Experimental Study on Friction Characteristics of Caragana korshinskii Kom

Xiao LIU,Yuming GUO

College of Engineering,Shanxi Agricultural University,Taigu 030801,China

Experimental Study on Friction Characteristics of Caragana korshinskii Kom

Xiao LIU*,Yuming GUO

College of Engineering,Shanxi Agricultural University,Taigu 030801,China

Caragana korshinskiiKom,which is a kind of excellent shrubs,has strong resistance to windstorms,and it is also a kind of forage that is of high nutritional value as well as a forming fuel conversion resource that is of high caloric.Caragana korshinskiiKom is of high lignifications after growing for a few years and the toughness of it is considerably high.Currently in China,equipments of harvesting and processing for ripe crops can hardly finish the mechanized production forCaragana korshinskiiKom.Friction characteristics of woody material forCaragana korshinskiiKom under different conditions should be given when the relevant operation machinery is designed,which can provide physical parameters for transportation ofCaragana korshinskiiKom as well as the designing of relevant machinery.The paper bases on the research of friction characteristics betweenCaragana korshinskiiKom whose diameter of 7,10,and 13 mm under sampling directions of 0°,45°, and 90°and machinery materials that are commonly used such as steel plate,rubber sheet and so on,and meanwhile the test considers factors such as different conditions ofCaragana korshinskiiKom,different materials of machines,different angles and so on.The data strongly suggests that the average static,dynamic friction coefficient betweenCaragana korshinskiiKom and steel plate is 0.399 711 and 0.353 022,respectively;The average static and dynamic friction coefficient betweenCaragana korshinskiiKom and rubber sheet is 0.965 178 and 0.883 667,respectively.The maximum of static and dynamic friction coefficients is when the angle between the direction of sampling and the direction of movement is vertical.As the angle increased,the dynamic and static friction coefficient decreased.The friction coefficient betweenCaragana korshinskiiKom and steel plate were increased with the increase of the diameter ofCaragana korshinskiiKom,but the diameter have no effect on the dynamic friction coefficient betweenCaragana korshinskiiKom and rubber plate.The conclusion of this paper can provide references for research on machines that are relevant to transportation and particle forming ofCaragana korshinskiiKom.

Caragana korshinskiiKom;Friction characteristics;Thestatic and dynamic friction coefficient;Experimental studyC aragana korshinskiiKom is a drought-resistant and high temperature-resistant shrub with luxuriant foliage and developed roots,which is one of the important species of soil moisture and forestation in the northwest,north,northeast western China;Caragana korshinskiiKom branches contain oils which can be used as a fuel.Caragana branches and leaves contain crude protein 22.9%,crude fat 4.9%,and crude fiber 27.8%;seed contains crude protein 27.4%,crude fat 12.8%,nitrogen free extract 31.6%,and can be used as important feed and fertilizer.Caragana korshinskiiKom can be utilized throughout the years,which bring huge economic benefits.

In recent years,many experts and scholars study onCaragana korshinskiiKom.For example,Wang reviewed the development and utilization ofCaragana korshinskiiKom in western region[1].Reng made a comparative analysis research onCaragana korshinskiiKom particle forming effect of main factors,which include the savagery of raw material,moisture content,particle size,and feed rate,forming pressure,die plate form and temperature of material and so on.It provides references for designing equipments which can processCaragana korshinskiiKom pellet feed and briquettes fuel[2].Liu analyzed the relationship among the cutter displacement,velocity,acceleration and the crank angle,and designed a reciprocating double knifeshrub harvester[3]. Currently in China,equipments of harvesting and processing for ripe crops can hardly finish the mechanized production forCaragana korshinskiiKom. Friction characteristics of woody material forCaragana korshinskiiKom under different conditions should be given when the relevant operation machinery is designed,which can provide physical parameters for transportation ofCaragana korshinskiiKom as well as the designing of relevant machinery.

The research measured the friction characteristics betweenCaragana korshinskiiKom whose diameters were 7,10,and 13 mm under sampling directions of 0°,45°,and 90°and materials commonly used were steel plate,rubber sheet and so on,and analyzed the effects of different conditions ofCaragana korshinskiiKom, different materials of machines,and different angles on friction coefficient. The conclusion of this research can provide references for exploring machines that are relevant to transportation and particle forming ofCaragana korshinskiiKom.

Materials and Method

Caragana korshinskiiKom collected from Suide County,Shaanxi Province.Three species ofCaragana korshinskiiKom samples were collected with different thickness as re-quired including the fine(7 mm),the medium(10 mm)and the thick(13 mm);steel plate and rubber plates are made by me.

Test equipment

MXD-01 type friction coefficient instrument(Labthink)was used in the research.Specifically,theCaragana korshinskiiKom was fixed on the sliding block with glue;the metal material was fixed on the test bench,followed by sliding before the two materials contact for 15 s.The first peak force is static frictionFs,and the average force (exclude static friction)by two samples moving 6 cm relatively to each other is dynamic frictionFd.The display showed the static and dynamic friction coefficient and with the motion of the slide,and the relation curve between the coefficient of friction and tension (Fig.1).Usually,the friction coefficient relates to the pressure,sliding speed, temperature,material and surface roughness and so on[4].The experimental test temperature was 23℃, and humidity was 50%.The slider forwarded at a rate of 10 mm/min,and two specimens moved relative to each other.The curve,test data and the results were shown on LCD.

Testing method

When designing the machines that are relevant to transportation and particle forming ofCaragana korshinskiiKom,it should recognize the friction properties ofCaragana korshinskiiKom with the surface of steel plate and the rubber plate.The friction force was acting on a plane stress(containing one or more contact points in this plane),which resisted to relative motion between the contact surfaces. Friction force is relation to the properties of contact material.According to classical mechanics,friction force is proportional to the pressure,and the constant of proportionality called friction factor[5].

In order to reduce the experimental error,Caragana korshinskiiKom was selected from the same tree.In the experiment,a piece ofCaragana korshinskiiKom was divided into two, and a section was cut and sampled, whose length was the same to the slide,which was fixed on the slide with glue and the steel plate or rubber plate was placed on the test rig.The friction characteristics ofCaragana korshinskiiKom whose diameter of 7,10,and 13 mm under sampling directions of 0°, 45°,and 90°were measured and materials that are commonly used included steel plate and rubber sheet.Each test was repeated 5 times,with a total of 18 sets of data[6].

Calculation formula of the static friction was

where,μsrefers to static friction coefficient;Fsis the static friction force(N);Fpis normal pressure at the cylinder base(N).

Calculation formula of the dynamic friction was

whereμdrefers to the dynamic friction coefficient;Fdis the dynamic friction force(N);Fpis normal pressure at the cylinder base(N).

Results and discussion

Different conditions ofCaragana korshinskiiKom,different materials of machines and different angles of 3 factors were considered in the study. The average value of each set of data was given in Table 1.

The analysis of variance(ANOVA)was conducted using SAS software for the experimental results, which were given in Table 2 and Table 3.

Results showed that the value of significance testing was lower than 0.001(P＜0.001),and different material and different sampling direction has significant effects on the friction coefficient.However,the influence diameter ofCaragana korshinskiiKom’s on the static friction coefficient is clear,but not on the dynamic friction coefficient.Besides,the coefficient of determination of static,and dynamic friction coefficientwere 0.986 1 (R2=0.986 1),0.982 673(R2=0.982 673), respectively.The average static friction coefficient between theCaragana korshinskiiKom and steel plate was0.399 711,and the average dynamic friction coefficient was 0.353 022;the average static friction coefficient between theCaragana korshinskiiKom and rubber sheet was 0.965 178,and the average dynamic friction coefficient was 0.883 667.

Table 1The test results of static(Y1)and dynamic(Y2)friction coefficient ofCaragana korshinskiiKom

The effect of different sampling direction upon the static and friction coefficient

Table 4 and Table 5 showed the results of Duncan’s multiple range tests about the effect of direction,and the level of significance was set at 95%and 99%,respectively.

Experimental results indicated that:(1)Considering the different sampling directions,the static,dynamic friction coefficient betweenCaragana korshinskiiKom and steel plate in descending order are 0°,90°,and 45°,and 0°,45°,and 90°,respectively. There was no significant difference between 45°and 90°.However,there were statistically significant difference among 0°and others;(2)the static,dynamic friction coefficient betweenCaragana korshinskiiKom and rubber plate in descending order are 0°,90° and 45°,and 0°,45°and 90°,respectively.There was no significant difference between 45°and 90°.However, there were statistically significant differences among 0°and others.

Experimental results demonstrated that the maximum of static and dynamic friction coefficients betweenCaragana korshinskiiKom and steel plate is when the angle between the direction of sampling and the direction of movement is vertical.Meanwhile, the dynamic friction coefficient ofCaragana korshinskiiKom decreased with the increase of the angle between the direction of sampling and the direction of movement.Fitted curves were shown in Fig.2 about steel and in Fig.3 about rubber.

The effect of different diameter upon the static and dynamic friction coefficient

Table 6 and Table 7 showed the results of Duncan’s multiple range tests about the effect of diameter,and the levels of significance were set at 95%and 99%,respectively.

Experimental results demonstrated that:(1)considering the different diameters,the static,dynamic friction coefficient betweenCaragana korshinskiiKom and steel plate in descending order are 10,13 and 7 mm, and 13,10 and 7 mm,respectively. There was no significant difference between 10 and 13 mm.However, there were statistically significant differences of 7 mm with others;(2)the static,dynamic friction coefficient betweenCaragana korshinskiiKom and rubber plate in descending order are 13,10 and 7 mm.There was no significant difference between each other. Therefore,the diameter ofCaragana korshinskiiKom had no influence on the friction coefficient between the rubber plate andCaragana korshinskiiKom.

Table 2ANOVA of the static friction coefficient ofCaragana korshinskiiKom

Table 3ANOVA of the dynamic friction coefficient ofCaragana korshinskiiKom

Table 4Duncan’s multiple range tests about the steel

Table 5Duncan’s multiple range tests about the rubber

Table 6Duncan’s multiple range tests about the steel

Table 7Duncan’s multiple range tests about the rubber

Experimental results demonstrated that as the diameter ofCaragana korshinskiiKom increased,the friction coefficient caragana betweenCaragana korshinskiiKom and steel plate increased;however,the diameter of theCaragana korshinskiiKom had no effect on the dynamic friction coefficient ofCaragana korshinskiiKom. Fitted curves were shown in Fig.4 about steel and in Fig.5 about rubber.

Conclusions

According to the analysis of the testing data using SAS software,the following conclusions could be drawn from the study on friction characteristics ofCaragana korshinskiiKom.

(1)The average static,and dynamic friction coefficients betweenCaragana korshinskiiKom and steel plate were 0.399 711 and 0.353 022, respectively.The average static and dynamic friction coefficients betweenCaragana korshinskiiKom and rubber sheet were 0.965 178 and 0.883 667, respectively.

(2)The maximum of static and dynamic friction coefficients betweenCaragana korshinskiiKom and steel plate is when the angle between the direction of sampling and the direction of movement is vertical.As the angle increased,the dynamic and static friction coefficient between steel plate andCaragana korshinskiiKom decreased. The friction coefficient betweenCaragana korshinskiiKom and steel plate increased with the increase of the diameter ofCaragana korshinskiiKom.

(3)The maximum of static and dynamic friction coefficient between rubber sheet andCaragana korshinskiiKom is when the angle between the direction of sampling and the direction of movement is vertical.As the angle increased,the dynamic and static friction coefficient between steel plate andCaragana korshinskiiKom decreased, but the diameter ofCaragana korshinskiiKom had no effect on the dynamic friction coefficient ofCaragana korshinskiiKom.

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Responsible editor:Xiaoxue WANG

Responsible proofreader:Xiaoyan WU

Supported by The 863 Program(2012AA10A509-02).

*Corresponding author.E-mail:guoyuming99@sina.com

Received:May 3,2015 Accepted:June 17,2015