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Lets look at a few terms relating to STRENGTH of steel. Theres a lot of information here, but much more to come. I think this will help in understanding how complex the issues of picking a steel is. The issue is how the steel reacts to the applied forces. Here we're looking at the types of strength there are. Look carefull at Yield strength and Tensile strength. When we get to testing and determining how to measure strength in particular geometries, this will be important.
Comparison of strengths between several types of steels is next; then more terms and finally some tests to determine characteristics of steel.
The following is reprinted from MATERIALS ENGINEERING, June 1967 issue, Reinhold Publishing Corporation, 430 Park Avenue, New York, N. Y. 10022.
Bending strength. Alternate term for flexural strength. It is most commonly used to describe flexure properties of cast iron and wood products.
Breaking strength. Tensile load or force required to rupture textiles (e.g., fibers, yarn) or leather. It is analogous to breaking load in a tension test. Ordinarily, breaking strength is reported as lb or lb/in. of width for sheet specimens.
Cohesive strength. Theoretical stress that causes fracture in tension test if material exhibits no plastic deformation.
Compressive strength. Maximum stress a material can sustain under crush loading. The compressive strength of a material that fails by shattering fracture can be defined within fairly narrow limits as an independent property. However, the compressive strength of materials that do not shatter in compression must be defined as the amount of stress required to distort the material an arbitrary amount. Compressive strength is calculated by dividing the maximum load by the original cross section area of a specimen in a compression test.
Creep strength. Maximum stress required to cause a specified amount of creep in a specified time. Also used to describe maximum stress that can be generated in a material at constant temperature under which creep rate decreases with time. Alternate term is creep limit.
Fatigue strength. Magnitude of fluctuating stress required to cause failure in a fatigue test specimen after a specified number of cycles of loading. Usually determined directly from the S-N diagram.
Impact strength. Energy required to fracture a specimen subjected to shock loading, as in an impact test. Alternate terms are impact energy, impact value, impact resistance and energy absorption. It is an indication of the toughness of a material.
Tensile strength. Ultimate strength of a material subjected to tensile loading. It is the maximum stress developed in a material in a tension test.
Ultimate strength. Highest engineering stress developed in material before rupture. Normally, changes in area due to changing load and necking are disregarded in determining ultimate strength.
Yield strength. Indication of maximum stress that can be developed in a material without causing plastic deformation. It is the stress at which a material exhibits a specified permanent deformation and is a practical approximation of elastic limit. Offset yield strength is determined from a stress-strain diagram. It is the stress corresponding to the intersection of the stress-strain curve and a line parallel to its straight line portion offset by a specified strain. Offset is usually specified as 0.2 %, i.e., the intersection of the offset line and the 0-stress axis is at 0.2 % strain.
Comparison of strengths between several types of steels is next; then more terms and finally some tests to determine characteristics of steel.
The following is reprinted from MATERIALS ENGINEERING, June 1967 issue, Reinhold Publishing Corporation, 430 Park Avenue, New York, N. Y. 10022.
Bending strength. Alternate term for flexural strength. It is most commonly used to describe flexure properties of cast iron and wood products.
Breaking strength. Tensile load or force required to rupture textiles (e.g., fibers, yarn) or leather. It is analogous to breaking load in a tension test. Ordinarily, breaking strength is reported as lb or lb/in. of width for sheet specimens.
Cohesive strength. Theoretical stress that causes fracture in tension test if material exhibits no plastic deformation.
Compressive strength. Maximum stress a material can sustain under crush loading. The compressive strength of a material that fails by shattering fracture can be defined within fairly narrow limits as an independent property. However, the compressive strength of materials that do not shatter in compression must be defined as the amount of stress required to distort the material an arbitrary amount. Compressive strength is calculated by dividing the maximum load by the original cross section area of a specimen in a compression test.
Creep strength. Maximum stress required to cause a specified amount of creep in a specified time. Also used to describe maximum stress that can be generated in a material at constant temperature under which creep rate decreases with time. Alternate term is creep limit.
Fatigue strength. Magnitude of fluctuating stress required to cause failure in a fatigue test specimen after a specified number of cycles of loading. Usually determined directly from the S-N diagram.
Impact strength. Energy required to fracture a specimen subjected to shock loading, as in an impact test. Alternate terms are impact energy, impact value, impact resistance and energy absorption. It is an indication of the toughness of a material.
Tensile strength. Ultimate strength of a material subjected to tensile loading. It is the maximum stress developed in a material in a tension test.
Ultimate strength. Highest engineering stress developed in material before rupture. Normally, changes in area due to changing load and necking are disregarded in determining ultimate strength.
Yield strength. Indication of maximum stress that can be developed in a material without causing plastic deformation. It is the stress at which a material exhibits a specified permanent deformation and is a practical approximation of elastic limit. Offset yield strength is determined from a stress-strain diagram. It is the stress corresponding to the intersection of the stress-strain curve and a line parallel to its straight line portion offset by a specified strain. Offset is usually specified as 0.2 %, i.e., the intersection of the offset line and the 0-stress axis is at 0.2 % strain.