Search Results

Recent developments in a NIST sponsored program on Design, Non-Destructive Evaluation and the Manufacturing Sciences (being conducted at Iowa State and Northwestern Universities) have led to the realization of a new paradigm for the design of safety critical components made by metal casting. The paradigm is based on the simultaneous integration of design for casting, design for fatigue performance and design for inspection. In a concurrent environment, foundry process simulation is used to predict an array of porosity related defects in the subject casting. The probability of detection of these defects is investigated with a radiographic inspection simulation tool (XRSIM). The likelihood that the predicted array of defects will lead to a failure is determined by a fatigue crack growth simulation. When properly utilized, this kind of system gives visibility to casting manufacturing, performance, and inspectability issues during the earliest stages of product definition.

The occurrence of porosity during metal solidification is one of the major issues that impact the quality of castings. Quantitative information on the development of porosity is particularly important for safety critical components, such as automotive chassis parts and airframe primary structures. In this paper, we present two approaches to predict the location and volume fraction of porosity for aluminum alloy A356. In the first approach, the application of Neural Networks to predict porosity is examined. Results are compared with the established criteria functions and reported experimental findings. Neural Networks are shown to predict the occurrence of porosity with higher confidence than the existing thermal parameter based criteria functions. In the second approach, microporosity evolution is modeled mathematically.

Ryobi Outdoor Products (ROP) in Arizona, one of the subsidiaries of Ryobi Group of companies, developed 26.2cc OHV engine for string trimmers. (2) The outline of the valve train of this engine was presented at the SAE conference at Indianapolis 1996.(3) This paper describes methodologies and theoretical considerations by which such a unique valve train was developed. The theoretical consideration includes how optimize the valve train design to minimize the moving mass as a total system. Methodology for optimizing the design of each component of valve train is also presented. A review of how the theoretical optimization was translated into the final production engine design is given. The experimental effort to optimize cylinder head design to make the overall optimized design theory reality is described.

This paper reviews the emissions reduction program that was pursued during the development of the small 26.2 cc, OHV, 4-cycle engine recently introduced by the Ryobi Group of Companies. This new engine's packaging and power density is designed to compete directly with pervasive, hand held, two-stroke power plants. The 4-cycle OHV design produces substantially less HC and CO emissions relative to the existing two stroke state-of-the-art hand held power plant. The challenge of minimizing NOx emission however is complicated by the practical limitations of low cost, diaphragm carburetor fuel metering systems. The levels of NOx emitted by the production engine are controlled by a careful manipulation of combustion chamber design, compression ratio, spark ignition timing, and internal and external exhaust gas recirculation. The results of experimental evaluations used to achieve a 1999 CARB standard capable design are discussed.

This paper outlines the design and construction of a small 26.2 cc overhead valve, 4-cycle engine recently developed by the Ryobi Group of Companies for hand held power equipment applications. Four cycle engines produce fewer hydrocarbon emissions and typically generate better low end torque than the commonly used two cycle. In order to displace the high power density two-stroke technology however, a four cycle design must be cost and performance competitive. Additionally, the engine must be durable and functional at operating speeds in excess of 8,500 r.p.m. The Design for Manufacturability and Design for Assembly methodology used to create the individual powertrain components and subsystems for the new, lightweight power plant to meet the desired cost, performance, and packaging objectives is reviewed.

This paper outlines the specifics of valve train design and construction for a small 26.2 cc, OHV, 4-cycle engine recently developed by the Ryobi Group of Companies for hand held power equipment applications. The first generation of this engine was designed to compete with existing 2-cycle technology for nylon string trimmers. As such, the valve train operates reliably at engine speeds in excess of 8,500 r.p.m. Design methodologies to minimize forces that develop during high speed operation will be reviewed. The lifter mechanism design facilitates parametric tuning of engine performance by simple variations in the geometry. A unique combination of nickel free stainless steel valve and polymeric valve spring retainer materials were used to avoid wear in the valve stem and limit valve float in a single spring design.

The horizontally opposed family of engines manufactured by Fuji Heavy Industries in Japan have been mass produced with a variety of cylinder block designs and Aluminum alloy casting techniques. These include closed deck configurations by a semi-permanent mold or low pressure casting technique, open deck configurations by a high pressure diecasting method, and both open and closed deck configurations by a hybrid medium pressure casting process. In this paper we review our experience with each production process/engine design combination. Special attention is paid to cylinder liner technology, coring methods applied to form the water jacket, oil galleries and other cavities, overall casting productivity and the contribution of casting design to end product performance.