Experimental and Numerical Modeling of the Extrusion Process in 1050A Aluminum Alloy for Design of Impact Energy-Absorbing Devices

The results obtained experimentally with the use of Hopkinson bar and numerical results on backward extrusion of 1050A aluminum at 10 m/s tool speed are presented, in order to assess the extrusion technology applied in the design of energy-absorbing devices. The devices of this type should satisfy the requirements, particularly, constant force versus displacement of the piston and the amount of the energy absorbed by the object. Numerical analyses of three variants of the absorbing device geometry were presented. The obtained results allowed an appropriate selection of geometric parameters of the device, and, as a result, the requirement of the proper amount of absorbed energy was satisfied

Dynamic Testing of Reinforced Glass Fibre-Epoxy Composite at Elevated Temperatures

We present the experimental analysis of the deformation, strength and failure of tubular speciImens, made of woven reinforced glass fibre-epoxy composite. These specimens were subjected to uniaxial tensile testing with the average strain rates of about 10 ^-5 and up to 20 с ^-1 . Tests were performed at room and three elevated temperatures, up to the temperature corresponding to the phase change of the matrix.Проведено експериментальний аналіз деформування, міцності і руйнування трубчастих зразків, виготовлених із армованого скловолокном епоксидного композита. Зразки випробовували на одновісний розтяг при середній швидкості деформації від 10 ^-5 до 20 c ^-1. Випробування проводили за кімнатної температури, а також за трьох підвищених до моменту фазового перетворення матриці.Представлен экспериментальный анализ деформирования, прочности и разрушения трубчатых образцов, изготовленных из армированного стекловолокном эпоксидного композита. Образцы подвергались одноосному растяжению при средних скоростях деформации от 10^-5 до 20 с^-1. Испытания проводились при комнатной температуре, а также при трех повышенных температурах до момента фазового превращения матрицы

Fatigue strength investigation of bonded joints

Numerous advantages of the bonded joints result in wide application in the aircraft, motor industry or powertrain components. These types of joints enable joining materials with different mechanical properties (e.g. Stiffness) and dimensions without structure change. Proper joint design limits the field of local stress concentrations or even eliminates them. The structural integrity of complete structure depends on the fatigue estimation of the bonded joint. Application of the finite element method to life prediction of the double lap bonded joint metal-composite-metal is presented. Three dimensional numerical models are generated by professional engineering software tools. The contact problem is modelled between the epoxy resin and metal and composite surfaces. A laminated composite consists of the epoxy woven carbon prepreg. Elasto-plastic materials models of the adhesion and metal and orthotropy composite model allowed determining the contact normal stress in the interfaces in each deformation increment which is induced by an external load. MSC.Marc was used to determine the strain and stress distribution in the double lap bonded joint including contact normal stress in the steel/adhesive and laminated composite/adhesive interfaces. Two numerical models of the double lap bonded joint were compared. The use of the presented method is more suitable for structure optimisation than numerical analysis

Security improvement for oil and gas pipeline infrastructure

This research has been inspired by security concerns due to the recent increase in the terrorist threat to gas and crude oil transportation around the world, especially in regions that are of significant value for the energy supplies. Computational mechanics methods will be used in this research to apply shock wave analysis for possible damage assessment of the affected pipelines. These methods may be also used for pipelines at power plants (especially nuclear), which are usually placed high on the homeland security priority list. The main goal of this research is focused on establishing effective simulation methodology to study the influence of shock waves (caused by explosion) on pipeline systems (buried, on surface, or underwater) to ensure their security. This study is primarily focused on the behaviour of a pipeline subjected to the shock wave produced by the detonation of highly explosive (HE) materials. The results of this study will primarily allow for analysis of the blast wave propagation and the resulting damage inflicted by the pipeline. Outcomes of this research are important in preventing damage progression of pipelines under the blast loading. This data will also be used to develop improved design guidelines for safer and less vulnerable pipelines. The study allows for determining a type of structure of the high energy absorbing protective system

Carbon - epoxy composite fatigue strength - experiment and fem numerical estimation

The development of composite materials characterized by the constant amelioration of their mechanical properties (stiffness and strength) has widened their application for structural elements, mainly in aeronautical, naval and automobile industries. The possibility of tailoring the composite’s properties appropriately to the applied load (by changing the direction of the fibre alignment and applying a corresponding matrix) results in the growing importance of the design process. The paper presents a numerical technique of determining the fatigue strength of the laminated carbon–epoxy composite. The experimental investigations were carried out to determine the complete set of the stiffness characteristics Eij, Gij, ..ij, the strength characteristics ..i,n, ..i,n. and the S-N fatigue curves. The static and fatigue numerical calculations were carried out for the material anisotropic model of the particular composite layers. Eight-node 3D finite elements with the composite’s properties were used to develop the specimen’s numerical model. The contact problem between the composite layers enabling the reflection of a mutual interaction was taken into account. The numerical investigation also included the state of effort analysis and the fatigue life assessment of the composite. The assessment of the composite’s fatigue life was performed using the MSC.Fatigue code. The verification of models and numerical analysis was carried out for composite specimens made of the CE 8201-245- 45/120 prepreg. The experimental verification confirmed that the places of the lowest fatigue life, found out in numerical analysis, are located in the area of the gauge part

Model reologiczny HWKK dla żywic

A rheological model for epoxy and polyester resins, denoted with the symbol HWKK, has been developed and positively validated for selected loading programmes. This model describes the first-rank reversible creep of amorphous tyermohardened polymers with good accuracy. The mechanical HWKK model consists of four elements connected in series, formulated by Hooke, Wilczyński and Kelvin. Constitutive equations of viscoelasticity for the HWKK model have been formulated, with fractional and normal exponential functions used as the generating ones. An algorithm for identification of the material constants, based on creep experiments of bar samples uniaxially tensioned, has been developed. The material constants have been identified for epoxy and polyester resins.Opracowano nowy model reologiczny żywicy epoksydowej i poliestrowej, oznaczony symbolem HWKK. Przeprowadzono walidację tego modelu dla wybranych programów obciążenia, uzyskując pozytywne wyniki. Model HWKK opisuje z dobrą dokładnośćią pełzanie pierwszorzędowe odwracalne polimerów amorficznych termoutwardzalnych. Model ten jest odwzorowany przez cztery elementy mechaniczne połączone szeregowo typu Hooke'a, Wilczyńskiego i Kelvina. Sformułowana równania konstytutywne lepkosprężystości i modelu HWKK stosując jako funkcje tworzące jedną funkcję wykładniczą ułamkową oraz dwie funkcje wykładnicze zwykłe. Opracowano algorytm identyfikacji stałych materiałowych opisujących model HWKK, bazujący na eksperymentach pełzania próbek prętowych rozciąganych osiowo. Stałe te zidentyfikowano dla żywicy epoksydowej i poliestrowej

Experimental investigation of deflector's angle influence on energy absorption

Numerical simulations without preliminary validation and model verification are vulnerable to errors. Best results are obtained when full experimental research is provided. Such tests are expensive and may be dangerous. Due to cost control and personnel safety, studies are often done in scale. Scale can affect both construction dimensions and applied load. In this paper four different vehicle's bottoms are examined: flat bottom and 3 types of deflectors. The paper presents four different vehicle's bottom shapes in order to examine deflector angle influence on energy absorption. The test included 4 cases: flat bottom broken-shaped deflector and deflectors with different apex angles 124 centigrade and 144 centigrade. For all cases the distance between explosive and panel was approximately 400 mm. The charge used was 100 g TNT. Flat bottom and deflectors were made of St3 steel with 2 mm thickness. For the purpose of the research a special test stand to examine effects of detonation wave was used. The force measurement system was designed in Department of Mechanics and Applied Computer Science. As a result, force versus time plots were obtained. The use of any deflector decreases maximum force affecting vehicle's hull

Adhesive Joints Testing of Ceramic and Anti-Ballistic Fabrics

W artykule przedstawiono wyniki badań połączeń adhezyjnych stosowanych w procesie wytwarzania kamizelek kuloodpornych. Połączenia przygotowano na bazie tkanin polietylenowych i aramidowych oraz płytek ceramicznych typu SiC i Al2O3. Do łączenia materiałów wykorzystano kleje przeznaczone do łączenia tworzyw polimerowych: BONDICX 01 CX-80, POXIPOL 10 min, LOCTITE 3038, Scotch-Weld 8010, Professional Silikon Czarny i Terostat M9399. Stwierdzono, że tkaniny polietylenowe HB50 ROLL 401184C i HB26 ROLL 401400B, ze względu na ich niską wytrzymałość międzywarstwową oraz brak podatności do przesycania, nie nadają się do adhezyjnego łączenia ich z płytkami ceramicznymi. Na podstawie badań zaproponowano również rodzaj próbek, które w dobry sposób odwzorowują w kamizelkach obciążenie płytek ceramicznych przyklejonych do tkanin. Badania przeprowadzone z wykorzystaniem takich próbek wykazały, że klej Bondicx 01 najbardziej nadaje się do takich zastosowań.The research results of adhesive joints used in the manufacture of bulletproof vests were presented. The joints were prepared on the basis of polyethylene and aramid fabrics and ceramic tiles of SiC and Al2O3 types. For joining the materials, the following adhesives dedicated to bonding polymeric materials were used: BONDICX 01 CX-80, Poxipol 10 min, LOCTITE 3038, Scotch-Weld 8010, Professional Silicone Black, and Terostat M9399. It was found that the polyethylene fabrics HB50 and HB26 401184C ROLL ROLL 401400B, due to their low interlaminar strength and lack of compliance to supersaturation, are not suitable for their adhesive bonding with the tiles. On the basis of research, the test specimens were proposed which in the best way represent the loading of ceramic tiles which are bonded to the fabric. Tests with using such specimens demonstrated that the adhesive BONDICX 01 is the best solution for such applications

Experimental and Analytical Research on Resonance Phenomena of Vibrating Head with MRE Regulating Element

A vibratory pile hammer (VPH) is a mechanical device used to drive steel piles as well as tube piles into soil to provide foundation support for buildings or other structures. In order to increase the stability and the efficiency of the VPH work in the over-resonance frequency, a new VPH construction was developed at the Military University of Technology. The new VPH contains a system of counter-rotating eccentric weights, powered by hydraulic motors, and designed in such a way that horizontal vibrations cancel out, while vertical vibrations are transmitted into the pile. This system is suspended in the static parts by the adaptive variable stiffness pillows based on a smart material, magnetorheological elastomer (MRE), whose rheological and mechanical properties can be reversibly and rapidly controlled by an external magnetic field. The work presented in the paper is a part of the modified VPH construction design process. It concerns the experimental research on the vibrations during the piling process and the analytical analyses of the gained signal. The results will be applied in the VPH control system

Numerical and experimental research on the influence of an obstacle on pressure distribution

W artykule przedstawiono wyniki badań nad modelowaniem układu wybuch-półsfera. Falę uderzeniową badano w sposób numeryczny i analityczny. W celu przeprowadzenia weryfikacji uzyskanych wyników wykonano stanowisko do badań eksperymentalnych.This paper deals with research results on the modeling of a blast wave and a half sphere configuration. Numerical and analytic methods were used to examine a blast wave. In order to verify the obtained results a stand for experimental tests was built