ENGR-45_Lec-14_Metal_MechProp-1.ppt 1 Bruce Mayer, PE Engineering-45: Materials of Engineering Bruce Mayer, PE Registered Electrical & Mechanical Engineer Engineering 45 Mechanical Properties of Metals (1)

ENGR-45_Lec-14_Metal_MechProp-1.ppt 2 Bruce Mayer, PE Engineering-45: Materials of Engineering Learning Goals.1 – Mech Props  STRESS and STRAIN: What they are and why they are they used instead of LOAD and DEFORMATION  ELASTIC Behavior How Much Deformation occurs when Loads are SMALL? Which Materials Deform Least

ENGR-45_Lec-14_Metal_MechProp-1.ppt 3 Bruce Mayer, PE Engineering-45: Materials of Engineering Learning Goals.2 – Mech Props  PLASTIC Behavior Determine the point at which dislocations cause permanent deformation Which materials are most resistant to permanent deformation  TOUGHNESS and Ductility What they are How to Measure them

ENGR-45_Lec-14_Metal_MechProp-1.ppt 4 Bruce Mayer, PE Engineering-45: Materials of Engineering Materials Testing  In The USA the American Society for Testing and Materials (ASTM) Sets Many, Many Materials-Test Standards Formerly ASTM International  Founded in 1898, ASTM International is a not-for-profit organization that provides a global forum for the development and publication of voluntary consensus standards for materials, products, systems, and services. Over 30,000 individuals from 100 nations are the members of ASTM International, who are producers, users, consumers, and representatives of government and academia. In over 130 varied industry areas, ASTM standards serve as the basis for manufacturing, procurement, and regulatory activities. Formerly known as the American Society for Testing and Materials, ASTM International provides standards that are accepted and used in research and development, product testing, quality systems, and commercial transactions around the globe.

ENGR-45_Lec-14_Metal_MechProp-1.ppt 5 Bruce Mayer, PE Engineering-45: Materials of Engineering ELASTIC Deformation  Apply/Remove a SMALL Force Load to a Specimen 1. Initial3. Unload return to initial 2. SMALL load bonds stretch F  F  Force Load (lb or N)   Deformation in Response to the Load (in or m) F  Linear- elastic Non-Linear- elastic ELASTIC means REVERSIBLE

ENGR-45_Lec-14_Metal_MechProp-1.ppt 6 Bruce Mayer, PE Engineering-45: Materials of Engineering PLASTIC Deformation  Apply/Remove a LARGE Force Load to a Specimen PLASTIC means PERMANENT 1. Initial 3. Unload Planes Still Sheared & planes 2. LARGE load bonds stretch shear F  elastic+plastic  plastic F  linear elastic linear elastic  plastic

ENGR-45_Lec-14_Metal_MechProp-1.ppt 7 Bruce Mayer, PE Engineering-45: Materials of Engineering Engineering Stress,   Normalize Applied-Force to Supporting Area  TENSILE Stress, σ Area, A F t F t  F t A o original area before loading  SHEAR Stress,  Area, A F t F t F s F F F s Engineering Stress Units → N/m 2 (Pa) or lb/in 2 (psi)

ENGR-45_Lec-14_Metal_MechProp-1.ppt 8 Bruce Mayer, PE Engineering-45: Materials of Engineering 5 Simple tension: cable Simple shear: drive shaft Note:  = M/A o R here. Ski lift (photo courtesy P.M. Anderson) Common States Of Stress A o = cross sectional Area (when unloaded) FF M M A o 2R F s A c

ENGR-45_Lec-14_Metal_MechProp-1.ppt 9 Bruce Mayer, PE Engineering-45: Materials of Engineering 6 Simple COMPRESSION: Note: These are COMPRESSIVE structural members ( σ < 0; i.e., a NEGATIVE number) (photo courtesy P.M. Anderson) Common Stress States cont.1 A o (photo courtesy P.M. Anderson) Balanced Rock, Arches National Park

ENGR-45_Lec-14_Metal_MechProp-1.ppt 10 Bruce Mayer, PE Engineering-45: Materials of Engineering Common Stress States cont.2  BIAXIAL Tension Pressurized tank (photo courtesy P.M. Anderson) Tank Surface  HYDROSTATIC Compression Fish under water (photo courtesy P.M. Anderson)   < 0 h Surface Element

ENGR-45_Lec-14_Metal_MechProp-1.ppt 11 Bruce Mayer, PE Engineering-45: Materials of Engineering Engineering Strain,   LATERAL Strain  SHEAR Strain  Engineering STRAIN Units → NONE (Dimensionless) To Save Writing Exponents –µ-in/in –µm/m  TENSILE Strain 90º 90º -  xx   =  x/y = tan y 

ENGR-45_Lec-14_Metal_MechProp-1.ppt 12 Bruce Mayer, PE Engineering-45: Materials of Engineering Tensile Testing – Cyl Specimen  Std Specimen  Tension Tester 3/4-10 Thd  Other Tests Compression Test for Brittle Materials –e.g.; Concrete → GREAT in Compression, Fractures in Tension/Shear Torsion (twist) Test –Drive Shafts, Torsion Bars for Vehicle Suspension

ENGR-45_Lec-14_Metal_MechProp-1.ppt 13 Bruce Mayer, PE Engineering-45: Materials of Engineering Linear Elastic Deformation  Consider a Tension Test With SMALL loads; Plotting σ vs. ε Find  The Data Plots as a Line Through the Origin Thus σ  ε –The Constant of Proportionality is the Slope, E  E is the “Modulus of Elasticity”, or “Young’s Modulus” Linear Elastic Materials are said to follow Hooke’s (spring) Law F F simple tension test  Linear- elastic 1 E 

ENGR-45_Lec-14_Metal_MechProp-1.ppt 14 Bruce Mayer, PE Engineering-45: Materials of Engineering Linear Elastic Deformation  During a Pull-Test the Material CONTRACTS Laterally,ε L, as it Extends Longitudinally, ε. Plotting  This Data Also Plots as a Line Thus ε L  ε –The Constant of Proportionality is the Slope,  is “Poisson’s Ratio” as Defined by F F simple tension test  L  1 

ENGR-45_Lec-14_Metal_MechProp-1.ppt 15 Bruce Mayer, PE Engineering-45: Materials of Engineering Shear Modulus  Data From  vs.  Shear Stress Test Where –G  Modulus of Rigidity (Shear Modulus)  Leads to Hooke’s Law in Pure Shear THIN Walled Cylinder echanical#Mechanical  1 G   

ENGR-45_Lec-14_Metal_MechProp-1.ppt 16 Bruce Mayer, PE Engineering-45: Materials of Engineering Bulk Modulus  Data From P vs.  V Tests  Leads to Hooke’s Law in Pure HydroStatic Compression Pressure Test: Init. vol =V o. Vol chg. =  V P PP P P  V 1 -K V o Where –K  Modulus of Compression (Bulk Modulus) in GPa or Mpsi

ENGR-45_Lec-14_Metal_MechProp-1.ppt 17 Bruce Mayer, PE Engineering-45: Materials of Engineering Elastic (Hooke’s) Relations  Uniaxial Tension  Isotropic Material “Modulus Relations” Also Poisson’s Ratio  Pure Shear  All-Over Compression  Steel Properties E = GPa G = GPa K = GPa =

ENGR-45_Lec-14_Metal_MechProp-1.ppt 18 Bruce Mayer, PE Engineering-45: Materials of Engineering Elastic Properties of Metals

ENGR-45_Lec-14_Metal_MechProp-1.ppt 19 Bruce Mayer, PE Engineering-45: Materials of Engineering Metals Alloys Graphite Ceramics Semicond Polymers Composites /fibers E(GPa) Based on data in Table B2, Callister 7e. Composite data based on reinforced epoxy with 60 vol% of aligned carbon (CFRE), aramid (AFRE), or glass (GFRE) fibers. Young’s Moduli: Comparison 10 9 Pa E ceramics > E metals >> E polymers

ENGR-45_Lec-14_Metal_MechProp-1.ppt 20 Bruce Mayer, PE Engineering-45: Materials of Engineering Temperature Effects  Affect of Temperature on an Aluminum Alloy  In General for Increasing T E↓  L ↑ at Fracture  ↓ at Fracture

ENGR-45_Lec-14_Metal_MechProp-1.ppt 21 Bruce Mayer, PE Engineering-45: Materials of Engineering Some Linear Elastic Relations  UniAxial Tension  Simple Torsion, Solid Cylinder M=moment  =angle of twist 2r o L o –Material, geometric, and loading parameters contribute to deflection –Larger elastic moduli minimize elastic deflection F A o  /2  L LoLo w o  FLFL o EA o  L  Fw o EA o  2ML o  r o 4 G

ENGR-45_Lec-14_Metal_MechProp-1.ppt 22 Bruce Mayer, PE Engineering-45: Materials of Engineering WhiteBoard Work 6.66 kN Cu 380 mm d  Consider this Situation:  Given for Cu E = 110 GPa (16 Mpsi)  y = 240 MPa (35 ksi)  Find PreLoad/PreStrain Diameter, d, for a PostLoad/PostStrain Axial Extension δ = 0.5 mm