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Blog 2017
In this blog post, we discuss the simulation of test “MEA12” from this series. In this test, a 1980 Datsun 200 SX with initial speed of 15.6 m/s impacts a 1989 Chevrolet Sprint with initial speed of 6.7 m/s. The collision occurs in a 90-degree t-bone configuration. A depiction of the test is shown below.
The study of motion and of physical concepts such as force and mass is called dynamics. The part of dynamics that describes motion without regard to its causes is called kinematics [1]. Occupant kinematics is the study of kinematics as it applies to occupants within a motor vehicle. Broadly speaking, in accident reconstruction, one uses concepts of occupant kinematics to understand mechanisms of injury causation by identifying potential points of contact between an occupant’s body and the occupant cabin itself.
With the November 25, 2017 auto-update, Virtual CRASH 4 users will be able to create 360 degree videos and Virtual Reality videos. Virtual CRASH 4 users will also have more video output options available. As always, these updates are provided to Virtual CRASH users for free!
Collision physics in Virtual CRASH is based on rigid body dynamics. In particular, most vehicle versus vehicle impacts in Virtual CRASH are simulated using the Kudlich-Slibar impulse-momentum model. This model dates back to the 1960s [1, 2] and is the basis for other vehicle collision simulators used for accident reconstruction [3, 4]. Rigid body dynamics simulators are based on Newton Laws. Newton’s 3rd Law in particular, of course, leads to momentum conservation.
In our Blog post from last year (http://www.vcrashusa.com/blog/2016/6/6/adding-traffic-signal-symbols-to-animations), we discussed how to create 2-D traffic signal symbols in your simulation environment. At the bottom of that post, we also discussed how to add semaphore objects (3D traffic signal lights) in your environment. The semaphore object has undergone significant improvements in Virtual CRASH 4 which have been made available in the October 10, 2017 update.
In both Virtual CRASH 3 and Virtual CRASH 4, the kinematics tool can be a quick and easy way to control complex pre-crash motion involving inherently unstable systems such as motorcycle or bicycle + rider systems. It also allows the user to set up a simulation at the moment-of-impact, and kinematically propagate vehicles to the point-of-impact without the needed of fine-tuning steering and acceleration inputs.
Virtual CRASH can be used to reconstruct motorcycle impact cases quickly and easily. In this blog post we will use Virtual CRASH to reconstruct “Case Study 1” presented in “Linear and Rotational Motion Analysis in Traffic Crash Reconstruction” by Keifer, Conte, and Reckamp.
Because impulses are only exchanged upon overlap of the vehicle polygon meshes, cases where you want to simulate directly wheel contact may require a little more work; remember, the wheels in Virtual CRASH are not part of the vehicle polygon mesh, and so are not considered by the collision detection algorithm. One technique to solve this problem is to directly install rigid body wheels, which is shown in the Knowledge Base post here. Another technique involves simply modifying the polygon mesh of your vehicle. This is shown below.
In Virtual CRASH you can create complex road geometries using the plane object. In this post, we will create a highway interchange ramp.
In this latest installment, we continue with our exploration of the Research Input for Computer Simulation of Automobile Collisions (RICSAC) test series. These tests make excellent benchmarks with which to study just how quickly and accurately Virtual CRASH can reproduce accident cases.
