Investigating the transverse motion of a pneumatic shock exciter using two different anvil mounting configurations

This paper describes novel design changes to the accelerometer mounting support of a commercial pneumatic shock exciter, with the aim of reducing the transverse motion the accelerometer is subjected to during shock excitation. The author describes the mounting support supplied by the manufacturer, the design changes made and the measurement data to compare the transfer motions recorded using two different mounting designs.

Design and technological provision of wear resistance of elastomer surface of rubber-cord casings of damping devices

Two main factors are considered that determining the friction between non-lubricated surfaces of an elastomer and a solid base during their relative motion. The first one is adhesion in the areas of real (actual) catalysis and the second factor is the deformation component, which is due to the delay of recovery of the elastomer after the irregularity is introduced and it is called the hysteresis component of friction. One of the main problems of increasing the resource of pneumatic dampers is minimizing the wear of the covering layer of the rubber-cord casing (RCC). The wear of the RCC is due to the fact that sliding friction occurs in the process of contact between the metal surface and the surface of the RCC, as a result of which the cover layer of the RCC (in some cases with the first cord layer) wears out, depending on the chemical composition of the rubber and the features of the operation of the pneumatic shock absorber. In order to minimize the wear of rubber, it is proposed to change the design of the pneumatic damper so that rolling friction dominates in the contact between the surfaces of rubber and metal

The influence of the shock absorber type on the stability of an ambulance vehicle to the rolls of its spring-suspended weight

The article presents the results of assessing the stability of the ambulance vehicle to lateral and longitudinal rolls regarding them as parameters affecting the quality of health care to the transported victim. The authors present the results of a road testing aimed at assessing the vehicle resistance to such rolls under conditions of imitation of a seriously ill patient`s delivery to a medical institution. The tests were carried out on ambulances equipped on the basis of Ford Transit vehicles, using various types of damping elements in the suspension, namely, two variants of two-tube hydraulic shock absorbers; one-tube hydro-pneumatic shock absorbers; air suspension. As the estimated parameters, there were used the values of actual angular acceleration of the passenger compartment rolls in comparison with the values admissible for medical indicators. It is shown that from the standpoint of providing the best comfort for the patient and the medical crew of ambulance, it is preferable to use in the vehicle suspension the single-tube hydro-pneumatic shock absorbers, the installation of which is permissible under conditions of operational modernization of the vehicle.

Comprehensive design of an oleo-pneumatic nose landing gear strut

A comprehensive design cycle of a nose landing gear strut having an oleo-pneumatic shock absorber for a lightweight aircraft is proposed. Design and analysis of a retractable nose landing gear according to Airworthiness Standards FAA FAR Part 23 have been carried out. This research is focused on mathematical modeling of an oleo-pneumatic strut with an analytical solution of design variables at static and dynamic loading conditions. The variation of spring and damping characteristics of an oleo-pneumatic shock absorber with the stroke length is also presented. Feasibility of equivalent mechanical spring and damper along with comparison of pneumatic as air spring and oleo as hydraulic damper is studied. Numerical integration technique was used to solve the dynamic model of an oleo-pneumatic strut with forcing function of an impact force during touch down scenario. Energy conservation principle was used to determine height required for drop tests. Parametric study of anteversion angle within the constraints of ground clearance and volume in the fuselage determined an optimized angle of nose landing gear strut. Based on the maximum pressure and impact force encountered during landing, the hydraulic cylinder and piston design was finalized. In order to validate the proposed design cycle for preliminary phase, a structural integrity of cylinder and piston assembly was carried out using finite element analysis. Deformation, maximum stresses and factor of safety validated the proposed design cycle of a nose landing gear strut specific to a general aviation aircraft having all up mass of 1600 Kg.

Multi-physics based Simulations of an Oleo-pneumatic Shock Absorber System for PHM

The paper presents multi-physics (Mechanical, Thermal, Hydraulic, and Pneumatic) based modelling and simulation of an Oleo-pneumatic shock absorber with fault capabilities. The fault simulated in this model is leakage due to eccentricity. The one-dimensional shock absorber system models to give loads at different sink velocities. These load values, used in the structural model to do static stress analysis. By using these loads directly from the system model eliminates the error in load computation from the load’s group, thereby eliminating the time and cost involved in this activity. The models and static stress analyses carried out with both 1-D and 3-D elements. The 3-D landing gear model meshed with using both auto and manual mesh generation options. The consequences of both 1-D and 3-D models mesh generation, discussed in this paper. The static stress analysis, compared with the experimental results and it is found that the results are within 5% deviation. Based on the static stress and fatigue analysis computed the life of a landing gear.

ВИЗНАЧЕННЯ ВПЛИВУ ТЕХНОЛОГІЧНИХ ЧИННИКІВ НА ПРОЦЕС ІНТЕНСИФІКАЦІЇ ПНЕВМОУДАРНОГО ШТАМПУВАННЯ ВИТЯГУВАННЯМ І ТОЧНІСТЬ ШТАМПОВАНИХ ДЕТАЛЕЙ

This work is devoted to experimental studies to determine the influence of technological factors on the process of intensification of pneumatic shock punching by drawing and accuracy of stamped products. The process of pneumatic shock extraction, as well as other impulse methods of extraction (explosive, electrohydraulic and magneto-pulse) is complicated by the high speed of deformation and, accordingly, by the occurrence of considerable inertial forces that counteract the movement of the flange of the extracted part. In the case of pneumatic shock reduction of the deformation rate can be achieved by adjusting the relative weight of the striker or by applying a two-stroke stretching. It is experimentally confirmed that the greatest influence on the limit values of the stamping ability in pneumatic impact stamping have the properties of the workpiece material, its surface properties, the scheme of the deformation process, the rate of deformation, the geometry of the matrix or punch, the value of contact friction and intensification techniques. Experiments have shown that the following factors have the greatest influence on the ultimate degree of drawing and the quality of the products: the condition of the surface and the physical and mechanical properties of the workpiece material; the radius of curvature of the working edge of the matrix; the relative thickness of the workpiece; workpiece loading rate (parameter α); the frictional properties of the matrix material and the workpiece; quality of greasing; technological scheme of operation. For two-stroke stretching, the stretching limit is increased by 8-10%. Also, when using two-stroke load, as shown by experiments, the amount of thinning in dangerous sections of the finished product is reduced. The reduction of radial deformation in the centre of the samples reaches 20-25%. The accuracy of pneumatic shock punching by a liquid is very high, since the deviation of the measured diameters does not exceed 0.1 mm. The surface quality of the pneumatic impacted products is determined only by the surface quality of the starting material. The pneumatic shock method of punching using a two-stage folded dash allows to increase the degree of drawing, accuracy and quality by means of a two-stroke loading, that is, to intensify the process of deep drawing of sheet products. The intensification is due to the successive double shock load for one cycle of the PUSH installation – the first blow is a formative, and the subsequent blow of the second stage is a calibration.

Research of the elastic characteristics of the new hydropneumatic shock absorber

The article is devoted to research on ensuring smooth running of vehicles, and specifically, the theoretical modeling of the damping characteristics of a new design of hydro-pneumatic shock absorber. There has been developed a mathematical model describing the characteristics implemented in MathCad. The influence of various factors on the parameters of the characteristics is studied.