What are spalls, and what is the fundamental process they represent?

Spalls are fragments that break off from a larger solid body of material. The terms spalling and spallation both refer to the process of surface failure where these fragments are shed. This phenomenon can occur due to various physical and chemical mechanisms.

What are the diverse mechanisms that can lead to the formation of spalls?

Spalls can be produced by several mechanisms, including the impact of projectiles, the process of corrosion, natural weathering, cavitation, and excessive rolling pressure, such as that experienced in a ball bearing.

How are the terms spall, spalling, and spallation utilized in the field of particle physics?

In particle physics, particularly in neutron scattering instruments, the terms are used to describe neutrons generated when a target material, like uranium, is bombarded by a stream of atoms. The neutrons ejected from this target are referred to as 'spall'.

Can you describe the phenomenon of mechanical spalling and where it commonly occurs?

Mechanical spalling happens at points of high stress contact. A prime example is within a ball bearing, where the stress concentration below the surface can cause material to shear off, forming a spall. This process occurs preferentially over brinelling because the maximum shear stress is located just beneath the surface.

Explain the mechanism of plate impact spalling.

Plate impact spalling involves the interaction of compression waves within a material. When two plates collide, or when a projectile impacts a plate, compression waves are generated. These waves can reflect off free surfaces, and their interaction can create a zone of high tensile stress within the material, leading to the formation and ejection of a spall.

What is the role of spalling in anti-tank warfare, particularly with HESH shells?

In anti-tank warfare, spalling is an intended effect of certain munitions, like High-Explosive Squash Head (HESH) shells. These shells flatten against the armor and explode, creating a shock wave that travels through the armor. When this wave reflects off the inner surface as a tensile wave, it causes fragments of the armor plate, known as spall, to break off on the inside, posing a threat to the crew and equipment.

How do kinetic energy penetrators contribute to spalling in armored vehicles?

Even when a kinetic energy penetrator successfully pierces armor, it often causes significant spalling on the interior surfaces. This internal fragmentation further damages the vehicle and its occupants, contributing to the destruction or disablement of the armored fighting vehicle (AFV).

What protective measures are employed in armored vehicles to mitigate the effects of spalling?

Many armored fighting vehicles are equipped with spall liners fitted to the inside of their armor. These liners are designed to absorb the energy of spalling fragments, preventing them from reaching the crew and critical equipment.

What was the purpose of the Wz. 35 anti-tank rifle in relation to spalling?

The Wz. 35 anti-tank rifle is cited as an early example of a weapon specifically designed to induce spallation rather than relying solely on direct penetration of armor. Its design likely aimed to cause fragmentation and damage within the target vehicle through shock and spalling effects.

How does spalling occur as a form of mechanical weathering in rocks?

Spalling in mechanical weathering happens at the surface of a rock when significant shear stresses develop just beneath that surface. These stresses can be induced by various environmental factors, leading to the detachment of surface layers.

What are the primary causes of spalling related to mechanical weathering?

The main factors causing spalling in mechanical weathering include the effects of freezing and thawing cycles, the process of unloading (pressure release), differential expansion and contraction due to temperature changes, and the deposition and crystallization of salts within the rock pores.

Describe the process of spalling due to unloading.

Unloading occurs when the pressure on a rock mass is reduced, typically by the removal of overlying material (overburden). If this pressure release happens rapidly, the rock expands quickly, creating high tensile stresses at the surface that can cause spalling.

Explain how freeze-thaw cycles lead to spalling in rocks.

Freeze-thaw weathering causes spalling when moisture within rock cracks freezes. Water expands as it turns into ice, exerting significant pressure that can fracture the rock. Repeated cycles of freezing and thawing cause these surface fragments, or spalls, to break off over time.

What is exfoliation weathering, and how does it relate to spalling?

Exfoliation, also known as onion skin weathering, is a type of spalling caused by cyclic temperature changes. When a rock's surface heats up and expands more than the underlying material, it creates stress. This differential thermal expansion leads to sub-surface shear stress, causing the outer layers to peel off in thin sheets or flakes.

How can extreme heat, such as from forest fires, contribute to rock spalling?

Extreme temperature changes, like those experienced during forest fires, can cause rapid heating of rock surfaces. This rapid heating leads to significant differential thermal expansion between the surface and the interior of the rock, generating stresses that can result in spalling.

What is salt spalling, and in what types of materials does it typically occur?

Salt spalling is a weathering process affecting porous building materials like brick, natural stone, tiles, and concrete. It happens when dissolved salts are drawn into the material by water and then crystallize near the surface as the water evaporates. The expansion of these salt crystals creates stress that breaks away surface fragments, or spalls.

How does spalling manifest during the process of corrosion?

In corrosion, spalling occurs when a material, such as metal or concrete, sheds small particles of its corrosion products. Unlike passivation, where corrosion products form a protective barrier, these shed particles do not adhere well and result from significant volume changes during the corrosion reaction, leading to surface failure.

What is unique about spalling in actinide metals like depleted uranium?

Actinide metals, such as depleted uranium, exhibit significant expansion upon exposure to air, causing a fine layer of oxide to be forcibly expelled from the surface. This process can resemble the peeling of an onion. A major hazard associated with these metals is their pyrophoric nature, meaning they can spontaneously ignite due to their high surface area.

What precautions are necessary when handling actinide metals that exhibit spalling?

Due to their pyrophoric nature, toxicity, and potential radioactivity, actinide metals are often handled under an inert atmosphere, such as nitrogen or argon, within a glovebox. This controlled environment prevents spontaneous ignition and minimizes exposure risks.

What are the primary drivers for spalling in refractory concrete?

Spalling in refractory concrete is driven by two main factors: thermal strain caused by rapid heating, and internal pressures generated as water is driven out of the material. Understanding these factors is crucial for predicting how refractory structures will behave under high temperatures.

What are the potential consequences of explosive spalling in refractory concrete structures?

Explosive spalling events in refractory concrete can be dangerous, ejecting substantial fragments (1-10 kg) over considerable distances. This poses safety risks and renders the refractory structure unusable, necessitating costly repairs.

How does blast-wave overpressure cause anatomical spalling in the human body?

Blast-wave overpressure can induce spalling in the human body at the interfaces between tissues of different densities. This occurs particularly where the wave transitions from a denser medium to a less-dense one, such as the boundary between the bowel wall and gas-filled intestines, or between lung tissue and body cavities.

What are the three primary mechanisms responsible for blast injuries?

The three main mechanisms that cause blast injuries are spalling, implosion, and shearing. Spalling, as described, occurs at density interfaces, while implosion involves the collapse of structures under pressure, and shearing involves tearing forces.

What is the significance of the image showing high-speed photography of an aluminum plate impact?

The image captures the rapid disintegration of a projectile and the generation of numerous small fragments, or spalls, from an aluminum plate upon impact at high velocity (7,000 m/s). This visually demonstrates spallation occurring without the projectile necessarily penetrating the plate.

What does the image of knapped obsidian arrowheads illustrate regarding spalls?

The image shows spalls created during the process of knapping obsidian to form arrowheads and other tools. This illustrates that spalling is a fundamental technique in creating sharp edges and shaping stone artifacts, as seen with obsidian sourced from Glass Buttes, Oregon.

What does the photograph of armor plating from HMS New Zealand demonstrate about spalling?

The photograph displays a piece of armor plating gouged from HMS New Zealand's turret during the Battle of Jutland. This piece serves as a physical example of spalling caused by the impact of a German shell, highlighting the destructive effects of artillery in naval combat.

What does the image of dunite boulder desquamation represent?

The image illustrates desquamation, a form of spalling, occurring on a dunite boulder. This visual shows the characteristic peeling or flaking of surface layers, which is a common outcome of weathering processes.

What is depicted in the image of granite dome exfoliation?

The image shows a granite dome exhibiting exfoliation, a type of weathering where the outer layers of the rock gradually peel away. This process is driven by thermal expansion and contraction, leading to the formation of sheet-like spalls.

What is the relationship between spalling and the Misnay–Schardin effect?

The Misnay–Schardin effect is a phenomenon related to the fracture of materials under high-speed impact, often involving the formation of cracks and fragments. While not explicitly detailed in the text, it is listed under 'See also,' suggesting a conceptual link to the mechanisms and outcomes of spalling, particularly in projectile impacts.

How does spalling differ from friability and frangibility?

While listed under 'See also,' the text does not explicitly define the differences between spalling, friability, and frangibility. However, spalling specifically refers to the shedding of fragments from a larger solid body due to surface failure mechanisms, whereas friability generally relates to a material's tendency to crumble, and frangibility relates to its tendency to break or shatter easily.

What is the 'behind-armour debris' mentioned in the 'See also' section, and how might it relate to spalling?

Behind-armour debris refers to fragments generated inside an armored vehicle after a projectile penetrates or impacts the armor. This debris is often a direct result of spalling from the interior surface of the armor plate, making it a critical concept related to spalling in armored warfare.

Study page for spall

Dive in with Flashcard Learning!

When you are ready...
🎮 Play the Wiki2Web Clarity Challenge Game🎮

What is Spall?

Definition of Spall

Spall refers to fragments that are detached from a larger solid body of material. This phenomenon is a manifestation of surface failure, where material is shed due to various physical processes. The terms spalling and spallation describe the dynamic processes by which these fragments are produced.

Origin and Terminology

The term originates from the process of surface failure. In specific scientific contexts, such as particle physics, "spall" is used to denote particles ejected from a target material. For instance, when a target, such as uranium, is bombarded with high-energy atoms, the ejected neutrons are referred to as spall.

Underlying Principle: Stress and Fracture

At its core, spalling is a result of localized stress exceeding the material's fracture toughness. These stresses can arise from impact, thermal gradients, chemical reactions, or pressure fluctuations, leading to the formation and propagation of cracks that ultimately eject fragments from the surface.

Mechanisms of Spallation

Impact and Projectile Interaction

A primary mechanism involves the impact of a projectile. When a high-velocity object strikes a solid surface, the intense localized stress can cause material to fracture and break away. This is particularly relevant in ballistics and material science, where understanding spall generation is crucial for designing protective structures and evaluating material performance under dynamic loading.

Cavitation Phenomena

Spalling can occur due to cavitation, a process where localized low-pressure regions within a fluid cause vapor bubbles to form. The subsequent collapse of these bubbles generates intense, localized shock waves. When these shocks impinge upon adjacent solid surfaces, such as those in pumps or propellers, they can induce significant stress and cause surface material to spall.

Mechanical Stress and Deformation

Excessive mechanical stress, such as the rolling pressure experienced within a ball bearing, can lead to surface fatigue and spalling. Unlike brinelling, where deformation occurs below the surface, spalling involves the shearing off of surface layers due to shear stresses that peak just beneath the surface. Plate impact experiments provide a simplified model for studying this phenomenon, where compression waves reflect off free surfaces to create tensile stresses that induce spall.

Corrosion and Chemical Degradation

Corrosion processes can also lead to spalling. In metals and concrete, the formation of corrosion products often involves volume changes that build up internal stresses. If these stresses exceed the material's strength, fragments of the corroded layer or the underlying material can be shed. This is particularly notable with certain reactive metals like actinides, where oxidation leads to significant expansion and detachment of oxide layers.

Weathering Processes

In geological contexts, spalling is a significant form of mechanical weathering. It occurs when stresses within rock surfaces, induced by factors like freeze-thaw cycles, unloading of overburden, thermal expansion, or salt crystallization, exceed the rock's tensile strength, causing surface layers to flake off.

Detailed Look: Mechanical Spalling

Bearing Surfaces and Fatigue

In mechanical components like ball bearings, the repeated application of high contact stresses can lead to subsurface shear failures. The maximum shear stress typically occurs at a depth slightly below the surface. When this stress surpasses the material's fatigue limit, it initiates micro-cracks that coalesce, eventually leading to the ejection of small, cup-shaped fragments known as spalls. This process is a common failure mode in rolling-element bearings.

Plate Impact Dynamics

A fundamental experimental setup for studying spalling involves plate impact. In this scenario, one plate strikes another at high velocity. The impact generates a shock wave that propagates through the target plate. Upon reaching the rear free surface, this compression wave reflects as a tensile wave. If the magnitude of this tensile stress is sufficient, it can exceed the material's dynamic tensile strength, causing a fracture layer parallel to the surface and ejecting a fragment—the spall.

Cavitation Erosion

Cavitation-induced spalling is a destructive process observed in fluid machinery. When fluid pressure drops below its vapor pressure, bubbles form. As these bubbles move into regions of higher pressure, they collapse violently, generating micro-jets and shock waves. Repeated impingement of these pressure waves on solid surfaces, such as pump impellers or propeller blades, can lead to material fatigue and the progressive removal of surface material through spalling.

Spalling in Anti-Tank Warfare

High-Explosive Squash Head (HESH)

The High-Explosive Squash Head (HESH) projectile is specifically designed to induce spalling. Upon impact with armor plating, the plastic explosive warhead deforms and detonates, creating a powerful shock wave. This wave propagates through the armor as a compression wave and reflects off the inner surface as a tensile wave. If the tensile stress exceeds the armor material's strength, it causes fragments (spall) to break away from the interior surface, posing a significant threat to the vehicle's crew and internal components.

Kinetic Energy Penetrators

While kinetic energy penetrators (KEPs) primarily function by piercing armor through sheer force, they also induce significant spalling within the target. The immense localized stress and deformation caused by a KEP's impact can fracture the armor from the inside, contributing to the overall damage and disablement of the armored vehicle, even if complete penetration is not achieved.

Protective Measures: Spall Liners

To mitigate the effects of spalling, many modern armored fighting vehicles (AFVs) are equipped with internal spall liners. These layers, often made of materials like Kevlar or specialized composites, are designed to absorb the energy of incoming fragments and prevent them from reaching the crew compartment. This passive protection system is critical for enhancing crew survivability against threats that rely on spallation.

Historical Context: WZ. 35 Rifle

An early example of a weapon designed to exploit spalling was the Polish wz. 35 anti-tank rifle. While not a penetrator, its specialized ammunition was intended to cause significant spalling upon impact with enemy tank armor, thereby disabling the vehicle.

Spalling in Geological Weathering

Freeze-Thaw Cycles

Freeze-thaw weathering is a potent mechanical process. When water infiltrates cracks or pores in rock or masonry, it expands upon freezing. This expansion generates significant hydrostatic pressure, exerting tensile stress on the surrounding material. Repeated cycles of freezing and thawing can progressively widen these cracks and cause surface layers or fragments (spalls) to detach.

Unloading and Expansion

Geological unloading occurs when overlying rock masses are removed through erosion. This reduction in confining pressure allows the underlying rock to expand. If this expansion is rapid, it can induce significant tensile stresses near the surface, leading to the formation of sheet-like spalls, a process often referred to as exfoliation.

Thermal Expansion and Exfoliation

Differential thermal expansion and contraction due to daily or seasonal temperature fluctuations can cause stress within rocks. When surface layers heat up or cool down much faster than the interior, internal stresses build. In processes like exfoliation (or onion-skin weathering), these stresses lead to the gradual shedding of thin, curved layers of rock, resembling the layers of an onion.

Salt Crystallization

Salt spalling is a destructive weathering mechanism common in porous building materials exposed to saline environments. Dissolved salts are drawn into the material via capillary action. As moisture evaporates from the surface, the salts crystallize within the pores. The growth of these salt crystals exerts pressure, leading to internal stresses that can fracture the material and cause surface spalling.

Spalling Driven by Corrosion

Metallic Corrosion Products

In metals, corrosion often produces oxides or other compounds that occupy a larger volume than the original metal. This volume expansion generates internal stresses at the metal-corrosion product interface. Unlike passivation, where a stable, adherent protective layer forms, this expansive corrosion product layer can build up stress until it detaches, shedding fragments (spall) and exposing fresh metal to further corrosion.

Actinide Metals and Pyrophoricity

Actinide metals, such as depleted uranium, exhibit extreme reactivity with air. Oxidation leads to significant volume expansion, forcibly expelling oxide layers as spall. This process increases the surface area-to-volume ratio, enhancing the material's pyrophoric nature—its tendency to spontaneously ignite in air. Handling these materials requires specialized inert atmospheres to prevent hazardous reactions.

Concrete Degradation

Corrosion processes within concrete structures, such as the rusting of reinforcing steel, can also lead to spalling. The expansion of rust exerts pressure on the surrounding concrete, causing it to crack and eventually break away from the surface. This degradation compromises the structural integrity and durability of concrete elements.

Spalling in Refractory Concrete

Thermal Strain Effects

Refractory concrete, designed for high-temperature applications, is susceptible to spalling, particularly during rapid heating events. The rapid temperature increase induces significant thermal gradients within the material. This differential expansion creates substantial internal stresses. If these thermal stresses exceed the concrete's tensile strength, explosive spalling can occur, ejecting large fragments.

Internal Pressures from Water Removal

The removal of physically or chemically bound water during the heating of refractory concrete can generate significant internal pressures. As water turns to steam within the material's pores, it expands rapidly. This pressure can drive crack propagation and contribute to explosive spalling, especially if the heating rate is high and the material cannot adequately vent the generated steam.

Industrial Implications

Explosive spalling events in industrial settings, such as furnaces or kilns lined with refractory concrete, pose serious safety risks. Ejected fragments can travel considerable distances, causing injury or damage. Furthermore, spalling renders the refractory structure ineffective, necessitating costly repairs and downtime. Predicting and mitigating these events is therefore critical for operational safety and efficiency.

Anatomical Spalling in Blast Injuries

Blast Wave Mechanics

Explosive blast waves create rapid, extreme pressure changes. When these waves encounter interfaces between tissues of significantly different densities within the human body, they can induce a phenomenon analogous to material spalling. This occurs where the wave transitions from a denser medium to a less dense one, such as from solid tissue to air-filled cavities.

Lung and Bowel Injuries

This anatomical spalling is particularly relevant in understanding blast injuries to organs like the lungs and bowels. The interface between the lung tissue and the air in the alveoli, or between the bowel wall and gas within the lumen, can experience shear forces and tensile stresses generated by the blast wave. This can lead to tissue fragmentation or tearing, contributing to the severity of the injury.

Injury Mechanisms

Spallation is one of the primary mechanisms contributing to blast injury, alongside direct pressure effects (compression and implosion) and shearing forces. Understanding these distinct mechanisms is vital for medical professionals diagnosing and treating individuals exposed to explosions, enabling more targeted interventions.

Teacher's Corner

Edit and Print this course in the Wiki2Web Teacher Studio

Edit and Print Materials from this study in the wiki2web studio

Click here to open the "Spall" Wiki2Web Studio curriculum kit

Use the free Wiki2web Studio to generate printable flashcards, worksheets, exams, and export your materials as a web page or an interactive game.

True or False?

Test Your Knowledge!

Gamer's Corner

Are you ready for the Wiki2Web Clarity Challenge?

Learn about spall while playing the wiki2web Clarity Challenge game.

Unlock the mystery image and prove your knowledge by earning trophies. This simple game is addictively fun and is a great way to learn!

Play now

Explore More Topics

Discover other topics to study!

the entertainment capital of the world

buffalo soapstone alaska

electroweak interaction

ge healthcare

laupheim

tenet film

References

The Accelerated Drying of Refractory Concrete â Parts I and II, Volume 6, Issues 2 and 4 /The Refractory Worldforum

A full list of references for this article are available at the Spall Wikipedia page

Feedback & Support

To report an issue with this page, or to find out ways to support the mission, please click here.

Disclaimer

Important Notice

This page was generated by an Artificial Intelligence and is intended for informational and educational purposes only. The content is based on a snapshot of publicly available data from Wikipedia and may not be entirely accurate, complete, or up-to-date. The information provided herein is synthesized for clarity and educational value, aiming to present complex topics in an accessible manner for advanced learners.

This is not professional advice. The information provided on this website is not a substitute for expert consultation in material science, engineering, geology, physics, or military applications. Always consult with qualified professionals for specific applications or concerns related to spalling phenomena.

The creators of this page are not responsible for any errors or omissions, or for any actions taken based on the information provided herein.

Spall: Fragments of Force

💡 Dive in with Flashcard Learning! 💡

What is Spall? ℹ️

🧱 Definition of Spall

🔬 Origin and Terminology

⚡ Underlying Principle: Stress and Fracture

Mechanisms of Spallation ⚙️

💥 Impact and Projectile Interaction

🌊 Cavitation Phenomena

⚙️ Mechanical Stress and Deformation

🧪 Corrosion and Chemical Degradation

⛰️ Weathering Processes

Detailed Look: Mechanical Spalling ⚡

⚙️ Bearing Surfaces and Fatigue

💥 Plate Impact Dynamics

💧 Cavitation Erosion

Spalling in Anti-Tank Warfare 🛡️

💣 High-Explosive Squash Head (HESH)

🎯 Kinetic Energy Penetrators

🛡️ Protective Measures: Spall Liners

📜 Historical Context: WZ. 35 Rifle

Spalling in Geological Weathering ⛰️

🧊 Freeze-Thaw Cycles

⬇️ Unloading and Expansion

☀️ Thermal Expansion and Exfoliation

🧂 Salt Crystallization

Spalling Driven by Corrosion 🧪

🔩 Metallic Corrosion Products

☢️ Actinide Metals and Pyrophoricity

🏗️ Concrete Degradation

Spalling in Refractory Concrete 🔥

🌡️ Thermal Strain Effects

💧 Internal Pressures from Water Removal

⚠️ Industrial Implications

Anatomical Spalling in Blast Injuries 🤕

💥 Blast Wave Mechanics

🫁 Lung and Bowel Injuries

🔬 Injury Mechanisms

Teacher's Corner 🧑‍🏫

Edit and Print this course in the Wiki2Web Teacher Studio

True or False? 🤔

❓ Test Your Knowledge! ❓

Gamer's Corner 🎮

Are you ready for the Wiki2Web Clarity Challenge?

Explore More Topics

📜 Discover other topics to study!

References

📜 References

Feedback & Support 👍

To report an issue with this page, or to find out ways to support the mission, please click here.

Disclaimer ⚠️

📜 Important Notice

Dive in with Flashcard Learning!

What is Spall?

Definition of Spall

Origin and Terminology

Underlying Principle: Stress and Fracture

Mechanisms of Spallation

Impact and Projectile Interaction

Cavitation Phenomena

Mechanical Stress and Deformation

Corrosion and Chemical Degradation

Weathering Processes

Detailed Look: Mechanical Spalling

Bearing Surfaces and Fatigue

Plate Impact Dynamics

Cavitation Erosion

Spalling in Anti-Tank Warfare

High-Explosive Squash Head (HESH)

Kinetic Energy Penetrators

Protective Measures: Spall Liners

Historical Context: WZ. 35 Rifle

Spalling in Geological Weathering

Freeze-Thaw Cycles

Unloading and Expansion

Thermal Expansion and Exfoliation

Salt Crystallization

Spalling Driven by Corrosion

Metallic Corrosion Products

Actinide Metals and Pyrophoricity

Concrete Degradation

Spalling in Refractory Concrete

Thermal Strain Effects

Internal Pressures from Water Removal

Industrial Implications

Anatomical Spalling in Blast Injuries

Blast Wave Mechanics

Lung and Bowel Injuries

Injury Mechanisms

Teacher's Corner

True or False?

Test Your Knowledge!

Gamer's Corner

Discover other topics to study!

References

Feedback & Support

Disclaimer

Important Notice