# Mechanical behavior of crystalline materials - Stress Types and Tensile Behaviour

Size: px
Start display at page:

Download "Mechanical behavior of crystalline materials - Stress Types and Tensile Behaviour"

Transcription

1 Mechanical behavior of crystalline materials - Stress Types and Tensile Behaviour 3.1 Introduction Engineering materials are often found to posses good mechanical properties so then they are suitable for applications. Mechanical properties referred here are tensile strength, ductility, toughness, fatigue strength, hardness etc. Ductility is estimated from uniaxial tensile test. Percentage reduction in area obtained from uniaxial tensile test is taken to be a measure of ductility. In this lecture, we will focus on tensile behavior of materials. Metallic materials have good ductility. They are easily deformable by application of external forces. Formability, the ease with which metals and alloys can be plastically deformed to a required shape depends on the nature of structure, grain structure and types of metallurgical phases that make a given alloy. For example a hardened steel which has a martensitic structure is impossible to shape. Forming of materials can be achieved through plastic deformation of the material by applying stress. Therefore, it is important to understand the plastic deformation behavior of materials. Material behavior under three different types of loading, tensile, compressive and torsion loading will be discussed in the following sections. 3.2 Stresses types: Suppose a certain force ΔF is acting on an area ΔA. Then the stress acting along an arbitrary direction is given as = This stress can be resolved along a direction perpendicular to the given surface called normal stress, σ. It is resolved along tangential direction to the given surface, called shear stress, τ. Normal stress can produce both normal and shear strains in a material. Shear stress produces shear strain. Normal Strain is the change in length divided by original length. Shear strain is the angular change of a right angle edge of the solid. 3.3 Tensile behavior: 3.3.1: The uniaxial tension test Tension test is a simple test used for finding the strength of materials. A round rod specimen, gripped on ends and is subjected to increasing axial load. The stress applied is measured using load cell. Strain on the specimen is measured using extensometer. A metallic material, when loaded in tension, initially deforms elastically. Elastic deformation refers to material strain Joint Initiative of IITs and IISc Funded by MHRD Page 3 of 13

2 which can be recovered fully. In elastic deformation, the nominal stress which is the load applied divided by the initial area of cross section of the rod, increases linearly with strain. Engineering strain is defined as change in length divided by initial gage length. True strain is defined as change in length divided by instantaneous gage length. Engineering stress or nominal stress is the load applied divided by initial cross section area of the rod. In the elastic region, the linear stress strain relation is given by Hooke s law: σ = εe The modulus of elasticity, E is a material property, which depends on the nature of bonding in a material. Typical value of E for steels is in the range GPa, whereas for aluminium, it ranges from 69 to 79 GPa. Elastic Poisson ratio is defined as ratio of linear [elongation] strain to lateral strain[contraction]. Poisson s ratio for steels ranges from 0.28 to Maximum value of Poisson s ratio is 0. Typical stress-strain curves for ductile materialswith pronounced yielding and without yielding shown below: Engi nee ring stre ss, S Yield point Start of necking 0.2 % Off set line Start of necking Engineering strain, e Fig : Engineering and true stress-strain curves for a ductile material From the tensile curve on can find many properties of the material. Beyond the elastic limit (linear), the material behavior is said to be plastic. The deformation in plastic behavior is permanent. Plastic deformation commences after elastic deformation, which is represented in Joint Initiative of IITs and IISc Funded by MHRD Page 4 of 13

3 stress-strain diagram by yielding. Some materials do not show yielding materials such as copper. Fig : Tensile test setup and tensile specimen Fig : Standard (ASTM E8) Tensile Specimens of plate and cylindrical types Joint Initiative of IITs and IISc Funded by MHRD Page 5 of 13

4 The stress at yield point is called yield strength. In case of materials which do not show pronounced yielding, the yield point strength is defined by 0.2% proof strength. This is obtained by 0.2% offset on the strain. Yield point stress is important in case of metal forming operations, because, forming processes require the metal to deform plastically. The area under the stress-strain curve upto yielding is called Modulus of resilience [MR]. MR = Y 2 /2E, Y being the yield strength. Springs should have high modulus of resilience, so that they can absorb more energy during elastic deformation and store it. The plastic portion of the stress-strain curve is non-linear. As the specimen gets loaded beyond yield point, the curve reaches a maximum. The stress corresponding to this maximum point known as ultimate tensile strength [ UTS]. UTS = F max /A o Until this point there is uniform reduction in area of cross section of the specimen. After the point of maximum engineering stress, with continued loading, the specimen forms a neck which has low area of cross-section due to concentration of stress locally. Necking is localized deformation. After necking begins, the deformation is restricted to necked region alone. With further loading, the engineering stress drops beyond necking point, till the point of fracture. Fracture essentially occurs at the necked region, due to triaxial state of stress in the neck region. Also because the material cross-section in the neck region is very small. The strain at the point of fracture is called total strain. Some of the useful mechanical properties of the material, which is being subjected to tensile loading, that can be evaluated from the stress-strain behaviour are: a] Yield strength, b] Ultimate strength, c] Percentage elongation and percentage area reduction. Ductility of a material is defined as percentage elongation or percentage reduction in area of cross-section. The percent elongation is defined as [l f -l o ]/l o, and the percentage reduction in area = [A o -A f ]/A o X 100. For metals, elongation may range from 10% to 60% and reduction in area may range from 20% to 90%. For some metals tensile properties are listed below: Joint Initiative of IITs and IISc Funded by MHRD Page 6 of 13

5 Table : Tensile properties of some alloys Material Yield strength, MPa Tensile strength, MPa % Elongation Low carbon steel Annealed aluminium Cold worked aluminium Alloy steels Austenitic stainless steel True stress is defined as ratio of load applied to instantaneous cross-section area, σ = P/A. True strain is defined as change in gage length divided by instantaneous gage length. It is given as: ε = = ln(l/l o ) = 2ln[D o /D]. For small strains, we can take both engineering and trues strains to be equal. However, true strains are more consistent with real phenomena. Advantage of using true strain is apparent from the fact that total true strain is equal to sum of incremental true strains. Moreover, volume strain can be given as sum of the three normal true strains. True strains for equivalent amount of tensile and compressive deformations are equal, only differing in sign. True stress and engineering stress are related by the expression: σ= S (1+ e ), where S is engineering stress, e is engineering strain. Similarly, relation between engineering strain e and true strain ε is given as: ε = ln(1+e) True strain is what happens naturally. Flow stress:metal forming operations involve plastic deformation of materials. The stress required to sustain a given amount of plastic deformation (plastic strain) is called flow stress. Flow stress is an important parameter in forming. It depends on type of material, temperature of working, conditions of friction at workpiece tool interface, tool and work piece geometry etc. Joint Initiative of IITs and IISc Funded by MHRD Page 7 of 13

6 3.3.2 True stress true strain curve: Tru e stre ss, σ Fig : True stress- true strain curve True strain, ε True stress-strain curve does not indicate any yield point. It also does not show the elastic region. The total area under the true stress-strain curve is known as toughness. Toughness =, where ε is the fracture strain. The true stress true strain relation in the plastic portion is given by the power law expression: σ = kε Stress required,σ in plastic range to maintain plastic deformation at a certain strain, ε is called flow stress. σ n where k is strength coefficient, n is called strain hardening exponent. ε When the true stress is plotted against true strain on log-log plane, the power law relation, becomes a straight line. Slope of the line is n. n is called strain hardening exponent. K, the strength coefficient is the value of stress σ, under ε=1. During plastic deformation, as the ultimate strength is reached, the localized deformation called necking begins. This is called point of instability, as the specimen is no longer able to support the load. It can be shown that at the point of instability, n = ε u, where ε u is strain at Joint Initiative of IITs and IISc Funded by MHRD Page 8 of 13

7 ultimate point. At the neck, triaxial state of stress is known to exist, due to larger area reduction. Axial stress varies across the specimen in the neck region Necking begins when the true strain is equal to the strain hardening exponent. That is n = ε Higher the value of n, higher the strain the material can withstand before necking. During instability, the material becomes stronger due to strain hardening. However, the localized reduction in area makes the specimen less capable of bearing the load. The rate of decrease in area is more than rate of increase in strength due to strain hardening, thereby leading to instability. This is called geometric softening. Instability due to necking may pose problems during forming of sheet metals. σ 3.3.3: Different types of stress-strain curves: σ=y Y σ ε a] b] c] d] Fig : Stress-strain behavior of different types of materials ε Perfectly elastic: Figure a, Brittle materials such as glass, ceramics, cast irons etc show only perfectly elastic behavior. There is very negligible yielding. Hooke s law governs the stressstrain relation. Stiffness of such material is indicated by E. Rigid plastic, figure b has infinite value of E, Once stress level reaches yielding Y, it continues to deform at same stress level. Elastic, perfectly plastic-fugure c - is combination of perfectly elastic and rigid plastic. This material will undergo elastic recovery upon unloading. Metals heated to high temperature behave this way. Lead has elastic, perfectly plastic at room temperature. Elastic, linearly strain hardening material, figure d It approximates many of engineering materials. Such material has linear elastic behavior and linear plastic behavior. Due to strain hardening, the flow stress increases with increasing strain. Joint Initiative of IITs and IISc Funded by MHRD Page 9 of 13

8 3.3.4 Factors affecting the stress-strain behavior Temperature and strain rate influence greatly the stress-strain behavior of materials. Increasing the temperature reduces the tensile strength, yield strength, increases ductility. Tensile strength σ Low temperature Stre ss Yield strength High temperature Elongation Temperature ε Fig : Effect of temperature on mechanical properties and stress-strain behaviour Strain rate effect Strain rate is the rate at which material gets strained. Strain rate is expressed in s -1. Deformation speed of material in a process of forming is expressed in m/s. Engineering strain rate is defined as, where v is velocity or deformation speed of the process, l True strain rate is o is initial length. V is ram speed in tensile testing. True strain rateis dependent on velocity and instantaneous length. In order to maintain constant strain rate during tensile test, velocity of the cross head of the tensile machine has to be increased. Increasing the strain rate increases the tensile strength. Increasing the temperature reduces the strength. Joint Initiative of IITs and IISc Funded by MHRD Page 10 of 13

9 At higher temperatures, the sensitivity of strength to strain rate increases strength becomes more sensitive to changes in strain rate. This is shown in figure below: The flow stress is strongly dependent on strain rate at elevated temperatures. Room temperature 400 o C Fl o w st re 800 o C 1200 o C Strain rate, s -1 Fir : Variation of flow stress with temperature and strain rate Velocity of deformation and strain rate of deformation during forming operations are deciding factors for selection of forming process and forming press. There are forming processes which are carried out at high strain rates and high velocities. Such processes are called high velocity forming. Example is explosive forming. Strain rate and deformation velocity for some of the forming operations are given in table below: Joint Initiative of IITs and IISc Funded by MHRD Page 11 of 13

10 Table : Strain rates and velocities in some forming operations Process True strain Deformation speed, Strain rate, s -1 m/s Cold forging, rolling Cold wire drawing Hot forging, rolling Hot extrusion Sheet metal forming Strain rate dependence of flow stress or tensile strength, can be represented by the expression: (, m is strain rate sensitivity parameter and is strain rate. In general, the value of m decreases as strength increases. With higher values of m, a material can undergo more plastic deformation before necking or failure. The material near the necking becomes stronger due to work hardening, at the instance of necking. Strain rates near necking are also high. As a result, Necking gets delayed. There is large uniform deformation before failure.elongation after necking also increases due to large values of m. Superplastic behavior of some materials is possible only if the strain rate sensitivity for a material is high 0.3 to Superplastic behavior is the ability of materials to undergo very large amounts of elongations upto 1000% elongation, before failure. There is also no necking in such behavior as m values are high. Examples are thermoplastics, hot glass, fine grained titanium alloy, zinc-aluminium alloy. Strain rate also affects the strain hardening exponent of materials. Strain hardening exponent decreases with increase in strain rate. Generally ductility of materials is dependent on strain rate sensitivity parameter, m Hydrostatic stress: Hydrostatic stress refers to a state of stress in which the stress acting along all the three directions is the same and of the same sign. Hydrostatic stress cannot cause yielding of conventional materials, because the plastic deformation of crystalline materials is caused by mechanism of slip. Slip is essentially caused by shear force. Joint Initiative of IITs and IISc Funded by MHRD Page 12 of 13

11 Hydrostatic stressis found to influence the plastic deformation process by affecting material property. Hydrostatic stress leads to increase in ductility of a material. Hydrostatic stress increases true fracture strain. However, it has no effect on necking, maximum stress, strain. Hydrostatic stress is found to increase the ductility of brittle materials like cast iron, ceramics. In metal forming operations, large strains are involved, true strains exceeding 3 to 4. Therefore, simple tensile test and the results obtained from the same are not sufficient to predict the flow stress of materials. Homogeneous compression test, torsion test, plane strain compression test are some of the tests which are used for determination of the flow stress. These tests are discussed in next lecture. Joint Initiative of IITs and IISc Funded by MHRD Page 13 of 13

### Chapter 2: Mechanical Behavior of Materials

Chapter : Mechanical Behavior of Materials Definition Mechanical behavior of a material relationship - its response (deformation) to an applied load or force Examples: strength, hardness, ductility, stiffness

### CE 221: MECHANICS OF SOLIDS I CHAPTER 3: MECHANICAL PROPERTIES OF MATERIALS

CE 221: MECHANICS OF SOLIDS I CHAPTER 3: MECHANICAL PROPERTIES OF MATERIALS By Dr. Krisada Chaiyasarn Department of Civil Engineering, Faculty of Engineering Thammasat university Outline Tension and compression

### Mechanical behavior of crystalline materials- Comprehensive Behaviour

Mechanical behavior of crystalline materials- Comprehensive Behaviour In the previous lecture we have considered the behavior of engineering materials under uniaxial tensile loading. In this lecture we

### Chapter 4 MECHANICAL PROPERTIES OF MATERIAL. By: Ardiyansyah Syahrom

Chapter 4 MECHANICAL PROPERTIES OF MATERIAL By: Ardiyansyah Syahrom Chapter 2 STRAIN Department of Applied Mechanics and Design Faculty of Mechanical Engineering Universiti Teknologi Malaysia 1 Expanding

### True Stress and True Strain

True Stress and True Strain For engineering stress ( ) and engineering strain ( ), the original (gauge) dimensions of specimen are employed. However, length and cross-sectional area change in plastic region.

### MECHANICAL PROPERTIES OF MATERIALS

MECHANICAL PROPERTIES OF MATERIALS Stress-Strain Relationships Hardness Effect of Temperature on Properties Fluid Properties Viscoelastic Behavior of Polymers Mechanical Properties in Design and Manufacturing

### Types of Strain. Engineering Strain: e = l l o. Shear Strain: γ = a b

Types of Strain l a g Engineering Strain: l o l o l b e = l l o l o (a) (b) (c) Shear Strain: FIGURE 2.1 Types of strain. (a) Tensile. (b) Compressive. (c) Shear. All deformation processes in manufacturing

### FME201 Solid & Structural Mechanics I Dr.Hussein Jama Office 414

FME201 Solid & Structural Mechanics I Dr.Hussein Jama Hussein.jama@uobi.ac.ke Office 414 Lecture: Mon 11am -1pm (CELT) Tutorial Tue 12-1pm (E207) 10/1/2013 1 CHAPTER OBJECTIVES Show relationship of stress

### Fundamental Course in Mechanical Processing of Materials. Exercises

Fundamental Course in Mechanical Processing of Materials Exercises 2017 3.2 Consider a material point subject to a plane stress state represented by the following stress tensor, Determine the principal

### 11/2/2018 7:58 PM. Chapter 6. Mechanical Properties of Metals. Mohammad Suliman Abuhaiba, Ph.D., PE

1 Chapter 6 Mechanical Properties of Metals 2 Assignment 7, 13, 18, 23, 30, 40, 45, 50, 54 4 th Exam Tuesday 22/11/2018 3 WHY STUDY Mechanical Properties of Metals? How various mechanical properties are

### where n is known as strain hardening exponent.

5.1 Flow stress: Flow stress is the stress required to sustain a certain plastic strain on the material. Flow stress can be determined form simple uniaxial tensile test, homogeneous compression test, plane

### The strength of a material depends on its ability to sustain a load without undue deformation or failure.

TENSION TEST The strength of a material depends on its ability to sustain a load without undue deformation or failure. This strength is inherent in the material itself and must be determined by experiment.

### MECHANICAL PROPERTIES AND TESTS. Materials Science

MECHANICAL PROPERTIES AND TESTS Materials Science Stress Stress is a measure of the intensity of the internal forces acting within a deformable body. Mathematically, it is a measure of the average force

### MECHANICAL PROPERTIES PROPLEM SHEET

MECHANICAL PROPERTIES PROPLEM SHEET 1. A tensile test uses a test specimen that has a gage length of 50 mm and an area = 200 mm 2. During the test the specimen yields under a load of 98,000 N. The corresponding

### High Temperature Materials. By Docent. N. Menad. Luleå University of Technology ( Sweden )

of Materials Course KGP003 Ch. 6 High Temperature Materials By Docent. N. Menad Dept. of Chemical Engineering and Geosciences Div. Of process metallurgy Luleå University of Technology ( Sweden ) Mohs scale

### ME -215 ENGINEERING MATERIALS AND PROCESES

ME -215 ENGINEERING MATERIALS AND PROCESES Instructor: Office: MEC325, Tel.: 973-642-7455 E-mail: samardzi@njit.edu PROPERTIES OF MATERIALS Chapter 3 Materials Properties STRUCTURE PERFORMANCE PROCESSING

### 3. Mechanical Properties of Materials

3. Mechanical Properties of Materials 3.1 Stress-Strain Relationships 3.2 Hardness 3.3 Effect of Temperature on Properties 3.4 Fluid Properties 3.5 Viscoelastic Properties Importance of Mechanical Properties

### ME 212 EXPERIMENT SHEET #2 TENSILE TESTING OF MATERIALS

ME 212 EXPERIMENT SHEET #2 TENSILE TESTING OF MATERIALS 1. INTRODUCTION & THEORY The tension test is the most commonly used method to evaluate the mechanical properties of metals. Its main objective is

### BFF1113 Engineering Materials DR. NOOR MAZNI ISMAIL FACULTY OF MANUFACTURING ENGINEERING

BFF1113 Engineering Materials DR. NOOR MAZNI ISMAIL FACULTY OF MANUFACTURING ENGINEERING Course Guidelines: 1. Introduction to Engineering Materials 2. Bonding and Properties 3. Crystal Structures & Properties

### Chapter 7: Mechanical Properties 1- Load 2- Deformation 3- Stress 4- Strain 5- Elastic behavior

-1-2 -3-4 ( ) -5 ( ) -6-7 -8-9 -10-11 -12 ( ) Chapter 7: Mechanical Properties 1- Load 2- Deformation 3- Stress 4- Strain 5- Elastic behavior 6- Plastic behavior 7- Uniaxial tensile load 8- Bi-axial tensile

### MECHANICAL PROPERTIES. (for metals)

MECHANICAL PROPERTIES (for metals) 1 Chapter Outline Terminology for Mechanical Properties The Tensile Test: Stress-Strain Diagram Properties Obtained from a Tensile Test True Stress and True Strain The

### Tensile Testing. Objectives

Laboratory 3 Tensile Testing Objectives Students are required to understand the principle of a uniaxial tensile testing and gain their practices on operating the tensile testing machine to achieve the

CIVE.3110 Engineering Materials Laboratory Fall 2017 Tensile/Tension Test Advanced Topics Tzuyang Yu Associate Professor, Ph.D. Structural Engineering Research Group (SERG) Department of Civil and Environmental

### CHAPTER 3 OUTLINE PROPERTIES OF MATERIALS PART 1

CHAPTER 3 PROPERTIES OF MATERIALS PART 1 30 July 2007 1 OUTLINE 3.1 Mechanical Properties 3.1.1 Definition 3.1.2 Factors Affecting Mechanical Properties 3.1.3 Kinds of Mechanical Properties 3.1.4 Stress

### CHAPTER 4 1/1/2016. Mechanical Properties of Metals - I. Processing of Metals - Casting. Hot Rolling of Steel. Casting (Cont..)

Processing of Metals - Casting CHAPTER 4 Mechanical Properties of Metals - I Most metals are first melted in a furnace. Alloying is done if required. Large ingots are then cast. Sheets and plates are then

### Tensile/Tension Test Fundamentals

CIVE.3110 Engineering Materials Laboratory Fall 2016 Tensile/Tension Test Fundamentals Tzuyang Yu Associate Professor, Ph.D. Structural Engineering Research Group (SERG) Department of Civil and Environmental

### When an axial load is applied to a bar, normal stresses are produced on a cross section perpendicular to the axis of the bar.

11.1 AXIAL STRAIN When an axial load is applied to a bar, normal stresses are produced on a cross section perpendicular to the axis of the bar. In addition, the bar increases in length, as shown: 11.1

### MECHANICS OF MATERIALS. Mechanical Properties of Materials

MECHANICS OF MATERIALS Mechanical Properties of Materials By NUR FARHAYU ARIFFIN Faculty of Civil Engineering & Earth Resources Chapter Description Expected Outcomes Understand the concept of tension and

### Chapter 7. Mechanical properties 7.1. Introduction 7.2. Stress-strain concepts and behaviour 7.3. Mechanical behaviour of metals 7.4.

Chapter 7. Mechanical properties 7.1. Introduction 7.2. Stress-strain concepts and behaviour 7.3. Mechanical behaviour of metals 7.4. Mechanical behaviour of ceramics 7.5. Mechanical behaviour of polymers

### NDT Deflection Measurement Devices: Benkelman Beam (BB) Sri Atmaja P. Rosyidi, Ph.D., P.E. Associate Professor

NDT Deflection Measurement Devices: Benkelman Beam (BB) Sri Atmaja P. Rosyidi, Ph.D., P.E. Associate Professor NDT Deflection Measurement Devices on Pavement Structure NDT measurement of pavement surface

### CITY AND GUILDS 9210 Unit 130 MECHANICS OF MACHINES AND STRENGTH OF MATERIALS OUTCOME 1 TUTORIAL 1 - BASIC STRESS AND STRAIN

CITY AND GUILDS 910 Unit 130 MECHANICS O MACHINES AND STRENGTH O MATERIALS OUTCOME 1 TUTORIAL 1 - BASIC STRESS AND STRAIN Outcome 1 Explain static equilibrium, Newton's laws, and calculation of reaction

### Mechanical Properties

Stress-strain behavior of metals Elastic Deformation Plastic Deformation Ductility, Resilience and Toughness Hardness 108 Elastic Deformation bonds stretch δ return to initial Elastic means reversible!

### CE205 MATERIALS SCIENCE PART_6 MECHANICAL PROPERTIES

CE205 MATERIALS SCIENCE PART_6 MECHANICAL PROPERTIES Dr. Mert Yücel YARDIMCI Istanbul Okan University Deparment of Civil Engineering Chapter Outline Terminology for Mechanical Properties The Tensile Test:

### Chapter Outline Mechanical Properties of Metals How do metals respond to external loads?

Chapter Outline Mechanical Properties of Metals How do metals respond to external loads?! Stress and Strain " Tension " Compression " Shear " Torsion! Elastic deformation! Plastic Deformation " Yield Strength

### Chapter 8: Mechanical Properties of Metals. Elastic Deformation

Chapter 8: Mechanical Properties of Metals ISSUES TO ADDRESS... Stress and strain: What are they and why are they used instead of load and deformation? Elastic behavior: When loads are small, how much

### Engineering Materials

Engineering Materials Mechanical Properties of Engineering Materials Mechanical testing of engineering materials may be carried out for a number of reasons: The tests may simulate the service conditions

### Deformation, plastic instability

Deformation, plastic instability and yield-limited design Engineering Materials 2189101 Department of Metallurgical Engineering Chulalongkorn University http://pioneer.netserv.chula.ac.th/~pchedtha/ Material

### SMU 2113 ENGINEERING SCIENCE. PART 1 Introduction to Mechanics of Materials and Structures

SMU 2113 ENGINEERING SCIENCE PART 1 Introduction to Mechanics of Materials and Structures These slides are designed based on the content of these reference textbooks. OBJECTIVES To introduce basic principles

### Chapter 6: Mechanical Properties: Part One

Slide 1 Chapter 6: Mechanical Properties: Part One ` 6-1 Slide 2 Learning Objectives 1. Technological significance 2. Terminology for mechanical properties 3. The tensile test: Use of the stress strain

### WEEK FOUR. This week, we will Define yield (failure) in metals Learn types of stress- strain curves Define ductility.

WEEK FOUR Until now, we Defined stress and strain Established stress-strain relations for an elastic material Learned stress transformation Discussed yield (failure) criteria This week, we will Define

### Chapter 6: Mechanical Properties

Chapter 6: Mechanical Properties ISSUES TO ADDRESS... Stress and strain: What are they and why are they used instead of load and deformation? Elastic behavior: When loads are small, how much deformation

### Materials Engineering 272-C Fall 2001, Lectures 9 & 10. Introduction to Mechanical Properties of Metals

Materials Engineering 272-C Fall 2001, Lectures 9 & 10 Introduction to Mechanical Properties of Metals From an applications standpoint, one of the most important topics within Materials Science & Engineering

### Part IA Paper 2: Structures and Materials MATERIALS Examples Paper 3 Stiffness-limited Design; Plastic Deformation and Properties

Engineering Part IA Paper 2: Structures and Materials MATERIALS FIRST YEAR Examples Paper 3 Stiffness-limited Design; Plastic Deformation and Properties Straightforward questions are marked with a Tripos

### Today s Topics. Plastic stress-strain behaviour of metals Energy of mechanical ldeformation Hardness testing Design/safety factors

MME 291: Lecture 10 Mechanical Properties of Materials 2 Prof. A.K.M.B. Rashid Department of MME BUET, Dhaka Today s Topics Plastic stress- behaviour of metals Energy of mechanical ldeformation Hardness

### Chapter 6: Mechanical Properties

Chapter 6: Mechanical Properties ISSUES TO ADDRESS... Stress and strain: What are they and why are they used instead of load and deformation? Elastic behavior: When loads are small, how much deformation

### Issues to address. Why Mechanical Test?? Mechanical Properties. Why mechanical properties?

Mechanical Properties Why mechanical properties? Folsom Dam Gate Failure, July 1995 Need to design materials that can withstand applied load e.g. materials used in building bridges that can hold up automobiles,

### MATERIALS: Clarifications and More on Stress Strain Curves

A 3.0 m length of steel rod is going to be used in the construction of a bridge. The tension in the rod will be 10 kn and the rod must extend by no more than 1.0mm. Calculate the minimum cross-sectional

### a. 50% fine pearlite, 12.5% bainite, 37.5% martensite. 590 C for 5 seconds, 350 C for 50 seconds, cool to room temperature.

Final Exam Wednesday, March 21, noon to 3:00 pm (160 points total) 1. TTT Diagrams A U.S. steel producer has four quench baths, used to quench plates of eutectoid steel to 700 C, 590 C, 350 C, and 22 C

### Concepts of stress and strain

Chapter 6: Mechanical properties of metals Outline Introduction Concepts of stress and strain Elastic deformation Stress-strain behavior Elastic properties of materials Plastic deformation Yield and yield

### Welcome to ENR116 Engineering Materials. This lecture summary is part of module 2, Material Properties.

Welcome to ENR116 Engineering Materials. This lecture summary is part of module 2, Material Properties. 1 2 Mechanical properties. 3 The intended learning outcomes from this lecture summary are that you

### 3. MECHANICAL PROPERTIES OF STRUCTURAL MATERIALS

3. MECHANICAL PROPERTIES OF STRUCTURAL MATERIALS Igor Kokcharov 3.1 TENSION TEST The tension test is the most widely used mechanical test. Principal mechanical properties are obtained from the test. There

### Mechanical Characterisation of Materials

Department of Materials and Metallurgical Engineering Bangladesh University of Engineering and Technology, Dhaka MME298 Structure and Properties of Biomaterials Sessional 1.50 Credits 3.00 Hours/Week July

### Formability R. Chandramouli Associate Dean-Research SASTRA University, Thanjavur

Formability R. Chandramouli Associate Dean-Research SASTRA University, Thanjavur-613 401 Joint Initiative of IITs and IISc Funded by MHRD Page 1 of 8 Table of Contents 1.Formability... 3 1.1 Introduction:...

### CHAPTER 6: MECHANICAL PROPERTIES ISSUES TO ADDRESS...

CHAPTER 6: MECHANICAL PROPERTIES ISSUES TO ADDRESS... Stress and strain: What are they and why are they used instead of load and deformation? Elastic behavior: When loads are small, how much deformation

### THE MECHANICAL PROPERTIES OF STAINLESS STEEL

THE MECHANICAL PROPERTIES OF STAINLESS STEEL Stainless steel is primarily utilised on account of its corrosion resistance. However, the scope of excellent mechanical properties the within the family of

### P A (1.1) load or stress. elongation or strain

load or stress MEEN 3145 TENSION TEST - BACKGROUND The tension test is the most important and commonly used test in characterizing properties of engineering materials. This test gives information essential

### بسم الله الرحمن الرحیم. Materials Science. Chapter 7 Mechanical Properties

بسم الله الرحمن الرحیم Materials Science Chapter 7 Mechanical Properties 1 Mechanical Properties Can be characterized using some quantities: 1. Strength, resistance of materials to (elastic+plastic) deformation;

### PLASTIC DEFORMATION AND THE ONSET OF TENSILE INSTABILITY

PLASTIC DEFORMATION AND THE ONSET OF TENSILE INSTABILITY Introduction In this experiment the plastic deformation behavior and the onset of plastic instability of some common structural alloys is investigated.

### MATERIALS SCIENCE-44 Which point on the stress-strain curve shown gives the ultimate stress?

MATERIALS SCIENCE 43 Which of the following statements is FALSE? (A) The surface energy of a liquid tends toward a minimum. (B) The surface energy is the work required to create a unit area of additional

### When an axial load is applied to a bar, normal stresses are produced on a cross section perpendicular to the axis of the bar.

11.1 AXIAL STRAIN When an axial load is applied to a bar, normal stresses are produced on a cross section perpendicular to the axis of the bar. In addition, the bar increases in length, as shown: 11.1

### Chapter 6: Mechanical Properties

ISSUES TO ADDRESS... Stress and strain Elastic behavior: When loads are small, how much reversible deformation occurs? What material resist reversible deformation better? Plastic behavior: At what point

### Plastic stress-strain behaviour of metals Energy of mechanical ldeformation Hardness testing Design/safety factors

Mechanical Properties of Materials 2 Prof. A.K.M.B. Rashid Department of MME BUET, Dhaka Plastic stress-strain behaviour of metals Energy of mechanical ldeformation Hardness testing Design/safety factors

### Workshop Practice TA 102

Workshop Practice TA 102 Lec 2 & 3 :Engineering Materials By Prof.A.Chandrashekhar Engineering Materials Materials play an important role in the construction and manufacturing of equipment/tools. Right

### Introduction to Engineering Materials ENGR2000 Chapter 7: Dislocations and Strengthening Mechanisms. Dr. Coates

Introduction to Engineering Materials ENGR2000 Chapter 7: Dislocations and Strengthening Mechanisms Dr. Coates An edge dislocation moves in response to an applied shear stress dislocation motion 7.1 Introduction

### ME 254 MATERIALS ENGINEERING 1 st Semester 1431/ rd Mid-Term Exam (1 hr)

1 st Semester 1431/1432 3 rd Mid-Term Exam (1 hr) Question 1 a) Answer the following: 1. Do all metals have the same slip system? Why or why not? 2. For each of edge, screw and mixed dislocations, cite

### Chapter 6: Mechanical Properties

Chapter 6: Mechanical Properties Elastic behavior: When loads are small, how much deformation occurs? What materials deform least? Stress and strain: What are they and why are they used instead of load

### Chapter 6: Mechanical Properties

Chapter 6: Mechanical Properties ISSUES TO ADDRESS... Stress and strain: What are they and why are they used instead of load and deformation? Elastic behavior: When loads are small, how much deformation

### Quiz 1 - Mechanical Properties and Testing Chapters 6 and 8 Callister

Quiz 1 - Mechanical Properties and Testing Chapters 6 and 8 Callister You need to be able to: Name the properties determined in a tensile test including UTS,.2% offset yield strength, Elastic Modulus,

### Metals are generally ductile because the structure consists of close-packed layers of

Chapter 10 Why are metals ductile and ceramics brittle? Metals are generally ductile because the structure consists of close-packed layers of atoms that allow for low energy dislocation movement. Slip

### Chapter 7. Mechanical Properties

Chapter 7 Mechanical Properties Chapter 7 Plastic Deformation, Ductility and Toughness Issues to address Stress and strain: What are they and why are they used instead of load and deformation? Elastic

### Properties in Shear. Figure 7c. Figure 7b. Figure 7a

Properties in Shear Shear stress plays important role in failure of ductile materials as they resist to normal stress by undergoing large plastic deformations, but actually fail by rupturing under shear

### The Mechanical Properties of Polymers

The Mechanical Properties of Polymers Date: 14/07/2018 Abu Zafar Al Munsur Behavior Of Material Under Mechanical Loads = Mechanical Properties. Term to address here Stress and strain: These are size-independent

### CHAPTER 6: Mechanical properties

CHAPTER 6: Mechanical properties ISSUES TO ADDRESS... Stress and strain: What are they and why are they used instead of load and deformation? Elastic behavior: When loads are small, how much deformation

### AERO 214. Introduction to Aerospace Mechanics of Materials. Lecture 2

AERO 214 Introduction to Aerospace Mechanics of Materials Lecture 2 Materials for Aerospace Structures Aluminum Titanium Composites: Ceramic Fiber-Reinforced Polymer Matrix Composites High Temperature

### Chapter 8 Strain Hardening and Annealing

Chapter 8 Strain Hardening and Annealing This is a further application of our knowledge of plastic deformation and is an introduction to heat treatment. Part of this lecture is covered by Chapter 4 of

### Extrusion of complex shapes

Extrusion of complex shapes 1 Hot extrusion Hot extrusion is the process of forcing a heated billet to flow through a shaped die opening It is used to produce long, strait metal products of constant cross

### REVISED PAGES IMPORTANT TERMS AND CONCEPTS REFERENCES QUESTIONS AND PROBLEMS. 166 Chapter 6 / Mechanical Properties of Metals

1496T_c06_131-173 11/16/05 17:06 Page 166 166 Chapter 6 / Mechanical Properties of Metals IMPORTANT TERMS AND CONCEPTS Anelasticity Design stress Ductility Elastic deformation Elastic recovery Engineering

### ENGINEERING MATERIAL 100

Department of Applied Chemistry Division of Science and Engineering SCHOOL OF ENGINEERING ENGINEERING MATERIAL 100 Experiments 4 and 6 Mechanical Testing and Applications of Non-Metals Name: Yasmin Ousam

### Mechanical Properties of Metals. Goals of this unit

Mechanical Properties of Metals Instructor: Joshua U. Otaigbe Iowa State University Goals of this unit Quick survey of important metal systems Detailed coverage of basic mechanical properties, especially

### Reproducible evaluation of material properties. Static Testing Material response to constant loading

Material Testing Material Testing Reproducible evaluation of material properties Static Testing Material response to constant loading Dynamic Testing Material response to varying loading conditions, including

### Tutorial 2 : Crystalline Solid, Solidification, Crystal Defect and Diffusion

Tutorial 1 : Introduction and Atomic Bonding 1. Explain the difference between ionic and metallic bonding between atoms in engineering materials. 2. Show that the atomic packing factor for Face Centred

### Mechanical Properties of Materials

INTRODUCTION Mechanical Properties of Materials Many materials, when in service, are subjected to forces or loads, it is necessary to know the characteristics of the material and to design the member from

### MECHANICAL PROPERTIES OF MATERIALS. Manufacturing materials, IE251 Dr M. Eissa

MECHANICAL PROPERTIES OF MATERIALS, IE251 Dr M. Eissa MECHANICAL PROPERTIES OF MATERIALS 1. Bending Test (Slide 3) 2. Shear Test (Slide 8) 3. Hardness (Slide 14) 4. Effect of Temperature on Properties

### Engineering materials

1 Engineering materials Lecture 2 Imperfections and defects Response of materials to stress 2 Crystalline Imperfections (4.4) No crystal is perfect. Imperfections affect mechanical properties, chemical

### MECHANICAL PROPERTIES

MECHANICAL PROPERTIES Mechanical Properties: In the course of operation or use, all the articles and structures are subjected to the action of external forces, which create stresses that inevitably cause

### 1) Fracture, ductile and brittle fracture 2) Fracture mechanics

Module-08 Failure 1) Fracture, ductile and brittle fracture 2) Fracture mechanics Contents 3) Impact fracture, ductile-to-brittle transition 4) Fatigue, crack initiation and propagation, crack propagation

Chapter 1 STRESS ND STRIN XIL LDING 1.1 INTRDUCTIN The purpose to study the mechanics of materials is to acquire analytical tools necessary for analysis and design of load taking members of practical utility

### Lab Exercise #2: Tension Testing (Uniaxial Stress)

Lab Exercise #2: (Uniaxial Stress) Learning Outcomes: 1. Understand the basic concepts of stress and strain 2. Identify the engineering material properties 3. Connect stress and strain through Hooke s

### 1.7 Prestressing Steel

1.7 Prestressing Steel This section covers the following topics. Forms of Prestressing Steel Types of Prestressing Steel Properties of Prestressing Steel Codal Provisions of Steel 1.7.1 Forms of Prestressing

### Chapter 6:Mechanical Properties

Chapter 6:Mechanical Properties Why mechanical properties? Need to design materials that can withstand applied load e.g. materials used in building bridges that can hold up automobiles, pedestrians materials

### Correlation between Engineering Stress-Strain and True Stress-Strain Curve

American Journal of Civil Engineering and Architecture, 2014, Vol. 2, No. 1, 53-59 Available online at http://pubs.sciepub.com/ajcea/2/1/6 Science and Education ublishing DOI:10.12691/ajcea-2-1-6 Correlation

Chapter 7: Mechanical Properties School of Mechanical Engineering Choi, Hae-Jin Materials Science - Prof. Choi, Hae-Jin Chapter 7-1 ISSUES TO ADDRESS... Stress and strain: What are they and why are they

### ENGR 151: Materials of Engineering LECTURE #12-13: DISLOCATIONS AND STRENGTHENING MECHANISMS

ENGR 151: Materials of Engineering LECTURE #12-13: DISLOCATIONS AND STRENGTHENING MECHANISMS RECOVERY, RECRYSTALLIZATION, AND GRAIN GROWTH Plastically deforming metal at low temperatures affects physical

### 21 Fracture and Fatigue Revision

21 Fracture and Fatigue Revision EG2101 / EG2401 March 2015 Dr Rob Thornton Lecturer in Mechanics of Materials www.le.ac.uk Fracture concepts Fracture: Initiation and propagation of cracks within a material

### Materials and their structures

Materials and their structures 2.1 Introduction: The ability of materials to undergo forming by different techniques is dependent on their structure and properties. Behavior of materials depends on their

### Sheet Metal: High ratio of surface area to thickness Thickness < 6mm Sheet Thickness > 6mm plate

Sheet Metal: High ratio of surface area to thickness Thickness < 6mm Sheet Thickness > 6mm plate Sheet metal forming is a process that materials undergo permanent deformation by cold forming to produce

### Chapter 12. Plastic Deformation Behavior and Models for Material

Chapter 12. Plastic Deformation Behavior and Models for Material System Health & Risk Management 1/ 20 Contents 12.1 Introduction 12.2 Stress Strain Curves 12.3 Three Dimensional Stress Strain Relationships

### Chapter 6 Mechanical Properties

Engineering Materials MECH 390 Tutorial 2 Chapter 6 Mechanical Properties Chapter 3-1 6.14:A cylindrical specimen of steel having a diameter of 15.2 mm and length of 250 mm is deformed elastically in tension