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Castigliano's method for calculating displacements is an application of his second theorem, which states: If the strain energy of a linearly elastic structure can be expressed as a function of generalised force Q i then the partial derivative of the strain energy with respect to generalised force gives the generalised displacement q i in the direction of Q i.
In classical mechanics, the Udwadia–Kalaba formulation is a method for deriving the equations of motion of a constrained mechanical system. [1] [2] The method was first described by Anatolii Fedorovich Vereshchagin [3] [4] for the particular case of robotic arms, and later generalized to all mechanical systems by Firdaus E. Udwadia and Robert E. Kalaba in 1992. [5]
The work W done by a constant force of magnitude F on a point that moves a displacement s in a straight line in the direction of the force is the product = For example, if a force of 10 newtons ( F = 10 N ) acts along a point that travels 2 metres ( s = 2 m ), then W = Fs = (10 N) (2 m) = 20 J .
Hence, the displacement of the structure is described by the response of individual (discrete) elements collectively. The equations are written only for the small domain of individual elements of the structure rather than a single equation that describes the response of the system as a whole (a continuum).
Betti's theorem, also known as Maxwell–Betti reciprocal work theorem, discovered by Enrico Betti in 1872, states that for a linear elastic structure subject to two sets of forces {P i} i=1,...,n and {Q j}, j=1,2,...,n, the work done by the set P through the displacements produced by the set Q is equal to the work done by the set Q through the displacements produced by the set P.
Equations and are the solution for the primary system which is the original system that has been rendered statically determinate by cuts that expose the redundant forces . Equation ( 5 ) effectively reduces the set of unknown forces to X {\displaystyle \mathbf {X} } .
The formula above for the principle of virtual work with applied torques yields the generalized force = = / = The mechanical advantage of the gear train is the ratio of the output torque T B to the input torque T A , and the above equation yields M A = T B T A = R . {\displaystyle MA={\frac {T_{B}}{T_{A}}}=R.}
For the n particle system, let the velocity of each particle P i be V i, then the virtual displacement δr i can also be written in the form [2] = = ˙, =, …,. This means that the generalized force, Q j , can also be determined as Q j = ∑ i = 1 n F i ⋅ ∂ V i ∂ q ˙ j , j = 1 , … , m . {\displaystyle Q_{j}=\sum _{i=1}^{n}\mathbf {F ...