Search Results for stress corrosion cracks

This article presents the results of a study in which stress corrosion crack growth was examined in situ in aluminum alloy samples. Precracked test specimens were mounted in a customized load frame and a scanning vibrating probe was used to map potential gradients induced by electrochemical coupling current around the crack tip, mouth, and surrounding surfaces. The authors describe the test setup and present and analyze their findings.

Stress corrosion cracking is an insidious form of damage that can occur when a susceptible metal is subjected to a tensile stress in a specific environment. To relieve tensile stresses at welded joints, postweld heat treatment can be helpful in reducing the susceptibility of carbon steel fabrications to SCC. When planning to use stainless steels in chloride-containing environments, it is advisable to select alloys that have been specifically developed to resist stress chloride cracking such as ferritic-austenitic (duplex) alloys, low-carbon ferritic alloys, and 6% Mo austenitic alloys or to select high-nickel alloys.

Although stress corrosion cracking (SCC) accounts for just a fraction of all engineering failures, its prevention is a major problem, particularly in the aerospace industry. Recent archaeometallurgical studies show that stress corrosion cracking occurred in ancient metallic artifacts. This article describes investigations that revealed definite evidence for SCC in ancient silver and bronze alloys and a probable case of SCC in low-carat (13K) gold. Diagnostic methods included visual inspection, metallography, and fractography.

A look at how bifilms are created during casting may offer clues to eliminating cracks, tensile fracture, fatigue failure, pitting, and stress corrosion cracking failures.

Researchers at Pacific Northwest National Laboratory (PNNL) use a combination of scanning and transmission electron microscopy, atom probe tomography, and focused ion beam milling to analyze corrosion and crack structures in light-water reactor components with near-atomic spatial resolution.

This article provides an overview of cracking and fracture mechanisms in heritage gold, silver, low-tin bronze, and wrought iron alloys. Understanding these mechanisms can be important for restorers, and possibly for conservators and curators as well. Metallography is widely used (when sampling is permitted) for studying archaeometallurgical artifacts in detail. However, fracture surface examinations and analysis (i.e., fractography) can often provide even greater insight. Case studies demonstrate the benefits of employing fractographic analysis to study cracking and fracture mechanisms in heritage alloys.

Cold spraying is a potentially attractive method for producing accident tolerant fuel cladding, near-net shape nuclear reactor components, and nuclear fuel storage canisters.

A pin used to hold the side plates together in a conveyor chain system fractured and failed, prompting a metallurgical failure analysis. This case study reviews the analytical steps and conclusions from the study of the failed pin.

Case studies from a range of industries illustrate how advanced additive manufacturing capabilities optimize both material performance and value. The materials discussed are Inconel 718, Ti-6Al-4V, aluminum F357, and Hastelloy X.

As copper’s antimicrobial benefits spur new applications, the metal’s other properties are also worth reviewing. Along with strength, fatigue resistance, and ability to take a good finish, the primary selection criteria for copper and its alloys are electrical conductivity, thermal conductivity, corrosion resistance, color, ease of fabrication, and antimicrobial benefits.

Nondestructive evaluation comprises a large family of specific test disciplines including visual inspection, dimensional metrology, ultrasound, radiography, penetrant tests, magnetic particle tests, leak tests, eddy current tests, potential drop tests, flash and vibrothermography, shearography, acoustic emissions, and many other methods. This article offers an overview of NDE science and discusses some key considerations for choosing specific techniques.

The National Research Council of Canada has teamed up with industrial partners to investigate the challenges of aluminum lightweighting. Project coverage areas include manufacturing of advanced aluminum components, assembly of aluminum and multi-material components, and durability and performance evaluation and solutions.

The production and processing of advanced materials, namely metals and alloys, began in the Old World about 8000 years ago and developed over many millennia, providing a lasting legacy for modern civilizations. This article gives a brief overview of the production and processing of ancient bronzes and silver in the Old World, and also mentions post-processing problems including corrosion and embrittlement, owing to long-term burial before archaeological recovery.

This article summarizes the more common analytical techniques for studying ancient metal artifacts, illustrated by case histories. There are two main classifications: noninvasive and invasive techniques. This distinction is of prime importance because some heritage objects may be too rare or valuable for invasive sampling, or there may be ethical objections to certain types of examination. Noninvasive examination of ancient metal artifacts is important, yet it cannot provide the detailed information obtainable from invasive techniques. This is especially true when artifacts contain “hidden” damage and there is also a need for accurate quantitative analyses.

Fasteners play a critical role in engineered structures as a method of nonpermanent joining for the aerospace, infrastructure, civil, automotive, energy generation/distribution, and many other industries. Fastener failures can lead to disastrous consequences and substantial financial losses. One of the most common fastener failure modes is fatigue crack initiation and growth. Inadequate design considerations, material problems, insufficient preload, loosening, and excessive loads can all contribute to fastener fatigue. A case study of steel screw failures highlights some of the critical manufacturing and design factors that affect fastener fatigue.

Alcoa’s aluminum monopoly continued throughout the 1920s and 1930s—a serious problem when World War II demands far exceeded production capacity. This articles reviews advances in aluminum technology during the war and the postwar period.

Beyond weight savings, aluminum products offer corrosion resistance, weldability, and ease of maintenance for a wide range of marine vessels. Aluminum was recognized as a promising material for marine construction from the early days of the industry. The development of 5xxx alloys and large production capacity made aluminum use more technically and economically possible beginning in the 1950s. The variety of aluminum vessels ranges from small fishing boats and fast ferry catamarans to cruise ships and military vessels. All benefit from aluminum's relatively light weight, low maintenance costs, and easy repairability. Other benefits of using aluminum in marine applications include formability, corrosion resistance, and availability in various product forms.

The corrosion of structural materials and control of coolant chemistry are key factors that impact the lifetime of nuclear reactors and the development of future reactors. This article reviews corrosion issues in four reactor concepts that use vastly different coolant types: light water reactors, lead fast reactors, high temperature gas-cooled reactors, and fluoride salt-cooled high temperature reactors.

The unique metallurgy and microstructure of Cu-Ni-Sn spinodal alloys provide a combination of strength, toughness, hardness, and corrosion resistance, suiting them for applications ranging from bearings, bushings, and friction surfaces in all sorts of machinery to electrical connectors and EMI shielding gaskets.

Corrosion is commonly defined as the deterioration of a material or its properties because of a reaction with its environment. It is a natural process due to a high energy state induced in metals and alloys during refining, processing, and manufacturing. Modern methods for preventing and controlling corrosion can reduce or eliminate its impact on public safety, the economy, and the environment. New technologies push materials to withstand increasingly demanding conditions as a result of higher temperatures and pressures, and environments with greater corrosivity. Therefore, the risks of new types of corrosion failures need to be considered along with methods to avoid them, as described in this article.