Pearlitic flake-graphite grey cast irons have long been widely used for the manufacture of diesel-engine combustion-chamber components. Nonetheless, very few pertinent high-temperature data are to be found in published work. The investigation described attempts to enlarge current knowledge on the high-temperature behaviour of grey cast irons in view of requirements highlighted by high thermal ratings. A general consideration of the problem showed that the often quoted Eichelberg material-quality factor is largely irrelevant and an alternative assessment formula is proposed. This is broadly confirmed by a systematic examination of the mechanical and physical properties of 166 plain and alloyed cast irons and a limited number of engine components.Different engine components impose different demands upon the material properties but for economic reasons a single cast-iron melt capable of meeting most of the requirements of all components is needed. It is shown that this situation is best met with an alloyed iron containing 1.3 per cent of copper-nickel and 0.4 per cent of molybdenum. The scatter in properties obtained from production casts was found to be typical for such irons. For components having safety factors of 2 or less, a prerequisite of economic engineering design, the service reliability is crucially dependent upon the scatter of material properties. Thus, there are advantages in reducing this scatter and it is shown that this can be achieved by attention to the cleanliness of the matrix and tight control of the chemistry of the melt.In general, the absolute values of mechanical and physical properties of flake-graphite cast irons appear to be governed mainly by the form and size of the graphite flakes and the chemistry of the matrix (i.e. CEV and alloying additions). Regression analysis of the results permitted the derivation of empirical formulae for the prediction of the iron properties. The general findings are used to suggest possible ways of improving the thermal resistance. Downloaded from f,, = aG+bS,+Kp+2K, . . (12) where G is the graphite-flake ASTM size, S, the carbon saturation value, a and b constants characteristic of the foundry methods, K, a constant determined by the degree of pearlite refinement, and K, contributions from the J O U R N A L O F S T R A I N A N A L Y S I S V O L 5 N O 2 I970 3
This paper is restricted to a review of the work carried out in order to develop a strain gauge capable of operating at temperatures up to 1000°C with an inherent accuracy of ±5 per cent. A large number of resistance alloys were tested as unbonded long wires at room temperature and, from the results obtained, a small number were selected for further investigation, in the form of gauges, at high temperatures. The effects of factors such as metallurgical changes, geometric shape and long-term exposure on the behaviour of the gauges were investigated. A number of bonding mediums, some commercially available, were examined with particular reference to creep under load, shear strength and resistance to erosion and thermal shock. Finally some preliminary tests in conjunction with the measurement of steady strains at elevated temperatures were undertaken. It is concluded that the gauge factor is a function of the lattice imperfections of the element wire and, as such, will be temperature-conscious only if the imperfections themselves are affected by temperature variations. In general, any factor affecting the resistivity will affect the sensitivity. The most significant result obtained during the work described is that the gauge factor may be predicted within ±5 per cent at any given temperature, provided certain precautions are observed. Some typical failures under field conditions are discussed as also are the possibilities of operating for protracted periods under steady stress conditions. More stringent requirements for future applications suggest that the wire gauge will be unsuitable, in view of its low resistance in very small sizes, and a possible alternative is briefly outlined.
British automotive design philosophies, engineering traditions, organizational structures and managerial practices have been geared to the generally recognizable European product concept. This distinctiveness has been eroding due to the convergence of Japanese and North American trends towards European values. Regaining the competitive edge has become the challenge facing the industry. The present paper describes a determined attempt to do so. Earlier investigations had shown that, in automotive engineering, the attainment of customer-perceived superb ‘quality’ was the only assurance of market acceptability and competitiveness. Traditional design methodologies were demonstrated as inadequate and incapable of ensuring the attainment of product attributes in line with end-user needs and expectations. The subsequent evaluation of an alternative design logic indicated the need for a reappraisal of the engineering culture. The organizational, managerial and operational changes necessary to implement this new philosophy are described in detail. A preliminary quantification of the benefits reaped are presented. Scope for further improvement is shown to exist. Although the transition was broadly successful, different areas showed different rates of progress. This highlighted the need for a commonality of ethos, objectives, goals and understanding by all. Apprehension and discomfort was encountered at all levels, but was particularly evident among middle management. This underlined the importance of mutual trust, good communications and appropriate training. The continuing evolution of the automotive industry and the pressing challenge of competition will force ongoing changes in engineering organizations to meet new market needs. The likely directions of such changes in the management of automotive engineering work are outlined.
The paper reviews the main requirements fulfilled by a cylinder head or cylinder block and outlines the common modes of failure met with in practice. The relative importance of the various loads applied to the head in operation are assessed and a method of predicting their influence on the structural integrity of the component described. The theoretical results obtained from a range of cylinder heads covering engines in the bore range 4 3/8 in (110 mm) to 17 in (430 mm) are shown and the experimental data obtained from verification tests presented. A quick design-assessment criterion is derived and the design-optimization procedure evolved is discussed. It is concluded that on highly rated engines the critical section is usually located at the narrow flame-plate section between adjacent exhaust-valve ports. Failures are mainly due to thermal overload. The cylinder head's rating can be extended by reducing the bottom-deck temperatures and the axial stiffness of the head and by adopting more advantageous materials for the bottom deck. Typical examples are illustrated.
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