Three-Dimensional Computations. Volume III. 60-Deg Oblique Impact.

1977 ◽  
Author(s):  
W. E. Johnson ◽  
V. Kucher
Keyword(s):  
Three Dimensional ◽  
Oblique Impact

scholarly journals Three-dimensional oblique water-entry problems at small deadrise angles

2012 ◽  
Vol 711 ◽  
pp. 259-280 ◽  
Author(s):  
M. R. Moore ◽  
S. D. Howison ◽  
J. R. Ockendon ◽  
J. M. Oliver
Keyword(s):  
Three Dimensional ◽  
Oblique Impact ◽  
Water Entry ◽  
Rigid Bodies ◽  
Normal Impact ◽  
Displacement Potential ◽  
Pressure Profiles ◽  
The Relationship ◽  
Wagner Theory ◽  
The Ideal

AbstractThis paper extends Wagner theory for the ideal, incompressible normal impact of rigid bodies that are nearly parallel to the surface of a liquid half-space. The impactors considered are three-dimensional and have an oblique impact velocity. A formulation in terms of the displacement potential is used to reveal the relationship between the oblique and corresponding normal impact solutions. In the case of axisymmetric impactors, several geometries are considered in which singularities develop in the boundary of the effective wetted region. We present the corresponding pressure profiles and models for the splash sheets.

Thermomechanical Finite Element Analysis of Impact-Induced Magnetic Erasures in Magnetic Storage Thin Film Media

2007 ◽  
Author(s):  
Ning Yu ◽  
Andreas A. Polycarpou ◽  
Jorge V. Hanchi
Keyword(s):  
Finite Element ◽  
Hard Disk Drives ◽  
Three Dimensional ◽  
Thermal Response ◽  
Rotating Disk ◽  
Oblique Impact ◽  
Magnetic Storage ◽  
The Finite Element Method ◽  
Element Analysis ◽  
The Impact

Oblique impact of a slider with a rotating disk in hard disk drives was analyzed using the finite element method. A three dimensional, thermomechanical, impact model was developed to study the mechanical and thermal response during the impact of a spherical slider corner with the disk. The model was validated by comparing finite element results with analytical solutions for homogeneous glass disk under simple conditions. Impact penetration, stress and incurred flash temperature were obtained for various normal impact velocities.

MADYMO Simulations of Occupant and Vehicle Kinematics in Offset and Oblique Barrier Tests

2005 ◽  
Author(s):  
Rex T. Shea ◽  
Jiri Kral
Keyword(s):  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Oblique Impact ◽  
Test Method ◽  
Vehicle Interior ◽  
Center Of Rotation ◽  
Frontal Impacts ◽  
Coordinate Origin ◽  
The Right

Oblique and offset impacts occur more frequently than full frontal impacts and the resulting occupant and vehicle kinematics are more complicated. Simulations of these test modes are more involved with added vehicle degrees of freedom. Additional occupant interactions with the vehicle interior need to be considered so that the occupant kinematics can be correlated more accurately. In order to capture the vehicle motion in an offset or oblique impact, a prescribed motion approach is preferred where the vehicle is given a three-dimensional motion with six degrees of freedom. With a planar motion assumption, the dominant angular motion about the vertical direction can be derived from linear accelerations measured at two locations where the vehicle deformation is a minimum. In a previous study the angular kinematics was given to a coordinate origin located on the vehicle centerline and longitudinally near the rear rocker. The instantaneous center of rotation was assumed to be fixed at this point during the event. This is referred to as Method I in this paper. A new approach, referred to as Method II, applied translational displacement to three bodies, which carried the passenger compartment through stiff spring elements. The displacements were integrated from measured accelerations, eliminating the uncertainty of a shifting center of rotation. Both methods assumed the vehicle frame between the front and rear rockers as a rigid body. The IP and steering column intrusions and floor deformations were neglected. The results from both methods were correlated to a pair of 40 kph 30 degree angle impact tests and an IIHS ODB test. Method II showed a slightly better timing correlation for the angle tests and the IIHS ODB test. However, both methods didn’t predict the lateral head contact for the driver in the left angle test and the passenger in the right angle test. More interior details have to be included in the model to capture the lateral motion of the occupants. The prescribed motion method is a more general approach than the commonly used inverse kinematics method, and can be applied to full frontal impact as well. The versatility of the method provides a basis for a modular approach in occupant simulations.

scholarly journals Air cushioning and bubble entrapment in three-dimensional droplet impacts

2010 ◽  
Vol 649 ◽  
pp. 135-163 ◽  
Author(s):  
PETER D. HICKS ◽  
RICHARD PURVIS
Keyword(s):  
Free Surface ◽  
Surface Deformation ◽  
Solid Wall ◽  
Three Dimensional ◽  
Oblique Impact ◽  
Droplet Radius ◽  
Liquid Density ◽  
Droplet Deformation ◽  
Approach Velocity ◽  
The Moment

Droplet deformation by air cushioning prior to impact is considered. A model is presented coupling the free-surface deformation of a droplet with the pressure field in the narrow air layer generated as a droplet approaches an impact. The model is based upon the density and viscosity in the air being small compared with those in the liquid. Additionally, the Reynolds number, defined using the droplet radius ℛ and approach velocity l, is such that lubrication forces dominate in the air layer. In the absence of significant surface tension or compressibility effects, these assumptions lead to coupled nonlinear integro-differential equations describing the evolution of a droplet free surface approaching a solid wall through air, with or without topography.The problem is studied numerically with a boundary-element method in the inviscid droplet coupled with a finite-difference method in the lubricating air. In normal impacts, air cushioning will be shown to deflect the free surface upwards, delaying the moment of touchdown and trapping a bubble. The volume of the bubble is found to be (μg4/3ℛ5/3/ρl4/3l4/3), where μg is the gas viscosity and ρl is the liquid density and the numerically computed pre-factor = 94.48. Bubble volumes predicted by this relationship are shown to be in good agreement with experimental observations. In oblique impact or impact with a moving surface with sufficient horizontal motion a bubble is not trapped beneath the approaching droplet. In this case, the region of touchdown is initially crescent shaped with air effects accelerating the moment of touchdown.

Multi-objective optimization of crash box filled with three-dimensional cellular structure under multi-angle impact loading

2021 ◽  
pp. 095440702199817
Author(s):  
Fangwu Ma ◽  
Hongyu Liang ◽  
Yongfeng Pu ◽  
Qiang Wang ◽  
Ying Zhao
Keyword(s):  
Energy Absorption ◽  
Impact Loading ◽  
Three Dimensional ◽  
Oblique Impact ◽  
Hexagonal Structure ◽  
Dynamic Responses ◽  
Surface Model ◽  
Gradient Distribution ◽  
Thin Walled Structures ◽  
Inclination Angles

Oblique impact loading conditions are common in automobile collision accidents, which strongly influence the energy absorption performance of thin-walled structures. In this paper, a novel three-dimensional (3-D) hexagonal structure-filled crash box with better comprehensive crashworthiness under multiple working conditions is proposed. First, the finite element models of four 3-D typical cellular structures (hexagon structure, re-entrant hexagon structure, star-shape structure, double arrow structure) are established. The dynamic responses of four structures under different impact angles (from 0° to 30°) and impact velocities (from 5 to 15 m/s) are discussed. The results reveal that the 3-D hexagonal structure has great advantages in terms of the energy absorption at varying inclination angles. Second, the 3-D hexagonal structure is filled in the crash box in the form of gradient distribution. The multi-island genetic algorithm (MIGA) based on the response surface model (RSM) is utilized to explore the optimal design of crash box. Compared with the traditional crash box, the optimal 3-D hexagonal structure-filled crash box increases 18.9% in specific energy absorption and decreases 21.7% in maximum peak force, which demonstrates great potential for applications in impact engineering.

scholarly journals Water entry of a body which moves in more than six degrees of freedom

2015 ◽  
Vol 471 (2177) ◽  
pp. 20150058 ◽  
Author(s):  
Y.-M. Scolan ◽  
A. A. Korobkin
Keyword(s):  
Degrees Of Freedom ◽  
Early Stage ◽  
Three Dimensional ◽  
Vertical Displacement ◽  
Oblique Impact ◽  
Water Entry ◽  
The Body ◽  
Body Motion ◽  
Elliptic Paraboloid ◽  
Over Time

The water entry of a three-dimensional smooth body into initially calm water is examined. The body can move freely in its 6 d.f. and may also change its shape over time. During the early stage of penetration, the shape of the body is approximated by a surface of double curvature and the radii of curvature may vary over time. Hydrodynamic loads are calculated by the Wagner theory. It is shown that the water entry problem with arbitrary kinematics of the body motion, can be reduced to the vertical entry problem with a modified vertical displacement of the body and an elliptic region of contact between the liquid and the body surface. Low pressure occurrence is determined; this occurrence can precede the appearance of cavitation effects. Hydrodynamic forces are analysed for a rigid ellipsoid entering the water with 3 d.f. Experimental results with an oblique impact of elliptic paraboloid confirm the theoretical findings. The theoretical developments are detailed in this paper, while an application of the model is described in electronic supplementary materials.

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