Markov Chain Modelling of Reliability Analysis and Prediction under Mixed Mode Loading

The reliability assessment for an automobile crankshaft provides an important understanding in dealing with the design life of the component in order to eliminate or reduce the likelihood of failure and safety risks.The failures of the crankshafts are considered as a catastrophic failure that leads towards a severe failure of the engine block and its other connecting subcomponents.The reliability of an automotive crankshaft under mixed mode loading using the Markov Chain Model is studied.The Markov Chain is modelled by using a two-state condition to represent the bending and torsion loads that would occur on the crankshaft.The automotive crankshaft represents a good case study of a component under mixed mode loading due to the rotating bending and torsion stresses.An estimation of the Weibull shape parameter is used to obtain the probability density function,cumulative distribution function,hazard and reliability rate functions,the bathtub curve and the mean time to failure.The various properties of the shape parameter is used to model the failure characteristic through the bathtub curve is shown.Likewise,an understanding of the patterns posed by the hazard rate onto the component can be used to improve the design and increase the life cycle based on the reliability and dependability of the component.The proposed reliability assessment provides an accurate,efficient,fast and cost effective reliability analysis in contrast to costly and lengthy experimental techniques.

Alterations in myosin heavy chain isoform gene expression during the transition from compensatory hypertrophy to congestive heart failure in rats

Objective To explore the molecular mechanism underlying the decreased velocity of tension rise in rat myocardium during congestive heart failure (CHF) and left ventricular hypertrophy (LVH) induced by aortic stenosis.Methods The maximum velocity of tension rise (+dT/dtmax) was measured in left ventricular papillary muscle and the mRNA level of myosin heavy chain (MHC) isoforms in the left ventricle were detected by Northern blot analysis.Results The value of +dT/dtmax in CHF and LVH group were 64.17% and 37.15% lower than sham-operated controls (Sham) (P<0.01); values in the CHF group were 42.99% lower than that of LVH (P<0.01). The level of α-MHC mRNA in LVH was not different from that of the Sham (P>0.05), but decreased significantly in CHF to 42.3% of Sham and 56.1% of LVH (P<0.01). The level of β-MHC mRNA was up-regulated by 88.3% (P<0.01) in LVH compared with Sham and the level of β-MHC in CHF was 1.5-fold and 3.7-fold higher than that in LVH and Sham respectively (P<0.01). The ratio of α-MHC/β-MHC mRNA in LVH and CHF decreased to 42.4% and 9.8% respectively of the value in Sham (P<0.01). Correlation between α-MHC/β-MHC mRNA level and +dT/dtmax was analyzed which showed that these values were positively correlated with a correlation coefficient of 0.875 (P<0.01).Conclusion The decreased ratio of α-MHC/β-MHC mRNA was the major molecular mechanism underlying the decreased +dT/dtmax in CHF and LVH myocardium. The decreased ratio of α-MHC/β-MHC mRNA in LVH was mainly due to the up regulation of β-MHC mRNA while in CHF both down regulation of α-MHC and up regulation of β-MHC were involved.