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1
Content available Application of two fracture models in impact simulations
Fras T., Roth C. C., Mohr D.
Bulletin of the Polish Academy of Sciences. Technical Sciences
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2020
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Vol. 68, nr 2
317--325
EN
The following discussion concerns modelling of fracture in steel plates during an impact test, in which both target and striker are manufactured from the same material, high-strength high-hardness armour steel – Mars® 300. The test conditions (3 mm thick targets, projectiles with different nose shapes at impact velocity lower than 400 m/s) result in severely damaged components, which results in an analysis of stress states showing material failure. Numerical analyses are performed using two material models: the Johnson-Cook approach, as traditionally used in impact simulations, accounting for the effect of stress triaxiality, strain rate and temperature and for comparison, a simulation by means of the stress triaxiality and Lode angle parameter-dependent Hosford-Coulomb model, also incorporating the effect of the strain rate on a fracture initiation. The aim of the study is to analyse the mechanisms of penetration and perforation observed in the armour steel plates and validation of the modelling approaches.
2
Content available Energy-Based Yield Condition for Orthotropic Materials Exhibiting Asymmetry of Elastic Range
Pęcherski R. B., Rusinek A., Fras T., Nowak M., Nowak Z.
Archives of Metallurgy and Materials
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2020
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Vol. 65, iss. 2
771--778
EN
The aim of the paper is to formulate physically well founded yield condition for initially anisotropic solids revealing the asymmetry of elastic range. The initial anisotropy occurs in material primarily due to thermo-mechanical pre-processing and plastic deformation during the manufacturing processes. Therefore, materials in the “as-received” state become usually anisotropic. After short account of the known limit criteria for anisotropic solids and discussion of mathematical preliminaries the energy-based criterion for orthotropic materials was formulated and confronted with experimental data and numerical predictions of other theories. Finally, possible simplifications are discussed and certain model of isotropic material with yield condition accounting for a correction of shear strength due to initial anisotropy is presented. The experimental verification is provided and the comparison with existing approach based on the transformed-tensor method is discussed.
3
Content available Influence of Add-On Perforated Plates on the Protective Performance of Light-Weight Armour Systems
Fras T., Faderl N.
Problemy Mechatroniki : uzbrojenie, lotnictwo, inżynieria bezpieczeństwa
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2018
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Vol. 9, Nr 1 (31)
31--48
EN
The presented experimental investigation, aimed at verification of defeat mechanisms against small-calibre projectiles, provided by 4-mm-thick perforated plates with different material- and geometrical properties, was performed. A regular pattern of punched holes in steel plates increases the possibility of asymmetrical contact between the plate and projectiles which may cause threat destabilization, rotation or fragmentation depending on the impact position. Three tested armour configurations comprise the super-bainitic high-hardness Pavise™ SBS 600P armour steel plates perforated by elongated holes of size 4 x 12 mm (the first configuration), the martensitic high-hardness Mars® 300P steel plates perforated by circular holes with a diameter of 5 mm (in the second configuration); and in the third configuration, the martensitic Mars® 300 plates perforated by oblong holes (4 x 10 mm) were used. The performed impact tests proved that the tested add-on plates assured high protection against the impact of 7.62 x 51 .308 Win P80 hard-core armour piercing (AP) projectiles. It was also observed that the plates caused similar mechanisms of bullet failure.
4
Content available Rubber and magnetorheological fluid applied as the interlayer in composite armours against high-velocity loadings
Fras T., Fras L. J., Faderl N.
Diagnostyka
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2017
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Vol. 18, No. 3
63--68
EN
Monolithic, homogenous ballistic shields consisting of a single thick, high-hardness and high-strength steel plate are rarely applied in modern combat vehicles. Currently, a popular armour concept is a multilayered shield since it is expected that the kinetic energy of a threat may be dissipated by transmission through materials with different properties and also by multiple interface reflections. Searching for a maximum ballistic protection at minimum weight inspires applications of various materials which complementary behaviour provides a high protective efficiency without excessive mass. The preliminary experimental investigation presented in the paper aimed to verify behaviour of two prototyped laminated armours under impacts of small-calibre projectiles (cal. 7.62). The main interest lied in impact properties of materials proposed as the intermediate layer. The first tested concept was a laminated steel armour with the 10 mm thick rubber interlayer. In the second armour, the intermediate layer consisted of a magnetorheological fluid.
5
Content available remote Description of the Yield State of Bioplastics on Examples of Starch-Based Plastics and PLA/PBAT Blends
Fras T., Nishida M., Rusinek A., Pęcherski R. B., Fukuda N.
Engineering Transactions
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2014
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Vol. 62, iss. 4
329–-354
EN
The present work concerns the description of the yield state of biodegradable materials. As examples, biodegradable polymers are chosen – cornpole CRP-M2, starch fatty acid ester, and PLA/PBAT, poly(lactic acid) (PLA) blended with poly(butylene adipate/terephthalate) (PBAT) [1, 2]. These biodegradable, plant-derived bioplastics are a promising alternative to petroleum-based plastics. To describe the onset of plasticity in the bioplastics under discussion, Burzyński ’s hypothesis of material effort has been applied [3, 4]. The applied criteria account for the strength differential effect and for the shear correction resulting from the difference between experimental and theoretical values obtained as a result of the Huber-Mises approach [5, 6]. In general, these properties of yield state are characteristic for polymers. The description of yield state for bioplastics is an issue that has hardly been investigated, which illustrates the novel nature of this paper where this topic is discussed.
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