Response to comments on ‘effect of prior processing on the performance of PH 13-8 Mo stainless steel helicopter components’

Conclusion The conclusions drawn for this investigation seemed appropriate from the results obtained. It is true that machining may have played a role in the components tested at AATD, but ARL does not feel this was the root cause of the premature “C” rod failures.     

,,... die Biologie als die Krone oder der höchste Strebepunct aller Wissenschaften.“

During the first decade after the publication of the first volume of Treviranus’ fundamental work Biologie oder Philosophie der lebenden Natur (6 vols, 1802–1822), three German naturalists and physicians – Oken, Bartels, and Carus, all inspired by the natural philosophy of Schelling –, used the term “biology” in the titles of some of their books.An analysis of these works shows, that their objective was somewhat different from what Treviranus himself had intended. In contrast to Treviranus’ idea of a “doctrine of life”, which should be separated as a discipline from the physical sciences, they generated the conception that also the universe is a living thing.This preoccupation of the term biology by the Naturphilosophen was just a short interplay in what may be called the period of “romantic biology”.Yet it is not improbable that this romantic notion of “biology” may have been an major obstacle to the formation of the academic discipline biology.     

Pressurized 3-piece steel container explosions and failure mechanisms

The design of 3-piece steel pressurized containers includes double seams that connect the bottom and top of the container to the container body. These seams have some inherent design features, such as crevices, that can lead to corrosion and other forms of failure. Since the 3-piece containers are pressurized with liquefied propellants, such as propane, failure can lead to catastrophic separation of the top or bottom from the body. This creates a “rocket” effect with the potential to cause serious personal injury and/or property damage. This paper presents the analysis of several such failures and demonstrates that corrosion, weld cracking, and stress concentrations act to cause sudden, unexpected, explosive failures. Several changes in construction that could minimize the tendency for explosion are also discussed.     

The role of materials science in the investigation of electrical and electronic failures

A poultry barn, housing a quarter million chickens, burns to the groun. An apartment complex burns and human lives are lost. A utility company installs cables for a new plant but when construction is halfway completed, the insulation on the cables is discovered to be faulty. These examples are typical of the failures that a forensic engineer may be asked to investigate. The term “forensic” is often thought to imply a criminal investigation but in many, if not most, cases the investigations are for civil, rather than crminal, purposes. The term “forensic” merely implies that some type of litigation is either ongoing or contemplated.     

The efficacy of a test and ESS program

Statistical results of all the 1621 failure analyses, which cover a four‐year effort, are presented. The failure analyses were part of an elaborate test and ESS process of a high‐reliability system. Of the failure analyses, 97.5% identified the root cause. The classification of the failures by 11 root cause classes, including the test and ESS process itself is provided. The distribution of failure root causes detected during the various phases of the process is shown. Each test phase was analyzed according to the share of failures found and the fraction of failures that occurred during that phase. Applying a linear formula that summarizes the relative efficacy of each test phase compares the performances of the various phases. The term efficacy is used to describe the ability of a test phase to reveal failures without generating new problems. Copyright © 2002 John Wiley & Sons, Ltd.     

Numerical investigation of intercoupling vibration of a mistuned turbomachinery compressor rotor wheel

Results of numerical experiments involving the determination of possible causes of disk rim failure of a rotor wheel with blades, having the root of a dovetail joint type, are presented. The theory of coupling vibration of mechanical systems is used to elucidate the cause of rather high vibration stresses in the disk rim. Numerical investigation into the influence of specific features of the natural vibration spectrum of the rotor wheel as a system with cyclic symmetry and of the blade frequencies mistuning upon resonant vibrations have been performed. The investigation has been performed in the framework of the project “Development of Methods for Lowering the Level of Vibration Stresses in GTE Parts” of the State Scientific and Technical Program “Enhancing the Dependability and Life of Machines and Structures”. Translated from Problemy Prochnosti, No. 2, pp. 67–78, March–April, 1997.     

Counting on Fatigue: Striations and Their Measure

Fatigue has been the subject of innumerable books, papers, and studies since the late 1800s and continues to be a major factor in component failure with an estimated 90% of all mechanical failures being attributed to fatigue (Dieter, Mechanical metallurgy, 1976). The classic fatigue “thumbnail” often visible to the naked eye may allege fatigue, but microscopic striations—tiny ridges that bear immutable witness to cyclical loading—pronounce the verdict. As such, counting striations should provide the analyst with valuable information regarding the loading regimen, the time to failure, and insight into events that gave birth to fracture. This paper presents both pros and cons of striation counting and discusses striation count accuracy. It also presents practical techniques for use in fatigue striation counting based on laboratory experience and observation.     

Failure analysis of A286 carrier panel fasteners

The observation that carrier panel fasteners recovered from the Columbia appeared to have fractured with minimal macroscopic ductility led to concern that stress-corrosion cracking (SCC) or other age-related degradation processes in the A286 bolts may have been the cause of failure during re-entry. To assess this hypothesis, several recovered fasteners having a brittle fracture appearance and several fasteners that fractured in a more ductile mode were analyzed. The results provided the information necessary to discount the “stress-corrosion” hypothesis and conclude that the fasteners failed by some unidentified tensile load after being weakened by high-temperature grain growth and liquid aluminum attack. This article is based on a presentation given on October 19, 2004, at the session on “The Space Shuttle Columbia: A Forensic Materials Perspective” as part of the Failure Analysis and Prevention Symposium at ASM International’s Materials Solutions Conference and Exposition in Columbus, Ohio.     

Failure analysis of three-piece steel aerosol cans

This paper explains how three-piece aerosol cans made from tin-plated steel are designed and manufactured, how they behave structurally, and provides information on doing failure analyses of aerosol cans. Particular emphasis is placed on the metallurgical aspects of the side-seam welding process used to create the body cylinders, the process of attaching the ends, and explains how three-piece aerosol cans made from tin-plated steel behave structurally. The paper also addresses a number of representations and conclusions presented in a paper by M. Fox and R. Hastings entitled “Pressurized 3-Piece Steel Container Explosions and Failure Mechanisms” published in the June 2003 issue of Practical Failure Analysis. Aerosol cans may fail, although not necessarily explode, by internal or external corrosion, by mechanical abuse (puncture, for example), or by being overheated. Understanding the design, manufacture, and structural behavior of these pressure vessels will aid in the formulation of conclusions as to the root causes of aerosol can failures.     

Columbia accident investigation board (CAIB) pathfinder analysis of item 33767

Early in the shuttle Columbia crash investigation, item 33767 was one of several “Pathfinder” components selected from the Columbia debris that exhibited damage patterns similar to those observed on the left wing airframe components, the components in which initial failure was thought to have occurred. “Pathfinder Analysis” sought to answer academic questions regarding the maximum heat attained and heating direction/duration and identify debris imposed on this fuselage section during Columbia breakup and re-entry. Traditional failure analysis techniques provided useful information on debris constituents and damage sequence and were successful in identifying heat effects, such as the presence of large thermal gradients across the component, and the existence of several failure modes that included hot tensile failure, hot bending failure, and rapid overload fracture. This article is based on a presentation given on October 19, 2004, at the session on “The Space Shuttle Columbia: A Forensic Materials Perspective” as part of the Failure Analysis and Prevention Symposium at ASM International’s Materials Solutions Conference and Exposition in Columbus, Ohio.     

Fatigue Failure of Flanged Thermowell

A fractured flanged thermowell was received for analysis. The fracture was located at the root of “U” insertion/immersion length which was welded to the flange. The failure of flanged thermowell was attributed to the vortex-induced fatigue. The failure was initiated by the weld failure to withstand the fluctuating load resulted from vortex after years of service. This weld failure then created stress raisers, as evidenced by the ratchet marks and river marks near the outer surface.     

SAO network analysis of patents for technology trends identification: a case study of polymer electrolyte membrane technology in proton exchange membrane fuel cells

This paper suggests a method for Subject–Action–Object (SAO) network analysis of patents for technology trends identification by using the concept of function. The proposed method solves the shortcoming of the keyword-based approach to identification of technology trends, i.e., that it cannot represent how technologies are used or for what purpose. The concept of function provides information on how a technology is used and how it interacts with other technologies; the keyword-based approach does not provide such information. The proposed method uses an SAO model and represents “key concept” instead of “key word”. We present a procedure that formulates an SAO network by using SAO models extracted from patent documents, and a method that applies actor network theory to analyze technology implications of the SAO network. To demonstrate the effectiveness of the SAO network this paper presents a case study of patents related to Polymer Electrolyte Membrane technology in Proton Exchange Membrane Fuel Cells.     

An exploratory study on substantive co-link analysis: A modification to total co-link analysis

Since the term “co-link” was put forward, many scholars have done exploratory investigations to prove the applicability and validity of co-link analysis used in mapping internet structure and mining relationships among internet colonies. All of these studies are based on the whole links in the web called “total co-link analysis”. However, there are both substantive and non-substantive links in the web, and the number of the latter outweights that of the former, which makes the preconditions of total co-link analysis untenable. In this paper, we present “substantive co-link analysis”, and believe it is more sound and valid than “total co-link analysis”. Then exploratory investigations on both total and substantive co-link analysis are carried out with the sample of 20 academic blogs on Library and Information Science, the results of which testify our assumption that “substantive co-link analysis” is more efficient and reasonable than “total co-link analysis”.     

The C-H delayed failure mechanism revisited

The often cited “Charles–Hillig” model of delayed failure assumes that corrosive attack on existing flaws in glass is controlled by interactions involving the moisture in the environment, which leads to time and stress dependent failure. The analysis by Inglis of the stress multiplication at a rounded end of a flaw is combined with stress-dependent chemical kinetics and thermodynamics. Failure occurs when the tip stress reaches the ultimate strength of the glass. The model provides a physical interpretation of the empirical “Universal Fatigue Law.” When sufficient data is available, it also provides an algorithm that allows a precise determination of the minimum stress needed to induce time-dependent failure. This model is compared with the competing LEFM model.     

Failure Analysis of Horizontal Hinge Pin Components from an Army Cargo Helicopter

A horizontal hinge pin (HHP) assembly from an Army cargo helicopter was examined to determine the root cause of ring and roller fracture and spalling. Chemical analyses, metallography and hardness testing indicated that the rings and rollers conformed to the material requirements of the governing drawing. Metallography and visual and scanning electron microscopy indicated the failure likely initiated in the lag ring due to rolling contact fatigue (RCF) because of high service loads. Evidence of subsurface crack initiation was observed. This article was originally published as “Failure Analysis of a Ring and Rollers from an Army Cargo Helicopter Rotary Wing Head Lag Horizontal Hinge Pin” in Integration of Machinery Failure Prevention Technologies into Systems Health Management, Proceedings of the 61st Meeting of the Society for Machinery Failure Prevention Technology, Society for Machinery Failure Prevention Technology, 2007, pp. 249–259, and is reprinted with permission.     

Conductive filament formation in printed circuit boards: effects of reflow conditions and flame retardants

Conductive filament formation, a major cause of failures in printed circuit boards, is an electrochemical process that involves the transport of a metal through or across a nonmetallic medium under the influence of an applied electric field. With an increasing potential to market “green” electronics, environmental and health legislations, and the advent of lead-free and halogen-free initiatives, newer types of printed circuit board materials are being exposed to ever higher temperatures during solder assembly. The higher temperatures can weaken the glass-fiber bonding, thus enhancing conductive filament formation. The effects of the inclusion of halogen-free flame retardants on conductive filament formation in printed circuit boards are not completely understood. Previous studies, along with analysis and examinations conducted on printed circuit boards with failure sites that were due to conductive filament formation, have shown that the conductive path is typically formed along the delaminated fiber glass and epoxy resin interfaces. This paper is a result of a year-long study on the effects of reflow temperatures, halogen-free flame retardants, glass reinforcement weave style, and conductor spacing on times to failure due to conductive filament formation.     

Dielectric Breakdown Elimination Via Particulate Additives

In many materials, strong electrical fields can cause highly conductive pathways to occur due to dielectric breakdown, which can cause the material to “jump” to a higher permittivity state. This effect is often undesirable and can lead to electrically-induced failure of a device, for example due to overheating. The overall goal of this work is to estimate the volume fraction and properties of the particulate additives needed to reduce the electrical load carried by a bulk material, in order to avoid dielectric breakdown.     

The mechanical behaviour of polyimide-copper laminates

The peel energies of flexible laminates consisting of polyimide films bonded to copper foil with a polymeric adhesive have been measured and the peel mechanisms investigated by conducting peel tests inside a scanning electron microscope. These laminates were prepared from polyimide films that had been subjected to either a “high-thermal history” or “low-thermal history” treatment during the production of the film. The laminates prepared from the “high-thermal history” polyimide films had higher recorded peel energies and the locus of failure during the peel test was mainly by cohesive fracture through the adhesive layer. The laminates prepared from the “low-thermal history” polyimide films tended to fail in a weak boundary layer of the polyimide film. The peel energies were lower and displayed a greater scatter. Thein situ peel tests have also identified various failure mechanisms which account for the different features observed on the peeled surfaces and the various types of peel energy traces which were recorded.     

Practical interpretation of metrological traceability on gauge block as to VIM 3

In ISO/IEC Guide 99:2007, i.e. the International Vocabulary of Basic and General Terms in Metrology-3rd edition (VIM 3), the term “traceability” is replaced by “metrological traceability”, giving it a new definition as property of a measurement result which can be related to a reference. In essence, “metrological traceability” can offer an evidence of measurands tracing to the primary standards which can realize the SI units, and offer a documented unbroken chain of calibrations, thus considered as one of the most important terms in VIM 3. National Measurement Laboratory (NML, Chinese Taipei) has long operated its main mission of calibration implemented along with peer assessed traceability of its measurement systems, which demonstrate a calibration hierarchy conventionally in schematic approach. In dealing with definition of the new term “metrological traceability” in VIM 3, this paper elaborates in taking additionally a newly mathematical approach rather than schematic approach only to realize the practical interpretation of “metrological traceability” to show how the unbroken calibration chain is functioning seamless and robust on the gauge block measurement system in NML. Through such study activities, we well assure our strong confidence on technology inheritance of gauge block and the other measurement systems with sufficient metrological know-how in NML, which can continually pass to each entry level metrologist.