Free fall drop tests to determine low speed stability and base pressure characteristics for blunt planetary entry bodies

1970 ◽  
Author(s):  
P. BUCE
Keyword(s):  
Free Fall ◽  
Base Pressure ◽  
Low Speed ◽  
Drop Tests ◽  
Speed Stability ◽  
Planetary Entry ◽  
Pressure Characteristics

scholarly journals Numerical Model Study of Prototype Drop Tests on Cube and Cubipod® Concrete Armor Units Using the Combined Finite–Discrete Element Method

2021 ◽  
Vol 9 (5) ◽  
pp. 460
Author(s):  
Giulio Scaravaglione ◽  
John-Paul Latham ◽  
Jiansheng Xiang
Keyword(s):  
Discrete Element Method ◽  
Validation Study ◽  
Free Fall ◽  
Discrete Element ◽  
Drop Test ◽  
Modeling Methodology ◽  
Model Study ◽  
Drop Tests ◽  
Rubble Mound Breakwaters ◽  
Element Method

This paper aims to evaluate the structural strength of unreinforced concrete armor units (CAU), named Cubipod®, used on rubble-mound breakwaters and coastal structures, through a numerical methodology using the combined finite–discrete element method (FDEM). A numerical modeling methodology is developed to reproduce the results of an experimental examination published by Medina et al. (2011) of a free-fall drop test performed on a 15 t conventional Cubic block and a 16 t Cubipod® unit. The field results of the Cube drop tests were used to calibrate the model. The numerically simulated response to the Cubipod® test is then discussed in the context of a validation study. The calibration process and validation study provide insights into the sensitivity of breakage to tensile strength and collision angle, as well as a better understanding of the crushing and cracking damage of this unit under drop test impact conditions.

scholarly journals Performance analysis of the protective effects of bicycle helmets during impact and crush tests in pediatric skull models

2012 ◽  
Vol 10 (6) ◽  
pp. 490-497 ◽  
Author(s):  
Tobias A. Mattei ◽  
Brandon J. Bond ◽  
Carlos R. Goulart ◽  
Chris A. Sloffer ◽  
Martin J. Morris ◽  
...  
Keyword(s):  
Impact Force ◽  
Compressive Force ◽  
Free Fall ◽  
Protective Effects ◽  
Human Cadaver ◽  
Bicycle Helmet ◽  
Bicycle Helmets ◽  
Drop Tests ◽  
Flat Steel ◽  
Human Skulls

Object Bicycle accidents are a very important cause of clinically important traumatic brain injury (TBI) in children. One factor that has been shown to mitigate the severity of lesions associated with TBI in such scenarios is the proper use of a helmet. The object of this study was to test and evaluate the protection afforded by a children's bicycle helmet to human cadaver skulls with a child's anthropometry in both “impact” and “crushing” situations. Methods The authors tested human skulls with and without bicycle helmets in drop tests in a monorail-guided free-fall impact apparatus from heights of 6 to 48 in onto a flat steel anvil. Unhelmeted skulls were dropped at 6 in, with progressive height increases until failure (fracture). The maximum resultant acceleration rates experienced by helmeted and unhelmeted skulls on impact were recorded by an accelerometer attached to the skulls. In addition, compressive forces were applied to both helmeted and unhelmeted skulls in progressive amounts. The tolerance in each circumstance was recorded and compared between the two groups. Results Helmets conferred up to an 87% reduction in so-called mean maximum resultant acceleration over unhelmeted skulls. In compression testing, helmeted skulls were unable to be crushed in the compression fixture up to 470 pound-force (approximately 230 kgf), whereas both skull and helmet alone failed in testing. Conclusions Children's bicycle helmets provide measurable protection in terms of attenuating the acceleration experienced by a skull on the introduction of an impact force. Moreover, such helmets have the durability to mitigate the effects of a more rare but catastrophic direct compressive force. Therefore, the use of bicycle helmets is an important preventive tool to reduce the incidence of severe associated TBI in children as well as to minimize the morbidity of its neurological consequences.

Low-speed stability analysis of the dual fuel waverider configuration

1996 ◽  
Author(s):  
Christopher Tarpley ◽  
Darryll Pines ◽  
Ajay Kothari
Keyword(s):  
Stability Analysis ◽  
Dual Fuel ◽  
Low Speed ◽  
Speed Stability

Low-Speed Aerodynamics of a Planetary Entry Capsule

1999 ◽  
Vol 36 (5) ◽  
pp. 659-667 ◽  
Author(s):  
Frank Y. Wang ◽  
Ozgur Karatekin ◽  
Jean-Marc Charbonnier
Keyword(s):  
Low Speed ◽  
Planetary Entry

An Explanation of Low-Speed Chatter Effects

1969 ◽  
Vol 91 (4) ◽  
pp. 951-958 ◽  
Author(s):  
T. R. Sisson ◽  
R. L. Kegg
Keyword(s):  
Cutting Tool ◽  
Cutting Edge ◽  
Physical Explanation ◽  
Low Speed ◽  
Tool Edge ◽  
Speed Stability ◽  
Physical Quantities

At low machining speeds, self-excited chatter behavior is dominated by factors which have never been satisfactorily explained. By studying the forces acting on the cutting tool right behind the cutting edge, the authors have developed a physical explanation for low-speed stability. This leads to an understanding, in terms of physical quantities, of how such variables as tool edge roundness, tool clearance angles, and chatter frequency affect stability. The explanation is consistent with all published experimental observations of low-speed chatter behavior.

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