Surface grain refinement mechanism of SMA490BW steel cross joints by ultrasonic impact treatment

Ultrasonic impact treatment(UIT) is a postweld technique for improving the fatigue strength of welded joints. This technique makes use of ultrasonic vibration to impact and plastically deform a weld toe and can achieve surface grain refinement of the weld toe,which is considered as the main reason for the improvement of fatigue strength. In this paper,the microstructure of the surface of a treated weld toe was observed by metallographic microscopy and transmission electron microscopy(TEM). The results show that UIT could produce severe plastic deformation on the surface layer of the weld toe and the maximum depth of plastic deformation extended to approximately 260 μm beneath the treated surface. Repeated processing could exacerbate the plastic deformation on the surface layer,resulting in finer grains. We can conclude that the surface grain refinement mechanism of SMA490 BW welded joints is related to the high density of dislocation tangles and dislocation walls.

Screening for SH3TC2, PMP2, and BSCL2 Variants in a Cohort of Chinese Patients with Charcot-Marie-Tooth

Background： SH3TC2, PMP2, and BSCL2 genes are related to autosomal recessive （AR） Charcot-Marie-Tooth （CMT） disease type 1, autosomal dominant （AD）-CMTI, and AD-CMT2, respectively. Pathogenic variants in these three genes were not well documented in Chinese CMT patients. Therefore, this study aims to detect SH3TC2, PMP2, and BSCL2 pathogenic variants in a cohort of 315 unrelated Chinese CMT families. Methods： A total of 315 probands from 315 unrelated Chinese CMT families were recruited from the Department of Neurology of Third Xiangya Hospital and Xiangya Hospital. We screened for SH3TC2 pathogenic variants in 84 AR or sporadic CMT probands, PMP2 pathogenic variants in 39 AD or sporadic CMTI probands, and BSCL2 pathogenic variants in 50 AD or sporadic CMT2 probands, using polymerase chain reaction and Sanger sequencing. All these patients were out of 315 unrelated Chinese CMT families and genetically undiagnosed after exclusion of pathogenic variants of PMP22, MFN2, MPZ, GJB 1, GDAP1, HSPB1, HSPB8, EGR2, NEFL. and RABT. Candidate variants were analyzed based on the standards and guidelines of American College of Medical Genetics and Genomics （ACMG）. Clinical features were reevaluated. Results： We identified three novel heterozygous variants such as p.L95V （c.283C〉G）, p.L 1048P （c.3143T〉C）, and p.V 1105 M （c.3313G〉A） of SH3TC2 gene and no pathogenic variants of PMP2 and BSCL2 genes. Although evaluation in silico and screening in the healthy control revealed that the three SH3TC2 variants were likely pathogenic, no second allele variants were discovered. According to the standards and guidelines of ACMG, the heterozygous SH3TC2 variants such as p.L95V, p.LI048P, and p.V1105M were considered to be of uncertain significance. Conclusions： SH3TC2, PMP2, and BSCL2 pathogenic variants might be rare in Chinese CMT patients. Further studies to confirm our findings are needed.