Matscie #4 $ 5 & 6 & 7

• Tough or ductile fracture - failure is preceded by excessive plastic deformation often detectable.
• Brittle or non-ductile fracture - involves little or no plastic deformation – often Catastrophic.
• Fracture - toughness describes the ability of a material containing a crack to resist fracture.
• Impact Testing - is used to observe the mechanics that a material will exhibit when it experiences a shock loading that causes the specimen to immediately deform, fracture or rupture completely
• Charpy Impact Test - also known as the Charpy V-notch test, is a high strain-rate test that involves striking a standard notched specimen with a controlled weight pendulum swung from a set height.
• Izod Impact Test - is a method of determining the impact resistance of materials.
• Tensile Impact Test - measures the amount of force needed to break a specimen under a highspeed tensile load introduced through a swinging pendulum.
• Fatigue Testing - helps determine a material’s ability to withstand cyclic fatigue loading conditions
• Uniform Corrosion - is considered an even attack across the surface of a material and is the most common type of corrosion.
• Pitting Corrosion - is one of the most destructive types of corrosion, as it can be hard to predict, detect and characterize
• Crevice Corrosion - is also a localized form of corrosion and usually results from a stagnant microenvironment in which there is a difference in the concentration of ions between two areas of a metal
• Intergranular Corrosion - An examination of the microstructure of a metal reveals the grains that form during solidification of the alloy, aswell as the grain boundaries between them.
• Stress Corrosion Cracking (SCC) - is a result of the combination of tensile stress and a corrosive environment, often at elevated temperatures.
• Stress corrosion - may result from external stress such as actual tensile loads on the metal or expansion/contraction due to rapid temperature changes.
• Galvanic corrosion - is the degradation of one metal near a joint or juncture that occurs when two electrochemically dissimilar metals are in electrical contact in an electrolytic environment; for example, when copper is in contact with steel in a saltwater environment.
• Temperature - As a general rule, increasing temperature increases corrosion rates.
• pH corrosion - rates almost always increase with decreasing pH (increasing acidity)
• Oxygen Concentration - in corrosion is as an aggressive gas or oxidizing agent.
• Fluid Velocity - The dependence of corrosion rate on fluid velocity is complex
• Suspended Solids - An increase in suspended solids levels will accelerate corrosion rates
• Metal Type - One simple way to prevent corrosion is to use a corrosion resistant metal such as aluminum or stainless steel.
• Anode - The electrode where galvanic reaction(s) generate electrons - negative ions are discharged and positive ions are formed.
• Cathode - The electrode that receives electrons - positive ions are discharged, negative ions are formed. The cathode is protected from corrosion.
• Electrolyte - The conductor through which current is carried. Electrolytes include aqueous solutions or other liquids.
• Return Current Path - The metallic pathway connecting the anode to the cathode. It is often the underlying metal substrate.
• Protective Coatings - The application of a paint coating is a cost-effective way of preventing corrosion.
• Environmental Measures - Corrosion is caused by a chemical reaction between the metal and gases in the surrounding environment.
• Sacrificial Coatings - involves coating the metal with an additional metal type that is more likely to oxidize; hence
• Cathodic Protection - The most common example of cathodic protection is the coating of iron alloy steel with zinc, a process known as galvanizing
• Anodic protection- involves coating the iron alloy steel with a less active metal, such as tin.
• Corrosion Inhibitors - are chemicals that react with the surface of the metal or the surrounding gases to suppress the electrochemical reactions leading to corrosion
• Design Modification - can help reduce corrosion and improve the durability of any existing protective anti corrosive coatings.
• Ultrasonic testing (UT)- is a non-destructive test method that utilizes sound waves to detect cracks and defects in parts and materials.
• Contact Ultrasonic testing - is often used in situations where radiographic inspection is not possible because it requires access to only one side of the test specimen.
• Immersion ultrasonic testing - is a laboratory-based inspection, useful for the detection of smaller defects, from cracking to porosity.
• Radiographic Testing (RT) is a non-destructive testing (NDT) technique that involves the use of either x-rays or gamma rays to view the internal structure of a component.
• Conventional radiography - uses a sensitive film which reacts to the emitted radiation to capture an image of the part being tested.
• Digital Radiography - Unlike conventional radiography, digital radiography doesn’t require film.
• computed Radiography - uses a phosphor imaging plate that replaces film in conventional radiography techniques.
• Direct Radiography (DR) - is also a form of digital radiography and very similar to computed radiography.