Hydride-induced sub-critical crack growth in metals is simulated, by taking into account the coupling of hydrogen diffusion, hydride precipitation and material deformation. The terminal solid solubility of hydrogen in a stressed metal is derived analytically for hydrides of any shape with different elastic properties than those of the solid solution. The general relation considers full anisotropy of both hydride and metallic phases. It is shown that a hydrostatic stress plateau develops in the area of hydride precipitation near the crack tip, when crack propagates under conditions approaching hydrogen chemical equilibrium, near the threshold stress intensity factor. The plateau hydrostatic stress depends strongly on remote hydrogen concentration and temperature. However, it is nearly independent of the yield stress and the hardening of the metal. The same hydrostatic stress develops also behind the crack tip in the presence of hydrides. The characteristics of the near-tip field are used for estimating a critical remote hydrogen concentration, below which no hydride precipitation occurs, and the threshold stress intensity factor. The theoretical estimates compare favorably with experimental measurements.

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BackgroundThe purpose of this study was to evaluate the prevalence of Chlamydia trachomatis, Neisseria gonorrhoeae, Mycoplasma genitalium and Ureaplasma urealyticum infections in infertile men that consulted our outpatient departments using a novel simultaneous amplification testing (SAT) that is RNA-detection based. The possible impact of C. trachomatis, N. gonorrhoeae, M. genitalium and U. urealyticum infections on semen parameters was also noted in the present study.MethodsA total of 2607 males that were diagnosed with infertility were included in this study. C. trachomatis, N. gonorrhoeae, M. genitalium and U. urealyticum infections were detected in the urine samples using SAT method. Related data, including semen parameters and age as well as C. trachomatis, N. gonorrhoeae, M. genitalium and U. urealyticum infections were collected and analyzed.ResultsA total of 51 and 1418 urine samples were found positive for M. genitalium RNA and U. urealyticum RNA, respectively, while the prevalence of C. trachomatis and N. gonorrhoeae was relatively lower. Men with positive M. genitalium RNA and U. urealyticum RNA had higher sperm DNA fragmentation index (DFI) while the comparisons of other semen parameters yielded nonsignificant results between the RNA positive and negative group. A multivariate linear regression analysis revealed that U. urealyticum and M. genitalium infections posed significant factors of DFI (adjusted R2 = 46.2%).ConclusionsOur study suggested a relative high prevalence of U. urealyticum and M. genitalium infection based on this novel SAT detection method. U. urealyticum and M. genitalium infection could possibly impair male fertility potential through promoting sperm DNA damage.

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