MECHANICAL AND CHEMICAL PROPERTIES OF METALS
Ñ Review documentation related to the actual properties of base and filler metal
Ñ Compare specification values with actual numbers to judge compliance
Ñ He can predict problems which may accur during welding
Mechanical Properties of Metal :
a. Strength
b. Ductility
c. Hardness
d. Toughness
e. Fatigue strength
a. STRENGHT is defined as the capacity of a material to withstand some applied load.
Ñ Tensile strength
Ñ Compressive strength
Ñ Shear strength
Ñ Torsional strength
Ñ Impact strength
Ñ Fatigue strength
Ñ Tensile strength is described as ability of metal to resist failure when subjected to a tensile, or pulling load.
Ñ Tensile strength expressed into two defferent ways i.e Ultimate tensile strength (tensile strength) and Yield strength.
Ñ Ultimate tensile strength (tensile strength) relates to the maximum load carrying capasity of metal, or failure occurs.
Ñ Yield strength is meant when a metal behaves elastically.
Ñ Behavior changes from elastic to plastic is referred to as its yield point.
Ñ Determined by conducting a tensile test, it is also possible to make indirect measurement of strength using hardness test. If hardness increases, tensile strength increase.
Ñ As temperature increases, the strength of a metal will decreases.
Ñ As temperature increases, the ductility increases as well and vice versa.
b. Ductility
Ñ The ability of a material to deform, or stretch (menegang), without failing
Ñ More ductile the more it will stretch.
Ñ Determines whether the metal fails gradually (high ductility) or suddenly (low ductility) when loaded.
Ñ Low ductility is reffered to as being brittle (no deformation before fracture)
Ñ The ductility can be expressed in one of two ways, either as percent elongation or percent reduction area.
Ñ The strength and ductility of a rolled metal is greatest in the direction of rolling.
c. Hardness
Ñ It is defined as the ability of a material to resist identification.
d. Toughness
Ñ The ability of material to absorb energy
Ñ The low toughness value difines brittle behaviour while a high value of toughness is related to a ductile failure.
Ñ The temperature is reduced, the toughness of metal decrease as well.
e. Fatigue strength
Ñ Defined as that strength to resist failure under repeated load applications
Ñ The majorrity of metal failures are the result of fatigue.
Ñ Related to the number of cycles required to cause a failure
Ñ Determined though fatigue testing.
Ñ The S-N curve is simply a graphic description of how many fatigue cycles are necessary (perlu) to produce a failure at various stress level.
Ñ A surface discontinuities, will more quickly lead to fatigue failure.
Chemical Properties of Metals
Ñ Drastic changes will also occur if the chemical composition is change
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