Shear Index Research Articles

割線入り錠剤の分割性と粉体の力学的特性値との関係

The relationship between dividing properties of the scored tablet and dynamic characteristics of the powder was investigated for proving the effects of physical characteristics of the powder on dividing properties of the scored tablet. Lactose, microcrystalline cellulose, corn starch, synthetic aluminum silicate and Perfiller were used as excipients. The dynamic characteristics of the powder, such as tensile strength (T), cohesive force (C), angle of friction (delta), flow factor (FF), shear index (n), C/T(K) and constants of Kawakita's equation of tapping compaction (a, 1/b) were measured. No correlations between coefficient of variation of divided tablet weight and each dynamic characteristics of the powder were found. However, from the result of the multiple regression analysis, multiple regression equation containing C and a as variables was obtained. Then a significant correlation was obtained between coefficient of variation of divided tablet weight and C/a, and also between logarithms of dividing strength of scored tablets and C/a. As a result, coefficient of variation of divided tablet weight decreased and dividing strength of scored tablets increased with decreasing C/a value.

INVESTIGATION OF INDEXES CHARACTERIZING GROUND MOVEMENTS ABOVE SHALLOW TUNNELS IN DILUVIAL SAND

To predict the following ground movement and detect the failure of the ground, it is important to assess ground conditions at that time based upon field measurement results as possible as we can.From the experiences of nine shallow tunnels' excavation through diluvial sand, three indexes termed Simple shear strain, Moment index, and Shear index which are based upon the assumption that the ground above a shallow tunnel behaves as a kind of a continuous beam along tunnel alignment and transversally, characterize the settlement behaviour of the ground associated with tunnel advance as well as error function curve determines the shape and characteristics of transversal settlement trough.

引っ張り・圧縮両垂直応力範囲における粉体層破壊包絡線の測定

A new type shear tester has been developed to obtain the yield loci under the normal stress ranging from positive to negative containing the adhesion force. This apparatus is characterized by the fact that the direction of the failure plane to the normal stress axis at the fracture by tensile stress is identified with the shear plane. By using this apparatus, the yield loci of several powders were measured. These results are summarized as follows:1) An adequate correlation is recognized on the relationship between the flow index and the shear index.2) The adhesion force obtained with this tester is larger than that with the split cell. From these results, it is estimated that the normal stress acting on the failure plane in this tester is larger than that in split cell.3) The family of yield loci obtained at various pre-consolidation stresses can be coincided with each other by means of using the reduced stress defined by the shear stress, and the sum of the normal stress and the adhesion force divided by the sum of the pre-consolidation stress and the adhesion force.

The failure properties od some “simple” and “complex” powders and the significance of their yield locus parameters

A study has been made of the failure properties of lactose, calcium carbonate and ultramarine. Narrow size fractions of the materials behave as “simple” powders: the angle of internal friction Δ, the shear index n, and the specific cohesion p″ and tensile strength q″ remain independent of packing density. Mixtures containing two different size fractions of the same material or similar size fractions of two different materials behave as “complex” powders. Three different types of “complex” powder can be distinguished by the way in which one or more of the above parameters vary with their packing density. Δ is a convenient single parameter for assessing the failure properties of the “simple” powders and of two of the types of “complex” powders. The significance of Δ and of the other parameters is discussed in terms of the forces that act between the particles in the powders.

Cohesion and tensile strength of bulk solids

For both cohesion and tensile strength it is apparent that a correlation exists between the strength of the bed; whether this is due to surface tension forces or other, and its state of packing i. e. eq. [5] and [6]. Further more it has been established both in this and other work (24), (32) that the state of packing may be correlated with the imposed normal stress i. e. eq. [4]. It is possible therefore, that a simple consolidation test will give an estimation of the comparative ease of flow of powders. If more precise information is required the tensile strength determinations can be carried out and approximations of cohesion calculated. For a complete description of powder properties however it is advisable to determine the shear strength in addition to the tensile strength in that the shear index and yield loci can be more accurately determined. More variables need to be studied before an expression of the form of eq. [2] can be used universally. One approach is to start with a simple system (32) and build into it known variables such as moisture, as in these experiments, particle size (23) shape, density, chemical constitution etc.

Warning to Pharmacists

Rutting indicators of asphalt mixtures were evaluated using wheel tracking testing results of AC-13 and AC-20 asphalt mixtures. A short term rutting period of 2520 cycles could be adequate for simulating heavy traffic and for prediction of long term rutting. Secondary rutting based indicators had higher rutting correlation coefficients than primary rutting based indicators (PRBI). The reliability of PRBI indicated that mixtures could be characterised based on primary rutting. The rutting at 2 cycles could be used for quick rutting prediction, but since the earliest recorded cycle was 2, it was hypothesised that even one cycle could as well be equally significant. A/C index, complex stability index and shear index were the most reliable indicators based on validating results of recycled hot mix asphalt mixtures. However, only A/C index could reliably screen mixtures with nearly the same secondary rutting rates. It was considered the best indicator, which could as well assess the performance of indirect rutting indicators. Its limiting mixture design values could be determined and validated.