ARTICLES

7/14/2009· Human Factors

Reaction Time

By: Kristopher J. Seluga, PE

When a person becomes aware of a dangerous situation, a time-interval must elapse before he can take defensive action against it. This time interval, commonly called the reaction time, has been found to be about 0.7 second for all normal persons, regardless of their background and training. This suggests that the reaction time depends on some basic aspect of the human physiology-involving the brain, nervous system, and muscles-which does not vary much from person to person.

7/14/2009· Accident Investigation & Reconstruction

Lawnmower Accidents

By: Kristopher J. Seluga, PE

There are approximately 180,000 lawnmower accidents per year. In this introductory presentation, we undertake to describe the various ways in which these accidents occur.

7/14/2009· Forensic Analysis

Stepladder Instability Testing

By: Kristopher J. Seluga, PE

According to Consumer Product Safety Commission (CPSC) accident estimates, tens of thousands of stepladder accidents requiring emergency room treatment occurred annually in the United States. Approximately 85-90% of these accidents involve the user falling from the ladder and 8-9% of these injuries are serious enough to require that the victim be admitted to a hospital. In addition to posing a severe health concern, these accidents have significant loss-of-wages and high medical expense implications.

7/14/2009· Forensic Analysis

Automobile Braking

By: Kristopher J. Seluga, PE

Accident reconstructionists are often called on to determine the distance that a car, covers while being braked to a stop. Conversely, the reconstructionist may be given information as to the length of the skidmarks left by a car on the roadway, and may be asked to determine how fast the car must have been going at the beginning of the skid. An expert can accomplish this with considerable accuracy, based on a knowledge of the physical principles that are involved, plus available information relating to the friction of tires on various types of road surfaces.

7/14/2009· Forensic Analysis

Slip and Fall Accidents

By: Kristopher J. Seluga, PE

Second to automobile accidents, accidents due to falls are the leading cause of injury and death. Of these, accidents due to slipping (not tripping) form a large proportion. Slipping may occur on floors, walkways, and stairs or steps. For Introductory purposes, however, the present discussion will be limited to slipping on flat surfaces such as a floor or sidewalk.

7/14/2009· Forensic Analysis

Analysis and Testing in Accident Reconstruction

By: Kristopher J. Seluga, PE

Persons with no training in engineering are generally unaware of the nature of engineering analysis, and so tend to assume that testing, as a means of determining the causation of accidents, is a dominant tool of the engineer. In the following examples, we shall undertake to explain the nature of engineering analysis, and to show that it is more basic than testing because testing without analysis is meaningless. Further, while analysis is always necessary in accident reconstruction, testing is only sometimes necessary.

7/14/2009· Human Factors

Industry Standards

By: Kristopher J. Seluga, PE

A standard can be defined as a document issued by a recognized agency, and dealing with design and/or safety requirements relating to a specific product or type of activity. Such agencies include the U.S. Occupational Safety and Health Administration (051-IA) and the American National Standards Institute (ANSI). OSHA standards are generally legally binding for an employer, while ANSI standards are generally of an advisory nature. The term "industry standard," however, is ordinarily taken to have a broader meaning, including formal standards as just defined, and also including designs and procedures not required in formal standards, though prevailing in a specific industry, and which represent generally accepted custom and practice.

7/14/2009· Forensic Analysis

Golf Car Hazards

By: Kristopher J. Seluga, PE

According to the Consumer Products Safety Commission (CPSC), there are approximately 10,000 golf car related injuries requiring emergency room treatment in the US each year. One significant mode of injury in golf car accidents is passenger ejection, which can lead to serious injuries, especially of the head. Based on CPSC statistics, roughly 35% of golf car accidents involve a person falling out of the car. In addition to ejection accidents, at least 10% of golf car accidents involve a rollover and statistics indicate that such accidents are roughly twice as likely to lead to injuries requiring a hospital stay as non-rollover accidents.

7/7/2009· Failure Analysis

Failure Analysis of a Broken Jam Jar

By: Dr. Thomas Read

Glass fractography is the most effective method for determining why a glass object, such as a bottle, failed. This technique consists of examining the fracture surfaces of the failure for artifacts such as Wallner lines and using them to trace the crack back to its origin. Once the origin has been identified, it can be examined in detail with a microscope to determine the cause of the failure.

7/7/2009· Failure Analysis

Failure Analysis of a Failed Ceramic Water Holding Tank on a Toilet

By: Dr. Thomas Read

The cracked tank was first inspected in the "as received" condition. In this condition it was cracked, but it was still whole. Next, the failed tank was separated by pulling it apart. This was done to expose the fracture surfaces of the main crack. This allowed for a complete failure analysis and for a determination of where the crack initiated.