Friction stir welding （FSW） was performed on 2024-T351 aluminum alloy plates. Metallographic analysis, Vickers microhardness and XRD tests were conducted to determine the properties of the welded zone. FE simulatio...Friction stir welding （FSW） was performed on 2024-T351 aluminum alloy plates. Metallographic analysis, Vickers microhardness and XRD tests were conducted to determine the properties of the welded zone. FE simulation of the FSW process was implemented for the different welding conditions to extract the residual stress and stress intensity factor （SIF）. Fracture and fatigue behaviors of the welds which have the initial crack in the nugget zone and the crack orientation along the welding direction, were studied based on standard test methods. Fracture behavior of the welds was also evaluated by shearography method. The results showed that the tool rotational and traverse speeds affect the fracture toughness and fatigue crack growth rate. FSW provides 18%-49% reductions in maximum fracture load and fracture toughness. A slight diminution in fracture toughness of the joints was observed for lower traverse speed of the tool, and at higher traverse or rotational speeds, increasing the probability of defects may contribute to low fracture toughness. Fatigue crack propagation rate of all welds was slower than that of the base metal for low values of stress intensity factor range ΔK （ΔK〈13 MPa·m^1/2）, but is much faster for high values of ΔK.展开更多
The technique of real-time digital speckle pattern interferometry is p roposed to study diffusion of surfactants in hydrogel. The diffusion coefficient is simply and directly determined from the interferograms. An e...The technique of real-time digital speckle pattern interferometry is p roposed to study diffusion of surfactants in hydrogel. The diffusion coefficient is simply and directly determined from the interferograms. An example of diffus ion coefficient measurement of surfactant in agarose gel demonstrates the useful ness of the method. The results obtained are compared with the theoretical simul ating values.展开更多
A temporal approach to fast shape measurement is presented.In principle,the rotational object method is used in combination with the sequence pulse counting method (SPCM) to determine the height of the object through ...A temporal approach to fast shape measurement is presented.In principle,the rotational object method is used in combination with the sequence pulse counting method (SPCM) to determine the height of the object through calculating the related phase.Two specimens are tested to demonstrate the validity of the approach.One is an object covered by a Chinese character (tea) with a height variety of 0.3 mm,and the other is an object surface with a relatively large fluctuation of 3.5 mm.The experimental results are compared with mechanical measurements.An axis shifting method is also proposed to determine shapes with relatively large fluctuations.Effects of such parameters on the height measurement as incident angle of the dual light beams,tilting angle of the object,and azimuth angle of the measured point are discussed as well.展开更多
文摘Friction stir welding （FSW） was performed on 2024-T351 aluminum alloy plates. Metallographic analysis, Vickers microhardness and XRD tests were conducted to determine the properties of the welded zone. FE simulation of the FSW process was implemented for the different welding conditions to extract the residual stress and stress intensity factor （SIF）. Fracture and fatigue behaviors of the welds which have the initial crack in the nugget zone and the crack orientation along the welding direction, were studied based on standard test methods. Fracture behavior of the welds was also evaluated by shearography method. The results showed that the tool rotational and traverse speeds affect the fracture toughness and fatigue crack growth rate. FSW provides 18%-49% reductions in maximum fracture load and fracture toughness. A slight diminution in fracture toughness of the joints was observed for lower traverse speed of the tool, and at higher traverse or rotational speeds, increasing the probability of defects may contribute to low fracture toughness. Fatigue crack propagation rate of all welds was slower than that of the base metal for low values of stress intensity factor range ΔK （ΔK〈13 MPa·m^1/2）, but is much faster for high values of ΔK.
文摘The technique of real-time digital speckle pattern interferometry is p roposed to study diffusion of surfactants in hydrogel. The diffusion coefficient is simply and directly determined from the interferograms. An example of diffus ion coefficient measurement of surfactant in agarose gel demonstrates the useful ness of the method. The results obtained are compared with the theoretical simul ating values.
基金supported by the National Natural Science Foundation of China(Grants Nos. 10972113,10732080)the National Basic Research Program of China(Grant Nos. 2007CB936803,2010CB631005)SRFDP(Grant No. 20070003053)
文摘A temporal approach to fast shape measurement is presented.In principle,the rotational object method is used in combination with the sequence pulse counting method (SPCM) to determine the height of the object through calculating the related phase.Two specimens are tested to demonstrate the validity of the approach.One is an object covered by a Chinese character (tea) with a height variety of 0.3 mm,and the other is an object surface with a relatively large fluctuation of 3.5 mm.The experimental results are compared with mechanical measurements.An axis shifting method is also proposed to determine shapes with relatively large fluctuations.Effects of such parameters on the height measurement as incident angle of the dual light beams,tilting angle of the object,and azimuth angle of the measured point are discussed as well.
