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| 1 | Effects of porosity and pore size on the compressive properties of closed-cell Mg alloy foam显示文摘In our current work,AZ31 magnesium alloy foams with closed-cell were successfully fabricated by melt foaming method using Ca and CaCO3 as thickening and blowing agent,respectively.The influences of porosity and pore size on the quasi-static compressive properties of the foams were systematically investigated.The results showed that the yield strength,energy absorption capacity and ideality energy absorption efficiency were decreased with the increase in porosity.However,specimens with porosities of 60%,65%and 70%possessed similar total energy absorption capacity and ideality energy absorption efficiency.Meanwhile,experimental results showed that mean plateau strength of the foams was increased first and then decreased with increase in mean pore size.In addition,energy absorption capacities were almost the same in the initial stage,while the differences were obvious in the middle stage.From the engineering point of view,the specimens with mean pore size of 1.5 mm possess good combination of mean plateau strength and energy absorption characteristics under the present conditions. | X.C.Xia X.W.Chen Z.Zhang X.Chen W.M.Zhao B.Liao B.Hur | 2013 | Journal of Magnesium and Alloys2013，1，4： | 8 |
| 2 | Effect of compressibility on the hypervelocity penetration显示文摘We further consider the effect of rod strength by employing the compressible penetration model to study the effect of compressibility on hypervelocity penetration.Meanwhile, we define different instances of penetration efficiency in various modified models and compare these penetration efficiencies to identify the effects of different factors in the compressible model. To systematically discuss the effect of compressibility in different metallic rod-target combinations, we construct three cases, i.e., the penetrations by the more compressible rod into the less compressible target, rod into the analogously compressible target, and the less compressible rod into the more compressible target. The effects of volumetric strain, internal energy, and strength on the penetration efficiency are analyzed simultaneously. It indicates that the compressibility of the rod and target increases the pressure at the rod/target interface. The more compressible rod/target has larger volumetric strain and higher internal energy. Both the larger volumetric strain and higher strength enhance the penetration or anti-penetration ability. On the other hand, the higher internal energy weakens the penetration or anti-penetration ability. The two trends conflict, but the volumetric strain dominates in the variation of the penetration efficiency, which would not approach the hydrodynamic limit if the rod and target are not analogously compressible. However, if the compressibility of the rod and target is analogous, it has little effect on the penetration efficiency. | W.J.Song X.W.Chen P.Chen | 2018 | Acta Mechanica Sinica2018，34，1： | 6 |
| 3 | Stability analyses of the mass abrasive projectile high-speed penetrating into a concrete target Part III: Terminal ballistic trajectory analyses显示文摘During the high-speed penetration of projectiles into concrete targets(the impact velocity ranges from 1.0 to1.5 km/s), important factors such as the incident oblique and attacking angles, as well as the asymmetric abrasions of the projectile nose induced by the target-projectile interactions,may lead to obvious deviation of the terminal ballistic trajectory and reduction of the penetration efficien y. Based on the engineering model for the mass loss and nose-blunting of ogive-nosed projectiles established, by using the Differential Area Force Law(DAFL) method and semi-empirical resistance function, a finit differential approach was programmed(PENTRA2D) for predicting the terminal ballistic trajectoryofmassabrasivehigh-speedprojectilespenetrating into concrete targets. It accounts for the free-surface effects on the drag force acting on the projectile, which are attributed to the oblique and attacking angles, as well as the asymmetric noseabrasionoftheprojectile.Itsvalidationontheprediction of curvilinear trajectories of non-normal high-speed penetrators into concrete targets is verifie by comparison with available test data. Relevant parametric influentia analyses show that the most influentia factor for the stability of terminal ballistic trajectories is the attacking angle, followed by the oblique angle, the discrepancy of asymmetric nose abrasion, and the location of mass center of projectile. The terminal ballistic trajectory deviations are aggravated as the above four parameters increase. | H.Wu X.W.Chen Q.Fang X.Z.Kong L.L.He | 2015 | Acta Mechanica Sinica2015，31，4： | 4 |
| 4 | Approximate solutions of the Alekseevskii–Tate model of long-rod penetration显示文摘The Alekseevskii–Tate model is the most successful semi-hydrodynamic model applied to long-rod penetration into semi-infinite targets. However, due to the nonlinear nature of the equations, the rod(tail) velocity, penetration velocity, rod length, and penetration depth were obtained implicitly as a function of time and solved numerically By employing a linear approximation to the logarithmic relative rod length, we obtain two sets of explicit approximate algebraic solutions based on the implicit theoretica solution deduced from primitive equations. It is very convenient in the theoretical prediction of the Alekseevskii–Tate model to apply these simple algebraic solutions. In particular, approximate solution 1 shows good agreement with the theoretical(exact) solution, and the first-order perturbation solution obtained by Walters et al.(Int. J. Impac Eng. 33:837–846, 2006) can be deemed as a special form of approximate solution 1 in high-speed penetration. Meanwhile, with constant tail velocity and penetration velocity approximate solution 2 has very simple expressions, which is applicable for the qualitative analysis of long-rod penetration. Differences among these two approximate solutions and the theoretical(exact) solution and their respective scopes of application have been discussed, and the inferences with clear physical basis have been drawn. In addition, these two solutions and the first-order perturbation solution are applied to two cases with different initial impact velocity and different penetrator/target combinations to compare with the theoretical(exact) solution. Approximate solution 1 is much closer to the theoretical solution of the Alekseevskii–Tate model than the first-order perturbation solution in both cases, whilst approximate solution 2 brings us a more intuitive understanding of quasi-steady-state penetration. | W.J.Jiao X.W.Chen | 2018 | Acta Mechanica Sinica2018，34，2： | 4 |
| 5 | Spherical cavity-expansion model for penetration of reinforced-concrete targets显示文摘The feature of reinforcing bars is introduced into dynamic cavity-expansion theory. Based on the elastic-plastic response penetration model of plain (i.e., unreinforced) concrete (Forrestal and Tzou, 1997), a dynamic spherical cavity-expansion penetration model for reinforced-concrete targets is developed with consideration of the circumferential restriction effect derived from reinforcing bars in the crushed region. The theoretical solution and simplified calculation formula for the cavity radial stress in incompressible and compressible reinforced concrete are obtained by introducing a reinforcement ratio as the volume fraction of rebars in the concrete target. A damping function is presented to describe the restriction effect of a single layer of reinforcing bars on the surrounding concrete, thus establishing a model to calculate the penetration resistance of multilayer reinforced-concrete targets. Compared with test data for the penetration depth, this model considering the circumferential restriction effect produces better results compared with the existing theory. | Y.J.Deng W.J.Song X.W.Chen | 2019 | Acta Mechanica Sinica2019，35，3： | 3 |
| 6 | EFFECT OF CERIUM ION IMPLANTATION ON THE AQUEOUS CORROSION BEHAVIOR OF ZIRCONIUM显示文摘In order to study the influence of cerium ion implantation on the aqueous corrosion behavior of zirconium, specimens were implanted by cerium ions with a dosage range from 1×1016 to 1×1017 ions/cm2 at about 150℃, using MEVVA source at an acceler ative voltage of 40kV. The valence of the surface layer was analyzed by X-ray photo- electron spectroscopy (XPS); Three-sweep potentiodynamic polarization measurement was employed to value the aqueous corrosion resistance of zirconium in a 0.5mol/L H2SO4 solution. It was found that a remarkable decline in the aqueous corrosion behavior of zirconium implanted with cerium ions compared with that of the as-received zirconium. Finally, the mechanism of the corrosion resistance decline of the cerium-implanted zirconium is discussed. | D.Q.Peng X.D.Bai Q.G.Zhou X.W.Chen R.H.Yu X.Y.Liu | 2004 | Acta Metallurgica Sinica(English Letters)2004，17，6： | 2 |
| 7 | Further numerical investigation on concrete dynamic behaviors with considering stress non-equilibrium in SHPB test based on the waveform features显示文摘In this study,with the meso-scale model reliably validated in our previous work(Construction and Building Materials,2018),the waveform features of plain concrete under various loading conditions and especially with considering stress non-equilibrium are reliably reproduced and predicted.Associating with waveform features,the violation indicator of the specimen stress equilibrium in the split Hopkinson pressure bar test is identified for concrete-like damage softening materi-als.The concrete material behaviors for stress non-equilibrium are further analyzed,e.g.the dynamic increase factor(DIF)and damage development,etc.The conception of“damage failure volume”is introduced,and a new method of defining the development of concrete dynamic damage is given in the nimierical study.What’s more,the“compression wave”and“double peak”phenomena observed in the experiment are further interpreted based on the means of numerical simulation.Waveform features how to reflect the concrete material properties is also concluded.The results show that,the disappearance of the“double peak” phenomenon of reflection curve under high strain rate can be regarded as the indicator of the violation of stress equilibrium.After the violation of the stress equilibrium,the relevant DIFs of the concrete specimen will not change significantly.Especially,the concrete specimen will turn into structural response from material response.The conception of“damage failure volume”can well explain the generation of the“double peak”phenomenon of the reflection curve.The “compression wave” phenomenon of reflection curve under lower strain rates is derived from the unloading expansion recovery of the concrete specimen.Furthermore,under the same loading condition,the amplitude of the first peak of the reflection curve can be used as the evaluation standard of the bonding quality between mortar and aggregates. | T.H.Lv X.W.Chen Y.J.Deng G.Chen | 2020 | Acta Mechanica Sinica2020，36，4： | 1 |
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