Yield load:

The point in the stress-strain curve at which the curve levels off and plastic deformation begins to occur. When something is stressed and stretches and after the load is taken off it goes back to the original position - this is plastic deformation, it has not yet ‘Yielded’. The Yield Load is the load which is great enough so it goes past this point, becomes inelastic and doesn’t return/go back to its original shape/position.

Source: http://en.wikipedia.org/wiki/Yield_%28engineering%29

Offset yield point (proof stress)

When a yield point is not easily defined based on the shape of the stress-strain curve an offset yield point is arbitrarily defined. The value for this is commonly set at 0.1 or 0.2% of the strain.[5] The offset value is given as a subscript, e.g., Rp0.2=310 MPa.[citation needed] High strength steel and aluminum alloys do not exhibit a yield point, so this offset yield point is used on these materials.[5]

Source: http://en.wikipedia.org/wiki/Yield_(engineering)#cite_ref-ross59_5-0

Tensile load

Tensile load or ultimate strength is the maximum stress that a material can withstand while being stretched or pulled before failing or breaking. This is higher than the Yield Load.

Source: http://en.wikipedia.org/wiki/Tensile_load

Shear Load

Shear strength is the strength of a material or component against the type of yield or structural failure where the material or component fails in shear. A shear load is a force that tends to produce a sliding failure on a material along a plane that is parallel to the direction of the force. When a paper is cut with scissors, the paper fails in shear. Shear strength is the strength a component or fastener has from a force at 90 degrees to the direction of the bolt or component. It would be calculated by an Engineer through testing or using the fastener/components Yield and Tensile Strengths. Unlike tensile and yield strengths, there are no published shear strength values or requirements for ASTM fastener specifications. The Industrial Fastener Institute (Inch Fastener Standards, 7th ed. 2003. B-8) states that shear strength for fasteners is approximately 60% of the minimum tensile strength.

Source: http://www.portlandbolt.com/faqs/calculating-strength/

http://en.wikipedia.org/wiki/Shear_strength

Standard Safety Factor

To determine the standard safety factor of a wire rope, cable or fittings, the nominal strength or Breaking Load (BL) must be reduced by a safety factor. The BL of a wire rope should be considered the straight line pull which will actually break the wire. The nominal strength or BL of a wire rope should never be used as its working load.

The safety factor is the ratio of strength of the rope or strand, or fitting to the Working Load Limit required. It is impossible to establish a uniform safety factor as it will depend upon the type of work performed, government regulations, loads applied, speed of operation, length of wire rope used, etc. As a guideline, designers/installers commonly use a the standard safety factor of 25% of Breaking Load, i.e. a 4:1 safety factor.