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Showing 2 results for Joudaki


Volume 11, Issue 1 (6-2011)
Abstract

Residual stress measurement is one of the most interesting research areas in experimental mechanics. Residual stress is introduced to material due to plastic deformation of parts and can be one of the most effective parameters on design and operation of parts. ASTM E837-01 standard studies residual stress determination in parts by hole drilling method and represent calibration coefficients for flat sheets with constant stress profile. However, there is no certain standard on the residual stress measurement by Incremental Hole Drilling Method (IHDM) which is the subject of this study. IHDM can obtain stress profile by using two modified stress calibration coefficients. In this article, the stress calibration coefficients have been extracted for incremental hole drilling by using finite element analysis (FEA). FEA contains both biaxial tension test and pure shear test which a hole has been drilled step by step in the parts by removing elements and the strains changes were determined at three strain gauge positions on the surface. At last, the calibration coefficients are determined for each step and the accuracy of coefficients have been verified by a set of experimental test and a FE analysis. The experimental test contains four-point bending of an AA5056 flat aluminum sheet. The numerical analysis contains four-point bending of a flat sheet. In both cases, the stress profile can be determined easily by using analytical equations. Average analytical stress in each increment has been calculated and compared with the result of numerical incremental hole drilling method. The comparisons show that numerical and experimental results have no significant differences in first six steps but in the last four steps show an increasing errors due to the change in stress profile and hole geometry. Results presents that the calibration coefficients have suitable accuracy in stress profile determination.

Volume 16, Issue 88 (6-2019)
Abstract

Doogh is widely used as a healthy dairy product in Iran which is a suitable alternative to soft drinks in the society. Ginkgo biloba is an ancient plant species on earth which is also known as the living fossil. The leaves of these tree have several nutritional and therapeutic properties and therefore the Ginkgo­-­enriched doogh has a high nutritional value. In this study, the impact of the addition of Ginkgo­ extract at the levels of 0, 1, 2, 3 and 4 percent on some attributes plus the survival rate of probiotic bacteria containing 0.2 g/l shallot extract during 21 days of storage at the temperature of 4°C was explored. According to the results, by enhancing the concentration of Ginkgo­ extract, acidity, population of Lactobacillus acidophilus LA-5 and Bifidobacterium lactis Bb-12 plus the antioxidant activity and total phenol level were significantly enhanced (p<0.05). Also, with the increase in the level of Ginkgo­ extract, the sensorial score of the samples were reduced considerably (p<0.05). Storage of the samples during 21 days resulted in the reduction of Lactobacillus acidophilus LA-5 and Bifidobacterium lactis Bb-12 population as well as antioxidant activity, total phenol content and sensory acceptability considering odor,taste and color (p<0.05). Overall, the sample containing 2 g/l Ginkgo­ extract was selected as the best sample and can be prepared as a healthy product in the dairy industry.
 

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