MSE 527 Fall 2011
MSE 527- Mechanical Behavior of Materials Time: Wed 18:30-19:50 PM, Room JD1504 Lecture units: 2.0, Lab design units: 1.0 A survey of relationships between mechanical behavior and materials structure. Elements of creep, fracture and fatigue of metals, ceramics, and composites. Introduction to applied fracture mechanics and environmentally assisted cracking laboratory methods for evaluating structural property relationships, fracture toughness measurements and failure analysis using Scanning Electron Microscopy. Textbook: R. W. Hertzberg, Deformation and Fracture Mechanics of Engineering Materials, 4th Ed., J. Wiley & Sons, 1996. Instructor: Dr. Behzad Bavarian Dept. of Manufacturing Systems Engineering and Management Office: JD3513, 818/677-3917 Email: firstname.lastname@example.org Office Hour: W 5:30-6:15PM Course Description: Prerequisites: MSE 227 and MSE 227L The main techniques used in this course, center around the application of scientific principles to real-life situations. Library research is necessary to develop most of the topic discussions. The course covers dislocation theory and plastic deformation in order to explain strengthening mechanisms in different materials. Materials applications in elevated temperature are studied to understand the design criteria for these applications. Fundamentals of fracture mechanics, microstructure aspects of fracture toughness, transition temperature, environment-assisted cracking, and fatigue crack propagation is discussed to be able to design based on the damage tolerant concept, and failure analysis using scanning electron microscopy. This course requires extensive design problem solving, technical presentation, and a term paper on a current topic in materials application or design.
Course Method and Expectations: The main techniques to be used in this course, center on the application of scientific principles to real-life situations. Library research is necessary to develop most of the topic discussions. Grading Policy Homework 10% Mid-term Exam 30% Term project 15% Final Exam 45% Grading System: Letter Grades Grade Points A Outstanding 4.0 B Excellent 3.0 C Acceptable 2.0 D Passing 1.0 F Failure 0.0 Plus/Minus Grading Last day to drop: Friday, Sept. 16, 2011 References: 1. D. Callister, Jr. Fundamentals of Materials Science and Engineering, J. Wiley & Sons, NY, 2nd Ed. 2005. 2. G. E. Dieter, Mechanical Metallurgy, McGraw-Hill, NY, 1994. 3. V. J. Colangelo and F.A. Meiser, Analysis of Metallurgical Failures, J. Wiley & Sons, NY, 1987. 4. ASM Metals Handbook, Volume 11, Failure Analysis and Prevention, Metals Park, 1986. 5. R. M. Caddell, Deformation and Fracture of Solids, 1980. 6. A. G. Guy, Elements of Physical Metallurgy, 1984.
Materials science deals with basic knowledge about the internal structure, properties and processing of materials. Materials engineering deals with the application of knowledge gained by materials science to convert materials to products. Materials Science and Engineering Materials Science Materials Engineering Basic Knowledge of Materials Applied Knowledge of Materials Resultant Knowledge of Structure and Properties 1-4
Types of Materials • Metallic Materials • Composed of one or more metallic elements. • Example:- Iron, Copper, Aluminum. • Metallic element may combine with nonmetallic elements. • Example:- Silicon Carbide, Iron Oxide. • Inorganic and have crystalline structure. • Good thermal and electric conductors. Metals and Alloys Ferrous Eg: Steel, Cast Iron Nonferrous Eg:Copper Aluminum 1-5
Types of Materials • Polymeric (Plastic) Materials • Organic giant molecules and mostly noncrystalline. • Some are mixtures of crystalline and noncrystalline regions. • Poor conductors of electricity and hence used as insulators. • Strength and ductility vary greatly. • Low densities and decomposition temperatures. • Examples :- Poly vinyl Chloride (PVC), Polyester. • Applications:- Appliances, DVDs, Fabrics etc. 1-6
Types of Materials • Ceramic Materials • Metallic and nonmetallic elements are chemically bonded together. • Inorganic but can be either crystalline, noncrystalline or mixture of both. • High hardness, strength and wear resistance. • Very good insulator. Hence used for furnace lining for heat treating and melting metals. • Also used in space shuttle to insulate it during exit and reentry into atmosphere. • Other applications : Abrasives, construction materials, utensils etc. • Example:- Porcelain, Glass, Silicon nitride. 1-7
Types of Materials • Composite Materials • Mixture of two or more materials. • Consists of a filler material and a binding material. • Materials only bond, will not dissolve in each other. • Mainly two types :- • Fibrous: Fibers in a matrix • Particulate: Particles in a matrix • Matrix can be metals, ceramic or polymer • Examples :- • Fiber Glass ( Reinforcing material in a polyester or epoxy matrix) • Concrete ( Gravels or steel rods reinforced in cement and sand) • Applications:- Aircraft wings and engine, construction. 1-8
Types of Materials • Electronic Materials • Not Major by volume but very important. • Silicon is a common electronic material. • Its electrical characteristics are changed by adding impurities. • Examples:- Silicon chips, transistors • Applications :- Computers, Integrated Circuits, Satellites etc. 1-9
Future Trends • Metallic Materials • Production follows US economy closely. • Alloys may be improved by better chemistry and process control. • New aerospace alloys being constantly researched. • Aim: To improve temperature and corrosion resistance. • Example: Nickel based high temperature super alloys. • New processing techniques are investigated. • Aim: To improve product life and fatigue properties. • Example: Isothermal forging, Powder metallurgy. • Metals for biomedical applications 1-11
Future Trends • Polymeric (Plastic Materials) • Fastest growing basic material (9% per year). • After 1995 growth rate decreased due to saturation. • Different polymeric materials can be blend together to produce new plastic alloys. • Search for new plastic continues. 1-12
Future Trends • Ceramic Materials • New family of engineering ceramics are produced last decade • New materials and applications are constantly found. • Now used in Auto and Biomedical applications. • Processing of ceramics is expensive. • Easily damaged as they are highly brittle. • Better processing techniques and high-impact ceramics are to be found. 1-13
Future Trends • Composite Materials • Fiber reinforced plastics are primary products. • On an average 3% annual growth from 1981 to 1987. • Annual growth rate of 5% is predicted for new composites such as Fiberglass-Epoxy and Graphite-Epoxy combinations. • Commercial aircrafts are expected to use more and more composite materials. 1-14
Future Trends • Electronic Materials • Use of electronic materials such as silicon increased rapidly from 1970. • Electronic materials are expected to play vital role in “Factories of Future”. • Use of computers and robots will increase resulting in extensive growth in use of electronic materials. • Aluminum for interconnections in integrated circuits might be replaced by copper resulting in better conductivity. 1-15
Future Trends • Smart Materials :Change their properties by sensing external stimulus. • Shape memory alloys: Strained material reverts back to its original shape above a critical temperature. • Used in heart valves and to expand arteries. • Piezoelectric materials: Produce electric field when exposed to force and vice versa. • Used in actuators and vibration reducers.
MEMS and Nanomaterials • MEMS: Microelectromechanical systems. • Miniature devices • Micro-pumps, sensors • Nanomaterials:Characteristic length < 100 nm • Examples: ceramics powder and grain size < 100 nm • Nanomaterials are harder and stronger than bulk materials. • Have biocompatible characteristics ( as in Zirconia) • Transistors and diodes are developed on a nanowire.
SUMMARY: BONDING Type Bond Energy Comments Ionic Large! Nondirectional (ceramics) Variable Directional Covalent large-Diamond semiconductors, ceramics small-Bismuth polymer chains) Variable Metallic large-Tungsten Nondirectional (metals) small-Mercury Directional inter-chain (polymer) Secondary smallest inter-molecular 14
FACE CENTERED CUBIC STRUCTURE (FCC) • Close packed directions are face diagonals. --Note: All atoms are identical; the face-centered atoms are shaded differently only for ease of viewing. • Coordination # = 12 Adapted from Fig. 3.1(a), Callister 6e. Click on image to animate (Courtesy P.M. Anderson) 6
BODY CENTERED CUBIC STRUCTURE (BCC) • Close packed directions are cube diagonals. --Note: All atoms are identical; the center atom is shaded differently only for ease of viewing. • Coordination # = 8 Adapted from Fig. 3.2, Callister 6e. Click on image to animate (Courtesy P.M. Anderson) 8
HEXAGONAL CLOSE-PACKED STRUCTURE (HCP) • ABAB... Stacking Sequence • 3D Projection • 2D Projection Adapted from Fig. 3.3, Callister 6e. • Coordination # = 12 • APF = 0.74 10
Mechanical Testing and Properties • Tensile Strength Tensile Test • Flexural Strength Bend Test for brittle materials • Hardness Hardness Test • Toughness Impact Test • Fatigue Life Fatigue Test • Creep rate Creep Test
Mechanical Testing and Properties Tensile Test & the properties obtained from the Tensile Test • Note: in Metals, Yield stress is usually the stress required for dislocations to slip.
Tensile Test & the properties obtained from the Tensile Test Note: Young’s modulus is a measure of the stiffness of the material.
Tensile Test & the properties obtained from the Tensile Test Er=1/2(yield strength)(strain at yielding)
Tensile Test & the properties obtained from the Tensile Test Er=1/2(yield strength)(strain at yielding)
Tensile Test & the properties obtained from the Tensile Test Effect of Temperature
The Bend Test for Brittle Material • Due to the presence of flaw at the surface, • in many brittle materials, the normal tensile • test cannot easily be performed.
6.7 The Impact Test impact strength To evaluate the brittleness of a material subjected to a sudden blow.
6.7 The Impact Test impact strength Impact strength vs. Temperature Note: BCC metals have transition temperature, but most FCC metals do not.
6.7 The Impact Test impact strength Yield Strength: A > B Impact Strength: B > A
The Fatigue Test S-N curve
The Creep Test: Apply stress to a material at an elevated temperature Creep: Plastic deformation at high temperature • a typical creep curve showing the strain produced as • a function of time for a constant stress and temperature.