Reduced-Order Modeling of Preloaded Bolted Structures in Multibody Systems by the Use of Trial Vector Derivatives

2017 ◽  
Vol 12 (5) ◽  
Author(s):  
Florian Pichler ◽  
Wolfgang Witteveen ◽  
Peter Fischer
Keyword(s):  
Computational Effort ◽  
Computational Time ◽  
Dynamic Simulations ◽  
Friction Forces ◽  
Trial Vector ◽  
Multibody Dynamic ◽  
New Strategy ◽  
Joint Contact ◽  
Correct Representation ◽  
Bearing Cap

In order to achieve a correct representation of jointed structures within multibody dynamic simulations, an accurate computation of the nonlinear contact and friction forces between the contact surfaces is required. In recent history, trial vectors based on trial vector derivatives, the so-called joint modes, have been presented, which allow an accurate and efficient representation of this joint contact. In this paper, a systematic adaption of this method for preloaded bolted joints is presented. The new strategy leads to a lower number of additional joint modes required for accurate results and hence to lower computational time. Further, a major reduction of the computational effort for joint modes can be achieved. The potential and also possible limitations of the method are investigated using two numerical examples of a preloaded friction bar and a bolted piston rod bearing cap.

scholarly journals Efficient Model Order Reduction for the Dynamics of Nonlinear Multilayer Sheet Structures with Trial Vector Derivatives

2014 ◽  
Vol 2014 ◽  
pp. 1-16 ◽  
Author(s):  
Wolfgang Witteveen ◽  
Florian Pichler
Keyword(s):  
Finite Element ◽  
Model Order Reduction ◽  
Mechanical Response ◽  
Order Reduction ◽  
Contact Forces ◽  
Computational Time ◽  
Present Contribution ◽  
Model Order ◽  
Friction Forces ◽  
Trial Vector

The mechanical response of multilayer sheet structures, such as leaf springs or car bodies, is largely determined by the nonlinear contact and friction forces between the sheets involved. Conventional computational approaches based on classical reduction techniques or the direct finite element approach have an inefficient balance between computational time and accuracy. In the present contribution, the method of trial vector derivatives is applied and extended in order to obtain a-priori trial vectors for the model reduction which are suitable for determining the nonlinearities in the joints of the reduced system. Findings show that the result quality in terms of displacements and contact forces is comparable to the direct finite element method but the computational effort is extremely low due to the model order reduction. Two numerical studies are presented to underline the method’s accuracy and efficiency. In conclusion, this approach is discussed with respect to the existing body of literature.

Dynamical Modeling of Gear Transmission Considering Gearbox Casing

2018 ◽  
Author(s):  
Yang Luo ◽  
Natalie Baddour ◽  
Ming Liang
Keyword(s):  
Dynamic Models ◽  
Signal Propagation ◽  
Gear Transmission ◽  
Gear System ◽  
Dynamical Model ◽  
Contact Friction ◽  
Dynamical Response ◽  
Dynamic Simulations ◽  
Friction Forces ◽  
Frequency Domains

Much research has been carried out to investigate the dynamical response of a gear system because of its importance on vibration feature analysis. It is well known that the gearbox casing is one of the most important components of the gear system and plays an important role in signal propagation. However, its effects have widely been neglected within the dynamic simulations and few dynamic models have considered the gearbox casing when modeling a gear transmission. This paper proposes a gear transmission dynamical model with the consideration of the effects of gearbox casing. The proposed dynamical model incorporates TVMS, a time-varying load sharing ratio, as well as dynamic tooth contact friction forces, friction moments and dynamic mesh damping coefficients. The proposed gear dynamical model is validated by comparison with responses obtained from experimental test rigs under different speed conditions. Comparisons indicate that the responses of the proposed dynamical model are consistent with experimental results, in both time and frequency domains under different rotation speeds.

Integrated Redesign of Large-Scale Structures by Large Admissible Perturbations

2003 ◽  
Vol 125 (4) ◽  
pp. 234-241 ◽  
Author(s):  
Vincent Y. Blouin ◽  
Michael M. Bernitsas ◽  
Denby Morrison
Keyword(s):  
Degrees Of Freedom ◽  
Large Scale ◽  
Direct Method ◽  
Computational Effort ◽  
Forced Response ◽  
Response Amplitude ◽  
Computational Time ◽  
Performance Constraints ◽  
Large Admissible Perturbations ◽  
Design Selection

In structural redesign (inverse design), selection of the number and type of performance constraints is a major challenge. This issue is directly related to the computational effort and, most importantly, to the success of the optimization solver in finding a solution. These issues are the focus of this paper, which provides and discusses techniques that can help designers formulate a well-posed integrated complex redesign problem. LargE Admissible Perturbations (LEAP) is a general methodology, which solves redesign problems of complex structures with, among others, free vibration, static deformation, and forced response amplitude constraints. The existing algorithm, referred to as the Incremental Method is improved in this paper for problems with static and forced response amplitude constraints. This new algorithm, referred to as the Direct Method, offers comparable level of accuracy for less computational time and provides robustness in solving large-scale redesign problems in the presence of damping, nonstructural mass, and fluid-structure interaction effects. Common redesign problems include several natural frequency constraints and forced response amplitude constraints at various frequencies of excitation. Several locations on the structure and degrees of freedom can be constrained simultaneously. The designer must exercise judgment and physical intuition to limit the number of constraints and consequently the computational time. Strategies and guidelines are discussed. Such techniques are presented and applied to a 2,694 degree of freedom offshore tower.

Accurate and efficient representation of intramolecular energy in ab initio generation of crystal structures. II. Smoothed intramolecular potentials

2019 ◽  
Vol 75 (3) ◽  
pp. 423-433 ◽  
Author(s):  
Isaac J. Sugden ◽  
Claire S. Adjiman ◽  
Constantinos C. Pantelides
Keyword(s):  
Structure Prediction ◽  
Weighted Average ◽  
Lattice Energy ◽  
Comparative Investigation ◽  
Computational Effort ◽  
Flufenamic Acid ◽  
Computational Time ◽  
Crystal Structure Prediction ◽  
Efficient Representation ◽  
First Time

The application of crystal structure prediction (CSP) to industrially relevant molecules requires the handling of increasingly large and flexible compounds. A revised model for the effect of molecular flexibility on the lattice energy that removes the discontinuities and non-differentiabilities present in earlier models (Sugden et al., 2016), with a view to improving the performance of CSP is presented. The approach is based on the concept of computing a weighted average of local models, and has been implemented within the CrystalPredictor code. Through the comparative investigation of several compounds studied in earlier literature, it is shown that this new model results in large reductions in computational effort (of up to 65%) and in significant increases in reliability. The approach is further applied to investigate, for the first time, the computational polymorphic landscape of flufenamic acid for Z′ = 1 structures, resulting in the successful identification of all three experimentally resolved polymorphs within reasonable computational time.

Treating Uncertainties in Multibody Dynamic Systems Using a Polynomial Chaos Spectral Decomposition

2004 ◽  
Author(s):  
Corina Sandu ◽  
Adrian Sandu ◽  
Brendan J. Chan ◽  
Mehdi Ahmadian
Keyword(s):  
Frequency Domain ◽  
Dynamic Systems ◽  
Time Domain ◽  
Spectral Decomposition ◽  
Polynomial Chaos ◽  
Model Uncertainties ◽  
Dynamic Simulations ◽  
Computational Tools ◽  
Model Complex ◽  
Multibody Dynamic

This study addresses the critical need for computational tools to model complex nonlinear multibody dynamic systems in the presence of parametric and external uncertainty. Polynomial chaos has been used extensively to model uncertainties in structural mechanics and in fluids, but to our knowledge they have yet to be applied to multibody dynamic simulations. We show that the method can be applied to quantify uncertainties in time domain and frequency domain.

Surrogate articular contact models for computationally efficient multibody dynamic simulations

2010 ◽  
Vol 32 (6) ◽  
pp. 584-594 ◽  
Author(s):  
Yi-Chung Lin ◽  
Raphael T. Haftka ◽  
Nestor V. Queipo ◽  
Benjamin J. Fregly
Keyword(s):  
Computationally Efficient ◽  
Dynamic Simulations ◽  
Multibody Dynamic ◽  
Contact Models

A comparison of numerical methods for optimizing even aged stand management

1990 ◽  
Vol 20 (7) ◽  
pp. 961-969 ◽  
Author(s):  
Lauri T. Valsta
Keyword(s):  
Dynamic Programming ◽  
Species Composition ◽  
Random Search ◽  
Optimization Methods ◽  
Global Optimum ◽  
Computational Effort ◽  
Direct Search ◽  
Computational Time ◽  
Discrete State ◽  
Stand Management

A two-species, whole-stand, deterministic growth model was combined with three optimization methods to derive management regimes for species composition, thinnings, and rotation age, with the objective of maximizing soil expectation value. The methods compared were discrete time – discrete state dynamic programming, direct search using the Hooke and Jeeves algorithm, and random search. Optimum solutions for each of the methods varied considerably, required unequal amounts of computational time, and were not equally stable. Dynamic programming located global optimal solutions but did not determine them accurately, owing to discretized state space. Direct search yielded the largest objective function values with comparable computational effort, although the likelihood of finding a global optimum solution was high only for smaller problems with up to two or three thinnings during the rotation. Random search solutions varied considerably with regard to growing stock level and species composition and did not define a consistent management guideline. In general, direct search and dynamic programming appeared to be superior to random search.

Load Effects on the Dynamics of Spur Gear Transmissions

2010 ◽  
Author(s):  
Alfonso Fernandez del Rincon ◽  
Fernando Viadero Rueda ◽  
Miguel Iglesias Santamaria ◽  
Pablo Garcia Fernandez ◽  
Ana de-Juan de Luna ◽  
...  
Keyword(s):  
Gear Tooth ◽  
Hybrid Approach ◽  
Angular Position ◽  
Spur Gear ◽  
Computational Effort ◽  
Contact Forces ◽  
Mode Shapes ◽  
Computational Time ◽  
Applied Torque ◽  
Rolling Elements

Gear transmissions in general and spur gears in particular exhibit a different dynamic behavior depending on the level of the transmitted load. This fact justifies the interest in the study of the role of the load in gear dynamics not only in the context of design, vibration and noise control but also for condition monitoring. This task requires the development of advanced models achieving a compromise between accuracy and computation time. In this work, gear and bearing non-linearities associated with the contact among teeth and roller elements have been included, taking into account the flexibility of gears, shafts and bearings. Besides, parametric excitations coming both from gear and bearing supports, as well as clearance, were also considered. Gear contact force calculations are carried out following a hybrid approach which combines both analytical and numerical tools. This lets to achieve accurate results with an acceptable computational effort and thus dynamic analysis becomes feasible. This approach was improved and the calculation speeded up from the point of view of computational time. This was performed by using a pre-calculated value for gear tooth stiffness as a function of load and the angular position when it operates under stationary conditions. On the other hand, bearings were formulated just as deflections of Hertzian type. This means that bending and shearing of races and rolling elements are neglected. However, the variation in the number of loaded rolling elements as a function of the load and the angular position was taken into account. Shaft flexibilities were added to gear and bearing models to define a simple transmission that was used to study the vibratory behavior under different levels of applied torque. In a preliminary study, this model was linearized for several loads, obtaining the corresponding frequencies and mode-shapes in order to assess their variation with this parameter. Finally, dynamic simulations were carried out, showing the modifications undergone by the orbits, meshing contact forces and transmitted bearing forces.

VERIFICATION OF A MARINE POLLUTANT SURFACE PLUME MODEL FOR USE IN THE DEVELOPMENT OF AUTONOMOUS VEHICLE TRACKING SYSTEMS

2017 ◽  
Vol 2017 (1) ◽  
pp. 1612-1628
Author(s):  
Laura M. Fitzpatrick ◽  
A Zachary Trimble ◽  
Brian S. Bingham
Keyword(s):  
Control Systems ◽  
Surface Concentration ◽  
Computational Effort ◽  
Computational Time ◽  
Type Model ◽  
Fine Scale ◽  
Multiple Model ◽  
Robotic Control ◽  
Statistical Parameters ◽  
Tuning Parameters

ABSTRACT A marine pollutant spill environmental model that can accurately predict fine scale pollutant concentration variations on a free surface is needed in early stages of testing robotic control systems for tracking pollutant spills. The model must reproduce, for use in a robotic control system simulation environment, the fine-scale surface concentration variations observed by a robot. Furthermore, to facilitate development of robotic control systems, the model must reproduce sample spill distributions in minimal computational time. A combination Eulerian-Lagrangian type model, with two tuning parameters, was developed to produce, with minimal computational effort, the fine scale concentrations that would be observed by a robot. Multiple model scenarios were run with different tuning parameters to determine the effects of those parameters on the model’s ability to reproduce an experimental measured pollutant plume’s structure. A qualitative method for analyzing the concentration variations was established using amplitude and temporal statistical parameters. The differences in the statistical parameters between the model and experiment vary from 69%–316%. After tuning, the model produces a sample spill, which includes a high frequency concentration component not observed in the experimental data, but that generally represents the real-time, fine scale pollutant plume structure and can be used for testing control algorithms.

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