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11.
针对熔化极气体保护电弧(gas metal arc,GMA)增材制造(additive manufacturing,AM)图像感知,提出一种透红外熔池视觉传感方法. 为客观评价熔池图像质量,综合图像灰度、纹理、形状和频谱等四类特征定义了熔池图像质量评价参数φ. 结果表明,φ值越大,图像质量越好. 透红外熔池图像质量评价参数φ远大于近红外窄带熔池图像,熔池更清晰,对比度更高. 相比800,850和930 nm等透红外滤光片,990 nm透红外滤光片能过滤大部分电弧连续谱和特征谱,获得的熔池信息量最大,对比度更明显,边缘更清晰,细节信息更丰富,熔池图像质量最佳,是最佳取像窗口. 相似文献
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Austenitic Fe-18Mn alloy was cyclically deformed at various total strain amplitudes. The structural changes induced by cyclic
straining in Fe-18Mn alloy were investigated by transmission electron microscopy. At a low strain amplitude of 0.4%, the formation
ofε-martensite associated with deformation twins and stacking faults was observed in this alloy. As the applied strain amplitude
was increased to 1.0%,α′-martensite embryos were induced in the alloy investigated. These embryos coalesce into a lath structure upon subsequent cyclic
deformation. 相似文献
15.
Polyvinylidene fluoride (PVDF) composites filled with in situ thermally reduced graphene oxide (TRG) and silver nanowire (AgNW) were prepared using solution mixing followed by coagulation and thermal hot pressing. Binary TRG/PVDF nanocomposites exhibited small percolation threshold of 0.12 vol % and low electrical conductivity of approximately 10-7 S/cm. Hybridization of TRGs with AgNWs led to a significant improvement in electrical conductivity due to their synergistic effect in conductivity. The bulk conductivity of hybrids was higher than a combined total conductivity of TRG/PVDF and AgNW/PVDF composites at the same filler loading. Furthermore, the resistivity of hybrid composites increased with increasing temperature, giving rise to a positive temperature coefficient (PTC) effect at the melting temperature of PVDF. The 0.04 vol % TRG/1 vol % AgNW/PVDF hybrid exhibited pronounced PTC behavior, rendering this composite an attractive material for making current limiting devices and temperature sensors. 相似文献
16.
H Irie H Honda T Kuroiwa K Hanada K Yoshimitsu T Tajima M Jimi K Yamaguchi K Masuda 《Canadian Metallurgical Quarterly》1998,22(4):651-655
PURPOSE: The purpose of this work is to describe the findings on MRI in patients with groove pancreatitis, a specific form of chronic pancreatitis affecting the groove between the pancreatic head, the duodenum, and the common bile duct. METHOD: MR images, including MR cholangiopancreatography, of five patients with groove pancreatitis were reviewed. Three patients underwent pancreatoduodenectomy due to serve duodenal stenosis, and the MR findings were compared to the histologic findings. RESULTS: A sheet-like mass was demonstrated between the pancreatic head and the duodenum in all patients. The masses were hypointense relative to pancreatic parenchyma on T1-weighted images and iso- to slightly hyperintense on T2-weighted images. After administration of Gd-DTPA, the masses showed delayed enhancement. Histologically, fibrous scar tissue was detected in the groove. CONCLUSION: MR images can clearly demonstrate the fibrous tissue in the groove in groove pancreatitis, and MR cholangiopancreatography can also provide useful information. 相似文献
17.
Sie Chin Tjong 《国际钢铁研究》1988,59(11):499-502
Austenitic Fe–29.7Mn–8.7Al–1.04C and duplex Fe–29Mn–10Al–0.4C alloys were exposed to the SO2–O2 mixed gas environments at 900 °C. The morphology of the scales formed on these alloys under oxidizing-sulfidizing conditions were examined by SEM and X-ray mapping techniques. The results showed that the addition of carbon up to 1 wt.% to the Fe–29.7Mn–8.7Al–1.04C alloy led to the formation of internal sulfidation and intergranular oxidation in the mixed oxidant gas environments. On the other hand, no evidence of intergranular oxidation could be detected in the duplex Fe–29Mn–10Al–0.4C alloy with lower carbon concentration. 相似文献
18.
Sie Chin Tjong 《国际钢铁研究》1989,60(2):91-94
A short-time hot corrosion test was performed on the austenitic Fe-29.7Mn-8.7Al-1.04C alloy in sodium sulphate at 900°C. The corrosion scales formed on the alloy investigated were studied by scanning electron microscopy and X-ray mapping techniques. The hot-corrosion scales morphology of the austenitic Fe-29.7Mn-8.7Al-1.04C alloy were characterized by the formation of Al2S3 and α-MnS sulphides at and beneath the internal alumina scale. No fluxing of the scales was observed. The effect of the addition of sodium chloride to the fused sodium sulphate on the hot corrosion scales morphology was also investigated. 相似文献
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A dilatometric technique was used to explore the tensile deformation mechanisms of polystyrene (PS)/high‐density polyethylene (HDPE) blends compatibilized by a styrene–ethylene–butylene–styrene (SEBS) triblock copolymer. The volume change of the sample during a uniaxial tensile process was determined with two extensometers, and it provided useful information concerning the tensile deformation mechanism. A simple model was used in this study in order to obtain quantitative information on the separate contributions of several possible deformation modes to the total deformation. The results indicated that elastic deformation was the main deformation mode for PS. However, elastic deformation was the main mode of deformation prior to yielding for SEBS compatibilized PS/HDPE blends; thereafter the plastic deformations (including shear and crazing) appeared to dominate over the elastic deformation. Moreover, crazing was the main plastic deformation mode for the blend containing 20 wt % HDPE, and shear deformation became predominant when the HDPE content was further increased. Finally, the essential work concept was used to determine the fracture toughness of the typical ductile PS/HDPE/SEBS 10/80/10 blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2024–2033, 2000 相似文献