板厚对薄壁锥形件拉深成形的影响

在食品包装行业,易撕盖食品罐的应用十分广泛。锥形件作为易撕盖食品罐可以在满足强度要求的前提下方便食品的盛装和夹取。由于锥形件拉深过程中侧壁悬空,起皱成为其拉深成形的一个难题,在薄壁易撕盖食品罐拉深过程中尤为突出。针对铝合金锥形易撕盖食品罐的拉深成形,基于有限元模拟分析技术,获取了不同厚度下的经向应力、纬向应力分布曲线,结合锥形件拉深效果图研究了锥形件拉深过程中的成形特点。

Zonal disintegration phenomenon in enclosing rock mass surrounding deep tunnels—mechanism and discussion of characteristic parameters

The mechanism of the zonal disintegration phenomenon(ZDP) was realized based on the analysis of the stressedstrained state of the rock mass in the vicinity of the maximum stress zone, which resides in the creep instability failure of rock mass due to the development of a plastic zone and transfer of the maximum stress zone within the rock mass.Some characteristic parameters of the ZDP are discussed theoretically.In first instance, the analytical critical depth condition for the occurrence of ZDP was obtained, which depends on the characteristics and stress concentration coefficient of the rock mass.Secondly, based on creep theory, the expression of the outer radius of the undisturbed zones in the deep rock mass was obtained with the use of an improved Burgers rheological model, which indicated that the radius depends on the characteristics of the rock mass and the depth of excavation and increases quasi-linearly with the rise of creep compliance of the rock mass.Finally, the formula for the distance of the most remote fissured zone away from the working periphery was derived, which increases logarithmically with the increase in the ratio of the in-situ stress and ultimate strength of rock mass.The distances between fissured zones are discussed in qualitative terms.

Evaluation of the zonal wind stress response to SST in the CMIP5 AMIP simulations

Zonal wind stress plays an important role in the evolution of El Ni（n）o-Southern Oscillation （ENSO） events;however,a comprehensive comparison and analysis in terms of model performance and related bias in the interannual variability of zonal wind stress across the tropical Pacific has yet to be performed.In this study,the authors evaluate how well the individual atmospheric models participating in phase 5 of the Coupled Model Intercomparison Project simulate zonal wind stress.It is found that the wind stress anomalies simulated by the multi-model ensemble are weaker than those in the observation in both El Ni（n）o and La Ni（n）a events,with a larger bias in the former.Further analysis indicates that the bias associated with El Ni（n）o events may be mainly attributable to the weaker negative precipitation anomalies in the AMIP simulations,compared with observations,over the eastern Indian Ocean.Through the Gill-like responses in atmospheric circulation,the rainfall bias over the eastern Indian Ocean results in an easterly wind stress anomaly in the western and central equatorial Pacific,which to some extent offsets the westerly wind stress anomalies associated with El Ni（n）o events.Consequently,the responses of zonal wind stress anomalies to warm SST anomalies are much underestimated in AMIP simulations during El Niffo events.

Structure of the Indian Ocean Meridional Overturning Circulation and its relationship with the zonal wind stress

We studied the structure of the Indian Ocean(IO)Meridional Overturning Circulation(MOC)by applying a nonlinear inertia theory and analyzed the coupled relationship between zonal wind stress and MOC anomalies.Our results show that the inertia theory can represent the main characteristics of the IO MOC:the subtropical cell(STC)and cross-equator cell(CEC).The stream function in equatorial and northern IO changes a sign from winter to summer.The anomalies of the zonal wind stress and stream function can be decomposed into summer monsoon mode,winter monsoon mode,and abnormal mode by using the singular vector decomposition(SVD)analysis.The first two modes correlate with the transport through 20°S and equator simultaneously whereas the relationship obscures between the third mode and transports across 20°S and equator,showing the complex air-sea interaction process.The transport experiences multi-time scale variability according to the continuous power spectrum analysis,with major periods in inter-annual and decadal scale.