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Welcome to NDT Inspect's failure mechanism group, a place for professionals to connect and discuss the latest techniques and technologies in the study of failure mechanisms. The study of failure mechanisms is an important aspect of ensuring the safety, reliability, and performance of products, materials, and structures in various industries. It involves the analysis of how and why a component or system fails under various conditions and the identification of the underlying causes of failure.
Failure mechanisms can be complex and can involve a range of factors, including material properties, design, manufacturing processes, environmental conditions, and operating conditions. The study of failure mechanisms involves the use of various methods and techniques, including mechanical testing, metallurgical analysis, and computer modeling, to evaluate the performance and behavior of a component or system under different loads and conditions.
Our member group offers a platform for sharing knowledge and best practices on the study of failure mechanisms and its applications in various industries. Join our community of experts from around the world and be a part of the conversation on advancing the understanding of failure mechanisms and improving the performance and reliability of products, materials, and structures. Whether you are new to the study of failure mechanisms or an experienced professional, you'll find valuable resources and a welcoming community in our group.
Updates
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3 years agoAmine cracking can occur in carbon steel pipelines, which are commonly used in the oil and gas industry. The degradation of amine-based chemicals can lead to corrosion in the pipelines, causing the steel to degrade and potentially leading to leaks and other operational issues. This is why proper selection and use of amine-based chemicals, as well as regular monitoring and maintenance, is crucial in ensuring the safe and effective operation of carbon steel pipelines.
Amine cracking in HAZ on carbon steel
Amine cracking can occur in the heat-affected zone (HAZ) of carbon steel pipelines, especially in situations where the temperature exceeds the recommended limits for the particular amine-based chemical being used. The high temperatures can cause the amine-based chemical to degrade, leading to corrosion and potential cracking in the HAZ. This can compromise the integrity and safety of the pipeline, and result in operational issues.
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NDT-Inspect started the discussion Weld cracking and types of cracking in the forum Failure Mechanisms3 years agoWeld cracks can form due to a variety of factors, including:
Poor design of the welded joint: If the welded joint is not properly designed to handle the stresses it will be subjected to, it can be more prone to cracking.
Improper welding techniques: If the welding process is not performed correctly, it can result in weld cracks. This can be due to improper preheat and interpass temperatures, incorrect filler metal selection, or inadequate joint preparation.
Incompatible materials being welded together: Welding together materials with different mechanical properties or melting points can lead to weld cracking.
Presence of contaminants in the weld area: Contaminants such as oil, grease, and rust can weaken the weld and make it more prone to cracking.
Temperature changes during welding: If the temperature of the welded joint changes too quickly during welding, it can cause the metal to contract and crack.
Residual stress from previous welds or other processing: If a welded joint has been subjected to high levels of stress in the past, it can be more prone to cracking when welded again.
Hot crack: A hot crack occurs while the weld is still cooling, and is usually caused by the presence of high residual stresses or the use of incompatible materials.
Cold crack: A cold crack occurs after the weld has cooled and is usually caused by the presence of tensile stress in the welded joint.
Underbead crack: An underbead crack occurs in the weld metal below the surface of the weld, and is usually caused by the presence of hydrogen in the weld metal.
Lamellar tear: A lamellar tear is a type of weld cracking that occurs in the heat-affected zone (HAZ) of a welded joint, and is usually caused by the presence of tensile stress in the HAZ.
Root crack: A root crack occurs at the root of a welded joint and is usually caused by the presence of tensile stress or the use of incompatible materials.
Intergranular crack: An intergranular crack occurs along the grain boundaries of the weld metal and is usually caused by the presence of tensile stress or the use of incompatible materials.
There are several different types of weld cracking, including:
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NDT-Inspect started the discussion Examples of disasters that have been caused by weld cracking in the forum Failure Mechanisms3 years ago
In 1979, a weld failure caused a gas pipeline explosion in Allentown, Pennsylvania, that killed at least 22 people and injured more than 50 others.
In 1980, a crack in a weld on a tanker ship caused a spill of over 10 million gallons of oil in the Gulf of Mexico, which is considered one of the worst oil spills in history.
In 1981, a weld failure on an oil rig caused a fire that killed over 100 people and resulted in the collapse of the rig.
In 1989, a crack in a weld on a steam pipe caused a explosion in Manhattan, New York, killing three people and injuring dozens more.
In 2002, a crack in a weld on a natural gas pipeline caused a explosion in the San Francisco Bay Area that killed four people and injured over 50 others.
In 2010, a weld failure on an oil rig caused the Deepwater Horizon oil spill in the Gulf of Mexico, which is considered one of the worst environmental disasters in history.
In 2013, a crack in a weld on a natural gas pipeline caused a explosion in Illinois that killed two people and injured over a dozen others.
In 2015, a crack in a weld on a natural gas pipeline caused a explosion in California that killed one person and injured four others.
In 2016, a crack in a weld on a train track caused a derailment in Washington state that killed three people and injured dozens more.
In 2018, a crack in a weld on a pedestrian bridge in Florida caused a collapse that killed six people and injured over a dozen others.
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3 years ago
Corrosion is a major concern in offshore platforms, as it can lead to costly damage and failure of equipment. Offshore platforms are exposed to harsh and corrosive environments, including saltwater, extreme temperatures, and high humidity, which can accelerate the corrosion process.
There are several types of corrosion that can occur in offshore platforms, including:
General corrosion: This is the most common type of corrosion, and it occurs when a material is exposed to an environment that is chemically aggressive. In offshore platforms, general corrosion is often caused by the presence of water, oxygen, and other contaminants.
Stress corrosion cracking (SCC): This type of corrosion occurs when a material is subjected to both tensile stress and a corrosive environment. SCC is a common cause of failure in offshore platforms, particularly in high-stress components such as pipelines and structural steel.
Galvanic corrosion: This type of corrosion occurs when two different metals are in contact with each other in the presence of an electrolyte, such as saltwater. The more noble metal will corrode preferentially, while the less noble metal will be protected.
Erosion corrosion: This type of corrosion occurs when a flowing fluid erodes the surface of a material. Erosion corrosion is common in offshore platforms, particularly in components that are subjected to high fluid flow rates.
Preventing corrosion in offshore platforms is essential for ensuring the reliability and safety of equipment. This can be achieved through the use of corrosion-resistant materials, such as stainless steel and other alloys, and by implementing corrosion prevention and control measures, such as coatings and cathodic protection.
Effective corrosion management is also important for optimizing the efficiency and productivity of offshore operations. By understanding the types of corrosion that can occur and implementing appropriate prevention and control measures, offshore platforms can reduce downtime, extend the lifespan of equipment, and minimize the risk of costly failures.
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3 years ago
Corrosion is a major concern in the oil and gas industry, as it can lead to costly damage and failure of equipment. Understanding the different types of corrosion and how they occur is essential for preventing and mitigating their effects.
There are several types of corrosion that can occur in the oil and gas industry, including:
General corrosion: This is the most common type of corrosion, and it occurs when a material is exposed to an environment that is chemically aggressive. In the oil and gas industry, general corrosion is often caused by the presence of water, oxygen, and other contaminants.
Stress corrosion cracking (SCC): This type of corrosion occurs when a material is subjected to both tensile stress and a corrosive environment. SCC is a common cause of failure in pipelines and other high-stress components.
Galvanic corrosion: This type of corrosion occurs when two different metals are in contact with each other in the presence of an electrolyte, such as saltwater. The more noble metal will corrode preferentially, while the less noble metal will be protected.
Erosion corrosion: This type of corrosion occurs when a flowing fluid erodes the surface of a material. Erosion corrosion is common in pipelines and other components that are subjected to high fluid flow rates.
Preventing corrosion in the oil and gas industry is essential for ensuring the reliability and safety of equipment. This can be achieved through the use of corrosion-resistant materials, such as stainless steel and other alloys, and by implementing corrosion prevention and control measures, such as coatings and cathodic protection.
Effective corrosion management is also important for optimizing the efficiency and productivity of oil and gas operations. By understanding the types of corrosion that can occur and implementing appropriate prevention and control measures, companies in the oil and gas industry can reduce downtime, extend the lifespan of equipment, and minimize the risk of costly failures.
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3 years ago
Fatigue embrittlement is a type of failure mechanism that can occur in materials under certain conditions. It is a process by which materials become more brittle and susceptible to failure as a result of repeated loading or stress.
Fatigue embrittlement typically occurs in materials that are subjected to cyclic loading or stress, such as in the case of fatigue failure. In these situations, the material is repeatedly stressed and strained, which can cause microscopic cracks to form on the surface of the material. Over time, these cracks can propagate deeper into the material, eventually leading to failure.
One of the key characteristics of fatigue embrittlement is that it can occur even in materials that are not naturally brittle. For example, a metal that is normally ductile and capable of undergoing large deformations without breaking may become brittle and susceptible to failure as a result of fatigue embrittlement.
In addition to increasing the susceptibility to failure, fatigue embrittlement can also reduce the overall strength and toughness of a material. This can have significant implications in engineering applications, as it can lead to the failure of structural components and machinery.
To prevent fatigue embrittlement, materials must be carefully selected and designed to withstand the loads and stresses they will be subjected to. In addition, proper maintenance and inspection practices must be implemented to detect and address any developing cracks before they can cause failure.
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3 years ago
Step-wise cracking is a type of failure mechanism that can occur in materials under certain conditions. It is a process by which cracks form and propagate in a material in a step-by-step manner, leading to the eventual failure of the material.
Step-wise cracking can occur in a variety of materials, including metals, polymers, and ceramics. It is often seen in materials that are subjected to repeated loading or stress, such as in the case of fatigue failure. In these situations, the material is subjected to cyclic loading, which can cause cracks to form and grow over time.
The process of step-wise cracking typically begins with the formation of small cracks on the surface of the material. These cracks may be caused by a variety of factors, including mechanical stresses, thermal stresses, or a combination of both. Once these initial cracks have formed, they can begin to propagate deeper into the material, forming larger and more complex cracks.
As the cracks continue to grow, they can eventually reach a critical size where the material can no longer support the applied load. At this point, the material will fail and the cracks will propagate rapidly, leading to the complete failure of the material.
Step-wise cracking can be a significant concern in engineering applications, as it can lead to the failure of structural components and machinery. To prevent step-wise cracking, materials must be carefully selected and designed to withstand the loads and stresses they will be subjected to. In addition, proper maintenance and inspection practices must be implemented to detect and address any developing cracks before they can cause failure.
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NDT-Inspect posted an update in the group Failure Mechanisms3 years ago
Failure mechanisms, also known as failure modes, are the specific ways in which a material or component can fail or be damaged. Failure mechanisms are typically classified according to the type of failure that occurs, such as fracture, fatigue, corrosion, or wear.
Understanding failure mechanisms is important for predicting the behavior of materials and components under different loads and conditions, and for designing them to avoid failure. Different materials and components may exhibit different failure mechanisms, depending on their composition, microstructure, and the loads and conditions they are subjected to.
Failure mechanisms can be studied through various testing methods, such as destructive testing, nondestructive testing, and simulation. These methods can provide valuable information about the failure mechanisms of a material or component, and can be used to optimize its design and performance. Failure mechanisms can also be studied through failure analysis, which involves examining the causes of failure in a failed material or component. This can provide valuable insights into the underlying causes of failure and can help prevent similar failures in the future.
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NDT-Inspect posted an update in the group Failure Mechanisms3 years agoCaustic Cracking
What Does Caustic Cracking Mean?
Caustic cracking is a form of stress corrosion cracking most frequently encountered in carbon steels or iron-chromium-nickel alloys that are exposed to concentrated hydroxide solutions at temperatures of 482°F (250°C).
This phenomenon mostly occurs in boilers where caustic soda (NaOH) has been added in small amounts to boiler water to prevent scaling. However, caustics (alkalis) may become concentrated amounts in crevices around rivet heads and at hot spots. When combined with the considerable fabrication stresses around rivet holes, this can cracking of the steel boiler shells and tube plates.
Caustic cracking is also known as caustic embrittlement.
Continue reading: https://www.corrosionpedia.com/definition/238/caustic-cracking#:~:text=What%20Does%20Caustic%20Cracking%20Mean,F%20(250%C2%B0C).
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NDT-Inspect posted an update in the group Failure Mechanisms4 years agoSPEED Makes This Warship CRACK!
Interesting video regarding warship cracking and also general fatigue cracking in material
https://www.youtube.com/watch?v=7UMjcXAJCoI
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mohamed-ali-bagath joined the group Failure Mechanisms4 years ago -
NDT-Inspect posted an update in the group Failure Mechanisms4 years ago
Fracture Mechanics
/fracture-mechanics/
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5 years agoThe combination of tensile stress and a specific corrosive environment can crack stainless steels. This mode of attack is termed stress corrosion cracking (SCC). The most common environmental exposure condition responsible for SCC of stainless steels is the presence of chlorides. Although no stainless steel grade is totally immune to chloride SCC, the relative resistance of stainless steels varies substantially.
Influence of Alloy CompositionThe relative resistance to chloride SCC is dependant on the stainless steel family. The austenitic family of stainless steels is the most susceptible. The resistance of austenitic stainless steels to SCC is related to the nickel content of the steel.
The most susceptible austenitic grades have nickel contents in the range of 8 to 10 wt%. Therefore, standard grades such as 304/304L and 316/316L are very susceptible to this mode of attack. Austenitic grades with relatively high nickel and molybdenum contents such as alloy 20, 904L, and the 6% molybdenum super austenitic grades have substantially better chloride SCC resistance.
The ferritic family of stainless steels, which includes grades such as type 430 and 444 is very resistant to chloride SCC. The duplex stainless steel with their dual austenite/ferrite microstructures has a resistance that is in between that of the austenite and ferrite grades.
Corrosion TestingThe relative resistance of a stainless steel to chloride SCC is often quantified by the use of standard boiling salt solutions. The table attached summarizes the results of testing in boiling salt solutions of 26% NaCl (sodium chloride), 33% LiCl (lithium chloride), and 42% MgCl2 (magnesium chloride). The boiling LiCl and MgCl2 test solutions are very aggressive relative to practical applications and only austenitic alloys with compositions that approach those of nickel-base alloys will routinely resist cracking in these test solutions.
Crack Appearance
The typical crack morphology for chloride stress corrosion cracking consists of branched transgranular cracks. Figure 1 shows the cracking that occurred on a 6Mo super austenitic stainless steel (N08367) exposed to 0.2% chlorides at 500 °F (260 °C).
Environmental Factors
The environmental factors that increase the cracking susceptibility include higher temperatures, increased chloride content, lower pH, and higher levels of tensile stress. Temperature is an important variable. When stainless steels are fully immersed, it is rare to see chloride stress corrosion cracking at temperatures below 60 °C (150 °F).
There is a synergistic relationship between dissolved oxygen and the chloride level. If the oxygen level is reduced to the 0.01 to 0.1 ppm range, aqueous solutions containing low to moderate chloride levels are not likely to crack austenitic alloys, such as 304L and 316L. The normal solubility of O2 in water at room to moderate temperatures (e.g. up to 140°F/60°C) is 4.5 to 8 ppm at atmospheric pressure.
In actual service environments, evaporation can produce a local build-up of aggressive corrosive substances, such as chlorides and the H+ ions, resulting in conditions that are substantially more aggressive. Under severe evaporative conditions, stainless steels can crack at temperatures well below the thresholds measured under conditions where there is full immersion. Because of this, one must use caution when specifying materials for applications that involve the evaporation of chloride-bearing solutions on hot stainless steel surfaces.
The Materials Technology Institute (MTI) of the Chemical Process Industry has reviewed the literature and collected case histories to define guidelines for the chloride SCC susceptibility of types 304L and 316L stainless steel in neutral water environments.
Figure 2 shows the cracking threshold for 304L and 316L stainless steel as a function of temperature and chloride content. The level of chlorides required to produce cracking is relatively low. Failures have been reported in environments with as little as 10 ppm chlorides. This is particularly true for environments having concentrating (evaporating) mechanisms such as wet/dry interfaces or a film of solution in immediate contact with a heat-rejecting surface. In these situations, a few ppm of chlorides in the bulk solution can concentrate to hundreds of ppm in the area of evaporation.
