Impact Center and Restitution Coefficients for Accident Reconstruction

Ishikawa, Hirotoshi

doi:10.4271/940564

Cited by 30 publications

(20 citation statements)

References 1 publication

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“…The choice of orientation of the impact plane is discussed in detail by Brach, Welsh and Brach [13] and they indicate that a nominal crush plane for a collision is one that is orientated so that it bisects the angle between the contacting surfaces of the two vehicles at impact. Earlier work by Brach [12] and Ishikawa [19] suggest orientation to an axis parallel to a hypothetical flat crush plane common to both vehicles. It is suggested that such choices are likely to align closely with the perpendicular orientation to the impulse required to match with CRASH as outlined previously.…”

Section: Discussionmentioning

confidence: 99%

Equivalence of impact-phase models in two-vehicle planar collisions

Neades

2013

Proceedings of the Institution of Mechanical Engineers, Part D:

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Determining the pre-impact velocities of vehicles are of prime importance when investigating road traffic collisions. Two types of impact-phase model are in common use to achieve this purpose, those based on the conservation of linear and angular momentum as exemplified by the models presented by Brach and Ishikawa and the CRASH model which explicitly includes the conservation of energy. A summary of the various models is provided to show how the models are related to each other together with a brief discussion of their strengths and weaknesses. Of particular significance is that although there are differences between these models it is shown that they are equivalent provided certain conditions are satisfied, namely that the crush or impact plane is orientated perpendicular to the impulse. In addition it is shown that they produce identical results from consistent input data. Explicit conversion factors between the models are provided together with a novel method to transform coefficients of restitution between various orientations of the crush plane. This facilitates comparison and movement between the models and it is shown that the choice of model utilised for an individual collision depends largely on the availability of particular data.

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Section: Discussionmentioning

confidence: 99%

Equivalence of impact-phase models in two-vehicle planar collisions

Neades

2013

Proceedings of the Institution of Mechanical Engineers, Part D:

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“…The centroid of the damage is often used to define the points of application of the impulse and the shape of the damage is used to estimate the PDOF. Ishikawa [7] proposes a method whereby the impact centre is taken to be the mid-point of the contacting surfaces at the point of maximum deformation. The PDOF is then assumed to lie along a line perpendicular to the line of the contacting surfaces through the impact centre.…”

Section: Discussionmentioning

confidence: 99%

“…In CRASH3 calculations the point through which the impulse acts is normally assumed to be the centroid of the damaged area. Ishikawa [7] proposes a method whereby the impact centre is assumed to be the mid-point of the contacting surfaces at the point of maximum deformation. He provides a method whereby that point can be calculated.…”

Section: Ricsac Test 9 Variation Of Initial Vehicle Speeds With Pdofmentioning

confidence: 99%

“…It is used by over 85% of police forces in the UK and by organisations such as Loughborough University's Vehicle Safety Research Centre and the Transport Research Laboratory. Other models, such as the Planar Impact Mechanics (PIM) model described by Brach [6] and a similar derivation by Ishikawa [7] are also useful in collision reconstruction. These are essentially forward iterative models and do not directly predict pre-impact velocities.…”

Section: Introductionmentioning

confidence: 99%

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The Determination of Vehicle Speeds from Delta-V in Two Vehicle Planar Collisions

Neades¹,

Smith

2010

Proceedings of the Institution of Mechanical Engineers, Part D:

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The change of a vehicle's velocity, delta-V ( v), due to an impact is often calculated and used in the scientific investigation of road traffic collisions. In isolation however, this figure does not yield any information concerning the actual velocities of the vehicles and such information is often of prime concern to those investigating collisions. In this paper a method is developed which uses the change in velocity sustained by a vehicle in a planar collision to estimate the velocities of the vehicle before and after a collision. The key equations are derived from conservation of momentum, conservation of energy and restitution. As with the calculation of delta-V, the method requires an initial estimate of the principal directions of force. The pre and post impact angles of the vehicles' velocities can be used to obtain better estimates of the principal directions of force and of the coefficient of restitution. In collisions where it is difficult to analyse the vehicles' post-impact motion, this method provides a way to estimate the actual speeds of vehicles. To demonstrate the method, it is used to analyse one of the RICSAC collisions. The results of an analysis of other staged collisions illustrate the accuracy of the method.

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“…The magnitude and direction of this force varies during the course of impact and its point of application also moves (relative to the vehicle's centre of mass) as crush occurs. A detailed study of the location of the impact centre as a function of time was reported in [11] for forty-five car-to-car collision tests based on acceleration, velocity and displacement measurements. It documented significant movements of the impact centre for some crash configurations during the collision phase (50-150 ms at 10 ms intervals) but found that the impact centre was located near the mid-point of the contacting surface at maximum vehicle deformation.…”

Section: Introductionmentioning

confidence: 99%

Vector model of vehicle collisions for inferring velocity from loss of kinetic energy with restitution on residual crush surface

Lenard

2016

International Journal of Crashworthiness

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In the standard mathematical model that underpins the inference of velocity change from vehicle damage in road accident reconstruction, the point where the colliding bodies engage is taken to lie in the same location as the point of application of the average impact force, usually in the central region of the crush zone or on the residual crush surface. Mathematical and physical reasons suggest the fidelity of the model could be deepened by allowing for a separation of these points, for example by locating the impulse or average force in the central region of the crush zone and defining engagement (common velocity or rebound) relative to the crush surface. Refinement of the theory revealed that the solutions for the change of linear and angular velocity are unaffected. For long-running in-depth research studies, this means that historical calculations of velocity change (delta-V) and related analyses on such topics as injury risk curves, countermeasure effectiveness and accident scenarios are not potentially undermined. Relative and absolute velocity are however affected. This was illustrated using crash test data where adjustments of six and twelve centimetres resulted in changes of up to four percent in road speed.

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Impact Center and Restitution Coefficients for Accident Reconstruction

Cited by 30 publications

References 1 publication

Equivalence of impact-phase models in two-vehicle planar collisions

Equivalence of impact-phase models in two-vehicle planar collisions

The Determination of Vehicle Speeds from Delta-V in Two Vehicle Planar Collisions

Vector model of vehicle collisions for inferring velocity from loss of kinetic energy with restitution on residual crush surface

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