Second Paper: Deep Drawing and Free Forming Using a Water Hammer Technique

1964 ◽  
Vol 179 (1) ◽  
pp. 222-233 ◽  
Author(s):  
A. P. Vafiadakis ◽  
W. Johnson ◽  
I. S. Donaldson
Keyword(s):  
Deep Drawing ◽  
Time History ◽  
Water Hammer ◽  
High Rate ◽  
Pressure Time ◽  
Order Of Magnitude ◽  
History Of ◽  
Overall Efficiency ◽  
Initial Movement ◽  
Better Than

Earlier work on a water-hammer technique for high-rate forming of sheet metal has been extended to include work on deep drawing using lead plugs. A study of the pressure-time history of a deforming blank during its initial movement is reported. An assessment of the overall efficiency of the process has been made and is found to be about 50 per cent; this is an order of magnitude better than that found with comparable electro-hydraulic and explosive methods.

scholarly journals Comparison of Novel Seismic Protection Devices to Attenuate the Earthquake Induced Energy

Actuators ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 73
Author(s):  
Osman Hansu ◽  
Esra Mete Güneyisi
Keyword(s):  
Lateral Displacement ◽  
Time History ◽  
Seismic Protection ◽  
Base Shear ◽  
Seismic Demands ◽  
Nonlinear Time History Analyses ◽  
History Of ◽  
Protection Devices ◽  
Nonlinear Time History ◽  
Better Than

This study addresses an alternative use of viscous dampers (VDs) associated with buckling restrained braces (BRBs) as innovative seismic protection devices. For this purpose, 4-, 8- and 12-story steel bare frames were designed with 6.5 m equal span length and 4 m story height. Thereafter, they were seismically improved by mounting the VDs and BRBs in three patterns, namely outer bays, inner bays, and all bays over the frame heights. The structures were modeled using SAP 2000 software and evaluated by the nonlinear time history analyses subjected to the six natural ground motions. The seismic responses of the structures were investigated for the lateral displacement, interstory drift, absolute acceleration, maximum base shear, and time history of roof displacement. The results clearly indicated that the VDs and BRBs reduced seismic demands significantly compared to the bare frame. Moreover, the all-bay pattern performed better than the others.

Analysis of Liquid Slug Motion in a Voided Line

1998 ◽  
Vol 120 (1) ◽  
pp. 74-80 ◽  
Author(s):  
J. Yang ◽  
D. C. Wiggert
Keyword(s):  
Momentum Transfer ◽  
High Speed ◽  
Time History ◽  
Air Entrainment ◽  
Phase Flow ◽  
Liquid Slug ◽  
Two Phase ◽  
Pressure Time ◽  
History Of ◽  
Good Agreement

A quasi-two-dimensional two-phase flow cylindrical model of slug motion in a voided line is developed that can reasonably predict the change of flow pattern of the slug, air entrainment, “holdup” and the distribution of axial velocity. However, when using the theory of incompressible momentum transfer to estimate the pressure-time history of slug at the elbow, the calculated results are not in good agreement with those of the experiments. Further analysis of the experimental results indicate that an acoustic, or waterhammerlike response may occur immediately upon impact of the high-speed slug with the elbow, and subsequently, the waveform exhibits momentum transfer due to the acceleration of the slug at the elbow.

A Method of Measuring Helicopter Landing Loads

1964 ◽  
Vol 68 (641) ◽  
pp. 323-329
Author(s):  
M. J. H. Harding
Keyword(s):  
Time History ◽  
Load Application ◽  
Research Station ◽  
List Type ◽  
Recording Equipment ◽  
Exact Degree ◽  
Helicopter Landing ◽  
History Of ◽  
Design Velocity ◽  
Better Than

SummaryTests have been made to examine the dynamic response of representative heliport structures to helicopter landing loads. The loads applied by an S.5S helicopter were measured by British European Airways and the corresponding strains, reactions and deflections occurring in the instrumented test platform were recorded by the Building Research Station.This paper describes the specially designed recording equipment fitted to the helicopter and discusses the data obtained from over 400 heavy landings. It is concluded that:—(a)The tyre deflection method used to measure applied load was better than the others considered.(b) Overall accuracy achieved was in the order of ± 10 to 15 percent.(c) Accuracy could have been improved if more time had been available to eliminate the effects of follower bounce and to establish the exact degree of sideloading present on the mainwheels.(d) There was inconsistency in oleo performance which had a marked effect on the time-history of load application.(e) The time-history of load application also depended on whether or not the rotor was running and providing lift.(f) In very few of the landings from a low hover and in none of the 30 or so run-on landings did all four wheels touch together; this is the most critical loading of the structure.(g) Despite the large number of heavy landings earlier in the trial the undercarriage finally failed at 19 fps which was considerably in excess of its design velocity.

scholarly journals A model and predictions for COVID-19 considering population behavior and vaccination

2021 ◽  
Author(s):  
Thomas Usherwood ◽  
Zachary LaJoie ◽  
Vikas Srivast
Keyword(s):  
United States ◽  
Disease Transmission ◽  
Transmission Rate ◽  
Time History ◽  
The United States ◽  
High Rate ◽  
Safety Level ◽  
History Of ◽  
Approach Zero ◽  
And Behavior

Abstract The effect of vaccination coupled with the behavioral response of the population is not well understood. Our model incorporates two important dynamically varying population behaviors: level of caution and sense of safety. Level of caution increases with infectious cases, while an increasing sense of safety with increased vaccination lowers precautions. Our model accurately reproduces the complete time history of COVID-19 infections for various regions of the United States. We propose a parameter d_I as a direct measure of a population’s caution against an infectious disease that can be obtained from the infectious cases. The model provides quantitative measures of highest disease transmission rate, effective transmission rate, and cautionary behavior. We predict future COVID-19 trends in the United States accounting for vaccine rollout and behavior. Although a high rate of vaccination is critical to quickly ending the pandemic, a return towards pre-pandemic social behavior due to increased sense of safety during vaccine deployment can cause an alarming surge in infections. Our results predict that at the current rate of vaccination, the new infection cases for COVID-19 in the United States will approach zero by August 2021. This model can be used for other regions and for future epidemics and pandemics.

Numerical Calculation of the Dynamic Responses of Vessel Mast Structure Under Air Explosion

2010 ◽  
Author(s):  
Xiaobin Li ◽  
Peng Zhang ◽  
Xing Wei ◽  
Weiguo Wu
Keyword(s):  
Time History ◽  
Data File ◽  
Dynamic Responses ◽  
Finite Element Software ◽  
Pressure Time ◽  
Calculation Results ◽  
History Of ◽  
Shock Resistance ◽  
Air Explosion ◽  
Explosion Load

Mast is defined as Grade A equipment which is essential for the safety and continued combat capability of the ship. Therefore, it is very necessary to evaluate the mast shock resistance under air explosion. However, it is very difficult to get the shock loading on the structure aroused by air explosion since it is varied with time and space. Flux-Corrected-Transport (FCT) algorithm is a high-order, monotone, preserving positive finite-difference algorithm. In this paper, a program is presented for air explosion load calculation based on FCT algorithm. Taking the coupling of air and mast into consideration, the pressure time history of each element on the surface of the mast is computed according to the program. A data file about the pressure load is written to integrate the commercial finite element software of LSDYNA. Furthermore, the dynamic responses of the mast are calculated based on LSDYNA. The capability of shock resistance under air explosion of the mast can be evaluated according to the calculation results, which can provide references for mast anti-explosion design.

scholarly journals Cavitation inception from bubble nuclei

2015 ◽  
Vol 5 (5) ◽  
pp. 20150006 ◽  
Author(s):  
K. A. Mørch
Keyword(s):  
Tensile Strength ◽  
Tap Water ◽  
Time History ◽  
Experimental Investigations ◽  
Cavitation Inception ◽  
Pressure Time ◽  
History Of ◽  
Cavitation Nuclei ◽  
Pressure Changes ◽  
Surrounding Liquid

The tensile strength of ordinary water such as tap water or seawater is typically well below 1 bar. It is governed by cavitation nuclei in the water, not by the tensile strength of the water itself, which is extremely high. Different models of the nuclei have been suggested over the years, and experimental investigations of bubbles and cavitation inception have been presented. These results suggest that cavitation nuclei in equilibrium are gaseous voids in the water, stabilized by a skin which allows diffusion balance between gas inside the void and gas in solution in the surrounding liquid. The cavitation nuclei may be free gas bubbles in the bulk of water, or interfacial gaseous voids located on the surface of particles in the water, or on bounding walls. The tensile strength of these nuclei depends not only on the water quality but also on the pressure–time history of the water. A recent model and associated experiments throw new light on the effects of transient pressures on the tensile strength of water, which may be notably reduced or increased by such pressure changes.

A New Model Based Signal Processing Scheme for Detecting Delay and Doppler in Bistatic Radars

2018 ◽  
Vol 27 (14) ◽  
pp. 1850229
Author(s):  
Seyed Vahab Shojaedini ◽  
Alireza Goldar
Keyword(s):  
Signal Processing ◽  
Time History ◽  
Joint Estimation ◽  
Processing Scheme ◽  
Model Based ◽  
History Of ◽  
Comparison Of The Results ◽  
Stationary Component ◽  
Processing Framework ◽  
Better Than

In this paper, a new method is presented for joint estimation of delay and Doppler in bistatic radars by using model-based signal processing framework. In the proposed method, the time history of each cell in ambiguity function is modeled as a stochastic process consisting of a stationary component caused by clutter and noise as well as a possible transient component which is caused by a target. Then some cells are indicated as candidates for being targeted based on estimating the higher order statistics of the above stochastic processes. Finally, the spatial processing scheme is performed to prune false candidates. To evaluate the proposed method, its performance is simulated under two different scenarios (i.e., slow and fast moving targets) which have been inspirited from real conditions. Comparison of the results obtained from the proposed method with its alternatives, shows its better performance in such a way that it detects fast targets at least 8% better than the best among all examined methods. Furthermore, the proposed method detects slow targets at least 4.3% better than the best among all examined methods. Both of the above superiorities are obtained in those conditions while the false alarm of the proposed method does not show the meaningful difference against other examined algorithms.

scholarly journals A model and predictions for COVID-19 considering population behavior and vaccination

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Thomas Usherwood ◽  
Zachary LaJoie ◽  
Vikas Srivastava
Keyword(s):  
United States ◽  
Disease Transmission ◽  
Transmission Rate ◽  
Time History ◽  
The United States ◽  
High Rate ◽  
Safety Level ◽  
History Of ◽  
Approach Zero ◽  
And Behavior

AbstractThe effect of vaccination coupled with the behavioral response of the population is not well understood. Our model incorporates two important dynamically varying population behaviors: level of caution and sense of safety. Level of caution increases with infectious cases, while an increasing sense of safety with increased vaccination lowers precautions. Our model accurately reproduces the complete time history of COVID-19 infections for various regions of the United States. We propose a parameter $$d_I$$ d I as a direct measure of a population’s caution against an infectious disease that can be obtained from the infectious cases. The model provides quantitative measures of highest disease transmission rate, effective transmission rate, and cautionary behavior. We predict future COVID-19 trends in the United States accounting for vaccine rollout and behavior. Although a high rate of vaccination is critical to quickly ending the pandemic, a return towards pre-pandemic social behavior due to increased sense of safety during vaccine deployment can cause an alarming surge in infections. Our results predict that at the current rate of vaccination, the new infection cases for COVID-19 in the United States will approach zero by August 2021. This model can be used for other regions and for future epidemics and pandemics.

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