Failure Modes

An FMEA (Failure Mode and Effect Analysis) is a systematic method of identifying and preventing product and process problems before they occur. FMEAs are focused on preventing defects, enhancing safety, and increasing customer satisfaction. Ideally, FMEAs are conducted in the product design or process development stages, although conducting an FMEA on existing products and processes can also yield substantial benefits. FMEA is used in the manufacturing industry to improve production quality and productivity by reducing potential reliability problems early in the development cycle where it is easier to take actions to overcome these issues, thereby enhancing reliability through design. It is a method that evaluates possible failures in the system, design, process or service. In this paper, Failure mode and Effect Analysis is done on the process of Punching. A series of punching operation is done on various work pieces and the defects are found. Based on the evidence found, the ratings are given and risk priority number is given. Based on the RPN, the preventive measures are given. The FMEA is a proactive approach in solving potential failure modes. These works serve as a failure prevention guide for those who perform the punching operation and works towards effective punching operation.

Turnout system is one of the most critical infrastructures in the railway operations. As high demand in railway operation, the railway operators have to increase the axle load, traffic density and speed of the operation. These would be able to give high impact to the turnout system as increasing the vibration level and noise when the rolling stock crossing the turnout. Therefore, any failure in turnout system can cause negative impact to the operation in scope of maintenance cost and catastrophic consequence effect from the failure could happen such as major derailment. Safety-based maintenance (SBM) approach is an effective maintenance that takes safety into account in the maintenance by analysing the probability of the failure occurrence and severity of the consequence. Safety analysis is to ensure that the probabilities of the failure occurrence and the consequence from the failure such as death or injury and damage or loss of property can be minimised as to a level that is as low as reasonably practicable (ALARP). In this study, SBM and ALARP will be used to demonstrate the optimisation of geometry restoration activities of the railway turnout, which is essential for the safety requirements and quality standards. The failure behaviour in different operational environment such as effect of temperature, humidity, snow, dust, corrosive environment and natural calamity will be analysed to form fault tree analysis and establish a safety-based maintenance approach that is practical and useful for railway industry.

In this paper an approach for obtaining depth and section modulus of the cantilever sheet pile wall using inverse reliability method is described. The proposed procedure employs inverse first order reliability method to obtain the design penetration depth and section modulus of the steel sheet pile wall in order that the reliability of the wall against failure modes must meet a desired level of safety. Sensitivity analysis is conducted to assess the effect of uncertainties in design parameters on the reliability of cantilever sheet pile walls. The analysis is performed by treating back fill soil properties, depth of the water table from the top of the sheet pile wall, yield strength of steel and section modulus of steel pile as random variables. Two limit states, viz., rotational and flexural failure of sheet pile wall are considered. The results using this approach are used to develop a set of reliability based design charts for different coefficients of variation of friction angle of the backfill (5%, 10% and 15%). System reliability considerations in terms of series and parallel systems are also studied.

The November 15, 1967, loss of X-15 Flight 3-65-97 (hereafter referred to as Flight 3-65) was a unique incident in that it was the first and only aerospace flight accident involving loss of crew on a vehicle with an adaptive flight control system (AFCS). In addition, Flight 3-65 remains the only incidence of a single-pilot departure from controlled flight of a manned entry vehicle in a hypersonic flight regime. To mitigate risk to emerging aerospace systems, the NASA Engineering and Safety Center (NESC) proposed a comprehensive review of this accident. The goal of the assessment was to resolve lingering questions regarding the failure modes of the aircraft systems (including the AFCS) and thoroughly analyze the interactions among the human agents and autonomous systems that contributed to the loss of the pilot and aircraft. This document contains the outcome of the accident review.

Dual phase (DP) steels having a microstructure consists of a ferrite matrix, in which particles of martensite are dispersed, have received a great deal of attention due to their useful combination of high strength, high work hardening rate and ductility. In the present work, a microstructure based micromechanical model is developed to capture the deformation behavior, plastic strain localization and plastic instability of DP 590 steel. A microstructure based approach by means of representative volume element (RVE) is employed for this purpose. Dislocation based model is implemented to predict the flow behavior of the single phases. Plastic strain localization which arises due to incompatible deformation between the hard martensite and soft ferrite phases is predicted for DP 590 steel. Different failure modes arise from plastic strain localization in DP 590 steel are investigated on the actual microstructure by finite element method.

Cellular beams became increasingly popular as an efficient structural form in steel construction since their introduction. Their sophisticated design and profiling process provides greater flexibility in beam proportioning for strength, depth, size and location of circular holes. The purpose of manufacturing these beams is to increase the overall beam depth, the moment of inertia and section modulus, which results in greater strength and rigidity. The objective of this study is to carry out non-linear finite element (FE) analysis of the cellular beams that were considered in the experimental study in order to determine their ultimate load carrying capacity for comparison. The finite element method has been used to predict their entire response to increasing values of external loading until they lose their load carrying capacity. FE model of each specimen that is utilized in the experimental studies is carried out. FE models of steel cellular beams are used to simulate the experimental work to verify of test results and to investigate the non-linear behavior of failure modes such as web-post buckling, shear buckling and vierendeel bending of beams.

– This paper presents the first of two case studies conducted in 2009, to evaluate a concept for specifying and designing a Health Management System (HMS). This first case study made use of a representative Unmanned Aerial Vehicle fuel system. Conflicting information ...

Presents and discusses observed failure modes of a commercial off-the-shelf (COTS) database management system (DBMS) under the presence of transient operational faults induced by SWIFI (software-implemented fault injection). The Transaction Processing Performance Council (TPC) standard TPC-C benchmark and its associated environment is used, together with fault-injection technology, building a framework that discloses both dependability and performance figures. Over 1600 faults were injected in the database server of a client/server computing environment built on the Oracle 8.1.5 database engine and Windows NT running on COTS machines with Intel Pentium processors. A macroscopic view on the impact of faults revealed that: (1) a large majority of the faults caused no observable abnormal impact in the database server (in 96% of hardware faults and 80% of software faults, the database server behaved normally); (2) software faults are more prone to letting the database server hang or to causing abnormal terminations; (3) up to 51% of software faults lead to observable failures in the client processes

This paper presents an overview of reliability testing, reliability estimation, and prediction models. It also presents approaches for the design of test plans which result in providing failure data and/or degradation data in a limited test duration. Equivalence of different test plans which result in similar reliability estimates is also discussed. Use of degradation data for reliability estimates and maintenance

AbstractIn this paper, a new design approach for dissipative truss moment frames (DTMFs) able to guarantee, under seismic forces, the development of a yield mechanism of global type is presented and applied. In particular, DTMFs consist of a truss moment frame where the energy dissipation is provided by means of special devices located at the ends of the truss girders at the bottom chord level. The proposed design methodology is based on the kinematic theorem of plastic collapse. The method is based on the assumption that sections of truss elements and the yield threshold of dissipative parts (i.e., special devices) are known, and therefore the column sections are the unknowns of the design problem, which are obtained by imposing that the equilibrium curve corresponding to the global mechanism has to lie below those corresponding to all the possible mechanisms within a displacement range compatible with local ductility supply of dissipative elements. The design methodology has been implemented in a comput...

The presence of lithophysae in some units of Topopah Spring Tuff at Yucca Mountain, Nevada, the U.S. high level nuclear waste repository, have a detrimental effect on the engineering properties of the rock mass and its performance. The lithophysae were formed by pockets of gas trapped within the falling volcanic ash that formed the tuff units. The porosity associated with the lithophysae is termed macroporosity because of the large pore size as compared with traditional rock pores. In this paper, lithophysae-rich tuff and analog models (both cylindrical and cubic) made of plaster of Paris containing artificially created cavities were tested to assess the effect of macroporosity on both the uniaxial compressive strength and failure modes of the specimens. As expected, compressive strength decreases with increasing porosity due to lithophysae in tuff and cavities in plaster analog specimens. Failure modes of cylindrical specimens were also investigated. The failure modes observed were grouped into four distinct categories: spalling, axial splitting, shear failure and web failure. The failure modes transition from spalling through web failure as the percentage of macroporosity within the specimen increased.