Papers by Keyword: Dynamic Fatigue

Abstract: This paper carried out simulation analysis on the dynamic fatigue strength of an inline six-cylinder engine block based on the measured indicator diagram by the means of virtual prototype technology. A 3D solid model of the crankshaft block system is established firstly. After that, based on finite element method, dynamic stress of the block under operating conditions is obtained, by the means of Multi-body dynamics method. Then, calculation analysis on the fatigue safety coefficient of the engine block is made.

Abstract: Dynamic fatigue behavior of two kinds of Y-TZP ceramics was investigated at room temperature. The results showed that dynamic fatigue and slow crack growth behaviors exist in zirconias. Crack growth exponents of original and pre-cracked samples were obtained. Crack growth exponents of the two original zirconias are 15.60 and 21.00, respectively. Crack growth exponents of annealed pre-cracked samples are close to the original samples, indicating that the pre-crack experimental method is reasonable and effective. Because of the influence of residual stress indcued by indentation, crack growth exponents of unannealed samples are different from that of original samples. So residual stress should be removed.

Abstract: In this study, the dynamic fatigue characteristics of chemical starch-based ER fluid are experimentally investigated. A flow mode type apparatus is manufactured to activate the flow motion of the ER fluid. After evaluating the field-dependent Bingham property, three important dynamic fatigue characteristics; yield stress, current density and response time of the ER fluid are investigated as a function of the operating cycle. The dynamic operation for the flow motions is undertaken up to one million cycles and electric voltage is applied to the electrodes. In addition, the change of the particles of the ER fluid is microscopically observed to advocate the variation of the yield stress.

Abstract: Ultrafine hydroxyapatite (HA) and fluorhydroxyapatite (FHA) powders were synthesized and dense bioceramic samples were fabricated thereof. The samples were treepoint bend tested in different environments, i.e. in ambient air, distilled water and simulated human saliva, in the wide deformation rate range. Weibull’ statistics test was performed under standard testing conditions but in different media. The stress velocity exponent was evaluated from the dynamic fatigue testing data. The mean strength is shown to decrease when both ceramics are exposed to water or to simulated saliva. HA ceramics is more susceptible to the environment compared to FHA ceramics, due to the later is less subjected to the stress corrosion. Fracture surface observations revealed the crack propagation is of mixed trans- and intergranular mode. Strength distribution changes from uni-modal in air environment to bimodal in harsh conditions of water and saliva, indicating slow increment of flaw size in ceramics. Crack velocity exponent values correspond to transient region from dissociative chemisorption to ion solvation mechanisms of stress corrosion in both HA and FHA ceramics. Generally, FHA ceramics is considered to be much more reliable for application in bone defects replacement or dental reconstruction.