Piotr Kędzierski - Academia.edu (original) (raw)

Papers by Piotr Kędzierski

Composite Structures, Jul 1, 2022

$Research paper thumbnail of Comparative fracturing of marble samples with fluids of different viscosity$

IM Inżynieria Materiałowa, Feb 5, 2017

Renewable Energy, Jul 1, 2016

The objective of this study is to determine the depth characteristic of a heat transfer coefficie... more The objective of this study is to determine the depth characteristic of a heat transfer coefficient in the wellbore heat exchanger with the use of the original calculation procedure called an internal functions method. During the geothermal heat recovery, the substances change their pressure and temperature together with current (local) depth of the wellbore. Together with a change of these thermophysical parameters, there are also changes in the substance thermophysical properties, i.e.: specific heat, heat conductivity, density and viscosity. These properties decide on Prandtl Pr and Reynolds Re criterion numbers. These numbers, in connection with Nusselt number, enable to determine the local values of the heat transfer coefficient. The values of thermophysical properties and a heat transfer coefficient, assumed in the calculation models of the geothermal heat recovery, usually have a decisive influence on the reliability of the obtained results.

Composites Part B-engineering, 2015

This paper presents experimental and numerical research regarding blunt trauma resistance of ten ... more This paper presents experimental and numerical research regarding blunt trauma resistance of ten fabrics made of high strength fibers. Fabrics of various architecture were examined, including plain woven fabrics, unidirectional laminates and multiaxial fabrics. The fabrics were compared with respect to the depth of the depression formed and the amount of energy transferred to the backing during projectile impact. Absolute values of mentioned parameters were compared, as well as their values after normalization with respect to thickness and areal density of the fabrics. A numerical method for estimating the amount of energy transferred to the backing was proposed. Normalized results, obtained experimentally and numerically, proved that most of the analyzed fabrics provide a similar level of protection, but the best blunt trauma resistance is given by multiaxial fabrics and the least by plain woven fabrics. This study has also shown that the depth of the depression in the backing mate...

Archives of Civil Engineering, 2017

Hydraulic fracturing of rocks boosts the production rate by increasing the fracture-face surface ... more Hydraulic fracturing of rocks boosts the production rate by increasing the fracture-face surface area through the use of a pressurized liquid. Complex stress distribution and magnitude are the main factors that hinder the use of information gathered from in situ hydraulic fracturing in other locations. Laboratory tests are a good method for precisely determining the characteristics of these processes. One of the most important parameters is breakdown pressure, defined as the wellbore pressure necessary to induce a hydraulic fracture. Therefore, the main purpose of this investigation is to verify fracture resistance of rock samples fractured with the assistance of the most popular industry fluids. The experiments were carried out using a stand designed specifically for laboratory hydraulic fracturing. Repeatable results with a relative error within the range of 6-11% prove that the experimental methodology was correct. Moreover, the obtained results show that fracturing pressure depe...

Mechanics of Composite Materials, 2016

The optimization process for a composite panel with an Al 2 O 3-AA2024 percolation phase subjecte... more The optimization process for a composite panel with an Al 2 O 3-AA2024 percolation phase subjected to a perpendicular impact of a 7.62 × 54R B32 Armor Piercing projectile is described. It is found that metal-matrix composite/ceramic-matrix composite structures have a lower ballistic resistance than structures in which a hard layer supported by a plastic one. Optimization revealed that the best composite panel with an Al 2 O 3-AA2024 percolation phase could be obtained when the probability distribution of individual materials was described by a highly nonlinear function.

Renewable Energy, 2016

Archive of Mechanical Engineering, 2015

The aim of the study is to identify the relevant aspects of numerical analysis of impact of proje... more The aim of the study is to identify the relevant aspects of numerical analysis of impact of projectiles with soft cores into a package composed of thin flexible plies located on the plastic backing. In order to illustrate the problem, normal impact of 7.62 mm TT projectile into an unclamped package comprising 36 plies of Dyneema SB71 supported on the plastic backing was selected. The problem was solved with the use of the finite element method (FEM) with the explicit integration scheme (central difference method) of motion equations in the matrix form. Based on the conducted numerical computations, it was revealed that obtaining the extreme deformations of a projectile soft core and the backing material in Lagrangian description requires employment of adaptive methods. The proposed R-adaptive method performs its role but must be used carefully due to the mass loss which may appear during calculations.

Bulletin of the Military University of Technology, 2021

The paper presents an analysis of applicability of two meshless methods to the modeling of pistol... more The paper presents an analysis of applicability of two meshless methods to the modeling of pistol bullets on the example of a 9 mm Parabellum. The studies included the following methods: SPH and SPG. The results of computer simulations were confronted with ballistic test results in terms of shape-dimensional compliance of the deformed projectile. The relative error of the projectile diameter was 15 and 17% for the SPG and SPH methods, respectively. The deformation form for the SPH method deviated from the ballistic test results, while the SPG method faithfully reproduced the shape of the deformed projectile. Keywords: mechanical engineering, impact simulation, pistol bullet, SPH, SPG

Materials & Design, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

International Journal of Impact Engineering, 2019

The paper demonstrates the process of development of a bending device for a springback study. The... more The paper demonstrates the process of development of a bending device for a springback study. The numerical analysis of a V-bending device work as well as its optimization and experimental verification are presented. The study was conducted for the samples made of S235 structural steel. The main difference between the proposed device and a well-known device for V-bending lies in sample fastening to the punch head and a larger die radius in relation to the sample thickness. The presented bending device is characterized by a larger springback angle, less dispersion of the results and lack of the sample reverse loading.

The work concerns the numerical analysis of the impact of the shock wave caused by the detonation... more The work concerns the numerical analysis of the impact of the shock wave caused by the detonation of the high explosive charge with the elements constituting the protective structure. The tests were carried out using the shock tube system and the LS-DYNA dynamic analysis software. The obtained results indicated the occurrence of a number of interesting effects and physical phenomena in the case of testing the heterogeneous protective systems containing elements in the form of spherical inclusions.

Composite Structures, 2016

Abstract This paper presents studies on perforation and trauma resistance of hybrid soft structur... more Abstract This paper presents studies on perforation and trauma resistance of hybrid soft structures. A selection of hybrid configurations were tested experimentally with a 7.62 × 25 mm Tokarev projectile. Hybrid packages included a wide range of textiles used for personal protection from laminates through plain-woven and multiaxial fabrics to felt. Their effectiveness was evaluated by reference to homogenous packages. The conducted examination demonstrated that hybrid packages employing stiff anti-trauma liners can reduce backface deformation by about 10% compared to homogenous packages. However, too many stiff layers deteriorates perforation resistance by shortening the distance in which a projectile is arrested. Utilization of felt material has a positive effect on trauma and perforation resistance. Soft layers with substantial thickness decrease impulse force and allow projectiles to be stopped over a longer distance. Hybrid packages with felt material have one major drawback in that they are a few times thicker than the other structures tested. An optimal compromise between ballistic performance and thickness is provided by panels based on unidirectional laminates combined with felt and stiff anti-trauma layers. Coupling of plain woven fabric and unidirectional laminate was found to be less efficient than packages entirely made of unidirectional laminate.

Solid State Phenomena, 2015

The paper presents a description of the stand for rock material fracturing in laboratory conditio... more The paper presents a description of the stand for rock material fracturing in laboratory conditions. Requirements to be met by fracturing stands were formulated. Proper operation of the test stand was verified by marble sample fracturing. Many of technical details of the developed stand were given, which may be useful for readers designing their own stands.

Bulletin of the Polish Academy of Sciences Technical Sciences, 2015

The main goal of this numerical and experimental study of composite armour systems was to investi... more The main goal of this numerical and experimental study of composite armour systems was to investigate their ballistic behaviour. Numerical simulations were employed to determine the initial dimensions of panel layers before the actual ballistic test. In order to achieve this aim, multivariate computations with different thicknesses of panel layers were conducted. Numerical calculations were performed with the finite element method in the LS-DYNA software, which is a commonly used tool for solving problems associated with shock wave propagation, blasts and impacts. An axisymmetric model was built in order to ensure sufficient discretization. Results of a simulation study allowed thicknesses of layers ensuring assumed level of protection to be determined.According to the simulation results two armour configurations with different ceramics have been fabricated. The composite armour systems consisted of the front layer made of Al