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FINITE ELEMENT SIMULATION OF ND:YAG LASER SHOCKPEENED NICKEL CHROME, COBALT CHROME BASE METAL ALLOY FOR DENTAL APPLICATION

FINITE ELEMENT SIMULATION OF ND:YAG LASER SHOCKPEENED NICKEL CHROME, COBALT CHROME BASE METAL ALLOY FOR DENTAL APPLICATIONILAVARASAN S2010118017KARTHIKEYAN S2010118024KUMAR K2010118026SARATH RAJA G2010118040

Project Guide Dr. K Shanmuga Sundaram Associate ProfessorDepartment of Mechanical Engineering College of Engineering, GuindyAnna University, Chennai-25

IntroductionThe main objective of this project is to give a solution to the material selection for the dental implants or any other dental treatments. Dental Implants are become necessary now a days. Because,

69% of adults at an age of 35 to 44, lost at least one of their permanent teeth by accident, gum disease or failed root canal.26% of adults at an age of 74, have lost all their permanent teeth.

Objective Selecting the suitable material, laser for the dental application and comparing the changes in the mechanical properties after doing shock peening operation

HardnessWear resistanceYield strengthUltimate strengthModulus of ElasticityThe experimental results and the theoretical results (simulation) are compared and studied

Material SelectionSelection of Materials are based on the following things,Bio compatibilityColorLife DurabilityEasy for shapingAestheticsPhysical propertiesLow thermal conductivity and expansionResistance to wear and abrasionResistance to chemical erosionFlexibility to adopt to a shapeStrength to withstand the Mastication force

Material Selection Disadvantages Poor StrengthHigh costLow Wear resistanceLess aestheticsTakes longer time to makeDifficult to adjustDull in tooth colorMay irritate the sensitive teeth (conducts cold)High costGalvanic ShockMore brittleLess lifeChance for future cavitiesMore time to place

Gold AlloyPorcelainPlastic + Fine GlassTitaniumCobalt ChromiumNickel Chrome

Suitable MaterialsCHEMICAL COMPOSITION :: Ni-Cr

CHEMICAL COMPOSITION :: Co-CrELEMENTPROPOSITIONNICKEL65.2 %CHROME22.5 %MOLYBDENUM9.5 %OTHERS (Fe, Si, Mn, Nb)2.8 %

ELEMENTPROPOSITIONCOBALT61 %CHROMIUM26 %MOLYBDENUM6 %TUNGSTEN5 %OTHERS (Si, Fe, Ce)2 %

Laser Shock Peening

Innovative surface enhancement process for increasing resistance of the components. This process creates compressive stress, four to five times deeper than conventional shot peening process. This compressive surface stresses inhibit the initiation and propagation of fatigue cracks. The peening drives a high amplitude shock wave into a material surface using high energy pulsed laser. Hence the purpose of this study is to compare mechanical properties with microstructure of Nd-YAG laser treated and non-treated on Ni-Cr and Co-Cr

Nd: YAG Laser Shock peening

0.4 mm to 1 mmLow cost and easily availableproduce continuous laser at room temperatureportable systems

Parameter

ConstantSpot Diameter1.2 mmPulse Duration10 msDepth of Penetration0.48 to 0.73 mmArgon Shielding450Peening Speed160 mm/sNo of Scan per Second 4

Variables Pulse Energy Density 450 , 340 , 430 J/cm2Pulse Frequency 1.1, 0.5, 2.5 kHz

Tensile Specimen using Pro/E

Finite Element Analysis

Structural Static Analysis Solid 185Element Size 0.0001 (Fine Mesh)

Meshed view of Specimen

Displacement Vector SumX Component Displacement Y Component DisplacementZ Component Displacement

11

1st Principal StressVon Mises StressXY Shear StressZ Component Stress

1st principal StrainVon Mises StrainZ Component StrainElastic Strain Intensity

Improved Mechanical Properties Vector Plot of Displacement Vector Plot of Elastic Strain

ResultThe Strain value of the Co-Cr Alloy got the smallest value than the Ni-Cr Alloy. So the less strain value material is opted for Dental applications.Obviously Co-Cr alloy is better than Ni-Cr alloy.

Maximum Strain Value of Ni-Cr alloy : 657 Maximum Strain Value of Co-Cr alloy : 553

ResultSince the Co-Cr alloy is suitable for dental applications, the Laser Parameter can be identified.

Pulse Energy Density value at max. strain value is 360104J/m2Pulse Energy Density value at min. strain value is 420104 J/m2

So the least strain value is occurred during the Pulse Energy Density value of 420 104 J/m2

ConclusionLaser Shock Peening process is a trendsetter now a days in the medical field. Its low cost and accurate operations make it popular. So that it gives an exact solution for all kind of age group who are all came with a dental problem. Nickel Chromium and Cobalt Chromium are some important materials in dental implants. These materials can be used in dental applications without doing shock peening process. But it cannot withstand for a longer period. LSP improves the fatigue strength and compressive stress of the material. The aesthetics of Co-Cr is little lower than Ni-Cr. Otherwise Co-Cr is the strongest material and can be shaped into any molar shape.

REFERENCES[1]O Brian WJ. 2002 Dental Materials and their selection. Chicago IL. Quintessence Publishing Co., Inc.; 2002.p.372-377[2]Ding K, Ye L. Laser Shock peening performance and process simulation. Cambridge: Woodhead Publishing; 2006[3]Ballard P. Residual Stresses induced by rapid impact Application for laser shocking. Ecolo Polytechnique, April 1991[4]Philips and Anusavic. Science of Dental Materials

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