A sensing-oriented finite element framework is developed to evaluate impact-induced mechanical responses and their relationship with acceleration-based head injury assessment. A three-dimensional helmet–head model consisting of a helmet shell, nonlinear expanded polystyrene liner, skull, and simplified brain structure is established. Dynamic impact simulations are performed for frontal, rear, top, and lateral orientations under different impact velocities. Stress, displacement, and acceleration responses are numerically extracted from the finite element model, and the acceleration–time histories are used for head injury criterion assessment. The results reveal direction-dependent stress concentrations and velocity-dependent deformation, with frontal and rear impacts generally producing higher local stresses. Increasing impact velocity also results in greater rebound displacement and more severe dynamic responses. Beyond the conventional mechanical response analysis, the proposed framework relates spatial stress and displacement characteristics to the numerically obtained acceleration–time responses of the simulated head, which represent the physical quantities that could subsequently be measured using accelerometers or inertial measurement units in an instrumented helmet. These responses also provide reference information for determining potential sensing locations and measurement requirements.