Resumo em Inglês:

Abstract This paper aims at investigating the failure response of expanded metal meshes subject to transversal impact. Firstly, the study is performed through explicit nonlinear finite element analysis, in which a numerical model is developed to determine the impact performance and failure mode of expanded metal meshes. Thereafter, the effect of expanded metal cell geometries, impact mass and velocity on the structural response of the meshes is analyzed. Then the perforation resistance of the impacted meshes is assessed and analyzed by means of vulnerability curves for various expanded metal geometries subject to transversal impact. The extent of damage in the meshes is also evaluated, and the maximum displacements achieved in each impact scenario is quantified. At the end, it is demonstrated that the perforation performance of the meshes depends on the expanded metal cell dimensions expressed as a combination of the strand cross-section and major axis length. Finally, the results also show the feasibility of using expanded metal meshes to protect structures impacted by flying debris.

Resumo em Inglês:

Abstract The fragmentation effect of PELE refers to the fragmentation of the jacket after PELE penetrates the metal target plate. Three sets of 30CrMnSiA tensile samples with different hardness were pulled to obtain the corresponding maximum principal tensile stress and fracture strain of the material. It was found that the greater the hardness, the smaller the fracture strain, and the more easily to shear failure; Then, PELE penetration metal thin target fragment recovery test was carried out. It was found that only HRC50 jacket had compression shear and other brittle material damage characteristics and produced ideal fragmentation effect during penetration; The results show that the greater the target velocity is, the greater the critical value of its own material breaking is. When its own breaking strain is less than the critical value, the jacket can play a fragmentation effect; For PELE penetrator with the same material performance that meet the crushing conditions, the greater the impact velocity, the more the number of jacket fragments and the larger the distribution radius of fragments.

Resumo em Inglês:

Abstract Tires are a critical component of military wheeled vehicles and are exposed to the threat of fragment caused by explosion of warhead on the battlefield. To study the ballistic impact response of military vehicle tires under fragment, experiments and numerical simulations of spherical fragments impacting tires were carried out. The damage mode of the tires was analyzed. The effects of obliquity, tire thickness, and fragment mass on the dynamic response of tires, as well as the ballistic limit velocity, were analyzed. The results indicate that: (1) The main failure modes of the tire comprise local erosion near the center of the perforation, elastic deformation surrounding the perforation, and tensile fracture of the steel cords. (2) The process of fragment penetration into a tire can be divided into four stages: the entry stage, stable penetration stage, cord layer penetration stage, and fragment exit stage. (3) The cord structure demonstrates its ability to undergo plastic deformation to a certain extent and its restraining effect on the rubber.

Resumo em Inglês:

Abstract Reinforced concrete pipes are usually designed to attend a three-edged-bearing test (TEBT) using the partial safety factors from building structures. This study presents an alternative approach to designing RC pipes based on simplified reliability analyses. The procedure consists of providing curves of failure probability according to the reinforcement areas used in the pipes. The results indicate that RC pipes with simple reinforcement show a failure probability of around 1% with the most traditional design method, even using the partial safety factors from buildings, due to the higher dispersion of the concrete cover and the use of a single reinforcement layer to satisfy different control sections. Meanwhile, RC pipes with double reinforcement show a significantly lower failure probability as each reinforcement layer is designed to satisfy the bending moments from different control sections and due to the larger pipe thickness. In summary, the large randomness of the reinforcement position increases the failure probability of these members compared to traditional building structures.