CMT - Lesson 11

• Tensile strength


  The ability of a material to withstand a pulling force
• Why are materials tested?

  • Ensure Quality
  • Test Properties
  • Prevent Failure in Use
  • Choose the Proper Materials
• Material properties determined by tensile testing(SDESMMM)

  • Strength
  • Ductility
  • Elasticity
  • Stiffness
  • Malleability
  • Modulus of Toughness
  • Modulus of Resilience
• Strength


  A fundamental property in the field of mechanics of materials, which deals with the behavior of solid objects UNDER VARIOUS STRESSES and STRAINS
• Ductility


  A mechanical property of a material that describes its ability to be DRAWN into a WIRE or stretched under tensile stress
• Elasticity


  A physical property of a material whereby the material returns to its ORIGINAL SHAPE after having been stretched out or altered by force
• Stiffness


  A material property that describes the extent to which an object RESISTS DEFORMATION in response to an applied force
• Malleability


  Refers to the ability of a material to undergo LARGE PLASTIC deformations under compressive stress
• Modulus of Toughness


  The amount of that ABSORBED ENERGY per unit of volume
• Modulus of Resilience


  The amount of STRAIN ENERGY per unit volume
• Five stages of tensile strength(PEYUB)

  • Proportional Limit
  • Elastic Limit
  • Yield Strength
  • Ultimate Strength
  • Breaking Strength
• Proportional Limit


  The point on the curve up to which the value of stress and strain REMAINS PROPORTIONAL
• Elastic Limit


  The limiting value of stress up to which the material is PERFECTLY ELASTIC
• Yield Strength


  The stress of a material that can withstand WITHOUT PERMANENT DEFORMATION
• Ultimate Strength


  The MAXIMUM STRENGTH a material can withstand while being stretched or pulled before failing or breaking
• Breaking Strength


  The MAXIMUM AMOUNT of TENSILE stress that the material can withstand before failure, such as fractures, breaking or permanent deformation
• The primary use of ASTM A370 is to determine the specified mechanical properties of steel, stainless steel, and related ALLOY products for the evaluation of conformance of such products
• The tensile strength of a STRUCTURAL steel bar is 400 Mpa and 841 Mpa for CARBON steel
• ASTM E8 | ASTM E8M describes uniaxial tensile testing of METALS at room temperature and the determination of characteristic values including yield strength, yield point, yield point elongation, tensile strength, strain at break and reduction of area
• Tensile specimen types

  • Flat Specimens
  • Round Specimens
• Five ways of specifying test speeds(SSCEF)

  • Specimen Strain Rate
  • Specimen Stress Rate
  • Crosshead Speed
  • Elapsed Time for Completing the test
  • Free-running Crosshead Speed
• Three control methods(SCC)

  • Stress Speed
  • Closed Loop Strain Rate
  • Crosshead Speed
• Universal Testing Machine


  It is used to TEST the TENSILE stress and COMPRESSIVE strength of materials
• Extensometer


  An INSTRUMENT that measures the ELONGATION of a material under stress
• Two classes of extensometer

  • Contact Extensometer
  • Non-contact Extensometer
• Contact Extensometer


  It test the deformation by directly placing a physical object onto the sample such as a KNIFE-EDGE
• Non-contact Extensometer


  It uses CAMERAS and LIGHT to determine the deformational parameters without physically touching the sample
• Shimming materials


  Used to fill SMALL GAPS or SPACES between objects
• Steel bars


  Use as a TENSION DEVICE in reinforced concrete and masonry structures to strengthen and aid the base material under tension
• Benefits of tensile testing(QCDM)

  • To determine batch quality
  • To determine consistency in manufacture
  • To aid the design process
  • To reduce material costs