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1.
本文应用慢应变速率拉伸试验法、金相和扫描电镜技术研究了带焊缝的A3钢试样在会缓蚀剂的盐酸溶液中的氢致腐蚀裂开行为。结果表明,在酸液中带焊缝试样的断裂均发生在热影响区;带焊缝A3钢试样的脆断敏感程度显著高于其母材;缓蚀剂的添加可以较大程度地改变带焊缝材料的脆断敏感性。 相似文献
3.
本文利用声电匹配和聚焦声透镜技术,研制出1,15MHz高灵敏度、高分辨率空气超声传感器。设计了单片机信号采集、处理、控制软硬件系统和纠偏执行机构。首次实现扫描式、固定式超声传感二维自动跟踪,跟踪精度横纵向均达到0.5mm。 相似文献
4.
5.
T. Karthikeyan Arup Dasgupta S. Saroja M. Vijayalakshmi 《Journal of Materials Engineering and Performance》2005,14(2):241-248
The successful replacement of the present generation of corrosion-resistant materials (nitric acid-grade stainless steel and
Ti) by Ti-5Ta-1.8Nb, which has better corrosion resistance, depends on its weldability characteristics. This article presents
the results of a study on the fabrication, qualification, and microstructural characterization of the welds. Welding was carried
out using the direct current electrode negative (DCEN) polarity tungsten inert gas (TIG) (manual) welding method with high-purity
Ar shielding. Testing was carried out as per the ASME standard (section IX, welding and brazing). Qualification tests found
that the weldment met the required properties. The weldment showed heterogeneous microstructures, which are rationalized based
on differences in phase transformation mechanisms that are dictated by the thermal cycles experienced by various microscopic
regions. The results, described in this article, confirm that the weldability of the developmental Ti-Ta-Nb alloy is excellent.
A preliminary evaluation of the corrosion behavior of the welds showed rates comparable to that of the base metal, establishing
that this alloy could be considered as an alternative material for use in highly corrosive environments. 相似文献
6.
Y. M. Zhang T. K. Tan Z. M. Xiao W. G. Zhang M. Z. Ariffin 《Fatigue & Fracture of Engineering Materials & Structures》2016,39(4):453-466
Corrosion is an electrochemical process in offshore pipelines where the material strength begins to decrease as corrosion advances. Numerous studies have been performed to determine the remaining strengths (failure pressure) of corroded pipelines. Currently the axial corrosions of the girth welded pipelines still leave much to be understood. This study attempted to simulate girth welded pipeline with various corroded depths and lengths in order to compare with offshore pipeline design manuals. Based on the numerical results, the influence of corrosion defects parameters on remaining strengths were investigated for girth welded pipelines. The investigation on the effect of strength mismatch revealed that in the cases of under‐matched, higher failure pressures are obtained. Comparisons of current results with B31G‐2012 and DNV‐RP‐F101 demonstrated that both codes may produce somewhat conservative predictions on the failure pressure. Furthermore, an equation was proposed to evaluate the corrosion progress across girth welded pipelines. 相似文献
7.
Moritz Braun Robert Scheffer Wolfgang Fricke Sren Ehlers 《Fatigue & Fracture of Engineering Materials & Structures》2020,43(2):403-416
Ships and offshore structures may be operated in areas with seasonal freezing temperatures and extreme environmental conditions. While current standards state that attention should be given to the validity of fatigue design curves at subzero temperatures, studies on fatigue strength of structural steel at subzero temperatures are scarce. This study addresses the issue by analysing the fatigue strength of welded steel joints under subzero temperatures. Although critical weld details in large welded structures are mostly fillet‐welded joints, most published data are based on fatigue crack growth rate specimens cut out of butt‐welded joints. This study analyses fillet‐welded specimens at ?20°C and ?50°C against controls at room temperature. Significantly higher fatigue strength was measured in comparison to estimates based on international standards and data from design codes even at temperatures far below the allowed service temperature based on fracture toughness results. 相似文献
8.
This research deals with the service evaluation of a retired CrMoV steel rotor that has been repaired using deep groove multi‐pass submerged arc welding (SAW) and gas tungsten arc welding (GTAW). Accelerated creep tests were conducted at several elevated temperatures and extrapolated to the service temperatures. The coalescence of carbides and cavity growth during creep were evaluated. For the CrMoV‐GTAW samples, it was found that the creep life depended on the location of the crossweld in the welded specimen. The service lives of the weldments were extrapolated. 相似文献
9.
TC21钛合金电子束焊接接头超高周疲劳行为研究 总被引:3,自引:0,他引:3
采用超声疲劳试验方法(20 k Hz),研究TC21钛合金电子束焊接接头的超高周疲劳性能与断裂机理。结果表明,TC21钛合金电子束焊接接头的疲劳性能要远低于母材的疲劳性能。在短寿命阶段,电子束焊接接头和母材的疲劳裂纹均在表面萌生;当寿命增大时,两者疲劳裂纹的萌生位置均由表面转向内部,母材的疲劳裂纹主要萌生于内部显微组织,而电子束焊接接头疲劳裂纹主要萌生于内部焊接气孔缺陷。当寿命较长时,疲劳源区会出现"鱼眼"形貌特征,源区附近有白色颗粒状细晶区,即细晶区(Fine granular area,FGA),其应力强度因子在2.90~3.33 MPa·m1/2,与疲劳寿命没有直接关系,可以认为是疲劳裂纹扩展门槛值。此外,基于AKINIWA小裂纹扩展理论,定量分析气孔尺寸与TC21焊接接头疲劳极限、疲劳应力的关系。 相似文献
10.
This paper deals with the influence of post-weld heat treatment (PWHT) of T92/TP316H martensitic/austenitic transition weldment on the resulting microstructure and creep characteristics. Experimental weldments were fabricated by gas tungsten arc welding using a nickel-based weld metal (Ni WM). After the welding, two individual series of produced weldments were heat-treated according to two different PWHT procedures. The first “conventional PWHT” was carried out via subcritical tempering (i.e. bellow Ac1 temperature of T92 steel), whereas the other one, the so-called “full PWHT” consisted of a complete reaustenitization of the weldments followed by water-quenching and final tempering. The use of “conventional PWHT” preserved microstructural gradient of T92 steel heat-affected zone (HAZ), consisting of its typical coarse-grained and fine-grained subregions with tempered martensitic and recrystallized ferritic–carbidic microstructures respectively. In contrast, the “full PWHT” led to the complete elimination of the original HAZ via transformation processes involved, i.e. the reaustenitization and back on-cooling martensite formation. The observed microstructural changes depending on the initial PWHT conditions were further manifested by corresponding differences in the weldments’ creep performance and their failure mode. The weldments in “conventional PWHT” state ruptured after long-term creep tests by premature “type IV failure” within their recrystallized intercritical HAZs. On the contrary, the long-term creep behavior of the weldments processed by “full PWHT” was characterized by their remarkable creep life extension but also by the occurrence of unfavorable “decohesion failure” along T92/Ni WM interface. 相似文献