Advanced Materials Research Vols. 299-300

Abstract: In this paper, inverse pseudo excitation method for vehicle dynamic load identification is used. When the vehicle is in stationary random vibration, the vehicle dynamic load spectrum recognition problem is solved by using the deterministic method. The auto-PSD and cross-PSD of vehicle vibration response is known. Base on the reversing the power spectrum of road excitation, Vehicle dynamic load PSD is obtained. The results show that, Inverse pseudo excitation method for solving the vehicle dynamic load spectrum has good solution accuracy, put forward new ideas and methods for vehicle engineering practice, and has broad application prospects.

Abstract: The stretch-bend springback of dual phase steel DP590 was studied experimentally and numerically in this paper. The aim of this work is to investigate the effects of elastic modulus degradation on springback prediction. Two anisotropic yield function yld89 and yld2000 were utilized along with isotropic hardening law. The appropriate material parameters characterizing the elastic modulus decrease were identified by response surface modeling. The current work showed that the accuracy of springback simulation improved when considering elastic modulus decreased with plastic strain and yld2000 can predict springback more accurately considering blank orientation in stretch bending.

Abstract: The influence of Sn content on the microstructure and dry sliding wear behaviour of hypereutectic Al-20Si alloy was investigated. The results show that the b-Sn in the alloys precipitates mainly in the form of strips and blocks on the grain boundaries of α-Al phase or the interface of silicon and α-Al phases. The addition of Sn can improve the wear resistance of the hypereutectic Al-20Si alloy.

Abstract: In the unmodified and EP-modified melt of Q235 steel, the solidification behavior including the nucleation and growth of crystals has been observed in situ by use of a confocal scanning laser microscope combined with an infrared image furnace, and meanwhile, described the characteristic of phase transformation. The result shows that the every stage of phase transformation is advanced; the phase transformation time is shortened, and temperature is reduced during heating proceeds. On the other hand, it can be observed that the nucleation density of solid phase increases and has an even distribution among the liquid phase.

Abstract: The type, shape and distribution of inclusions in ductile cast iron were studied using a scanning electron microscopy (SEM) and the energy spectrum analysis, combining the thermodynamic calculation of inclusions formation. The results show that the oxides are most likely formed from the thermodynamics in ductile cast iron when the temperature is 1373~1873 K , followed by the sulfides, the carbides again. There exist the uniphase inclusions MgO, SiO₂ and MgS, the heterogeneous inclusions of containing rare-earth MnO-MgO-SiO₂-La₂O₃ and MgS-LaS-SiO₂-Al₂O₃-MgO , and the heterogeneous inclusions of non-rare earth SiO₂-MnO-MgO-Al₂O₃ in ductile cast iron. The shapes of the inclusions are mainly polygon, and the size variation is from 3 to 10 um. The inclusions are mainly distributed on the graphite ball surfaces, the ferrite grain boundaries and in the pearlites.

Abstract: The distinct images of molten steel droplets were obtained utilizing a home-made experimental equipment, and the method which measures the contact angle between the molten steel droplet and the refractory material using a computer image processing technology and Visual C++ language was represented, meanwhile the measurement system of the contact angle was developed. The results show that the maximum deviation of the measurement system is 0.13° comparing with the actual measurement results, the minimum deviation is 0.03°, and the mean deviation is 0.06°. Under this experiment conditions, the contact angle increases 1.2° when the quality of sample increases from 0.2g to 0.8g at 1550°C, and the contact angle increases 2.3° when the temperature increases from 1550°C to 1600°C for the sample of 0.2g.

Abstract: Under the condition that the solid-liquid interface bends periodically in continuous casting, the expression of solid-phase growth rate adapting to continuous casting was set up, and then the growth rates were calculated. On this basis, the morphologic of crystal growth and the variation of primary dendrite spacing during continuous casting slabs were studied. The results show that the growth rate is the fastest when solid-phase moves to wave crest within a deformation periodicity, whereas the growth rate is the slowest when the crystal moves to wave hollow. The bigger the bulge size is, the greater the variation amplitude of the growth rate will become. The variation of the growth rate results in the S/L interface to develop towards a planar surface. Because the value is much smaller than the critical value of the transformation from cells to dendrites, and the crystals only grow in the fashion of dendrites. The primary dendrite spacing at wave crest is bigger than the primary dendrite spacing at wave hollow in early stage of columnar crystal growth, and the dendrite spacing at wave crest is basically equal with the dendrite spacing at wave hollow in the late stage of solidification, and they quickly simultaneous increase. Good correlation is obtained between the experimental results and the calculation results of the dendrite arm spacing.

Abstract: The carbon steel samples of great quality can not be melted using a high-temperature confocal scanning laser microscopy(HTCSLM). On account of only arc surface of the tiny liquid-drop top is observed, it is difficult to obtain distinct images. The shape variation of the tiny liquid-drop is studied experimentally in this article. The results show that the shape of the liquid-drop will be changed at 1600°C, when the carbon steel sample of 0.5g is laid on the Al₂O₃ sloping of 15 degrees. Though the radius of curvature of the liquid-drop top surface is obviously enlarged, the impact of improving the surface shape of liquid-drop through the gravity flow of tiny liquid-drop is finite. For the carbon steel sample of less than 0.8g, the hanging drop is automatically formed in the melting process under the condition that the gap between the solid sample and Al₂O₃ single crystal plate is 0.3mm, and the shape retains invariant when it is hold for 20 min at 1600°C. The contact surface between the sample and Al₂O₃ single crystal plate is 24mm².

Abstract: The fracture toughness of different zones of X100 SAWL pipe was studied by three-point bend test method under different temperature. At the same temperature, the crack propagation resistance and tear modulus of X100 SAWL pipe distributed as: base metal>HAZ>weld bead, and the distribution of the CTOD value of X100 SAWL pipe is :base metal >weld bead >HAZ. Further investigation was conducted to analyze the decrease of fracture toughness (especially low temperature fracture toughness) and the occurrence of local unstable phenomenon in HAZ specimens.

Abstract: The authors investigate the effect of electric pulse field (EPF) on the grain size of Pb-Sn alloy and conclude the optimization parameter of EPF through the specialized experiment. Applying the electric dipole theory, the electro-migration theory and combining with the electrostatic force analysis, the author explain that the EPF can modify the liquid structure, can make the smaller cluster reorganized and growing up and at the same time can make the bigger cluster fission, then induce the cluster scale to the same and therefore improve the solidification structure from the theory point of view.