Experimental Aircraft Fuel Tank Vapour/Air Explosions Using Jet A and Jet A / Gasoline Blend Fuels

The potential of a fuel tank explosion is a well-known hazard in the aircraft industry. In this study, an investigation of a lab scale aircraft fuel tank in a flight situation at varying initial pressures of 400 - 1,000 mbar (equivalent to altitudes of 0 - 22,300 ft) and at variable temperatures was conducted in a 100-litre cylindrical test rig. A standard Jet A fuel and with a type Jet B fuel (which in this case was a Jet A with 10% of gasoline by mass) were used. Their flashpoints were measured to be 45oC (Jet A) and 20 oC (Jet B). In the simulated fuel tank explosions ignition occurred when the fuel liquid temperature was much higher than the flash point - 71 – 107 oC depending on initial pressure (altitude) for Jet A and 57 – 95 oC for the more volatile Jet B. The resulting maximum explosion overpressures were high, ranging from 0.7 to 5.8 bar, much higher than typical design strengths of aircraft fuel tanks, and much stronger than anticipated overpressures on the basis of ignition at or close to the lower flammability limit (LFL). It is postulated that these pressures are due to the distance between the liquid fuel surface and the ignition point and the formation of a vapour cloud with decreasing concentration with height above the fuel (being at LFL at the ignition point) and hence an overall concentration much higher than LFL. This demonstrated that severe explosions are fuel tanks are likely and the assumption that the explosion will be a near lean limit event is not safe. The work also provided explosion severity index data which can be used in design of suppression and venting systems for the mitigation of aircraft fuel tank explosions and provided other quantitative data to help manage this explosion risk appropriately.

Pengaruh Waktu Pencampuran terhadap Kekerasan Vickers Material Crucible Berbahan Limbah Evaporation Boats, Kaolin dan Semen Tahan Api

Evaporation boat waste contains Boron Nitride (BN) and Titanium Diboride (TiB2) so that it has electrically conductive properties with high resistance to chemicals and heat. In addition, the combination of these materials has high thermal conductivity properties with a melting point of up to 2700oC and has an oxidation resistance of up to 1000oC so it is very suitable if applied to crucibles, or refractory. The purpose of this study was to determine the effect of mixing duration on the hardness of the crucible material made from a mixture of evaporation boats waste, kaolin and fire mortar SK-34. The mixing process of evaporation boats waste, kaolin and refractory cement is carried out using a mixer machine with a duration of 30, 60 and 90 minutes. The compaction process was carried out on the mixture with a force of 40 kg/cm2 to produce a cylindrical test specimen. After seven days, the specimens were sintered at 1000oC for 2 hours. The hardness test process was carried out with the FM-800 microhardness tester machine to determine the effect of mixing duration on the final product hardness. The highest hardness of 37,2 HV was found in the final product with a mixing duration of 90 minutes. The hardness of final product is increasing with an increase in mixing duration.

METHODS FOR REDUCING THE STRESS CONCENTRATION IN CYLINDRICAL SPECIMENS, AT AXIAL LOADING

The article presents specialized software methods for reducing stress concentration. Objects of study are cylindrical test specimens subjected to axial loading. Notching with different shapes and sizes on the specimens were formed to reduce the stresses in the endangered areas. The geometric parameters of notches identified through the specialized built-in modules to the ANSYS software. An analysis performed were to show the influence of stresses acting on the fatigue limit during different cycles. The results of the study were present in a graphical form.

Estudio comparativo de resistencias a la compresión en hormigones de 24 Mpa empleando agregados finos procedente de los ríos de Manabí

Las arenas de río son materiales empleados para las construcciones de viviendas y demás obras pequeñas que se realizan en los sectores alejados de las canteras, pero a su vez están cerca de meandros de ríos para su extracción y empleo. Por el uso que se da a este material, se creyó necesario realizar los ensayos físicos y mecánicos que tiene las arenas de varios ríos de la provincia de Manabí, exclusivamente los que atraviesan los cantones de Paján, Calceta y Olmedo, para posterior a ello realizar las dosificaciones del hormigón según los establece la ACI 211.1 y las normativas ecuatorianas, se realizaron probetas cilíndricas que permaneciendo en curado húmedo por un tiempo de 28 días, para realizar el ensayo de resistencia a la compresión, también se realizó el ensayo de resistividad superficial según lo establece la ASTM C1 202, 2012, para correlacionar los datos y establecer los usos apropiados de las arenas de los ríos en mención, Finalmente se obtuvieron los datos de los ensayos determinando que las arenas de los ríos mencionados no cumplen con las condiciones para su uso en obras que requieran hormigón de tipo estructural. Palabras claves: Arena de río, resistencia a la compresión, resistividad superficial. Abstract River sands are materials used for the construction of houses and other small works that are carried out in sectors far from the quarries, but in turn are close to meandering rivers for their extraction and use. Due to the use that is given to this material, it was believed necessary to carry out the physical and mechanical tests that the sands of several rivers in the province of Manabí have, exclusively those that cross the cantons of Paján, Calceta and Olmedo, to later carry out the concrete dosages as established by ACI 211.1 and the Ecuadorian regulations, cylindrical test tubes were made that, remaining in wet curing for a time of 28 days, to carry out the compression resistance test, the surface resistivity test was also carried out according to It is established by ASTM C1 202, 2012, to correlate the data and establish the appropriate uses of the sands of the rivers in question.Finally, the data of the tests were obtained determining that the sands of the mentioned rivers do not meet the conditions for their use in works that require structural concrete. Keys Words; River sand, compressive strength, surface resistivity

Modeling and Numerical Simulation of the Effect of Temperature on the LCF Behaviour of a CuCrZr Alloy Specimen

The main originality of this work consists in investigating low cycle fatigue of cylindrical test piece with wings under imposed constraint and for the temperature 20°c, 200°c, 400°c. Based on a combination between the fatigue parameter of Jiang-Sehitoglu and the relationship of Coffin-Manson, a numerical model for the prediction of the number of cycles at break. It was found that the CuCrZr cylindrical test piece showed a reduction in fatigue life with increasing temperature.

STUDI PENAMBAHAN SUPEPRPLASTCIZER PADA KUAT TEAN BETON DENGAN VARIASI FAS 0,4 – 0,5 MENGGUNAKAN AGREGAT KASAR YANG DI PECAH (SPLIT)

This study aims to determine the effect of superplasticizer usage on concrete compressivestrenght with variation of water cement ratio using subdivided crude aggregates (split).This research cylindrical test object with diameter 15 cm and height 30 cm. Compressivestrength concrete design fc’ 35 MPa, with variation of water cement ratio W/C 0,4; 0,45; 0,5 andusing Superplasticizer Sikament LN materials 0,5% of the weight of cement and slump value 12 ± 2cm.The result of research showed an increase the value of concrete compressive strength withthe addition of superplasticizer. The average of concrete compressive strength without the addition ofsuperplasticizer and variation of water cement ratio W/C 0,4; 0,45; 0,5 at 28 days in a row is 36,14MPa, 34,73 MPa, 29,82 MPa. While the value of concrete compressive strength with the addition ofsuperplasticizer increase to 39,73 MPa, 37,18 MPa, 31,23 MPa.

SIMULATION AND EXPERIMENTAL INVESTIGATION OF WRINKLE DEFECT IN DEEP DRAWING PROCESS OF CARBON STEEL SPCC SHAPED CYLINDER FLANGE CUP

A Sheet Metal Forming (SMF) process, especially deep drawing, is one of the manufacturing processes that commonly used in the automotive industry. Compared with casting and forging, the SMF process has several advantages, including lesser weight materials and broader variations in shape that can be made. One of the problems in the SMF process is the wrinkling phenomenon, which can cause the size and appearance defects of sheet products. The wrinkle occurs because of the mechanical properties of the material, product geometry, and blank holder force (BHF). Several variations of BHF were applied in these simulations and experiments to eliminate the wrinkle defects of cylinder flange cup test products. The characteristic of the cylinder flange cup is from the cold-rolled coiled steel plate (SPCC) type of material with a thickness of 0.8 and 1.0 mm, the height of 10 mm, the inner diameter of 58 mm, and flange diameter of 76 mm. Simple simulations of the SMF process were carried out by using Solidworks with version 2017, and the experiment was carried out at a 600 kN press with a punch velocity of 40 strokes per minute and blank holder force variations from 0 to 21 kN. The experimental data performed with a single die on a flanged cup cylindrical test material shows that the higher the blank holder force (BHF) number, the smaller the wrinkle defect, and it can be eliminated starting from the BHF number of 15 kN.

CONCRETO PRODUZIDO COM AGREGADO GRAÚDO LATERÍTICO EM SANTARÉM, PARÁ

RESUMO: Avaliou-se a substituição da brita basáltica existente no concreto por material alternativo em abundância no município de Santarém-PA: a laterita. Foi avaliado o desempenho do concreto incorporado com agregado laterítico in natura em substituição parcial ao agregado graúdo de brita basáltica nos teores de 20% e 50%. Realizou-se a caracterização dos agregados graúdo e miúdo. De acordo com o método da ABCP, determinou-se o traço de referência em massa 1:1,71:3,03:0,53; confeccionou-se corpos-de-prova cilíndricos 10x20 cm utilizando 3 traços diferentes, de modo a substituir a brita basáltica pelo agregado laterítico, em 20% e 50%. Para cada traço foram quantificados a sua consistência, por meio do ensaio de abatimento do tronco de cone, resistência à compressão axial, resistência à tração por compressão diametral e módulo de elasticidade aos 28 dias. A substituição do agregado convencional de brita basáltica por agregado laterítico em seu estado natural promoveu diminuição da resistência a compressão simples, da resistência à tração por compressão diametral e do módulo de elasticidade com a inclusão do agregado laterítico na mistura. Destaca-se que acima de determinado teor de substituição o concreto torna-se inviável devido a necessidade de adicionar aditivo plastificante para manter a consistência desejada e que as duas misturas incorporadas com agregado laterítico se mostraram muito semelhantes após os 28 dias, no que tange a ganhos de resistência a compressão. ABSTRACT: This study is about the replacement of basaltic origin crushed stone by alternative material present in the municipality of Santarém, Pará State: the laterite. The aim were to evaluate the performance of concrete incorporated with natural lateritic aggregate, replacing the of crushed stone in 20% and 50%. The first stage was characterizing the coarse and fine aggregates that made up the studied concrete. According to ABCP dosing method it was determined the mass reference trait 1: 1.71: 3.03: 0.53; bodies of 10x20 cm were made for cylindrical test, using three different strokes so that the basaltic crushed stone gradually replaced by the lateritic aggregate in proportions of 20% and 50%. For each trait its consistency was quantified by means of the tapering test, axial compression strength, diametric compression tensile strength and the modulus of elasticity at 28 days. Was observed that the replacement of the conventional aggregate basalt crushed stone for aggregate of laterite in natural state promoted a decrease in the value of simple compressive strength, diametric tensile strength and modulus of elasticity with inclusion of a larger amount of lateritic aggregate in the mixture. It is noteworthy that above a certain substitution content, the concrete becomes not feasible due to the need for a large increase in the amount of plasticizer additive to the desired consistency is maintained and the two blends incorporated with lateritic showed very similar after 28 days in terms of gains in compressive strength.

Factors influencing ultrasonic pulse velocity in concrete

The hydration process of Portland cement triggers reactions of stabilization of minerals from the contact of the clinker with water, which is the Hydrated Calcium Silicate (C-S-H), the Etringite (3CaO.Al2O3.3CaSO4.32H2O) and the Portlandite (Ca(OH)2). In order to understand the effects of the evolution of hydration in cement, it is possible to apply non-destructive tests. In this context, the objective of this work is to evaluate the influence of the type of cement, the curing age, of the format and humidity of the test specimens of concrete in the ultrasonic pulse velocity (UPV). In order to do that, 36 cylindrical test specimens (10 x 20 cm) and 9 cubic ones with 25 cm of edges, with mix proportion of 1:2,7:3,2 (cement/sand/gravel), water/cement ratio of 0.58 and three types of Portland cement (CP II-Z-32, CP IV-32 RS and CP V-ARI) were molded. With data obtained it was possible to correlate the increase of concrete strength along time (at ages of 7, 14, 28, 70 and 91 days) with the increase of the ultrasonic pulse velocity. Besides, it was possible to prove the direct influence of the concrete moisture and of the degree of hydration in the UPV. The shape of the test specimen generally had no influence on the results, except in the case of cement CP V ARI.