Breaking pharmaceutical tablets with a hole: Reevaluation of the stress concentration factor and influence of the hole size

Abstract

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Quantification of tablet sensitivity to a stress concentration: Generalization of Hiestand's approach and link with the microstructure

“…For the application of the generalized Hiestand's approach, a special set of flat faced Euro B tooling was used as described previously [20,27]. These tooling made it possible to obtained a so-called flattened geometry.…”

“…As described elsewhere [20], the holes in the tablets were inserted using a drill Micromot 50 E/EF (PROXXON S.A., Luxembourg). Three drill diameters (0.5, 0.8 and 1 mm) were used to make the holes.…”

“…As a consequence, results published in the literature are difficult to compare one to another. For this reason, we recently proposed to introduce a new index, calculated using different hole sizes, in order to generalize Hiestand's approach [20]. Using the average stress criterion introduced by Whitney et al [7], it was found possible to characterize the evolution of the strength of the tablet as a function of the hole size.…”

Finite Element Analysis and Modeling in Pharmaceutical Tableting

“…From these, 31.3% deal with the effect of punch shape [ 61 , 74 , 79 , 82 , 85 ]. The second most studied aspect (22.2% of the total) is the stress/strain distribution in the tablet during mechanical strength testing [ 65 , 81 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 ]. From these, 40% deal with the effect of tablet shape and studied crack propagation [ 89 , 90 , 92 , 93 ].…”

“…Croquelois et al (2017) [ 86 ] reevaluated the stress concentration factor (SCF) in the case of cylindrical and flattened tablets [ 81 ] with holes, during the diametral compression test, with the aid of FEA; 11-mm tablets were tested for two different materials: acetaminophen ( = 4.4 GPa, = 0.25) and spray dried lactose ( = 3.7 GPa, = 0.23). It was reported that the value of SCF was nearly independent of the hole size when the ratio of the hole and the tablet diameters was less than 0.1.…”