Search results

In this sense, nature offers a number of residual stresses free simple layered structures, such as shells or teeth, which present improved failure behaviour as compared to that of the individual components.
A number of ceramic-metal and ceramic-polymer laminates have been developed on this basis [14-18].
The approach was based on the effect of small amounts of titania as agents for alumina grain growth enhancement.
Starting from a fine grained green body that combined alumina layers with composite layers made of mixtures of alumina and titania, the sintering schedule led to a layered structure with external layers of small grain sized alumina combined with additional "in situ" formed layers contiguous to the composite layers constituted by large alumina grains due to the diffusion of titanium (Fig. 5a).
The large alumina grains of the in situ formed large grained alumina layer act as sites for crack branching and as bridges in the wake of the propagating crack.

The liquid phase penetrates into the boundaries between ZnO grains, and enhances grain growth and densification of the film.
This process would strengthen the interfacial stress of the ZnO grains, which may be the main cause of the shift in the modes of the Raman spectrum.
As a result, as the film is oriented more preferentially along the [002] direction, the grain size of the film is increased, the Zn content decreased, the tensile stress of the ZnO crystals also becomes higher and the absorption is increased.
Films doped with 5at.% of tin had, at 500°C, a stronger c-axis orientation perpendicular to the substrate and a smaller grain than that of the others.
In the Raman spectra, the modes shifted to lower wave-numbers and to higher wave-numbers, respectively, when the film were doped with Sn; indicating that the tensile residual stress and the free-carrier concentration increased with doping.

In the case where grain boundaries are considered as being the dominant barrier, D is regarded as the grain diameter.
As this alloy was obtained in the form of rolled plate, it had a preferred grain orientation.
The average grain size was as follows: 220 µm in the longitudinal direction, 80 µm in the transverse direction and 52 µm in the short transverse direction.
Thus, the stress gradient associated with the dents at the first barrier (grain size) dominates over the closure stress effect.
Number of cycles to failure, Nf 104 105 106 107 108 Maximum stress, MPa 100 200 300 400 500 Unpeened Optimum peened Curve fit worse peened Curve fit optimum peened Worst peened Unpeened 2024-T351 X X (S330, 100%, 30º) Y (S110, 200%, 90º) Y Z (S330, 200%, 90º) Z (a) Figure 3.

With the increase of the number of hammer, a layer of encrustation appears at the surface of the soil column, which prevents the energy from being transferred to the bottom.
Graining effect is quite obvious and detrital grain quantity increases so that soil particle edge becomes fuzzy when lime dosage is 6%.
Soil particle edge has completely fuzzy and at the same time a large number of lime Crystal substance fill in the gaps between soil particles [[]CHENG Yu,SHI Ming-lei,ZHOU Zheng-ming.Aggregation effect of slaked lime on treated expansive soils[J].Rock and Soil Mechanics,2008,29(8):2209-2214. ] when lime dosage is 9%.
Generally, when lime dosage is 2% graining reaction happens, meanwhile, soil reunions.
Graining and aggregation play a leading role in improving expansive soil，which Change the soil particle shape, particle size, the interparticle contact, consolidation state ,and change the nature of the soil.

There are a number of reports about nanoferrite materials in litrature but only few of them combines the effects of dopent elements on microstructures and consequent effects on the electrical and magnetic properties.
The grain size increased by sintering.
The structure of the prepared samples consists of conducting grains separated by highly resistive thin layers (grain boundaries).
As the crystallite size decreases, the total grain area increases which subsequently increases resistivity.
Grain growth was found to occur with sintering.

Continuous casting technologies are being developed that could greatly reduce the number of subsequent processing steps required, and lower the manufacturing costs [1,2].
It is well known that aluminum alloys can be strengthened by a number of mechanisms such as particle dispersion hardening, solute hardening, age hardening precipitates and grain size reduction.
It would be effective to coarsen the recrystallization grain structure to prevent the deformation of fin stock at elevated temperatures.
During brazing treatment the grain size grew up to 1-2mm.
Coarse recystallized grains enhanced the permeation of molten brazing during the brazing process.

The quartz content is from 28% to 46% with average value being 39.5%; the maximum grain diameter, 0.50~3.80 mm, median grain diameter, 0.15~0.50 mm.
In many cases, when wetting-phase saturation is50%, capillary pressures often exceeds 1,000 psi, which indicates that the diameter of a large number of pore throats is less than 0.1μm, varying from micro level to millimicro level (Hartmann and Beaumont,1999).
The same microfacies get better as grain gradation increase, conglomerate and grit stone have the best physical properties, medium-grained sandstone comes the second, followed by fine sandstone and siltstone.
In the parts where tectonic deformation stress are concentrated, the volume of sediments constantly shrinks, porosity continually decrease and the sliding, displacement, deformation, rupture of grains occur within sediments, further resulting in rearrangement or structural change of sediment grains.
Besides, as the lateral stress from tectonization constantly increase, the solubility at the parts where grains contact also increase, and lattice distortion and pressure solution takes place, thus enhancing the degree of reservoir densification.

Fig. 2 Creep rupture test specimen of simulated welded joint Table 2 The statistics of fracture’s locations Locations of fracture Number Fusion zone between the 1st and the 2nd transition layers 4 The 2nd transition layer 2 Fusion zone between the 2nd and the 3rd transition layers 7 The 3rd transition layer 1 Fusion zone between the 3rd and the 4th transition layers 1 The 4th transition layer 1 As shown in Table 2, the number of fractures appear at fusion zones next to the 2nd transition layer is the largest one, so this mode of fracture can be considered as a typical mode.
It can be found in Fig. 7 (b) and Fig. 7 (c) that, the grains around the fusion zone are strip, and they are nearly parallel to the micro-cracks, while the other grains are nearly vertical to them.
This is because the special direction of strip grains around the fusion zone causes shearing stress under tensile loading, and makes the micro-cracks grow in the form of tearing.
(3) The direction of the grains in fusion zones is obviously regular.
The special feature of grains’ direction leads to shear stress at grain boundaries under tensile loading, which makes creep voids grow in the form of tearing.

These differences strongly depend on the angle between the slip plane and the polished plane, and the shear stress direction caused by slurry grains.
It is likely that the polishing rate is influenced by the distribution of the dislocations, strain, and shear stress caused by slurry grains.
The mass removal rate in the polishing is related to the formation of "small grains layer" introduced by polishing.
In the case where many small grains are formed in the layer below the polished surface, as seen in the c plane- polished specimen, the mass removal rate is likely to be high.
Acknowledgments This paper was funded by NSFC with contract number 50705088 and opening foundation of the state tribology laboratory (Tsinghua University), it is also funded by the projects of Zhejiang nature science foundation and Zhejiang science and technology bureau with contract number 207C21061 and Y105610 respectively.

Heavy crankshaft full-grain-flow forging technology is one of effective ways to guarantee parts to work correctly in complex stress state (see Figure 1).
Fig.1 Schematic diagram of full-grain-flow forging process 1.Crank throw 2.Crank journal 3.Main journal Characterized by continuous fiber and a reasonable distribution of the crankshaft, full fiber upset-bending forging technology greatly improves the crankshaft fatigue strength, increases metal utilization, reduces production cost, and is superior to freedom forging.
Among them, TR upset-bending forging process has been extensively used in making heavy crankshaft at home and abroad, because the continuous grain flow upset-bending process improve significantly the fatigue, material usage and machining productivity.
Though a large number of experimental simulations, the result show that the forming quality with barstock as the blank is better than that of stepped shaft, which usually is regarded as an easier holding and forming shape.
Yanshan University (Dissertation, P.R.C, 2009) [2] Taisheng Chen: Comparative Analysis and Research of RR, TR and NTR Upset-bending Processes for Heavy Crankshaft of Continuous Grain Flow.