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

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102 In the field of experimental investigations, new measurement methods have been elaborated and known methods have been improved to interpret unclear phenomena or to facilitate strenuous and time consuming measurement procedures. Regarding determination of strength parameters of granular materials, Jenike method [74] has been widely accepted and standardized in many national design codes as well as in international Eurocode 1 [50]. From among numerous earlier elaborated instruments, the ring shear tester will probably gain the position of recognized measurement technique. It is particularly useful in investigations of food products and granular plant materials. Because of high deformability of particles these materials require long shearing path to reach steady flow, and deformation in the ring shear apparatus is unlimited. The second significant advantage of the ring shear apparatus is the possibility of examinations under low level of normal load. Vertical loading force related to the relatively large surface of lateral section of the channel of the apparatus gives low values of normal pressure. Description of mechanical behaviour of granular materials under low normal load (in thin layer) is currently in particular interest of industrial practice. The two advantages of the ring shear tester open new fields of its application as well as promise the possibility of interpretation of some phenomena that still remain unclear. Two other old methods for the measurement of angle of repose and of angle of friction with inclined table will probably remain as standards for the determination of mechanical properties of granular material thanks to their simplicity. Search for methods of examination of product quality and for quality indices has been a symptomatic trend of technology of granular materials in the last several years. Quality assessment in the sense of granular mechanics means the determination of material flowability. Within the approach of Jenike [74] that is recently widely accepted the measure of flowability is the flow function II 1 c (1 1 ), i.e. the relationship between unconfined compression strength and major consolidation pressure. The direct shear tester or the Jenike method has, however, some disadvantages pointed out by practitioners. Testing is tedious and time consuming, while elaboration and interpretation of results require significant knowledge. Industrial practitioners demand a quick and simple method with an unmistakable and intelligible quality index. Academic laboratories and consulting firms put their propositions on the market one after the other, but none of them gained wide acceptation till now. Probably, for process engineering the set of Johanson’s indices has been accepted, while in the pharmaceutical industry Carr indices are commonly used.
103 14. REFERENCES 1. ACI 313-91. Standard practice for design and construction of concrete silos and stacking tubes for storing granular materials. American Concrete Institute. Box 19150 Redford Station. Detroit Michigan 48219, 1995. 2. Allen J.R.L.: Notes towards a theory of concentration of solids in natural sand. Geological Magazine, (106) 4, 309-321, 1969. 3. ASAE Standards, D241.4: Density, specific gravity, and mass-moisture relationships of grain for storage. St. Joseph, MI, ASAE, 1999. 4. ASAE Standards, EP433. Loads exerted by free-flowing grain on bins. St. Joseph, MI, ASAE, 1999. 5. ASAE Standards, D272.3 MAR96. Resistance to airflow of grains, seeds, other agricultural products and perforated metal sheets. ASAE Standards 1997, 532-538, 1997. 6. ASAE Standards, D274.1 FEB03. Flow of grain and seeds through orifices. ASAE Standards 2003: 576-578, 2003. 7. ASTM – D6393 Standard Test Method for Bulk Solids Characterization by Carr Indices. American Society for Testing and Materials, West Conshohocken, PA, 1999. 8. ASTM – D4781 Standard Test Method for Mechanically Tapped Packing Density of Fine Catalyst Particles and Catalyst Carrier Particles. American Society for Testing and Materials, West Conshohocken, PA, 2000. 9. ASTM – D6128 Standard Test Method for Shear Testing of Bulk Solids Using the Jenike Shear Cell. American Society for Testing and Materials, West Conshohocken, PA, 2000. 10. AS 3774-1996. Loads on bulk solids containers. Standards Australia. 1 The Crescent, Home bush, NSW 2140, 1996. 11. Balassy Z., Horabik J., Molenda M.: On friction properties of wheat grain. Zesz. Probl. Post. Nauk Roln., 378, 11-19, 1989. 12. Bardet J.P., Proubet J.: Adaptative dynamic relaxation for statics of granular materials. Computers and Structures, 39(3/4), 221-229, 1991. 13. Bardet J.P., Proubet J.: Shear-band analysis in idealized granular material. J. Enene Mechanics, 118(2), 397-415, 1992. 14. Bathurst R.J., Rothenberg L.: Micromechanical aspects of isotropic granular assemblies with linear contact interactions. Journal of Applied Mechanics, 55(1), 17-23, 1988. 15. Bednarski T.: Mechanics of plastic flow (in Polish). PWN, Warszawa, 1995. 16. Bell T.A., Ennis B.J., Grygo R.J., Scholten W.J.F., Schenkel M.M.: Practical Evaluation of the Johanson hang-up indicizer. Bulk Solids Handling, 14(1), 117-125, 1994. 17. Bickert W.G., Buelow F.W.: Kinetic friction of grains on surfaces. Trans. of the ASAE, 9(1), 124- 129, 1966. 18. Bijnen F.G.C., H. van Aalst, Baillif P.Y., Blonk J.C.G., Kersten D., Kleinherenbrink F., Lenke R., van der Stappen M.L.M.: In-line structure measurement of food products. Powder Technology, 124, 188-194, 2002. 19. Blau P.: The signifficance and use of the friction coefficient. Tribology International, 34, 585-591, 2001. 20. Blair D.L., Mueggenburg N.W., Marshal A.H., Jaeger H.M., Nagel S.R.: Force distributions in three-dimensional granular assemblies: Effects of packing order and interparticle friction. Physical review E, 63, 041304, 1-8, 2001. 21. Bowden F.P., Tabor D.: Introduction to tribology (in Polish). Warszawa, WNT 1980.
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EC Centre of Excellence AGROPHYSICS
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4 9.3. Factors influencing the coef
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6 BASIC NOTATION c - cohesion [kPa]
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8 Numerous granular materials when
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10 the tensor of plastic strain inc
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12 Fig. 2.1. Yield curves with comp
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14 Stable or unstable behaviour of
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16 In turn, the model of Lade, also
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18 same porosity need not have iden
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20 where: A = ∫ E( β) sin βdβ
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22 (β = 0 o ), positioning the out
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24 grain was poured into the mould
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26 axes of the ellipse characterizi
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28 [176] for the determination of p
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30 A different approach to the desc
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32 where: I - moment of inertia, k
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34 a) b) f s f s m M f n f n Contac
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36 The micropolar model yields resu
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38 Fig. 3.17. Model of shear band f
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40 In the case of agricultural mate
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42 5.2. Density of consolidated mat
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44 (cereal grain, sand, soil), the
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46 Multiple wetting and drying of g
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48 vertical pressure within the ran
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50 of the curve defined by A, where
Page 52 and 53: 52 6. Vertical consolidation refere
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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)
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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 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 126 and 127: 126 Table 16.16. Cont. 1 2 3 4 Icin
Page 136 and 137: 136 Table 16.25. Cont. 1 2 3 4 Icin
Page 140 and 141: 140 Table 16.29. Cont. Table sugar
Page 144 and 145: 144 Table 16.35. Mean values (± St
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