The article analyses the influence of concentrated mechanical loads on the durability of roofing materials as a function of roof waterproofing. The authors compared the influence of concentrated static, dynamic and hail loads on water tightness of coverings made of flexible roofing materials, i.e. bitumen sheet with reinforcement, PVC sheet and EPDM sheet. Mentioned materials were tested on concrete substrates and on the surface of mineral wool.
PL
W artykule przeanalizowano wpływ skupionych obciążeń mechanicznych na trwałość pokryć dachowych, określoną w funkcji wodoszczelności. Autorzy porównali wpływ skupionych obciążeń statycznych, dynamicznych i działanie gradu na wodoszczelność pokryć dachowych wykonywanych z wyrobów rolowych, tj. z papy, folii PVC i folii EPDM. Wspomniane wyroby badano na podłożach betonowych i z wełny mineralnej.
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W artykule zaprezentowano wyniki badania odporności na uderzenie systemu ociepleń ETICS z wełną mineralną lamelową (TR80) oraz zwykłą (TR10). Okładzinę stanowiły płytki klinkierowe oraz płytki cięte z cegieł ceramicznych. Badania przeprowadzono po cyklach hydrotermicznych oraz zamrażania-rozmrażania. Zastosowano nowe podejście do badania odporności na uderzenie z użyciem ciał twardych i miękkich. Na podstawie uzyskanych wyników testowane rozwiązania sklasyfikowano w najwyższej I kategorii użytkowania. Nie zaobserwowano wpływu rodzaju materiału termoizolacyjnego ani rodzaju płytek okładzinowych na rozpatrywaną właściwość.
EN
The paper presents the results of the impact resistance tests of ETICS made with the use of lamella (TR80) and regular (TR10) mineral wool. The cladding was made of clinker tiles and tiles cut from ceramic bricks. The tests were carried out after hydro-thermal and freeze-thaw cycles. A new approach was used to test the impact resistance with the use of hard and soft bodies. Based on the results, the tested solutions were classified in the highest category I of use. No influence of the type of thermal insulation material or the type of cladding tiles on the considered property was observed.
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Studies have shown that rubberised concrete is a potential pavement material. Pavement materials are generally expected to possess concrete with high impact resistance, especially in regions where winter temperatures remain lower than the freezing point for long periods. However, knowledge about the performance of rubberised concrete on impact under low temperatures is still limited. In this study, experiments were conducted to evaluate the compressive strength, elasticity modulus, bending strength, and impact resistance of rubberised concrete at room temperature (20 °C) and at a sub-zero temperature (− 20 °C). Meanwhile, a new U-shaped specimen drop-weight test was performed as an impact test. The results indicated that although the impact toughness of both rubberised and plain concrete types decreased at low temperatures, rubber particles also had positive effects on concrete impact resistance at − 20 °C. In addition to macroscopic tests, mercury injection and molecular dynamics simulations were performed to understand the mechanism through which rubber particles improve the impact resistance of concrete at low temperatures. The pores that could not freeze accounted for 1.55% of the total pores in plain concrete; this value was 2.36% in concrete with a rubber particle density of 50 kg/m3. From the results of this study, we can conclude that the addition of rubber can change the distribution of water or ice in concrete pores, which leads to an improvement in the toughness of concrete at a low temperature (- 20 °C).
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In this study, the dynamic, compressive, and flexural behaviors of ultra-rapid-hardening mortar (URHM) containing 2% polyethylene fiber are investigated. The results confirm the robust strain-hardening behavior of URHM at an early age of 4 h. Its tensile strength, strain capacity, and g value at 4 h were found to be 7.3 MPa, 5.1%, and 297.5 kJ/m3, respectively. The compressive and flexural strength and toughness of URHM increased with the strain rate. A higher loading rate led to a greater increase in the strength; the rate sensitivity was higher during flexure compared to that during compression. The highest dynamic increase factor (DIF) of the compressive strength was 1.75 up to a strain rate of 115/s; the highest DIF of the flexural strength was 3.34 up to a strain rate of 96/s. Its deflection-hardening behavior was converted to deflection-softening behavior under impact loads having a potential energy of 392 J or greater. Furthermore, the greater potential energy led to a lower energy dissipation rate, and more energy remained in the system. The rate sensitivity of the URHM under compression was similar to that of other fiber-reinforced concretes; however, its flexural strength was less sensitive to the strain rate than that of the others.
When a truck impacts on a reinforced concrete (RC) column such as a bridge pier at a high velocity, a large reaction force would generate which would damage the truck, hurt the passengers and destroy the column. Lightweight foams with excellent energy absorbing performance are often used as safeguard constructions to resist impact. The impact behavior can be divided into soft and hard impact. In the case of soft impact, the impacted structure deformation is predominant. In the paper, metallic foam safeguarded RC square columns impacted by a rigid block are simulated using the ABAQUS code software, and the influential characteristic of foam density on the peak impact force and ultimate energy absorption is focused on. The simulated results indicate that the foam safeguard constructions play remarkable role on impact resistance. It is exciting that there appears almost an identical critical foam density corresponding to the minimum peak force and the ultimate energy absorption, which is of great significance for engineering design of this type of safeguard constructions to resist impact.
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The tungsten inert gas welded P91 steel welded joints were subjected to the two different type of heat treatments including the postweld direct tempering (PWDT) and re-austenitizing based tempering (PWNT) treatment. The microstructure of weld fusion and heat affected zone (HAZ) were characterized in different heat treatment conditions using optical microscope and scanning electron microscope. For as-welded joint, a great heterogeneity was observed in microstructure and mechanical properties across the weldments. The Charpy toughness of the as-welded joint was measured much lower than the minimum recommended value of 47 J and it was measured 8 ± 5 J. The PWHTs have found a beneficial effect in decreasing the microstructure heterogeneity across the welded joint and improving the mechanical properties. The PWDT resulted in a drastic improvement in the Charpy impact toughness of the welded joint and it was measured 59 ± 5 J which was higher than the minimum required value of 47 J but still inferior than the base metal. The δ ferrite still remained in overlap zone of the weld fusion zone. The PWNT treatment resulted in homogeneous microstructure and hardness variation across the welded joint in transverse direction and Charpy impact toughness (149 ± 6 J) exceeded than that achieved in base metal.
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W artykule omówiono metody badawcze stosowane podczas oceny odporności na uderzenie wybranych systemów elewacyjnych. Przedstawiono kryteria oceny bezpieczeństwa i przydatności użytkowej oraz zależność pomiędzy odpornością na uderzenia a miejscem stosowania elewacji.
EN
This article discusses the impact resistance test methods used in evaluating of different façade systems. The safety and usability criteria are also presented. The paper are presented relationship between impact resistance and the place of facade application.
W artykule przedstawiono wyniki badań odporności na uderzenia wybranych powłok polimerowych naniesionych na powierzchnie stalowe. Wybrano trzy podłoża stalowe o różnej grubości, na które nakładane były powłoki epoksydowe, poliestrowe i polietylenowe. Przeprowadzone badania wykazały istotny wpływ rodzaju powłoki oraz jej grubości, a także grubości podłoża stalowego na odporność na uderzenia.
EN
The article presents the results of the impact resistance of selected polymer coatings deposited on steel surfaces. Were selected three steel substrates of different thicknesses, which were applied epoxy, polyester and polyethylene. The study showed a significant effect of the type of coating and its thickness, and the thickness of the substrate steel on impact resistance.
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This study presents an alternative approach for the absorption of impact energy that uses the internal pressurization of structures in the framework of a crash-adaptive response. Numerical simulations were conducted on the axial impact of thin-walled tubular structures with circular cross-section that serves as an approximation to a front crash box of a motor vehicle.The main objective of this work consists in studying the effect of internal pressurization of tubular structures in a crashworthiness application, as well as the possibility to obtain a reduction in wall thickness thus improving weight efficiency. A numerical study is presented for an internal pressure of 20 bar and tubular structures of circular section and 1.14 mm thickness. Numerical simulations were performed by making use of the LS-DYNA explicit dynamics software, while considering for the material a stainless steel alloy that is a material with interest for crashworthiness applications and manufacturing requisites due to its balance between strength, ductility, and energy absorption. The results obtained allow the conclusion, that with respect to internal pressurization it is feasible to reduce the wall thickness and have an impact resistance identical to the original while improving overall efficiency.
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W artykule przedstawiono wyniki badań odporności na uderzenia wybranych powłok polimerowych naniesionych na powierzchnie stalowe. Podłoże stalowe przed nałożeniem powłok zostało poddane obróbce strumieniowo-ściernej elektrokorundem o różnej granulacji ziaren. Badaniom poddano powłoki otrzymane z poliuretanów i polimoczników. Przeprowadzone badania wykazały istotny wpływ parametrów chropowatości podłoża stalowego na przyczepność do blachy stalowej powłok poliuretanowych i polimocznikowych po uderzeniu.
EN
The paper presents the results of the impact resistance of selected polymer coatings deposited on steel surfaces. Steel substrates before covering with the coating has been subjected to abrasive blasting with corundum particles with characterized by the different particles diameter. The investigations of the polyurethane and polyureas coatings were performed. The study showed the influence of steel surface roughness parameters on the adhesion of polyurethane and polyurea coatings to steel sheet after impact.
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Laminaty epoksydowo-węglowe są nowoczesnymi materiałami konstrukcyjnymi stosowanymi przede wszystkim w technice lotniczej z uwagi na wysokie właściwości mechaniczne w odniesieniu do gęstości. W czasie eksploatacji poza własnościami wytrzymałościowymi duże znaczenie ma także odporność na udarowe uderzenia skupione (impact), w tym uderzenia udarowe przy niskich prędkościach. Przy dostatecznie niskich energiach następuje utrata spójności wewnątrz struktury w postaci delaminacji niewidocznych przy ocenie makroskopowej elementów. W pracy przedstawiono badanie odporności na uderzenia przy niskich energiach laminatów epoksydowo-węglowych o różnych układach włókien, wytworzonych metodą autoklawową z jednokierunkowej taśmy preimpregnowanej. Zastosowano energie uderzenia w zakresie 1,5-5 J. Wyznaczono wykres zmian siły w czasie uderzenia, siłę maksymalną oraz siłę inicjacji utraty spójności kompozytu. Ponadto wyznaczono obszar zniszczenia ultradźwiękową metodą echa. Zauważono, że układy jednokierunkowe charakteryzują się niską odpornością na uderzenia. Układy wielokierunkowe w mezo- i makro- skali cechują się odpornością na udarowe uderzenia skupione w zakresie zastosowanych energii, jednak często tracą wewnętrzną spójność poprzez powstawanie delaminacji. Ponadto wraz ze wzrostem energii uderzenia wzrasta obszar zniszczenia w laminatach epoksydowo-węglowych.
EN
Carbon-epoxy laminates are modern construction materials used primarily in aerospace due to high mechanical properties in relation to density. During operation, besides strength properties great importance has resistance to impact, including the low-velocity impact. With sufficiently low energies of impact loss of cohesion inside structure is created in the form of delaminations which are invisible in the macroscopic assessment of elements. The laminates response to low velocity impact of carbon-epoxy laminates using hemispherical tipped impactor (diameter 38.1 mm) were analyzed. Laminates with different layers configurations were manufactured by autoclave method with unidirectional prepreg tapes. Impact energies in the range 1.5-5 J were applied. Diagram of changes of force at the time were determined, maximum and also first crack initiation forces. Furthermore impact damage zone was designated with ultrasonic methods. It was noted that unidirectional layouts have no practical impact resistance. multidirectional systems in meso- and macro-scale is characterized by resistance to impact the energy used, but often lose their internal cohesion in the form of delaminations. Moreover, with increasing impact energy is increasing generated damage area.
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