Archive of Mechanical Engineering

Using a highly sensitive and precise apparatus, series of spatial movements of human cervical segments (C3/C4) were measured. They followed cyclic varied pure torques for axial rotation, lateral flexion, and flexion-extension in the presence of axially directed preloads as running parameter, whose force lines were shifted over the segments. By successive resections of the uncovertebral and zygapophysial joints as well as ligamental structures, the reach of these guiding structures for segmental kinematics and stiffness could be evaluated. For the first time, the biomechanical significance of the uncovertebral joints could be substantiated. In axial rotation and in lateral bending, the instantaneous helical axis (IHA) was found to be not stationary. Its position depended on the size of the rotational angle. The ensemble of the skew IHA formed a ruled surface with a waist. Torque and unit vector of the IHA were found to be parallel only for flexion-extension. In this case, all four joints were in guiding function, whereas in axial rotation and lateral flexion the joints alternated with each other. IHA included with torque T_z(t) for axial rotation ≈+30deg, and with torque T_x(t) ≈−30deg: These motions were coupled. Resection of all ligaments did hardly influence the kinematical structure.

In the presented work, the author introduces the ballistic energy absorbed by the shield m_pV²_BL/2 to elaborate the results of firing on homogeneous plates and multi – layered constructional shields. The introduced criterion V²_BL is used to determine ballistic thickness h_BL and ballistic velocity V_BL under normal firing 7.62 mm ŁPS bullets.

The experimental tests were performed on an unified test stand to investigate ballistic resistance of materials in field conditions. The stand was developed at the Naval University of Gdynia and then patented. The design of this test stand was based on the construction of ballistic pendulum arranged for measuring: the impact forces, the turn angle of ballistic pendulum φ, initial and residual velocities of the bullet. All the measurement data were transmitted to a digital oscilloscope and personal computer. The energy absorbed by the shield was subject to further analysis of V²_BL[R] according to Recht’s and Ipson’s method and of V²_BL[Z] according to author’s method. The verification of the above-mentioned dependences was based on the results of the tests. The ballistic velocities V_BL[R] and V_BL[R] of the steel and steel – aluminium alloy shields with air interlayer thicknesses of 0, 6, 12 mm were approximately equal, however, they were quite different for aluminium alloy multi – layered shields, according to the results of firing 7.62 mm ŁPS bullets. These properties were confirmed by the average mass coefficients α²_s and average effectiveness coefficients β_s of the V²_BL for the tested methods.

The paper presents the mathematical model of a pipelay spread. In the model, elasto-plastic deflections of the pipe, its large deformations and contact problems are considered. The modification of the rigid finite element method (REFM) is used to discretise the pipe. The problem is analyzed in two stages. First, the quasi-static problem is considered. The tip of the pipe is pulled from the reel to the tensioner. Then, dynamic analysis (during ordinary work) of the pipelay spread is carried out. Some results of numerical calculations are presented.

The paper presents application of guidance system for small, smart mortar missile. The presented control system is simple and inexpensive. It is based on a set of one time used impulse control engines and linear coordinator rotating with controlled object. Engines are mounted around the missile. There are no movable devices on the projectile board. The correcting impulses from rocket engines are perpendicular to main symmetry axis of the flying object and influence directly the centre of gravity of the guided missile. In the paper, authors describe the whole control system of the missile. Particular attention is focused on seeker and control devices. Numerical analysis presents some cases of the missile controlled flights.

The motion of a ring pack on a thin film covering a cylinder liner has been analysed. In contrast to the previous papers [30], [31], which considered a primary hydrodynamic phenomena (including mixed lubrication), in the present paper an additional degree of freedom of a ring i.e. a twist motion is also taken into account. Equations describing the twist of rings are presented and used in simulation. The twist phenomena of a single ring have been analysed in the past [25]. In this paper, the twist effects of separate rings forming a ring pack are considered. In the pack configuration, the twist of the upstream ring strongly influences the operation of the downstream ring. The phenomenon commonly treated as secondary effect seems to be influencing the ring motion strongly. Differences between results obtained applying and neglecting ring twist motion are analysed and discussed.