Search Results for flow-localization-controlled failure

This article discusses the equipment design, procedures, experimental considerations, and interpretation of the torsion tests used to establish workability. It describes the application of torsion testing to obtain flow-stress data and to gage fracture-controlled workability and flow-localization-controlled failure. The article discusses the torsion test used to establish the processing parameters that are required to produce the desired microstructures.

Workability in forging depends on a variety of material, process-variable, and die-design features. A number of test techniques have been developed for gaging forgeability depending on alloy type, microstructure, die geometry, and process variables. This article summarizes some common workability tests and illustrates their application in practical forging situations. Workability tests for open-die forging of cast structures, hot and cold open-die forging of recrystallized structures, fracture-controlled defect formation, establishing effects of process variables and secondary tensile stresses on forgeability, and flow-localization-controlled failure are some common tests. The workability test used for closed-die forging is also summarized.

This article focuses on the modeling and simulation of cavitation phenomena. It summarizes the experimental observations of cavitation and reviews the modeling of cavity nucleation and growth. The article discusses the modeling of the cavity growth based on mesoscale and microscale under uniaxial versus multiaxial tensile-stress conditions. Mesoscale models incorporate the influence of local microstructure and texture on cavitation. The article outlines the descriptions of cavity coalescence and shrinkage. It also describes the simulation of the tension test to predict tensile ductility and to construct failure-mechanism maps.

This article discusses two types of hot-tension tests, namely, the Gleeble test and conventional isothermal hot-tension test, as well as their equipment. It summarizes the data for hot ductility, strength, and hot-tension for commercial alloys. The article presents isothermal hot-tension test data, which helps to gain information on a number of material parameters and material coefficients. It details the effect of test conditions on flow behavior. The article briefly describes the detailed interpretation of data from the isothermal hot-tension test using numerical model. It also explains the cavitation mechanism and failure modes that occur during hot-tension testing.

This article briefly describes water and steam chemistry, which influence the effect of corrosion in boilers. The appropriate control measures to prevent corrosion in boilers are also presented. The article provides a discussion on the common causes of fluid-side corrosion such as flow-accelerated corrosion, oxygen pitting, chelant corrosion, caustic corrosion, acid corrosion, organic corrosion, phosphate corrosion, hydrogen damage, and corrosion-assisted cracking.

Unexpected and frequently costly failures occur due to the lack of sound and reliable engineering design. Therefore, designing against corrosion is essential for reducing such failures. This article provides a discussion on design considerations and general corrosion awareness. It details the functional requirements, such as design and materials selection, which assist in controlling corrosion in different environments. The article also illustrates the design factors that accelerate corrosion.

This article reviews the common methods of shear and multiaxial testing for the evaluation of engineering components such as fasteners and mill products. It discusses shear test methods, including through-thickness tests, in-plane shear tests, and double-notched shear test. The article provides information on torsional (rotational shear) tests as well as the basic equipment and setup of torsion testing. Motors, twist and torque transducers, torque sensors, and heating systems as well as the specimen preparation procedure are also discussed.

The principal task of a failure analyst during a physical-cause investigation is to identify the sequence of events involved in the failure. Technical skills and tools are required for such identification, but the analyst also needs a mental organizational framework that helps evaluate the significance of observations. This article discusses the processes involved in the characterization and identification of damage and damage mechanisms. It describes the relationships between damage causes, mechanisms, and modes with examples. In addition, some of the more prevalent and encompassing characterization approaches and categorization methods of damage mechanism are also covered.

This article describes the general root causes of failure associated with wrought metals and metalworking. This includes a brief review of the discontinuities or imperfections that may be the common sources of failure-inducing defects in bulk working of wrought products. The article discusses the types of imperfections that can be traced to the original ingot product. These include chemical segregation; ingot pipe, porosity, and centerline shrinkage; high hydrogen content; nonmetallic inclusions; unmelted electrodes and shelf; and cracks, laminations, seams, pits, blisters, and scabs. The article provides a discussion on the imperfections found in steel forgings. The problems encountered in sheet metal forming are also discussed. The article concludes with information on the causes of failure in cold formed parts.

This article describes the two critical goals in a failure investigation: damage mechanisms and damage modes. It explains the determination of primary and secondary damage mechanisms and discusses the methodology used to classify the damage mechanisms.

The steam turbine is the simplest and most efficient engine for converting large amounts of heat energy into mechanical work. This article discusses the primary corrosion mechanisms such as corrosion fatigue, stress-corrosion cracking (SCC), pitting, corrosion, and erosion-corrosion, in steam turbines. It illustrates the various causes of the corrosiveness of the steam turbine environments through a Mollier diagram. The article describes the four parts of design disciplines that affect turbine corrosion, namely, mechanical design, heat transfer, flow and thermodynamics, and physical shape. It lists the ways to control the steam and surface chemistry, and design and material improvements to minimize turbine corrosion.

This article discusses the particular corrosion problems encountered and the corrosion control methods used in petroleum production (i.e., upstream) and the storage and transportation of oil and gas (i.e., midstream) up to the refinery (i.e., downstream). These control methods include proper material selection, protective coatings, cathodic protection systems, use of inhibitors, use of nonmetallic materials, and control of the environment. The article reviews the aspects of corrosion that tend to be unique to corrosion as encountered in applications involving oil and gas exploration and production. It discusses corrosion problems that are specific to the various types of environments or equipment used in secondary recovery, including producing wells, producing flow lines, and injection wells. Corrosion mitigation methods and guidelines are also discussed for each type of environment.

This article explains the main types and characteristic causes of failures in boilers and other equipment in stationary and marine power plants that use steam as the working fluid with examples. It focuses on the distinctive features of each type that enable the failure analyst to determine the cause and suggest corrective action. The causes of failures include tube rupture, corrosion or scaling, fatigue, erosion, and stress-corrosion cracking. The article also describes the procedures for conducting a failure analysis.

This article reviews the dynamic factors, experimental methods and setup, and result analysis of different types of high strain rate shear tests. These include high strain rate torsion testing, double-notch shear testing and punch loading, drop-weight compression shear testing, thick-walled cylinder testing, and pressure-shear plate impact testing.

Failures in boilers and other equipment taking place in power plants that use steam as the working fluid are discussed in this article. The discussion is mainly concerned with failures in Rankine cycle systems that use fossil fuels as the primary heat source. The general procedure and techniques followed in failure investigation of boilers and related equipment are discussed. The article is framed with an objective to provide systematic information on various damage mechanisms leading to the failure of boiler tubes, headers, and drums, supplemented by representative case studies for a greater understanding of the respective damage mechanism.

This article discusses the bulk formability or workability of steels. It describes their formability characteristics and presents procedures for various formability tests used for carbon and alloy steels. Tests for bulk formability can be divided into two main categories: primary tests and specialized tests. The article compares the processing of microalloyed plate and bar products. The article focuses on the use of torsion testing to evaluate the forgeability of carbon and alloy steels and presents information on measuring flow stress. The article discusses the metallurgy and thermomechanical processing of high-strength low-alloy (microalloyed) steels and the various parts of the rolling operation. The article summarizes some of the common tests for determining formability in open-die and closed-die forgings.

This article describes the methodology for performing a failure modes and effects analysis (FMEA). It explains the methodology with the help of a hot water heater and provides a discussion on the role of FMEA in the design process. The article presents the analysis procedures and shows how proper planning, along with functional, interface, and detailed fault analyses, makes FMEA a process that facilitates the design throughout the product development cycle. It also discusses the use of fault equivalence to reduce the amount of labor required by the analysis. The article shows how fault trees are used to unify the analysis of failure modes caused by design errors, manufacturing and maintenance processes, materials, and so on, and to assess the probability of failure mode occurrence. It concludes with information on some of the approaches to automating the FMEA.

This article is a pictorial guide to forms of corrosion that draws attention to common pitfalls or situations that have caused premature corrosion, sometimes with expensive consequences. The examples used are not exhaustive; they highlight the necessity to fully examine materials, conditions, and specific circumstances that together can reduce the anticipated service life of a component or plant. The color images in this article are categorized according to the type of corrosion following the general order that is adopted in Volume 13A of ASM Handbook. The first table of the article provides a categorization of the forms of corrosion. It also provides a reference to articles or sections of articles in Volume 13A that detail the particular corrosion form or mechanism. The second table is a guide listing the figures in this article by material and by the corrosion form or mechanism illustrated.

This article addresses the major heat-transfer components of the water-steam loop of a power plant. It describes the various types of condensers, including water-cooled condensers and air-cooled condensers. The article explains the corrosion mechanisms encountered in the condensers, including erosion-corrosion, galvanic corrosion, and pitting corrosion. It discusses the types of deaerators and deals with their corrosion problems. The article provides a discussion on two types of feedwater heaters: channel feedwater heaters and header feedwater heaters. It summarizes the corrosion problems associated with common feedwater heater tube materials.

This article provides information on thermal spray coating features, which combine to determine the properties of a coating. These include the lamellar or layered splat structure, entrapped unmelted or resolidified particles, pores, oxide inclusions, grains, phases, cracks, and bond interfaces. The article describes the sources of porosity and the factors that control the final coating porosity levels. The article also lists the materials most suitable for thermal spraying processes.