Search results

The statement is supported by the image at 15 minutes where microcaverns are already visible; - increasing the duration of the cavitation attack leads to the development of caverns, the size and number of which increases; - the shape of the caverns is trench-type, due to the breaking and expulsion of groups of fragile compounds, respectively of grains of the base metal; - starting from the 90th minute, the differences become more and more difficult to notice, which explains the decrease in the impact force, due to the damping effect of the water and air penetrated into them, during the contraction period of the sonotrode.
Intergranular cracks suggest the presence of impurities or secondary phases at the grain boundaries, which contributed to crack initiation and propagation.
Intergranular cracks indicate the presence of secondary phases (such as Mg2Si intermetallic compulsion) that have weakened the grain boundaries.
Conclusion Cavitation erosion of the WIG remelted surface structure of alloy 6082 presents typical structural degradation characteristics through complex mechanisms that include: - intergranular and transgranular cracking, suggesting the presence of impurities or secondary phases that weaken the material at the grain boundaries; - plastic deformation suggesting energy absorption before fracture; - breakage, predominantly ductile, indicated by the grainy texture and the presence of large cavities; - the eroded surface is very rough, with cavities that overlap and connect with each other, forming large and numerous cavities in the central area.
Demian, C., Ghera, Cavitation behavior study of the aging heat treated aluminum alloy 7075, Journal of Physics: Conference Series, (ICAS 2022), Open Access, Volume 2540, Issue 1, Article number 012037, Banja Luka, 25 May 2022 (2023)

At the same time, as can be seen from experiments [14 -16], close to surfaces there are sharp changes of the velocity and temperature fields at distances of the order of a grain diameter or less, stemming from the elevated porosity approaching the cubic-package value.
Moreover, the authors when trying to widen the range of the Reynolds number were increasing primarily the ball size instead of increasing the filtration velocity to cover a wide range of Reynolds number change.
Now determine the relation between Reynolds number and distances at which the viscosity is of importance.
The grain diameter or equivalent pore dimension can be used as a characteristic length scale in this law.
For moderate Reynolds numbers the packed bed core contribution should be taken into account.

Despite obvious valuable properties this material has a number of disadvantages that significantly limits the scope of application.
General information Fireresistance tests, carried by a number of researchers, have shown that UHPC matrix could be additionally hardened under temperature exposure of 150 to 300 ˚C [13-15].
Hence: - if Silica fume consumption at minimum (~ 5%) and Quartz powder consumption at maximum (~30 %) – distance between cement grains increases, lowering the role of pozzolanic reactions in dense structure formation, porosity of the crystalline phase also rises, which cause permeability growth; - if Silica fume consumption at maximum (~25%) and Quartz powder consumption at minimum (~10 %) – distance between cement grains increases due to the composition over-satiation with SF grains, which cause additional flocculation and increase amount of micro-defects under oven heat treatment
[18] Begunov O., Alexandrova O., Solovyov V., Studying of influence of fiber reinforcing at fine-grained concrete applying in transport construction / Begunov et al./ IOP Conference Series Materials Science and Engineering, 90 012016 (doi :10.1088/1755-1315/90/1/012016) (2017) [19] Caijun Shi, A review on ultra-high performance concrete: Part I.

Surface roughness depends on the thin film grain size which in turn depends on the cluster nucleation density [3], therefore SiC film quality can be controlled via managing nucleation process of SiC clusters on the Si surface.
Each process k (k = 1..n, where n is the total number of possible processes) is determined by the probability of realization of this process per unit time and occurs with rate Rk (s-1).
The activation energy for C atom diffusion depends on its local environment and can be represented as follows: Ed = Em + ΣlbEb + ΣliEi, (4) where Em is the migration energy for the carbon adatom, lb, li are the numbers of the nearest carbon and impurity atoms respectively and Eb, Ei are the bonding energy between C and Si atoms in SiC and between C and impurity atoms respectively.
The second term in the right side of the expression (4) takes into account that the bonding energy between Si and C atoms in the SiC cluster on the Si surface depends on the total number of the SiC molecules and hence the number of C atoms in the cluster.
In case of cluster edge diffusion of the carbon atom, i.e. the total number of the neighbors before and after the hop is the same, the edge diffusion rate R3 is equal to: R3 = υ∙exp(-Em /kbT)

However it does not implement the photolithograph process in the fabrication of pattern-less nanotubes but it needs to control the grain size of the metal catalyst to complete the fabrication of high density grown nanotubes.
Fig. 1 Illustration of CNT pattern Size Measurement Procedures Seven carbon nanotubes samples are used in the measurement tests; in which numbers 1–3 are high density pattern-less carbon nanotubes; their grown heights are 64µm, 80µm and 100µm respectively.
In Fig. 5, it is the spectral analyzer measurement result for the number 2 CNT (pattern-less CNT with 80µm height) while in Fig. 6, it is the spectral analysis result from the mirror-formed reflector.
From Fig. 5, it observes that when number 2 CNT is implemented as a reflector its reflected optical energy is quite small and it also suffers large noise interference.
The measurement results for numbers 1–3 CNTs are tabulated in Table 1, it shows that with grown heights of 64.3 um, 79.4 um and 96.8 um pattern-less CNTs they have the same return loss of 45 dB and this is equivalent to a reflectivity of 0.56%.

And Nf is the number of cycles to failure.
Glossy spots are seen on the fracture surfaces in both environments, though the number of glossy spots increases in hydrogen.
Furthermore, though Nf in hydrogen is less than that in nitrogen, the number of such grains with developed slip bands as indicated by arrows in Fig.6 in hydrogen is more than that in nitrogen.
Number of cycles to failure Total strain range ∆εt [ ]% → → → in air in H gas2 10 4 10 5 10 6 10 7 0.3 0.4 0.5 0.6 0.7 0.8 Fig. 1 ∆εt-Nf curve (a) in air enlargement of (A) (a) (b) (b) in hydrogen Fig. 3 Flat site on the fracture surface in hydrogen Fig. 2 Fracture Surfaces (a) (b) enlargement of (A) (c) enlargement of (B) in air (∆εt =0.57%, Nf=74500) (d) (e) enlargement of (D) (f) enlargement of (E) in
hydrogen (∆εt =0.56%, Nf=204000) Fig. 4 Ductile fracture surfaces in air and in hydrogen #2000 finished (A) L=0.1mm 0 50000 100000 150000 200000 0.1 1.0 10.0 in Air in H2 gas -1 Number of cycles N Crack length l [mm] in H2 gas -2 in N2 gas Loading axis Fig. 5 Crack growth plots.

The average area, average diameter, total number of cavities and surface roughness of sealed film are shown in Table 1.
The average area, maximal diameter and total number of cavities for boiling water sealing films is the biggest and these for sol is the smallest.
The average area, average diameter and total numbers of cavities in films sealed by Na2Cr2O7 and boiling water are bigger than unsealed films.
The total number of cavities for boiling water is most in per square millimetre, and it is least for sol sealing.
(2) Two-dimensional morphology shows: the surface of unsealed films consist of rounded grains, the one by sol have some raised bulk and the ones by sodium dichromate and boiling water appears round or oblong cavities

Because of its high production efficiency and material utilization, appropriate metal flow distribution and compact crystal grain, it becomes very important in modern manufacture.
A large number of tetrahedral elements were used for the billet in this simulation so that the material flow was well represented in the critical regions of the die cavity for more accurate design.
The advantage of performing simulations is that no tooling has to be built and the number of experimental tryouts can be significantly reduced.

（3）Complex admixture：slag,fly ash,natural mineral （4）Stone: 5mm～25mm gravel, crushed target of 4.8%, the grain shape is good, graded, in line with JGJ53-92 "concrete with crushed stone or gravel quality standards and inspection methods" requirements
Table 1 Concrete mixing ratio for sulfate erosion test Number concrete admixture sand stone water Superplasticizer M0 450 0 743 1027 170 1.5 M1,2 405 135 743 1027 170 1.5 The compressive strengt of the concrete has been testd according to GB/T50081-2002 "ordinary mechanical properties of concrete test method standards".
Table 2 Concrete test for sulfate erosion Number Compressive strength after 28ds’ standard curing (MPa) Compressive strength after 28ds’ immersing (MPa) Compressive strength after 56ds’ immersing (MPa) A B C A B C M0 64.1 68.8 64.6 61.2 74.9 72.8 68.7 M1,2 64.6 73.3 76.9 75.6 75.5 73.9 73.9 Results and discussion From Table 2 , the compressive strength of the concrete with admixture mineral and without admixture mineral has been compared after 28ds’ and 56ds’ immersing in water(A),5 % NaSO4 (B)and 5% MgSO4(C) solution,as shown in Figure 1 and Figure 2.

A number of methods have been developed for the preparation of Mg(OH)2 materials with different morphologies [7-9].
Nearly all diffraction peaks can be indexed as the hexagonal structure of Mg(OH)2 (JCPDS file number 7-239).
Moreover, the peaks of the samples are broadened due to the small grain size of the Mg(OH)2 particles.