A shear panel element in a finite element model of an airframe represents
Answer: C
The shear panel is the direct counterpart of the idealised skin, and combining rods with shear panels reproduces the classical boom idealisation inside a finite element model. It remains common in airframe stress work for exactly that reason.
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Mesh convergence in a finite element model is demonstrated by
Answer: D
A single result from one mesh proves nothing about its accuracy. Refining and observing the quantity of interest settle is the only evidence that the discretisation error has become small, and it should be done for the quantity that matters rather than in general.
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A stress singularity at a re-entrant corner in a finite element model
Answer: A
The elasticity solution is genuinely unbounded at a sharp re-entrant corner, so refining the mesh simply produces a larger number. The real structure has a fillet, and either the fillet must be modelled or the result interpreted through a different method.
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Boundary conditions in a structural model should be chosen to
Answer: B
Over-constraining stiffens the model and attracts artificial load into the supports, while under-constraining leaves it free to move as a rigid body. Both errors are common, and the reaction forces are a useful check that the restraint is behaving as intended.
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Saint-Venant's principle justifies idealising a load application because
Answer: C
At distances comparable with the member's own dimensions, two statically equivalent load systems produce the same stress field. It is what allows a bolt pattern to be replaced by a single force, provided the region of interest is not the joint itself.
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Fasteners in a global airframe model are often represented by
Answer: D
A calibrated spring reproduces the joint's flexibility, which materially affects load distribution between parts, without the cost of modelling every fastener in three dimensions. Treating every joint as rigid stiffens the model and misdistributes the load.
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A global-local modelling approach means
Answer: A
The coarse model captures the overall stiffness and load distribution, and its displacements or forces are then applied to a finely meshed submodel of the region of interest. It gives detailed stresses where they are needed without meshing the entire aircraft at that density.
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Symmetry can be exploited in an idealisation only when
Answer: B
A symmetric structure under asymmetric loading does not behave symmetrically, so the half model would be wrong. Where both conditions hold, half or quarter models with appropriate symmetry boundary conditions halve or quarter the work.
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An idealised model should always be checked by
Answer: C
Summing the reactions and comparing them with the applied load is the cheapest and most revealing check available, and it catches misapplied loads, wrong units and unintended restraints. Deformed shape plots and simple hand calculations are the natural companions to it.
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Comparing a finite element result with a simple hand calculation is valuable because it
Answer: D
A hand check will not validate the fine detail, but it will reveal an answer wrong by a factor of a thousand or with the wrong sign. Order-of-magnitude agreement is the minimum standard before any detailed result is believed.
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