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Screw theory is the algebraic calculation of pairs of vectors, also known as dual vectors [1] – such as angular and linear velocity, or forces and moments – that arise in the kinematics and dynamics of rigid bodies. [2] [3]
Graph of Johnson's parabola (plotted in red) against Euler's formula, with the transition point indicated. The area above the curve indicates failure. The Johnson parabola creates a new region of failure. In structural engineering, Johnson's parabolic formula is an empirically based equation for calculating the critical buckling stress of a column.
Metric threaded rods are marked on the end with a color code to define the ISO strength class. The color codes are: [9] Unmarked — 4.6 class (tensile strength = 400 N/mm 2, yield strength 240 N/mm 2) Yellow — 8.8 class (800 N/mm 2, 640 N/mm 2) Green — A2 stainless steel (304) Red — A4 stainless steel (316) White — 10.9 class (1000 N ...
The screw is a mechanism that converts rotational motion to linear motion, and a torque (rotational force) to a linear force. [1] It is one of the six classical simple machines. The most common form consists of a cylindrical shaft with helical grooves or ridges called threads around the outside.
Where L e is the thread engagement length, A t is the tensile stress area, D is the major diameter of the screw, and p is the pitch. This equation only holds true if the screw and female thread materials are the same. If they are not the same, then the following equations can be used to determine the additional thread length that is required: [14]
Strength depends upon material properties. The strength of a material depends on its capacity to withstand axial stress, shear stress, bending, and torsion.The strength of a material is measured in force per unit area (newtons per square millimetre or N/mm², or the equivalent megapascals or MPa in the SI system and often pounds per square inch psi in the United States Customary Units system).
Fig. 1: Critical stress vs slenderness ratio for steel, for E = 200 GPa, yield strength = 240 MPa. Euler's critical load or Euler's buckling load is the compressive load at which a slender column will suddenly bend or buckle. It is given by the formula: [1] = where
The screw itself should be drilled a minimum of 1" into the concrete to hold effectively and a maximum of 1-3/4" or the threads will wear and will lose holding power. Ideally 1-1/4" to 1-1/2" of screw thread in the concrete. [1] So for example, if a 1/2" board is being screwed onto the concrete, a 1-3/4" to 2" concrete screw should be used ...