Search results

First, the finite element model of the SRM grain is established by using MSC.PATRAN.
The finite element model of the SRM grain According to symmetry of the loading and configuration, as shown in Figure 2, one-twelfth of an axisymmetric start of the motor grain is considered for the analysis.
Fig. 2 The radial and longitudinal section of SRM grain Fig.3 The regional 3-D finite element model of SRM grain and the debonded cracks in stress-release boot (b) Rear of the grain (a) Fore of the grain The SRM grain is a composite structure consisting of variety materials.
As shown in Fig. 5, 11 numbers of crack nodes are used over the crack foreside line.
Fig. 8 shows that one rear debonded crack with width 40mm and depth 16.5mm. 11 numbers of crack nodes are used over the crack foreside line, and crack 1, crack 2 and crack 3 correspond to the depth of 16.5mm, 27.0mm and 36.5mm to simulate the rear debonded crack growth.

The oxygen tracer diffused quickly from the surface up to the grain boundary and then appeared as discontinuous steps at the grain boundary.
They found that non-doped BaTiO3 contained a higher number of oxygen vacancies than the La-doped BaTiO3.
Neither grain boundaries nor grain segregation were observed in any of the images.
One of the possible reasons for the blocking behavior could be the lower number of effective oxygen vacancies around the grain boundaries, compared to those in the grains themselves.
That is, the effective number of oxygen defects is reduced because of the formation of such complex defects.

According to Eq.3, the contact pressure of each effective abrasive Pi is related directly to the number of abrasives involved in machining.
Usually, there are a lot of effective abrasive grains in the working area, and the number of them may be thousands or even more.
Normally, the contact pressure of a single abrasive grain Pi is very small.
Once some abnormal larger grains are interfused in polishing process, the number of abrasive involved in machining will be decreased sharply.
Maybe only hundreds of abrasive grains or even less are still active.

Fatigue cracks in ultrafine-grained structure develop both in the regions of larger grains and also in the fine grained areas.
The average grain size in the fine grained areas is 3.3 ± 0.5 µm whereas in the large grain areas the grain size is 9.9 ± 4.5 µm.
The shift in number of cycles to failure is nearly two orders of magnitude.
Cracked grain boundaries in fine grained area. σa = 180 MPa, N = 1.5 x 103 cycles.
In the case of UFG alloy, the number of slip bands rapidly decreases with decreasing stress amplitude.

It was found that a single grain was easily removed from the material.
The number of abrasive grains on the surface of the wheel was determined through observations using a microscope.
Furthermore, the numbers were evaluated by a calculation using the wheel particle frequency and the degree of concentration.
As a result, the number of abrasive grains on the surface of the wheel was assumed to be approximately 12,800 particles per square mm.
Figure 3 shows the value of Ft (<0.18 mN) on a single abrasive grain.

Introduction Nano-metals, defined as pure metals or alloys having grain size reduced to below 100 nm, have been a subject of extensive research which resulted in the development of a number of fabrication routes.
As a result, a number of SPD techniques, which allow obtaining unconventionally large strain, have been developed and successfully employed for grain size refinement in various metallic systems.
This was already proved for a number of metals and alloys and is illustrated in Fig. 1 for those processed by HE.
It should, however, be noted that the improvement in tensile strength was much more significant (580 MPa and 310 MPa for nano- and microcrystalline samples, respectively). 260 280 300 320 340 360 380 400 420 1.0E+04 1.0E+05 1.0E+06 1.0E+07 Number of cycles to failure Stress [MPa] nano- micro 0.00E+00 1.00E-08 2.00E-08 3.00E-08 4.00E-08 5.00E-08 6.00E-08 7.00E-08 8.00E-08 9.00E-08 1.00E-07 1 2 3 resistivity [ΩΩΩΩm] Fig. 3 Wöhler curves for micro- and nanocrystalline 2017 aluminium alloy Fig. 4 Resistivity of CuCrZr alloy: 1 - coarse grained, precipitation hardened, 2 - dislocation boundaries, 3 - fine grained Corrosion Resistance An important consequence of the reduced grain size is a significant increase in the surface area of the grain boundaries per unit volume of the alloy.
As the nano-grain structure is formed, the resistivity becomes only slightly higher than in coarse grain materials.

During cold rolling, the coarse-grained, random texture of the slab is transformed into the classical rolling texture of a fine-grained Al-alloy, with elongated Al-grains delimited by thin Sn-ribbons.
Grain growth within the original cold-rolled grains is fast, but once the recrystallised grain size reaches the length scale of the second-phase distribution, it slows down and both phases coarsen simultaneously, accompanied by a significant texture change.
Grains are often delimited on both sides by the Sn-ribbons, but often collections of smaller grains are present between two parallel ribbons.
In general, the appearance of “exotic” components such as M, b and c may be associated with local strain heterogeneities which are present in too small numbers to be observed in the recrystallised texture but, having originated at sites of higher stored energy may posses a size advantage when secondary recrystallisation is activated by the ongoing coarsening of the liquid Sn.
In: Recrystallisation and Grain Growth, Ed.

Grain size 0,5 µµµµm Fig. 3.
The alternation in temperature dependence of conductivity in different temperature ranges is well known and appears in a number of oxide materials, and is attributed to a change in the dominating charge transport mechanism.
As a comparison a number of results from previous research on polycrystalline alumina is shown.
Ref [11] undoped, average grain size 3 µm, relative density 99.5%.
Ref [16] MgO doped, average grain size 20 µm.

A large number of dimples are observed on the fracture surface, implying as ductile fracture.
It can also be seen that from the weld zone to the base metal, the number of LAGBs decreased gradually.
A large number of shear dimples were observed.
From the weld zone to the base metal, the number of low angle grain boundaries is gradually reduced.
In the 35J / mm sample, the number of low angle grain boundaries was about 0.29, and a large number of deformation twins can be formed during the deformation process, which has a great contribution to the strength of the weld.

Introduction Alumina ceramic has been found a wide application in a number of abrasive wear environments, such as in balls, mills, cutting tools, dies, and so on [1].
As an additive, La2O3 decrease grain sizes and improve ceramics density [7].
The micrograph clearly shows that grain sizes of ceramic samples with Tb4O7 doped are smaller than S1, and grains become bigger with increasing of Tb4O7.
And terbium ions in liquid phases could inhibit ions migration, which prevent grain growth and make grain sizes small, to improve wear resistant of ceramic samples.
Grain size effect on abrasive wear mechanisms in alumina ceramics.