Search Results for Pugh method

In materials selection, a decision matrix method refers to any formalized procedure by which materials are ranked prior to a selection decision. This article describes the advantages and limitations of decision matrix methods, as well as the steps involved, with examples. The methods include the Pugh method, the Dominic method, and the Pahl and Beitz method. The article discusses the three important concepts in decision making: alternatives (candidate materials), criteria (objectives), and weighting factors.

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 begins with a general review of the effects of changes in stress state on processing of materials. It describes the fundamentals of hydrostatic extrusion and reviews the various issues and benefits associated with hydrostatic extrusion. The article discusses the hydrostatic extrusion of structural alloys, composites, brittle materials, and intermetallics or intermetallic compounds, with examples. It concludes with a discussion on the attempts made to extend the hydrostatic extrusion to higher temperatures.

This article discusses the conceptual and configuration design of special-purpose parts that are designed and manufactured especially for use in a particular application. It provides a discussion on the issues considered in designing of parts, including, functionality; the relationship of the part to the whole assembly or subassembly; material and process selection; configuration; and tolerances. The article discusses the qualitative physical reasoning and qualitative reasoning that assist in developing part configuration alternatives.

This article discusses the basic approach for predicting the corrosion-fatigue life of structural components. It describes two types of tests that are normally used in combination: cycles-to-failure tests, which focus on crack initiation, and crack propagation tests, which focus on crack growth rates under cyclic load. The article examines corrosion-fatigue cracking along with the effects of cracking due to stress corrosion and hydrogen embrittlement, which often occur together. It explains how test parameters such as loading and environmental conditions impact crack growth mechanisms and data interpretation.

This article describes the incubation, nucleation, and propagation of stress-corrosion cracking and how to evaluate it using standard tests. It discusses constant-strain, constant-load, bending, and uniaxial tension testing and how they compare when evaluating smooth and precracked test specimens under elastic-strain, plastic-strain, and residual-stress conditions. The article provides guidance on specimen selection and preparation, strain rate, and test equipment. It also examines service and laboratory test environments and provides detailed information on how to test various steels and alloys and how to interpret test results.

Stress-corrosion cracking (SCC) is a phenomenon in which time-dependent crack growth occurs when the necessary electrochemical, mechanical, and metallurgical conditions exist. This article provides an overview of the environmental phenomenon, mechanisms, and controlling parameters of SCC. It describes the phenomenological and mechanistic aspects of the initiation and propagation of SCC. The article includes a phenomenological description of crack initiation and propagation that describes well-established experimental evidence and observations of stress corrosion. Discussions on mechanisms describe the physical process involved in crack initiation and propagation. The article also includes information on dissolution models and mechanical fracture models.

Materials selection is an important engineering function in both the design and failure analysis of components. This article briefly reviews the general aspects of materials selection as a concern in proactive failure prevention during design and as a possible root cause of failed parts. It discusses the overall concept of design and describes the role of the materials engineer in the design and materials selection process. The article highlights the significance of materials selection in both the prevention and analysis of failures.

Materials selection is closely related to the objectives of failure analysis and prevention. This article briefly reviews the general aspects of materials selection as a concern in both proactive failure prevention during design and as a possible root cause of failed parts. Coverage is more conceptual, with general discussions on the following topics: design and failure prevention, materials selection in design, materials selection for failure prevention, and materials selection and failure analysis. Because materials selection is just one part of the design process, the overall concept of design is discussed. The article also describes the role of the materials engineer in the design and materials selection process. It provides information on the significance of materials selection in both the prevention and analysis of failures.

Engineering design should result in a product that performs its function efficiently and economically within the prevailing legal, social, safety, and reliability requirements. This introductory article discusses some key considerations in design, material selection, and manufacturing that a materials engineer should take into account to satisfy such requirements. It includes a brief section on concurrent engineering, which companies use to ensure that all needed input is obtained and addressed concurrently throughout the product lifecycle, including material selection and processing, product design, cost analysis, manufacturing, recyclability, and performance.

This article focuses on direct extrusion processing where metal powders undergo plastic deformation, usually at an elevated temperature, to produce a densified and elongated form having structural integrity. It provides information on the basic powder extrusion processes and the mechanics of extrusion. The article also examines specific extrusion practices for the production of wrought material from powder stock and provides examples of materials processed by powder extrusion.

Mechanically assisted degradation of metals is defined as any type of degradation that involves a corrosion mechanism and a wear or fatigue mechanism. This article provides a discussion on the mechanisms of five forms of degradation: erosion, fretting corrosion, fretting fatigue, cavitation and water drop impingement, and corrosion fatigue. It describes the factors affecting the severity of fretting corrosion. The article also illustrates the relationship between corrosion fatigue and stress-corrosion cracking.

This article presents an overview of an engineering design process. Though the process is extremely complex, distinct stages of design activities are identified and described. The article illustrates guided iteration methodology that helps in problem solving in design. It describes the engineering conceptual design and configuration design of special-purpose parts. It discusses the parametric design methods of the parts and best practices that are used by successful firms to achieve the goals of quality, cost, time-to-market, and marketing flexibility.

Dealloying is a corrosion process in which one or more elements are selectively dissolved, leaving behind a porous residue of the remaining elements. This article describes the dealloying in various systems, namely, dezincification, graphitic corrosion, dealuminification, and noble metal alloys dealloying. The current-potential behavior of a binary alloy undergoing selective dissolution is reviewed. The article highlights the four mechanisms required for the formation of porous metals: ionization-redeposition, surface diffusion, volume diffusion, and percolation model of selective dissolution.

This article is a compilation of definition of terms related to materials selection and its integration with engineering design processes.

Geochemical modeling is being used to understand and predict scaling, susceptibility to corrosion, atmospheric corrosion rates, acid rain, corrosion film solubility, and environmental impacts of aqueous species in runoff. This article discusses the principles, limitations, and applications of the modeling. It explains how to calculate the chemical equilibrium in geochemical modeling and provides information on modeling features.

Fracture toughness is the ability of a material to withstand fracture in the presence of cracks. This article focuses on the use of fracture toughness as a parameter for engineering and design purposes. Both linear elastic and elastic-plastic fracture mechanics concepts are reviewed as they relate to fracture toughness and design process. The article explores the use of plane strain fracture toughness, crack-tip opening displacement, and the J-integral as the criteria for the design and safe operation of structures and mechanical components. It discusses the variables affecting fracture toughness, including yield strength, loading rate, temperature, and material thickness. A summary of different fatigue and fracture mechanics design philosophies and their relationship with fracture toughness is provided. The article concludes with information on the examples of fracture toughness in design.

Stress-corrosion cracking (SCC) is a cracking phenomenon that occurs in susceptible alloys, and is caused by the conjoint action of tensile stress and the presence of a specific corrosive environment. This article provides an overview of the anodic dissolution mechanisms and cathodic mechanisms for SCC. It discusses the materials, environmental, and mechanical factors that control hydrogen embrittlement and SCC behavior of different engineering materials with emphasis on carbon and low-alloy steels, high-strength steels, stainless steels, nickel-base alloys, aluminum alloys, and titanium alloys.

Coextrusion is defined as the simultaneous extrusion of two or more metals to form an integral product that can be carried out using conventional extrusion or drawing equipment at a temperature appropriate to the metal system being formed. This article discusses the applications, billet configurations, and metal flow modes of coextrusion. It presents the analytical studies of coextrusion: deformation energy methods, lower-bound (slab) analyses, upper-bound analyses, and finite-element analyses. These studies are used to identify the regime of material properties and process variables for which sound extrusions can be obtained. The article concludes with a discussion on the state-of-the-art of coextrusion that assists in developing process models, which accurately describe both the macroscopic and microscopic aspects of a process.