Abstract: Effect of hydrogen trapping and poisons on diffusion behavior of hydrogen in commercial cold-rolled low carbon steel was investigated by means of electrochemical hydrogen permeation techniques. The experimental results reveal that diffusion rate and diffusion flux of hydrogen in the materials gradually increase with increasing the number of hydrogen charging and outgassing, and lag time significantly shortens with them, therefore, hydrogen trapping impede diffusion behavior of hydrogen in the materials. Different poisons in the hydrogen charging solution have also resulted in a certain influence on the assessment of hydrogen diffusion behavior.
Abstract: We discuss two methods of preparation and modification on nanoMMT, one is called “one-step method”, and another is called “two-steps method”. And then we use the IR, TEM, XRD, granulometer and sedimentation to test the effect of modification. The result shows that two methods can also modify nanoMMT, but the nanoMMT made by “one-step method” in lubricate oil is more stable and dispersed than another’s. Average grain diameter of nanoMMT made by “one-step method” in lubricate oil is 46nm, while another’s is 69.75nm. Also, it’s layer distance has expanded from 1.52nm to 2.10nm.
Abstract: Applying 3D digital image correlation (3D-DIC) method to observe and investigate on crack forming process of C45 cylinder concrete under axial compression. The three-dimensional displacement and strain of the exterior surface of C45 concrete during the failure process are obtained. Furthermore, the location and shape of the crack are predicted with the generation, variation and aggregation of the maximum strain equipotential line on the concrete surface. The results show that the applying of 3D-DIC method can accurately obtain the concrete strain distribution data, predict the crack development trend and provide an important basis for further study on the mechanism of damage and fracture characteristics of concrete structure.
Abstract: In order to improve the corrosion resistance of shock absorber for ships, the alumina ceramic coatings are carried out on the surface of aluminum alloy shock absorber by micro arc oxidation (MAO) technology. The microstructure and anti-corrosion performance of the MAO coatings were investigated experimentally. This paper mainly focuses on the experimental work to determine the effect of current density on the structural characteristics and corrosion resistance of MAO coatings. The results show that the current density has a significant influence on the preparation of MAO coating during the process. The surface of the coating becomes more compact and smooth with the cathode voltage of 7 A.dm-2. Furthermore, the anti-corrosion performance of the MAO coatings can effectively be improved at the current density of 7 A.dm-2.
Abstract: In order to improve the high temperature oxidation resistance of exhaust pipes, the nanocomposite coatings are carried out on the surface of exhaust pipe by electrodeposition technology, and the microstructure and oxidation behavior of the nanocomposite coatings are investigated experimentally. This paper mainly focuses on the experimental work to determine the structural characteristics and oxidation resistance of nanocomposite coatings in presence of Al2O3 and cerium oxide CeO2. The results show that the amount of the Al2O3-CeO2 has significant influence on the structural properties of nanocomposite coatings. The surface of coating becomes more compact and smooth with the increase of the amount of the Al2O3 and CeO2. Furthermore, the anti-oxidation performance of the nanocomposite coatings formed with Al2O3 and CeO2 were both better than those of the composite coatings formed without Al2O3 and CeO2.
Abstract: It is one of the difficult problems in the manufacture of the integrated aircraft part of Machining distortion caused by residual stress. According to the characteristics of aluminum alloy pre stretched thick plate, the modified removal method for measuring residual stress in thick pre-stretched aluminum plates is proposed and the stress-strain relation matrix is deduced by elasticity theory. Moreover, the residual stresses in the specimen of 7075T7351 plate is measured by the proposed method, and the results are finally analyzed and compared with the data obtained by other methods. The results indicate that the proposed method is effective in measuring the residual stress in thick pre-stretched aluminum alloy plates. The measurement results can be used for the quantitative analysis of aerospace parts machining distortion caused by residual stress, and it has higher value in engineering application.
Abstract: Precision rubber mold is an extremely important basic process equipment in industrial production, however, there are some classic problems, such as viscose, coke accumulation and difficult demoulding, can not be effectively resolved. In order to solve this problem, in this paper, a new process of preparing high performance DLC coated precision rubber mold is proposed by using the excellent anti-sticking properties, self-cleaning properties and hydrophobic properties of DLC coating. In the experiment, steel ( S35C ) substrate with the same material as tire mold is used. Hydrophobic of DLC coating surface mainly depends on the surface element composition and the roughness. All the substrates are exactly processed, so as to ensure that the roughness has minimal impact on hydrophobic. Plasma enhanced chemical vapor deposition (PECVD) technology is employed to prepare fluorine doped diamond-like carbon (F-DLC) coating and hydrogenated diamond-like carbon (a-C:H) coating. Arc ion plating (AIP) technology is applied to produce Non-hydrogenated diamond-like carbon (a-C) coating. The coating is deposited on the surface of steel ( S35C ). Then, the roughness, the element composition and the hydrophobicity of the prepared coating are tested. Experimental results demonstrate that the water contact angle of a-C coating only 73.8 degrees, water contact angle of a-C:H coating up to 80.16 degrees, however, water contact angle of F-DLC coating could reach to 89.01 degrees, meanwhile, the surface energy can be reduced to 22.62 mN/m. To some extent, the hydrophobicity of the coating enhances with the increase of H content, and the content of weak polarization group CF2 becomes stable with the incorporation of F element. As a consequence, the surface of coating becomes smoother and the wettability of coating and water becomes poorer, therefore the performance of hydrophobic of the coating is further enhanced.
Abstract: Hydrophobicity improvement of DLC can be achieved by adding fluorine element usually. However, higher F content may affect the other performance of DLC seriously, such as strength and abrasive resistance. Plasma enhanced chemical vapor deposition technology were employed to prepare F-DLC on the surface of steel (S35C) substrate in condition of 20mass% of F. Experimental results demonstrated that roughness significant increase in the coating substrate has contributed to improve hydrophobicity. In the range of 0~200nm for the roughness, the contact angle is influenced by the surface energy and the surface roughness; Ra>200nm, the influence of roughness on the water contact angle is gradually becoming the leading. And Ra=1300nm, water contact angle is 104°.
Abstract: Coal-winning machine is to break coal with rotating mechanism. Owing to the harsh working environment and large stress, the top-disc plate, helical blade and tooth holder in cylinder often lose their wear resistance, hence causing overhauling of the machine and influencing the production of coal. With the modernization of the production technology and mining equipment of coal, the mining intensity of coal constantly increases, which calls for higher wear resistance of the top-disc plate, helical blade and tooth holder in cylinder. Currently, many studies have been performed on the wear resistance of the tooth holder in cylinder, but rare on the wear-resistant technology and wear resistance of the top-disc plate and helical blade in cylinder. In this paper, 16Mn steel which is used in the top-disc plate and helical blade in the cylinder of coal-winning machine was welded based on surfacing technology using EDTCrMnSi special wire to obtain composite wear-resistant steel plates. Then wear tester was employed to compare the wear of 16Mn steel and composite wear-resistant steel plate. Meanwhile, metallographic microscope and x-ray fluorescence spectrometer (XRF) were used to observe the microstructure of the materials and analyze the types and contents of elements in the surfacing layers of the composite wear-resistant steel plate. Furthermore, the influence of surfacing technology on the wear resistance of the material was analyzed. The results showed that there existed high contents of Cr, Si and Mn in the surfacing layers of the top-disc plate and helical blade in cylinder of the coal-winning machine after welded based on surfacing technology. Moreover, the wear resistance and service life of matrix were largely improved.