Search results

Experimental Study on Compaction and Strength Characteristic of Wetland Fine Grained Soil Hongxia Yang School of Civil Engineering, Shandong Jiaotong University, Jinan, Shandong, 250023, China yanghongxia0531@163.com Keywords: Wetland, Fine grained soil, Compaction curve, Strength.
This paper through test study on the compaction and strength of several typical fine grained soil subgrade filler come from Ji-He expressway wetland soil field, discusses compaction characteristics of the fine grained soil under the condition of moisture content changes in a wide range,and change rule of compaction soil unconfined compressive strength and CBR value with the compaction work and moisture content.
Table 1 The fine grained soil physical property indexes No.
A large number of construction experience also shows, the moisture content is close to the optimum moisture content conditions,using made in China roller generally able to achieve the degree of compaction of the heavy standard, but for a higher moisture content over wet soil, it is difficult to achieve heavy standard requirements the degree of compaction.
[5] Hua Li.The Family of Compaction Curves for Fine grained Soils and There Engineering Behaviors.University of Alberta.2001

Motion of Grain Boundaries: Experiments on Bicrystals Dmitri A.
Grain shape evolution and rotation behavior of grains with pure tilt and mixed <100> low angle boundaries.
In order to analyze the effect of the inclinational anisotropy of grain boundary energy on the grain shape evolution and grain growth kinetics molecular dynamics (MD) simulations were employed.
The dislocation content of these boundaries, therefore, was not characterized by the invariant dislocation number, but rather by the constant dislocation density that preserved essentially the grain boundary structure.
Concurrent grain boundary motion and grain rotation.

Therefore, when the grain size of a polycrystalline aggregate is reduced, the fraction of atoms at structurally disordered sites increases while the number of atoms at perfect lattice sites decreases.
However, this number can be substantially increased to over 80% in what is referred to as grain boundary engineering.
It should be noted that the value of 0.48 B for site 1 does not significantly reduce the total moments associated with the 5 boundary, since Ni (1) sites constitute only a small portion of the total number of atoms in this boundary.
Note that the hardness values in this figure are given in units of Vickers Hardness Numbers (VHN).
The Taber wear index is usually given as a unitless number: the lower the Taber wear index the higher the material's resistance to abrasive wear.

At a strain of 0.8, an ultrafine equiaxed grained structure with mostly high angle grain boundaries was successfully obtained.
A combination of any two of the 12 variants gives rise to 5 different types (numbered as I-V in the present work) of high angle intervariant crystallographic interfaces/boundaries:, , , and forming through the variant selection mechanism during the martensitic phase transformation [10].
Similar to the mechanical twins formed inside the α' laths, a number of intervariant interfaces also had twin characteristics with the interface plane [12].
The newly formed refined grains had an average grain size of ~300 nm and their formation was found to be related to the alignment of α' laths with respect to the compression axis.
Closer microstructural examination around the strained laths (Fig. 3) revealed quite a number of low angle grain boundaries forming from the intervariant interfaces into the retained alpha laths.

The microstructure of 0°specimen are of equiaxed grain due to dynamic recrystallization after compression, while the grain shape of 45°and 90°specimens are still of lamellar grain structure.
Therefore, the dislocations concentrated near the grain boundary.
The propagation of dislocations to the matrix is easiest when the maximum shear stress in grain is parallel to longitudinal grain boundaries by applying the external stress in the 45° direction of elongated grain structure.
This could be attributed to the lamellar grain structures and the texture of the extruded bar. 2 The microstructure of 0°specimen are of equiaxed grain due to dynamic recrystallization after compression, while the grain shape of 45°and 90°specimens are still of lamellar grain structure.
Acknowledgements It is a project supported by natural science foundation of shanxi province China (project number: 2009011028-1; 2011011021-1).

This phenomenon is known from alloying element segregation to grain boundaries.
Here the hardening effect interferes with grain size strengthening.
The high-resolution capability of such analytical tools makes it possible to study small scale mechanical properties of individual grains, across grain boundaries and of selected areas, like precipitates and strongly deformed grains.
Twinning, as a form of plastic deformation, increases the number of interfaces (twin boundaries) and causes strain hardening, which leads to a hardness increase; see the value of 2.01 GPa in Table 3.
Although the extruded material is very fine grained, the scale of the indentation at the point where the first pop-in occurs is still smaller than the grain size.

The results showed that grain size and domain size were small before HT,there was  high-density dialocation in the alloy.After HT,grain size  increased, the internal stress, dislocation and other defects were reduced,magnetic domains became wider,the number of the domain decreased and the exchange energy between the magnetic domain reduced,leading to the decrease of the coercivity and increase of permeability.It was also found that the curie temperature was not changed after heat treatment.
As to the grain size, the large grain size is preferred due to the decrease of the coercivity [10,11].The grain size increased and the area of the grain boundary reduced after heat treatment, reducing moving resistance of the domain wall and increasing movable distances of the domain wall in grain.
The grain size increased after heat treatment, making the coercivity(Hc) lower.
(2) The number of domains  reduced with the domain becoming larger,the exchange energy between magnetic domains and the energy of magnetocrystalline anisotropy reduce, which reduced the coercivity and increased the magnetic permeability
Interactive Effect of Grain Orientation and Grain Size on Magnetic Properties of Fe–78 wt% Ni Ribbons.

For example, FSP of 99.999% aluminum leads to a minimum grain size of ~50 μm but much smaller minimum grain size of 3.5 μm is achieved in 99.99% aluminum [7].
FSP was conducted to investigate the minimum grain size of Al-0.01%Fe, which was compared with the grain sizes of other processed pure aluminums　[1-4, 7-8, 12-18].
A grain was defined an area surrounded by HAGBs, and the grain size (d) was defined the diameter of a circle with the same area as that of the grain.
However, the grain size remained almost unchanged over 1016 s-1.
Acknowledgements This work was supported in part by JSPS KAKENHI Grant Number 15K21294, the Light Metal Educational Foundation Inc., the Japan Aluminium Association, and the Nikki-Saneyoshi Scholarship Foundation.

Introduction Equal channel angular pressing (ECAP) is the representative model technique of severe plastic deformation (SPD) refining the grain size of metallic materials down to the sub-µm level, so called ultrafine grained (UFG) materials.
In the flat area, individual grain did not appear explicitly, and grain boundary sliding (GBS) hardly occurred across the boundaries.
The flat areas seemed to be agglomerates of grains having low angle boundaries.
In addition, a number of boundaries were well-defined, and showed sharp offsets of marker lines.
The deformation mode was changed from dislocation viscous glide to grain boundary sliding by additional rolling resulting in the development of larger portion of high angle grain boundaries. 3.

Commonly, the multidirectional forging to a strain of about 0.4 leads to the appearance of a large number of the strain-induced subboundaries with low-angle misorientations (q < 15°), which appear as deformation microbands (DMBs) and/or dense dislocation walls (DDWs) crossing over the original grains (Fig. 2).
The new grains are characterized by nearly equiaxed shape, with a mean grain size below 1 mm.
The formation of the new ultrafine grains occurs nearby the initial grain boundaries as well as along several DMBs/DDWs.
Such grains include the great number strain-induced boundaries with low-angle misorientations.
The corresponding grain size distributions are characterized by sharp peaks for the grains with sizes less than 2 mm (Fig. 3), which can be considered as DRX grains.