Failure Analysis of Weld Repaired Turbine Rotor

2004 ◽  
Author(s):  
Fred V. Ellis ◽  
Blaine W. Roberts
Keyword(s):  
Weld Metal ◽  
Failure Analysis ◽  
Stress Analysis ◽  
Failure Mechanism ◽  
Turbine Rotor ◽  
Weld Bead ◽  
Design Stage ◽  
Weld Repair ◽  
Fracture Appearance ◽  
Product Forms

The first stage of an IP turbine rotor failed after approximately eight years of service. The rotor had been weld repaired using a 360 degree all weld metal buildup. The rotor material was specified as ASTM A-470 Class 8, 1Cr-1Mo-1/4V forging material, and the weld metal was Modified 9Cr-1Mo known as Grade 91 in the wrought product forms. The weld repair procedure used a controlled weld bead deposition process to refine the grain size of the HAZ. A failure analysis was performed including metallurgical examination and stress analysis. For the failure analysis, the primary features of interest were the fracture appearance, cracking/failure location, and failure mechanism. The fracture appearance was “lack of fusion” where the fracture surface nominally conforms to the weld bead shape. The primary cracking and failure was located at the fusion interface of the weld repair. The failure mechanism was creep rupture. Based on the thermal and stress analysis, the probable root cause of failure was improper location of the weld fusion line during the design stage. Both the operating stress and temperature were higher than design. The operating temperature was higher than the design temperature because of the lower cooling of the rotor experienced in service than predicted. Thus, the HAZ was located at a radial position having higher than allowable temperatures and stresses for the creep weak HAZ.

Evaluation of Smear and Its Effect on the Mechanical Integrity of Plated Through Hole-Inner Plane Interface in Thick Printed Wiring Boards

2000 ◽  
Vol 123 (1) ◽  
pp. 6-15 ◽  
Author(s):  
R. Venkatraman ◽  
K. Ramakrishna ◽  
K. Knadle ◽  
W. T. Chen ◽  
G. C. Haddon
Keyword(s):  
Failure Analysis ◽  
Stress Analysis ◽  
Failure Mechanism ◽  
Stress Testing ◽  
Large Strain ◽  
Peel Test ◽  
Stress Tests ◽  
Printed Wiring Boards ◽  
Element Analysis ◽  
Plated Through Hole

In multi-layer printed wiring boards (PWBs), electrical connections between different layers are accomplished with plated through holes (PTHs). The reliability of the PTH barrel and the PTH-inner plane (IP) connection depends not only on the design but also on the conditions of manufacturing and assembly processes of the board. The concerns associated with manufacturing arise from drilling which heats up and smears the surrounding epoxy onto the copper inner plane surfaces and also from subsequent chemical hole-clean operations which desmear the drilled holes. Good adhesion of the PTH copper to the desmeared PTH wall and to the copper inner planes is important for the reliability of the PTHs during assembly and field service. PWB coupons consisting of resin-glass bundle areas as well as resin filled clearance areas surrounding the PTH have been considered for a series of experiments and tests. On these coupons, accelerated stress tests and failure analysis of the PTHs at the end of these tests have been conducted. An elasto-plastic finite element analysis of the PTH strains for a temperature excursion of 102°C has been carried out for signal PTHs without and with IP connections. A peel test, using a micro-mechanical tester, has also been carried out to assess the adhesion of PTH copper to different regions along the drilled hole. All of the testing techniques have been supplemented by suitable analytical techniques for studying the distribution of smear on the copper inner planes. A birefringence technique to estimate the temperature of the hole wall during drilling has been described. All of the fails observed during stress testing are in the form of cracks in the PTH barrel, the plane of the crack being perpendicular to the barrel axis. The cracks are localized near the glass bundle-resin rich interface. It has also been observed in the failure analysis that the PTH/IP connections are not susceptible to failure during the accelerated stress testing conditions considered. These observations are also supported by the results of stress analysis. The results of stress analysis show that the interior clearance holes show higher strains than those closer to board surfaces, suggesting that the PTH barrel failure is likely to occur at the clearance hole and that the likelihood of failure at the interior clearance holes is higher than those closer to the PWB surfaces. The results of the peel test reveal that in the glass bundle-resin regions, the adhesion along the PTH wall is determined by the mechanical interlocking between the plated copper and the glass bundles and is relatively insensitive to desmear operations. However, adhesion in the resin-rich areas is a strong function of the desmear operation, which enhances the adhesion of the PTH to the resin. Finally, it is shown that the birefringence technique may be used effectively to estimate the drilling temperature and, hence, the degree of smearing and PTH quality. It is concluded that while smear may play an important role in the failure of PTHs in PWBs, for thick packaging boards with high aspect ratio PTHs, the predominant failure mechanism is less likely to be smear related. Such a failure mechanism would be preceded by failure in the PTH barrels as a result of the large strain concentrations imposed at specific locations within the cross-section.

Case Study in Fault Isolation of a Metal Short for Yield Enhancement

2010 ◽  
Author(s):  
Sarven Ipek ◽  
David Grosjean
Keyword(s):  
Failure Analysis ◽  
Failure Mechanism ◽  
Photon Emission ◽  
Fault Isolation ◽  
Yield Enhancement ◽  
Analysis Technique ◽  
Laser Signal ◽  
Signal Injection ◽  
Microscopy Techniques

Abstract The application of an individual failure analysis technique rarely provides the failure mechanism. More typically, the results of numerous techniques need to be combined and considered to locate and verify the correct failure mechanism. This paper describes a particular case in which different microscopy techniques (photon emission, laser signal injection, and current imaging) gave clues to the problem, which then needed to be combined with manual probing and a thorough understanding of the circuit to locate the defect. By combining probing of that circuit block with the mapping and emission results, the authors were able to understand the photon emission spots and the laser signal injection microscopy (LSIM) signatures to be effects of the defect. It also helped them narrow down the search for the defect so that LSIM on a small part of the circuit could lead to the actual defect.

Unique Autoclave Stress Induced Failure Mechanism

2005 ◽  
Author(s):  
John Butchko ◽  
Bruce T. Gillette
Keyword(s):  
Corrosion Rate ◽  
Grain Boundary ◽  
Failure Analysis ◽  
Failure Mechanism ◽  
Metal Corrosion ◽  
Corrosion Mechanism ◽  
Reliability Testing ◽  
Process Change ◽  
Transistor Reliability ◽  
Pass Through

Abstract Autoclave Stress failures were encountered at the 96 hour read during transistor reliability testing. A unique metal corrosion mechanism was found during the failure analysis, which was creating a contamination path to the drain source junction, resulting in high Idss and Igss leakage. The Al(Si) top metal was oxidizing along the grain boundaries at a faster rate than at the surface. There was subsurface blistering of the Al(Si), along with the grain boundary corrosion. This blistering was creating a contamination path from the package to the Si surface. Several variations in the metal stack were evaluated to better understand the cause of the failures and to provide a process solution. The prevention of intergranular metal corrosion and subsurface blistering during autoclave testing required a materials change from Al(Si) to Al(Si)(Cu). This change resulted in a reduced corrosion rate and consequently prevented Si contamination due to blistering. The process change resulted in a successful pass through the autoclave testing.

Investigation of High Frequency Failures on a 0.35μm CMOS IC

1999 ◽  
Author(s):  
Alan Kennen ◽  
John F. Guravage ◽  
Lauren Foster ◽  
John Kornblum
Keyword(s):  
Failure Analysis ◽  
Failure Mechanism ◽  
Integrated Circuit ◽  
Metal Layer ◽  
Ion Beam ◽  
Stress Test ◽  
Design For Test ◽  
Interface Failure ◽  
Serial Interface ◽  
High Impedance

Abstract Rapidly changing technology highlights the necessity of developing new failure analysis methodologies. This paper will discuss the combination of two techniques, Design for Test (DFT) and Focused Ion Beam (FIB) analysis, as a means for successfully isolating and identifying a series of high impedance failure sites in a 0.35 μm CMOS design. Although DFT was designed for production testing, the failure mechanism discussed in this paper may not have been isolated without this technique. The device of interest is a mixed signal integrated circuit that provides a digital up-convert function and quadrature modulation. The majority of the circuit functions are digital and as such the majority of the die area is digital. For this analysis, Built In Self Test (BIST) circuitry, an evaluation board for bench testing and FIB techniques were used to successfully identify an unusual failure mechanism. Samples were subjected to Highly Accelerated Stress Test (HAST) as part of the device qualification effort. Post-HAST electrical testing at 200MHz indicated that two units were non-functional. Several different functional blocks on the chip failed electrical testing. One part of the circuitry that failed was the serial interface. The failure analysis team decided to look at the serial interface failure mode first because of the simplicity of the test. After thorough analysis the FA team discovered increasing the data setup time at the serial port input allowed the device to work properly. SEM and FIB techniques were performed which identified a high impedance connection between a metal layer and the underlying via layer. The circuit was modified using a FIB edit, after which all vectors were read back correctly, without the additional set-up time.

Failure and Stress Analysis of Cu TSVs Using GHz-Scanning Acoustic Microscopy and Scanning Infrared Polariscopy

2015 ◽  
Author(s):  
Ingrid De Wolf ◽  
Ahmad Khaled ◽  
Martin Herms ◽  
Matthias Wagner ◽  
Tatjana Djuric ◽  
...  
Keyword(s):  
Failure Analysis ◽  
Stress Analysis ◽  
Rayleigh Waves ◽  
Acoustic Microscopy ◽  
Scanning Acoustic Microscopy ◽  
Through Silicon Vias ◽  
Stress Anisotropy ◽  
Silicon Vias ◽  
Ic Technology ◽  
Detection Of Defects

Abstract This paper discusses the application of two different techniques for failure analysis of Cu through-silicon vias (TSVs), used in 3D stacked-IC technology. The first technique is GHz Scanning Acoustic Microscopy (GHz- SAM), which not only allows detection of defects like voids, cracks and delamination, but also the visualization of Rayleigh waves. GHz-SAM can provide information on voids, delamination and possibly stress near the TSVs. The second is a reflection-based photoelastic technique (SIREX), which is shown to be very sensitive to stress anisotropy in the Si near TSVs and as such also to any defect affecting this stress, such as delamination and large voids.

Failure Analysis on a Counterweight Assembly of an Aeroengine

2011 ◽  
Vol 339 ◽  
pp. 342-348
Author(s):  
Hai Jun Tang ◽  
Hong Yu Yao
Keyword(s):  
Heat Treatment ◽  
Stress Concentration ◽  
Failure Analysis ◽  
Failure Mechanism ◽  
Treatment Process ◽  
Hardness Test ◽  
Heat Treatment Process ◽  
Material Loss ◽  
Structure Strength ◽  
Crucial Part

The paper presents a failure analysis on a counterweight assembly installed on crank shaft which resulted in an in-flight shutdown of a piston aeroengine. The counterweight assembly failure includes counterweight block material loss and fractured washer which is the most crucial part for in-flight shutdown in this type of aeroengine. Macro observation, fractography analysis, metallography analysis and hardness test were conducted on the failed counterweight assembly. The result shows that failure mechanism of counterweight block and washer is fatigue. The washer failure is likely due to inappropriate heat treatment process and continuous impact in flight by slightly tilted roller. Counterweight material loss is attributed to stress concentration, low structure strength and impact came from the tilted roller. Finally some safety suggestion on design and maintenance is given.

Metallographic and Materials Evaluation of a Cracked Radial Steam Turbine Rotor

2018 ◽  
Author(s):  
Vamadevan Gowreesan ◽  
Wayne Greaves
Keyword(s):  
Steam Turbine ◽  
Manganese Sulfide ◽  
Turbine Rotor ◽  
Impact Testing ◽  
Composition Analysis ◽  
Tempered Martensite ◽  
Material Defects ◽  
Fracture Appearance Transition Temperature ◽  
Fracture Appearance ◽  
High Level

A radial steam turbine developed cracks after 220,000 hours of service. The rotor had an integral disc with eight rows of blades, and a short stub. Nine inlets on the disc channeled steam from one side to the other, and then radially outward. Analysis of the fracture surface revealed cracks originating in some of the inlet holes, and propagating by fatigue. No material defects were found at the crack initiation sites. Hardness and microstructure (optical) across the disc were uniform, but chemical composition analysis of the alloy revealed high level of phosphorus and sulfur. In addition, the microstructure consisted of uniformly tempered martensite with manganese sulfide stringers. Although tensile properties were normal, impact testing indicated embrittlement by a shift in Fracture Appearance Transition Temperature (FATT). Metallurgical evidence of embrittlement was also found. It was concluded that service induced cyclic loading in combination with reduced crack resistance caused by embrittlement lead to cracking.

Identification of Human Errors During Early Design Stage Functional Failure Analysis

2018 ◽  
Author(s):  
Lukman Irshad ◽  
Salman Ahmed ◽  
Onan Demirel ◽  
Irem Y. Tumer
Keyword(s):  
Failure Analysis ◽  
Human Error ◽  
System Level ◽  
Design Stage ◽  
Human Factors Engineering ◽  
Human Errors ◽  
Functional Failure ◽  
Early Design ◽  
Early Design Stage ◽  
Early Design Stages

Detection of potential failures and human error and their propagation over time at an early design stage will help prevent system failures and adverse accidents. Hence, there is a need for a failure analysis technique that will assess potential functional/component failures, human errors, and how they propagate to affect the system overall. Prior work has introduced FFIP (Functional Failure Identification and Propagation), which considers both human error and mechanical failures and their propagation at a system level at early design stages. However, it fails to consider the specific human actions (expected or unexpected) that contributed towards the human error. In this paper, we propose a method to expand FFIP to include human action/error propagation during failure analysis so a designer can address the human errors using human factors engineering principals at early design stages. To explore the capabilities of the proposed method, it is applied to a hold-up tank example and the results are coupled with Digital Human Modeling to demonstrate how designers can use these tools to make better design decisions before any design commitments are made.

scholarly journals Numerical Simulation of Cascade Flow: Vortex Element Method for Inviscid Flow Analysis and Axial Turbine Blade Design

2021 ◽  
Vol 85 (2) ◽  
pp. 14-23
Author(s):  
Nono Suprayetno ◽  
Priyono Sutikno ◽  
Nathanael P. Tandian ◽  
Firman Hartono
Keyword(s):  
Best Practice ◽  
Lift Coefficient ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Inviscid Flow ◽  
Turbine Rotor ◽  
Design Stage ◽  
Outer Diameter ◽  
Axial Turbine ◽  
Cascade Flow

This study aims to design an axial turbine rotor blade and predict the turbine performance at preliminary design stage. Quasi three dimensional method was applied to design including blade to blade flow analysis. The blade profile uses a NACA 0015 airfoil by varying the profile thickness from hub to tip. The profile is divided into eleven segments which has different parameters. The profile was analysed using blade to blade flow/cascade flow analysis called vortex panel method to obtain lift coefficient. The analysis of cascade flow was performed in potential flow and prediction of turbine perfomance is carried out involving common best practice to give drag effect on the blade. The design of the turbine was applied on three different rotors, which also have a different discharge, head, and design rotation. The outer diameter of turbine 1 is 0.65 m, while turbine 2 and turbine 3 have an outer diameter of 0,60 m. The calculation result show that the efficiency of turbines 1, 2, and 3 were 88,32%, 89,67%, and 89,04%, respectively.

scholarly journals Development of Novice Teacher Induction Program Model in Sleman Regency, Indonesia

2019 ◽  
Author(s):  
Maria Dominika Niron ◽  
Lia Yuliana ◽  
Pandit Isbianti ◽  
Baiquni Rahmat
Keyword(s):  
Data Analysis ◽  
Primary School ◽  
Teacher Induction ◽  
Novice Teacher ◽  
Needs Analysis ◽  
Design Stage ◽  
Program Model ◽  
Implementation Phase ◽  
Induction Program ◽  
Product Forms

The study aims to identify and develop Novice Teacher Induction Program Model in SlemanRegency,Indonesia.ThisstudyusedthemethodofResearchandDevelopment BorgandGall.Inthisstudy,ResearchandDevelopmentwassimplifiedintofourstages from ten steps, namely: (1) the preliminary stage which is the initial research stage and gathering information about the implementation of Primary School Novice Teacher Induction Program (PIGP), (2) planning of Primary School Novice Teacher Induction Program (PIGP) as the development of initial product forms, (3) testing, evaluation and revision stages through assessment of model and product feasibility and limited testing, and (4) implementation phase of Novice Teacher Induction Program (PIGP) for Primary school. The data collection techniques used include: (1) Focus Group Discussion (FGD), (2) observation, (3) interviews, and (4) documentation studies. Next, quantitative and qualitative data analysis were used as data analysis techniques in this research. The study revealed that the development of Novice Teacher Induction Program (PIGP) was carried out in four stages: 1) the stage of designing the model and design, 2) expert validation, 3) testing, and 4) program implementation. At the design stage, the model is designed based on the results of the study and needs analysis of the PIPG model. Based on the results of the needs analysis, the school has a variety of mentoring techniques for novice teachers. However, in general the guidance of the learning process or counseling is carried out by the principal and senior teacher.

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