Structure and Properties of Materials
Structure and Properties of Materials EGN 3365
University of Central Florida
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This 30 page Class Notes was uploaded by Lora Metz on Thursday October 22, 2015. The Class Notes belongs to EGN 3365 at University of Central Florida taught by Yongho Sohn in Fall. Since its upload, it has received 58 views. For similar materials see /class/227562/egn-3365-university-of-central-florida in General Engineering at University of Central Florida.
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Date Created: 10/22/15
Crystallographic Directions and Planes In Cubic Systems hkl is perpendicular to uvw hkl J uvw lllllllll 0 llllllllll q quoti o 39 IIIIIIIII39 lllllllll O I IQ lllllllll 100 100 110 1101 111 111 In Cubic Systems uvw Can Describe hkl Crystallographic Directions and Planes R loR 220 when R 1JR 2 R3EXR 2 I E V1W2 V2W1I 111 V1 W1 2 u1W2 u2W1j 112 V2 W2 quot ule VleE 111112 V1V2 W1W2 RluRzi Mug V W5 u vg w Polycrystalline Materials Square Grid Depicts Unit Cells A Grain Consists of Units Cells with The Same Orientation aw 39EE3 QC llllany Grains with ifferent Grientaton form a Polyerystallne Materials Grain Boundaries between Grains Polycrystalline Materials x La 39 39 E I quot1 rIrltlJ quotquot II 1 hr 3 39u r J quot i39 quot1 I quotquotl ilk quot 3quot quot1 I u 1 f a39 i I DquotJ L IEquot I 1quot u 239quot Iquot I rquot 5H IE1 I m l 5 Optical 39 39 1 39L 39 Photomicrograph of 1 my quot 39 FeCr Alloy Mixture T39i4 LR I 39 39 I In HTJif I 1 I a 3 4t quot quotj J quotI quot n J 3 Ext7 sz 2 39 ii I 539 fr 4 r Jquot 3 r 39l 39 1 39 I XRay Diffraction XRD Experimental Technique Determination of Crystal Structure Chemical Identification Determination of AtomicIonic Radius Many many others such as grain size crystallographic orientation etc Diffraction Incident Ray with Constant Wavelength Scattering as a Function of Atomic Arrangement Defined by Planes in the Unit Cell XRadiation lt 1 nm in wavelength in the Order of AtomicIonic Geometry 1000 nm for Visible Light Mm 1163 a F4 TIII quotl XRay Diffraction XRD I J will I Scutlznng wqu l H l h A H a m A ex A F xv H J x x l g 3 ii 1 mm f Constructive Interference 4in if xx x f x t t Destructlve Interference XRay Diffraction XRD Bragg Equation Bragg Equation At the Precise Geometry for Constructive Interference Scattered Waves in Phase the Difference in Path Length Between the Adjacent X ray Beams is Some Integral Number n of Radiation Wavelength 9t 6 Bragg Angle 29 Diffraction Angle d lnterplanar Spacing 39 4 t In39 V A KIligand m a 5 rid1 1 2 ram Iiquote x 1 W 39 J quotH ftquot EEK ME I Hf f I M nD Dl 39lgt LCf a 0 f quotA xquot quotArtLi i x 39 quot E CDE5 39lt3 3c 1n I C O D D Cr SQT n for constructive interference SQ QT dsinG n 2dsin9 XRay Diffraction XRD Interplanar Spacing and Reflection Rules ConstructiveDestructive Interference Interplanar Spacing d Distance between Adjacent th Planes For Cubic Systems 210 d hkl xh2k212 Reflection Rules for XRay Diffraction Diffraction Only Occurs When All th for SC hkl Even Number for BCC h k l are All Even or All Odd Numbers for FCC XRay Diffraction XRD Diffraction Patterns 110 ocFe BCC 211 200 39 quotHMTUWWQ39I h IW39W VW AMWWVW Lll racmn angle 2 hk Even Number for BCC h k I are All Even or All Odd can we Calcu39ate rFe Numbers for FCC XRay Diffraction XRD Diffraction Patterns 1110 aFe BCC 211 200 39 MTKWWQquot A IW39W VW AMWWVW Lli racticn angle 2i Typical XRay Source Bragg Equatlon n ZdSme Cu with xo1542 nm dth a o Cu K Radiation xhz 1lt2 12 4 ao Sample Problem 321 Page 108 for Al Impact Energy and Impact Testing gt Prior to Fracture Mechanics Impact testing techniques were established gtImpact Energy Energy necessary to fracture the test specimen gtCommon techniques l Charpy test and 2 Izod test gtImpact load in the form of a swinging pendulum gtImportant feature is stress concentrating Notch machined into the side of the sample Impact Testing a Notched Specimen b Schematic representation of the impact testing machine Energy necessary to fracture is directly calculated from the difference in initial and nal heights of pendulum Increasing the size of the notch can result in lowering of impact energy Ductile to Brittle Transition Temperature gt Variation in fracture mode with temperature gt Failure in brittle mode at relatively low temperatures gt Increasing yield strength and decreasing dislocation velocities gt Near the transition temperature between ductile and brittle fracture surface exhibits mixed texture gt Failure of Liberty Ships during World War 11 Low carbon steels Temperature Dependence of Impact Energy Increase in impact energy with temperature and vice versa Fatigue gt Failure due to repeated or uctuating or cyclic loading gt Stress level below the ultimate tensile stress gt Fatigue curve or S N curve Plot of stress S versus number of cycles N on logarithmic scale gt Material which can Withstand stress of 800 MPa on single loading fractures after 10000 applications of stress less than 600 MPa gt Applied Stress can be 1 Axial 2 Bending 3 Torsional Regular Sinusoidal Cycle AMM Variation of Stress with time Repeated S N l vvvv W Random Stress Cycle tress Cycle Parameters to characterize uctuating stress cycle Um mean stress 039 range of stress 0a stress amplitude R stress ratio i 107N112 IE 3 gt Fatigue Limit gt Low cycle fatigue lt 104 to 105 gt Fatlgue Strength gt ngh cycle fatigue gt104 to 105 gt Fatigue Life Fatigue Failure Stages Fatigue failure occurs by gt Crack Initiation gt Crack Propagation gt Final Failure Crack Initiation gt Surface of Component gt Stress Concentration gt Surface scratches sharp corners keyways threads dents etc Crack Propagation Stage I gt Propagation along the crystallographic planes of high shear stress Stage II gt Crack extension rate increases dramatically gt Change in propagation direction gt Crack growth proceeds by repetitive plastic blunting and sharpening at the crack tip Fatigue crack propagation mechanism stage II a zero or maximum compressive load b small tensile load c maximum tensile load d small compressive load e zero or maximum compressive loa f small tensile load The loading axis is vertical Fractographs Beach Marks I Fatigue Stn39ations Crack Propagation Rate gt Crack growth rate initially small increases with crack length gt Growth rate enhanced with increasing applied stress NonDestructive Testing gt Evaluation of the materials gt Usefulness of the materials unaffected gt Identi cation of potentially critical aws gt Analysis of existing failure or prevent future failures XRadiography Radiator suture Beer s Law I intensity of beam transmitted through material no is 9 lm mg Phi x thickness ofmaterial 1 Incident beam intensity 1 linear absorption coef cient Increases with atomic number Fault shcwr m expsed lm Electromagnetic spectrum Wavelength lt lnm Ultrasonic Testing Acoustic spectrum with frequencies 125 MHZ above the audible range 20 to 20000 Hz Ultrasonic waves are more mechanical in nature It requires transmitting me 39um Re ection coef cient R Other Non Destructive Tests gt Eddy Current Testing gt Magnetic Particle Testing gt Liquid Penetrant Testing gt Acoustic Emission Testing Failure Modes gt Ductile fracture gt Brittle Fracture gt Fatigue failure gt Corrosionfatigue failure gt Stresscorrosion failure gt Liquid metal embrittlement gt Hydrogen Embrittlement gt Creep gt Wear Failure Analysis gt Background Information gt Preliminary Examination gt Non Destructive Testing gt Mechanical Testing gt Cleaning of fracture surfaces gt Macroscopic and Microscopic Examination gt Application of Fracture Mechanics gt Analyzing the evidence gt Drawing conclusions and Writing report