Dynamic Response of the Inertial Platform of the Laser ELI-NP Magurele-Bucharest Facility

Previous studies on the vibrational behavior of the inertial platform installed at ELI-NP, in Magurele-Bucharest have reported eigenfrequencies in the domain in which excitations can occur from earthquakes which manifests itself periodically in this geographical area. The paper aimed to study the vibrational response that may occur, due to human activities or natural phenomena (earthquakes), at the inertial platform of the Laser + Gamma building within the ELI-NP complex. The large mass of the platform, 54,000 tons in full condition, must ensure that the experiments are carried out without being disturbed by unwanted vibrations. The laser and gamma beam must be very precisely positioned and the shocks and vibration from the external environment must be damped or absorbed. To realize this, the behavior of the inertial concrete platform at external excitations was studied based on a model with finite elements. The response to the forced vibrations of the platform and the possible behavior in case of an earthquake were obtained

Impact Attenuator Design for Improvement of Racing Car Drivers’ Safety

An essential element for driver safety is represented by the Impact Attenuator (especially for race cars). The effect of the Impact Attenuator can be seen in the behavior of a dummy, tied with a seat belt, in a frontal collision with a rigid wall. The loads that act on the dummy are determined and checked to see if they fall within the values recommended by existing standards. The car is considered a structure with a dummy fixed with a seat belt and equipped with an Impact Attenuator. Two types of Impact Attenuator having constructive similarity and symmetries are studied, made up of three different materials and different thicknesses of material. The behavior of the dummy was studied, considering a frontal collision of the car–dummy assembly, in accordance with existing standards. Using simulation software, the accelerations were determined at various points on the mannequin’s body and the force appearing on the seat belts was determined. The Gibbs–Appell equations are the method used to determine the dynamic response in this problem involving shocks

Stress–Strain Field in an Innovative Metallic Dam Gate Used to Control the Water Flow

The paper aims to determine the stress and strain field in metallic dam gates to identify an optimal constructive solution for their design, from the point of view of strength in service. The study is of a dam with a central, oscillating pivot, which has the role of closing the gates when the downstream water level becomes too high and can thus flood the upstream portion of the river. It starts from a constructive solution initially proposed by the designers, which is then modified in several steps, until a better solution is reached in terms of strength to mechanical stress. This solution is obtained after analyzing several structural scenarios. The final results ensure an excellent behavior of the mechanical stresses, and represent a constructive solution that is easy to achieve and is economically convenient

A Vibration Analysis of the Rubber Inertial Dampers Used in Electrical Vehicles

The development of electric vehicle manufacturing, which is considered a useful new popular propulsion system, has major design differences compared to conventional vehicles. This requires a reconsideration of the main components of vehicles and an analysis of them to determine the optimal design and solutions for the new models of cars. Among the many systems that need to be reconsidered is the suspension. A cheaper solution for reducing the car’s vibrations is suspension where the damping is ensured by elastic rubber elements, which are very simple, as they have significant structural damping and a much lower price than the classic solution. The main advantage of this solution is the simplicity. The paper presents and analyzes such an element, analyzing the vibrations of this element and the way in which inertial masses (metal spheres) inserted into the volume of the rubber influence the behavior of this element. The transmissibility of such an element, and how the number of balls and the level of structural damping influences this property, is also analyzed. The results suggest possible applications in the automotive industry

Modeling and Testing of the Sandwich Composite Manhole Cover Designed for Pedestrian Networks

This research concerning the topic, pursues the design, manufacturing, analysis and testing of the manhole cover that may be used in pedestrian networks. Although there are certain commercially available manhole covers made of glass-reinforced composites, there are a few papers published related to the modelling, simulation and mechanical testing of such parts. Herein, the manhole cover is made of the sandwich composite. The novelty of this kind of cover is to use an oriented strand board (OSB) as the core between two sides containing layers, which are reinforced with glass fibers. The OSB core leads to the increase of the stiffness-weight ratio. The paper describes the materials corresponding to the layers of the composite cover, geometry of the cover, technology used to manufacture the bending specimens and cover tested. Specimens made of materials that correspond to each layer of the cover, are tested in bending in order to determine their mechanical properties (flexural strength and flexural modulus). Bending tests and testing of the cover are also described. The composite manhole cover is also analysed by the finite element method to obtain the state of stresses and strains. The strains of the manhole cover are experimentally measured by using the tensometric method. Finally, comparing the strains with the strains experimentally measured validates the numerical simulation model

Effects of Seat Belts and Shock Absorbers on the Safety of Racing Car Drivers

This paper aimed to study the behavior of a body (dummy) that was in a race car in the event of a frontal collision with a wall in order to see what loads were acting on the dummy. Based on a complex car model, equipped with two safety system seat belts and a shock absorption system, the behavior of the dummy was obtained following frontal collision of the car–dummy assembly. The accelerations were obtained at different points of the dummy’s body and the force that appeared on the seat belts were determined. The Gibbs–Appell method was used to assess the response of the system based on the equations of motion in a problem involving shocks. This paper demonstrates that the revisited old principle of mechanics can offer an interesting and convenient means to obtain results in a short time. FEM and Altair Hyperworks software II was used to model the system. It can be used to determine whether a seat belt is able to work if it has defects during use, such as scratches, cigarette burns or animal bites

Effects of Seat Belts and Shock Absorbers on the Safety of Racing Car Drivers

This paper aimed to study the behavior of a body (dummy) that was in a race car in the event of a frontal collision with a wall in order to see what loads were acting on the dummy. Based on a complex car model, equipped with two safety system seat belts and a shock absorption system, the behavior of the dummy was obtained following frontal collision of the car–dummy assembly. The accelerations were obtained at different points of the dummy’s body and the force that appeared on the seat belts were determined. The Gibbs–Appell method was used to assess the response of the system based on the equations of motion in a problem involving shocks. This paper demonstrates that the revisited old principle of mechanics can offer an interesting and convenient means to obtain results in a short time. FEM and Altair Hyperworks software II was used to model the system. It can be used to determine whether a seat belt is able to work if it has defects during use, such as scratches, cigarette burns or animal bites

Calculation of Homogenized Mechanical Coefficients of Fiber-Reinforced Composite Using Finite Element Method

Determining the mechanical properties of a composite material represents an important stage in its design and is generally a complicated operation. These values are influenced by the topology and geometry of the resulting composite and the values of the elastic constants of the components. Due to the importance of this subject and the increasing use of composite materials, different calculation methods have been developed over the last fifty years. Some of the methods are theoretical, with results that are difficult to apply in practice due to difficulties related to numerical calculation. In the current paper, using theoretical results offered by the homogenization theory, values of engineering elastic constants are obtained. The finite element method (FEM) is used to determine the stress and strain field required in these calculations; this is an extremely powerful and verified calculation tool for the case of a material with any type of structure and geometry. In order to minimize errors, the paper proposes the method of least squares, a mathematical method that provides the best estimate for the set of values obtained by calculating FEM. It is useful to consider as many load cases as possible to obtain the best estimates. The elastic constants for a transversely isotropic material (composite reinforced with cylindrical fibers) are thus determined for a real case

Design and Analysis of Inertial Platform Insulation of the ELI-NP Project of Laser and Gamma Beam Systems

All the installations, devices, and annexes within the laser and the gamma ray production system within the ELI-NP project from Magurele are installed on an inertial platform that weighs over 54,000 tons. The platform is made of concrete, is insulated from the outside environment, and is supported by spring batteries and shock absorbers. The flatness of this platform respects some very strict standards, and, taking into account the processes that take place on the platform, the transmission of the different trepidations of the environment to the inertial mass must be extremely low. For this reason, a static study and a vibration analysis of the platform, performed in this paper, are required. The static analysis verifies if the flatness of the platform can be observed in operating conditions, and the dynamic analysis verifies how excitations coming from the external environment can be transmitted to the measuring equipment. The finite element method is used both to determine the deformability of the concrete platform for different loads, placed at different points and to determine its eigenvalues and its eigenmodes of vibration. The obtained results are analyzed and constructive solutions are proposed to improve the realized system, through a judicious placement of the installations and the distribution of the masses on the platform