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allowable load – Or permissible load, also known as the working load or design load. Basically it is the maximum load expected to be applied to the part when it is in operation. The maximum load that a structural member or machine component will be allowed to carry under normal conditions of utilization is considerably smaller than the ultimate load. This smaller load is referred to as the allowable load.
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breaking strength – Same as fracture strength. Sometimes in engineering, breaking strength is also used to denote the strength at which a designed part breaks under the type of loading condition it is designed for. For example, the breaking strength for a chain link might be the strength at which it breaks under tension from two other chain links pulling on it at opposing ends.
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compression – Can be thought of as pushing, squeezing. (picture)
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deflection – Also referred to as elongation or deformation. Abbreviated by δ, used in Eq1 in the lesson Normal Strain. It is the change in length of a part due to an applied axial force. The units are in length.
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deformation – Also known as deflection. (has a different meaning in fluid mechanics)
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design load – Should be same as allowable load. Also known as working load or permissible load.
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ductile rupture – A type of failure that occurs when the plastic deformation, in a machine part that exhibits ductile behavior, is carried to the extreme so that the member separates into two pieces. Initiation and coalescence of internal voids slowly propagate to failure, leaving a dull, fibrous rupture surface.
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elastic limit – The largest value of the stress for which a material behaves elastically. If a specimen is loaded beyond this point, the deformation is said to be plastic ad the material will take on a permanent set when the load is removed. See the lesson Stress-Strain Diagram.
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elastic modulus – Same as modulus of elasticity.
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elongation – Is deflection.
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fracture strength – The value of nominal stress obtained when the load carried by a tensile specimen at the time of fracture is divided by its cross-sectional area. Fracture strength is not used as a material property in mechanical design.
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isotropic – Independent of direction.
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lower yield point – The point corresponding to the load required to maintain yield. The lower yield point should be used to determine the yield strength of a material. Typically associated with more ductile materials. Can be located on a stress-strain diagram. In contrast to the upper yield point. (picture)
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modulus of elasticity – Abbreviated by E. Also known as Young's modulus, or elastic modulus. Commonly associated with Hooke's Law. The units are in terms of stress. Every material has a unique elastic modulus value. The modulus of elasticity is the slope of the linear part of the stress-strain curve. The modulus of elasticity is a measure of the stiffness of a material.
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modulus of rigidity – Is a material stiffness property (it is a material-specific property). Abbreviated by G. Also known as shear modulus, shear modulus of elasticity, or torsional modulus. The modulus of rigidity is anywhere from one third to one half the magnitude of the modulus of elasticity for most materials. For material values go to Engineering Data External Links
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nominal strain – Same as engineering strain.
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nominal stress – Same as engineering stress.
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offset yield strength – see lesson Offset Yield Method.
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permissible load – Should be same as allowable load. Also known as design load or working load.
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proportional limit – The largest value of the stress for which Hooke's law can be used for a given material. Everything before the proportional limit can be fitted to a linear relationship. (picture) (also see Stress-Strain Diagram)
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section modulus – There are two types: elastic section modulus and plastic section modulus.
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shear – A force which is the magnitude of the resultant of shearing forces that exist in the plane of a section of a member. These internal forces are due to transverse forces acting on the member. See the given picture. In physics, shear might actually be referred to as a stress.
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shear force – Also known as shearing force. A force which is the magnitude of the resultant of internal forces that exist in the plane of a section of a member. These internal forces are due to transverse forces acting on the member. See the given picture. In physics, shear might actually be referred to as a stress.
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shear modulus – Also known as modulus of rigidity, shear modulus of elasticity, or torsional modulus.
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shear modulus of elasticity – Also known as modulus of rigidity, shear modulus, or torsional modulus.
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statically indeterminate structure – When the structure is held by more supports than are required to maintain its equilibrium. This results in more unknown reactions than available equilibrium equations.
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strength – In mechanics of materials, and machine design, often refers to stress. See lesson on Difference Between Stress and Strength.
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tension – The longitudinal deformation of an elastic body that results in its elongation. The force producing such deformation. Can be thought of as pulling, stretching. The act of stretching or straining. The state of being stretched or strained. A body that has pulling forces applied at its ends is in tension. (picture)
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tensile – Of or pertaining to tension. Capable of being stretched or drawn out; ductile.
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tensile force – A force in tension.
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tensile stress – Typically refers to normal stress, or stress that is experienced in the same direction as the tensile load.
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tensile strength – Usually refers to ultimate strength, especially in metallurgy and materials science.
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torsionalmodulus – Also known as modulus of rigidity, shear modulus, or shear modulus of elasticity.
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upper yield point – The point corresponding to the load reached just before yield starts. The upper yield point is transient. Typically associated with more ductile materials. Can be located on a stress-strain diagram (picture).
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working load – Should be same as allowable load. Also known as design load or permissible load.
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yield – When a material yields, it physically changes its shape under an applied load; elongate; deform.. To give way to force, pressure, etc., so as to move, bend, collapse, or the like. In everyday terms, one definition is: to concede under some degree of pressure, but not necessarily to surrender totally.
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yield point – The point at which the strain begins to increase very rapidly without a corresponding increase in stress. Not all materials have an obvious yield point, especially for brittle materials. Also see upper yield point and lower yield point.
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Young's modulus – Same as modulus of elasticity.
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