Anwar Ul-Hamid

Practical Engineering Failure Analysis

INTRODUCTION Engineering Products and Their Performance Engineering Properties of Materials Classes of Engineering Alloys Structure of Engineering Alloys Failure of Engineering Products Imperfect vs. Defective Products Definition and Objective of Failure Analysis Investigations Approach to Failure Analysis Investigations Background Requirements of the Failure Analyst: Scope of the Book ENGINEERING DESIGN-FABRICATION-PERFORMANCE Introduction Stages of Engineering Design Material Selection Fabrication of Engineering Alloys Solidification of Ingots Cold Working Recrystallization Thermomechanical Processing Primary Fabrication Techniques Secondary Fabrication Techniques Joining Techniques Service Performance Common Causes of Failure PRINCIPLES OF MECHANICS Introduction Concepts of Mechanics Concepts of Mechanical Force Concepts of Work and Energy Force and Motion Conservation of Energy Concept of Machines State of Mechanical Equilibrium Concept of Strain Concept of Stress Hooks Law PROPERTY EVALUATION Introduction Nondestructive Tests Destructive Tests: Measurement of Mechanical Properties STRESS ANALYSIS Introduction Uniaxial State of Stress Generalized State of Stress Multiaxial Stress-Strain Relationship Loading Conditions and Stress Thermal Stress Type of Stress Required to Produce Plastic Deformation Maximum Stresses Design Stresses Criterion for the Onset of Plastic Deformation (Yielding) Stress Concentration Criteria for Mechanical Failure Applications: Analysis of Stresses in Specific Components Solved Problems MACROSCOPIC ASPECTS OF FRACTURE AND FRACTURE MECHANICS Definition of Fracture Objective of Fracture Mechanics Use of the Terms Brittle and Ductile in Fracture Crack Loading Modes and Macroscopic Morphology of Fracture Surfaces Crack Propagation Under a Plane Strain Condition Crack Propagation Under a Plane Stress Condition Crack Propagation Under a Mixed State of Plane Strain and Stress Sequence of Events Leading to Fracture Classification of Crack Propagation Modes According to Loading Conditions Variables Affecting Fracture Behavior Basic Principles of Fracture Mechanics Linear Elastic Fracture Mechanics (LEFM) Use of Fracture Mechanics in Design Concept of Allowable Crack Size Use of Fracture Mechanics in Failure Analysis Selection of Materials Resistant to Fracture STRUCTURE OF ENGINEERING ALLOYS Introduction Principles of Thermodynamics Elements of Internal Structure Structure of the Atom Significance of the Electronic Structure of Atom Electronic Structure and Chemical Properties: Classes of Elements Origin of Interatomic Binding Forces Types of Interatomic Binding Forces Bond Strength and Properties of Materials Arrangement of Atoms in Perfect Crystals Understanding the Microscopic Plasticity of Perfect Crystals Crystal Imperfections Understanding the Microscopic Plasticity of Real Crystals Alloy Phases and Phase Change Equilibrium Phase Diagrams Methods of Strengthening Engineering Alloys MATERIALS CHARACTERIZATION Introduction Techniques for Microstructural Characterization Techniques for Chemical Analysis Microstructural Engineering Alloys CORROSION Introduction Low-Temperature Aqueous Corrosion High-Temperature Corrosion METALLURGICAL ASPECTS OF FRACTURE AND FRACTOGRAPHY Introduction Microscopic Aspects of Crack Nucleation Microscopic Mechanisms of Crack Propagation Fracture Modes and Fractography FAILURE ANALYSIS PROCEDURE Introduction Definition of the Problem Technical Background Experimental Program and Analysis Mode of Failure vs. Cause of Failure Data Interpretation and Terminology Recommendations Failure Analysis Reports CASE STUDIES Introduction Failure of Engineering Alloys Due to Improper Processing Practice Failure of Engineering Products During Manufacturing Effect of Variations in Design on Service Performance Failure of Engineering Products During Service Because of Unanticipated Service Conditions Failure of Engineering Products During Service Because of Improper Material Selection Failure of Engineering Products During Service Because of Improper Service Conditions APPENDIX A: CHEMICAL COMPOSITION AND CLASSIFICATION OF SELECTED STEELS APPENDIX B: UNITS OF MEASUREMENTS IN MECHANICS APPENDIX C: MOMENT OF INERTIA OF SELECTED CROSS SECTIONS INDEX

Failure of crude oil pipeline due to microbiologically induced corrosion

Abstract A 25·5 km long and 28 in. diameter underground pipeline used for transporting wet sour Arab Light grade crude oil failed after 3 years of service. The pipeline was operated at 40% of permissible flow velocity and capacity and protected under a corrosion inhibitor programme. The failure occurred due to corrosion of the lower surface of the pipeline resulting in pinholes within a period of one month. Eight corrosion damaged areas were detected over the entire length of the pipeline. Ultrasonic non-destructive inspection and close potential surveys were conducted on the failed pipeline. Various sections of the corrosion products were metallurgically evaluated using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. The corrosion product was identified using photometric and potentiometric analysis combined with X-ray diffraction. Crude oil and water samples obtained from the pipeline were also analysed. The material of the pipeline was identified as AISI grade C1018. Ultrasound testing revealed localised pitting at failed locations, while close potential surveys ruled out external corrosion. Experimental results indicated that the failure was caused by extensive microbiologically induced corrosion at the internal surface of the pipeline. Sulphate reducing bacteria present in the crude oil, along with below standard flow velocity of the latter, is thought to be responsible for the observed microbiologically induced corrosion. Replacement with a 20 in. diameter pipeline was suggested as a permanent solution to the corrosion problem, whereas a number of short-term measures were also recommended.

Synthesis, characterization, and water adsorption properties of a novel multi-walled carbon nanotube/MIL-100(Fe) composite

Conventional small-scale adsorption chillers generally employ silica-gel/water or zeolite/water working pairs given the relatively high level of mesoporosity and water affinity in these adsorbent materials. However, the coefficient of performance (COP) and specific cooling power (SCP) evaluated for the adsorption chiller using these adsorbent/adsorbate pairs cannot be still considered practically feasible in the context of a commercial system. Metal organic frameworks (MOFs) are not only characterized by much higher water adsorption capacities than these materials, but also can be mass-produced using much simpler methods than the template-assisted synthesis routes of most zeolites. However, the low intrinsic thermal conductivity of these materials limits their use as adsorbents in commercial-scale adsorption chillers. In this study, a novel composite composed of multi-walled carbon nanotubes (MWCNTs) incorporated in a MIL-100(Fe) framework has been synthesized using a molecular-level mixing process. The resulting composite, with varying volume fraction of MWCNTs, has been characterized for microstructure, degree of crystallinity, thermal stability, water sorption kinetics and hydrothermal cyclic stability for potential use as an adsorbent in commercial adsorption chillers.

Effect of aspect ratio, surface modification and compatibilizer on the mechanical and thermal properties of ldpe-mwcnt nanocomposites

Abstract In this work, nanocomposites of low density polyethylene (LDPE) / multiwall carbon nanotubes (MWCNTs) were prepared using melt blending. The effects of CNT aspect ratio, CNT loading, CNT chemical modification and the presence of a compatibilizer (maleated polyethylene) on morphology, mechanical and thermal properties of the CNT/LDPE composites were studied. Different MWCNTs were used: long CNT (LCNT); COOH modified CNT (MCNT) and short CNT (SCNT). FE-SEM images of produced nanocomposites show agglomeration of the MWCNTs. Addition of compatibilizer to both LCNT and MCNT nanocomposites improved their dispersion in the LDPE matrix. Yield strength and modulus increased with loading of various MWCNTs. However, ultimate strength, percent elongation and toughness reduced significantly for CNT loadings of 2% CNT and higher. The addition of maleated PE resulted in improvements of Young’s modulus, yield strength and ultimate strength but no impact on elongation at break or toughness. Addition of compatibilizer did not affect the crystallinity of the produced nanocomposites. In general, the use of CNT with high aspect ratio and the addition of compatibilizer and chemical modification improved the dispersion of MWCNTs and consequently improved most of the mechanical properties except elongation at break and toughness.

Corrosion Behavior of Coarse- and Fine-Grain Ni Coatings Incorporating NaH2PO4.H2O Inhibitor Treated Substrates

Plain carbon steel substrates were treated with NaH2PO4.H2O inhibitor for 24 hours and coated with Ni using dc and pulse electrodeposition in standard Watt’s bath. The effect of dc and pulse electrodeposition, on the microstructure and corrosion properties of Ni coatings in 3.5 wt% NaCl solution was studied. The effect of inhibitor on the deposition process and corrosion behavior was also examined. Materials characterization was performed using field emission scanning electron microscopy, cross-sectional scanning transmission electron microscopy, atomic force microscopy, x-ray diffraction and nanoindentation. Experimental results indicated that pulse electrodeposition produced fine grained Ni coatings that showed lower corrosion rate compared to coarse grained dc electrodeposited Ni. Pre-treatment of substrates with inhibitor did not adversely affect the deposition process and adherent Ni coatings were readily developed. The results showed that pulse electrodeposition could be used to produce hard corrosion resistant Ni coatings while the inhibitor treatment yielded enhanced corrosion protection by providing a protective buffer layer between the Ni coating and the substrate.

Corrosion study of SS304 and SS316 alloys in atmospheric, underground and seawater splash zone in the Arabian Gulf

ABSTRACT Bare stainless steel type 304 and 316 alloys were exposed to atmospheric, underground and seawater splash conditions in order to evaluate their corrosion properties. The exposure was undertaken for 15 months at the coastal and industrial city of Jubail located in the Arabian Gulf. The corrosivity of the environment was determined by testing the soil, groundwater, seawater and air quality. Corrosion rate of the exposed coupons was determined by weight loss method. The experimental results indicate that the both types of stainless steels corroded moderately in this environment. Primary factors influencing the corrosion process are thought to be high degree of variation in temperature and humidity combined with high chloride and sulphate concentrations. The corrosion rate of stainless steel is also compared with those reported for other international locations.

Corrosion behaviour of cast iron exposed to Arabian Gulf environment

Purpose – The purpose of this paper is to determine the long‐term corrosion behavior of cast iron coupons in the Jubail Industrial City (JIC), Saudi Arabia.Design/methodology/approach – The samples were exposed under atmospheric, underground, and splash zone conditions, at Khaleej Mardumah Test Station (KMTS) in Jubail. Soil, groundwater, seawater and air particulate samples were collected at the exposure sites and were analyzed. Secondary electron microscopy (SEM), X‐ray diffraction (XRD) and X‐ray fluorescence (XRF) were used to examine the surface morphology of the test coupons and identify the corrosion products developed on the surface of the metals. The corrosion rates of the coupons were determined by weight loss method.Findings – The results showed that the atmosphere, underground and splash zone conditions all were very corrosive to cast iron, due to temperature and humidity variations as well as the high chloride and sulfate concentrations in the region. The splash zone was the most corrosive re...

Effect of calcination on nanoscale zirconia produced by high temperature hydrolysis

Acidic and ammoniacal zirconium chloride solutions were subjected to high temperature hydrolysis (HTH) at temperatures between 110 and 150°C. The precipitates obtained from ammoniacal solutions were identified as monoclinic zirconia of Baddeleyite type as dried at room temperature (RT). Their lattice parameters varied between 5.004 and 5.493 Angstrom (Å), and crystallite size between 0.99 and 1.58 nm. The BET specific surface area of the dry powder was measured between 144 and 183 m2/g, corresponding to the equivalent particle diameter of 6.94 and 5.37 nm, respectively. Analysis carried out using field emission scanning electron microscope (FESEM) indicated that the size of zirconia particles ranged between 20 and 220 nm. Calcination of zirconia precipitates at 800°C for 2 hours (h) in air increased the crystallinity and crystal size of the precipitate, and affected the monoclinic crystal structure. It was also observed that the monoclinic crystal structure partially transformed into cubic and tetragonal zirconia.

Carburization behavior of high velocity oxy fuel sprayed metallic coatings at 900°C

Purpose – The purpose of this investigation was to evaluate the performance of high velocity oxy fuel (HVOF) coated SS-310 samples in a carburizing environment. Design/methodology/approach – The carburization behavior of metallic coatings with three different compositions was studied under isothermal carburizing exposure conditions at 900°C for 125 hours. The coatings were deposited on SS 310 substrates using the HVOF technique. The ASTM Standard method was used to evaluate coating adhesion. Scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, X-ray diffraction and weight gain were used to evaluate the surface morphology, microchemical composition, phase constitution and degree of environmental protection imparted by the coatings. Findings – The experimental results indicate that Ni-rich coating offered better protection to SS 310 alloy compared to Co-rich coatings in carburizing environments. This was thought to be due to the formation of a continuous protective layer of Cr2O3 ...

Failure analysis of coated galvanized steel panels

The purpose of this paper was to determine the mode and cause of failure of polyester-coated galvanized corrugated steel sheets that exhibited degradation of the coating after seven months into service.,Visual inspection and light microscopy revealed the extent of damage exhibited by the panels. Standard metallographic techniques were used to prepare samples obtained from both unused and failed sections. Light microscopy, scanning electron microscopy combined with energy dispersive x-ray spectroscopy and x-ray diffraction techniques were used to study the surface morphology, microstructural features, elemental composition and structure of the samples.,The failure occurred in the form of delamination and blistering of coated layer. Presence of solar radiation, humidity and water retention resulted in loss of adhesion, leading to coating delamination and flaking especially at the top surface. The coating at the bottom surface of the panels showed evidence of blistering caused by water vapor differential that existed between the environment and the coating because of prolonged (four months) wet conditions that existed at the manufacturer’s site during storage.,It is recommended that the coated panels are stored in covered area where direct exposure to atmospheric conditions can be prevented. If open storage is unavoidable, then the use of tarpaulin or plastic sheet as covering and vapor-phase inhibitors was recommended.,This paper provides an account of failure analysis of metal sheet panels. It identifies the mode and cause of failure and also provides recommendations to avoid such occurrences in the future. The information contained in this paper is useful for plant engineers and project managers working in the metal sheet industry.