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Technical Paper

Accelerated Testing of Multi-Layer Steel Cylinder Head Gaskets

Accelerated testing techniques for cylinder head gaskets have become absolutely necessary because of developments at engine manufacturers including: shorter engine development times, high costs of vehicle and dynamometer testing, new material generations for engine components, and new engine generations and longer engine life This paper will describe two accelerated test methods for Multi-Layer Steel (MLS) cylinder head gaskets and will discuss the most important parameters which influence MLS cylinder head gasket functional performance. We will describe how these parameters have been duplicated in the laboratory using the accelerated tests: the Bending Simulator and the Hydraulic Pulsator. The test method results have been confirmed based on detailed metallurgical analysis of MLS gaskets; comparing field (dynamometer and vehicle) tested gaskets to those gaskets evaluated on accelerated tests.
Technical Paper

An Overview of Microalloyed Steels, Part I: Metallurgical Aspects

Microalloyed (MA) steels have been developed as one of the most significant metallurgical advances over the last thirty years, with their property improvement and cost effectiveness characteristics. Even though the underlying principles for microstructural property control of these steels have been well established, applications of these steels are still limited in scale mainly due to a lack of their understanding. This review paper focuses on mechanical property control of these steels. Since the properties depend mainly on the composition and microstructure which in turn are controlled by steel making and processing, metallurgical variables are reviewed in this first part of the review. These include their strengthening mechanisms, effects of composition and processing on their behavior, and the various MA steel microstructures.
Technical Paper

An Overview of Microalloyed Steels, Part II: Their Mechanical Behavior

Microalloyed (MA) steels have been developed as economical alternatives to the traditional quenched and tempered (QT) steels. The physical metallurgy principles underlying their basic composition-processing-microstructure-property interrelationships have been reviewed in the first part of the review. In this second part of the review, mechanical properties as well as fabrication properties, such as mahinability, weldability, and formability, are discussed. Flat products (such as strips, sheets, and plates), long products (including bars, rods, sections/profiles), and forging articles made of MA steels are investigated. Since most engineering components made of these steels are subjected to cyclic loading, fatigue and fracture performance of MA steels and their comparison with the QT steels are also evaluated in this review.
Technical Paper

Corrosion Fatigue Influence on Gasket Flange Cracking

This paper discusses corrosion fatigue and the corrosive environment as they relate to an industrial engine head gasket joint. The paper will identify possible corrosive elements which initiate corrosion fatigue failures. The sources of the corrosive elements will be cited with the associated concentration levels. The paper will formulate a hypothesis as to how the corrosive elements are transferred through the engine coolant system. Utilizing a Scanning Electron Microscope (SEM) and an Energy Dispersive X-ray Spectroscope (EDX), an analysis of coolant residue at the fracture will show evidence of the corrosive elements to verify the proposed hypothesis. Information from engines in the field will be compared to laboratory engine tests to show how laboratory and field results are significantly different. The main corrosive failure of the engine head gasket is flange cracking.
Technical Paper

Effects of Piston-Ring Dynamics on Ring/Groove Wear and Oil Consumption in a Diesel Engine

The wear patterns of the rings and grooves of a diesel engine were analyzed by using a ring dynamics/gas flow model and a ring-pack oil film thickness model. The analysis focused primarily on the contact pressure distribution on the ring sides and grooves as well as on the contact location on the ring running surfaces. Analysis was performed for both new and worn ring/groove profiles. Calculated results are consistent with the measured wear patterns. The effects of groove tilt and static twist on the development of wear patterns on the ring sides, grooves, and ring running surfaces were studied. Ring flutter was observed from the calculation and its effect on oil transport was discussed. Up-scraping of the top ring was studied by considering ring dynamic twist and piston tilt. This work shows that the models used have potential for providing practical guidance to optimizing the ring pack and ring grooves to control wear and reduce oil consumption.
Technical Paper

Microstructure and Mechanical Properties of Welded Thermoplastics

Thermoplastics have been used increasingly for automobile components for both interior and under-the-hood applications. The plastic parts are made through various molding process such as compression molding, injection molding and blow molding. For parts with large or complicated geometry, small portions of the part may have to be molded first, then joined together using a welding process. The welded regions usually exhibit inhomogeneous and inferior mechanical performance compared to the bulk regions due to the differences in thermal history. The microstructures and mechanical properties of welded thermoplastics have been examined using hot-plate welded polyethylene. The specimens are prepared at various thermal conditions to simulate the real welding process. The thermal properties in welds are monitored using DSC (Differential Scanning Calorimetry) and the crystallinities are calculated.
Technical Paper

Piston Ring Cylinder Liner Scuffing Phenomenon: Investigation, Simulation and Prevention

In spite of being a popular topic in technical publications, scuffing between piston ring face and cylinder liner is an extremely unpredictable and hard-to-reproduce phenomenon that significantly decreases engine performance. This paper will discuss results of metallurgical and metrological (post-mortem) examinations of the scuffing between hard and soft cylinder liners and different piston ring coatings after field, engine and bench testing. Detailed metallurgical analysis describes the lubricity mechanism between various piston ring coatings and iron cylinder liner at different temperatures with and without oil. The paper will explain the origin of the scuffing through lack of or inadequate lubrication at top dead center, particularly for hardened iron heavy-duty diesel cylinder liners.
Technical Paper

Quality and Productivity: An Answer to the Question

Who will repair the cars of the future? By the year 2001 there will be over 200 million vehicles registered in the United States. The closing of many new car dealerships and the reduction of service bays at oil companies are contributing to the decline of traditional service outlets to repair vehicles. Certain trends, however, are emerging that indicate that a shortage of auto repair technicians will not exist. Vehicles have been improved and maintenance schedules and warranties have been extended. The quality of the modern vehicle has impacted some traditional types of auto repair that used to be done. Rustproofing and engine tune-ups are just two such businesses. Factory rustproofing and the use of rust resistant materials have forced muffler shops and rustproofing businesses to change their repair focus. Tune-up services have changed to engine performance services because of the change in vehicle technology.
Technical Paper

Rapid Prototyping Shortens Hydraulic Component Development Time

A few years ago hydraulic fluid power component manufacturers had the luxury of long lead times to develop new products. In today's competitive global market, pump and valve design engineers must be able to shorten development lead times and get new, less costly products to production in order to satisfy customer demands. This paper describes how one fluid power component manufacturer uses rapid prototyping technology to speed up the development cycle by making: fit and form models, design evaluation test samples, and tooling for prototype castings.
Technical Paper

Spatial Transmissibility of Plastic Cylinder-Head Covers

The transmissibility technique has been traditionally used for evaluating the NVH performance of isolated, rigid structures such as the elastomer mount isolated automobile engine. The transmissibility quantity provides information on how a structure reduces vibration as subjected to dynamic loading and thereby attenuates noise. In the present study, the transmissibility is applied to a non-rigid, plastic structure - the engine cylinder-head cover module. The cover module includes primarily a thin, plate-like cover and the elastomer isolation system. At low frequencies, the cover will behave as a rigid mass and thus display a major peak at its resonant frequency. At high frequencies, the cover will vibrate as a flexible panel and thus display multiple peaks with magnitudes differing from point to point across the cover surface. As a result, the transmissibility calculated would have a spatial resolution, called the spatial transmissibility.
Technical Paper

Variability of Test Specimens Used for Evaluating Light Duty Automotive Filter Seal Materials

Quality control and materials development of cellular polyurethane foam used in light-duty automotive air filter seals rely on measurement of mechanical and physical properties such as tensile strength, elongation, compression set, specific gravity, and durometer hardness. These properties are typically measured on specimens cut from slabs formed in preheated closed molds. However, these slabs are nonuniform in specific gravity, and property measurements vary with location within a slab. The effect of sampling location on mechanical and physical properties is discussed.