Elastic and plastic deformation behavior analysis in small punch test for mechanical properties evaluation

In order to estimate deformation and mechanical properties of material accurately,elastic and plastic deformation behavior of small punch test was discussed in this paper.A two-dimensional finite element model was established based upon the Gurson-Tvergaard-Needleman(GTN)equation.According to the integration of load–displacement curves with different displacements,the evolution of elastic energy was obtained.The results show that the elastic energy increases quickly in the initial region and tends to be an approximate constant during the plastic bending phase.Meanwhile,an obvious change of the slope of load–displacement curve can be found in the elastic-plastic transition region.The macroscopic deformation and fracture feature were also discussed in order to verify the deformation analysis.Finally,the yield strength,tensile strength and elongation of AISI304 were obtained based on the analysis of deformation energy and percent fracture deflection.The results have a good agreement with that of conventional tensile tests,which may provide a theoretical basis of small punch analysis.

Elastic-plastic properties of thin film on elastic-plastic substrates characterized by nanoindentation test

To characterize the elastic-plastic properties of thin film materials on elastic-plastic substrates,a simple theory model was proposed,which included three steps:dimensionless analysis,finite element modeling and data fitting.The dimensionless analysis was applied to deriving two preliminary nondimensional relationships of the material properties,and finite element modeling and data fitting were carried out to establish their explicit forms.Numerical indentation tests were carried out to examine the effectiveness of the proposed model and the good agreement shows that the proposed theory model can be applied in practice.

Effect of Shoushen granule on arterial elasticity in patients with carotid atherosclerosis:a clinical randomized controlled trial

OBJECTIVE: To investigate the effectiveness of Shoushen granule,Chinese herbal preparation,on carotid artery elasticity in patients with carotid atherosclerosis.METHODS: The total of 156 carotid atherosclerosis patients were randomly divided into the intervention group(83 cases,treated with Shoushen granule) and the control group(73 cases,treated with pravastatin). Brachial-ankle pulse wave velocity(ba PWV) and Ankle-Brachial Pressure Index(ABI)were measured by automated arteriosclerosis detector. The changes of common carotid artery intima-media thickness(IMT) and parameters of the carotid artery elasticity in patients,including stiffness parameter(β),pressure-strain elastic modulus(Ep),arterial compliance(Ac),augmentation index(AI),and pulse wave velocity β(PWVβ) were detected by Echo-Tracking(ET) technique before and after 24 week treatment. In the meantime,levels of blood lipid,and liver and renal function were measured respectively.RESULTS: After 24 weeks,ba PWV,IMT and parameters of the carotid artery elasticity(β,Ep,AI and PWVβ) were markedly decreased in intervention group compared with those of before treatment(P < 0.01),but the level of Ac was increased significantly(P < 0.01). And there were no significant differences compared with control group on the same period(P > 0.05).CONCLUSION: In this pilot study,it was demonstrated ET technology and automated arteriosclerosis detector could be used to evaluate carotid artery elasticity effectively,and the action of Shoushen granule on carotid atherosclerosis might be related to the regulation of carotid artery elasticity.