When I read Reddy's book, "Energy Principles and Variational Methods in Applied Mechanics", Chapter 5.1. I am confused with the two jargons "the principle of virtual displacement" and "the principle of virtual work". They are used interchangeably without clarification. Could someone explain the difference between them?
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1$\begingroup$ The are the same thing. $\endgroup$– mike stoneCommented May 24, 2020 at 18:22
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$\begingroup$ I thought so. Thx! $\endgroup$– Jonas LionelCommented May 25, 2020 at 19:34
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2 Answers
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Loosely, work is force times displacement (more precisely $W=\int \vec F.d\vec r$ ).
Virtual work is force times virtual displacement( $dW= \vec F.d\vec r$ ).
It is regarded as "virtual", because the object does not actually move, but we imagine it moving an infinitesimal displacement $d\vec r$, which we call virtual displacement.
answered May 24, 2020 at 18:28
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Finally, I found the answer from Reddy's book. "the principle of virtual work" and "the principle of virtual displacement" refer to the same thing while "the principle of virtual force" and "the principle of complementary virtual work" refer to one other principle.