TRACTIVE PERFORMANCE ANALYSIS ON RADIALLY DEPLOYABLE WHEEL CONFIGURATION OF LUNAR ROVER VEHICLE BY DISCRETE ELEMENT METHOD

With the consideration of volume constraint of launch vehicle and trafficability of rover vehicle on lunar regolith terrain, a new design of radially deployable wheel is presented. For the purpose of achieving the meso-mechanics and dynamical behavior of lunar soil particles as well as macro-parameters of tractive performance for radially deployable wheel, the interaction between two types of wheel configurations and lunar soil particles is analyzed by means of discrete element method. The network of contact forces, the displacement vector chart, and the deformation of lunar soil beneath wheels are plotted. The equations of soil thrust, motion resistance, drawbar pull and driven torque are derived in granular scale based on the coordinates transformation and algebraic summation. The calculated results show that there is sufficient traction for both 6-split and 12-split radially deployable wheels with 304 mm outspread diameter to negotiate lunar regolith terrain specified here; the value of drawbar pull enhances with the increase of split number of radially deployable wheel, however, the required driven torque increases simultaneously, therefore, the tractive efficiency decreases.

Highly Improved Electrochemical Performances of the Nanocrystalline and Amorphous Mg_2Ni-type Alloys by Substituting Ni with M (M=Cu,Co,Mn)

The element Ni in the Mg2Ni alloy is partially substituted by M（M = Cu, Co, Mn） in order to ameliorate the electrochemical hydrogen storage performances of Mg2Ni-type electrode alloys. The nanocrystalline and amorphous Mg20Ni10-xMx（M = None, Cu, Co, Mn; x = 0-4） alloys were prepared by melt spinning. The effects of the M（M = Cu, Co, Mn） content on the structures and electrochemical hydrogen storage characteristics of the as-cast and spun alloys were comparatively studied. The analyses by XRD, SEM and HRTEM reveal that all the as-cast alloys have a major phase of Mg2Ni but the M（M = Co, Mn） substitution brings on the formation of some secondary phases, MgCo2 and Mg for the（M = Co） alloy, and Mn Ni and Mg for the（M = Mn） alloy. Besides, the as-spun（M = None, Cu） alloys display an entirely nanocrystalline structure, whereas the as-spun（M = Co, Mn） alloys hold a nanocrystalline/amorphous structure, suggesting that the substitution of M（M = Co, Mn） for Ni facilitates the glass formation in the Mg2Ni-type alloys. The electrochemical measurements indicate that the variation of M（M = Cu, Co, Mn） content engenders an obvious effect on the electrochemical performances of the as-cast and spun alloys. To be specific, the cyclic stabilities of the alloys augment monotonously with increasing M（M = Cu, Co, Mn） content, and the capacity retaining rate（S20） is in an order of（M = Cu） 〉（M = Co） 〉（M = Mn） 〉（M = None） for x≤1 but changes to（M = Co） 〉（M = Mn） 〉（M = Cu） 〉（M = None） for x≥2. The discharge capacities of the as-cast and spun alloys always grow with the rising of M（M = Co, Mn） content but first mount up and then go down with increasing M（M = Cu） content. Whatever the M content is, the discharge capacities are in sequence：（M = Co） 〉（M = Mn） 〉（M = Cu） 〉（M = None）. The high rate discharge abilities（HRDs） of all the alloys grow clearly with rising M（M = Cu, Co） content except for（M = Mn） alloy, whose HRD has a maximum value with varying M（M = Mn） content. Furthermore, for the as-cast alloys, the HRD is in order of（M = Co） 〉（M = Mn） 〉（M = Cu） 〉（M = None）, while for the as-spun（20 m·s^-1） alloys, it changes from（M = Co） 〉（M = Mn） 〉（M = Cu） 〉（M = None） for x = 1 to（M = Cu） 〉（M = Co） 〉（M = None） 〉（M = Mn） for x = 4.

Structure and electrochemical properties of LaMgNi4-xCox(x=0-0.8)hydrogen storage electrode alloys

LaMgNi（4-x）Cox（x = 0-0.8） electrode alloys used for MH/Ni batteries were prepared by induction melting. The structures and electrochemical hydrogen storage properties of the alloys were investigated in detail.X-ray diffraction（XRD） and scanning electron microscopy（SEM） analysis show that LaMgNi4 phase and LaNi5 phase are obtained. The lattice parameters of the two phases increase first and then decrease with Co content increasing.The electrochemical properties of the alloy electrodes were measured by means of simulated battery tests. Results show that the addition of Co does not change the discharge voltage plateau of the alloy electrodes. However, the maximum discharge capacity increases from 319.9 mAh·g^-1（x = 0）to 347.5 mAh·g^-1（x = 0.4） and then decreases to331.7 mAh·g^-1（x = 0.8）. The effects of Co content on electrochemical kinetics of the alloy electrodes were also performed. The high rate dischargeability（HRD） first increases and then decreases with Co content increasing and reaches the maximum value（95.0 %） when x = 0.4. Test results of the electrochemical impedance spectra（EIS）,potentiodynamic polarization curves and constant potential step measurements of the alloy electrodes all demonstrate that when Co content is 0.4 at%, the alloy exhibits the best comprehensive electrochemical properties.

Analysis of Angular Side Berthing Against a Rubber Cone Fender

This paper analyzes fender selection process in berth design and focuses on the case of a rigid berth with rubber cone fenders.Fender types and performance comparison methods are studied along with current numerical models.Berth design methods are analyzed with a focus on berthing energy calculation and fender selection.A new approach to determine the required fender capacity is suggested.A finite elements rubber cone model is tested and used in simulations of angular side berthing.Results show that the energy absorbed by the fender can be much higher than what can be calculated with the current berth design method.A new form for the expression of the energy that must be absorbed by the fender during angular berthing impact is suggested.