Investigation on the Inspection Technology of GH3535 Alloy Butt Weld With Linear Array Probe

The critical problem to accurately characterizing defects in GH3535 alloy weld is the deflection of the acoustic beam and scattering due to the coarse columnar grains. Signal-to-noise ratio is an important index to indicate whether the grain scattering is severein the ultrasonic inspection. In this paper, the phased array ultrasonic testing of GH3535 alloy butt weld was studied using sector scan mode with linear array probe. The soundfield characteristics of the linear array probe with different focusing parameters were analyzed, and the signal-to-noise ratio in the detection was calculated. The results show that: the acoustic beam of the linear array probe can cover the weld,based on the removal of weld reinforcement. The signal-to-noise ratio of transverse hole with φ3mm located at the weld-fusion lineis more than 15dB, when the front end ofthe probe is located directly above the transverse hole of weld-fusion line.

FEM Simulation of Waves Excited by Array Probe Propagating in Centrifugally Cast Stainless Steel With Hexagonal Column

Centrifugally cast stainless steel (CCSS) is widely used in PWR primary coolant systems. However, ultrasonic testing for such material is very challenging because its coarse grains and anisotropic property. The phased array ultrasonic technology (PAUT) is considered the most promising solution to the problem mentioned. To improve the accuracy of PAUT for CCSS with columnar grains, we used the voxel-based finite element method to perform simulation of wave propagation in CCSS, where waves were excited by a linear array. We modeled columnar grains in CCSS with hexagonal columns and introduced a side-drilled hole. It was easily to have different inclined columnar grains by rotating the crystal axes. All column crystals were considered cubic crystals while CCSS with columnar grains was macroscopically transversely isotropic. Wave propagations were computed for different focal laws and their results were compared. Waves exactly propagated toward and focused at the targeted SDH when focal laws were calculated according to the anisotropic property of CCSS, but deviated the target for focal laws based on isotropy.

Alterations in MicroRNA gene expression profile in liver transplant patients with hepatocellular carcinoma

Background Hepatocellular carcinoma (HCC) can lead to liver failure which renders to liver transplant. miRNAs might be detected as biomarkers in subclinical stage of several hepatobiliary disorders like HCC. Therefore, in the present study, alterations in miRNAs as biomarkers were detected in LT patients with HCC. Methods Fourteen tissue samples composed of 5 rejected and 9 non-rejected ones were used for studying the miRNAs expression pattern using LNA-array probe assay and the result was evaluated by in house SYBR Green Real-time PCR protocols on 30 other tissue samples composed of 10 rejected and 20 non-rejected ones for the selected miRNAs. All samples were collected from liver transplanted patients with HCC. Results The study results revealed that in rejected patients compared to non-rejected ones, hsa-miR-3158-5p, -4449, -4511, and -4633-5p were up-regulated and hsa-miR-122-3p, -194-5p, 548as-3p, and -4284 were down-regulated. ROC curve analysis also confirmed that miR194-5p and -548as-3p in up-regulated and also, miR-3158-5p, -4449 in down-regulated microRNAs are significantly important molecules in rejection. Conclusion Finally, the tissue levels of specific miRNAs (especially hsa-miR-3158-5p, -4449, -194-5p and -548as-3p) significantly correlated with the development of HCC, which can be present as biomarkers after further completing studies.

Phased Array Ultrasonic Testing of Inconel 625 Produced by Selective Laser Melting

We investigate the use of phased array ultrasonic testing (PAUT) as an offsite non-destructive quality assurance technique for parts made by Selective laser melting (SLM). SLM is a popular additive manufacturing (AM) approach for fabricating high value metallic components with complex geometries. Slight variations in the laser power during fabrication might lead to internal defect development within the part, which could compromise its mechanical strength and fatigue life. PAUT is employed to detect typical internal porosity generated in Inconel 625 samples due to laser power fluctuation during SLM. The typical defect size, shape and distribution are first identified using metallography and X-ray computed tomography (XCT). B-scan images of the defect region is then generated experimentally using a 5 MHz linear UT phased array probe. Finite elements simulate wave propagation using geometries obtained from XCT images. The simulation results are compared to the experimental imaging of large defect regions and then used to generate total focusing method images of isolated clusters of 50-200 µm defects. The testing technique illustrates a successful application of PAUT for quality inspection of SLM parts.