SME 4133 Failure of Engineering Components and Structures

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

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

SME 4133 Failure of Engineering Components and Structures SKMM 4133 Failure of Engineering Components and Structures Failure Analysis of Metallic Components • 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 INTRODUCTION M. N. Tamin, UTM

SME 4133 Failure of Engineering Components and Structures SKMM 4133 Failure of Engineering Components and Structures Week 1 2 3 4 5 6 7 8 9 10 11 Date (Sun. ) 07 Sep 14 Sep 21 Sep 28 Sep 05 Oct 12 Oct 19 Oct 26 Oct 02 Nov 09 Nov 16 Nov 12 13 14 15 16 17 23 Nov 30 Nov 07 Dec 14 Dec 21 Dec 28 Dec INTRODUCTION Lecture & Topics Lecture 1 2 3 A A A B B B C C C SEMESTER BREAK Test 1 C C C C D D E E E D D E E Test 2 Closure STUDY LEAVE FINAL EXAMINATION Topics 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 M. N. Tamin, UTM

SME 4133 Failure of Engineering Components and Structures SKMM 4133 Failure of Engineering Components and Structures COURSE CONTENT 1. 0 Introduction 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. 0 Materials Defects Processing-structure-property relationship, metallurgical imperfection, processing defects, NDT methods, surface defects and corrosion, propagation of defects, tools for metallurgical failure analysis 3. 0 Failure 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. 0 Buckling of Struts and Columns Euler’s column theory, Rankine-Gordon formula, eccentric loading, inelastic buckling. INTRODUCTION M. N. Tamin, UTM

SME 4133 Failure of Engineering Components and Structures SKMM 4133 Failure of Engineering Components and Structures COURSE CONTENT (Continued) 5. 0 Fatigue 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. 0 Creep 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. 0 Fatigue 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. INTRODUCTION M. N. Tamin, UTM

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

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

SME 4133 Failure of Engineering Components and Structures SKMM 4133 Failure of Engineering Components and Structures Classification of the causes of failure 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 timevarying load, thermal cycling, corrosion fatigue. • Severe stress raiser inherent in design. • Inadequate stress analysis • Mistake in designing on basis of static tensile properties only • High-temperature failure – creep, oxidation, local melting, warping. • Static delayed fracture – hydrogen embrittlement, INTRODUCTION M. N. Tamin, UTM

SME 4133 Failure of Engineering Components and Structures SKMM 4133 Failure of Engineering Components and Structures Classification of the causes of failure Faulty processing • Flaws due to faulty composition – wrong material, inclusions, embrittling impurities. • Abnormalities due to heat treatment – grain growth, precipitation, excessive retained austenite, decarburization. • Defects originating in ingot making and casting – porosity, non-metallic inclusions, segregation. • Flaws due to case hardening – intergranular carbides, soft core. • 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. INTRODUCTION • 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. M. N. Tamin, UTM

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

SME 4133 Failure of Engineering Components and Structures SKMM 4133 Failure of Engineering Components and Structures Steps in Performing Failure Analysis • 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. INTRODUCTION • 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) M. N. Tamin, UTM