This packet is intended for use in a mechanical engineering dynamics course. Dynamic loading in an automobile crash is used to present the argument for properly securing passengers, especially children, in moving vehicles. The material in this packet involves a crash test example, and the forces behind the crash. A short lecture outline is presented.
Time for presentation is estimated as 20 minutes.
Objective:
To introduce mechanical engineering students to basic safety concerns that involve
the
principles of dynamics.
This packet includes the following items:
• Lecture material for the instructor
• Overheads for use during the lecture
• Homework problem and instructor solution
• Exam problems and solutions
Files are found on disk, in WordPerfect 8 format. (This version converts nicely
to Word 97.)
Files are (in order of packet):
• Preview lecture outline
• Preview overheads
• Preview Assignment
Download Car Crash Test in printable Adobe Acrobat Format (pdf). This includes overheads in a ready to use format.
Homework problem solutions, exam problems, and exam solutions are available to qualified recipients. Send an email with request information to Dr. Donald Bloswick.
A. The Insurance Institute for Highway Safety compiles a yearly report of motor vehicle deaths among children under 13 years old.
B. The following is a compilation of the 1997 statistics on motor vehicle deaths:(OVERHEAD 1)
1. Child deaths in crashes have declined since 1975, but motor vehicle crashes still cause about 1 of every 3 injury deaths among children 12 and younger.
2. Among those 5-12 years old, crash injuries are the leading cause of death.
3. Most of the deaths are passenger vehicle occupants, and proper restraint use can reduce this problem.
4. Sitting in the rear instead of the front reduces fatal injury risk by 36 percent among children 12 and younger.
II. What Can Happen to a Child Held in Your Arms?
A. Many parents believe that the safest and most loving way to transport a small child or infant in a car is in their arms.
1. They are certain that if an accident is about to occur, they will have time and the strength to hold the child and protect him/her from injury. This is not true.
2. One of the most dangerous places in a car for a child is on the lap or in the arms of an adult. Children can be crushed by adults in a collision, and/or may not be restrained properly by an adult.B. Two recent studies clearly illustrate this danger to children.
(OVERHEAD 2)1. In a series of tests at the Highway Safety Research Institute of Michigan, male and female adult volunteers were safely fastened to a seat with lap and shoulder belts.
a. Each volunteer held a 17-pound "dummy" which represented the size and weight of a six-month-old baby.
b. Each was then subjected to simulated 15 and 30 mile per hour impacts. Not one of the volunteers was able to hold onto the "baby."
c. Even knowing the precise moment of impact and using all their strength, the baby was ripped from their arms and slammed into the dashboard.
(OVERHEAD 3)
2. A second study was sponsored by the Insurance Institute for Highway Safety in Washington, D.C.a. It shows what happens to infants held in the arms of adults who are not using proper restraining devices.
b. In this test, a 1979 4-door automobile was driven into a solid barrier at just 24 miles per hour.
c. The test shows that even if the adult is able to restrain the child, the unrestrained adult may crush the child.
d. The second major cause of death and injury to children in cars is being crushed by unrestrained adults.
References:
http://www.highwaysafety.org/
http://www.highwaysafety.org/safety_facts/fatality_facts/children.htm
• People 12 years and younger represented 20 percent of the U.S. population
in 1997 and 5 percent of motor vehicle deaths.
• Child deaths in crashes have declined since 1975, but motor vehicle crashes
still cause about 1 of every 3 injury deaths among children 12 and younger.
• Among these 5-12 years old, crash injuries are the leading cause of death.
• Most of the deaths are passenger vehicle occupants, and proper restraint use can reduce this problem.
• Sitting in the rear instead of the front reduces fatal injury risk by 36 percent among children 12 and younger.
In a series of tests at the Highway Safety Research Institute of Michigan, male and female adult volunteers were safely fastened to a seat with lap and shoulder belts.
• Each volunteer held a 17-pound "dummy" which represented the size and weight of a six-month-old baby.
• Each was then subjected to simulated 15 and 30 mile per hour impacts. Not one of the volunteers was able to hold onto the "baby."
• Even knowing the precise moment of impact and using all their strength, the baby was ripped from their arms and slammed into the dashboard.
A second study was sponsored by the Insurance Institute for Highway Safety in Washington, D.C.
•It shows what happens to infants held in the arms of adults who are not using proper restraining devices.
• In this test, a 1979 4-door automobile was driven into a solid barrier at just 24 miles per hour.
• This test illustrates why the second major cause of death and injury to children in cars is being crushed by unrestrained adults.
Consider the following scenario.
You are returning from a road trip to the Grand Canyon and are holding your
6-month old baby in your arms in the passenger seat of a 1997 minivan. It is
night and your child (ornery from a long day on the road) won't let you put
her down. The driver, also worn-out from the long, hot day, falls asleep at
the wheel while driving and rams into a 100-foot embankment of granite rock.
CASE 1
Assuming you are traveling at a rate of 30 miles per hour, and upon collision
the front end crushes a distance of 2 feet, find the force required to hold
the 16-pound baby in your arms. It can be assumed that the embankment experiences
no deformation and that the car's deceleration is linear. Are you strong enough
to hold this baby?
CASE 2
Now let's assume that you had purchased a 1998 minivan. This type of minivan
only crumples 1 foot upon collision, and protects the driver from leg and chest
injuries. What will be the effective force to hold the baby in this instance?
Is it any easier to hold the baby in this case?