Investigation of Microstructure and Mechanical Properties of High-Depth-to-Width-Ratio Horizontal NG-GMAW Joint for S500Q Steel.

A novel high depth-to-width ratio of 15:1 narrow-gap gas metal arc welding technique was developed for the welding of S500Q steel in a horizontal butt joint. The bead arrangement of the I groove was optimized to produce a high-quality connection with the upper sidewall of the joint. The microstructure and mechanical properties were observed and evaluated by optical microscopy, scanning electron microscopy, tensile testing, and micro-hardness and impact toughness testing at 1/5, 2/5, 3/5, and 4/5 thickness of the joint. The 3/5 T position exhibited the highest strength, which was attributed to the presence of finer carbide precipitates. The highest micro-hardness appeared at 4/5 T. The highest impact toughness appeared at 3/5 T. The formation of coarse granular bainite was the major reason for the decrease in impact toughness in other regions. A microscopic fracture at 1/5 T and 3/5 T was further analyzed. It was observed that the width of the fibrous zone at 3/5 T was significantly larger than that at 1/5 T. The radial zones at 1/5 T were observed to exhibit cleavage, with secondary cracks on the fracture surface.

Experimental and Numerical Investigation of Shielding Gas Behaviors in Laser Welding of TC4 Alloy.

Gas protection is a crucial part of quality control in laser welding, especially for titanium alloy, which oxidizes easily at high temperatures. Substantial experiments concerning shielding gas characteristics in the welding process have been implemented. However, the common analysis conducted is simplistic and lacks a theoretical basis. This paper presented an investigation of the shielding gas behaviors based on numerical simulation and a titanium alloy laser welding experiment. The numerical model was established and validated by experiment. Subsequently, the temperature field and gas flow fields were calculated. By combining the two fields, the threshold temperature of gas protection was determined, and the influence of shielding gas parameters on the protection effect was examined. The results revealed that the protection of the high-temperature zone was primarily influenced by the nozzle height, nozzle inner diameter, and nozzle angle, while the plasma suppression effect was mainly correlated with the nozzle inner diameter and gas flow rate. These initial findings provide scientific guidance for the better quality production of laser beam welded components made of not only titanium alloy but also other metallic materials.

Investigation of Weld Root Defects in High-Power Full-Penetration Laser Welding of High-Strength Steel.

The currently available high-power laser shows promising opportunities for the welding of thick plates in a single pass. However, weld-root defect frequently occurs when a high-power laser is used to join thick plates in a full-penetration mode, which has a significantly adverse effect on the serviceability of the weld joint. The purpose of this work is to understand the defect formation mechanism and reduce these defects through controlling welding parameters. In this study, the characteristics of weld root defects were investigated using a 10 kW fiber laser using a program of experiment and theoretical analysis. The corresponding defect formation mechanisms were discussed based on the bottom molten pool behaviors observed by the high-speed camera. The results showed that there were four types of weld-root appearances as follows with an increase of linear heat input from 300 J/mm to 1000 J/mm: weld-root humping (30 mm/s), sound weld (25 mm/s), weld sagging (20 mm/s) and excessive weld sagging. The remedies for reducing weld-root defects were also presented to obtain sound weld bead by optimizing welding parameters. Weld-root humping was formed due to the quasi-full-penetration keyhole. Weld sagging resulted from the imbalance of the hydrostatic pressure and surface tension in the condition of a through keyhole. It was also found that the sound weld was formed when a through keyhole and a proper molten pool size were obtained. Thus, the state of the keyhole and molten pool geometry were the major factors that affect weld-root defects.

Effects of Different Types of Interlayers on the Interfacial Reaction Mechanism at the Cu Side of Al/Cu Lap Joints Obtained by Laser Welding/Brazing.

The influence of tin foil and Ni coatings on microstructures, mechanical properties, and the interfacial reaction mechanism was investigated during laser welding/brazing of Al/Cu lap joints. In the presence of a Zn-based filler, tin foil as well as Ni coating strengthened the Al/Cu joints. The tin foil only slightly influenced the joint strength. It considerably improved the spreading/wetting ability of the weld filler; however, it weakened the bonding between the seam and the Al base metal. The Ni coating considerably strengthened the Al/Cu lap joints; the highest tensile strength was 171 MPa, which was higher by 15.5% than that of a joint without any interlayer. Microstructure analysis revealed that composite layers of Ni3Zn14-(τ2 Zn-Ni-Al ternary phase)-(α-Zn solid solution)-Al3Ni formed at the fusion zone (FZ)/Cu interface. Based on the inferences about the microstructures at the interfaces, thermodynamic results were calculated to analyze the interfacial reaction mechanism. The diffusion of Cu was limited by the Ni coating and the mutual attraction between the Al and Ni atoms. The microstructure comprised Zn, Ni, and Al, and they replaced the brittle Cu-Zn intermetallic compounds, successfully strengthening the bonding of the FZ/Cu interface.

The Microstructure and Mechanical Properties of Dual-Spot Laser Welded-Brazed Ti/Al Butt Joints with Different Groove Shapes.

Laser welding-brazing was performed to join Ti and Al together. The dual-spot laser beam mode was selected as the heat source in this study. Ti-6Al-4V and 6061-T6 Al alloys were selected as the experimental materials. Al-12Si welding wire was selected as the filler material. The effect of groove shape on the weld appearance, microstructure, temperature field, and mechanical performance of Ti/Al welded-brazed butt joints was investigated. The interfacial intermetallic compound (IMC) layer at the Ti/Weld brazing interface was inhomogeneous in joints with I-shaped and Y-shaped grooves. In Ti/Al joints with V-shaped grooves, the homogeneity of temperature field and IMC layer was improved, and the maximum thickness difference of IMC layer was only 0.20 µm. Nano-sized granular Ti7Al5Si12, Ti5Si3, and Ti(Al,Si)3 constituted the IMCs. The tensile strength of Ti/Al joints with V-shaped grooves was the highest at 187 MPa. The fracture mode transformed from brittle fractures located in the IMC layer to ductile fractures located in the Al base metal, which could be attributed to the improvement of the IMC layer at the brazing interface.

Experiment and Numerical Simulation for the Compressive Buckling Behavior of Double-Sided Laser-Welded Al-Li Alloy Aircraft Fuselage Panel.

The aim of this work was to study the buckling behavior and failure mode of the double-sided laser-welded Al-Li alloy panel structure under the effect of axial compression via experimental and numerical simulation methods. In the test, multi-frequency fringe projection profilometry was used to monitor the out-of-plane displacement of the laser-welded panel structure during the axial compression load. In addition, the in-plane deformation was precisely monitored via strain gauge and strain rosette. The basic principles of fringe projection profilometry were introduced, and how to use fringe projection profilometry to obtain out-of-plane displacement was also presented. Numerical simulations were performed using the finite element method (FEM) to predict the failure load and buckling modes of the laser-welded panel structure under axial compression, and the obtained results were compared with those of the experiment. It was found that the fringe projection profilometry method for monitoring the buckling deformation of the laser-welded structure was verified to be effective in terms of a measurement accuracy of sub-millimeter level. The structural failure was caused by local buckling of the skin. The observed failure modes such as local buckling of the skin, bending deformation of the stringers, continuous fracture of several welds, and failure of local strength and stiffness were attributed to the deformed laser-welded panel structure under the axial compression. The predicted failure load in the numerical simulation was slightly smaller than that of the experimental test, and the error of the simulation result relative to the test result was -2.7%. The difference between them might be due to the fact that the boundary and loading conditions used in the FEM model could not be completely consistent with those used in the actual experiment.

Inhibition Effectiveness of Laser-Cleaned Nanostructured Aluminum Alloys to Sulfate-reducing Bacteria Based on Superwetting and Ultraslippery Surfaces.

This paper is a continued study on laser cleaning removal of marine microbiofouling from Al alloy surfaces. According to our previous study, it is noted that the antifouling functions of the generated laser-cleaned metallic surfaces must be highlighted. In this work, the inhibition effectiveness of the laser-cleaned Al alloy surfaces was evaluated using a type of vital marine microorganism, sulfate-reducing bacteria (SRB) Desulfovibrio desulfuricans subsp. desulfuricans, in a dynamic bacterial solution. Before the immersion tests, the laser-cleaned surfaces with nanostructures were chemically processed into superhydrophilic, superhydrophobic, and ultraslippery surfaces. SRB attachment behaviors as well as inhibition mechanisms of the three surfaces to the SRB settlement were characterized and revealed. The SRB adhering to the above surfaces presented three different morphologies, i.e., broken, dented, and plump cells. Superhydrophilic surfaces unexpectedly showed a not inferior antibacterial ability. A piercing effect of the nanostructures caused nontoxic mechanical damage to the cell membranes. The antiadhesion property of superhydrophobic solid-air hybrid surfaces was unreliable due to the loss of air bubbles. The morphology of the last surviving SRB cells left on the ultraslippery surfaces was basically plump. The stable repellent function of the surfaces was responsible for the vigorous prevention of the adhesion of the SRB. The research results offer an insight into the antibacterial/antiadhesion properties of the laser-cleaned surfaces and a practical value for the periodic service of marine high-end equipment.

Effect of Laser Beam Oscillation on Laser Welding-Brazing of Ti/Al Dissimilar Metals.

Ti4Al6V and 6061 Al dissimilar metals were butt welded by the laser oscillating welding method. The effects of laser offset, oscillation frequency, and energy distribution on the formation, microstructure, and tensile properties of dissimilar metal joints are discussed in detail. The experimental results show that the Ti6Al4V was micro melted with a laser offset of 1.1 mm, and a large number of intermetallic compounds (IMCs) were formed on the side of the Ti6Al4V. Additionally, there were some porosity defects in the fusion zone (FZ) due to an inappropriate laser oscillation frequency. When the laser offset was increased to 1.2 mm, the IMC distribution was uniform and the thickness was controlled below 2 µm. The porosity defects in the FZ decreased and the tensile strength of the joints increased significantly. The maximum value of tensile strength reached 173 MPa at a laser frequency of 28 Hz.

Microstructure and Mechanical Properties of Laser Welded Al-Si Coated Hot-Press-Forming Steel Joints.

High strength steel has attracted a lot of attention due to its excellent advantage of weight reduction. A thin Al-Si coating covered on the surface of hot-press-forming (HPF) steel offers functions of antioxidation and decarburization under high temperature processing conditions. In this study, the microstructure characteristic, phase, microhardness, and tensile strength of laser welded Al-Si coated HPF steel joints were investigated at different laser powers. Experimental results show that the welding process becomes unstable because of metallic vapor generated by ablation of the coating. Some of the white bright rippled Fe-Al phase was observed to be distributed in the fusion zone randomly. It is found that microhardness, tensile strength, and cupping test qualification rate decreases with the increase of the laser power. For the 1.1 kW laser power, the sound weld performs the best mechanical properties: Microhardness of 466.53 HV and tensile strength of 1349.9 MPa.

Preliminary effectiveness of breast cancer screening among 1.22 million Chinese females and different cancer patterns between urban and rural women.

To determine the preliminary effectiveness of breast cancer screening among Chinese females, 1226714 women aged 35-69 years first received clinical breast examinations. Urban women with suspected cancer received mammography followed by breast ultrasound (BUS), while rural suspected women underwent BUS followed by mammography. After one-year follow-up, 223 and 431 breast cancers were detected among urban and rural women (respectively), with overall detection rates of 0.56/1000 and 0.52/1000. Higher detection rates were significantly associated with older age at screening for both urban and rural women; additionally, urban women were at significantly higher risk if they had no job, no insurance, or were obese; additional risk factors specific to rural women included Han nationality, higher income, being unmarried, and having a family history of cancer (all P values < 0.05). Among screening-detected breast cancers in urban vs. rural women, 46.2% and 38.8% (respectively) were early stage, 62.5% and 66.3% were ≤2 centimeters, 38.0% and 47.3% included lymph-node involvement, and 14.0% and 6.0% were identified as carcinoma in situ. All abovementioned cancer characteristics were significantly better than clinic-detected cancers (all P values < 0.001). In conclusion, several important differences were found between urban and rural women in screening effectiveness and patterns of cancer distribution.

[Eradication of schistosomiasis: a new target and a new task for the National Schistosomiasis Control Porgramme in the People's Republic of China].

The achievements for the national schistosomiasis control programme in the People's Republic of China over the last 6 decades were reviewed, with an emphasis on the status and challenges to accomplish the tasks of "Workplan for the Mid- and Long-term of National Schistosomiasis Control Programme from 2004 to 2015". Four features of current national schistosomiasis control programme were identified in the new stage. First, the high prevalence areas have been shrunk, but few regions are still at the risks of schitosomiasis rebounding. Second, large areas with low prevalence of schistosomiasis will remain for a long time, so that the disease surveillance will be a long-term task. Third, more notable places will be in the high risk areas where more activities of human and livestock occurred, so that it is essential to implement the integrated control measures in those high risk areas. Fourth, the technologies using in the schistosomiasis eradication programme are delayed as expected, and more needs to accelerate the R&D programmes. It was recommended that sustained implementation of integrated control strategy with more emphasis on control of infectious sources has to be strengthened through enhanced regulation performance in addition to the aforementioned notifications, in order to eradicate schistosomiasis in a response to the newly formulated target of "making the 'God of Plague' to be sweep away from the history, and retuning the clear land/water and happy/healthy life to the people".

[The Endemic Situation and Challenges of Major Parasitic Diseases in China].

During the twelfth "Five-year Plan" period, the Chinese government further strengthened the implementation of several medium and long-term plans on disease control, which resulted in the acceleration of the control of schistosomiasis, malaria and echinococcosis. To further elucidate the endemic status and control experience during the stage, this article described current situation on the major parasitic diseases and put forward the challenges and consequent countermeasures for planning the control programs in the next five years and laying a foundation for the next Five-year Planning.

[Endemic status of schistosomiasis in People's Republic of China in 2014].

This report presented the endemic status of schistosomiasis in the People's Republic of China at national level in 2014, and analyzed the data captured from the national schistosomiasis prevention and control system and 81 national schistosomiasis surveillance sites. Among the 12 provinces (municipality and autonomous region) endemic for schistosomiasis japonica in China, 5 provinces (municipality and autonomous region) of Shanghai, Zhejiang, Fujian, Guangdong and Guangxi had achieved transmission interruption, 4 provinces of Sichuan, Yunnan, Jiangsu and Hubei had achieved transmission control, and Anhui, Jiangxi and Hunan provinces were still at infection control until 2014. There were 453 counties (city, district) endemic for schistosomiasis, with 251 million residents, and 30,048 villages endemic for schistosomiasis, with 68 million 507 thousand and 3 hundred residents. Among the 453 endemic counties (city, district), 69.09% (313/453) and 29.80% (135/ 453) endemic counties (city, district) reached the transmission interruption and transmission control respectively while the number of counties (city, district) at the stage of infection control reduced from 34 in 2013 to 5 in 2014 (accounted for 1.10% of the total number of endemic counties, 5/53). Till 2014, 115,614 people were estimated to have schistosomiasis and only 2 acute schistosomiasis cases were reported. In addition, there were 30,880 advanced schistosomiasis cases documented in 2014. In 2014, a total of 9,461,348 individuals received schistosomiasis examinations and 8,270 persons were found stool positives with the reduction rate of 50.96% as compared to that (16,865 cases) in 2013. The Oncomelania hupensis snail survey was performed in 20 123 endemic villages in 2014, and the snails were detected in 5,653 villages, which accounted for 28.09% of total villages, with 13 newly detected villages with snails. The snail survey covered an area of 576,506.37 hm² and snails were found in an area of 364 324.42 hm², including an area of 531.13 hm² detected snails for the first time. No schistosome infected snails were found in 2014. A total of 919,579 head of cattle were raised in the schistosomiasis endemic areas of China. In 2014, 494,620 head of cattle received examinations and only 666 were determined as stool positives. Based on the data from the 81 national schistosomiasis surveillance sites of China, the mean Schistosomajaponicum infection rate was 0.11% and 0.05% in humans and cattle respectively, and no infected snails were detected in 2014. There were 280,855 schistosomiasis cases receiving treatments, with 2,565,555 cases undergoing expanded chemotherapy; there were 798 head of cattle with schistosomiasis receiving treatments, with 408,690 head of cattle undergoing expanded chemotherapy; there was a total 138,923.90 hm² area with snail control by using molluscicides , with actual mollusciciding of 74,538.17 hm²; and there was an environmental modification of 5,331.42 hm². These data demonstrate a decline in the endemic city of schistosomiasis in China in 2014. However, the risk of schistosomiasis transmission remains high in some regions. Further control and effective surveillance should be strengthened to consolidate the achievements and reduce the endemic situation of schistosomiasis in China.

[Progress and challenges of the National Schistosomiasis Control Program during the period of the 12th Five-Year Plan].

The achievements of the national schistosomiasis control program during the period of the 12th Five-Year Plan were reviewed, in particular, the reduction of the prevalence and progress in control activities were evalucated among different regions of China. Moreover, current difficulties of schistosomiasis control and gaps to achieve the transmission interruption of the disease in China were analyzed, which provide more evidences to formulate the future efforts and work-plan to eliminate the disease in the country.

[Endemic status of schistosomiasis in People's Republic of China in 2013].

This report presented the endemic status of schistosomiasis in the People's Republic of China at national level in 2013. By the end of 2013, there are 184 943 schistosomiasis japonica cases. Meanwhile, nine acute cases were reported, and 4 cases reduced compared with that of 2012. A total of 29 796 advanced cases were reported; while 911 cases were determined as advanced cases and 1 700 cases were dead in 2013. Nationally, there were around 365 467.99 hm2 Oncomelania snail infested areas in total and 9.25 hm2 of them habituated infected snails in 2013. There were 287.28 hm2 of snail infested areas found in non-endemic areas historically. Moreover, 962 065 cattle were estimated to be raised in endemic regions and 633 cattle were determined as positive by stool examinations. The data showed that the endemicity of schistosomiasis in China decreased further. However, challenges exist to reach the aims of the medium and long-term national program. Further control and effective surveillance need to be strengthened as the endemicity of schistosomiasis is unstable in the areas after schistosomiasis transmission under control or interruption.

[Control situation and primary task of key parasitic diseases in China].

In the "11th Five-year Plan" period, China unveiled a mid-term planning on the control of the key parasitic diseases, including schistosomiasis, malaria, echinococcosis (hydatid disease), as well as some other parasitic diseases. It clarifies the goals on the control of the major parasitic diseases in the national control program during the "12th Five-year' Plan" period (2011-2015) , formulates current main tasks based on analyzing the progress of the national control program on key parasitic diseases, in order to meet the challenges appearing in the future implementation.

[The current situation of blood pressure control and the influencing factors on hypertensive patients in residential communities of China].

OBJECTIVE: To understand the situation of blood pressure control and the major factors influencing the programs among those hypertensive patients living in the communities from different parts of China. METHODS: A protocol of community-based standardized blood pressure management was developed based on the current Chinese guideline for prevention, treatment of hypertension. Grass-roots caretakers from community health service centers across China were trained under the requirement of this protocol to manage the hypertensive patients. In this study, the hypertensive patients who had been registered in the project centers from Beijing, Hebei, Gansu, Jiangsu, Zhejiang, Guangdong provinces, were selected as the study subjects, and the baseline data for these patients was analyzed. RESULTS: By the end of 2010, a total of 242 182 patients were registered. The mean age was 61.0 ± 10.5, with 48.5% of them being males. The overall control rate of blood pressure was 27.4%. The control rate was significant lower among patients who were in lower age group, being male, with higher BMI, smoking, drinking or with more salt consumption. However, the control rate was significant higher among those patients who had family history of hypertension, always undertook physical exercise or receiving medical treatment. CONCLUSION: The blood pressure control rate for community hypertensive patients in China was still in a relatively low level. Standardization management measures should be strengthened so as to improve the rate of control on high blood pressure.

[Schistosomiasis status in People's Republic of China in 2010].

This annual report overviewed the national endemic status of schistosomiasis japonica in People's Republic of China in 2010. By the end of 2010, a total of 325 824 cases of schistosomiasis japonica were estimated with a decrease rate of 10.92% compared to those in 2009. A total of 43 acute cases were reported, decreased by 44.16% compared to those in 2009. A total of 25 115 advanced cases were treated in 2010, increased by 3.43% compared to that in 2009. About 373 596.18 hm2 of areas infested with Oncomelania snail were found in 2010, and about 1 081.80 hm2 newly detected areas were reported. A total of 1 476 606 cattle were raised in schistosomiasis transmission regions in 2010. The infection rate of cattle infected with Schistosoma japonicum was 1.04% in 2010, with a little increase comparing to that in 2009 (1.03%).