Trencher: Impingement on Buried Objects

There is a resemblance between the digging chain of a trencher and the folklore chain saw. The safety of trenchers requires that the similarities and differences between these two machines be understood so that appropriate warning signs can be formulated. There is a notion that the trencher can be suddenly thrust rearward in the direction of the digging chain in the manner associated with the chain saw. There is also a notion that the kickback characteristic of the chain saw is also characteristic of a trencher digging chain. This paper shows that these rearward thrust and kickback notions for the trencher are false. On the other hand, contact with moving teeth is hazardous on either machine.

Ladder Slide Out: First Order Analysis

One of the more important collapse modes for straight, combination, and extension ladders is base slide out; the top of the ladder slides down the support wall as the base slips away from it. Various fundamental models have been used to study this behavior. This paper revisits the analytical solutions associated with these models and describes their implications for the analysis, design, and testing of ladders.

Application of the Physics of Failure Approach to Reliability Prediction for Design Guidance of Commercial Appliance Components

The physics of failure approach to reliability prediction considers fundamental failure mechanisms such as fatigue, wear, corrosion and creep that can shorten the useful life of a product. The work described here uses this approach for commercial appliance components and presents three examples. This paper also outlines a methodology for developing rate modification factors. These rate modification factors can be used for evaluating design changes, early estimation of failure rates, planning accelerated life tests and assessing risks in component application alternatives. Although the physics of failure approach is not new, the application to relatively inexpensive light service commercially based components extends the application beyond the realm of military and heavy industrial equipment. Simplifying assumptions and the use of manufacturer’s material properties are utilized to create a “cookbook” approach for development of design charts useful for improving product reliability. The principal objective of the work presented here is to demonstrate the development of the design charts and their application to commercially based products.

Removal of Cadmium From Contaminated Water

Over the past 15 years, about one half million sites with potential contamination have been reported to federal or state authorities. Of these, about 217,000 sites still need remediation (1) and new contaminated sites continue to appear each year. The most common type of contaminants are metals, solvents and petroleum products. Heavy metals are present in two thirds of DOD and superfund sites and about 50% of DOE and RCRA sites. AAM is a new material that possesses the ability to remove heavy metal from conaminated water. AAM consists of fly ash activating chemicals and fillers. AAM barrier material was used to remove Cd from contamination water. Fly ash from three different sources were used to produce reactive barrier of different permeability. AAM materials with permeability 10−2 to 10−1 was created. Only highest permeability proved to be viable for reactive barrier material. AAM barrier from three ash sources with permeability of 10−1 was produced and crushed into pelletized form. To determine effectiveness of the various barriers batch test was performed, based on that result the column test was conducted. In this work contamination barrier with controled permeabilty was tested to determine its ability to remove Cd from contaminated water. AAM barrier material was used in column test to remove Cd from 1000 ppm and 10 ppm solution. The results show that AAM barrier is very effective in removing Cd from highly contaminated water (up 99% efficiency).

Accumulator Roll Analysis Using the Finite Element Method

The purpose of this study was to develop a method to analyze various designs of non-driven accumulator rolls using a static finite element software package. This would allow the engineer to determine how the various components of the roll design contribute to or lessen the deflection of and stresses in the roll body when it is loaded by sheet metal passing over o under it. The method outlined is intended mainly for use when an advanced dynamic finite element package that incorporates contact elements is not available and when a comparison of various roll designs is desired. First, an approximation of the pressure on the roll body caused by the force of the sheet metal as it wrapped over or under the roll was determined. Then using the finite element package ALGOR, an FEA model of a standard accumulator roll design was loaded with this pressure and the stresses and deflections were calculated. Next, components of this basic roll design were varied in the FEA model. These were the location of the stiffeners and the thickness of the roll body, the end plates, and the stiffeners. A comparative approach was then used to assess the impact each of these variations in roll design had oh the deflection of and the stresses in the roll.

The Design of a Universal Autonomous Power Tray

Several accessories have been developed to aid the wheelchair-confined individual in retaining their social independence. However, after a comprehensive study it was determined that a device, which would automatically extend the immediate reach of the handicapped individual, could not be easily added to such currently existing wheelchairs. We proposed a device that could easily be attached to the back of the electric wheelchair. This unit contains all necessary hardware to support the movement of an actuating arm whose intent is to automatically deliver and retrieve objects outside the person’s immediate reach. In addition, the unit does not significantly exceed the dimensions of the chair so as to not obstruct its normal use. To maximize our efforts, we re-evaluated the creativity of its construction: This was done to optimize its durability, reliability, and ultimately lower its construction cost. The ease of its manufacturing supports our intent for a universal application so that all handicapped individuals could benefit from this device as an after-market electric wheelchair accessory. Achieving these types of functions required the development of two pneumatic telescoping arms that can match and overcome its maximum load of 15 lb., and an electrical control system that both develops arid defines all object motions. A comprehensive static and dynamic analysis was performed to, determine the forces governing the motion of the arm as well as to predict its operating speed and direction. This analysis also tests the boundaries of our control system. This information allowed us to determine the range and limitations that defined the electrical as well as mechanical components of this system.

Minimally Invasive Suturing Device

The design of an intracorpeal suturing device that will assist surgeons in placing an internal suture through a small incision. Performing surgical procedures through a small incision greatly reduces patient trauma and rehabilitation time, both of which are proportionally related to medical costs. Medical devices exists today that allow surgeons to perform procedures through small incisions, unfortunately, it is difficult to place sutures deep in the body using minimally invasive techniques. A device that enables surgeons to place sutures minimally invasively will facilitate surgeons by increasing the scope of procedures that can be preformed using this technique.

Removal of Chromium From Contaminated Water

Over the past 15 years, about one half million sites with potential contamination have been reported to federal or state authorities. Of these, about 217,000 sites still need remediation (1) and new contaminated sites continue to appear each year. The most common type of contaminants are metals, solvents and petroleum products. Heavy metals are present in two thirds of DOD and superfund sites and about 50% of DOE and RCRA sites. AAM is a new material that possesses the ability to remove heavy metal from conaminated water. AAM consists of fly ash activating chemicals and fillers. AAM barrier material was used to remove Cr from contamination water. Fly ash from three different sources were used to produce reactive barrier of different permeability. AAM materials with permeability 10−2 to 10−1 was created. Only highest permeability proved to be viable for reactive barrier material. AAM barrier from three ash sources with permeability of 10−1 was produced and crushed into pelletized form. To determine effectiveness of the various barriers batch test was performed, based on that result the column test was conducted. In this work contamination barrier with controled permeabilty was tested to determine its ability to remove Cr from contaminated water. AAM barrier material was used in column test to remove Cr from 1000 ppm and 10 ppm solution. The results show that AAM barrier is very effective in removing Cr from highly contaminated water (up 99% efficiency).

Commercial Walk-Behind Lawn Mower Failure Analysis Case Study

A failure modes and effects testing program was conducted to analyze the cause of a mid-size commercial walk-behind lawn mower accident in which the operator’s foot came in contact with the rotating blade. Systematic analysis showed that the accident was caused by improper mower service and operator misuse of the mower. Testing results reveal that an alternative design proposal does not preclude this random event. Accident prevention countermeasures are explored.

Vehicle Lifts: The Hyperstatic Problem

Occasionally, vehicles topple off of structurally sound automobile lifts, even when they are properly supported at their lift points. This happens with a family of lifts that use four arms to position lifting pads under the vehicle chassis. The arms operate in a horizontal plane and are positioned by swinging and telescoping. Gravity loading of the pads and the attendant horizontal friction resistance cannot be relied upon to maintain the set-up position of the pads. There is a non-obvious structural phenomena called hyperstatic behavior that may easily lead to minimal, or even zero, pad loading with the attendant loss of resistance to horizontal pad movement. Unless otherwise restrained, the bumping and jostling associated with vehicle maintenance can produce random forces that will push a pad from beneath the vehicle. The resulting three-point support almost always leads to toppling of the vehicle from the lift.