Search results

There have been a large numbers of researches on the effect of porosity on the mechanical properties of sintered parts inevitably containing pore for a long time. [3~6] The majority of the researches were, however, focused on the parts made by conventional powder metallurgy mainly consisting of pressing and sintering, in which the systematic control of pore shape and microstructure is inherently difficult.
The specimen sintered at 900 o C corresponds to the adhesion stage of sintering; those sintered at 1000 and 1100 oC the initial stage, those at 1200 and 1250 oC the intermediate stage, and those at 1300 and 1350 o C the final stage. [13] It is interesting to not that discrete grains are evident in the specimens sintered at the temperatures of 1250 oC and above.
In a large number of investigations, equations relating the strength of a powder compact to its fractional porosity have been developed.
The initial porosity �i denotes the stacking structure, i.e. the number of the nearest neighbor powders.

Based on the assumption that the fatigue life to initiate a micro-structurally short crack, i.e. a crack with dimensions of few grain sizes, may be neglected, Dankert et al. [1] have proposed a calculation model describing both stages of the fatigue lifetime, i.e. mechanically short crack propagation till to technical crack initiation of approximately 1mm and stable long crack propagation, using the cyclic J-integral as a crack driving force parameter.
Specimen dimensions in [mm], notch concentration factors and material properties 103 104 105 106 107 50 100 150 200 250 300 350 400 S355J0G1 notch shape A stress ratio R=0 R=-1 R=-3 Number of cycles to total failure Nf Nominal stress amplitude Sn,a [MPa] (a) 10 3 10 4 10 5 10 6 10 7 50 100 150 200 250 300 350 400 stress ratio R=0 R=-1 R=-3 R=0,5 S355J0G1 notch shape B Number of cycles to total failure Nf Nominal stress amplitude Sn,a [MPa] (b) Fig. 2 Comparison of calculated and experimental fatigue lives for notch shapes a) A and b) B 10 3 10 4 105 10 6 10 7 50 100 150 200 250 300 350 400 S355J0G1 notch shape C Number of cycles to total failure Nf Nominal stress amplitude Sn,a [MPa] stress ratio R=-1 R=0 R=0.5 Fig. 3 Comparison of calculated and experimental fatigue lifetimes for notch shape C Fig. 2(a), 2(b) and 3 show the experimental Wöhler curves to

However, the existence of the Mg-Zn/Ca phase is not constant at the grain boundaries.
However, oxides discovered inside the grains may seem to prevent grain formation.
In addition, there was an increase in the overall number of pores produced.
The reinforcement of PLA polymer with co-doped HAp filler leads to an increase in the number of pores formed.
Meanwhile, the doped HAp has more consistent crystal formation and grain boundaries.

The paper affirms that, despite the number of works in the sludge neutralization of waste water containing heavy metal compounds, the proportion of their use remains marginal.
Their use, according to the results presented in Table 3 and Fig. 2, facilitates an increase of buckling coefficient and lower of grain density compared to control composition.
In this case the resulting gravel has characteristics: average density of grain - 450-500 kg/m3, the brand strength P 25, the mark for the packed density - 250.

It decomposes the mesh in different directions following the order of xyz into a specific number of domains according to user’s configuration.
Thus after being decomposed by Simple method, each of the domains still contains a very large number of cells.
The maximum total number of boundary vertexes is.
Figure 6 Decomposition time comparison Number of faces generated by the decomposition and percent of the max number of cells of all the domains above the average number can reflect quality of decomposition in the view of communication overhead and load balance [7].
A Coarse-Grain Parallel Formulation of Multilevel k-way Graph Partitioning Algorithm [C].

In contrast, the deposits via MLFS typically show a fine grained homogeneous microstructure [14] and a good bonding, where the roughness of the preliminary layer helps the mechanical anchoring [15].
Similar to findings by Shen et al. [14], the layers show a homogeneous and fine grained microstructure.
The etched cross section, extracted 55 mm from the beginning along the stack length, also reveals the area where the substrate material shows a grain refinement, indicating the thermomeachanically affected zone (TMAZ).
Along the stack height, the stud consumption islower, which is indicated by a decreasing deposit thickness and increasing length of the remaining consumable stud for an increasing number of MLFS layers, see Fig. 5(a).
For the investigated material combination, the results reveal a slightly less efficient deposition with increasing number of deposition layers, however, after a very limited number of layers, the MLFS depositions are uniform, i.e. a constant deposition rate is achieved.

Efficient and stress in relation with the number of buckets were studied in the work.
This has make them relevant materials for number of applications in airspace and other engineering industries.
Generally, mechanical properties of aluminium alloys and composites are reduced by coarse grain, cavities and needle shape eutectic silicon.
At the speed of 1500 RPM, the microstructure of the bucket experiences the following: transformation of large primary silicon into needle shaped eutectic silicon in the inner; long needle-shaped eutectic silicon are converted into fine primary silicon at the outer and; there is the formation of fine grain.
Kori, "Effect of Grain Refinement and Modification on the Dry Sliding Wear Behaviour of Eutectic Al-Si Alloys," Tribology International, vol. 42, pp. 59-65, 2009

For example, in order for a glass-ceramic to form a mechanically strong, adherent and hermetic seal to a metal or alloy a number of specific criteria must be met, as discussed below.
Both lithium zinc silicate, LZS, and lithium aluminosilicate, LAS, glass-ceramics have been successfully sealed to a number of different alloys at AWE [1, 3] in the manufacture of electrical feed-through components.
For example, Hong and Holland [8] noted that in the absence of a pre-oxidation stage glass-ceramic coatings on Nimonic 263 alloy were coarse grained.
On the other hand, pre-oxidation of the substrate yielded Cr in the Cr3+ oxidation state, which is considerably less mobile than Cr2+, and therefore reaction with P2O5 was avoided, resulting in a fine grained microstructure.
Internal oxidation and grain boundary attack of the metal components themselves may also occur during operation and this can cause swelling of the metal, leading to interface failure [36].

Research on Regulating the Effect of Different Mulching Measures on Root Spatial Distribution and the Root-Shoot Ratio of Maize Kexin Wang1,2,3a, Qiang Fu1,2b, Xin Jiang 4c Xiaoping Zhang 4d 1School of Water Conservancy & Civil Engineering, Northeast Agricultural University, Heilongjiang, Harbin 150030, China 2 Collaborative Innovation Center of Grain Production Capacity Improvement in Heilongjiang Province, Heilongjiang Harbin 150030, China 3Postdoctoral research station of Agricultural engineering in Northeast Agricultural University, Heilongjiang Harbin 150001, China 4Water Conservancy and Hydropower Survey Design Institute of Heilongjiang province, Heilongjiang Harbin 150001, China aemail: wangkexin0224@126.com, bemail: fuqiang100@371.net cemail:Jiangxin_0725@126.com, demail: Zhangxp@126.com Keywords: straw mulching; maize; root; root-shoot ratio Abstract:The effects of four types of mulching models (surface tillage with straw mulching, no-tillage with straw mulching
This mode has obviously promoted the root growth of maize, utilization efficiency of maize grain and water[1].
This experimental area is in a cold temperate zone continental monsoon climate area; therefore, it is cold and dry in the winter, windy and with less rainfall in spring, and warm and moist in the summer; the average temperature is 3.5°C, the average number of frost-free days is 135 d, the average sunshine duration is 2636 h, the average evaporation from the water surface is 796.3 mm, and the average annual precipitation is 545.7 mm.
(1) In these formulas, represent the root weight density (g·cm-3); represent the root weight density (g) of each plant in each layer of soil mass; n represents the total number of root of the jth plant; m represents measured plant number; and represents the soil volume (cm3). 2.4 Date Processing and Analysis The effects of the treatments on the root parameters were determined using a one-way analysis of variance by SPSS 11.0.
[5] Gao-bao Huang, Qiang Chai, Fu-xue Feng, Ai-zhong Yu.Effects of Different Tillage Systems on Soil Properties, Root Growth, Grain Yield, and Water Use Efficiency of Winter Wheat (Triticum aestivum L.) in Arid Northwest China.

Moreover, their formation occurs not on the grains of cement clinker, but on the particles of zeolite or in the pore space.
A number of researchers also pointed to an increase in porosity that occurs when unstable compounds with high molar volume are converted to stable compounds with lower molar volume as a major cause of strength loss.
During the hydration of the Portland cement mixture, the formation of needle crystals in the intergranular space is observed (Fig. 4b) covering the surface of individual grains.
The addition of zeolite-containing rock to Portland cement leads to the appearance of a large number of needle crystals of high-basic sulfoaluminate and calcium hydroaluminate.
At these ratios of fractions the optimum packing of grains of sand is reached.