Operational Requirements And Service Conditions Of Piston Engineering Essay

Operational Requirements And Service Conditions Of Piston Engineering EssayABSTRACTThere is an bound in changing the tr blockade of the secular by its properties and its characteristic. The majority of the worldlys completely depend on the application of the material in the compvirtuosont and its versatility. The elements by material vary from each other by its properties. The materials attain the tendency to change its manufacturing mental process by its character. A element can be make by using divers(a) materials depending according to the application and its life sentence. In this report we discussed about the manufacturing process of the components manage piston, connecting celestial pole and the crank shaft. The alternative methodologies and usage of alternative materials ar also explained by using CES chart with its advantages.INTRODUCTIONSelecting the appropriate material is an total go against of the successful implementation of an railway locomotiveers desi gn. A design engineers ability to objectively quantify the combined marketing, technical and manufacturing requirements as they apply to the material selection is critical to the actual as well as the perceived success of the product. This paper contains a deep knowledge about the selection of the material and its manufacturing procedure with justification.CHAPTER 1 GENERAL COMPONENT DETAILS1.1 PISTONThe piston is the most native component of the engine which actually transfer the energy output from the combustion chamber to the crankshaft through connecting rod. This is a pressure-tight cylindrical plunger which is subjected to the expanding gas pressure. Basically, piston geomorphologic components ar head, skirt, gudgeon pin, grooves and lands.1.1.1 OPERATIONAL REQUIREMENTS AND SERVICE CONDITIONS OF PISTONHence in order to transmit this advanced power output the piston must be designed swingingly and must be robust. The piston must be of higher persuasiveness material that can with stand the high pressure that is been generated out-of-pocket to the burning of air-fuel mixture within the cylinder. Piston must be fitted properly to control the expansion due to temperature, without which the piston will fit loosely when in cold and they bind themselves when it gets warmed.1.1.2 FUNCTIONS OF PISTONTransmit energy from combustion unit to piston pin,Serve as a carrier for the piston ring which seals the coalition in the cylinder,Act as a guide for upper end of the connecting rod,Withstand high temperature expansionDespite the genus Oestrus energy to the coolant.piston.gifFig(1) Piston manufacturingConditions of piston at normally high speed,Piston moves from the top to bottom of the cylinder and vice versa with a acceleration of speed of around 50mph at essence and decelerates.The piston is subjected to pressure of about 6.8MPA.The piston is subjected to temperature of about 315C.11.1.3 DESIRABLE MATERIAL CHARACTERISTICSThe Piston materials must meet the following conditions, 2Low thermic expansions for arresting the voluptuous gases. spirited thermal conductivity for releasing heating plant from piston head.High strong point to mass ratio (light weight) for transmitting high power output.High pall thin forcefulness for increasing the material strength.Good opponent to surface abrasion.To humble skirt and ring groove wear.1.2 CONNECTING RODConnecting rod is a part of the engine which connects the piston to the crankshaft. This connecting rod converts the linear work of the piston to rotating motion to the crankshaft.1.2.1 OPERATIONAL REQUIREMENTS AND SERVICE CONDITIONS Connecting rods should be made as long as possible to reduce the oblique angle by the cylinder axis.Both tensile and compressive at a lower placescorees are produced due to piston reciprocating-inertia stretch alongs.In order to evade scuffing proper lubrication is needed. Lubrication of the slight end by a hole drilled along the shank should be so ar ranged that the hole intersects the big end bore circumferentially.To prevent buckling the rod shank is made in an H section, i.e., with a central web and two end flanges.Intense heat is generated at high rotational speed, so large military strength area is required to make the rod wear well.They should be checked for the correct length, weight distribution, straightness and freedom from twist.1.2.2 FUNCTIONS OF CONNECTING RODAs the word is self explanatory, the connecting rod connects the piston and the crankshaft.The connecting rod continuously transmits energy from the combustion chamber to the crank shaft.It actually converts the reciprocating motion of the piston to the rotary motion of the crankshaft.These dynamic motions of the connecting rod makes it as light as possible whilst having a rigid section.14900_19847.jpg1.2.3 DESIRABLES MATERIAL CONDITIONSMust be strong to remain rigid to a lower place loading and light enough to reduce the inertia forces.Material must have goo d elastic modulus.It must have high fatigue strength in order to avoid failure due to high cycle fatigue.Heat efficiency of the connecting rod must be high.Must withstand buckling stress due to large compressive loads.Must be of low density to avoid bearing failure.1.3 CRANKSHAFTCrankshaft is the central link-up for the power produced by each cylinder in the engine. This crankshaft is one of the heavier part of the engine which is to be made strong to withstand the load from the con-rod.1.3.1 OPERATIONAL REQUIREMENTS AND SERVICE CONDITIONSFillet areas locations are to be verified since both torsional and crook loads are experienced during its service life.Counterbalancing of weight is to be considered in order to counteract the centrifugal forces created by crankpin.The projected areas of the big-end and main-end journals must be able to withstand maximum cylinder pressure.After grounding should have a surface finish of 0.5m to minimize bearing wear.Crankshaft must have the capac ity to absorb the thrust loads from clutches or torque converter.1.3.2 FUNCTIONSIt transmits power from combustion chamber to the flywheel through piston, piston rings and connecting rod.It harness and phase the mortal cylinders power impulses transmitted through the mechanism of the connecting rod which converts the reciprocating motion of the piston to rotary motion at crankshaft.It changes the linear displacement due to sudden buffet caused by the combustion chamber into smooth rotary motion which is the input to many devices.Crankshaft rotates in the cylinder in the cylinder block of the main bearing which supports the crankshaft which reduces the excessive wear.http//www.motorera.com/dictionary/pics/c/crankshaft.gif1.3.3 DESIRABLES MATERIAL CHARACTERISTICSMaterial nominal stress must not exceed 20% of tensile strength in divagation and 15% in torsion.Must have the capacity to withstand large force from gas combustion.Must have high heat withstanding capacity.Must have low th ermal expansion.Must have high adequate strength, toughness, hardness, and high fatigue strength.CHAPTER 2-MATERIAL SELECTION2.1 MATERIAL SELECTION FOR PISTONhhMaterial selection process is an integral part of the all overall product development process and must be considered in the early phases of the product definition. The material chosen for manufacturing the product is rumpd on the following consideration,Mass considerationStrength and wear considerationHeat-conduction considerationExpansion considerationBased on the higher up considerations the aluminium alloys satisfies all the factors equivalence to pull in atomic number 26 and firebrand.Mass consideration Since the pistons reciprocating force is high at high speed, it is necessary to turn to light material instead of array iron and steel. It has a relative density of 2.6 when compared with 7.8 for cast iron.Strength and wear consideration Since pure aluminium has low tensile strength of 92 to124 N/mm2 and spend of to 31N/mm2 at 300C, it is always alloyed with copper or silicon for piston materials which improves the strength to mass ratio. At high level of silicon, the alloy exhibits exquisite surface hardness, wear resistance properties and excellent dimensional stability.Heat-conduction consideration The better heat dissipation of aluminium-alloy pistons compared to cast-iron pistons greatly reduces the maximum piston-crown operating temperature of 250C 300C for allou pistons and 400 to 500C for cast iron.Expansion Consideration The thermal expansion is less for Al-Si alloy which has a thermal expansin of 0.000 021 and 0.000 017 per C for 12% Si alloy and 22% Si alloy.Fig() CES chart2.1.1 SURFACE CONSIDERATONDue to high speed reciprocation of the piston there may be so many losses or issues that must be considered. In that the rubbingal losses in piston assembly are majorly due to generation of heat. Subsequent raise in temperature can have this force out in the operation. In order to o vercome this problem, proper material with good thermal conductivity is chosen.2.2 MATERIAL SELECTON FOR CON-RODThe connecting rods are crucial and highly stressed component of the automotive engine subjected to alternative tensile and compressive stresses. Hence the material must be chosen based on the following conditionsGood elastic modulus,High fatigue strength,Low density to avoid bearing failure andHigh heat capacity.Based on the following conditions microalloyed steel is chosen which meets all the requirements mentioned above. This steel has a hardness level of 20-30 HRC. Small microalloying admittances of vanadium and niobium are used to increase the strength of carbon steel plates. 1.1%Mn-0.5%Cr is the best compounding to obtain thee high fatigue strength. Lowering the carbon content down to 0.33% and increasing the vanadium content to control the hardness gives toughness which improves the fatigue strength of free machining grades with S and Pb. The finally obtained chem ical composition is 0.33%C-1.05%Mn-0.5%Cr-0.12%V-.055%S-0.20%Pb-Ca which has fatigue strength of 26% higher than a conventional microalloyed forging steel. As for connecting rod, application of light metal like titanium alloys and aluminium alloys are been tested, due to high salute in light metal the connecting rod are made of microalloyed steel. This expression contains ferrictic-pearlitic-bainit.Fig() CES chart2.2.1 SURFACE CONSIDERATIONThe connecting rod is one of the highly stress concentrated part of the automotive engine. It is known that in the four cycle engines the connecting-rod small end is particularly stressed when the con-rod is at top dead centre at the beginning of the induction stroke, since the small end is ovalized by the tensile inertial forces exerted by the mass of the piston assembly. During both the stroke condition (expansion and contraction) gudgeon pin pushes the small end along the lower end of the arc, by which the compression load directly acts on t he con-rod without considerably stressing the eye. The eye is therefore subjected to repeated stresses, whereas the con-rod shank stress are reversed.(10)2.3 MATERIAL SELECTION FOR CRANKSHAFT (hh)Crankshaft are from materials which can be readily conventiond, machined and heat-treated and which have desirable mechanical properties such as adequate strength, toughness, hardness and high fatigue strength and of course , low make up. The highest quality steels are usually specified for congenial the con variationts given. Metals with optimum combination of bending and the stiffness are identified by creating a charts in CES by using implementation indices in axes.From the figure it is clear that the low carbon steel, high carbon steel, low alloy steel and medium carbon steel are satisfying the given constraints. Low alloy steel with chromium-molybdenum is used for crankshaft.This forging steel is suitable for medium to heavy-duty petrol and diesel-engine crankshafts. It presents no difficulty in live(a) working and afterwards can be advantageously machined to size.The alloying composition is 0.4% carbon, 1.2% chromium and 0.3% molybdenum.2.3.1 SURFACE CONSIDERATIONSSince crankshaft is the most highly strained part of the engine with high load acting on it the following factors must be considered.Pitting failure can occur in the crank-pinDue to omit of surface integrity lack of control over stress and temperature.CHAPTER 3 MANUFACTURING PROCESS3.1 MANUFACTURING PROCESS FOR PISTONSSBased on the material selected as aluminium alloys for piston, the manufacturing process is carried-out through stamp because of its mental ability to produce near-net shaped parts at the required production rate. Hence the process selected for this component is the Gravity die casting.3.1.1 GRAVITY DIE CASTINGThe pistons are produced from high-silicon alloys, such as 413.0 aluminium alloy. This alloy has high fluidity and can create high-definition surfaces through permanent m ould casting it also has high resistance to corrosion, good weldability, and low specific gravity. The universal acceptance of aluminium pistons for internal combustion engine applications is due to mainly to their light weight and high thermal conductivity.ss This type of casting is suitable for high volume production. The main advantages are the dimensional accuracy and surface finish. Castings ranging from few grams to 100kgs of aluminium alloy could be casted. This process could achieve higher mechanical properties than other casting by heat treatment. Since silicon has got good properties like, low shrinkage and imparting high fluidity which results in good casting. The maximum amount of silicon in cast alloy are in range of 22%-24%.(11)Manufacturing route ssThe h13 tool-steel mould is preheated to ccC to 450C, depending on the cast alloy and part size. initially, the preheat is achieved with a hand-held torch, the mould reaches a steady-state temperature. Molten aluminium is h eated to between 100C-200C above its liquidus temperature as shown below. Once the molten shot is in place the piston drives the mould in its place. Because of high thermal conductivity of the mould material, heat extraction from the molten metal is rapid and the metal solidifies in small channels before filling the mould completely.93.1.2 MICROSTRUCTURAL CHANGESSilicon has a diamond watch crystal bodily structure and is consequently precise brittle. These silicon structure damage the mechanical properties and nucleates on aluminium phosphide particles that is present in the melt as impurities. Further addition of sodium to the melt getters the phosphorous, which thereby increases the difficulty of sodium nucleation. Solidification is suppressed to lower temperature where the nucleation rate is large. This leads to remarkable refinement of microstructure. 9AluminiumSilicon 9From the figure above the dark feature is a shrinkage pore caused by a casting defect. This figure shows th e coarse silicon plates in an aluminium matrix.3.2 MANUFACTURING PROCESSMicroalloyed connecting-rod is manufactured by a simplified thermomechanical treatment like controlled cooling following hot forging. Through these processes desired properties could be obtained without quenching and tempering treatments. Hence pulverise forging was selected which would conveniently satisfy the manufacturing process for the selected material and component.3.2.1 POWDER FORGINGPowder forging rods are manufactured by combining metal powders into a pre-form that is sintered and reheated to forging temperature. Then it is completely forged to its final shape and machined to its final dimensions.This mixed powder is compacted at room temperature and high pressure upto to 200 to 400MPa. At the end of the process the powdered material acquires a density of 70 to 85%. This process has resulted in fully dense shape part which makes it suitable for high performance applications where high durability and s trength are required. The detailed manufacturing route of this PF process is shown below12The advantages of using PF process are,Good dimensional accuracyMinimum scattering of weightEnergy saving 123.2.2 MICROSTRUCTURE 1313pdfFrom the photograph of the microstructure of the connecting-rod material it is clear that the component contains pearlite and ferrite materials in composition. The above picture clearly indicates that in the powder metal connecting rods oxides are removed from the material surface by shot peening but the oxides are entrapped and remain below the surface causing the walkover to originate below the surface.3.3 MANUFACTURING PROCESS3.3.1 FORGING ssThe material selected for the crankshaft is forged steel which has a desirable mechanical properties such as adequate strength, toughness, hardness, and high fatigue strength. Hence the suitable manufacturing process for this steel is forging.Forging is a basic process in which the work-piece is shaped by compressive fo rces apply through various dies and tooling. For this forging process the dimensional tolerance range from 0.5 to 1% of the forging dimensions. At higher temperatures of about 700C dynamic forging recrystallisation occurs which increases the stress and strain deformation of the metal to make it hard.Manufacturing routePrepare a slug or billetHeat the work-piece in the suitable furnaceFor hot forging, preheat and lubricate the diesForge the billet in appropriate dies and in the proper sequenceClean the forging and check its dimensionsPerform additional operations such as heat treatments and straighteningInspect for defectsIn the hot forging process to form a metal billet two or more dies are brought unneurotic to each other at a suitable room temperature in a shape of the die impression. This process follows two basic requirements,The strength of the material must be low so that the die pressure can be kept within the limits.The material should be capable of deforming without fail ure and should exit required amount of deformation.The flow of metal and die filling are mainly determined by (i) flow stress and cooling ability(ii) friction and cooling effects at the material interface. In this process, definite amount of heat is received by all the parts after machining in heat treatment process. This is mainly carried-out to improve fatigue and wear properties. High quality parts with moderate cost can be made by this process. consequently this process offers high strength to weight ratio, toughness and resistance to impact and fatigue to the material which is considered in the performance of the crank shaft. 143.3.2 MICROSTRUCTUREHeating above recrystallisation temperature causes recrystallisation that removes the microstructure malformed and generated recrystallised grains. After eutectoid-carburizing martensite transformation takes place and a black portion near the surface is formed consisting of fine grains of ferrite and carbide.On quenching from the a ustentite () phase martensite is formed. This transformation is a diffusion-less shear transformation .Martensite is too brittle in plain carbon steel for practical applications and is subsequently tempered to restore some toughness.CHAPTER 4 startle MATERIAL4.1 switch over MATERIAL FOR PISTONhhCast iron refers to the family of ferrous alloys composed of iron, carbon ranging from 2.11% to about 4.5% and silicon of about 3.5%. They are classified by their structure ferritic, pearlitic, quenched and tempered or austempered. The equilibrium phase diagram relevant to cast iron is shown below where right boundary is 100%C. The eutectic temperature is 1154C and thereof cast irons are completely liquid at temperatures lower than those required for liquid steels.One of the major disadvantage of the aluminium as the base metal of the piston is that it has high co-efficient of linear expansion in the range of 0.0000221perC, compared with 0.0000117perC of cast iron. Aluminium has twice the expansion rate of cast iron. cementite is metastable (not completely stable) which has a tremendously low decomposition rate. However it can be made decomposed into alpha-ferrite and graphite. The graphitization can be controlled, promoted and accelerated by adding silicon, compulsory the rate of cooling and modifying the composition.ss151.4.1 LIMITATIONSRelative density is high of about 7.8When in tension, the presence of graphite acts as a stress riser weakens the material.Strength properties of the cast iron are significantly affected by the shape and size of graphite.Higher material and manufacturing cost.The major disadvantage is the shrinkage.1.4.2 POTENTIAL BENEFITSPresence of graphite in cast iron improves wear-resistance as it acts as a lubricant.High carbon content-degradation of ductility and fracture toughness.Good corrosion-resistance.Easy machinabilityWide range of composition and microstructures-easy weldability.4.2 ALTERNATE MATERIAL FOR CON-RODThe alternate materi al chosen for connecting rod is aluminium alloyed material as it is light in weight and provides long service life to the part. The aluminium alloys are high strength-to-weight ratio, resistance to corrosion by many chemicals, high conductivity and ease of formability. The material composition of aluminium is 7.6 to 8.4% Zn,1.8-2.3%Mg, 2-2.6%Cu, 0.08-0.25%Zr, 0.10%Si, 0.15%Fe, 0.05%Mn, 0.04%Cr and 0.06%Ti. When compared to othe alloys it convinces the constrains like low thermal expansion, wear-resistant, high fatigue strength and buckling.Majorly this material is chosen based on the following considerationMass considerationStrength and wear considerationExpansion considerationHeat-conduction considerationhttp//www.streetperformance.com/ART/PRODUCTS/100687/14012-8.jpg192.4.1 LIMITATIONSIt is more pricey than cast iron.Low dimensional accuracy and poor surface finish.Solidification is very slow.Occurrence of fracture in short transverse direction.Expansion rate is high when compared to cast iron with oure aluminium.2.4.2 POTENTIAL BENEFITSAluminium alloys can be easily machined and welded and formed.High dimensional accuracy with long service life.High yield strength in both tensile and compression.Aluminium is much better theatre director of heat than cast iron.Aluminium alloys provide improved resistance to abrasion and produce strength over temperature range.Improves the performances of the piston and thus the engine.4.3 ALTERNATE MATERIAL FOR CRANKSHAFTAs the crankshaft is the heavier moving part in the automotive engine, the material selected for this part has to be strong and light. Titanium alloys having high strength with reduced weight is used for crankshaft until and unless cost is not considered, as this material is very expensive.http//amt-advanced-materials-technology.com/s/cc_images/cache_867254901.jpg174.3.1 POTENTIAL BENEFITS OF TITANIUM ALLOYSTitanium has high melting point of about1678C which specifies strong creep and strength above wide te mperature range.The density is about 55% of steel with comparable strength.Ti alloys exists in two allotropic forms and Presence of thin oxide surface film-resistance over atmospher and sea environments including chlorine and organic chemicals.Reacts rapidly with oxygen, nitrogen and constituents in cutting tools at high temperature.4.3.2 LIMITATIONSEmbrittlement occurs during fabrication because of susceptibility of hydrogen, oxygen and nitrogen.Forging with titanium alloys is expensive but it increases the strength of the material.Ti alloys has a tendency to madden when tightening with connecting rod using bolt.Titanium is more difficult to machine due its antiphonal nature.NiobiumTitanium16CHAPTER 5 ALTERNATE MANUFACTURING PROCESS5.1 ALTERNATE MANUFACTURING PROCESS FOR PISTON5.1.1 SAND CASTINGSand casting is a one of the most possible manufacturing process where the unit production is comparatively less. In this process a mixture of sand and clay is compacted around the exer cise in which the pattern retains the shape of the original component to be produced. Then the pattern is removed in order have the cavity in the shape of the pattern. Generally low cost wooden patterns with gateways and runner are used. The molten metal is poured into the gateway by which it runs through the runner and fills the cavity and forms the exact shape of the cavity. Actually this whole transcription is housed in a box called flask. After which the molten metal allowed to solidify by cooling it. As the molten metal is solidified the sand pattern is broken and final work is done to obtain the finished component. The figure below shows the manufacturing process of the sand casting in detail.http//openlearn.open.ac.uk/file.php/1689/T173_2_020i.jpgFig(8.1) Sand Casting serve well 185.1.2ADVANTAGESLow tooling and equipment costComponent with any complicated shape can be producedRelatively cheap processPossibly components can be produced in large quantity.5.1.3 DISADVANTAGESHi gh tolerance ratio is requiredLabour cost is high.5.2 ALTERNATE MANUFACTURING PROCESS FOR CON-ROD5.2.1 SQUEEZE DIE CASTINGSqueeze die casting or liquid metal casting involves the process of solidification of molten metal under high pressure. The machinery includes a die, punch and ejector-pin. Under the pressure applied by the punch keeps the entrapped gases in solution and the rapid heat transfer takes place at the die-metal contact which results in fine microstructure with good mechanical properties.ss body waste of shrinkage and gas porosity happens because of precise metal metering, quiescent die filling and high pressure.5.2.2 ADVANTAGESPrecise dimension,Excellent surface finish,Fully shaped component is obtainedComplex part can be made to near-shape.5.2.3 DISADVANTAGESHigh initial costLimitation of high fluidity metals205.3 ALTERNATE MANUFACTURING PROCESS FOR CRANKSHAFT5.3.1 FORGINGIn forging operations the metal is squeezed to shape by die in which the metal is subjected to l arge plastic deformation. These metals are placed in-between closed dies under high temperature and pressure which results in succession of the final shape.http//www.forcast.ca/images/00436_faq1.gif21Forgings generally are subjected to additional finishing operations, such as heat treating to modify properties and machining to obtain right final dimensions and surface finish.5.3.2 ADVANTAGESGood utilizations of materialsGood dimensional accuracyHigh production rateGood reproducibilityLow die costs5.3.3 DISADVANTAGESInitial cost is highNot economical for small quantitiesMachining often necessaries