Technology & Engineering
Tensile Properties
Tensile properties refer to the mechanical characteristics of a material under tension, including its ability to withstand stretching and deformation before breaking. These properties are typically measured through tests such as tensile strength, yield strength, and elongation, providing valuable insights into the material's performance and suitability for various engineering applications. Understanding a material's tensile properties is crucial for designing and selecting appropriate materials for structural and mechanical components.
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9 Key excerpts on "Tensile Properties"
- C. Suryanarayana(Author)
- 2011(Publication Date)
- CRC Press(Publisher)
315 9 Tensile Testing 9.1 INTRODUCTION The. mechanical. properties. of. materials. are. very. important. in. determining. their. applications. .For.example,.one.may.be.interested.in.choosing.a.material.for.load-bearing. applications . . In. that. case,. a. material. with. high. strength. is. required . . Alternately,.if.one.is.interested.in.a.material.for.easy.fabrication,.then.the.material. should.have.high.ductility . .Thus,.for.different.applications,.an.engineer.will.have.to. select.a.material.with.an.appropriate.combination.of.properties . .Even.though.people. talk. of. materials. being. strong. or. weak,. a. quantitative. comparison. of. the. strength. properties.is.essential.for.an.intelligent.choice.of.suitable.material . The.strength.of.a.material.can.be.understood.as.its.resistance.to. plastic deforma-tion . .It.may.be.measured.by.applying.a.static.load.uniformly.over.a.surface.cross. section.and.monitoring.the.dimensional.changes.of.the.specimen . .The.load.may.be. applied.in.four.basically.different.ways— tension ,. compression ,. shear ,.and. torsion . . These.four.different.modes.are.schematically.shown.in.Figure.9 .1. .In.tension,.a.load. is.applied.in.such.a.way.that.the.load.pulls.the.specimen.apart.and.the.specimen. expands.in.the.direction.of.application.of.load . .In.compression,.the.load.is.applied.so. as.to.contract.the.specimen.in.the.direction.of.application.of.load . .In.shear,.the.load. is. applied. in. opposite. directions. on. two. parallel. faces. of. a. specimen . . In. torsion,. which.is.a.variation.of.pure.shear,.a.specimen.is.twisted.by.a.torque,.which.produces. a.rotational.motion.about.the.longitudinal.axis.of.one.end.of.the.specimen.relative.to. the.other . .Even.though.the.load.may.be.applied.in.many.different.ways,.it.is.the.shear. force.which.causes.plastic.deformation.in.a.material . .Consequently,.irrespective.of. the.way.in.which.the.load.is.applied,.it.is.the.shear.component.which.needs.to.be.
eBook - PDF- Timothy A. Philpot(Author)
- 2014(Publication Date)
- Wiley(Publisher)
Mechanical Properties of Materials CHAPTER 3 47 To properly design a structural or mechanical component, the engineer must understand the characteristics and work within the limitations of the material used in the component. Materials such as steel, aluminum, plastics, and wood each respond uniquely to applied loads and stresses. To determine the strength and characteristics of materials such as these requires laboratory testing. One of the simplest and most effective laboratory tests for ob- taining engineering design information about a material is called the tension test. The tension test is very simple. A specimen of the material, usually a round rod or a flat bar, is pulled with a controlled tension force. As the force is increased, the elongation of the specimen is measured and recorded. The relationship between applied load and re- sulting deformation can be observed from a plot of the data. This load-deformation plot has limited direct usefulness, however, because it applies only to the specific specimen (mean- ing the specific diameter or cross-sectional dimensions) used in the test procedure. A more useful diagram than the load-deformation plot is one showing the relationship between stress and strain, called the stress–strain diagram. The stress–strain diagram is more useful because it applies to the material in general rather than to the particular speci- men used in the test. The information obtained from the stress–strain diagram can be applied to all components, regardless of their dimensions. The load and elongation data obtained in the tension test can be readily converted to stress and strain data. 3.1 The Tension Test 48 MECHANICAL PROPERTIES OF MATERIALS Tension Test Setup To conduct the tension test, the test specimen is inserted into grips that hold the specimen securely while tension force is applied by the testing machine (Figure 3.1).
eBook - PDFFundamentals of Materials Science and Engineering
An Integrated Approach
- William D. Callister, Jr., David G. Rethwisch(Authors)
- 2022(Publication Date)
- Wiley(Publisher)
The mechanical behavior of a material reflects its response or deformation in relation to an applied load or force. Key mechanical design properties are stiffness, strength, hardness, ductility, and toughness. The mechanical properties of materials are ascertained by performing carefully de- signed laboratory experiments that replicate as nearly as possible the service conditions. Factors to be considered include the nature of the applied load and its duration, as well as the environmental conditions. It is possible for the load to be tensile, compressive, or shear, and its magnitude may be constant with time or may fluctuate continuously. Application time may be only a fraction of a second, or it may extend over a period of many years. Service temperature may be an important factor. 8.1 | | INTRODUCTION WHY STUDY Mechanical Properties? It is incumbent on engineers to understand how the various mechanical properties are measured and what these properties represent; they may be called upon to design structures/components using predetermined materials such that unac- ceptable levels of deformation and/or failure will not occur. In Design Examples 8.1 and 8.2, we present two typical types of design protocols; these examples demonstrate, respectively, a procedure used to design a tensile-testing ap- paratus and how material requirements may be determined for a pressurized cylindrical tube. LEARNING OBJECTIVES After studying this chapter, you should be able to do the following: 1. Define engineering stress and engineering strain. 2. State Hooke’s law and note the conditions under which it is valid. 3. Define Poisson’s ratio. 4. Given an engineering stress–strain diagram, determine (a) the modulus of elasticity, (b) the yield strength (0.002 strain offset), and (c) the tensile strength and (d) estimate the percentage elongation. 5. For the tensile deformation of a ductile cylin- drical metal specimen, describe changes in specimen profile to the point of fracture.
eBook - PDF- Nelson Bolívar(Author)
- 2020(Publication Date)
- Arcler Press(Publisher)
Mechanical Properties and Performance of Materials 7 CONTENTS 7.1. Introduction .................................................................................... 170 7.2. Mechanical Behavior ...................................................................... 170 7.3. Stress And Strain ............................................................................. 171 7.4. Fundamentals Definitions In The Mechanics Of Materials ............... 175 7.5. Tensile Properties ............................................................................ 177 7.6. Compressive, Bearing, And Shear Properties ................................... 181 7.7. Measures Of Ductility ..................................................................... 186 7.8. Creep And The Stress Rupture Properties ......................................... 187 7.9. Toughness ....................................................................................... 189 7.10. Plastic/Elastic Deformation ........................................................... 200 7.11. Fatigue .......................................................................................... 201 References ............................................................................................. 206 Chapter General Physics 170 7.1. INTRODUCTION Samples of the engineering materials are exposed to a broad variety of mechanical tests to measure their elastic constants, strength, and other material properties along with their performance under the variety of actual utilization conditions and environments (Curtis and Clark, 1990; Oka and Yoshida, 2005). The outcomes of these tests are used for two main purposes: 1) engineering design and 2) the quality control either by materials producer to validate the procedure or by the end-user to endorse the material specifications (Kolsky, 1949; Murayama, 1978).
- Donald Askeland, Wendelin Wright, Donald Askeland(Authors)
- 2020(Publication Date)
- Cengage Learning EMEA(Publisher)
The mechanical properties of materials must also be understood so that we can process materials into useful shapes using deformation processing techniques. Deformation processing requires a detailed understanding of the mechanical properties of materials at different temperatures and conditions of loading. We must also under- stand how materials processing may change materials properties, e.g., by making a metal stronger or weaker than it was prior to processing. In the sections that follow, we define terms that are used to describe the mechanical properties of engineered materials. Different tests used to determine mechanical properties of materials are discussed. 6-2 Terminology for Mechanical Properties There are different types of forces or “stresses” that are encountered in dealing with mechanical properties of materials. In general, we define stress as the force acting per unit area over which the force is applied. Tensile, compressive, and shear stresses are illus- trated in Figure 6-1(a). Strain is defined as the change in dimension per unit length. Stress is typically expressed in psi (pounds per square inch) or Pa (pascals, newtons per square meter). Strain has no dimensions and is often expressed as in./in. or cm/cm. Tensile and compressive stresses are normal stresses. A normal stress arises when the applied force acts perpendicular to the area of interest. Tension causes elongation in the direction of the applied force, whereas compression causes shortening. A shear stress arises when the applied force acts in a direction parallel to the area of interest. Many load-bearing applications involve tensile or compressive stresses. Shear stresses are often encountered in the processing of materials using such techniques as polymer extrusion. Shear stresses are also found in structural applications. Note that even a simple tensile stress applied along one direction will cause a shear stress in other directions (e.g., see Schmid’s law, Chapter 4).
- Donald Askeland, Wendelin Wright(Authors)
- 2018(Publication Date)
- Cengage Learning EMEA(Publisher)
The mechanical properties of materials must also be understood so that we can process materials into useful shapes using deformation processing techniques. Deformation processing requires a detailed understanding of the mechanical properties of materials at different temperatures and conditions of loading. We must also under-stand how materials processing may change materials properties, e.g., by making a metal stronger or weaker than it was prior to processing. In the sections that follow, we define terms that are used to describe the mechanical properties of engineered materials. Different tests used to determine mechanical properties of materials are discussed. 6-2 Terminology for Mechanical Properties There are different types of forces or “stresses” that are encountered in dealing with mechanical properties of materials. In general, we define stress as the force acting per unit area over which the force is applied. Tensile, compressive, and shear stresses are illus-trated in Figure 6-1(a). Strain is defined as the change in dimension per unit length. Stress is typically expressed in psi (pounds per square inch) or Pa (pascals, newtons per square meter). Strain has no dimensions and is often expressed as in./in. or cm/cm. Tensile and compressive stresses are normal stresses. A normal stress arises when the applied force acts perpendicular to the area of interest. Tension causes elongation in the direction of the applied force, whereas compression causes shortening. A shear stress arises when the applied force acts in a direction parallel to the area of interest. Many load-bearing applications involve tensile or compressive stresses. Shear stresses are often encountered in the processing of materials using such techniques as polymer extrusion. Shear stresses are also found in structural applications. Note that even a simple tensile stress applied along one direction will cause a shear stress in other directions (e.g., see Schmid’s law, Chapter 4).
eBook - PDFFundamentals of Modern Manufacturing
Materials, Processes, and Systems
- Mikell P. Groover(Author)
- 2016(Publication Date)
- Wiley(Publisher)
[18] www.tedpella.com/company_html/hardness.htm. 64 | Chapter 3 | Mechanical Properties of Materials R E V I E W Q U E S T I O N S 3.1 What are the three types of static stresses to which materi- als are subjected? 3.2 State Hooke’s law. 3.3 What is the difference between engineering stress and true stress in a tensile test? 3.4 Define tensile strength of a material. 3.5 Define yield strength of a material. 3.6 Why can a direct conversion not be made between the duc- tility measures of elongation and reduction in area using the assumption of constant volume? 3.7 What is work hardening? 3.8 Under what circumstances does the strength coefficient have the same value as the yield strength? 3.9 How does the change in cross-sectional area of a test spec- imen in a compression test differ from its counterpart in a tensile test specimen? 3.10 What is the complicating factor that occurs in a compres- sion test that might be considered analogous to necking in a tensile test? 3.11 Tensile testing is not appropriate for hard brittle materials such as ceramics. What is the test commonly used to deter- mine the strength properties of such materials? 3.12 How is the shear modulus of elasticity G related to the tensile modulus of elasticity E, on average? 3.13 How is shear strength S related to tensile strength TS, on average? 3.14 What is hardness, and how is it generally tested? 3.15 Why are different hardness tests and scales required? 3.16 Define the recrystallization temperature for a metal. 3.17 Define viscosity of a fluid. 3.18 What is the defining characteristic of a Newtonian fluid? 3.19 What is viscoelasticity, as a material property? P R O B L E M S Answers to problems labeled (A) are listed in an Appendix at the back of the book. Strength and Ductility in Tension 3.1 (A) (SI Units) A tensile test specimen has a gage length = 50 mm and its cross-sectional area = 100 mm 2 . The speci- men yields at 48,000 N, and the corresponding gage length = 50.23 mm.
- James C. Gerdeen PhD PE, Ronald A.L. Rorrer PhD PE(Authors)
- 2011(Publication Date)
- CRC Press(Publisher)
27 2 Mechanical Properties of Polymers 2.1 INTRODUCTION In the previous chapter, it was pointed out how the chemical structure of polymers influences their mechanical properties. The glass transition temperature and the rate of cooling from the melt determine whether the polymer will be a hard, stiff material, or a soft flexible material. These qualitative differences can be quantified by measuring standard mechanical properties. The student, generally, is introduced to the subject of mechanical behavior through the study of linear elastic metals that exhibit solid behavior at normal operating temperatures and conditions. However, this study of polymers reveals that polymers exhibit fluid as well as solid behavior and are visco-elastic and viscoplastic at room temperature. The mechanical properties of polymers are strain rate sensitive and highly temperature dependent. 2.2 Tensile Properties The standard tensile test, 1 is conducted on a uniaxial specimen with a reduced cross section. Standard tensile specimens have an overall length of 8 in. with a 2 in. gage length and cross section of 0.500 in. width and thickness t . Smaller specimens of one-half standard size are sometimes used for polymers. An extensometer is mounted on the central portion of the specimen to measure the elongation over the 2-in. gage length, and the conventional engineering strain is calculated from ε = δ = L L L L L o o o ( ) , -(2.1) where L o is the gage length and L is the length for any axial load P applied to the specimen. Equation 2.1 is satisfactory for small strains in relatively stiff materials. However, for large strains the true strain definition is recommended, where ε δ T o d ln 1 = = + L L L L ∫ . (2.2) The conventional engineering tensile stress in the specimen is calculated from σ = P A o (2.3) when strains are small. A o is the original cross-sectional area. When strains are large, the true stress definition is recommended, where
eBook - PDFFundamentals of Materials Science and Engineering
An Integrated Approach
- William D. Callister, Jr., David G. Rethwisch(Authors)
- 2016(Publication Date)
- Wiley(Publisher)
• For an isotropic material, shear and elastic moduli and Poisson’s ratio are related according to Equation 7.9. • The phenomenon of yielding occurs at the onset of plastic or permanent deformation. • Yield strength is indicative of the stress at which plastic deformation begins. For most materials, yield strength is determined from a stress–strain plot using the 0.002 strain offset technique. • Tensile strength is taken as the stress level at the maximum point on the engineering stress–strain curve; it represents the maximum tensile stress that can be sustained by a specimen. • For most metallic materials, at the maxima on their stress–strain curves, a small constriction or “neck” begins to form at some point on the deforming specimen. All subsequent deformation ensues by the narrowing of this neck region, at which point fracture ultimately occurs. • Ductility is a measure of the degree to which a material plastically deforms by the time fracture occurs. • Quantitatively, ductility is measured in terms of percents elongation and reduction in area. Percent elongation (%EL) is a measure of the plastic strain at fracture (Equation 7.11). Percent reduction in area (%RA) may be calculated according to Equation 7.12. Concepts of Stress and Strain Stress–Strain Behavior Elastic Properties of Materials Tensile Properties (Metals) Introduction 264 • Chapter 7 / Mechanical Properties • Yield and tensile strengths and ductility are sensitive to any prior deformation, the presence of impurities, and/or any heat treatment. Modulus of elasticity is relatively insensitive to these conditions. • With increasing temperature, values of elastic modulus and tensile and yield strengths decrease, whereas the ductility increases. • Modulus of resilience is the strain energy per unit volume of material required to stress a material to the point of yielding—or the area under the elastic portion of the engineering stress–strain curve.
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