The applied load throughout the load path must be balanced by the total reaction at the end of the load path thus resulting in a static equilibrium. A static analysis is based on the satisfactory convergence of equations of equilibrium. The answer actually lies in the question. So how can one manage to create unwanted mechanisms in a static analysis? This behavior is termed as a ‘mechanism’, similar to mechanisms in machines. If there is a lack of constraint or stiffness in a particular direction and there is some kind of applied loading in that direction, then the system will either move or rotate in that direction unrestrained which results in a fatal error when you run the analysis. What in the world is a mechanism you ask?Ī mechanism is any part of the model that is a joint, or a link or a load path where two elements are connected together at a common node. But what the heck is it doing in a linear static analysis? It is actually quite simple. A rigid body mode in a linear static analysis is basically a ‘mechanism’ that exhibits a rigid body mode.
So we now know what a rigid body mode is in terms of a normal modes analysis. We value your privacy and would never spam you Rigid Body Mode in a static analysis: These first 6 modes will have zero or close to zero modal frequency. If any part of this rigid body is constrained in any way, the corresponding rigid body mode will go away. So now let us talk about using this to our advantage in a linear static or nonlinear static analysis. This means the body will not undergo any internal deformation but will be able to move or rotate freely.
RIGID BODY EQUILIBRIUM 3D FREE
Definition of a Rigid body Mode:Ī rigid body mode is defined as the free translation or rotation of a body without undergoing any significant internal deformation.įor a free free normal modes analysis where there are no loads or constraints, there will be 6 rigid body modes, three translational (TX, TY, TZ) and three rotational (RX, RY, RZ). For example, in a linear static or a non linear static analysis. Surprised? Don’t be, let us look at the definition of a rigid body mode. It is true that a rigid body mode is in fact commonly encountered in such analyses. However, there are other analysis types where this term is also used.
Normally, when you hear someone say rigid body mode, the first thing that comes to mind is Modal or Normal Modes analysis. Recently when I asked my subscribers for a blog post topic, I received a ton of awesome suggestions, thank you to all of those who took the time to send me those. So picking one out those many great suggestions, in this post we will discuss the term “Rigid Body Mode”. Ready? Let’s go… So what exactly is a rigid body mode? What is a Rigid Body Mode? Click here to access pdf versions of the latest blog posts…
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