Irem Y. Tumer

The Function-Failure Design Method

To succeed in the product development market today, firms must quickly and accurately satisfy customer needs while designing products that adequately accomplish their desired functions with a minimum number of failures. When failure analysis and prevention are coupled with a products design from its conception, potentially shorter design times and fewer redesigns are necessary to arrive at a final product design. In this article, we explore the utility of a novel design methodology that allows failure modes and effects analysis (FMEA)-style failure analysis to be conducted during conceptual design. The function-failure design method (FFDM) guides designers towards improved designs by predicting likely failure modes based on intended product functionality.

A Graph-Based Fault Identification and Propagation Framework for Functional Design of Complex Systems

In this paper, the functional-failure identification and propagation (FFIP) framework is introduced as a novel approach for evaluating and assessing functional-failure risk of physical systems during conceptual design. The task of FFIP is to estimate potential faults and their propagation paths under critical event scenarios. The framework is based on combining hierarchical system models of functionality and configuration, with behavioral simulation and qualitative reasoning. The main advantage of the method is that it allows the analysis of functional failures and fault propagation at a highly abstract system concept level before any potentially high-cost design commitments are made. As a result, it provides the designers and system engineers with a means of designing out functional failures where possible and designing in the capability to detect and mitigate failures early on in the design process. Application of the presented method to a fluidic system example demonstrates these capabilities.

A SURVEY OF AIRCRAFT ENGINE HEALTH MONITORING SYSTEMS

This paper presents a survey of engine health monitoring systems for commercial aircraft. The state of practice is explored first, with the purpose of identifying the shortcomings of current systems. The state of the research to address these shortcomings is them surveyed to explore the alternatives. Research and monitoring applications for various other types of engines provide a good basis for further exploring the topic. This survey is meant to serve as a precursor to engine health and monitoring research at the NASA Ames Research Center.

The risk in early design method

Risk assessments are necessary to anticipate and prevent accidents from occurring or repeating. Current probabilistic risk assessment methods require mature design proposals to analyse. Since product safety and reliability are affected the most by decisions made during the early design phases, a risk assessment that can be performed with less mature data during these design phases is needed. This study focuses specifically on the relationship between function and risk in early design by presenting a mathematical mapping from product function to risk assessments that can be used in the conceptual design phase. An investigation of a spacecraft orientation subsystem is used to demonstrate the mappings. The results from the study and its spacecraft application yield a preliminary risk assessment method that can be used to identify and assess risks as early as the conceptual phase of design. The preliminary risk assessment presented in this paper is a tool that will aid designers by identifying risks as well as reducing the subjectivity of the likelihood and consequence value from a risk element, will provide four key risk element properties (design parameter, failure mode, likelihood, and consequence) for numerous risk elements with simple calculations, and will provide a means for inexperienced designers to effectively address risk in the conceptual design phase.

Risk-Based Decision-Making for Managing Resources During the Design of Complex Space Exploration Systems

Complex space exploration systems are often designed in collaborative engineering environments where requirements and design decisions by various subsystem engineers have a great impact on the overall risk of the mission. As a result, the system-level management should allocate risk mitigation resources (e.g., capital to place additional sensors or to improve the current technology) among various risk elements such that the main objectives of the system are achieved as closely as possible. Minimizing risk has been long accepted as one of the major drivers for system-level decisions and particularly resource management. In this context, Risk-Based Decision Making refers to a process that allocates resources in such a way that the expected risk of the overall system is minimized. This paper presents a new risk-based design decision-making method, referred to as Risk and Uncertainty Based Concurrent Integrated Design Methodology or RUBIC Design Methodology for short. The new approach is based on concepts from portfolio optimization theory and continuous resource management, extended to provide a mathematical rigor for risk-based decision-making during the design of complex space exploration systems. The RUBIC design method is based on the idea that a unit of resource, allocated to mitigate a certain risk in the system, contributes to the overall system risk reduction in the following two ways: (1) by mitigating that particular risk; and (2) by impacting other risk elements in the system (i.e., the correlation among various risk elements). RUBIC then provides a probabilistic framework for reducing the expected risk of the final system via optimal allocation of available risk-mitigation resources. The application of the proposed approach is demonstrated using a satellite reaction wheel example.

The Risk in Early Design (RED) Method: Likelihood and Consequence Formulations

This study focuses specifically on the relationship between function and risk in early design by presenting a mathematical mapping from product function to likelihood and consequence risk assessments that can be used in the conceptual design phase. An investigation of a spacecraft orientation subsystem is used to demonstrate the proposed mappings. The risk assessment presented in this paper is a tool that will aid designers by identifying risks as well as reducing the subjectivity of the likelihood and consequence value from a risk element, provide four key risk element properties (design parameter, failure mode, likelihood, and consequence) for numerous risk elements with a simple calculation, and provide a means for inexperienced designers to effectively address risk in the conceptual design phase. The investigation demonstrates that the method presented in this paper is a useful tool for preliminary identification and assessment of product risks.Copyright

Analysis of Triaxial Vibration Data for Health Monitoring of Helicopter Gearboxes

Research on the nature of the vibration data collected from helicopter transmissions during flight experiments has led to several crucial observations believed to be responsible for the high rates of false alarms and missed detections in aircraft vibration monitoring systems. This work focuses on one such finding, namely, the need to consider additional sources of information about system vibrations. In this light, helicopter transmission vibration data, collected using triaxial accelerometers, are explored in three different directions, analyzed for content, and then combined using Principal Components Analysis (PCA) to analyze changes in directionality. The frequency content of the three different directions is compared and analyzed using time-synchronously averaged vibration data. To provide a method for analysis and monitoring purposes, the triaxial data are decorrelated using a mathematical transformation, and compared to the original axes to determine their differences. The benefits of using triaxial data for vibration monitoring and diagnostics are explored by analyzing the changes in the direction of the principal axis of vibration formed using all three axes of vibration. The statistical variation introduced due to the experimental variables is further analyzed using an Analysis of Variance approach to determine the effect of each variable on the overall signature. The results indicate that triaxial accelerometers can provide additional information about the frequency content of helicopter gearbox vibrations, and provide researchers and industry with a novel method of capturing and monitoring triaxial changes in the baseline vibration signatures.

A FRAMEWORK FOR CREATING A FUNCTION-BASED DESIGN TOOL FOR FAILURE MODE IDENTIFICATION

Knowledge of potential failure modes during design is critical for prevention of failures. Currently industries use procedures such as Failure Modes and Effects Analysis (FMEA), Fault Tree analysis, or Failure Modes, Effects and Criticality analysis (FMECA), as well as knowledge and experience, to determine potential failure modes. When new products are being developed there is often a lack of sufficient knowledge of potential failure mode and/or a lack of sufficient experience to identify all failure modes. This gives rise to a situation in which engineers are unable to extract maximum benefits from the above procedures. This work describes a function-based failure identification methodology, which would act as a storehouse of information and experience, providing useful information about the potential failure modes for the design under consideration, as well as enhancing the usefulness of procedures like FMEA. As an example, the method is applied to fifteen products and the benefits are illustrated.

Prescribing and Implementing the Risk in Early Design (RED) Method

To aid designer’s abilities to increase product safety and reliability, risk assessments need to be moved forward to the conceptual design phase of a product. This is especially difficult because often the product has not assumed a physical form in this design stage. In an effort to perform risk assessments based on function, rather than physical components, the risk in early design (RED) method was developed. This paper presents the function based mathematical mappings of the RED method for preliminary risk assessments based on catalogued historical failure information. An example of the RED preliminary risk assessments on a thermal control subsystem along with heuristics for applying the particular types of risk assessments are discussed. Finally, the steps for performing RED in the conceptual design phase are offered. The heuristics and steps for preliminary risk assessments shown offer a method for identifying potential areas of concern in a product during the early stages of design when much can be done to over come them.Copyright

Integrating Life Cycle Assessment Into the Conceptual Phase of Design Using a Design Repository

This paper describes efforts taken to further transition life cycle assessment techniques from the latter, more detailed phases of design to the early-on conceptual phase of product development. By using modern design methodologies such as automated concept generation and an archive of product design knowledge, known as the Design Repository, virtual concepts are created and specified. Streamlined life cycle assessment techniques are then used to determine the environmental impacts of the virtual concepts. As a means to benchmark the virtual results, analogous real-life products that have functional and component similarities are identified. The identified products are then scrutinized to determine their material composition and manufacturing attributes in order to perform an additional round of life cycle assessment for the actual products. The results of this research show that sufficient information exists within the conceptual phase of design (utilizing the Design Repository) to reasonably predict the relative environmental impacts of actual products based on virtual concepts.