Time domain and frequency domain analysis of functionally graded piezoelectric harvesters subjected to random vibration: Finite element modeling

2016 ◽  
Vol 136 ◽  
pp. 384-393 ◽  
Author(s):  
Y. Amini ◽  
P. Fatehi ◽  
M. Heshmati ◽  
H. Parandvar
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
Frequency Domain ◽  
Time Domain ◽  
Random Vibration ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Functionally Graded ◽  
Element Modeling ◽  
Functionally Graded Piezoelectric

Finite-Element Modeling and Frequency-Domain Analysis of Liquid-Propulsion Launch Vehicle

AIAA Journal ◽  
2015 ◽  
Vol 53 (11) ◽  
pp. 3297-3304 ◽  
Author(s):  
Yu Hao ◽  
Guo-an Tang ◽  
Deyuan Xu ◽  
Qiongliang Yang
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
Frequency Domain ◽  
Domain Analysis ◽  
Launch Vehicle ◽  
Frequency Domain Analysis ◽  
Element Modeling

Random Vibration Fatigue: Frequency Domain Critical Plane Approaches

2013 ◽  
Author(s):  
Giovanni de Morais Teixeira ◽  
Radwan Hazime ◽  
John Draper ◽  
Dewi Jones
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Input Signal ◽  
Random Vibration ◽  
Equivalent Stress ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
System Response ◽  
Valuable Insight ◽  
Critical Plane

Frequency domain analysis offers a very efficient method for the fatigue durability assessment of structures subjected to vibration loading. It also allows engineers to gain valuable insight into system behavior and characteristics that are not easily recognized in the time domain. With some reasonable assumptions, most importantly linearity and steady state behavior, the response of a structure in many engineering applications can be simply evaluated through the “scaling” of the input signal by the Frequency Response Functions (FRFs). In cases where the input is random or stochastic in nature additional assumptions are needed to assess the behavior of the system. Usually such cases assume a stationary and ergodic input signal with a zero mean Gaussian distribution. When making such assumptions the system is still characterized by its FRFs. However, since the input signal is random it can be best described by its Power Spectral Density (PSD). Furthermore, the system response (characterized by the stress tensor) can be evaluated by “scaling” the PSD of the input signal(s) by the magnitude squared of the stress FRFs. The linearity assumption also allows the evaluation of a system response due to multiple inputs through superposition principles. When using stress based fatigue (to assess the durability of a component or a structure) there are several damage evaluation methodologies that can be used. Traditionally, for time domain analysis the von Mises equivalent stress had been the methodology of choice. More recently critical plane search methods have gained popularity and have shown much better correlation with laboratory experiments and field failures, especially under multi-axial and non-proportional loading. Some of these methods have found their way into frequency domain analysis. This paper highlights the application of critical plane methods for the multi-axial fatigue assessment of engineering structures that are subjected to non-deterministic random vibration. A case study is presented to illustrate the process and shows how the proposed method works.

scholarly journals Analysis of Three-Phase Wye-Delta Connected LLC

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3606
Author(s):  
Jing-Yuan Lin ◽  
Chuan-Ting Chen ◽  
Kuan-Hung Chen ◽  
Yi-Feng Lin
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Operation Time ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Complete Analysis ◽  
Plane Analysis ◽  
Analysis Methods ◽  
Three Phase

Three-phase wye–delta LLC topology is suitable for voltage step down and high output current, and has been used in the industry for some time, e.g., for server power and EV charger. However, no comprehensive circuit analysis has been performed for three-phase wye–delta LLC. This paper provides complete analysis methods for three-phase wye–delta LLC. The analysis methods include circuit operation, time domain analysis, frequency domain analysis, and state–plane analysis. Circuit operation helps determine the circuit composition and operation sequence. Time domain analysis helps understand the detail operation, equivalent circuit model, and circuit equation. Frequency domain analysis helps obtain the curve of the transfer function and assists in circuit design. State–plane analysis is used for optimal trajectory control (OTC). These analyses not only can calculate the voltage/current stress, but can also help design three-phase wye-delta connected LLC and provide the OTC control reference. In addition, this paper uses PSIM simulation to verify the correctness of analysis. At the end, a 5-kW three-phase wye–delta LLC prototype is realized. The specification of the prototype is a DC input voltage of 380 V and output voltage/current of 48 V/105 A. The peak efficiency is 96.57%.

scholarly journals Optimal implementation of frequency domain impedances in time domain simulations of building structures on embedded foundations

2020 ◽  
Author(s):  
Danilo S. Kusanovic ◽  
Elnaz E. Seylabi ◽  
Domniki Asimaki
Keyword(s):  
Finite Element ◽  
Frequency Domain ◽  
Time Domain ◽  
Response Spectrum ◽  
Free Field ◽  
Domain Analysis ◽  
Shallow Foundation ◽  
Rigid Base ◽  
Dimensionless Frequency ◽  
Building Structures

Soil-Structure Interaction (SSI) have been studied the last decades, and proper analysis for the linear elastic case in frequency domain has been established successfully. However, SSI is rarely considered in the seismic design of building structures. Regardless of its importance as a significant source of flexibility and energy dissipation, buildings are analyzed using a rigid base assumption, and the design is based on a response spectrum analysis, for which not only the soil, but also time are totally ignored. In a first attempt to improve and to incentivize time domain analyzes compatible with standard finite element packages for the engineering community, the state-of-practice introduces two major simplifications to transform the frequency domain analysis into a time domain analysis: (a) it assumes the frequency at which the impedance value should be read is the flexible-base frequency, and (b) it also assumes that the foundation input motion preserves the phase of the free field motion. Upon these simplifications, the following questions may arise: How does NIST recommendations perform in overall against a full finite element model? Are the embedment effects for shallow foundation not important so that the phase angle can be neglected? What is the best dimensionless frequency to estimate the soil impedance? Is it possible to make a better estimation of the dimensionless frequency to increase the NIST accuracy? In this study, we attempt to address these questions by using an inverse problem formulation.

Sign in / Sign up

Export Citation Format

Share Document