smart technologies for safety engineering

Dynamic Load Monitoring 119
Figure 4.16 Mass identification in the second phase of the impact (force and acceleration approach).
Acceleration measured on: (left) piston rod of the gas spring; (right) falling mass
mass (instead of the piston rod) is feasible only when joint movement of the body and the piston
occurs. In the case of the analysed structure it happened first 80 ms from the very beginning of
the impact process. Notice that the identification is not possible with the accelerometer sensor
located on the falling mass, since for integration the initial condition is required. In the case of
the piston rod it is zero, while in the case of the falling body it is exactly the impact velocity
being sought.
4.1.6.3 Approaches Based on The Conservation of Momentum
Verification of the momentum conservation approach for mass identification was performed
on the basis of Equation (6), which uses the restitution coefficient, and Equation (7), which is
based directly on the principle of conservation of momentum during the first contact impulse.
Figure 4.17 Velocity identification: integrated accelerations and differentiated displacements of piston
rod – an example