Search Results for fractional factorial design

This article presents an approach to manage the uncertainty present in materials design. It describes inductive and deductive approaches to deal with uncertainty. The article focuses on providing an understanding of the opportunities for managing uncertainty and the decisions that influence the accuracy of the results. A design of experiments (DOE) represents a sequence of experiments to be performed, expressed in terms of factors set at specified levels. The article discusses the two types of DOEs: the full factorial design and the fractional factorial design. It explains the factors to be considered when selecting a procedure for propagating uncertainty. The article lists the categories of the popular types of uncertainty propagation methods, including simulation-based methods, local expansion methods, and numerical integration-based methods.

Planning of experiments does not consist merely of identifying a few key parameters and then selecting a specific plan. Selection of the proper experimental plan depends on the purpose of the experiment, physical restrictions on the taking of measurements, and other restrictions imposed by time, economic considerations, and materials and personnel availability. This article presents recommendations that should be followed in outlining the methods of conducting and analyzing an experiment to ensure successful results. It discusses restricted type of experiments, in which the experimenter varies the parameters, or factors, under study and then observes the effects of this action. These include factorial experiments, blocked factorial experiments, and fractional factorial experiments. The article describes the estimation of experimental errors and provides information on randomized designs and block designs. It also presents the methods for determining optimum conditions or levels.

This article describes methods that are oriented toward the analysis of planned cooperative experiments that involve multiple factors, blocks, and/or treatment levels. The experiments include factorial, fractional factorial, randomized block, and incomplete block experiments.

When planning a corrosion-testing program, it is advisable to select the testing conditions carefully in order to produce ranking parameters with minimal influence from testing conditions while rich in engineering significance. This article provides a discussion on test objectives, metal composition and metallurgical conditions, test specimen preparation, and corrosion damage assessment. It describes a strategy for planning the design of controlled and uncontrolled factorial experiments. The article contains a table that lists the elements of an iterative process for the experimental design. It illustrates the experimental designs applied to corrosion testing.

Reliability is a measure of the capacity of equipment or systems to operate without failure in the service environment. This article focuses on reliability in design and presents equations governing the instantaneous failure rate, general reliability function, mean time to failure, mean time between failures, and useful life period. The article describes the calculation of reliabilities for series and parallel arrangements of a complex system. It provides a comparison of probabilistic and deterministic design and concludes with a discussion on reliability growth.

Process optimization is the discipline of adjusting a process to optimize a specified set of parameters without violating engineering constraints. This article reviews data-driven optimization methods based on genetic algorithms and stochastic models and demonstrates their use in powder-bed fusion and directed energy deposition processes. In the latter case, closed-loop feedback is used to control melt pool temperature and cooling rate in order to achieve desired microstructure.

This article explains the key features of the manufacturing techniques for polymer composites. It describes the selection of a technically and economically feasible manufacturing technique for a composite design. The article discusses widely accepted and emerging techniques to manufacture polymer composites such as open-mold techniques.

Thermomechanical are used to gain insight into the causes of problems that arise during a given thermomechanical process. This article provides examples to demonstrate how significant the parameters were selected for specific tests. It examines the types of problems that can occur during a thermomechanical process. The article provides information on the thermophysical properties, which include specific heat, coefficient of thermal expansion, thermal conductivity/diffusivity, and density. It concludes with examples that illustrate how the various considerations in testing are successfully used to solve practical thermomechanical processing problems.

This article describes design factors for products used in engineering applications. The article groups these factors into three categories: functional requirements, analysis of total life cycle, and other major factors. These categories intersect and overlap, constituting a major challenge in engineering design. Performance specifications, risk and hazard analysis, design process, design for manufacture and assembly, design for quality, reliability in design, and redesign are considered for functional requirements. Life-cycle analysis considers raw-material extraction from the earth and product manufacture, use, recycling (including design for recycling), and disposal. The other major factors considered include evaluation of the current state of the art for a given design, designing to codes and standards, and human factors/ergonomics.

Statistics are extremely important tools in the operation of press shops, providing numerical process analysis capabilities. The most common use of statistics in the press shop is statistical process control (SPC) that uses statistical techniques such as control charts to analyze a process or its output to enable appropriate actions to be taken to achieve and maintain a state of statistical control. This article discusses the role of statistics in sheet metal forming operations, both in terms of SPC techniques, such as control charting, statistical deformation control, and experimental design, including single-variable studies, multivariable studies, and Taguchi experiments.

Concurrent engineering is product development that is done by concurrently utilizing all of the relevant information in making each decision. This article discusses the three aspects that must be taken into account for all product development decisions. The aspects include product functionality, production capability, and field-support capability. The concurrent process is carried out by a multifunctional team that integrates the specialties. The article schematically illustrates product design team configurations with subsystem teams and team of subsystem leaders. It discusses the three-step decision-making process, such as requirements, concepts, and improvement, followed by multifunctional product development teams. The article describes the two types of requirements development by multifunctional teams, namely, quality function deployment and functional analysis. It schematically illustrates the integration of product requirements and concept development. The article concludes with a discussion on the improvement of concepts in terms of robust design and mistake minimization.

This article provides an outline of the issues to consider in performing a probabilistic life assessment. It begins with an historical background and introduces the most common methods. The article then describes those methods covering subjects such as the required random variable definitions, how uncertainty is quantified, and input for the associated random variables, as well as the characterization of the response uncertainty. Next, it focuses on specific and generic uncertainty propagation techniques: first- and second-order reliability methods, the response surface method, and the most frequently used simulation methods, standard Monte Carlo sampling, Latin hypercube sampling, and discrete probability distribution sampling. Further, the article discusses methods developed to analyze the results of probabilistic methods and covers the use of epistemic and aleatory sampling as well as several statistical techniques. Finally, it illustrates some of the techniques with application problems for which probabilistic analysis is an essential element.

This article begins with a discussion on the driving forces for recycling composites. It reviews the recycling process of thermoset-matrix composites and thermoplastic-matrix composites. The recycling of thermoset-matrix composites includes regrind, chemical, energy recovery, and thermal processes. Thermoplastic-matrix composites are recycled by regrinding, compounding/blending and reprocessing. The article concludes with discussion on the properties of recycled composite fibers.

This article briefly introduces the concepts of failure analysis and root cause analysis (RCA), and the role of failure analysis as a general engineering tool for enhancing product quality and failure prevention. It reviews four fundamental categories of physical root causes, namely, design deficiencies, material defects, manufacturing/installation defects, and service life anomalies, with examples. The article describes several common charting methods that may be useful in performing an RCA. It also discusses other failure analysis tools, including review of all sources of input and information, people interviews, laboratory investigations, stress analysis, and fracture mechanics analysis. The article concludes with information on the categories of failure and failure prevention.

The major benefit of the implementation of the corrosion-control technologies at Army installations is the extension of the service life of buildings and other structures. This article reviews the exposure of military facilities and equipment to a wide variety of environmental conditions, including soils, waters, or atmospheres of varying corrosivity. It presents the case studies illustrating typical examples of the types of corrosion problems found on military installations. The article describes the various corrosion-control technologies used in military facilities. These include protective coatings and linings, cathodic protection, advanced materials selection and design, water treatment, equipment inspection and monitoring, and below-grade moisture mitigation.

This article begins with a description of the advantages and disadvantages of thermal spraying. It provides a discussion on the importance of substrate processing prior to coating and the role of undercutting in repair. The article reviews the steps for substrate preparation, namely, cleaning, roughening, masking, and preheating. Information on the equipment and process variables of dry abrasive grit blasting are also provided. The article describes the roles of spray stream and the spray pattern for all thermal spray processes. It discusses the defects arising from poor temperature control and from the variables influencing the manipulation of the spray torch. The article concludes with helpful information on calculating the process efficiency of thermal spraying.

This article describes the presses, transportation equipment, and manufacturing processes associated with cogging. It discusses the practical and metallurgical issues encountered during the conversion of ingot to billet. The article explains the use of numerical modeling as part of the continuing efforts to reduce the cost and time associated with developing new cogging sequences, increase the yield, make the processes more robust, and increase the quality of the produced product.

This article describes the general concepts and practices related to manufacturing and design. It discusses the activities of design and manufacturing by placing it in the context of the business system that they support. The article presents an overview of the manufacturing technology field from a design and material selection perspective. It provides an insight to the complex relationship among design, material selection, and manufacturing. The article offers information on modern design for manufacturing practices that are widely used in the industry.

This article illustrates the use of the American Petroleum Institute (API) 579-1/ASME FFS-1 fitness-for-service (FFS) code (2020) to assess the serviceability and remaining life of a corroded flare knockout drum from an oil refinery, two fractionator columns affected by corrosion under insulation in an organic sulfur environment, and an equalization tank with localized corrosion in the shell courses in a chemicals facility. In the first two cases, remaining life is assessed by determining the minimum thickness required to operate the corroded equipment. The first is based on a Level 2 FFS assessment, while the second involves a Level 3 assessment. The last case involves several FFS assessments to evaluate localized corrosion in which remaining life was assessed by determining the minimum required thickness using the concept of remaining strength factor for groove-like damage and evaluating crack-like flaws using the failure assessment diagram. Need for caution in predicting remaining life due to corrosion is also covered.

This article briefly introduces the concepts of failure analysis, including root-cause analysis (RCA), and the role of failure analysis as a general engineering tool for enhancing product quality and failure prevention. It initially provides definitions of failure on several different levels, followed by a discussion on the role of failure analysis and the appreciation of quality assurance and user expectations. Systematic analysis of equipment failures reveals physical root causes that fall into one of four fundamental categories: design, manufacturing/installation, service, and material, which are discussed in the following sections along with examples. The tools available for failure analysis are then covered. Further, the article describes the categories of mode of failure: distortion or undesired deformation, fracture, corrosion, and wear. It provides information on the processes involved in RCA and the charting methods that may be useful in RCA and ends with a description of various factors associated with failure prevention.