Material Properties Engineering Mechanical Laboratory AUTOMOTIVE DESIGN AND MANUFACTURING International Program, Chulalongkorn University

Lecturer Aj. Thanyarat SINGHANART (TSN) Office room : AUTO. Bldg. 2 nd floor, room 213

Brackgrounds

Challenger was destroyed in the second minute of STS-51-L, the orbiter's tenth mission, on January 28, 1986, when an O-ring seal on its right solid rocket booster (SRB) failed. The O-rings failed to seal due to a variety factors, including unusually cold temperatures. This failure allowed a plume of flame to leak out of the SRB and impinge on both the external fuel tank (ET) and SRB aft attachment strut. This caused both structural failure of the ET, and the SRB pivoted into the orbiter and ET. The vehicle assembly then broke up under aerodynamic loads. STS-51-LJanuary O-ringsolid rocket boosterexternal fuel tank

O-ring “Properties drop in low temperature”

Mathematical Models Deformation of Axially-Loaded Member Deformation of Torsion Member Deflection of Beam Buckling Safety Factor

Objectives  To study how to test the materials for obtaining the desired properties.  Tensile test  Hardness test  Impact test  To study how to evaluate the mechanical properties of the materials.  Etc. （ Options)  Can we relate the material properties to applications?  Can we determine the tensile strength from the hardness value?  Can we explain the fracture mechanism of ductile and brittle materials?  etc.

STANDARD : Tensile test

STANDARD : Hardness test

STANDARD : Impact test

Testing Machines Materials: - Construction Steel - Shaft Steel - Cast Iron - Aluminum - Brass

Stress-Strain Relationship

Data Reduction (Tensile Test) Young’s Modulus 0.2% offset Yield Stress Tensile Strength % Elongation % Reduction of Area Modulus of Resilience Modulus of toughness Etc.

Hardness test Materials: - Steel - Steel after hardening process

Impact test Materials: - Steel - Aluminum - Brass

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