Motorcyclist Protection Systems: Analysis of the Crash Test Tolerances of the European Technical Specification and the Spanish Standard

One of the most frequent and harmful kinds of motorcycle accidents is an impact against the post of the roadside barrier, so designers have developed some motorcyclist protection system (MPS) to reduce it. Some countries have developed a standard testing procedure, like the Spanish UNE-135900-2008 standard, identical to the CEN's recently approved Technical Specification (TS 1317-8). These standards specify the test procedure to obtain the behaviour of the MPS, but experimental tests have shown some dispersion of results for identical tests of the same barrier. There are some theories to explain this but the most reasonable is the influence of tolerances of some of the test variables in the final result like impact height, impact velocity, yaw angle, and mass. To analyze these theories, numerical analysis that can measure the independent influence of each parameter in the results has been used, using a correlated numerical model, a common and experimentally tested barrier, and an MPS. So, the results of this paper show how some parameters of impact significantly influence the behaviour of the system, changing impact severity, potential damage, and injuries. Therefore, the test tolerances do not guarantee repeatability and can accept systems too harmful for the same test conditions, so it will be necessary to reduce limit deviations of some impact variables

Simulation of Suspensions, Torsion Bars, and Fifth Wheel for Semitrailers Using Finite Elements

The objective of this paper is the simulation of some different types of elements for semitrailers, like the suspension, both mechanical with springs and pneumatic with a spring anddiapresses; other parts like the wheels, the torsion bars, the fifth wheel and the suspension of the tractor unit have also been simulated. Then, the numerical simplified FE model of these elements that allows simulating the real behavior of the suspension to apply adequately the boundary conditions of a heavy vehicle has been obtained for a structural simulation using numerical tools with a good accuracy of the local and global behavior of the vehicle

Mechanical properties and energy–absorption capabilities of thermoplastic sheet gyroid structures

The development of additive manufacturing and lattice structures has created opportunities for the development of lightweight impact–absorption structures that can overcome most constraints of previously used materials such as expanded polystyrene foams. However, for the successful application of such structures, the effects of their variables in their mechanical performance must be established. In this study, the mechanical properties and energy absorption of thermoplastic sheet gyroid structures were investigated and compared with the performance of current materials. Consequently, the specimens were tested after changing the main variables, i.e., cell size and volume fraction, of various thermoplastic materials such as acrylonitrile butadiene styrene, polylactic acid, thermoplastic polyurethane, and polyamide 12. Finally, they were tested in a quasi-static compression test and their deformation stages were photographed. The stress–strain curves of all materials changed after adopting the sheet gyroid structure, exhibiting three distinct regions: linear elastic, long collapse plateau, and densification that made them particularly applicable for energy absorption. Volume fraction affected the layer collapse. The elastic geometrical stiffness increased for higher volume fractions and smaller cells. In addition, the peak and plateau stresses increased at higher volume fractions, and while smaller cells were not directly affected. Additionally, the area under the curves increase with the volume fraction; hence, for most materials, specific energy absorption was larger for higher volume fractions. The constituent material properties contributed significantly to the structural behavior, exhibiting three primary deformation mechanisms, i.e., elastomeric, elastic–plastic, and elastic–brittle, resulting in a wide spectrum of properties for each application requirement. The comparison of the optimal properties with the expanded polystyrene demonstrated the ability of sheet gyroid structures to overcome most of its challenges, exhibiting a superior specific energy absorption, ability to withstand various impacts, letting air flow in its all axes, and being recyclable. Thus, sheet gyroid structures can be considered promising alternatives

Mechanical properties of diamond lattice structures based on main parameters and strain rate

The diamond triply periodic minimal surface structure has a high mechanical property–weight ratio. They can be modified by changing their internal parameters or the material. They are generated using the additive manufacturing (AM) that possibilities the use of various materials for generating zones with different mechanical properties or by modifying their internal parameters. However, the effects of internal parameters in the mechanical properties have not been defined in detail. Furthermore, the strain rate modifies these mechanical properties. In this study, the effects of the internal parameters and strain rate were evaluated and additionally, the failure mechanism of the structures

La diferenciación interna del terciario en el análisis de la funcionalidad de la ciudad.

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Characterization of cork and cork agglomerates under compressive loads by means of energy absorption diagrams

Cork and cork agglomerates could be suitable replacements for petroleum-based polymeric foams due to their similar internal structure of cells and grains. Additionally, cork products have a renewable origin and are recyclable. Despite these notable properties, few studies have analysed the mechanical properties, especially the specific properties, of these materials under compressive loads. Moreover, although efficiency, ideality, and energy-normalized stress diagrams are commonly used for polymeric foams and 3D-printed lattice structures, these types of diagrams are not yet applied to cork products. It must be highlighted that efficiency diagrams are plotted only against nonspecific properties so, this article proposes additionally the use of nonspecific properties to compare materials not only in terms of properties per unit volume instead but also in terms of properties per unit mass that is more suitable for certain applications in which the weight is crucial. The materials studied herein include three different white cork agglomerates, a brown cork agglomerate, a black cork agglomerate, natural cork, and expanded polystyrene foam, which are subjected to quasi-static compressive loads

A study on interlaminar behavior of carbon/epoxy laminated curved beams by use of acoustic emission

The interlaminar tensile strength of carbon/epoxy laminated curved beams with variable thickness and through-the-thickness tufted reinforcement is studied experimentally by means of a four-point-bending test in accordance with ASTM D6415. These tests are monitored by the acoustic emission (AE) technique in order to gain deeper knowledge of the delamination onset and post-failure behavior. The results show that AE technique has proven to perform well when identifying delamination onset and its evolution after failure. In addition to this, AE has demonstrated to be an appropriate tool to assess the manufacturing quality of the carbon/epoxy laminated curved-beam, once the right pattern has previously been established

Analysis of the capability of cork and cork agglomerates to absorb multiple compressive quasi-static loading cycles

Despite the higher specific mechanical properties and the lower density of polymeric foams, these materials present cumulative damage behaviour that implies in the second and successive impacts, their mechanical properties decrease drastically. However, cork and cork agglomerates have the ability to absorb multiple impacts so they could be a more suitable material in some products, such as bumpers and helmets. This article is focused on the study of five different cork agglomerates and a natural cork under four different maximum deformations subjected to four consecutive compression loading cycles. Main diagrams, such as the stress–strain, energy density and efficiency, and the variation in diverse parameters, such as the absorbed energy density and maximum efficiency, were investigated and compared with an expanded polystyrene foam

Comparative analysis of mechanical properties and energy absorption capabilities of functionally graded and non-graded thermoplastic sheet gyroid structures

Additive manufacturing allows the tailoring of the structure of energy-absorbing materials. It is thus feasible now to use light, printed structures instead of other materials such as foams and honeycombs, signifying greater possibilities for customization. Some of these structures are triply periodic minimal-surface structures that is a family of different structures like the gyroid one. Another benefit of additively manufactured graded structures, which foams or honeycombs lack, is the flexibility to vary the internal parameters along one or more directions. This study focuses on the comparative analysis of graded and non-graded gyroid structures for four common thermoplastic materials used in additive manufacturing. These structures are compared with each other under quasi-static compression testing, as well as with expanded polystyrene foam and solid samples of the thermoplastic materials. The analysis includes investigation of the stress–strain and specific stress–strain curves, capability of absorbing energy per unit weight and per unit volume, ideality, total efficiency, and normalized energy vs. normalized stress characteristics. We also analyze the internal fracture mechanism of the structures. The objective is to obtain more extensive knowledge of the behavior of non-graded structures

Enhanced cohesive zone model to predict delamination behavior of carbon/epoxy laminated curved beams

This paper proposes an enhanced Cohesive Zone Model (CZM) for the prediction of delamination in curved beams of epoxy carbon laminates. This model improves the conventional CZM, taking into account the fiber-bridging phenomenon and the variation of the element size among the thickness in the curved zone. The advantages of the enhanced model are underlined when results obtained from the numerical simulations of a four-point-bending test in compliance with ASTM D6415 standard are compared with the corresponding experimental results. The prediction of the post-failure behavior obtained with this model is closer to that obtained experimentally than with the conventional model