Search Results

Cavitation is the dynamic process of gas cavity growth and collapse in a liquid. These cavities are due to the presence of dissolved gases or volatile liquids and they are formed at the point where the pressure is less than the saturation pressure of the gas (gaseous cavitation) or vapor pressure (vaporous cavitation). In this paper, various hydraulic system design factors and fluid properties affecting the cavitation process, and bubble collapse mechanisms will be discussed. In-situ generation of cavitation, examination of the cavitation process in model hydraulic systems, material effects and test methods will be reviewed.

Thermal distortions of friction disks caused by frictional heating modify pressure distribution on friction surfaces. Pressure distribution, in turn, determines distribution of generated frictional heat. These interdependencies create a complex thermoelastic system that, under some conditions, may become unstable and may lead to severe pressure concentrations with very high local temperature and stress. The phenomenon is responsible for many common thermal failure modes of friction elements and is known as frictionally excited thermoelastic instability (TEI). In the paper, one of the cases of TEI is investigated theoretically and experimentally. The study involves a two-disk structure with one fiction disk and one matching steel disk that have one friction interface. An unsteady heat conduction problem and an elastic contact problem are modeled as axisymmetric ones and are solved using the finite element method.

This paper concerns the analysis of data for cases where there are NO occurrences of “failures” when there is reason to assume a Weibull distribution with known slope parameter for the characteristic being studied. All samples survive a time t in an unfailed condition. In a series of n independent tests conducted under similar conditions, if we observe no failures by time t we call this a “success” run of length n. In this paper the classical non-parametric success run is first reviewed and it is shown what can be said about the relationship among reliability, confidence and sample size. Next, the Weibull distribution is explored for modeling the success run test when it is reasonable to assume a value for the Weibull slope parameter, b.

The excellent anti-wear (AW) and oxidation inhibition properties of Zinc Dialkyl Dithio Phosphates (ZDDPs) have resulted in their extensive use in modern AW hydraulic oils. However, increasingly compact hydraulic systems utilizing high service-pressure pumps (>300kg/cm2), has lead to operating temperatures (>250°C) that have been shown to thermally degrade ZDDP into insoluble sludge [1]. This paper chronicles the development of a non-ZDDP AW hydraulic oil, and evaluates its performance relative to a ZDDP oil in the areas of sludge generation, oxidation, and AW properties. The formulation reduces sludge by 85 to 99.5%; retains more viscosity; reduces metal wear by 04-06%; and extends useful service life to at least twice that of the ZDDP-based hydraulic oil.

This paper describes the development and manufacture of roll-off container handling systems for off-highway articulated trucks. This presentation reviews systems incorporating four unique products covering various roll-off container handling alternatives. The various components described and, depending on the style of the system, incorporated into a system are: 1. An off-highway truck “J”-Hook arrangement for picking roll-off containers up off of the ground and pulling them onto a haulage vehicle. 2. An automatic tailgate locking and opening system for roll-off containers vs. a manual vehicle driver dependent door/tailgate system. 3. A scissors lift for lifting roll-off containers to be dumped into various other vessels (railroad gondola cars, etc.). 4. A unique “J”-Hook interface for standard 20-ft. intermodal roll-off shipping containers so they can be hooked onto and handled with a “J”-Hook.

The application of open-circuit, load-sensing hydraulic systems in industrial, marine, and mobile equipment has long provided many advantages to machine designers, manufacturers, distributors, dealers, and end-user customers. Typically, the flow for such systems is provided by variable-displacement piston or vane pumps. However, in some applications, fixed-displacement gear pumps with integral load-sensing valve packages offer a more economical, and (depending on machine duty cycle and other parameters) a more efficient system. This paper will provide an overview of the design and advantages of these units, discuss the essential criteria which must be considered during the “fixed-displacement versus variable-displacement” pump selection process, and describe some typical applications.

As a means of lowering greenhouse gas emissions, increasing economic growth, and reducing the dependency on imported oil, the Department of Energy and Brookhaven National Laboratory (DOE/BNL) is promoting the substitution of liquefied natural gas (LNG) in heavy-vehicles that are currently being fueled by diesel. Heavy vehicles are defined as Class 7 & 8 trucks (> 118,000 pounds GVW), and transit buses that have a fuel usage greater than 10,000 gallons per year and driving range of more than 300 miles. The key in making LNG market-competitive with all types of diesel fuels is in improving energy efficiency and reducing costs of LNG technologies through systems integration. This paper integrates together the three LNG technologies of: (1) production from landfills and remote well sites; (2) cryogenic fuel delivery systems; and (3) state-of-the-art storage tank and refueling facilities, with market end-use strategies.

A dedicated closed-loop propane fuel system has been developed for the General Motors Medium Duty truck with a 7.4 liter engine. The fuel metering system consists of a closed-loop controlled regulator and mixer. Regulator output pressure is controlled by a pulse-width modulated vacuum signal from the mixer for off-idle operation. Idle fuel is provided by an electronically controlled, fuel metering solenoid valve. Additionally, original equipment manufacturer (OEM) fail-safe performance of the Electronic Throttle Control system has also been achieved. This fuel system is an example of how an open loop regulator-mixer system can be enhanced with electronic controls to achieve significant improvements in emission signature, driveability, and customer satisfaction.

Heavy-duty vehicles account for approximately 30 percent of the oxides of nitrogen (NOx) and 65 percent of the particulate matter (PM) emissions from the entire California on-road fleet, despite the fact that these vehicles comprise only 2 percent of the same. To meet legislative mandates to reduce excess smoke emissions from in-use heavy-duty diesel-powered vehicles, the Air Resources Board (ARB or Board) adopted, in December 1997, amendments to the regulations governing the operation and enforcement of the Heavy-Duty Vehicle Inspection Program (HDVIP or the “roadside” program) and the Periodic Smoke Inspection Program (PSIP or the “fleet” program). The initial roadside program was adopted in November 1990 in response to Senate Bill (SB) 1997 (stat. 1988, ch. 1544, Presley), and enforced from 1991 to 1993. It was suspended in October 1993, when the Board redirected staff to investigate reformulated fuels issues.

The objective of this project, which is supported by the U.S. Department of Energy (DOE) through the National Renewable Energy Laboratory (NREL), is to provide a comprehensive comparison of heavy-duty trucks operating on alternative fuels and diesel fuel. Data collection from up to eight sites is planned. This paper summarizes the design of the project and early results from the first two sites. Data collection is planned for operations, maintenance, truck system descriptions, emissions, duty cycle, safety incidents, and capital costs and operating costs associated with the use of alternative fuels in trucking.

Cast structures offer significant potential for weight reduction by applying numerical optimization methods. However, optimization techniques have been rarely used by industry in these applications because of either the large computational resources required or the extensive time required to set up the optimizations. Improvements in topological optimization and faster computers have overcome some of these problems. This paper shows some examples of recent optimization studies as applied to cast structures. Topological optimization studies are performed using ANSYS finite element software. Sizing optimization studies were performed with MSC/NASTRAN software. These studies have shown that optimization can be effectively applied to solid structures, assuming that the critical loads can be modeled with linear analyses.

Finite element models were developed and used to predict springback and residual stresses in a solid plate due to bending. This paper presents the modeling issues that were involved in the development of the optimum finite element tool and discusses the effects of the different input parameters on springback. A sensitivity analysis concluded that the springback depended on the bent angle as well as other various parameters such as tool and die geometry, part geometry, material characteristics, and the pre-bending residual stresses. A “probabilistic” approach was taken to determine the sensitivity of the model to the above mentioned parameters. The results of preliminary validation of springback are also presented.

Understanding the main effects and interactions of welding process variables on the weld nugget is essential to weld quality. A structured experiment was performed to investigate the effects of primary process variables on the weld nugget geometry. The weld chosen to model in this study was a flat fillet, welded in spray transfer with .052” ER70S-3 and a shielding gas of 90% Argon-l 0%CO2.

The growing use of laser processing within the automotive industry has generated interest in applying laser welding, cutting and surfacing to structures commonly used in off-road vehicle manufacture. The perceived benefits of applying laser welding technology are to reduce structural distortion, increase joint production rates, allow more accurate structures to be produced and enable mechanisation and automation. This paper will review the current status of high power laser technology, including CO2 and Nd:YAG lasers. The application of high power lasers to materials relevant to the fabrication of off-road vehicles will be presented covering details of joint design, joint quality, joint performance, quality assurance and economics.

In this paper hydraulic system of a modern forest machine, different types of biodegradable hydraulic fluids and the use of biodegradable hydraulic fluids in Timberjack forest machines are described. Today there is a wide variety of biodegradable hydraulic fluids in the market. These hydraulic fluids must meet the biodegradability requirements and also the functional requirements from component manufacturers and machine manufacturers. It is a difficult task to select the right fluid for different applications and operating conditions. Many times selection is based on experience.

Technical groups worldwide have been actively developing specifications and requirements for biodegradable hydraulic fluids for mobile applications. These groups have recognized that an industry-wide specification is necessary due to the increase in environmental awareness in the agriculture, construction, forestry, and mining industries, and to the increasing number of local regulations primarily throughout Europe. Caterpillar has responded to this need by publishing a requirement, Caterpillar BF-1, that may be used by Caterpillar dealers, customers, and industry to help select high-performance biodegradable hydraulic fluids. This requirement was written with the input of several organizations that are known to be involved with the development of similar types of specifications and requirements.

The fatigue performance of fillet-welded transverse attachments was compared for several procedure variants for both FCAW and SAW on ½ in. steel plates. Measurements of weld toe shape on adjacent pieces of weld indicated that smoother weld toes, as evidenced by larger weld toe radius, were correlated to improved fatigue performance for both processes. Fatigue tests conducted on 59 and 109 ksi yield strength plates did not show an effect of plate strength. Weld procedures designed to provide smooth toes, such as reduced parameter FCAW beads at horizontal weld toes and flat position FCAW at higher heat inputs, were shown to provide fatigue performances near post-weld improved fillets.

An important emerging technical area is computer-based modeling of the various manufacturing processes that are used in many diverse industries. These models are used to optimize manufacturing techniques to reduce fabrication costs and improve the service performance. One manufacturing process important in steel fabrication is welding. It can be a useful tool to aid in reducing fabrication costs and service durability by optimizing the weld process and is the subject of this paper.

In the early 1990's, the Standards and Data Services Committee (SDSC) of the American National Standards Institute (ANSI) saw the need for a national standards system network that would allow users to identify and obtain the standards documents necessary for their work. From this initial concept the NSSN has grown to become a comprehensive source for standards information on the World Wide Web. This paper will briefly provide the history of the NSSN; describe the current services available; and discuss the current development direction for the service.

Engineering new technology and products challenges managers to balance design innovation and program risk. To do this, managers need methods to judge future results to avoid program and product disasters. Besides the traditional prediction tools of schedule, simulations and “iron tests”, process control standards (with measurements) can also be applied to the development programs to mitigate risks. This paper briefly discusses the theory and case history behind some new process control methods and standards currently in place at Caterpillar's Electrical & Electronics department. Process standards reviewed in this paper include process mapping, ISO9001, process controls, and process improvement models (e.g. SEI's CMMs.)