character analysis of cylinder head

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CHARACTER ANALYSIS OF CLINDERR HEAD

APPLICATION

The Cylinder Head of an internal combustion engine is a solid block that rests on the main

body(encompassin the piston).The Function of the cylinder head is to provide for a passage to

the charge i.e the intake and exhust valve ports and valve seats and the exhaust gases as well

as to provide a closed surrounding for the combustion cycle to take place.

SERVICE CONDITIONS

Cylinder heads while in operation are subjected to very high pressures.Contolled explosion of

fuel takes place inside the chamber.Hence these are subjected to tmperature stresses.

REQUIRED PROPERTIES

While slecting a material for clynder head maufacture the following properties have to be

verified:



y Resistance to mechanical shocks.

y Thermal conductivity

MATERIAL CHOICES

Aluminum and cast iron alloys are used as cylinderhead materials because of the excellent

casting properties.

Because of the mechanical and thermal requirementsAl-Si-alloys and increasingly cast irons

with vermicular graphite (GJV) are used for this engine component. High thermal conductivity,

low thermal expansion and high tension/compression strength leadto a good thermal

behaviour. Cast irons are used in heavy goods vehicles because of the higher requirements in

the strength. For light weight construction requirements Al-Si-alloys are taken by the

automotive engineer, even though these alloys are more expensive.

PROCESSING CHOICESCylinder heads are relatively large in size and the molds used for casting them feature

complicated core shapes. Traditionally, cylinder heads and similarly complicated castings have

been produced by manufacturing wooden patterns that model the shape of the required

product, creating sandmolds which are the inverse of the wooden patterns, combining these to

form a casting cavity, and finally pouring aluminum or some other molten metal into this cavity

to produce the required casting. Creation of wooden patterns in this process requires a

considerable amount of time as it involves time-consuming jobs such as designing casting plans

and making wooden pattern manufacturing data. In recent years, machinery manufacturers

have market- released a wide variety of rapid prototyping machines which use three-

dimensional, computer-aided design data in the creation of the models, and these machines

are being put to use in the field of electrical appliances to make resin case prototypes and, in

the field of automobiles, to create models of small resin components in order that development

periods may be shortened.

Further the port cavity has to be made by the use of a special Porting tool.The surface finish is

generally done by machines as the valves require a very minute clearance.

Porting and grinding CNC



COST AND AVAILABILITYCast iron is easier to obtain from pig iron.Also the main ore being ferritic compounds are

readily available near the earths crust.Hence cast iron is relatively cheaper than majority

materials.Aluminium on the other hand requires costly extraction process and its ore bauxite is

difficult to mine.Hence out of the two Cast iron is readily available and cheaper too.

FINAL SELECTION

Cast iron cylinder heads offer the benefit of being inexpensive, durable. Cast iron headsare also heavy, less forgiving of high compression ratios, and more expensive to port. Aluminum cylinder heads have the advantage of being lightweight (generally 50% or less of the weight of a comparable iron head), repairable, easier (which translates to ³cheaper´) toport, and more forgiving of high compression ratios. Disadvantages to aluminum headsinclude cost (compared to iron heads), the need to pay close attention to proper fastenertightening procedures to avoid thread damage, and issues of valve lash and otheradjustments that may be effected by the fact that aluminum expands quite a bit more thaniron when your engine reaches its normal operating temperature. Which is the best to use depends largely on your application, and which properties of thetwo materials best suit your needs.

character analysis of cylinder head

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