Materials And Their Applications

MATERIALS DESIGN AND ENGINEERING

Semester II, 2008-09 Indian Institute of Information Technology, Design & Manufacturing Jabalpur

MATERIALS IN AIRCRAFT APPLICATIONS

Materials in Aircraft Applications

Materials in Aircraft Applications Basic Design of an Aircraft Gas Turbine Engine Exhaust Nozzle Inlet Air

Inlet Air Compressor

Combustion Chamber

Turbine

Exhaust Gases

Key Components of a Turbojet Gas Turbine Engine are • A Compressor • A Combustion Chamber • A Turbine

Other elements of the design are An Exhaust Nozzle, A Mixer (which is usually placed between the turbines and the exhaust nozzle An After-Burner

Materials in Aircraft Applications Rotating Compressor Blades

Basic Design Features of the Compressor Section Stationary Compressor Blades

The ambient air is drawn into the compressor and gets pressurized as it is redirected between one set of stators and rotating blades. Thus the compressor pulls air into the engine, raises its temperature and pressure and delivers it to the combustion chamber.

Materials in Aircraft Applications

COMBUSTION CHAMBER

Basic Design Features of the Combustion Chamber and the Turbine

ROTATING TURBINE BLADES MOUNTED ON THE SHAFT

STATIONARY TURBINE BLADES

The compressed high-pressure air is thoroughly mixed with a fine spray of fuel in the combustion chamber and the mixture is ignited. The hot exhaust combustion gases expand rapidly and pass at high speed through the turbine section, which again is an array of rotating blades and stators, and are rejected to the atmosphere through the exhaust nozzle.

Materials in Aircraft Applications

The Carnot Cycle consists of two adiabatic (no gain or loss of heat) and two isothermal processes. For a cyclic heat engine process, the PV diagram will be closed-loop, the area inside the loop representing the amount of work done during the cycle. Not all the heat supplied in the heat enginecan be used to do work.

TH – Temperature of Isothermal Expansion, TC – Temperature of Gas Compression

It is clear that the efficiency of the heat engine can be increased by increasing TH

Materials in Aircraft Applications

The relationship between altitude of cruising and the Mach number of aircraft speed

Materials in Aircraft Applications

Ramjet Engines

Unlike conventional turbojet engines, a ramjet engine provides thrust for an aircraft using no moving part (compressor or turbine). At supersonic speeds the air compresses itself by ramming into a barrier. Therefore, instead of using a compressor to increase the air pressure, a ramjet compresses the air using the speed of the aircraft itself. Even though a ramjet compresses the air entering at supersonic speeds, the air moving through the engine itself must be slowed to subsonic speed to enable efficient combustion. The compressed air is therefore slowed down. It subsequently enters the combustion chamber and exits through the nozzle after burning.

Materials in Aircraft Applications

Scramjet Engines

The term scramjet stands for supersonic combustion ramjet. Scramjet engines work much the same way as ramjets but burn hydrogen instead of hydrocarbon fuel. The hydrogen is stored in the craft as an extremely cold liquid. The liquid hydrogen cools the engine. In the process it is warmed enough to become a gas, which serves as the fuel. The difference between a ramjet and a scramjet is that the fuel in scramjet is combusted while the air is at supersonic speeds and therefore does not require to be slowed down.

Materials in Aircraft Applications

THE FUSELAGE

The fuselage, in essence, is the body of the airplane and holds all the pieces together. The fuselage, along with the passengers and cargo, contribute a significant portion of the weight of an aircraft. The center of gravity of the aircraft is the average location of the weight and it is usually located inside the fuselage. In flight, the aircraft rotates around the center of gravity because of torques generated by the elevator, rudder, and ailerons. The fuselage must be designed with enough strength to withstand these torques.

Materials in Aircraft Applications Important Landmarks 1903 Wright Brothers

History of Materials Usage in Aircrafts

Wood, Metallic wires, Fabric (Glider Materials)

1912 Hans Reissner

First all-metal monoplane, wings made from Al

1940s

Al alloy airframe, Turbine Blades from Fe-35Ni15Cr-2Ti Steel/ Nimonic 80 (Ni-20Cr-2.5Ti)

1950s

Increased use of Superalloys for engine components, beginning of Ti alloys for frame

1960s

Development of advanced superalloys, beginning of (α+ β) Ti alloys for engine parts

1970s

FRP Composites for Airframe Applications

1980s

Single Crystals and DS superalloys for blades

1990s

Intermetallics, Ceramics, Advanced Composites

Materials in Aircraft Applications

C/CC, CMC MMC, Whisker REG Gr-EP, Gr-PI, Gr-TP B-EP Titanium Skins & Forgings, SPF/DB SS & Superalloys, PM-HIP, SPF/DB

High Strength Steel Forgings Mg Sheet Casting A Stresses Skin, Al-Li Alloys, Superplastic Forming/DB Steel or Al Framing Wood Monocoque Wood, Wire, Fabric

1920

1940

1960

1980

2000

2020

Materials in Aircraft Applications

Design-Limiting Properties of Materials

Elastic Modulus (Yong’s, Shear and Bulk) Strength (Yield, Tensile and Fracture) Hardness MECHANICAL PROPERTIES

Toughness Fracture Toughness Damping Capacity Fatigue Endurance Limit Creep Resistance Stress Rupture Strength

Materials in Aircraft Applications

Design-Limiting Properties of Materials

Thermal Conductivity Thermal Diffusivity Specific Heat THERMAL PROPERTIES

Melting Point Thermal Expansion Coefficient Thermal Shock Resistance Glass Transition Temperature

Materials in Aircraft Applications

Design-Limiting Properties of Materials

WEAR

Archard’s Wear Constant

CORROSION

Corrosion Rate

OXIDATION

Oxidation Rate

DENSITY

COST

Microchips are made of large number of small transistors (circuit elements).

Manufacturing in Si Age

Chip Design and Scale of its magnitude Historically circuits are measured in microns 1 micron – 1/1000 of 1 mm Approximately 70 times smaller than the width of a human hair Today’s advanced technologies are measured in terms of nanometers 1 nanometer = 1/1000 of a micrometer That is thousands of times smaller than the width of a human hair

Inside the Chip The inside of the chip consists of various kinds of thin films and layers which need to be deposited/ created on the silicon wafer substrate.

Manufacturing Steps for Mico/Nano Chip Making

Manufacturing of a micro/nano chip goes in sequential steps. Part of the Process Flow chart is shown here

Manufacturing Steps for Mico/Nano Chip Making

BONE IMPLANTS How Materials Engineers Affect Technological Developments in the Field of Bio-Materials

ES 103: II Semester, 2007-08 Instructor Incharge: Dr S Bhargava

Functions of Bones in Human Body The bones of the skeleton perform several functions: • Provide support • Provide protection of internal organs from mechanical damage (e.g., skull, ribs) • Serve as reservoir of calcium and phosphate • Since all types of blood cells are produced in the bone marrow (some 1011 of them each day in an adult human), bones also serve as the source of blood cells.

HOW DOES A HIP JOINT FUNCTION? The hip is a ball and socket joint. It comprises of two main parts: The Femur and The Pelvis The femur is the thighbone and forms a ball at its tip. The socket, a part of the pelvis, is called the acetabulum. The joint operates with the femoral ball fitting into the acetabulum. A smooth layer of cartilage and a thin layer of synovial fluid (lubricant) form between the ball and socket and ensure that bones are able to move in a nearly frictionless environment.

FAILURE OF THE HIP JOINT • The most common cause of the hip joint failure is osteoarthritis. • Osteoarthritis occurs in middle-aged or elderly individuals when the cartilage and synovial fluid in the hip joint gradually dissipate due to wear and tear over an extensive period of time. • This causes the underlying bone to become exposed.

Pain results as the femoral ball and the acetabulum rub directly against each other.

OTHER REASONS OF HIP JOINT FAILURE A common cause of hip pain is inflammation of the joints. Inflammation increases pressure within the joint, damaging the cartilage lining of the hip. This can be caused by a variety of conditions: Rheumatoid arthritis is the general inflammation of joints. Avascular necrosis is often the result of alcohol abuse. It decreases the blood supply to the hip, which causes the bone around the joint to die from lack of nourishment. Other causes of hip malfunction are trauma to the joint and dislocation of the femoral ball from the acetabulum cup.

HIP ANTHROPLASTY: HIP REPLACEMENT SURGERY •

In an injured hip, the primary damage exists on the upper femoral ball,

Surgery begins with the removal of the deteriorated femoral head.

The ball is dislocated from the acetabulum and then removed by cutting through the femoral neck,

HIP ANTHROPLASTY The femoral canal is then prepared so that a prosthetic femoral stem can replace the removed portion of the femur

The core of the mostly hollow femur is cleaned and enlarged in the shape of the implant stem

Acetabulum is also prepared by cleaning and enlarging with circular reamers of gradually increasing size

HIP ANTHROPLASTY The new acetabular shell is implanted securely within the prepared The plastic inner hemispherical socket. portion of the implant is placed within the metal shell and fixed into place.

The new femoral stem is then inserted

THE HIP ANTHROPLASTY IS DONE

HOW DOES IMPLANT LOOK AFTER THE SURGERY IS DONE?

DESIGN OF HIP IMPLANTS THE IMPLANT COMPRISES OF THREE PARTS Femoral Ball

Femoral Stem

Acetabular Socket

HIP IMPLANT DESIGNS

Both, STEM as well as BALL, can be parts of a single piece implant

STEM and BALL can be manufactured from two different materials and can then be joined together

HIP IMPLANT DESIGNS In addition, the design of the HIP implant may be based on the three different following approaches for joining:

CEMENTED IMPLANTS CEMENTLESS IMPLANTS HYBRID IMPLANTS

CEMENTED HIP IMPLANTS When a bonding material is used to coat the implant stem before placing into the hollow femoral canal, the implant is known as the CEMENTED IMPLANT. Cemented fixing relies on a stable interface between the prosthesis and the cement, on one hand, and a solid mechanical bond between the cement and the bone on the other. Unless the material for cementing is chosen carefully, the cement may loosen and fail with time.

LOOSENING OF CEMENTED HIP IMPLANTS CONTRIBUTION OF MECHANICAL PROCESSES: •In patients who are very active or very heavy, cracks (fatigue fractures) can result in the cement over extended period of usage.These cracks can loosen the prosthetic stem which, in turn, becomes unstable. The friction of the ball against the acetabular socket creates wear debris. The generated wear debris particles can then trigger a biological response that further contributes to loosening of the implant and sometime to loss of bone around the implant.

LOOSENING OF CEMENTED HIP IMPLANTS CONTRIBUTION OF BIOLOGICAL PROCESSES: •The microscopic debris particles are absorbed by cells around the joint and initiate an inflammatory response from the body, which tries to remove them. •This inflammatory response can also cause cells to remove bits of bone around the implant, a condition called OSTEOLYSIS. •As the bone weakens, the instability increases. Progressing from the edges of the implant, bone loss can occur around both the acetabulum and the femur.

CEMENTLESS HIP IMPLANTS Research has shown that bone will attach to a metal implant if the surface of the metal has a surface topography that is conducive to attracting new bone growth.

Human Cancellous Bone structure containing interconnected pores (100X)

Porous structure produced on the Stem/Acetabular surface (100X)

CEMENTLESS HIP IMPLANTS The coarse and gritty exterior of the stem allows the bone to essentially grow into the surface of the implant.

An acetabular socket having surface topography that resembles the porous structure of bone

The porous coating, when combined with the surface topography of the stem implant, is conducive to bone growth, allowing it to achieve fixation within the bone.

MATERIALS AND THEIR SELECTION FOR

PRODUCING HIP IMPLANTS

PROPERTY REQUIREMENTS FROM HIP IMPLANT MATERILAS •

They must have mechanical properties that duplicate the structures they are intended to replace; Thus they must be strong enough to take weight bearing loads, flexible enough to bear stress without breaking and able to move smoothly against each other as required,

•

They resist to corrosion, degradation and wear whereby they retain their strength and shape for a long time. Proper joint functioning would otherwise be affected,

•

They must be biocompatible, i.e., they function in the body without creating either a local or a systemic rejection response,

•

They meet the highest standards of fabrication and quality control at a reasonable cost.

RAIL WHEELS Rail wheels serve several functions: •

They support the bogey weight,

•

They steer the vehicle through curves,

•

They also serve as heat sinks during on-tread braking. The service loading conditions of wheels include those due to wheel-on-rail contact as well as thermal loads from frictional heating during on-tread braking.

The Loading Pattern

Wheel Rim

Wheel Plate

Rail

Wheel Flange

The loading of the rail as well the wheel is cyclic in nature. Frictional heating at the point of contact between the rails and the wheel increases the temperature. Estimates of the surface temperature vary. It is usually suggested that the surface temperature increases to about 400 – 500oC. Detailed microstructural studies of grain sizes and deformation, however, suggest that the temperature goes as high as 1000oC.

Wheel Manufacturing by Forging Starting cylindrical Steel Block

Wheel Blank

Intermediate Wheel Shape

Final Wheel Shape

Post Forging Heat Treatment

Schematic Representation of Three Rail Wheel Designs Flange Rim

Plate

Hub

Straight Plate

S-Plate

Freight Wheel

Nuclear Energy

Principle of Nuclear Power Generation

Principle of Nuclear Power Generation Steam

Steam produced

Generator Turbine

Electricity Heat

Boiling Water Reactor (BWR)

Reactor Design Containment Vessel 1.5-inch thick steel

Shield Building Wall 3 foot thick reinforced concrete

Dry Well Wall 5 foot thick reinforced concrete

Bio Shield 4 foot thick leaded concrete with 1.5-inch thick steel lining inside and out

Reactor Vessel 4 to 8 inches thick steel

Reactor Fuel Weir Wall 1.5 foot thick concrete

Core of the Reactor

One of the Bundles of the Reactor Core

Nuclear Fuel UO2 Pellets

World Uranium Production

Process Planning

Process R&D

Process Selection, Process Design, Process Parameters, Tools & Dies, Quality Control

Process Modeling & Optimization

Processing

Production Preparation Assembly Drawings Part Drawings Make/Buy Decisions

Product Design

Parts Manufacturing, Sensing and Corrective Action Taking; Storing, Moving and Handling

COMMON DATABASE FOR CAD AND CAM

Assembly

Industrial Design Mechanical Design & Elelctrical Analysis Materials Product R&D

Production Control

Dispatching

Product Concept Market Forecast Market Research

Routing, Scheduling, Production Tracking, Inventory Control, Purchasing, Receiving, Quality Assurance

Customer Service Disposal/Recycling