Strona 2_redak - Instytut Agrofizyki im. Bohdana DobrzaÅskiego ...

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38 Fig. 3.17. Model of shear band formation according to Iwashita and Oda [72] 4. CLASSIFICATION OF GRANULAR MATERIALS The concept of granular material covers a very broad class of materials, beginning with farmaceuticals, cement and aspiration dust – through agricultural products, like e.g. cereal grain – food products, like flour, sugar, powder milk – to mineral raw materials, like e.g. gravel, stones and coal. For a variety of technological operations highly important is the wide array of such physical properties as bulk density, granulation, friction coefficient, hardness, moisture, explosiveness, sorptive and thermal properties. This creates the need for a coherent classification of such materials, to avoid the risk of errors and misunderstandings resulting from the omission of some material characteristic important for a given process. The properties of granular materials vary within a very broad range, depending on the origin of a material, the processes of production and processing applied, and on external factors and conditions. At present, two systems of classification of granular materials are most commonly used – CEMA and ISO [71]. The CEMA classifycation comprises bulk density, grain size, flowability, abrasiveness, and a number of other mixed characteristics. The ISO classification [71] is rather abbreviated – it comprises particle form, flowability, and several characteristics related to material transport and handling. The popular division of granular materials according to the mean grain size D includes the following classes [169]: dusty (e.g. aspiration dusts, fertilizer lime) D ≤ 0.05mm, powder (e.g. flour, fine meal) 0.05 < D ≤ 0.5 mm, granular (e.g. cereal grain) 0.5 < D ≤ 10 mm, nodular (e.g. gravel, wood chips) 10 < D ≤ 50 mm, lumpy (e.g. coal) 50 < D ≤ 300 mm, massive (e.g. unsorted stones) D > 300 mm.
39 Classification of materials according to the shape or form of grains, adopted by ISO [71], is as follows: sharp-edged, with three dimensions similar, sharp-edged, with one of the three dimensions clearly greater than the other two, sharp-edged, with one of three dimensions clearly smaller than the other two, round-edged, with the three dimensions similar, round-edged, with one of three dimensions clearly greater than other two, fibrous, stringy, curly, linked. The hardness of granular materials is most frequently assessed using the 10- grade Mohs scale. The particular grades of the scale correspond to the following: 1 – talcum, 2 – gypsum, 3 – calcite, 4 – fluorite, 5 – apatite, 6 – orthoclase, 7 – quartz, 8 – topaz, 9 – corundum and 10 – diamond. In this scale, cereal grain falls between grade 1 and 3 of hardness. Abrasiveness of granular materials is their ability to damage surfaces of equipment with which they are in contact as a result of movement over the surfaces. The degree of abrasiveness is related to the hardness, shape and size of the material grains. Chattopadhyay et al. [34] list four grades of abrasiveness of granular materials: mildly abrasive, moderately abrasive, extremely abrasive, very sharp, gouges soft materials like rubber. Flowability of granular materials is related to grain size and shape, surface properties, moisture, temperature, adhesion, cohesion, and mainly on consolidation time. ISO proposes a classification of materials according to their flowability that is based on the flow function ff introduced by Jenike [76]. The function will be discussed in detail in chapter 8. Chattopadhyay et al. [34] supplemented that classification with two extreme categories, proposing a division comprising six classes of materials: fluidlike flooding very free flowing ff > 10, free flowing 10 > ff > 4, average flowing 4 > ff > 2, poor flowing 2 > ff, sluggish/interlocked.
Page 2 and 3: EC Centre of Excellence AGROPHYSICS
Page 4 and 5: 4 9.3. Factors influencing the coef
Page 6 and 7: 6 BASIC NOTATION c - cohesion [kPa]
Page 8 and 9: 8 Numerous granular materials when
Page 10 and 11: 10 the tensor of plastic strain inc
Page 12 and 13: 12 Fig. 2.1. Yield curves with comp
Page 14 and 15: 14 Stable or unstable behaviour of
Page 16 and 17: 16 In turn, the model of Lade, also
Page 18 and 19: 18 same porosity need not have iden
Page 20 and 21: 20 where: A = ∫ E( β) sin βdβ
Page 22 and 23: 22 (β = 0 o ), positioning the out
Page 24 and 25: 24 grain was poured into the mould
Page 26 and 27: 26 axes of the ellipse characterizi
Page 28 and 29: 28 [176] for the determination of p
Page 30 and 31: 30 A different approach to the desc
Page 32 and 33: 32 where: I - moment of inertia, k
Page 34 and 35: 34 a) b) f s f s m M f n f n Contac
Page 36 and 37: 36 The micropolar model yields resu
Page 40 and 41: 40 In the case of agricultural mate
Page 42 and 43: 42 5.2. Density of consolidated mat
Page 44 and 45: 44 (cereal grain, sand, soil), the
Page 46 and 47: 46 Multiple wetting and drying of g
Page 48 and 49: 48 vertical pressure within the ran
Page 50 and 51: 50 of the curve defined by A, where
Page 52 and 53: 52 6. Vertical consolidation refere
Page 54 and 55: 54 poured into the box without vibr
Page 56 and 57: 56 7.2.2. Bulk density Stress-strai
Page 58 and 59: 58 near the box wall and lifted alo
Page 60 and 61: 60 and the upper boundary was 18.5
Page 62 and 63: 62 A -1 5 -1 0 -5 1 0 5 -5 5 1 0 1
Page 64 and 65: 64 Fig. 8.2. Yield locus and effect
Page 66 and 67: 66 in such a way that friction woul
Page 68 and 69: 68 a) b) µ = tg ϕw ϕ w c) d) e)
Page 70 and 71: 70 9.3. Factors influencing the coe
Page 72 and 73: 72 galvanized steel received from d
Page 74 and 75: 74 9.3.4. Velocity of sliding Becau
Page 76 and 77: 76 1+ sinϕ k = . 1 − sinϕ (10.3
Page 78 and 79: 78 N ϕ VLQϕ 3UHVVXUHUDWLRN
Page 80 and 81: 80 10.4.1. Friction force mobilizat
Page 82 and 83: 82 10.4.3. Moisture content With in
Page 84 and 85: 84 Table 10.1. Measured (k s ) and
Page 86 and 87: 86 conventional engineering analyse
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88 a, b - product-dependent coeffic
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90 also be performed as a function
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92 reliable processing and stable v
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94 unconfined yield strength to pow
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96 The Chute Index (CI) is recommen
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98 obtained the maximum deviation o
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100 efficient flow control using op
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102 In the field of experimental in
Page 104 and 105:
104 22. Britton M.G., Moysey E.B.:
Page 106 and 107:
106 69. Horabik J., Rusinek R.: Pre
Page 108 and 109:
108 114. Morland L.W., Sawicki A.,
Page 110 and 111:
110 158. 6WSQLHZVNL$ Influence of m
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112 16. APPENDIX - Physical Propert
Page 114 and 115:
114 16.2. Density and porosity Tabl
Page 116 and 117:
116 Table 16.7. Mean values (±St.
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126 Table 16.16. Cont. 1 2 3 4 Icin
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136 Table 16.25. Cont. 1 2 3 4 Icin
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140 Table 16.29. Cont. Table sugar
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144 Table 16.35. Mean values (± St
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