Materials Science PDF

Review 1. NON-METALLIC MATERIALS Containing no metal. 2. FERROUS MATERIALS Iron, or any alloy containing iron. 3. the force per unit of area, usually expressed in pounds per square inch, is called the unit stress or simply the stress., 4. If the stress is the result of forces...

Review 1. NON-METALLIC MATERIALS Containing no metal. 2. FERROUS MATERIALS Iron, or any alloy containing iron. 3. the force per unit of area, usually expressed in pounds per square inch, is called the unit stress or simply the stress., 4. If the stress is the result of forces tending to stretch or lengthen the material it is called a tensile stress. 5. S If it compresses or shortens the material a compressive stress. 6. S if it shears the material, a shearing stress. 7. S If it twists the material, a torsion stress 8. ELASTICITY A body is said to be perfectly elastic if, after it has been deformed by external forces, it returns completely to its original shape when the forces are removed. 9. YIELD STRENGTH The maximum stress that can be applied to a material without permanent deformation of the material. 10. ULTIMATE STRENGTH The stress at which a material in tension, compression or shear will fracture. 11. PLASTICITY The property of a metal which allows it to be reshaped. 12. CONDUCTIVITY The characteristic of a material which makes it possible for it to transmit heat or electrical conduction. 13. DURABILITY The property of metal that enables it to withstand force over a period of time. 14. The three most important lightweight metals in aircraft structure are: 15. Aluminium and Aluminium alloys (density 2,7 Kg/dm3) 16. Titanium and Titanium alloys (density 4,5 Kg/dm3) 17. Magnesium and Magnesium alloys 18. The base material iron is the chemical element Fe which, in its pure form, is a very soft, malleable and ductile metal which is easy to form and shape. 19. The resistance of steel against corrosion can be increased by the addition of large quantities of certain alloying elements, 20. Carbon (not considered as an alloying element) Increases strength and hardness. Reduces toughness, formability and weldability. 21. Silicon acts as a hardener. 22. Chromium increases the strength, wear and corrosion resistance. 23. Selection of high-strength alloy steel is based upon high tensile-to-yield ratios 24. Toughness of a material is the ability displayed to absorb energy by deformation 25. Steels are only hardenable due to the existence of a certain carbon content. 26. The quenching is done using water, oil or a different medium. 27. Sheets made of alloys are clad with a thin layer of pure aluminium on both sides as a means of corrosion protection. 28. Cladding means to permanently weld metal layers onto a basis material, 29. The main purpose of hardening is to increase the strength of hardenable aluminium material, by a precisely specified heat treatment procedure. 30. STEPS OF HARDENING 1-Solution Annealing The material is heated to a specified temperature and held there for a specified time. 2-Natural Aging and Artificial Aging Hardening of the material at room temperature (natural aging) or elevated temperature in a furnace (artificial aging). 31. the quenching is carried out in a water bath at temperatures of 20_to 38_C, 32. Generally, the quenching has to be carried out within 5 to 15 seconds, depending on the material tickness. 33. Hardness testing is a method of determining the results of heat treatment as well as the state of a metal prior to heat treatment 34. The Brinell hardness tester uses a hardened spherical ball, which is forced into the surface of the metal. 35. The Rockwell hardness tester measures the resistance to penetration as does the Brinell tester 36. In civil commercial aircraft, the main reason for structure fatigue is the number of flights, which every single aircraft is carrying out. 37. Composite materials are used mainly to reduce weight 38. Fibreglass is made from small strands of molten silica glass and than spun together and woven into cloth 39. Core material is the central member of the assembly. 40. Adhesive is a substance used to bond two or more surfaces together. 41. Adhesive bonds distribute the stress at the bonding point, are moisture- and corrosion-resistant and eliminate the need for rivets and bolts. 42. Phenolic resins are used for cabin furnishing due to their fire resistance and low toxicity. (Floor Panel, Galley etc. 43. Epoxy resins are used for external components due to their good mechanical properties. (A320 Stabilizer, Ailerons etc.) 44. Resins and hardeners The amount of hardener added is critical 45. Epoxies have high adhesion to metals, glass, and ceramics. 46. The appropriate investigation methods are specified in the SRM (Structure Repair Manual), and in the NTM (Non Destructive Test Manual). 47. Damage classification 1-Allowable 2-Repairable or Non repairable 48. Scratches and Gouges affect structural strength and have to be repaired 49. Abrasion is damage to a surface caused by scuffing, rubbing or scraping of the component 50. The effect of a lightning strike depends on the material 51. Delamination is when the separation of plies occurs in a multi-laminate material. 52. Tap-testing is widely used for the quick evaluation of any accessible aircraft surfaces to detect presence of debonding or entrapped water. 53. Radiography is a NDT technique that uses X−rays or gamma rays 54. X-Ray X−rays are a form of electromagnetic radiation similar to light. 55. Gamma rays are similar to X−rays in their characteristics, and are emitted from the nuclear disintegrating of radioactive substances like radium and cobalt 60. 56. All the surface protection (including paint and primer) is to be removed using mechanical methods only. Chemical strippers may cause deterioration of the resin. 57. The repair surface needs to be cleaned and degreased 58. Shelf Life The shelf life is the time which the product is still good in an unopened container and varies from product to product. If the shelf life is exceeded, the resin or catalyst must be discarded as the cure may not achieve sufficient strength. 59. Corrosion of metals occurs due to the tendency of most metals, to return to their natural state 60. Noble metals, such as gold and platinum, do not corrode since they are chemically pure in their natural state 61. Pure aluminium does not have the tendency to corrosion either 62. Steel (except most stainless steels) and other metals, such as brass and bronze, require cadmium plating, zinc plating and aluminium coating etc. 63. Aluminium alloys are usually anodized (a chemical coating) 64. Magnesium and magnesium alloys are highly susceptible to corrosion attack 65. Chemical Corrosion Especially technical acids such as sulphuric acid, sulphurous acid and other aggressive industrial products, which often occur in the atmosphere, are the reason for chemical corrosion in the airframe area 66. Electrochemical corrosion occurs most common between adjacent components, whose metals have different electrochemical potential 67. Corrosion of steel is easily recognized because the corrosion product is red rust.  68. When iron-based alloys corrode, dark corrosion products usually form first on the surface of the metal. hydraulic systems are devided into high-, medium- and low pressure systems, depending on their intended purpose. S At pressures of over 1500 PSI (105 bar) we speak of high pressure lines, S under 1500 PSI (105 bar) medium pressure lines S suction and return lines we speak of low pressure lines. Hydraulic systems work with a system pressure of 3000 PSI CONSTRUCTION STEEL Carbon content 0,05 up to 0,5 %. CARBON STEEL Carbon content 0,5 up to 0,8% This steel can be hardened, is suitable for annealing and surface hardening. The corrosion product of aluminium is a white-grey powdery material which can be removed by mechanical polishing or brushing with materials softer than the metal.