Search results for: adhesion tests

Authors: Mustafa Yildiz, Ali Sinan Soganci

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Pumice soils are countered in many projects such as transportation roads, channels and residential units throughout the World. The pumice deposits are characterized by the vesicular nature of their particles. When the pumice soils are evaluated considering the geotechnical viewpoint, they differ from silica sands in terms of physical and engineering characteristics. These differences are low grain strength, high friction angle, void ratio and compressibility. At stresses greater than a few hundred kPa, the stress-strain-strength behaviour of these soils is determined by particle crushing. Particle crushing leads to changes in the density and reduction in the components of shear stress due to expansion. In this study, the bearing capacity and behaviour of granular pumice soils compared to sand-gravels were investigated by laboratory model tests. Firstly the geotechnical properties of granular pumice soils were determined; then, the behaviour of pumice soils with an equivalent diameter of sand and gravel soils were investigated by model rectangular and circular foundation types and were compared with each other. For this purpose, basic types of model footing (15*15 cm, 20*20 cm, Φ=15 cm and Φ=20 cm) have been selected. When the experimental results of model bearing capacity are analyzed, the values of sand and gravel bearing capacity tests were found to be 1.0-1.5 times higher than the bearing capacity of pumice the same size. This fact has shown that sand and gravel have a higher bearing capacity than pumice of the similar particle sizes.

Keywords: pumice soils, laboratory model tests, bearing capacity, laboratory model tests, Nevşehir

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Authors: Bharat Kumar, Deepak Kumar, Vijay Chaudhry

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Zirconium alloys are widely used for the core components of a pressurized heavy water reactor (PHWR) or Canada deuterium (CANDU) reactor due to their low neutron absorption cross-section and excellent mechanical properties. The components made of Zirconium alloys are subjected to flow-induced vibrations, resulting in fretting wear at the interface of; pressure tubes and bearing pads, pressure tubes and calandria tubes, and calandria tubes and Liquid injection shutdown system (LISS) nozzles. There is a need to explore the tribological response under such conditions. Present work simulates the contact between calandria tube and LISS nozzle of PHWR/CANDU reactor as cylinder-on-cylinder contact configuration. Reciprocating tribo-tests were conducted on Zircaloy-4 (Zr-4) under the self-mated condition at varying amplitude, frequency, and sliding time. To understand the active wear mechanism, worn surfaces were analyzed using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The change in amplitude severely affects the wear than other factors. The wear mechanism transits from adhesion to abrasion with increasing test amplitude. The dominant wear mechanisms are micro-cutting and micro-plowing followed by delamination in some areas. However, the coefficient of friction has indifferent behaviors.

Keywords: zircaloy-4, tribology, calandria tube, LISS nozzle, PHWR

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Authors: R. Alias, A. Kasa, M. R. Taha

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The effect of particle size on shear strength of granular materials are investigated using direct shear tests. Small direct shear test (60 mm by 60 mm by 24 mm deep) were conducted for particles passing the sieves with opening size of 2.36 mm. Meanwhile, particles passing the standard 20 mm sieves were tested using large direct shear test (300 mm by 300 mm by 200 mm deep). The large direct shear tests and the small direct shear tests carried out using the same shearing rate of 0.09 mm/min and similar normal stresses of 100, 200, and 300 kPa. The results show that the peak and residual shear strength decreases as particle size increases.

Keywords: particle size, shear strength, granular material, direct shear test

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Authors: M. Tang, S. M. Wen, D. W. Liu

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This paper presents the influences on the entrainment of serpentines by grinding and reagents during copper–nickel sulfide flotation. The previous bench flotation tests were performed to extract the metallic values from the ore in Yunnan Mine, China and the relatively satisfied results with recoveries of 86.92% Cu, 54.92% Ni, and 74.73% Pt+Pd in the concentrate were harvested at their grades of 4.02%, 3.24% and 76.61 g/t, respectively. However, the content of MgO in the concentrate was still more than 19%. Micro-flotation tests were conducted with the objective of figuring out the influences on the entrainment of serpentines into the concentrate by particle size, flocculants or depressants and collectors, as well as visual observations in suspension by OLYMPUS camera. All the tests results pointed to the presences of both “entrapped-in” serpentines and its coating on the hydrophobic flocs resulted from strong collectors (combination of butyl xanthate, butyl ammonium dithophosphate, even after adding carboxymethyl cellulose as effective depressant. And fine grinding may escalate the entrainment of serpentines in the concentrate.

Keywords: serpentine, copper and nickel sulfides, flotation, entrainment

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Authors: Afsaneh Jasmine Majidi

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Language testing is an important part of language teaching experience and language learning process as it presents assessment strategies for teachers to evaluate the efficiency of teaching and for learners to examine their outcomes. However, language testing is demanding and challenging because it should provide the opportunity for proper and objective decision. In addition to all the efforts test designers put to design valid and reliable tests, there are some other determining factors which are even more complex and complicated. These factors affect the educational system, individuals, and society, and the impact of the tests vary according to the scope of the test. Seemingly, the impact of a simple classroom assessment is not the same as that of high stake tests such as International English Language Testing System (IELTS). As the importance of the test increases, it affects wider domain. Accordingly, the impacts of high stake tests are reflected not only in teaching, learning strategies but also in society. Testing experts use the term ‘washback’ or ‘impact’ to define the different effects of a test on teaching, learning, and community. This paper first looks at the theoretical background of ‘washback’ and ‘impact’ in language testing by reviewing of relevant literature in the field and then investigates washback effects of IELTS test of on Iranian IELTS teachers and students. The study found significant relationship between the washback effect of IELTS test and teaching strategies of Iranian IELTS teachers as well as performance of Iranian IELTS candidates and their community.

Keywords: high stake tests, IELTS, Iranian Candidates, language testing, test impact, washback

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Authors: Ling Xu, Giuseppe Loprencipe, Antonio D'Andrea

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Asphalt pavement with recycled and sustainable materials has become the most commonly adopted strategy for road construction, including reclaimed asphalt pavement (RAP) and crumb rubber (CR) from waste tires. However, the adhesion and cohesion characteristics of rubberized reclaimed asphalt pavement were still ambiguous, resulting in deteriorated adhesion behavior and life performance. This research investigated the effect of bonding characteristics on rutting resistance and moisture susceptibility of rubberized reclaimed asphalt pavement in terms of two RAP sources with different oxidation levels and two tire rubber with different particle sizes. Firstly, the binder bond strength (BBS) test and bonding failure distinguishment were conducted to analyze the surface behaviors of binder-aggregate interaction. Then, the compatibility and penetration grade of rubberized RAP binder were evaluated by rotational viscosity test and penetration test, respectively. Hamburg wheel track (HWT) test with high-temperature viscoelastic deformation analysis was adopted, which illustrated the rutting resistance. Additionally, a water boiling test was employed to evaluate the moisture susceptibility of the mixture and the texture features were characterized with the statistical parameters of image colors. Finally, the colloid structure model of rubberized RAP binder with surface interaction was proposed, and statistical analysis was established to release the correlation among various indexes. This study concluded that the gel-phase colloid structure and molecular diffusion of the free light fraction would affect the surface interpretation with aggregate, determining the bonding characteristic of rubberized RAP asphalt.

Keywords: bonding characteristics, reclaimed asphalt pavement, rubberized asphalt, sustainable material

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Authors: Esmaeil Zabihi, Seyed Hossein Alavi

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The purpose of this study is a comparison of movement and physical fitness in athlete's male students in altitude and sea-level. The samples consist of 450 subjects in altitude and sea-level in Iran in years of 2013 which were selected randomly from the population. We investigated the effect of high altitude on the tests activity profile of youth high altitude and sea level residents. Methods 450 Sea Level (Mahmood Abad) and 450 Altitude-resident (Shahre-Kord) athlete students tests of physical fitness near sea level (-5 m) and in Altitude (2100 m). This study is Descriptive Research (causal-comparative research). The tests of physical fitness include pull-ups test, sit-ups test, agility test(4 9), 45 sprint test, 1600 m running, long jump, and flexibility test. For determining of different between the physical fitness of altitude and sea-level students was used t-test (P ≤ 0.05). The result of this study show that there is no significant difference between the average of pull-ups test, flexibility, 45 sprints, and agility (4 9) test of students in sea-level and altitude. But there is a significant difference between the average of sit-ups, 1600 m running and long jump in altitude. The students of altitude have higher power rather than sea-level. But the students of sea-level have stronger abdominal muscles and cardio-respiratory endurance rather than altitude. High altitude reduces the distance covered by youth athlete students during tests. Neither acclimatisation nor lifelong residence at high altitude protects against detrimental effects of altitude on tests activity profile.

Keywords: physical fitness, sea level, altitude areas, AAHPERD test

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Authors: Mallikarjunachari Gangapuram

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The design of stimuli-responsive hydrogel nanocomposite thin films is gaining significant attention in these days due to its wide variety of applications. Soft microrobots, drug delivery, biosensors, regenerative medicine, bacterial adhesion, energy storage and wound dressing are few advanced applications in different fields. In this research work, the nanomechanical properties of composite thin films of 20 microns were tuned by applying homogeneous external DC, and AC magnetic fields of magnitudes 0.05 T and 0.1 T. Polyvinyl alcohol (PVA) used as a matrix material and elliptical hematite nanoparticles (ratio of the length of the major axis to the length of the minor axis is 140.59 ± 1.072 nm/52.84 ± 1.072 nm) used as filler materials to prepare the nanocomposite thin films. Both quasi-static nanoindentation, Nano Dynamic Mechanical Analysis (Nano-DMA) tests were performed to characterize the viscoelastic properties of PVA, PVA+Hematite (0.1% wt, 2% wt and 4% wt) nanocomposites. Different properties such as storage modulus, loss modulus, hardness, and Er/H were carefully analyzed. The increase in storage modulus, hardness, Er/H and a decrease in loss modulus were observed with increasing concentration and DC magnetic field followed by AC magnetic field. Contact angle and ATR-FTIR experiments were conducted to understand the molecular mechanisms such as hydrogen bond formation, crosslinking density, and particle-particle interactions. This systematic study is helpful in design and modeling of magnetic responsive hydrogel nanocomposite thin films for biomedical applications.

Keywords: hematite, hydrogel, nanoindentation, nano-DMA

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Authors: Kamrun N. Keya, Nasrin A. Kona, Ruhul A. Khan

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Bamboo fiber (BF) reinforced polypropylene (PP) based composites were fabricated by a conventional compression molding technique. In this investigation, bamboo composites were manufactured using different percentages of fiber, which were varying from 25-65% on the total weight of the composites. To fabricate the BF/PP composites untreated and treated fibers were selected. A systematic study was done to observe the physical, mechanical, and interfacial behavior of the composites. In this study, mechanical properties of the composites such as tensile, impact, and bending properties were observed precisely. Maximum tensile strength (TS) and bending strength (BS) were found for 50 wt% fiber composites, 65 MPa, and 85.5 MPa respectively, whereas the highest tensile modulus (TM) and bending modulus (BM) was examined, 5.73 GPa and 7.85 GPa respectively. The BF/PP based composites were treated with irradiated under gamma radiation (the source strength 50 kCi Cobalt-60) of various doses (i.e. 10, 20, 30, 40, 50 and 60 kGy doses). The effect of gamma radiation on the composites was also investigated, and it found that the effect of 30.0 kGy (i.e. units for radiation measurement is 'gray', kGy=kilogray) gamma dose showed better mechanical properties than other doses. After flexural testing, fracture sides of the untreated and treated both composites were studied by scanning electron microscope (SEM). SEM results of the treated BF/PP based composites showed better fiber-matrix adhesion and interfacial bonding than untreated BF/PP based composites. Water uptake and soil degradation tests of untreated and treated composites were also investigated.

Keywords: bamboo fiber, polypropylene, compression molding technique, gamma radiation, mechanical properties, scanning electron microscope

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Authors: Ayman M. M. Abdelhaleem, Mustafa Gamal Sadek, Kamal Reyad, Montasser M. Dewidar

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The main objective of this research is to study the effect of adding polycarbonate (PC) to pure Acrylonitrile Butadiene Styrene (ABS) using the injection moulding process. The PC was mixed mechanically with ABS in 10%, 20%, 30%, 40%, and 50% by weight. The mechanical properties of pure ABS reinforced with PC were investigated using tensile, impact, hardness, and wear tests. The results showed that, by adding 10%, 20%, 30%, 40%, and 50% wt. of PC to the pure ABS, the ultimate tensile strength increased from 55 N/mm2 for neat ABS to 57 N/mm2 (i.e. 3.63%), 60 N/mm2 (i.e. 9.09%), 63 N/mm2 (i.e. 14.54%), 66 N/mm2 (i.e. 20%), 69 N/mm2 (i.e. 25.45%) respectively. Test results also revealed nearly 5.72% improvement in young's modulus by adding 10% of PC to ABS, 16.74% improvement by adding 20%, 23.34% improvement by adding 30%, 27.75% improvement by adding 40%, and no other increase in case of 50%. The impact test results showed that with the increase of the PC content, first, the impact strength decreased and then increased gradually. The impact strength decreased rapidly when the content of PC was 0% to 10% range. As well as, in the case of 20%, 30%, 40%, and 50% PC, the impact strength is increased. The hardness test results, using the Shore D tester, showed that, as the PC particles contents increased, the hardness increased from 76 for the ABS to 80 for 10% PC, and decreased to 79 for 20% PC, and then increased to 80 in case of 30%, 40%, and 50% PC. Wear test results showed that PC improves the wear resistance of ABS/PC blends. Positron annihilation lifetime spectroscopy showed that with an increase of PC in ABS/PC blends, a slight decrease in free volume size and an increase in the tensile strength due to good adhesion between PC and ABS matrix, which acted as an advantage in the polymer matrix.

Keywords: ABS, PC, injection molding process, mechanical properties, lifetime spectroscopy

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Authors: Mustafa Tufekci, Caner Guven

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In Automotive Industry, sliding door systems that are also used as body closures, are safety members. Extreme product tests are realized to prevent failures in a design process, but these tests realized experimentally result in high costs. Finite element analysis is an effective tool used for the design process. These analyses are used before production of a prototype for validation of design according to customer requirement. In result of this, the substantial amount of time and cost is saved. Finite element model is created for geometries that are designed in 3D CAD programs. Different element types as bar, shell and solid, can be used for creating mesh model. The cheaper model can be created by the selection of element type, but combination of element type that was used in model, number and geometry of element and degrees of freedom affects the analysis result. Sliding door system is a good example which used these methods for this study. Structural analysis was realized for sliding door mechanism by using FE models. As well, physical tests that have same boundary conditions with FE models were realized. Comparison study for these element types, were done regarding test and analyses results then the optimum combination was achieved.

Keywords: finite element analysis, sliding door mechanism, element type, structural analysis

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Authors: Fatih Sulak, Betül A. Özdemir, Beyza Bozdemir

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In order to improve symmetric key research, several competitions had been arranged by organizations like National Institute of Standards and Technology (NIST) and International Association for Cryptologic Research (IACR). In recent years, the importance of authenticated encryption has rapidly increased because of the necessity of simultaneously enabling integrity, confidentiality and authenticity. Therefore, at January 2013, IACR announced the Competition for Authenticated Encryption: Security, Applicability, and Robustness (CAESAR Competition) which will select secure and efficient algorithms for authenticated encryption. Cryptographic algorithms are anticipated to behave like random mappings; hence, it is important to apply statistical randomness tests to the outputs of the algorithms. In this work, the statistical randomness tests in the NIST Test Suite and the other recently designed randomness tests are applied to six second round algorithms of the CAESAR Competition. It is observed that AEGIS achieves randomness after 3 rounds, Ascon permutation function achieves randomness after 1 round, Joltik encryption function achieves randomness after 9 rounds, Morus state update function achieves randomness after 3 rounds, Pi-cipher achieves randomness after 1 round, and Tiaoxin achieves randomness after 1 round.

Keywords: authenticated encryption, CAESAR competition, NIST test suite, statistical randomness tests

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Authors: Sanjeev Mukherjee, Satyendra Mittal

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This paper presents the experimental investigations on the behaviour of a group of single, double and triple helical screw anchors embedded vertically at the same level in sand. The tests were carried out on one, two, three and four numbers of anchors in sand for different depths of embedment keeping shallow and deep mode of behaviour in mind. The testing program included 48 tests conducted on three model anchors installed in sand whose density kept constant throughout the tests. It was observed that the ultimate pullout load varied significantly with the installation depth of the anchor and the number of anchors. The apparent coefficient of friction (f*) between anchor and soil was also calculated based on the test results. It was found that the apparent coefficient of friction varies between 1.02 and 4.76 for 1, 2, 3, and 4 numbers of single, double and triple helical screw anchors. Plate load tests conducted on model soil showed that the value of ф increases from 35o for virgin soil to 48o for soil with four double screw helical anchors. The graphs of ultimate pullout capacity of a group of two, three and four no. of anchors with respect to one anchor were plotted and design equations have been proposed correlating them. Based on these findings, it has been concluded that the load-displacement relationships for all groups can be reduced to a common curve. A 3-D finite element model, PLAXIS, was used to confirm the results obtained from laboratory tests and the agreement is excellent.

Keywords: apparent coefficient of friction, helical screw anchor, installation depth, plate load test

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Authors: Feng Fu, Ahmad Bazgir

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This study aimed to investigate and examine the structural behaviour of steel fibre reinforced concrete slabs when subjected to impact loading using drop weight method. A number of compressive tests, tensile splitting tests, as well as impact tests were conducted. The experimental work consists of testing both conventional reinforced slabs and SFRC slabs. Parameters to be considered for carrying out the test will consist of the volume fraction of steel fibre, type of steel fibres, drop weight height and number of blows. Energy absorption of slabs under impact loading and failure modes were examined in-depth and compared with conventional reinforced concrete slab are investigated.

Keywords: steel fibre reinforce concrete, compressive test, tensile splitting test, impact test

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Authors: Khoa K. Doan

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Assessment plays an essential role in teaching and learning English as it aims to measure the learning outcomes. Designing appropriate test types and procedures for four skills, especially productive skills, is a very challenging task for teachers of English. The assessment scheme is supposed to provide precise measures and fair opportunities for students to demonstrate what they can do with their language skills. This involves content domains, measurement techniques, administrative feasibility, target populations, and potential sources of testing bias. Based on these elements, a review of end-of-term speaking tests for English-majored students at Ho Chi Minh City Open University (Viet Nam) was undertaken for the purpose of analyzing the strengths and limitations of the testing tool for the speaking assessment. It helped to identify what could be done to facilitate the process of teaching and learning in that context.

Keywords: assessment, oral tests, speaking, testing

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Authors: Omar S. Qaftan, T. T. Sabbagh

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This paper studies the free-field response by adopting a flexible membrane container as soil boundary for experimental shaking table tests. The influence of the soil container boundary on the soil behaviour and the dynamic soil properties under seismic effect were examined. A flexible container with 1/50 scale factor was adopted in the experimental tests, including construction, instrumentation, and determination of the results of dynamic tests on a shaking table. Horizontal face displacements and accelerations were analysed to determine the influence of the container boundary on the performance of the soil. The outputs results show that the flexible boundary container allows more displacement and larger accelerations. The soil in a rigid wall container cannot deform as similar as the soil in the real field does. Therefore, the response of flexible container tested is believed to be more reliable for soil boundary than that in the rigid container.

Keywords: soil, seismic, earthquake, interaction

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Authors: Kamrun N. Keya, Nasrin A. Kona, Ruhul A. Khan

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Sugarcane bagasse (SCB)-reinforced Polypropylene (PP) Based matrix composites (25-45 wt% fiber) were fabricated by a compression molding technique. The SCB surface was chemically modified using 5%-10% sodium hydroxide (NaOH), and after that, mechanical properties, water uptake, and soil degradation of the composites were investigated. Tensile strength (TS), tensile modulus (TM), bending strength (BS), bending modulus (BM) and elongation at break (Eb%) of the 30wt% composites were found to be 35.6 MPa, 10.2 GPa, 56 MPa, 5.6 GPa, and 11%, respectively. The SCB/PP based composites were treated with irradiated under gamma radiation (the source strength 50 kCi Cobalt-60) of various doses (2.5 kGy to 10 kGy). The effect of gamma radiation on the composites was also investigated, and it found that the effect of 5.0 kGy (i.e. units for radiation measurement is 'gray', kGy=kilogray ) gamma dose showed better mechanical properties than other doses. The results revealed that the combination of the chemical modification of the SCB fibers and irradiation of the composites were more effective in compatibility improvement than chemical modification alone. After flexural testing, fracture sides of the untreated and treated both composites were studied by scanning electron microscope (SEM). SEM results of the treated SCB/PP based composites showed better fiber-matrix adhesion than untreated SCB/PP based composites. However, it was found that the treated SCB/PP composite has better mechanical strength, durability, and more receptivity than untreated SCB/PP based composite.

Keywords: sugarcane bagasse (SCB), polypropylene (PP), mechanical properties, scanning electron microscope (SEM), gamma radiation, water uptake tests and soil degradation

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Authors: Huseyin Guler, Cigdem Kosar

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The aim of this study is to propose Bridge estimator for seasonal unit root tests. Seasonality is an important factor for many economic time series. Some variables may contain seasonal patterns and forecasts that ignore important seasonal patterns have a high variance. Therefore, it is very important to eliminate seasonality for seasonal macroeconomic data. There are some methods to eliminate the impacts of seasonality in time series. One of them is filtering the data. However, this method leads to undesired consequences in unit root tests, especially if the data is generated by a stochastic seasonal process. Another method to eliminate seasonality is using seasonal dummy variables. Some seasonal patterns may result from stationary seasonal processes, which are modelled using seasonal dummies but if there is a varying and changing seasonal pattern over time, so the seasonal process is non-stationary, deterministic seasonal dummies are inadequate to capture the seasonal process. It is not suitable to use seasonal dummies for modeling such seasonally nonstationary series. Instead of that, it is necessary to take seasonal difference if there are seasonal unit roots in the series. Different alternative methods are proposed in the literature to test seasonal unit roots, such as Dickey, Hazsa, Fuller (DHF) and Hylleberg, Engle, Granger, Yoo (HEGY) tests. HEGY test can be also used to test the seasonal unit root in different frequencies (monthly, quarterly, and semiannual). Another issue in unit root tests is the lag selection. Lagged dependent variables are added to the model in seasonal unit root tests as in the unit root tests to overcome the autocorrelation problem. In this case, it is necessary to choose the lag length and determine any deterministic components (i.e., a constant and trend) first, and then use the proper model to test for seasonal unit roots. However, this two-step procedure might lead size distortions and lack of power in seasonal unit root tests. Recent studies show that Bridge estimators are good in selecting optimal lag length while differentiating nonstationary versus stationary models for nonseasonal data. The advantage of this estimator is the elimination of the two-step nature of conventional unit root tests and this leads a gain in size and power. In this paper, the Bridge estimator is proposed to test seasonal unit roots in a HEGY model. A Monte-Carlo experiment is done to determine the efficiency of this approach and compare the size and power of this method with HEGY test. Since Bridge estimator performs well in model selection, our approach may lead to some gain in terms of size and power over HEGY test.

Keywords: bridge estimators, HEGY test, model selection, seasonal unit root

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Authors: Vaclav Mentl, P. Zlabek, J. Volak

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New methods of mechanical testing were developed recently that are based on making use of miniature test specimens (e.g. Small Punch Test). The most important advantage of these method is the nearly non-destructive withdrawal of test material and small size of test specimen what is interesting in cases of remaining lifetime assessment when a sufficient volume of the representative material cannot be withdrawn of the component in question. In opposite, the most important disadvantage of such methods stems from the necessity to correlate test results with the results of standardised test procedures and to build up a database of material data in service. The correlations among the miniature test specimen data and the results of standardised tests are necessary. The paper describes the results of fatigue tests performed on miniature tests specimens in comparison with traditional fatigue tests for several steels applied in power producing industry. Special miniature test specimens fixtures were designed and manufactured for the purposes of fatigue testing at the Zwick/Roell 10HPF5100 testing machine. The miniature test specimens were produced of the traditional test specimens. Seven different steels were fatigue loaded (R = 0.1) at room temperature.

Keywords: mechanical properties, miniature test specimens, correlations, small punch test, micro-tensile test, mini-charpy impact test

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Authors: Carine Cridelich, Pablo Juesas Cano, Emmanuel Ramasso, Noureddine Zerhouni, Bernd Weiler

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Safety is one of the most important considerations when buying a new car. While active safety aims at avoiding accidents, passive safety systems such as airbags and seat belts protect the occupant in case of an accident. In addition to legal regulations, organizations like Euro NCAP provide consumers with an independent assessment of the safety performance of cars and drive the development of safety systems in automobile industry. Those ratings are mainly based on injury assessment reference values derived from physical parameters measured in dummies during a car crash test. The components and sub-systems of a safety system are designed to achieve the required restraint performance. Sled tests and other types of tests are then carried out by car makers and their suppliers to confirm the protection level of the safety system. A Knowledge Discovery in Databases (KDD) process is proposed in order to minimize the number of tests. The KDD process is based on the data emerging from sled tests according to Euro NCAP specifications. About 30 parameters of the passive safety systems from different data sources (crash data, dummy protocol) are first analysed together with experts opinions. A procedure is proposed to manage missing data and validated on real data sets. Finally, a procedure is developed to estimate a set of rough initial parameters of the passive system before testing aiming at reducing the number of tests.

Keywords: KDD process, passive safety systems, sled test, dummy injury assessment reference values, frontal impact

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Authors: Armin Rahmatfam, Mohammad Zehsaz, Farid Vakili Tahami, Nasser Ghassembaglou

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In this paper the thermal ratcheting, kinematic hardening parameters C, γ, isotropic hardening parameters and also k, b, Q combined isotropic/kinematic hardening parameters have been obtained experimentally from the monotonic, strain controlled cyclic tests at room and elevated temperatures of 20°C, 100°C, and 400°C. These parameters are used in nonlinear combined isotropic/kinematic hardening model to predict better description of the loading and reloading cycles in the cyclic indentation as well as thermal ratcheting. For this purpose, three groups of specimens made of Aluminum 7075-T6 have been investigated. After each test and using stable hysteretic cycles, material parameters have been obtained for using in combined nonlinear isotropic/kinematic hardening models. Also the methodology of obtaining the correct kinematic/isotropic hardening parameters is presented.

Keywords: combined hardening model, kinematic hardening, isotropic hardening, cyclic tests

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Authors: Abdel Hadi N. Ebraheim, Eman Azomi, Nefisa A. Fahmy

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This paper designs and implements a computer-aided system (CAS) to help detect and diagnose liver cirrhosis in patients with Chronic Hepatitis C. Our system reduces the required features (tests) the patient is asked to do to tests to their minimal best most informative subset of tests, with a diagnostic accuracy above 99%, and hence saving both time and costs. We use the Support Vector Machine (SVM) with cross-validation, a Multilayer Perceptron Neural Network (MLP), and a Generalized Regression Neural Network (GRNN) that employs a base of radial functions for functional approximation, as classifiers. Our system is tested on 199 subjects, of them 99 Chronic Hepatitis C.The subjects were selected from among the outpatient clinic in National Herpetology and Tropical Medicine Research Institute (NHTMRI).

Keywords: liver cirrhosis, artificial neural network, support vector machine, multi-layer perceptron, classification, accuracy

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Authors: Murat Avci, Fatih Kosar, Ismail Yilmaz

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In this study, structure-flow interaction for water brake mechanism is studied with Abaqus CEL approach. The water brake mechanism is used for dynamic systems such as sled system on rail. For the achievement of these system tests, structure-flow interaction should be investigated in detail. This study is about a sled test of an aircraft subsystem which rises to supersonic speeds thanks to rocket engines. To decrease or to stop the thrusting rocket sleds, water brake mechanisms are used. Water brake mechanism provides the deceleration of the structures that have supersonic speeds. Therefore, structure-flow interaction may cause damage to the water brake mechanism. To verify all design revisions with system tests are so costly so that some decisions are taken in accordance with numerical methods. In this study, structure-flow interaction that belongs to water brake mechanism is solved with Abaqus CEL approach. Fluid and deformation on the structure behaviors are modeled at the same time thanks to CEL approach. Provided analysis results are corrected with the dynamic tests. Deformation zones seen in numerical analysis are also observed in dynamic tests. Finally, Johnson-Cook material model parameters used for this analysis are proven, and it is understood that these parameters can be used for dynamic analysis like water brake mechanism.

Keywords: aircraft, rocket, structure-flow, supersonic

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Authors: Enjie Xu, Zhen Huang, Kunpeng Zhu, Jianping Hu, Xiaolong Ma, Yongjie Wang, Jiazhuang Zhu, Chunlin Zhang

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Abstract: Hypoxia and dedifferentiation of osteosarcoma (OS) cells leads to poor prognosis. We plan to identify the role of hypoxia on dedifferentiation and the associated signaling pathways. We performed a sphere formation assay and determined spheroid cells as dedifferentiated cells by detecting stem cell-like markers. RNAi assay was used to explore the expression relationship between hypoxia inducible factor 1 subunit alpha (HIF1A) and platelet derived growth factor receptor beta (PDGFRB). We obtained PDGFRB knockdown and overexpression cells through lentiviral infection experiments and the effects of PDGFRB on cytoskeleton rearrangement and cell adhesion were explored by immunocytochemistry. Wound-healing experiments, transwell assays, and animal trials were employed to investigate the effect of PDGFRB on OS metastasis. Dedifferentiated OS cells were found to exhibit high expression of HIF1A and PDGFRB, and HIF1A promoted the expression of PDGFRB, subsequently activated ras homolog family member A (RhoA), and increased the phosphorylation of myosin light chain (MLC). PDGFRB also enhanced the phosphorylation of focal adhesion kinase (FAK). The OS cell morphology and vinculin distribution were altered by PDGFRB. PDGFRB also promoted cell dedifferentiation and had a significant impact on the metastasis of OS cells both in vitro and in vivo. Our results demonstrated that HIF1A up-regulated PDGFRB under hypoxic conditions, and PDGFRB regulated the actin cytoskeleton by activating RhoA and subsequently phosphorylating MLC, thereby promoting OS dedifferentiation and pulmonary metastasis.

Keywords: osteosarcoma, dedifferentiation, metastasis, cytoskeleton rearrangement, PDGFRB, hypoxia

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Authors: Trunal Bhujangrao, Catherine Froustey, Fernando Veiga, Philippe Darnis, Franck Girot Mata

Abstract:

The understanding of the material behavior under shear loading has great importance for a researcher in manufacturing processes like cutting, machining, milling, turning, friction stir welding, etc. where the material experiences large deformation at high temperature. For such material behavior analysis, hot shear tests provide a useful means to investigate the evolution of the microstructure at a wide range of temperature and to improve the material behavior model. Shear tests can be performed by direct shear loading (e.g. torsion of thin-walled tubular samples), or appropriate specimen design to convert a tensile or compressive load into shear (e.g. simple shear tests). The simple shear tests are straightforward and designed to obtained very large deformation. However, many of these shear tests are concerned only with the elastic response of the material. It is becoming increasingly important to capture a plastic response of the material. Plastic deformation is significantly more complex and is known to depend more heavily on the strain rate, temperature, deformation, etc. Besides, there is not enough work is done on high-temperature shear loading, because of geometrical instability occurred during the plastic deformation. The aim of this study is to design a new shear tensile specimen geometry to convert the tensile load into dominant shear loading under plastic deformation. Design of the specimen geometry is based on FEM. The material used in this paper is AA7075 alloy, tested quasi statically under elevated temperature. Finally, the microstructural changes taking place during

Keywords: AA7075 alloy, dynamic recrystallization, edge effect, large strain, shear tensile test

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Authors: M. O. Bayram, H. B. Gencdal, N. O. Fercan, B. Basbug

Abstract:

Liquid limit, which is used as a measure of soil strength, can be detected by Casagrande and fall-cone testing methods. The two methods majorly diverge from each other in terms of operator dependency. The Casagrande method that is applied according to ASTM D4318-17 standards may give misleading results, especially if the calibration process is not performed well. To reveal the effect of calibration for drop height and amount of soil paste placement in the Casagrande cup, a series of tests were carried out by multipoint method as it is specified in the ASTM standards. The tests include the combination of 6 mm, 8 mm, 10 mm, and 12 mm drop heights and under-filled, half-filled, and full-filled Casagrande cups by kaolinite samples. It was observed that during successive tests, the drop height of the cup deteriorated; hence the device was recalibrated before and after each test to provide the accuracy of the results. Besides, the tests by under-filled and full-filled samples for higher drop heights revealed lower liquid limit values than the lower drop heights revealed. For the half-filled samples, it was clearly seen that the liquid limit values didn’t change at all as the drop height increased, and this explains the function of standard specifications.

Keywords: calibration, casagrande cup method, drop height, kaolinite, liquid limit, placing form

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Authors: Asad Naeem, Jinkoo Kim

Abstract:

This research proposes a self-centering passive damping system consisting of a spring viscous damper linked with a preloaded tendon. The seismic performance of the spring viscous damper is evaluated by pseudo-dynamic tests, and the results are used for the formulation of an analytical model of the damper in the structural analysis program. The shaking table tests of a two-story steel frame installed with the proposed damping system are carried out using five different earthquake records. The results from the shaking table tests are verified by numerical simulation of the retrofitted structure. The results obtained from experiments and numerical simulations demonstrate that the proposed damping system with self-centering capability is effective in reducing earthquake-induced displacement and member forces.

Keywords: seismic retrofit, spring viscous damper, shaking table test, earthquake resistant structures

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Authors: Clara Oliver, Oibar Martinez

Abstract:

This paper is intended to reveal the severity of electrostatic discharge (ESD) effects in electronic and optoelectronic devices by performing sensitivity tests based on Human Body Model (HBM) standard. We explain here the HBM standard in detail together with the typical failure modes associated with electrostatic discharges. In addition, a prototype of electrostatic charge generator has been designed, fabricated, and verified to stress electronic devices, which features a compact high voltage source. This prototype is inexpensive and enables one to do a battery of pre-compliance tests aimed at detecting unexpected weaknesses to static discharges at the component level. Some tests with different devices were performed to illustrate the behavior of the proposed generator. A set of discharges was applied according to the HBM standard to commercially available bipolar transistors, complementary metal-oxide-semiconductor transistors and light emitting diodes. It is observed that high current and voltage ratings in electronic devices not necessarily provide a guarantee that the device will withstand high levels of electrostatic discharges. We have also compared the result obtained by performing the sensitivity tests based on HBM with a real discharge generated by a human. For this purpose, the charge accumulated in the person is monitored, and a direct discharge against the devices is generated by touching them. Every test has been performed under controlled relative humidity conditions. It is believed that this paper can be of interest for research teams involved in the development of electronic and optoelectronic devices which need to verify the reliability of their devices in terms of robustness to electrostatic discharges.

Keywords: human body model, electrostatic discharge, sensitivity tests, static charge monitoring

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Authors: Ozden Saygili, Eser Cakti

Abstract:

The masonry building stock in Istanbul and in other cities of Turkey are exposed to significant earthquake hazard. Determination of the safety of masonry structures against earthquakes is a complex challenge. This study deals with experimental tests and non-linear dynamic analysis of masonry structures modeled through discrete element method. The 1:10 scale model of Mustafa Paşa Mosque was constructed and the data were obtained from the sensors on it during its testing on the shake table. The results were used in the calibration/validation of the numerical model created on the basis of the 1:10 scale model built for shake table testing. 3D distinct element model was developed that represents the linear and nonlinear behavior of the shake table model as closely as possible during experimental tests. Results of numerical analyses with those from the experimental program were compared and discussed.

Keywords: dynamic analysis, non-linear modeling, shake table tests, masonry

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Authors: Bharat Kumar, Deepak Kumar, Vijay Chaudhry

Abstract:

Zirconium alloys are used as core components of nuclear reactors due to their high wear resistance, good corrosion properties, and good mechanical stability at high temperatures. The present work simulates the contact between the calandria tube and the liquid injection shutdown system (LISS) nozzle. The Calandria tube is the outer covering of the pressure tube. Water flows inside the pressure tube through fuel claddings which produces vibration in the pressure tube along with vibration in the calandria tube. Fretting wear takes place at the point of contact between the calandria tube and the LISS nozzle. Fretting tests were performed under different conditions, such as; varying fretting duration (i.e., 1 to 4 hours), varying frequency (i.e., 5 to 6.5 Hz), and varying amplitude (100 to 400 µm). The formation of the oxide layer was observed during the fretting wear test; as a result, the worn product. The worn surfaces were analyzed with scanning electron microscopy (SEM) to analyze the wear mechanism involved in the fretting test, and Energy dispersive x-ray spectroscopy (EDS) and Raman spectroscopy were used to confirm the presence of an oxide layer on the worn surface. The oxide layer becomes more uniform with fretting duration in case of water submerged condition as compared to dry contact condition. The oxide layer is deeply removed at high amplitude due to the change of wear mechanism from adhesion to abrasion, as confirmed by the presence of micro ploughing and micro cutting. Low amplitude fretting favors the formation of the tribo-oxide layer.

Keywords: tribo-oxide layer, wear, mechanically mixed layer, zircaloy

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