type of the materials, deposition schemes such as those of solid and hollow structures, different layer thickness applications, and the effect of timing will be elucidated. Microscopy conducted on the fractured surfaces enables the investigation of the mechanisms of fracture and failure for these CSCR composites. The details of experiments conducted, microscopy performed and the results of mechanical tests will be presented.

Analysis of an Embedded Sensor in a Composite Laminate for Enabling Damage Detection

2003 ◽  
Author(s):  
Scott Sealing ◽  
Charles Seeley ◽  
Haleh Ardebili
Keyword(s):  
Transfer Function ◽  
Composite Laminate ◽  
Transfer Functions ◽  
Coefficient Of Thermal Expansion ◽  
Fiber Composite ◽  
Shear Stresses ◽  
Material Interfaces ◽  
Face Centered ◽  
Global And Local ◽  
Selection Of

A study of the influence of embedding sensors to detect damage within a composite laminate is conducted. A variety of sensors are considered along with several encapsulation materials. Encapsulation is required to aid in interfacial adhesion and to provide an electrical isolation from the graphite fiber composite laminate. This study is conducted to down-select the options for the sensor and encapsulant. A parametric global and local finite element models are developed to perform multiple runs corresponding to a design of experiments (DOE). The parameters that are varied are the sensor thickness, sensor length, encapsulant thickness, sensor modulus and coefficient of thermal expansion (CTE), and encapsulant modulus and CTE. Each parameter is varied based on the initial selection of sensors and encapsulants and considered at three levels for a quadratic transfer function. The DOE selected is a face centered CCD resulting in a total of 143 runs. The required output from each run is the effective axial and bending stiffness and the normal and shear stresses at the material interfaces. For each of these outputs from all of the runs, a transfer function is developed to identify the major contributors to the results. The resulting transfer functions indicate that the influence of the sensor and encapsulant parameters do not significantly affect the effective composites stiffness. However, they do contribute significantly to the material interfacial stresses, with the modulus of the sensor and encapsulant contributing the most to the variation of these stresses.

A Technique for Planar Contact Recognition in Automatic Assembly Planning

1996 ◽  
Author(s):  
Sa’id Golabi ◽  
Kazem Abhary ◽  
Lee H. S. Luong
Keyword(s):  
Assembly Planning ◽  
Solid Model ◽  
Automatic Assembly ◽  
Model Data ◽  
New Approaches ◽  
Assembly Sequences ◽  
Geometrical Data ◽  
Solid Part ◽  
Planar Contact ◽  
Selection Of

Abstract Recognition of all assembly sequences and selection of the most efficient one have been the main concerns of researchers in assembly planning during the last decade. Few of these researchers attempted to automatically generate assembly sequences using the geometric and solid model data of the product. To solve the problem of contact recognition a broad research was conducted to recognise contact between planar, cylindrical and conical faces during this research. This paper explains one of the techniques developed herein to recognise contact between two planar faces. The necessary geometrical data of a solid model has been extracted from AutoCAD. The method includes new approaches for detecting a point within the solid part of a face, and investigating the intersection of two curved edges.

scholarly journals Frictionless multiple impacts in multibody systems. I. Theoretical framework

2008 ◽  
Vol 464 (2100) ◽  
pp. 3193-3211 ◽  
Author(s):  
Caishan Liu ◽  
Zhen Zhao ◽  
Bernard Brogliato
Keyword(s):  
Multibody Systems ◽  
Contact Stiffness ◽  
Contact Point ◽  
Multiple Impacts ◽  
Contact Points ◽  
Post Impact ◽  
Relative Potential ◽  
Impact Problems ◽  
Selection Of ◽  
Theoretical Developments

A new method is proposed that can deal with multi-impact problems and produce energetically consistent and unique post-impact velocities. A distributing law related to the energy dispersion is discovered by mapping the time scale into the impulsive scale for bodies composed of rate-independent materials. It indicates that the evolution of the kinetic energy during the impacts is closely associated with the relative contact stiffness and the relative potential energy stored at the contact points. This distributing law is combined with the Darboux–Keller method of taking the normal impulse as an independent ‘time-like’ variable, which obeys a guideline for the selection of an independent normal impulse. Local energy losses are modelled with energetic coefficients of restitution at each contact point. Theoretical developments are presented in the first part in this paper. The second part is dedicated to numerical simulations where numerous and accurate results prove the validity of the approach.

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