陶瓷材料力学性能幻灯片.ppt

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1、陶瓷材料力学性能第1页，共29页，编辑于2022年，星期三 Tensile stress,s:Shear stress,t:Stress has units:N/m2 or lb/in2ENGINEERING STRESS第2页，共29页，编辑于2022年，星期三 Elastic modulus,E E curvature at roE is larger if Eo is larger.PROPERTIES FROM BONDING:E第3页，共29页，编辑于2022年，星期三 Elastic Shear modulus,G:t=G g Elastic Bulk modulus,K:Spec

2、ial relations for isotropic materials:simpletorsiontestpressuretest:Init.vol=Vo.Vol chg.=VOTHER ELASTIC PROPERTIES第4页，共29页，编辑于2022年，星期三 Tensile strain:Lateral strain:Shear strain:qStrain is alwaysdimensionless.(L)(-LL)ENGINEERING STRAIN第5页，共29页，编辑于2022年，星期三(c)2003 Brooks/Cole,a division of Thomson L

3、earning,Inc.Thomson Learning is a trademark used herein under license.Figure 6.3 (a)Tensile,compressive,shear and bending stresses.(b)Illustration showing how Youngs modulus is defined for elastic material.(c)For nonlinear materials,we use the slope of a tangent as a variable quantity that replaces

4、the Youngs modulus constant第6页，共29页，编辑于2022年，星期三The Tensile Test:Use of the Stress-Strain DiagramoLoad-The force applied to a material during testing.oStrain gage or Extensometer-A device used for measuring change in length and hence strain.oGlass temperature(Tg)-A temperature below which an otherwi

5、se ductile material behaves as if it is brittle.oEngineering stress-The applied load,or force,divided by the original cross-sectional area of the material.oEngineering strain-The amount that a material deforms per unit length in a tensile test.第7页，共29页，编辑于2022年，星期三(c)2003 Brooks/Cole,a division of T

6、homson Learning,Inc.Thomson Learning is a trademark used herein under license.Figure 6.7 A unidirectional force is applied to a specimen in the tensile test by means of the moveable crosshead.The cross-head movement can be performed using screws or a hydraulic mechanism第8页，共29页，编辑于2022年，星期三(c)2003 B

7、rooks/Cole,a division of Thomson Learning,Inc.Thomson Learning is a trademark used herein under license.Figure 6.9 Tensile stress-strain curves for different materials.Note that these are qualitative第9页，共29页，编辑于2022年，星期三 Ductilefracture isdesirablefor structural applications!Classification:Ductile:w

8、arning before fracture,i.e.changes geometry before failureBrittle:No warningAdapted from Fig.8.1,Callister 6e.DUCTILE VS BRITTLE FAILURE第10页，共29页，编辑于2022年，星期三(c)2003 Brooks/Cole,a division of Thomson Learning,Inc.Thomson Learning is a trademark used herein under license.Figure 6.10 The stress-strain

9、 curve for an aluminum alloy第11页，共29页，编辑于2022年，星期三1.Initial2.Small load3.UnloadElastic means reversible!ELASTIC DEFORMATION第12页，共29页，编辑于2022年，星期三31.Initial2.Small load3.UnloadPlastic means permanent!PLASTIC DEFORMATION(METALS)第13页，共29页，编辑于2022年，星期三(c)2003 Brooks/Cole,a division of Thomson Learning,I

10、nc.Thomson Learning is a trademark used herein under license.Figure 6.11 (a)Determining the 0.2%offset yield strength in gray cast ion,and(b)upper and lower yield point behavior in a low-carbon steel第14页，共29页，编辑于2022年，星期三True Stress and True StrainoTrue stress The load divided by the actual cross-se

11、ctional area of the specimen at that load.oTrue strain The strain calculated using actual and not original dimensions,given by t ln(l/l0).Figure 6.17 The relation between the true stress-true strain diagram and engineering stress-engineering strain diagram.The curves are identical to the yield point

12、第15页，共29页，编辑于2022年，星期三The Bend Test for Brittle MaterialsoBend test-Application of a force to the center of a bar that is supported on each end to determine the resistance of the material to a static or slowly applied load.oFlexural strength or modulus of rupture-The stress required to fracture a sp

13、ecimen in a bend test.oFlexural modulus-The modulus of elasticity calculated from the results of a bend test,giving the slope of the stress-deflection curve.第16页，共29页，编辑于2022年，星期三Figure 6.18 The stress-strain behavior of brittle materials compared with that of more ductile materials第17页，共29页，编辑于2022

14、年，星期三Figure 6.19 (a)The bend test often used for measuring the strength of brittle materials,and(b)the deflection obtained by bending第18页，共29页，编辑于2022年，星期三Figure 6.21 (a)Three point and(b)four-point bend test setup第19页，共29页，编辑于2022年，星期三第20页，共29页，编辑于2022年，星期三Hardness of MaterialsoHardness test-Measur

15、es the resistance of a material to penetration by a sharp object.oMacrohardness-Overall bulk hardness of materials measured using loads 2 N.oMicrohardness Hardness of materials typically measured using loads less than 2 N using such test as Knoop(HK).oNano-hardness-Hardness of materials measured at

16、110 nm length scale using extremely small(100 N)forces.第21页，共29页，编辑于2022年，星期三Figure 6.23 Indentors for the Brinell and Rockwell hardness tests第22页，共29页，编辑于2022年，星期三Vickers Hardness,Hv第23页，共29页，编辑于2022年，星期三FRACTURE TOUGHNESSFracture toughness:Kc=Ysc(pa)0.5=Y(2Egs)0.5 Kc is a material propertyY 1,depe

17、nds on geometry第24页，共29页，编辑于2022年，星期三increasingBased on data in Table B5,Callister 6e.Composite reinforcement geometry is:f=fibers;sf=short fibers;w=whiskers;p=particles.Addition data as noted(vol.fraction of reinforcement):1.(55vol%)ASM Handbook,Vol.21,ASM Int.,Materials Park,OH(2001)p.606.2.(55 vo

18、l%)Courtesy J.Cornie,MMC,Inc.,Waltham,MA.3.(30 vol%)P.F.Becher et al.,Fracture Mechanics of Ceramics,Vol.7,Plenum Press(1986).pp.61-73.4.Courtesy CoorsTek,Golden,CO.5.(30 vol%)S.T.Buljan et al.,Development of Ceramic Matrix Composites for Application in Technology for Advanced Engines Program,ORNL/S

19、ub/85-22011/2,ORNL,1992.6.(20vol%)F.D.Gace et al.,Ceram.Eng.Sci.Proc.,Vol.7(1986)pp.978-82.FRACTURE TOUGHNESS第25页，共29页，编辑于2022年，星期三 Crack growth condition:Largest,most stressed cracks grow first!-Result 1:Max flaw size dictates design stress.-Result 2:Design stress dictates max.flaw size.K KcDESIGN AGAINST CRACK GROWTH第26页，共29页，编辑于2022年，星期三第27页，共29页，编辑于2022年，星期三第28页，共29页，编辑于2022年，星期三第29页，共29页，编辑于2022年，星期三