Two-scale dynamic optimal design of composite structures in the time domain using equivalent static loads

2016 ◽  
Vol 142 ◽  
pp. 335-345 ◽  
Author(s):  
B. Xu ◽  
X. Huang ◽  
Y.M. Xie
Keyword(s):  
Optimal Design ◽  
Time Domain ◽  
Composite Structures ◽  
Static Loads ◽  
Equivalent Static Loads ◽  
The Time Domain

Dynamic Response Topology Optimization in the Time Domain Using Equivalent Static Loads

AIAA Journal ◽  
2012 ◽  
Vol 50 (1) ◽  
pp. 226-234 ◽  
Author(s):  
H. H. Jang ◽  
H. A. Lee ◽  
J. Y. Lee ◽  
G. J. Park
Keyword(s):  
Topology Optimization ◽  
Dynamic Response ◽  
Time Domain ◽  
Static Loads ◽  
Equivalent Static Loads ◽  
The Time Domain

Fiber-Reinforced Sandwich Plates Under Static Loads—Proposals for Their Optimization

1986 ◽  
Vol 108 (2) ◽  
pp. 152-158 ◽  
Author(s):  
H. A. Eschenauer ◽  
W. Fuchs
Keyword(s):  
Optimal Design ◽  
Composite Structures ◽  
Design Method ◽  
Sandwich Plates ◽  
Structural Members ◽  
Optimization Strategy ◽  
Static Loads ◽  
Conflicting Objectives ◽  
Sequential Linearization ◽  
Optimal Stiffness

In order to satisfy the permanently increasing specification demands on machines and plants, the structural members and units of the constructions have to be designed in an “optimal” way. Nowadays more and more composite structures are attaining such new fields of application where one-component materials are not able to fulfill the higher demands. Typical examples are light constructions with optimal stiffness at various loadings. In this paper, a detailed investigation of the deformation behavior of a simply supported sandwich plate under static loads is carried out. Then, an optimal design method is formulated as a nonlinear multiobjective optimization problem by adopting the two conflicting objectives “minimal deformation” at “minimal weight,” including a set of constraints. The application of an optimization strategy is shown by means of a special preference function and sequential linearization as optimizer. Finally, some results of this procedure are discussed concerning the optimal design of sandwich plates.

Application of Frequency Domain Methods for Response Based Analysis of Flexible Risers

2017 ◽  
Author(s):  
C. Armstrong ◽  
Y. Drobyshevski ◽  
C. Chin
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Composite Structures ◽  
Full Time ◽  
Threshold Limit ◽  
Frequency Domain Methods ◽  
Non Linear ◽  
Flexible Risers ◽  
The Time Domain ◽  
Extreme Responses

Response Based Analysis (RBA) is an advanced method for the prediction of long term distributions of critical responses in offshore floating systems. For complex non-linear systems such as flexible risers, RBA requires time domain simulations that form the core data to which probabilistic models are applied. Because RBA requires significantly larger amounts of data than traditional short term analysis approaches, running the required number of simulations in the time domain can quickly become unfeasible if the system’s physics being modelled are exceedingly complex. In addition, flexible risers are complex composite structures with highly dynamic, non-linear responses which further limit the feasibility of application of the RBA process to these systems. As an alternative, frequency domain solvers, such as that used in the OrcaFlex software, are potential substitutes for portions of datasets due to their processing times being significantly faster than time domain solvers. A comparison of extreme responses generated by frequency and time domain solvers was performed over the duration of two storms. An upper threshold limit for the frequency domain’s accuracy was found by comparing the differences of the two solver’s responses as the storm progressed; where the differences became too large the threshold limit was set. For environmental conditions smaller than this threshold, the frequency domain solver may provide a quicker method for predicting the riser responses. Conditions that exceed this threshold require full time domain analysis for accurate responses to be generated. Limitations of the frequency domain solvers include their reduced ability to deal with non-linear mechanics such as bending/curvature responses. As a result, curvature component results from the frequency domain are limited in their direct usability, especially when exposed to more extreme metocean conditions and locations along the riser that are subject to larger curvature (generally where risers are connected to structures with greater stiffness). Although these limitations exist, the frequency domain solver may still provide reasonable insight into metocean conditions that potentially cause extreme responses. A method is proposed for the use of both frequency and time domain simulations in the flexible riser flowline RBA process. Screening, filtering and ‘stitching’ methods utilizing the speed of the frequency domain solver are presented in order to compensate for the time domain’s extensive computation times. The proposed method of stitching, when applied to an example storm history, required 39% of the processing time when using only the time domain solver.

Apodisation in the time domain

1992 ◽  
Vol 2 (4) ◽  
pp. 615-620
Author(s):  
G. W. Series
Keyword(s):  
Time Domain ◽  
The Time Domain

JOINT INTERPRETATION OF AIRBORNE ELECTROMAGNETIC DATA IN THE TIME DOMAIN AND FREQUENCY DOMAIN

2018 ◽  
Vol 12 (7-8) ◽  
pp. 76-83
Author(s):  
E. V. KARSHAKOV ◽  
J. MOILANEN
Keyword(s):  
Fourier Transform ◽  
Frequency Domain ◽  
Time Domain ◽  
Frequency Interval ◽  
Single Spectrum ◽  
Simultaneous Inversion ◽  
Homogeneous Half Space ◽  
Time Domain Data ◽  
The Time Domain

Тhe advantage of combine processing of frequency domain and time domain data provided by the EQUATOR system is discussed. The heliborne complex has a towed transmitter, and, raised above it on the same cable a towed receiver. The excitation signal contains both pulsed and harmonic components. In fact, there are two independent transmitters operate in the system: one of them is a normal pulsed domain transmitter, with a half-sinusoidal pulse and a small "cut" on the falling edge, and the other one is a classical frequency domain transmitter at several specially selected frequencies. The received signal is first processed to a direct Fourier transform with high Q-factor detection at all significant frequencies. After that, in the spectral region, operations of converting the spectra of two sounding signals to a single spectrum of an ideal transmitter are performed. Than we do an inverse Fourier transform and return to the time domain. The detection of spectral components is done at a frequency band of several Hz, the receiver has the ability to perfectly suppress all sorts of extra-band noise. The detection bandwidth is several dozen times less the frequency interval between the harmonics, it turns out thatto achieve the same measurement quality of ground response without using out-of-band suppression you need several dozen times higher moment of airborne transmitting system. The data obtained from the model of a homogeneous half-space, a two-layered model, and a model of a horizontally layered medium is considered. A time-domain data makes it easier to detect a conductor in a relative insulator at greater depths. The data in the frequency domain gives more detailed information about subsurface. These conclusions are illustrated by the example of processing the survey data of the Republic of Rwanda in 2017. The simultaneous inversion of data in frequency domain and time domain can significantly improve the quality of interpretation.

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