Rothbart Ch06 Qxd 2 24 06 10 35 Am Page 6 1 Chapter 6-Books Pdf

Rothbart CH06 qxd 2 24 06 10 35 AM Page 6 1 CHAPTER 6
18 Oct 2020 | 1 views | 0 downloads | 48 Pages | 1.03 MB

Share Pdf : Rothbart Ch06 Qxd 2 24 06 10 35 Am Page 6 1 Chapter 6

Download and Preview : Rothbart Ch06 Qxd 2 24 06 10 35 Am Page 6 1 Chapter 6

Report CopyRight/DMCA Form For : Rothbart Ch06 Qxd 2 24 06 10 35 Am Page 6 1 Chapter 6



Transcription

Rothbart CH06 qxd 2 24 06 10 35 AM Page 6 2, PROPERTIES OF ENGINEERING MATERIALS. 6 2 MECHANICAL DESIGN FUNDAMENTALS, It is good design practice to analyze the conditions under which test data were. obtained and to use the data most pertinent to anticipated service conditions. The challenge that an advancing technology imposes on the engineer in specify. ing treatments to meet stringent material requirements implies a need for a basic. approach which relates properties to structure in metals As a consequence of the. mechanical thermal and metallurgical treatments of metals it is advantageous to. explore for example the nature of induced internal stresses as well as the processes. of stress relief Better material performance may ensue when particular treatments. can be specified to alter the structure in metals so that the likelihood of premature. failure in service is lessened Some of the following concepts are both basic and. 1 Lattice structure of metals imperfections anisotropy and deformation mechanisms. 2 Phase relations in alloys equilibrium diagrams, 3 Kinetic reactions in the solid state heat treatment by nucleation and by diffusion. less processes precipitation hardening diffusion and oxidation. 4 Surface treatments chemical and structural changes in carburizing nitriding and. localized heating, 5 Metallurgical bonds welded and brazed joints. 6 2 STRENGTH PROPERTIES TENSILE TEST, AT ROOM TEMPERATURE.
The yield strength determined by a specified offset 0 2 percent strain from a stress. strain diagram is an important and widely used property for the design of statically. loaded members exhibiting elastic behavior This property is derived from a test in. which the following conditions are normally controlled surface condition of standard. specimen is specified load is axial the strain rate is low i e about 10 3 in in s and. grain size is known Appropriate safety factors are applied to the yield strength to allow. for uncertainties in the calculated stress and stress concentration factors and for possible. overloads in service Since relatively small safety factors are used in critically stressed. aircraft materials a proof stress at 0 01 percent strain offset is used because this more. nearly approaches the proportional limit for elastic behavior in the material A typical. stress strain plot from a tensile test is shown in Fig 6 1 indicating the elastic and plastic. behaviors In order to effect more meaningful comparisons in design strength properties. among materials having different specific gravities the strength property can be divided. by the specific gravity giving units of psi per pound per cubic inch. The modulus of elasticity is a measure of the stiffness or rigidity in a material. Values of the modulus normally are not exactly determined quantities and typical val. ues are commonly reported for a given material When a material is selected on the. basis of a high modulus the tendency toward whip and vibration in shaft or rod appli. cations is reduced These effects can lead to uneven wear Furthermore the modulus. assumes particular importance in the design of springs and diaphragms which neces. sitate a definite degree of motion for a definite load In this connection selection of a. high modulus material can lead to a thinner cross section. The ultimate tensile strength and the ductility percent elongation in inches per inch. or percent reduction in area at fracture are other properties frequently reported from. tensile tests These serve as qualitative measures reflecting the ability of a material in. deforming plastically after being stressed beyond the elastic region The strength prop. erties and ductility of a material subjected to different treatments can vary widely. This is illustrated in Fig 6 2 When the yield strength is raised by treatment to a high. Downloaded from Digital Engineering Library McGraw Hill www digitalengineeringlibrary com. Copyright 2006 The McGraw Hill Companies All rights reserved. Any use is subject to the Terms of Use as given at the website. Rothbart CH06 qxd 2 24 06 10 35 AM Page 6 3, PROPERTIES OF ENGINEERING MATERIALS. PROPERTIES OF ENGINEERING MATERIALS 6 3, FIG 6 1 Portions of tensile stress strain. curves in metals 1 a Elastic behavior b Elastic, and plastic behaviors. FIG 6 2 The effects of treatments on tensile characteristics of a metal 1 a Perfectly. brittle embrittled all elastic behavior b Low ductility hardened elastic plus. plastic behaviors c Ductile softened elastic plus much plastic behaviors. value i e greater than two thirds of the tensile strength special concern should be. given to the likelihood of tensile failures by small overloads in service Members sub. jected solely to compressive stress may be made from high yield strength materials. which result in weight reduction, When failures are examined in statically loaded tensile specimens of circular section. they can exhibit a cup and cone fracture characteristic of a ductile material or on the. other extreme a brittle fracture in which little or no necking down is apparent Upon load. ing the specimen to the plastic region axial tangential and radial stresses are induced In. a ductile material the initial crack forms in, the center where the triaxial stresses.
become equally large while at the surface, the radial component is small and the. deformation is principally by biaxial shear, On the other hand an embrittled material. exhibits no such tendency for shear and the, fracture is normal to the loading axis. Some types of failures in round tensile, specimens are shown in Fig 6 3. The properties of some wrought met, als presented in Table 6 1 serve to show.
the significant differences relating to, FIG 6 3 Typical tensile test fractures 1 a Initial. crack formation b Ductile material c Brittle, alloy content and treatment Section 6 17. material gives more information, Downloaded from Digital Engineering Library McGraw Hill www digitalengineeringlibrary com. Copyright 2006 The McGraw Hill Companies All rights reserved. Any use is subject to the Terms of Use as given at the website. Rothbart CH06 qxd 2 24 06 10 35 AM Page 6 4, PROPERTIES OF ENGINEERING MATERIALS. 6 4 MECHANICAL DESIGN FUNDAMENTALS, TABLE 6 1 Room Temperature Tensile Properties for Some Wrought Metals.
The tensile properties of metals are dependent upon the rate of straining as shown for. aluminum and copper in Fig 6 4 and are significantly affected by the temperature as. shown in Fig 6 5 For high temperature applications it is important to base design on dif. ferent criteria notably the stress rupture and creep characteristics in metals both of which. are also time dependent phenomena The use of metals at low temperatures requires a con. sideration of the possibility of brittleness which can be measured in the impact test. FIG 6 4 Effects of strain rates and temperatures on tensile strength properties of copper and. aluminum 1 a Copper b Aluminum, FIG 6 5 Effects of temperatures on tensile proper. ties u ultimate tensile strength y yield strength, Downloaded from Digital Engineering Library McGraw Hill www digitalengineeringlibrary com. Copyright 2006 The McGraw Hill Companies All rights reserved. Any use is subject to the Terms of Use as given at the website. Rothbart CH06 qxd 2 24 06 10 35 AM Page 6 5, PROPERTIES OF ENGINEERING MATERIALS. PROPERTIES OF ENGINEERING MATERIALS 6 5, 6 3 ATOMIC ARRANGEMENTS IN PURE METALS. CRYSTALLINITY, The basic structure of materials provides information upon which properties and.
behavior of metals may be generalized so that selection can be based on fundamental. considerations A regular and periodic array of atoms in common metals whose. atomic diameters are about one hundred millionth of an inch in space in which a unit. cell is the basic structure is a fundamental characteristic of crystalline solids Studies. of these structures in metals lead to some important considerations of the behaviors in. response to externally applied forces temperature changes as well as applied electri. cal and magnetic fields, The body centered cubic bcc cell shown in Fig 6 6a is the atomic arrangement. characteristic of Fe W Mo Ta Ti V and Nb It is among this class of metals that. transitions from ductile to brittle behavior as a function of temperature are significant. to investigate This structure represents an atomic packing density where about 66 per. cent of the volume is populated by atoms while the remainder is free space The ele. ments Al Cu Fe Ni Pb Ag Au and Pt have a closer packing of atoms in space. constituting a face centered cubic fcc cell shown in Fig 6 6b Characteristic of these. are ductility properties which in many cases extend to very low temperatures Another. structure common to Mg Cd Zn Ti and Be is the hexagonal close packed hcp. cell in Fig 6 6c These metals are somewhat more difficult to deform plastically than. the materials in the two other structures cited above. FIG 6 6 Cell structure a Body centered cubic bcc unit cell structure b Face centered cubic. fcc unit cell structure c Hexagonal close packed hcp unit cell structure. It is apparent from the atomic arrays represented in these structures that the clos. est approach of atoms can vary markedly in different crystallographic directions. Properties in materials are anisotropic when they show significant variations in differ. ent directions Such tendencies are dependent on the particular structure and can be. especially pronounced in single crystals one orientation of the lattices in space. Some examples of these are given in Table 6 2 When materials are processed so that. Downloaded from Digital Engineering Library McGraw Hill www digitalengineeringlibrary com. Copyright 2006 The McGraw Hill Companies All rights reserved. Any use is subject to the Terms of Use as given at the website. Rothbart CH06 qxd 2 24 06 10 35 AM Page 6 6, PROPERTIES OF ENGINEERING MATERIALS. 6 6 MECHANICAL DESIGN FUNDAMENTALS, TABLE 6 2 Examples of Anisotropic Properties in Single Crystals. Property Material and structure Properties relation. Elastic module E in tension Fe bcc E AB 2 2E AC, Elastic module G in shear Ag fcc G OC 2 3G OK. Magnetization Fe bcc Ease of magnetization, Thermal expansion coefficient Zn hcp OZ 4 OA.
their final grain size is large each grain represents one orientation of the lattices or. that the grains are preferentially oriented as in extrusions drawn wire rolled sheet. sometimes in forgings and castings special evaluation of anisotropy should be made. In the event that directional properties influence design considerations particular. attention must be given to metallurgical treatments which may control the degree of. anisotropy The magnetic anisotropy in a single crystal of iron is shown in Fig 6 7. FIG 6 7 Magnetic anisotropy in a single crystal of iron2 I B H 4. where I intensity of magnetization B magnetic induction gauss H. field strength oersteds, 6 4 PLASTIC DEFORMATION OF METALS. When metals are externally loaded past the elastic limit so that permanent changes in. shape occur it is important to consider the induced internal stresses property changes. and the mechanisms of plastic deformation These are matters of practical considera. tion in the following materials that are to be strengthened by cold work machining of. cold worked metals flow of metals in deep drawing and impact extrusion operations. forgings where the grain flow patterns may affect the internal soundness localized. surface deformation to enhance fatigue properties and cold working of some magnetic. materials Experimental studies provide the key by which important phenomena are. revealed as a result of the plastic deformation process These studies indicate some. treatments that may be employed to minimize unfavorable internal stress distributions. and undesirable grain orientation distributions, Plastic deformation in metals occurs by a glide or slip process along densely. packed planes fixed by the particular lattice structure in a metal Therefore an applied. Downloaded from Digital Engineering Library McGraw Hill www digitalengineeringlibrary com. Copyright 2006 The McGraw Hill Companies All rights reserved. Any use is subject to the Terms of Use as given at the website. Rothbart CH06 qxd 2 24 06 10 35 AM Page 6 7, PROPERTIES OF ENGINEERING MATERIALS. PROPERTIES OF ENGINEERING MATERIALS 6 7, FIG 6 8 Slip deformation in single crystals a Resolved shear stress P A0 cos cos. ABCD is plane of slip OZ is slip direction b Sketch of single crystal after yielding. load is resolved as a shear stress on those particular glide elements planes and direc. tions requiring the least amount of deformation work on the system An example of. this deformation process is shown in Fig 6 8 Face centered cubic fcc structured. metals such as Cu Al and Ni are more ductile than the hexagonal structured metals. such as Mg Cd and Zn at room temperature because in the fcc structure there are. four times as many possible slip systems as in a hexagonal structure Slip is initiated. at much lower stresses in metals than theoretical calculations based on a perfect array. of atoms would indicate In real crystals there are inherent structural imperfections. termed dislocations atomic misfits as shown in Fig 6 9 which account for the. observed yielding phenomenon in metals In addition dislocations are made mobile by. mechanical and thermal excitations and they can interact to result in strain hardening. PROPERTIES OF ENGINEERING MATERIALS 6 3 FIG 6 1 Portions of tensile stress strain curves in metals 1 a Elastic behavior b Elasticand plastic behaviors FIG 6 2 The effects of treatments on tensile characteristics of a metal 1 a Perfectly brittle embrittled all elastic behavior b Low ductility hardened elastic plusplastic behaviors

Related Books

ManualonTrainingPreparation JICA

ManualonTrainingPreparation JICA

ManualonTrainingPreparation Manual on TrainingPreparation Glossary Activity Sequence Activity sequencing is to identify dependencies and logical relationships among activities Budget The budget for something is the amount of money that a person or organization has available to spend on it Budgeting Budgeting is to aggregate the estimated costs of individual activities to establish

Sample Preparation Kit Biognosys

Sample Preparation Kit Biognosys

First Edition Version 1 04 April 2017 Sample Preparation Kit Manual Biognosys AG Switzerland Page 3 of 11 Sample Preparation Kit Components

Manual for the Preparation of a Community Based Adaptation

Manual for the Preparation of a Community Based Adaptation

Manual for the Preparation of a Community Based Adaptation Plan with a focus on Water Resources Management Partners COCOF UNICOOPAGI IPFG AND MMM KIRAMBI With experiences from the Water and Climate Change Project in 9 villages of Kamonyi Nyanza and Nyamagabe Districts of the Southern Province of Rwanda Head office Maynooth Co Kildare Tel 353 0 1 629 3333 Dublin 12 Cathedral

LES COURS DE AUL RNAUD Chimie organique

LES COURS DE AUL RNAUD Chimie organique

LES COURS DE PAUL ARNAUD Chimie organique 19e dition Brigitte Jamart Professeure l ENSIC universit de Lorraine Nancy Jacques Bodiguel Ma tre de conf rences l universit de Lorraine Nancy

Synth se d un dulcorant Education gouv fr

Synth se d un dulcorant Education gouv fr

Clayden Greeves Warren et Wothers Chimie organique Drouin Introduction la chimie organique Br ckner M canismes r actionnels en chimie organique Situation d clenchante possible Le 3 amino 4 1 benzyl 2 m thoxy 2 oxo thyl amino 4 oxobutano que plus connu sous le nom aspartame est un dulcorant artificiel d couvert en 1965 Il a un pouvoir sucrant environ 200 fois

Cas cliniques Des r sum s la n des paragraphes

Cas cliniques Des r sum s la n des paragraphes

Graham Clayden MD FRCP FRCPCH is published by arrangement with Elsevier Limited ISBN 9780723435655 Cette dition d Illustrated Textbook of Paediatrics 4th par Tom Lissauer MB BChir FRCP FRCPCH and Graham Clayden MD FRCP FRCPCH est traduite et dit e en fran ais par De Boeck Sup rieur en accord avec Elsevier Limited

Greeves organique Decitre

Greeves organique Decitre

Clayden I Greeves I Warren Chimie organique Clayden I Greeves I Warren a En d but de chapitre un encadr qui trace le fil rouge de la mati re a Concepts cl s repris dans un encadr dans la marge a Des encadr s bleus avec des informations suppl mentaires sur la mati re vue a Des notices bibliographiques la fin du chapitre 9 782804174415 Conception graphique Primo amp Primo CLAYDEN

MANUAL GEARBOX VGK RACING

MANUAL GEARBOX VGK RACING

Reverse idler gear 54 Reverse fork 55 Oil seal mainshaft 56 Belville washer mainshaft end thrust 57 Ball bearing mainshaft 58 Mainshaft 59 Needle roller bearing 3rd 60 3rd gear 61 Synchro ring 3rd gear

The engine exhaust from this American Honda Motor Company

The engine exhaust from this American Honda Motor Company

The engine exhaust from this product contains chemicals known to the State of California to cause cancer birth defects or other reproductive harm Keep this Owner s Manual handy so you can refer to it at any time This Owner s Manual is considered a permanent part of the outboard motor and should remain with the outboard motor if resold The information and specifications included in

Bedienungsanleitung Grundeinstellungen Ricoh

Bedienungsanleitung Grundeinstellungen Ricoh

Bedienungsanleitung Bedienungsanleitung Grundeinstellungen Lesen Sie bitte diese Bedienungsanleitung sorgf ltig bevor Sie das Ger t benutzen und bewahren Sie die Anleitung griffbereit auf

ELECTRICAL WIRING R H DRIVE VEHICLES

ELECTRICAL WIRING R H DRIVE VEHICLES

WIRING HARNESS CONFIGURATION DIAGRAMS Connector symbol 01 thru A 50 Earth cable C 4 WIRING HARNESS CONFIGURATION DIAGRAMS ENGINE COMPARTMENT A 01 2 B Brake fluid level switch A 03 1 B Noise condenser A 04 1 Alternator A 05 4 GR Alternator A 09 1 B Starter A 10 1 Starter A 12 2 B Fuel pressure solenoid valve A 16 4 B