| This paper was based on the third phase of lunar exploration project in China,to get the samples of lunar soil.The formation and design of tubular fabrics for unmanned drilling and sampling and its pull-out behaviour in drilling and sampling device were studied.The main purpose of this research was to provide the preliminary design idea and data reference for lunar exploration.Meanwhile,this paper provided a reference for further study of other mechanical properties of high-performance tubular fabrics,which is of crucial academic significance and practical engineering value.Firstly,two high-performance tubular fabrics made from aramid filament yarns were designed for drilling and sampling.For weaving and formation of woven tubular fabrics,a specially small shuttle was developed.Picking with the configuration of weft picking lever and the small shuttle,the weft tension of small diameter woven tubular fabrics was well adjusted.Consequently,woven tubular fabrics with good circumferential uniformity were manufactured.In addition,tubular fabrics with radial shrinkage and expansion feature were designed and developed.Through the cross rotation of the two cross-yarns at the intersection point,it achieved good adherent from the outside of the rigid round pipe to the inside.Hence,the radial adaptability of tubular fabrics was effectively improved.Secondly,the mechanical and tribological properties of two kinds of high-performance tubular fabrics and the component aramid filament yarn were conducted systematically using a multi-functional electronic fabric strength tester,yarn friction coefficient tester and KES-FB-4 surface performance tester in this paper.It was found that the selected aramid filament yarn had a strong ability to resist external tension and good axial tensile properties.Moreover,its frictional coefficient was low,only about 0.33,thus,the smoothness was better.The tensile and frictional indexes of the two high-performance tubular fabrics of three different radii have been analyzed.It was found that the tensile parameters of the tubular fabrics increased with the increase of the radii.Compared with woven tubular fabrics,the fracture strength of the tubular fabrics with radial shrinkage and expansion,fracture strength Fb,initial modulus E0 and fracture specific work W were all smaller than that of the woven fabrics with the same radius.It was also proved that the structure of the tubular fabrics with radial shrinkage and expansion has been adjusted during the stretch process,due to the cross rotation of the two cross-yarns at the intersection point,which,in turns,resulted a larger extension at break.The friction test showed that the frictional coefficients of the two high-performance tubular fabrics were roughly the same and low,about 0.35,and it had good smoothness,which is beneficial to the realization of the pull-out behaviour of the tubular fabrics during drilling and sampling.Then,some preliminary trials were made in this paper to design two measuring devices for testing the pull-out behaviours of tubular fabrics,however,in view of the actual requirements for drilling and sampling,especially,with the goal to obtain the deep soil samples and test the pull-out behaviours of the tubular fabrics,a measuring device for testing pull-out behaviours of tubular fabrics during drilling and sampling process was elaborately developed based on the design of the above two devices.The pull-out force-time(F-t)curves of the high-performance tubular fabrics can be obtained by this designed device,and the maximum force Fmax and the maximum pull-out force variation rate ?Fmax of two different high-performance tubular fabrics can be obtained.According to the two indexes,the pull-out behaviours of high-performance tubular fabrics with different lengths and radii,as well as two different types of high-performance tubular fabrics in the same length and radius can be well evaluated.In addition,using the theory of relative motion,the principle of force balance,the Euler formula of the flexible body and the Amontons law,this paper analyzed the interaction between tubular fabrics and rigid round pipe in three important parts: the outer wall,the inner wall and the corner of rigid round pipe.The stress values of tubular fabrics in different parts and during the whole drilling and sampling were obtained by mathematical calculus,and some key factors that affected the pull-out force of tubular fabrics were revealed.The analysis of pull-out force showed that there was a linear relationship between the pull-out force and the time when the tubular fabrics and its matched rigid round pipes were determined.The test showed that the woven tubular fabrics had a very obvious fold at the corner of rigid round pipe,even a larger fold,which seriously affected its pull-out behaviours,and made the motion of tubular fabrics in the inner wall of rigid round pipe be greatly hindered.In contrast,the structural deformation of the two cross-yarns at the intersection of the tubular fabrics with radial shrinkage and expansion made it no obvious folds,which means that it was better attached to the rigid round pipe,and was more suitable for drilling and sampling.Finally,a comprehensive study of two factors affecting the length and radius of the pull-out force of tubular fabrics has been reported.It was found that the theoretical and obtained experimental F-t curves of the two high-performance tubular fabrics both showed a gradual increasing trend.In contrast,the theoretical F-t curve was lower than the experimental one because of the idealized hypothesis of the theoretical model,that is,the actual pull-out forces of two high-performance tubular fabrics were larger.The analysis of the same length and the same type of high-performance tubular fabric showed that the pull-out force F increased with the increase of the radius,and the corresponding parameter Fmax became larger.The two kinds of high-performance tubular fabrics with the same length and radius were analyzed.It was found that the pull-out forces of the tubular fabrics with radial shrinkage and expansion were smaller because of the structural adjustment in the process of drilling and sampling.Moreover,from the maximum pull-out force variation rate ?Fmax,it can be seen that the maximum pull-out force of tubular fabrics with radial shrinkage and expansion decreased by about 30% compared to the woven tubular fabrics,which fully indicated that the tubular fabrics with radial shrinkage and expansion had a better recovery and pull-out behaviour. |
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