2014 CDR summit DVD
C
2014 Vol.9 Iss.1
ollision C The International Compendium for Crash Research
Volume 9 Issue 1
SPRING 2014
Collision: The International Compendium for Crash Research
Validating CDR Data Through Crash Testing
Signs of a Wreck
Volume 9, Issue 1 - Spring 2014
How to Spot a Rolling Disaster and Testing and Simulation
3D Simulation of a Crash Test Series in SIMON Utilizing A, B, C and D Stiffness Coefficients
collisionmagazine.com
Analysis of Motorcycle and Rider Limits on a Curve
An Amazing
Speed Computation
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Contents
Spring 2014
Volume 9 Issue 1
inside
10
4
Letter From the Editor
8
NAPARS: Letter From the President
features 10
Three Dimensional Simulation of a Crash Test Series in SIMON Utilizing A, B, C and D Stiffness Coefficients by Jeffrey Suway, Anthony Cornetto, Ronny Wahba, John Swanson, Fawzi Bayan
222
My Turn At the Wheel: An Amazing Speed Computation by Erik Carlsson
28
Analysis of Motorcycle and Rider Limits on a Curve by Nathan A. Rose, Neal Carter, and David Pentecost
38
Signs of a Wreck: How to Spot a Rolling Disaster by Dan H. Wyatt
75
Signs of a Wreck: Testing and Simulation by Rusty Haight and Sean Haight
86
Validating Crash Data Retrieval Tool Data through Crash Testing by James D English
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28
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38
Collision Magazine - Volume 9 Issue 1 3
THREE DIMENSIONAL SIMULATION OF A CRASH TEST SERIES IN SIMON UTILIZING A, B, C, AND D STIFFNESS COEFFICIENTS
A
bstract A method for determining A, B, C, and D stiffness coefficients for simulation in HVE-SIMON using DyMESH has been used to simulate the Yaris crash test series conducted at the 2013 ARC-CSI Crash Conference in Las Vegas. This paper will present a comparison between the real world crash tests and the HVE-SIMON simulations. HVE version 9.1, SIMON version 4.11, and DyMESH version 3.1 were used for the studies presented in this paper.
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ntroduction A and B stiffness coefficients rely on the basic principle that a vehicles structure absorbs energy and deforms similar to a linear spring. These methodologies rely on a minimum force, energy, or more often, a barrier impact speed required to initiate vehicle crush. Additionally, the results increase in accuracy as the number of crash tests, at varying speeds, increases. Using these standard methods, the crush across the width of the vehicle is used to determine the amount of energy absorbed. This process is a two-dimensional process and does not include the third dimension, crush height.
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Jeffrey Suway Anthony Cornetto Ronny Wahba John Swanson Fawzi Bayan S-E-A, Ltd. Engineering Dynamics Corporation's (EDC) Human Vehicle Environment (HVE) SImulation MOdel Non-linear (SIMON), using the DyMESH model, allows three-dimensional vehicle meshes and analyses. Based on the methodology that DyMESH uses to calculate collision forces, the height of the crush becomes a factor. Because of this, the stiffness model incorporated in DyMESH is a threedimensional model using A, B, C, and D stiffness coefficients. Previous work by Cornetto et al. [1] has shown a method for calculating the A, B, C, and D stiffness coefficients for HVE-SIMON, based on the existing crash test data. In Cornetto et al. the resulting crash pulse and deflectiontime history, as predicted by HVE-SIMON using the derived three dimensional stiffness coefficients, are compared to the data from the NHSTA crash test. Additionally, Suway et al. [2] has shown how the method proposed in Cornetto et al. compares to SIMON with default, 2D stiffness coefficients, as well as EDSMAC4 with default 2D stiffness coefficients. The authors’ methodology has been applied to a NHTSA crash test of a Toyota Yaris and the resulting stiffness coefficients have been input into HVESIMON. The results of simulations representing the NHTSA crash test and the ARC-CSI crash tests are compared to data recorded during the real world testing as well as post-crash crush measurements. www.collisionpublishing.com
Collision Magazine - Volume 9 Issue 1 11
rn u T My
l e e h W e h at t
An Amazing Speed Computation By: Erik Carlsson
T
his article is about a 3-vehicle collision that happened in the middle of a February night on a four-lane westbound bridge in New Jersey. There was a light rain at the time, and the bridge was covered with what is often described as black ice. [Of course we all know that black ice is not black. It is completely transparent, and because of this undetectable – except for the fact that at night it reflects brightly the light from tail lamps of vehicles in front.] Water on ice acts like a lubricant, making ice very slippery, and some vehicle drivers on the bridge were unable to control their vehicles. The driver of a minivan, traveling slowly in the far left lane was at the highest point of the bridge when he observed a stopped vehicle some distance ahead in his lane. He applied the brakes, but the vehicle began to slide. It turned around completely and came to rest against the adjacent concrete barrier, facing east, still occupying part of the fourth lane. (There was no breakdown lane on the left side of the bridge.) The driver decided to continue his travel, and began his intended U-turn just as a car traveling very slowly in the lane second from the right was abreast.1 When the minivan was halfway through the intended U-turn it was broadsided by a company van traveling in the second lane. The collision was very severe, and the minivan was propelled sideways at such a speed that it not only caught up with the car ahead in that lane, but struck the car with a force high enough to cause its rear window to break. The damage to the car was such that the insurance company subsequently declared it a total loss. Naturally, there was substantial damage also to the minivan’s left side, though not as extensive as that of the side struck by the company van. The minivan was completely demolished at the two
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impacts, and the rescue crew had to cut off the roof to extract a passenger. The drivers describe the accident: The driver of the minivan stated at the police investigation that he did not see the company van approaching.2 The driver of the company van stated that the minivan suddenly crossed the travel lanes right in front of him, and that there was nothing he could do to prevent the collision. He did not know how fast he was going, or that the road was icy until he stepped out of his van following the accident (when he slipped and fell.) He had not noticed the warning sign that reads “BRIDGE FREEZES BEFORE ROAD.” The driver of the car stated that he was going no faster than 15 mph due to the slippery road conditions. Careless driving? There is little doubt that most accident reconstruction analysts would consider the driver of the minivan the culprit, causing the accident by attempting to make a U-turn on an icy bridge right in front of an approaching vehicle. But what about the other two drivers? Were they merely unfortunate victims of the minivan driver’s attempt to make a U-turn on a slippery highway in the middle of the night? Well, the driver of the car can hardly be accused of having contributed to the accident by driving slowly in the second lane on the four-lane ice-covered bridge. (He was nevertheless named as a defendant in the lawsuit that followed!) Of course, it can be argued that drivers of slow-moving vehicles should al-ways use the lane to the far right, a lane that is often called the “slow lane.” If he had done so, his car would not have been struck by the minivan. But what about the driver of the company van? Was he careless in any way? No, not according to an accident reconstruction firm that analyzed the accident. In their
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report, the analysts stated that the driver of the company van was traveling at a speed of 35 mph, and that this was a reasonable speed! Hence the driver of the company van was not careless and did not cause or contribute to the accident.
ergy would be equal to the damage energy of each side of the minivan. But if so, their computation would not show Delta-V, but Equivalent Barrier Speed, which in a case like this are two very different speeds.
Ingenious Speed computations? How did the analysts determine that the speed of the company van was 35 mph when the accident happened? Well, in their report they stated that when data about the damage to the minivan’s passenger side were entered in the EDCRASH computer program, the computer showed a Delta-V of 25 mph of the company (!) van, and 10 mph when data about the damage to the minivan’s left side was entered. Hence the pre-impact speed of the company van was 35 mph, they stated!
In any case, one can easily see that there is something fundamentally wrong with the speed computation. If indeed the speed of the company van was 35 mph when it broadsided the minivan, and the resulting Delta-V was 25 mph, it would mean that the speed of the company van was reduced to 10 mph during the impact. But this would also mean that during the impact, the broadsided minivan reached a lateral speed of 10 mph. Thus the minivan would have had a Delta-V of 10 mph in the direction of the travel lane, while that of the much heavier company van was 25 mph. This is of course impossible since conservation of linear momentum applies.
How the analysts made the EDCRASH computer program show the Delta-V of the company van based on the damage to the minivan was not explained in the report, nor did they include the creative computations. It may perhaps be reasonable to assume that what the analysts did was to compute the energy dissipated by the deformation of each side of the minivan, and next calculate the speed at which the company van’s kinetic en-
The weight of the company van was 1.6 times that of the minivan. Hence the lateral Delta-V of the minivan had to be 1.6 times the Delta-V of the company van. Thus, if the Delta-V of the latter was 25 mph, that of the minivan had to be 40 mph. But if the company van was moving at 40
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Collision Magazine - Volume 9 Issue 1 23
Analysis of Motorcycle and Rider Limits on a Curve Nathan A. Rose, Neal Carter, and David Pentecost Kineticorp, LLC
F
rom 1975 to 1980, H.H. Hurt investigated 4,500 motorcycle accidents – 900 with onscene, in-depth investigations and 3,600 using police reports – to identify common factors that contributed to causing these accidents [1]. The accidents in Hurt’s dataset occurred in the Los Angeles, California area. He found that “the most common motorcycle accident involve[d] another vehicle causing the collision by violating the right-of-way of the motorcycle at an intersection, usually by turning left in front of the oncoming motorcycle because the car driver did not see the motorcycle.” In these intersection collisions, the motorcycle rider was “usually inconspicuous in traffic, inexperienced, untrained, unlicensed, unprotected and uninsured and [did] a poor job of avoiding the collision.” In addition to these intersection collisions, “approximately one-fourth of [the] motorcycle accidents were single vehicle accidents involving the motorcycle colliding with the roadway or some fixed object in the environment.” Hurt further found that “in the single vehicle accidents, motorcycle rider error was present as the accident precipitating factor in about twothirds of the cases, with the typical error being a slide-out and fall due to overbraking or running wide on a curve due to excess speed or undercornering…” In an earlier article, Hurt had also reported that “environmental problems such as animals in the roadway, oil, water, and gravel contamination of the roadway, grooved freeways, [and] railroad tracks” can contribute to motorcycle accidents [2]. 28 Collision Magazine - Volume 9 Issue 1
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Hurt’s findings provide a statistical picture of the factors that can contribute to the occurrence of motorcycle accidents. However, reconstructionists are sometimes asked to determine which of these factors played a role in a particular accident. For example, suppose that a motorcyclist loses control and falls down while traveling through a curve that contains an area of deteriorated roadway. For this type of accident, questions may arise regarding the role that the deteriorated roadway played in causing the accident. In these cases, the mere presence of deteriorated roadway in the area of the accident does not establish that this deterioration played a direct role in the accident. Other possible factors – such as speed – should be considered, as should the specific characteristics of the deterioration and the effect it would likely have on the motorcycle. In such a case, the motorcycle rider may have lost control because they entered the curve at too high of a speed and this speed led to what Hurt referred to as “overbraking” or “undercornering”. Acci-
dent statistics can certainly provide a useful list of possible factors and worthwhile lines of inquiry in such a situation. However, these statistics cannot enable a determination of which possible factors contributed in a specific instance. Identification of the factors contributing to a particular accident must ultimately rely on the physical evidence from that accident and on the physics that elucidates the meaning of that evidence. This article focuses on single-vehicle motorcycle accidents that occur on curves and explores the physics that would enable a reconstructionist to determine the role the rider’s actions played in the accident. Specifically, the circumstances that might lead to the following two types of rider error are analyzed: (1) “a slide-out and fall due to overbraking” and (2) “running wide on a curve due to excess speed or undercornering.” These rider errors typically lead to the motorcycle falling down and sliding on the ground or to the motorcycle impacting a roadside object.
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Collision Magazine - Volume 9 Issue 1 29
SIGNS OF A WRECK How to spot a Rolling Disaster Dan H. Wyatt
Collision Service Investigators of North Carolina, LLC.
Editors Note
How often has a crash been investigated where the assumption was made that the involved vehicle(s) were in “essentially good as new” condition but, unknown to the investigator, one or more of the involved vehicles had been subjected to a prior repair which wasn’t necessarily up to par or which didn’t leave the involved vehicle in anything close to the same shape it was in when it was new? Dan Wyatt of Collision Service Investigators of North Carolina has over 25 years of auto body repair experience and has been licensed as a Motor Vehicle Damage Appraiser by the North Carolina Department of Insurance since 2003. He has obtained more than 17 training certificates from the Inter-Industry Conference Auto on Collision Repair (I-CAR), which was formed by the collision industry in 1979. This authorized reprint of part of his book “Signs of a Wreck” together with the discussion of a crash test involving one of the vehicles Mr Wyatt evaluated is offered as, at least, “food for thought” for the next time a vehicle involved in a crash you’re working doesn’t seem to have performed “quite as anticipated.” His work here includes some basics of auto body repair and offers some valuable insight on what to look for toward trying to identify inadequate repairs which might affect vehicle performance in a crash in a straight-forward, easy-to-read first person approach. The complete book is available from Mr Wyatt at 704-216-0081; www.csiofnc.com or email: dwyatt@csiofnc.com 38 Collision Magazine - Volume 9 Issue 1
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ntroduction The original book “Signs of a Wreck” was designed to provide general information and insight for consumers as well as used auto dealers in an effort to help them avoid unknowingly purchasing a damaged and inadequately repaired vehicle. At least some of the material is applicable to the crash investigator or reconstructionist who may want to evaluate whether or not one or more of the vehicle(s) involved in a crash may have been previously repaired and that repair’s effectiveness may play a role in the performance of that vehicle during the subsequent crash.
The original book includes suggestions for the potential used car buyer with respect to the condition of a vehicle including what to look for when buying a used car and sources of information with respect to that vehicle’s history. This excerpt of “Signs of a Wreck” is focused on those portions of the original book which relate to the techniques best suited to the crash investigator rather than the consumer.
V
ehicle Exterior Inspection Assuming the reader is involved in investigating a crash where one or more of the involved vehicles may have been involved in a previous crash and repaired to one degree or another, the logical place to start would seem to be to conduct a visual inspection of the vehicle in an effort to determine if it might have been previously repaired. The effectiveness of the repairs would come later.
One way to identify previous repair(s) made to a vehicle is to spot color variance or mismatched paint. At some point in time, we have all looked at a vehicle and wondered if there was a mismatch in the paint—a color variance. Depending on the amount of sunlight and the angle you are viewing the car from, a color variance in the paint may be obvious or may not show up at all.
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Collision Magazine - Volume 9 Issue 1 39
ANIMATION FOR THE REAL WORLD
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Validating Crash Data Retrieval Tool Data thRough Crash Testing James D English James D English and Associates
S
ooner or later everyone in the collision ence, and move methodically through how your reconstruction world will find themselves investigation was performed and your foundation testifying in a deposition or on the witness for your conclusion, but what about a question stand offering an expert opinion about how along the lines of “How has the CDR Tool been a given crash occurred. Whether on the private side validated?” or the law enforcement side, there’s a point where As your mind starts to race on how stall for a few each of us will research and prepare for just about precious seconds and how to answer, you may wonany question. But no matter how well we prepare der, is he asking about the “validation” of the CDR or try to predict what questions may be coming, Tool itself, about the “validation” data recorded there may still be something coming “out of left in the module, or could it be the “validation” of field” that we may not have thought of. You can source of the data? 86 Collision Magazine - Volume 9 Issue 1 www.collisionpublishing.com handle questions about your training and experi-
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