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Technical Paper

Validation of PC-Crash - A Momentum-Based Accident Reconstruction Program

1996-02-01
960885
PC-Crash is a Windows™ - based accident reconstruction program developed in Graz, Austria by Dr. Hermann Steffan. ...Hermann Steffan. PC-Crash collision analysis results are compared with previously published staged collision data. ...The staged collisions were reconstructed using PC-Crash and the trajectories were compared to actual measurements of the skid marks and rest positions.
Technical Paper

Data from Five Staged Car to Car Collisions and Comparison with Simulations

2000-03-06
2000-01-0849
Five collisions were staged in order to evaluate PC-Crash, a simulation program used for investigating motor vehicle collisions. Both vehicles were moving in all of the staged collisions at 1:1 or 2:1 speed ratios. ...Firstly, collision parameters were calculated from measured data, and used as input to the PC-Crash collision model. Secondly, the post-impact vehicle paths and rest positions were used to determine the pre-impact speeds. ...Using the PC-Crash "Optimizer" to reconstruct the five collisions, the error in calculated pre-impact speeds of the ten vehicles ranged from-3.3 to +4.1 km/h.
Technical Paper

Measuring and Modeling Suspensions of Passenger Vehicles

2013-04-08
2013-01-0774
Numerical parameters describing suspension stiffness and damping are required for 3D simulation of vehicle trajectories, but may not be available. This paper outlines a simple, portable method of measuring these properties with a coefficient of variation of 5% on stiffness. 24 of 26 vehicles tested were significantly stiffer in roll than pitch, complicating analyses with models that don't include anti-roll. Suspension parameters did not correlate with static wheel load distribution, and damping coefficient did not correlate with natural frequency. Computer simulations of the speed required to initiate rollover in an S-curve were highly sensitive to the suspension parameters used. When pre-impact tire marks and rollover distance were considered, the simulations became almost insensitive to suspension parameters.
Technical Paper

Empirical Testing of Vehicular Rotational Motion

2012-04-16
2012-01-0602
Vehicles often rotate during traffic collisions due to impact forces or excessive steering maneuvers. In analyzing these situations, accident reconstructionists need to apply accurate deceleration rates for vehicles that are both rotating and translating to a final resting position. Determining a proper rate of deceleration is a challenging but critical step in calculating energy or momentum-based solutions for analytical purposes. In this research, multiple empirical tests were performed using an instrumented vehicle that was subjected to induced rotational maneuvers. A Ford Crown Victoria passenger car was equipped with a modified brake system where selected wheels could be isolated. The tests were performed on a dry asphalt surface at speeds of approximately 50 mph. In each of the tests, the vehicle rotated approximately 180 degrees with the wheels on one side being completely locked.
Technical Paper

Uncertainty in Calculations Using Lambourn's Critical Speed Procedure

2013-04-08
2013-01-0779
Critical Speed Formula (CSF) belongs to the canon of tools used in reconstruction of vehicle accidents. It is used to calculate vehicle speed at the beginning of tire yaw marks and, together with the entire methodology of processing the information contained in the marks into the data, is often referred to as the Critical Speed Method (CSM). Its great practical importance as well as recurring doubts as to the reliability make it one of the best experimentally and theoretically studied methods. Although the CSF applies in fact to a point mass, it is used with reference to a vehicle, i.e., an increasingly complicated multi-body system. Accident reconstruction experts point out the particular usefulness of Lambourn's research concerning the CSM in respect to a passenger car.
Technical Paper

Determination of Critical Speed, Slip Angle and Longitudinal Wheel Slip based on Yaw Marks Left by a Wheel with Zero Tire Pressure

2016-04-05
2016-01-1480
This article presents the results of an analysis of the yaw marks left by a car with normal pressure in all tires and then normal pressure in three tires and zero in one rear tire. The analysis is a continuation of research on influence of reduced tire pressure on car lateral dynamics in a passing maneuver, discussed in the SAE paper No. 2014-01-0466. Preliminary analysis of yaw marks has shown, that a wheel with zero pressure deposits a yaw mark whose geometry differs from the yaw mark made by a wheel with normal pressure based on which we could calculate: critical speed, slip angle and longitudinal wheel slip. The aim of the presented research was to analyze the yaw marks left by car with zero pressure in one rear wheel in order to check the possibility of determining the vehicle critical speed, slip angle and longitudinal wheel slip. It was reached by performing bench and road tests during which the vehicle motion parameters were recorded using GPS Data Logging System.
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