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排序方式: 共有513条查询结果,搜索用时 15 毫秒
71.
Dario Croccolo Massimiliano De Agostinis Stefano Fini Giorgio Olmi Francesco Robusto Sneana iri‐Kosti Slobodan Mora
a Neboja Bogojevi 《Fatigue & Fracture of Engineering Materials & Structures》2019,42(1):374-386
This work deals with the effect of build orientation and of allowance for machining on DMLS‐produced Maraging Steel MS1. The experimental results, arranged by tools of Design of Experiment, have been statistically processed and compared. The outcomes were that, probably due to effect of the thermal treatment, machining, and material properties, the aforementioned factors do not have a significant impact on the fatigue response. This made it possible to work out a global curve that accounts for all the results, consisting in a high amount of data points. This can be regarded as one of the most complete and reliable fatigue models in the current literature. Fractographic and micrographic studies have been performed as well, to individuate the crack initiation points, usually located at subsurface porosities, and to investigate the location of internal inclusions and the actual martensitic microstructure along the stacking direction and on the build plane. 相似文献
72.
73.
74.
The image‐based inertial impact (IBII) test has shown promise for measuring properties of composites at strain rates where existing test methods become unreliable due to inertial effects (> 102 s?1 ). Typically, the IBII tests are performed with a single camera, and therefore, to use surface measurements for material property identification, it is necessary to assume that the test is two‐dimensional. In this work, synchronised ultra‐high‐speed cameras are used to quantify the relevance of this assumption when nonuniform, through‐the‐thickness loading is applied to interlaminar samples. Initial experiments revealed that an angular misalignment of approximately 1° between the impact faces of the waveguide and projectile created a bending wave that propagated along the sample behind the axial pulse. Even under these conditions, consistent measurements of stiffness were made by assuming a linear distribution of the behaviour through‐the‐thickness. When the misalignment was reduced to 0.2°, the effects on single‐sided measurements were significantly reduced. The two alignment cases were compared to show that three‐dimensional loading had a small effect on stiffness identification (approximately 5% bias) relative to failure stress (approximately 30% bias). This study highlights the importance of impact alignment for reliable characterisation of the interlaminar failure stress and was used to establish guidelines for diagnosing loading issues from single‐sided measurements. 相似文献
75.
This work focuses on simultaneous approximation terms (SATs) for multidimensional summation-by-parts (SBP) discretizations of linear second-order partial differential equations with variable coefficients. Through the analysis of adjoint consistency and stability, we present several conditions on the SAT penalties for general operators, including those operators that do not have nodes on their boundary or do not correspond with a collocation discontinuous Galerkin method. Based on these conditions, we generalize the modified scheme of Bassi and Rebay and the symmetric interior penalty Galerkin method to SBP-SAT discretizations. Numerical experiments are carried out on unstructured grids with triangular elements to verify the theoretical results. 相似文献
76.
Harumi Sato Masahiko Shimoyama Taeko Kamiya Toru Amari Slobodan aic Toshio Ninomiya Heinz W. Siesler Yukihiro Ozaki 《应用聚合物科学杂志》2002,86(2):443-448
Raman spectra have been measured for pellets of five samples of high‐density polyethylene (HDPE), seven samples of low‐density polyethylene (LDPE), and six samples of linear low‐density polyethylene (LLDPE). The obtained Raman spectra have been compared to find out characteristic Raman bands of HDPE, LDPE, and LLDPE. Principal component analysis (PCA) was applied to the Raman spectra in the 1600–650 cm?1 region after multiplicative scatter correction (MSC) to discriminate the Raman spectra of the three different PE species. They are classified into three groups by a score plot of PCA factor 1 vs. 2. HDPE with high density and high crystallinity gives high scores on the factor 1 axis, while LDPE with low density and low crystallinity yields negative scores on the same axis. It seems that factor 1 reflects the density or crystallinity. A PC weight loadings plot for factor 1 shows six upward peaks corresponding to the bands arising from the crystalline parts or all‐trans ? (CH2)n? groups and seven downward peaks ascribed to the bands of the amorphous or anisotropic regions and those arising from the short branches. Partial least‐squares (PLS‐1) regression was applied to the Raman spectra after MSC to propose calibration models that predict the density, crystallinity, and melting points of the polyethylenes. The correlation coefficient was calculated to be 0.9941, 0.9800, and 0.9709 for the density, crystallinity, and melting point, respectively, and their root‐mean‐square error of cross validation (RMSECV) was found to be 0.0015, 3.3707, and 2.3745, respectively. The loadings plot of factor 2 for the prediction of melting point is largely different from those for the prediction of density and crystallinity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 443–448, 2002 相似文献
77.
Slobodan?P.??erbanovi? Ivona?R.?Grguri? Mirjana?Lj.?Kijev?anin Aleksandar?Z.?Tasi? Bojan?D.?Djordjevi?Email author 《Korean Journal of Chemical Engineering》2004,21(4):858-866
A comparison of the performances of two different approaches of cubic equations of state models, based on a classical van
der Waals and mixing rules incorporating theG
E
equation, was carried out for correlation of Vapor-Liquid Equilibria (VLE), HE and C
P
E
data alone, and simultaneous correlation of VLE+HE, VLE+C
P
E
, HE +C
P
E
and VLE+HE +C
P
E
data for the diethers (1,4-dioxane or 1,3-dioxolane) with n-alkane systems. For all calculations the Peng-Robinson-Stryjek-Vera
cubic equation of state (PRSV CEOS) was used. A family of mixing rules for the PRSV CEOS based on the Modified van der Waals
one-fluid mixing rule (MvdW1) and two well-known CEOS/GE mixing rules (MHV1 and MHV2), was considered. The NRTL equation, as the GE model with linear or reciprocal temperature dependent parameters, was incorporated in the CEOS/GE models. The results obtained by the CEOS/GE models exhibit significant improvement in comparison to the MvdW1 models. 相似文献
78.
Minoru Tomozawa Kenneth M. Davis Jared H. Seaman Emily M. Aaldenberg 《Journal of the American Ceramic Society》2017,100(10):4548-4561
Anomalous water diffusion into SiO2 glass was observed in a low temperature range, below ~850°C, under a constant water vapor pressure of 355 Torr (47.3 kPa). Both the effective water diffusion coefficient and water solubility exhibited an anomalous time dependence. For example, water solubility in the low temperature range increased initially, achieving much higher values than expected based on extrapolation from higher temperature data, and then decreased with time toward an equilibrium value. This phenomenon was reported earlier, but a complete explanation was not possible; a new model is presented based upon glass surface compressive stress generation and subsequent surface stress relaxation. Water diffusion can promote stress generation and stress relaxation, both of which affect the reaction between diffused molecular water and the glass structure. By considering these stress effects, the anomalous water diffusion behavior in silica glass is explained. Furthermore, the same model can account for the reversal of external tensile and compressive stress effects on water solubility and diffusivity in silica glass observed after a few hours of heat treatment at 650°C in 355 Torr water vapor pressure. 相似文献
79.
Nikola Bulatović Nikola Žarić Slobodan Djukanović Igor Radusinović Milica Pejanović-Djurišić 《Wireless Personal Communications》2017,92(1):237-250
The paper addresses the Be Responsible platform, a representative example of human-centric sensing network which, relying on the Info-Communication and Internet of Things concepts, aims to improve the communication between citizens, on one side, and government authorities, on the other side, with the purpose of resolving various problems encountered in a modern society. A widespread network of human-centric smartphone devices and PCs has been used as a valuable source of data collected and processed in order to trigger adequate actions upon problem resolving. In this way, humans acting as sensor operators and data sources become a powerful factor in improving their society. The Be Responsible platform enables the people to report the irregularities in various aspects of their social life (grey economy, misuse of government vehicles, ecology, traffic), and hence to take active part in resolving them. It also promotes positive and responsible social and institutional behavior, which has to be nurtured in any society seeking progress. The number of submitted reports as well as the money collected from the fine revenues and subsequently invested in projects of social good, undoubtedly prove that what could not be achieved through years of traditional government-led policy approach, was achieved in months of citizen engagement. 相似文献
80.
Aleksandar Vencl Ilija Bobić Milan T. Jovanović Miroslav Babić Slobodan Mitrović 《Tribology Letters》2008,32(3):159-170
In the present study, the effect of the Al2O3 particles (average size of 12 μm, 3 and 10 wt.%) reinforcement on the microstructure and tribological properties of Al–Si
alloy (A356) was investigated. Composites were produced by applying compocasting process. Tribological properties of unreinforced
alloy and composites were studied, using pin-on-disc tribometer, under dry sliding conditions at different specific loads
and sliding speed of 1 m/s. Microhardness measurements, optical microscope and scanning electron microscope were used for
microstructural characterization and investigation of worn surfaces and wear debris. During compocasting of A356 alloy, a
transformation from a typical dendritic primary α phase to a non-dendritic rosette-like structure occurred. Composites exhibited
better wear resistance compared with unreinforced alloy. Presence of 3 wt.% Al2O3 particles in the composite material affected the wear resistance only at specific loads up to 1 MPa. The wear rate of composite
with 10 wt.% Al2O3 particles was nearly two order of the magnitude lower than the wear rate of the matrix alloy. Dominant wear mechanism for
all materials was adhesion, with others mechanisms: oxidation, abrasion and delamination as minor ones. 相似文献