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INTRODUCTION M.N. Tamin, UTM SME 4133 Failure of Engineering Components and Structures MODULE 1 INTRODUCTION SKMM 4133 Failure of Engineering Components.

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Presentation on theme: "INTRODUCTION M.N. Tamin, UTM SME 4133 Failure of Engineering Components and Structures MODULE 1 INTRODUCTION SKMM 4133 Failure of Engineering Components."— Presentation transcript:

1 INTRODUCTION M.N. Tamin, UTM SME 4133 Failure of Engineering Components and Structures MODULE 1 INTRODUCTION SKMM 4133 Failure of Engineering Components and Structures

2 INTRODUCTION M.N. Tamin, UTM SME 4133 Failure of Engineering Components and Structures Fatigue crack in root area of a turbine blade List possible questions regarding this fracture situation OPENING REMARKS SKMM 4133 Failure of Engineering Components and Structures

3 INTRODUCTION M.N. Tamin, UTM SME 4133 Failure of Engineering Components and Structures Failure Inability of a component to perform according to its intended function. Failure Analysis The examination of a failed component and of the failure situation in order to determine the causes of failure Failure Analysis of Metallic Components SKMM 4133 Failure of Engineering Components and Structures

4 INTRODUCTION M.N. Tamin, UTM SME 4133 Failure of Engineering Components and Structures SKMM 4133 Failure of Engineering Components and Structures WeekDate (Sun.) Lecture & Topics Topics Lecture 1 Lecture 2 Lecture SepAAA A – Introduction - Overview - Requirements and approach B – Static failure due to overload and instability. C – Fatigue failure - High-cycle fatigue - Low-cycle fatigue D – Creep and stress rupture E – Fatigue crack propagation (OPTIONAL) – Computational aspects of failure analysis 214 SepAAA 321 SepBBB 428 SepBBB 505 OctCCC 612 OctCCC 719 OctSEMESTER BREAK 826 OctTest1CC 902 NovCCC 1009 NovCCC 1116 NovDDD 1223 NovDDD 1330 NovEEE 1407 DecEEE 1514 DecETest 2Closure 1621 DecSTUDY LEAVE 1728 DecFINAL EXAMINATION

5 INTRODUCTION M.N. Tamin, UTM SME 4133 Failure of Engineering Components and Structures COURSE CONTENT 1.0Introduction Historical background, origin, detection and prevention of failure, types of mechanical failure: gross yielding, fatigue fracture, buckling, creep rupture, review of stress field and stress concentration, statistical aspect of failure analysis, loading spectrum, metallurgical aspect of component failure. 2.0Materials Defects Processing-structure-property relationship, metallurgical imperfection, processing defects, NDT methods, surface defects and corrosion, propagation of defects, tools for metallurgical failure analysis 3.0Failure due to overload Yield failure theories, idealized material behavior, plastic bending of beams, collapse loads, plastic torsion of circular bar, residual stresses after yielding. 4.0Buckling of Struts and Columns Euler’s column theory, Rankine-Gordon formula, eccentric loading, inelastic buckling. SKMM 4133 Failure of Engineering Components and Structures

6 INTRODUCTION M.N. Tamin, UTM SME 4133 Failure of Engineering Components and Structures COURSE CONTENT (Continued) 5.0Fatigue Failure High-cycle fatigue, Strength-life (S-N) curves, cumulative damage concept, life prediction and fracture control; low-cycle fatigue, strain cycling concept, strain-life curve and low-cycle fatigue relations, influence of non-zero mean strain and non-zero mean stress. 6.0Creep and Stress Rupture Theories for predicting creep behavior, Larson-Miller and Manson-Haferd parameters, uniaxial and multi-axial state of stress, cumulative creep concept, creep-fatigue interaction. 7.0Fatigue Crack Propagation and Control Basics of fracture mechanics, linear elastic and elastic-plastic fracture mechanics, stress intensity factor range, fatigue crack growth rate, factors affecting crack propagation, fatigue fracture mechanisms in metals. SKMM 4133 Failure of Engineering Components and Structures

7 INTRODUCTION M.N. Tamin, UTM SME 4133 Failure of Engineering Components and Structures COVERAGE CONCEPT FUNDAMENTAL THEORY ESTABLISHED WORK STATISTICS CASE STUDIES SKMM 4133 Failure of Engineering Components and Structures

8 INTRODUCTION M.N. Tamin, UTM SME 4133 Failure of Engineering Components and Structures SCOPE MODES OF FAILURE Gross Yielding Fatigue Fracture Creep Rupture Buckling Static Delayed Fracture REQUIREMENTS FOR FAILURE ANALYSIS Mechanical design and analysis Force analysis Stress analysis Chemical analysis Metallography Fractography Mechanical testing Failure simulation SKMM 4133 Failure of Engineering Components and Structures

9 INTRODUCTION M.N. Tamin, UTM SME 4133 Failure of Engineering Components and Structures Faulty design considerations/ misapplication of materials Ductile failure – excessive deformation (elastic or plastic), tearing or shear fracture). Brittle fracture – from flaws and critical stress raisers. Fatigue failure – due to time- varying load, thermal cycling, corrosion fatigue. High-temperature failure – creep, oxidation, local melting, warping. Static delayed fracture – hydrogen embrittlement, Severe stress raiser inherent in design. Inadequate stress analysis Mistake in designing on basis of static tensile properties only Classification of the causes of failure SKMM 4133 Failure of Engineering Components and Structures

10 INTRODUCTION M.N. Tamin, UTM SME 4133 Failure of Engineering Components and Structures Faulty processing Flaws due to faulty composition – wrong material, inclusions, embrittling impurities. Defects originating in ingot making and casting – porosity, non- metallic inclusions, segregation. Defects due to working – laps, seams, hot-short splits, excess local deformation Irregularities / mistakes due to machining, grinding or stamping – burns, tearing, cracks. Welding defects – voids, undercuts, residual stresses, HAZ, lack of penetration. Abnormalities due to heat treatment – grain growth, precipitation, excessive retained austenite, decarburization. Flaws due to case hardening – intergranular carbides, soft core. Defects due to surface treatment – plating, chemical diffusion, hydrogen embrittlement. Parting-line failure in forging - due to poor transverse properties. Careless assembly – mismatch of mating parts, residual stress, gouges. Classification of the causes of failure SKMM 4133 Failure of Engineering Components and Structures

11 INTRODUCTION M.N. Tamin, UTM SME 4133 Failure of Engineering Components and Structures Deterioration in service Overload / unforeseen loading conditions Wear – erosion, galling, seizing, cavitation. Corrosion – chemical attack, stress corrosion, dezincification. Inadequate / misdirected maintenance or improper repair – welding, grinding, cold straightening. Disintegration by chemical attack, attack by liquid metals or plating at elevated temperature Radiation damage - decontamination may destroy evidence for the cause of failure. Accidental condition – abnormal operating temperature, severe vibration, impact, thermal shock. Classification of the causes of failure SKMM 4133 Failure of Engineering Components and Structures

12 INTRODUCTION M.N. Tamin, UTM SME 4133 Failure of Engineering Components and Structures Description of the failure situation – Background information, history of usage, design of component. Visual inspection – DO NOT damage the fracture surface. Mechanical design analysis (stress analysis) – to establish the cause of failure. Was the part of sufficient size? Chemical design analysis –to establish the suitability of the material wrt corrosion resistance. Fractography – examine fracture surface to establish the mechanism of fracture. Metallographic examination – to help establish such facts as whether the part has correct heat treatment. Determine properties – to establish properties pertinent to the design. Failure simulation - to establish response of identical component under exact condition of loading, numerical simulation. Formulation of conclusions, Report writing (may include recommendations) Steps in Performing Failure Analysis SKMM 4133 Failure of Engineering Components and Structures


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