Prediction of the Vibration Levels Generated by Pyrotechnic Shocks Using an Approach by Equivalent Mechanical Shock

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
David Wattiaux ◽  
Olivier Verlinden ◽  
Calogero Conti ◽  
Christophe De Fruytier
Keyword(s):  
Dynamic Behavior ◽  
Response Spectrum ◽  
Electronic Equipment ◽  
The Other ◽  
Test Facility ◽  
Computational Techniques ◽  
Mechanical Shock ◽  
Fem Model ◽  
Test Specifications ◽  
Electromagnetic Relays

This paper is concerned with the numerical simulation of mechanical structures subjected to pyroshocks. In practice, the methodology is applied on the pyroshock test facility, which is used by Thales to qualify the electronic equipment intended to be embarked onboard of spatial vehicles. This test facility involves one plate or two plates linked by screw bolts. The tested device is mounted on one side while the explosive charge is applied on the other side. The main issue of this work is to be able to tune, by simulation, the parameters of the facility (number of plates, material of plate, number of bolts, amount of explosive, etc.) so as to get the required level of solicitation during the test. The paper begins by an introduction presenting the state of the art in terms of pyroshock modeling, followed by a description of the shock response spectrum (SRS) commonly used to represent the test specifications of an embarked equipment. It turns out that there is a lack of computational techniques able to predict the dynamic behavior of complex structures subjected to high frequency shock waves such as explosive loads. Three sections are then devoted to the simulation of the pyrotechnic test, which involves on one hand a model of the structure and on the other hand an appropriate representation of the impulsive load. The finite element method (FEM) is used to model the dynamic behavior of the structure. The FEM models of several instances of the facility have been updated and validated up to 1000Hz by comparison with the results of experimental modal analyses. For the excitation source, we have considered an approach by equivalent mechanical shock (EMS), which consists in replacing the actual excitation by a localized force applied on the FEM model at the center of the explosive device. The main originality of the approach is to identify the amplitude and duration of the EMS by minimizing the gap between the experimental and numerical results in terms of the SRS related to several points of the facility. The identification has been performed on a simple plate structure for different amounts of explosive. The methodology is then validated in three ways. Firstly, it is shown that there is a good agreement between experimental and numerical SRS for all the points considered to identify the EMS. Secondly, it appears that the energy injected by the EMS is well correlated with the amount of explosive. Lastly, the EMS identified on one structure for a given amount of explosive leads to coherent responses when applied on other structures. A parametric study is finally performed, which shows the influence of the thickness of the plate, the material properties, the localization of the EMS, and the addition of a local mass. The different obtained results show that our pyroshock model allows to efficiently estimate the acceleration levels undergone by the electronic equipment during a pyroshock and, in this way, to predict some eventual electrical failures, such as the chatter of electromagnetic relays.

Prediction of the Dynamic Behaviour of Electromagnetic Relays Submitted to Mechanical Shocks

2006 ◽  
Author(s):  
D. Wattiaux ◽  
C. Conti ◽  
O. Verlinden
Keyword(s):  
Shock Waves ◽  
Dynamic Behaviour ◽  
Response Spectrum ◽  
Response Spectra ◽  
Electronic Equipment ◽  
Computational Techniques ◽  
Experimental Frequency ◽  
Mechanical Shocks ◽  
Shock Response ◽  
Electromagnetic Relays

During space flights, pyrotechnic devices are widely used to separate structural subsystems, to unfold solar panels or to activate propellant valves. The firing of these pyrotechnic devices generates severe shock waves (so-called pyroshocks) with high intensity and wide frequency range, which can damage the surrounding electronic equipment. Common observed damages more especially concern relay chatter and transfer, as well as failure of magnetic components. There is a lack of failure criteria for electronic equipment as well as computational techniques able to predict the dynamic behaviour of complex structures subjected to high frequency shock waves. The pyrotechnic shock behaviour is checked experimentally: test specifications imposed through embarked electronic devices are generally defined as a maximum limit imposed to the Shock Response Spectrum (SRS). This paper describes a methodology to check the electrical and mechanical behaviours of some electromagnetic relays submitted to severe mechanical shocks. Experimental results obtained when checking the perturbations induced by shocks on the electrical behaviour of some relays, such as the latching GP250 relay are also presented. Microswitches levels have been correlated with the magnitude and shape of different Shock Response Spectra. This paper presents also a simplified model of electromagnetic relays allowing to predict the electrical dysfunctions such as the micro-openings. The model has been updated using experimental frequency and modal analysis.

scholarly journals How Do We Evaluate the Good Test of Arabic in High School in Indonesia?/كيف نواصف الاختبار الجيد لمادة اللغة العربية في المدرسة الثانوية بإندونيسيا؟

2018 ◽  
Vol 2 (1) ◽  
pp. 78-94
Author(s):  
Eva Lathifah
Keyword(s):  
Secondary School ◽  
The Other ◽  
Final Exam ◽  
Good Test ◽  
Islamic Schools ◽  
Teaching Objectives ◽  
Test Specifications ◽  
Measurement And Evaluation ◽  
Academic Year

The teaching process consists of four pillars: the teaching objectives, the needs and preparations of the students, the input of behavioral inputs, experiences or educational activities, and the measurement and evaluation. These four pillars are interconnected to each other organically so that one cant be dispensed with the other. Therefore, this research aims to know the calendar in general. The research also deals with the knowledge of the good test specifications in the Islamic schools, especially the secondary school, and the quality of the exam in the final exam in the academic year 2015/2016.إن العملية التدريسية تتكون من أربعة أركان وهي الأهداف التدريسية وحاجات واستعدادات التلاميذ المساة بالمدخلات السلوكية والخبرات أو الأنشطة التعليمية ثم  القياس والتقويم. وترتبط هذه الأركان الأربع بعضها ببعض ارتباطا عضويا بحيث لا يستغنى أحدها عن الأخر. لذا، يهدف هذا البحث إلى معرفة التقويم بوجه عام، كما يتطرق البحث إلى معرفة مواصفات الاختبار الجيد في المدارس الإسلامية بخاصة المدرسة الثانوية ومعرفة جودة الاختبار في الامتحان النهائى المقنن فيها للعام الدراسي 2015/2016 مـ.

scholarly journals Effects of Eccentricity on the Dynamic Behavior for Electromechanical Integrated Toroidal Drive

2013 ◽  
Vol 20 (2) ◽  
pp. 273-286 ◽  
Author(s):  
Lizhong Xu ◽  
Haifeng Li
Keyword(s):  
Dynamic Behavior ◽  
Natural Frequencies ◽  
Drive System ◽  
The Other ◽  
Dynamic Equations ◽  
Electromechanical Integrated ◽  
Drive Systems ◽  
Forced Responses ◽  
Design And Manufacture ◽  
Center Distance

In electromechanical integrated toroidal drive, eccentric center errors occur which has important influences on the dynamic behavior of the drive system. Here, the dynamic equations of the drive system with eccentric center are presented. Changes of the natural frequencies and vibrating modes along with eccentric center distance are analyzed. The forced responses of the drive system to eccentric center excitation are investigated. Results show that the eccentric center causes some natural frequencies to increase, and the other natural frequencies to drop. It also causes some vibrations to become weak, and the other vibrations to become strong. The eccentric center has more obvious effects on the dynamic behavior of the planets. The results are useful in design and manufacture of the drive systems.

Computational Study of 16 kWth Furnace Cofired Using Pulverized Bituminous Coal and Liquified Petroleum Gas Operated in Un-Staged and Air-Staged Conditions

2020 ◽  
Vol 143 (8) ◽  
Author(s):  
Nitesh Kumar Sahu ◽  
Mayank Kumar ◽  
Anupam Dewan
Keyword(s):  
Particle Size ◽  
Coal Particle ◽  
Bituminous Coal ◽  
Computational Study ◽  
Pearson Correlation ◽  
Turbulence Models ◽  
The Other ◽  
Test Facility ◽  
Measured Temperature ◽  
Inlet Swirl

Abstract This paper presents a computational study on air-fuel combustion of bituminous coal and liquified petroleum gas (LPG) in a 16 kWth test facility with a coflow-swirl burner. The performance of three turbulence models is investigated for the furnace operated under both air-staged and un-staged conditions by comparing their predictions with the reported measurements of temperature and species concentrations. This comparison shows that the shear stress transport (SST) k–ω model and SST k–ω model with low-Re correction predict the profiles of temperature and species concentrations reasonably well, but significantly underpredict the temperature in the furnace core at axial locations away from the burner. On the other hand, the transition SST k–ω model provides better overall congruency with the measured temperature and species concentrations when compared with the other turbulence models used, as indicated by relatively higher values of the Pearson correlation coefficient at locations away from the burner. The present high-fidelity computational model developed is also capable of accurately simulating the effect of coal particle size on the furnace environment, which is verified by the match between the computational predictions and the experimental results for two different sized coal samples. The model is also used to investigate the effect of coal particle size on the internal recirculation zone (IRZ) and the reattachment length (LR) for the same inlet swirl number (SN). A decrease of nearly 50% in the coal sample size results in the increase of LR and IRZ length by 20% and 82.6%, respectively.

Three Component Velocity Field Measurements in the Stagnation Region of a Film Cooled Turbine Vane

2001 ◽  
Author(s):  
Marc D. Polanka ◽  
J. Michael Cutbirth ◽  
David G. Bogard
Keyword(s):  
Field Measurements ◽  
The Other ◽  
Test Facility ◽  
Laser Doppler Velocimeter ◽  
Stagnation Region ◽  
Turbine Engine ◽  
Mainstream Flow ◽  
Turbine Vane ◽  
Component Velocity ◽  
Very High

The showerhead region of a film cooled turbine vane in a gas turbine engine involves a complex interaction between mainstream flow and coolant jets. This flow field was studied using three-component laser Doppler velocimeter measurements in a simulated turbine vane test facility. Measurements were focused around the stagnation row of holes. Low and high mainstream turbulence conditions were used. The spanwise orientation of the coolant jets, typical for showerhead coolant holes, had a dominating effect. Very high levels of turbulence were generated by the mainstream interaction with the coolant jets. Furthermore, this turbulence was highly anisotropic, with the spanwise component of the turbulent fluctuations being twice as large as the other components. Finally, there was an interaction of the high mainstream turbulence with the coolant injection resulting in increased turbulence levels for the spanwise velocity component, but had little effect on the other velocity components.

Analytical Determination of Shock Response Spectra for an Impulse-Loaded Proportionally Damped System

Volume 1 ◽  
2004 ◽  
Author(s):  
R. David Hampton ◽  
Nathan S. Wiedenman ◽  
Ting H. Li
Keyword(s):  
Transient Response ◽  
Shock Loading ◽  
Response Spectrum ◽  
Response Spectra ◽  
Analytical Determination ◽  
System Response ◽  
Mechanical Shock ◽  
Shock Response ◽  
Mass Spring ◽  
The Impact

Many military systems must be capable of sustained operation in the face of mechanical shocks due to projectile or other impacts. The most widely used method of quantifying a system’s vibratory transient response to shock loading is called the shock response spectrum (SRS). The system response for which the SRS is to be determined can be due, physically, either to a collocated or to a noncollocated shock loading. Taking into account both possibilities, one can define the SRS as follows: the SRS presents graphically the maximum transient response (output) of an imaginary ideal mass-spring-damper system at one point on a flexible structure, to a particular mechanical shock (input) applied to an arbitrary (perhaps noncollocated) point on the structure, as a function of the natural frequency of the imaginary mass-spring-damper system. For a response point sufficiently distant from the impact area, many Army platforms (such as vehicles) can be accurately treated as linear systems with proportional damping. In such cases the output due to an impulsive mechanical-shock input can be decomposed into exponentially decaying sinusoidal components, using normal-mode orthogonalization. Given a shock-induced loading comprising such components, this paper provides analytical expressions for the various common SRS forms. The analytical approach to SRS-determination can serve as a verification of, or an alternative to, the numerical approaches in current use for such systems. No numerical convolution is required, because the convolution integrals have already been accomplished analytically (and exactly), with the results incorporated into the algebraic expressions for the respective SRS forms.

Study on Mechanisms of a Mini-Instrument for Sound Source Localization

2011 ◽  
Vol 368-373 ◽  
pp. 624-628
Author(s):  
Qing Sheng Wang ◽  
Xin Jiang ◽  
Xiao Hang Liu
Keyword(s):  
Dynamic Behavior ◽  
Source Localization ◽  
Sound Source ◽  
Microphone Arrays ◽  
The Other ◽  
Sound Source Localization ◽  
Special Relationship ◽  
Ormia Ochracea ◽  
Compact Structure ◽  
New Instrument

Sound source localization is always of great value in many engineering applications. In this paper, a new instrument is designed to accomplish the purpose of localizing the sound source by a relatively compact structure. This bionics structure is designed to mimic the localization function of the ears of the parasitoid fly Ormia ochracea, and it consists of three elastic diaphragms, three bars which connected to the diaphragms, and the other mechanical components. The analysis of this structure’s dynamic behavior shows that the incident angles of the sound have special relationship to the responses of this instrument, and the incident angles can be estimated by detecting the vibrations of the three elastic diaphragms. Compared with traditional microphone arrays, this instrument has the advantage of compaction and higher integrated level.

Air Release During Column Separation

1983 ◽  
Vol 105 (1) ◽  
pp. 113-118 ◽  
Author(s):  
Muin Baasiri ◽  
J. Paul Tullis
Keyword(s):  
The Other ◽  
Test Facility ◽  
Empirical Equations ◽  
Column Separation ◽  
Free Air ◽  
Dissolved Air

Air release caused by column separation in a pipeline was investigated in a test facility where column separation could be generated for any desired length of time. The temperature, pressure, amount of dissolved air, and the other variables affecting the process were carefully controlled. Tests were made for cases where there was no initial free air in the system and for cases where there was some initial free air. The parameters influencing air release were identified and empirical equations developed for predicting the amount of air released during each cycle of column separation.

Design Considerations for a State of the Art Development Test Cell for Aeroengines

1994 ◽  
Author(s):  
Roger C. Stevens ◽  
David J. Piggott
Keyword(s):  
State Of The Art ◽  
Test Cell ◽  
The Other ◽  
Test Facility ◽  
Cell Design ◽  
Test Bed ◽  
New Developments ◽  
Design Considerations ◽  
Technological Developments ◽  
Reverse Thrust

A number of new considerations are beginning to influence the design of development aeroengine test facilities due to technological, environmental and regulatory developments. Whilst the technological developments are of an evolutionary nature, the other developments, for example, the imposition of mandatory environmental noise constraints and the requirement to perform in-cell reverse thrust testing for early Extended Twin Operations certification, may impose step changes in test facility design. This paper examines the influence of these new developments on test cell design and describes how the new requirements were integrated with the traditional considerations in the design of a new “sea level” Test Bed in Derby, UK.

Temperature Fluctuations Inside the CANDU Reactor Moderator Test Facility (MTF)

2012 ◽  
Author(s):  
Araz Sarchami ◽  
Nasser Ashgriz ◽  
Marc Kwee
Keyword(s):  
High Temperature ◽  
Tube Bundle ◽  
Three Dimensional ◽  
Symmetry Plane ◽  
Temperature Fluctuations ◽  
The Other ◽  
Test Facility ◽  
Temperature Distributions ◽  
Frequency Fluctuations ◽  
Temperature Liquid

Three dimensional numerical simulation is conducted on the CANDU Moderator Test Facility (MTF). Heat generation inside the tank is modeled through surface heating. Transient variations of the temperature and velocity distributions inside the tank are determined. The results show that the flow and temperature distributions inside the moderator tank are three dimensional and no symmetry plane can be identified. A high temperature zone, located on the top left corner of the tank, is identified. The inlet jets are found to flow along the walls of the tank and impinge on each other at the top of the tank. This impingement point is located more towards the right side of the tank. The impingement of these two flow result in a secondary downward moving jet, which penetrates into the tube bundle. This secondary jet divides the tank into two sides. One side contains high temperature liquid and the other side contains low temperature liquid. The temperature contours along the length of the tank have a saddle shape, with high temperatures towards the edges of the saddle. This is due to strong wall jet flows in the middle planes pushing the hotter fluid towards the end walls of the tank. Competition between the upward moving buoyancy driven flows and the downward moving momentum driven flows, results in the formation of circulation zones inside the tank. The numerical results for MTF indicate that the moderator tank operates in the buoyancy driven mode. Any small disturbances in the flow or temperature can make the system unstable and asymmetric. Once the system comes out of symmetry, it cannot go back to symmetry. This results in circulating buoyancy driven flow at one side and a momentum driven flow at the other side of tank. Different types temperature fluctuations are noted inside the tank: (i) large amplitude temperature fluctuations are mainly at the boundaries between the hot and cold; (ii) low amplitude temperature fluctuations are mainly in the core of the tank with more uniform temperature distributions; (iii) high frequency fluctuations are in the regions with high velocities; and (iv) low frequency fluctuations are in the regions with lower fluid velocities.

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