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

More documents

Recommendations

Info

60 and the upper boundary was 18.5 mm above the corrugation peaks. The dilation in the boundary layer resulting from shearing during discharge gives rise to an overpressure. The overpressure is independent of silo scale causing a decrease in the relative overpressure with increased silo size. The shear zone in granular material has recently become the object of wider interest of researchers. The determination of the thickness of the shear zone is important for the estimation of forces transferred from the granular material to the structure. The thickness of the shear zones depends on the wall roughness, the grain diameter, the specimen size and the boundary value problem considered [160]. The relation between shear band thickness and grain size has profound implications for investigations of progressive failures within granular solids. According to direct experimental observations of Roscoe [143], the width of shear bands is about 10 times the average grain diameter. Investigations concerning the shear band formation are mainly based on computer simulations or theoretical modelling. The thickness of fully developed shear band was found to be approximately 16 times the mean grain diameter. Only a few researchers investigated experimentally the formation of the shear band in bulk of grain [109, 122, 177]. Triaxial compression tests [64] were performed to obtain information on the displacement distribution of particles inside the shear band. The sample was 30 cm high and 15 cm in diameter. The volume of the sample was divided into 30 cylindrical regions using two different colours of seeds: stained and not stained mustard seeds. Each region was 3 cm high and 3 cm thick. In the vertical direction the sample was divided into three cylindrical coaxial regions by inserting two cylindrical moulds of diameters of 3 cm and 9 cm into the sample mould. Layers of seed of 3 cm in height were poured into each of the three cylindrical regions of the sample. Ten layers of stained and not stained seed were poured into each column of the sample. Vertical cross-section of the sample of triaxial compression at ε 1 = 0.17 with the deformed meshes indicated is shown in figure 7.8. Orientation angle of the shear zone α and its thickness were also indicated in figure 7.8. The shear zone was oriented at an angle of: π ϕ (7-4) α = + 4 2 with the horizontal axis (direction of the minor principal stress σ 3 ) as predicted by the Mohr-Coulomb theory where φ is the angle of internal friction. Average value of the angle of internal friction for stained and not stained seed was 26 o . Distributions of displacement across the shear band, at axial strain ε 1 of 0.1 and 0.17, are shown in figure 7.9 and 7.10. Vectors connecting the line of original and deformed mesh represent the distribution of displacement across the
61 shear band. Vertical component of the vector, u ξ /D, represents the shear displacement, ∆L s , (related to grain diameter D) and horizontal component represents the normal displacement, ∆L n . The thickness of the shear band was determined from the width of the ramp in the η direction [64]. The thickness of the fully developed shear band was found to be 15 times the average grain diameter. A B C 12D α Fig. 7.8. Cross-section of mustard seeds sample deformed in triaxial compression test showing localization of deformation as shear band 1 0 A -2 0 -1 5 -1 0 -5 5 -5 5 1 0 1 5 2 0 2 5 3 0 3 5 40 -1 0 1 0 B -3 0 -2 5 -2 0 -1 5 -1 0 -5 5 5 1 0 1 5 2 0 2 5 3 0 -5 -1 0 1 0 C -3 0 - -2 0 -1 5 -1 0 -5 5 5 1 0 1 5 2 0 2 5 -5 -1 0 Fig. 7.9. Displacement distribution across shear band ε 1 = 0.1 [64]
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 38 and 39: 38 Fig. 3.17. Model of shear band f
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 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
Page 88 and 89: 88 a, b - product-dependent coeffic
Page 90 and 91: 90 also be performed as a function
Page 92 and 93: 92 reliable processing and stable v
Page 94 and 95: 94 unconfined yield strength to pow
Page 96 and 97: 96 The Chute Index (CI) is recommen
Page 98 and 99: 98 obtained the maximum deviation o
Page 100 and 101: 100 efficient flow control using op
Page 102 and 103: 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
Page 112 and 113:
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.
Page 118 and 119:
Page 120 and 121:
Page 122 and 123:
Page 124 and 125:
Page 126 and 127:
126 Table 16.16. Cont. 1 2 3 4 Icin
Page 128 and 129:
Page 130 and 131:
Page 132 and 133:
Page 134 and 135:
Page 136 and 137:
136 Table 16.25. Cont. 1 2 3 4 Icin
Page 138 and 139:
Page 140 and 141:
140 Table 16.29. Cont. Table sugar
Page 142 and 143:
Page 144 and 145:
144 Table 16.35. Mean values (± St
show all

Strona 2_redak - Instytut Agrofizyki im. Bohdana DobrzaÅskiego ...

Create successful ePaper yourself

Delete template?

Save as template?

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