THE USE OF MARKOV CHAINS THEORY FOR APPROXIMATION OF ATIGUE CURVE OF COMPOSITE MATERIAL
Some simple mathematical model for fatigue life of composite m aterial consisting mainly of parallel rigidd components (strands) is offered.. The model,, whi chh is foundedd onn the use of Markov chainn theory,, allows too get S-type curve of internal stress growthh and, finally,, too s ee the connectionn betweenn static strengthh distributionn parameters andd S-N fatigue curve (Wholer curve).. The model is tooo simple andd does not provide numerica l coincidence with experimental fatigue test data but by the use of some additional parameters we cann fit the model too actual fatigue datasets,, we can use it for nonlinear regressionn model of S-N fatigue curveandd predict consequence of static strengthh parameter changes.
Binomial version of Markov model of fatigue life of composite with two reasons for failure
Abstract A model of fatigue damage accumulation in laminate with two reasons for fatigue failure (the distortion of rigid items and the excessive yielding of the plastic part of the composite (matrix)) is offered. The model is based on the use of the Markov chains theory. It is shown how the corresponding transition probability matrix can be filled and how to calculate the mean time to failure, the variance of this time, and the probability distribution function. This model can be used as a nonlinear regression model for fatigue curve approximation and for fatigue damage accumulation description in program fatigue test. Processing of experimental data (fatigue test of carbon‐fiber reinforced laminate for fatigue curve building and for residual fatigue‐life investigation in program test with two levels of stress) shows that the model can be used for satisfactory description of the results of these tests. The specific feature of the model considered in this paper is the use of binomial distribution of failu...
Evaluation of Impact of Yarn Count and Stitch Length on Pilling, Abrasion, Shrinkage and Tightness Factor of 1 ? 1 Rib Cotton Knitted Fabrics
This study investigates the impact of yarn count and stitch length of 100% cotton knitted fabrics. 1 × 1 ribs structured fabrics were used in this research work. The stitch length 2.50 mm, 2.52 mm, 2.60 mm, 2.70 mm, 2.80 mm and 2.96 mm were used of the yarn count of 26Ne, 28Ne and 36Ne. The areal densities of the grey fabrics were in various amounts. The impacts of yarn count and stitch length were measured concerning pilling resistance, abrasion resistance, and shrinkage and tightness factor. The result showed that the fabric pilling grade decreased while number of cycle increased. Abrasion resistance decreased but length wise shrinkage increased despite the fact that the stitch length increased. The results also exposed that the tightness factor of the fabric increased with the increase of the stitch length in both dyeing and washing state and finished state compared to grey state for the yarn count 26Ne and homogeneous result not found for yarn count 28Ne and 36 Ne. Evaluation of Impact of Yarn Count and Stitch Length on Pilling, Abrasion, Shrinkage and Tightness Factor of 1 × 1 Rib Cotton Knitted Fabrics