THE TECHNOLOGICAL RESOURCE OF DIGGING AND TRANSPORT HEAVY EQUIPMENTS USED IN ROAD CONSTRUCTIONS

Transcription

1 HE ANNALS OF DUNAEA DE JOS UNIVESIY OF GALAI FASCICLE XIV ECHANICAL ENGINEEING ISNN HE ECHNOLOGICAL ESOUCE OF DIGGING AND ANSO HEAVY EQUIENS USED IN OAD CONSUCIONS rof. univ. dr. ing.laurentiu SÂBU Universitatea ehnic de Construc ii Bucure ti ABSAC For it can be alied the efficiency analysis of a mecanical system on the basis of robabilistic transform and correlation methods in the case of industrial tractors which are working in aggregate with different equiments it must be determined the machine ower on a technological working cycle.. INODUCION he models for the calculation of dynamic stresses in the working outfit and the structure of the machine from the work [] is taking into account F = f ( & ) and of the interaction between the motor transmission and rolling system. 2. HEOEIC ELEENS OF EFFICIENCY OF ECHANICAL SYSES ON HE BASIS OF ANSFOING AND COELAION EHODS he idea of the machines synthesis which use the efficiency s methods consists in the determination of the realisable ossibilities of the basis data concerning the limiting level which indicates the ehausting functional caacity and the working time until the beginning of that moment that is the establishment of the most ossible working term [ 3]. In the case of industrial tractors aggregated with outfits of digging and transorting the ground the basic time is reresented by the secific working cycle for the technology eecuted by the tractor with the bulldozer bulldozer scarificator or the saer [2]. he method is standing at the formal basis of the robabilities transforming of these arameters and of the determination of their statistic characteristics. If there are analysed two accidental sizes which are linked functionally which is the case of construction machines structure with one deendence [for eamle loading which are acting long-term (on the basis of the energetic iterium of the efficiency of the industrial tractor with the hel of the traction diagram [2] taking into account the general energetic otential for tractors aggregated with bulldozer bulldozer scarificator or saer therefore: = F + F + F (.) e s s b where: s b bs - total energetical indicators in the case of the tractor s aggregation with the saer the buldozer and the buldozer scarificator; F s F b F bs - the robability of the aggregation. he total energetic indicator of the ower for the aggregation with all the tyes of outfits is [2] : = (.2) K V where: c b r - the average ower at the hook in kw: K c - the cyclic coefficient deending on the idling seed and on the distribution of the ground work K c = 3 7 s/m; Vr - average real seed in m/s) according to which aear lastic deformations on usage s] then the static characteristic of a single aleatory size y as an accidental function of the argument [y=f()] is determined if it is known the distribution law of. bs bs

2 FASCICLE XIV HE ANNANALS OF DUNAEA DE JOS UNIVESIY OF GALAI 6 the mass of the transorting equiment of the ground; 7 the vertical loadings at the ground working; 8 the distribution of traction forces of the machine; 9 the acting system of the machine the ower and the seed of the Diesel engine Figure a he distribution of loads n in the mechanical systems Figure c. he robability of the entrance and issue arameter at the moment t Figure bhe distribution of issue arameters with n realizations If at the entrance of the system is alied a erturbation (t) ( for eamle given by the loads shae in mechanical systems or of the signals from automatic command systems with a totality of realisations 2 n (figure a) any moment t (on the elements of the working cycle) id characterised by the totality of the distribution (t ). Following the action of these loading the issue arameter has the value y(t) (for eamle the tension of the material for the limiting state the rigid or elastic deformation or the usage which aears in the comounds of the rojected system) (figure b). he dynamic behavior of the tractor working aggregated with digging and transorting equiment s (figure 2) is reresented by the following characteristics of factors are reresenting the loading schedule as: the working rocess of the ground at advance walking of the machine; the idling dislacement of the tractor; 2 the mass of the aggregate; 3 the loading of the machine; 4 the duration for eerimental recording (for de cases a - seer b - bulldozer and c- bulldozer-scarificator ); 5 the recording diagrams of the itical force at the hook with different equiments; 22 hen the distribution totality of this internal arameter is ossible to be determined if it is judged in this way. If it is taken the condition of the equality for robabilities belonging to the entrance arameter at the moment t for the segment X X X + d (figure e) and to the issue arameter in the same moment for the segment y y dy y + then it can be written: from where ( t ) d ( y t )dy = ; (.3) d = ; (.4) ( y t ) d ( t ) dy where is eressed by y varying monotonly the function f(). he relationshi (.4) is the basic equation for transforming the robabilities of the issue arameter which determination resents interest in the rojection of new machines. he rocess itself of seeking for the shae of the formula which determines the robabilistic density curve in any case conjugated with a secial comleity is doing that using the robability method the calculation is tending to a determination of numeric characteristics for moments of the distribution of the aleatory sizes. he first order moment of the mathematical attending suoses the average from the aleatory values of the function (t) which can be eressed in the indeendent eeriences and which are done in the same conditions.

3 HE ANNANALS OF DUNAEA DE JOS UNIVESIY OF GALAI FASCICLE XIV [ ( t) ] ( t)d = (.5) For the comlete characterization of the aleatory function it is necessary to determine the value which indicates the order of disersion for ossible values for aleatory sizes about the average value. he initial moment used for this second order is written as: 2 { [ ( t) ]} = y 2 ( ) ( t) 2 y = Y d (.6) he disersion of the second order central moment is: 2 [( Y my) ] = { y( ) [ Y ( ) ]} ( t d D y = ) (.7) he ultimate relationshi allows to determine the disersion of the issue arameter of the system having known the band function y(t) and the density of the robability for the issue arameter. aking into account the revious considerations the calculation of the robability and durability of the system by heling of the robabilities transformation can be done in the following ordfer [3] : ) here are determined the factors which are influencing on the system behavior which may be desibed as a final number of aleatory arameters using the law of distribution and of robabilities: d d 2 d m ; g g2 gr (.8) where: d d m - the arameters which characterize the internal factors (for eamle when there are known the technological characteristics of the ossible functional and technological arameters realized for equiment; or the arameters which characterize the interior comosition of the system the digression from the geometrical shae the mechanical roerties the surface stage etc.) g gr - the arameters which characterize the loading and another eternal conditions of the eloitation. 2) he grouing indicated of factors suose by self the named sizes of entrance arameters of (machine) or system: y y 2 y m. 3) It is determined the shae of the relationshi between entrance and issue arameters on the basis of eerimental or theoretical data: y I = Y (d d m ; g gr ) I = 2 n (.9) 4) It is determined the density shae that is issue arameters of the system. he working erformances of industrial tractors are ut in evidence by the energetical balance and traction characteristic aggregated with digging and transorting equiments. he schedule of the tractor aggregated with working equiment is resented in the figure 2. In the work [2] are indicated the following working hyotheses: he first hyothesis shows that the energetical balance of the functioning aggregate is a stationary rocess arallel with the dislacement of the mechanical transmission tractor for which is considered the ower balance: where: Figure 2 he working schedule of the tractor in aggregate with road construction equiments[2]. = f s (2.) the ower develoed at the driving wheel = m tr = m tr ; tr the consumed ower for the defeating of frictions during the transmission; tr - the mechanical efficiency of the transmission; 23

4 FASCICLE XIV HE ANNANALS OF DUNAEA DE JOS UNIVESIY OF GALAI f i - the ower for the defeating of the global rolling strength and for the sliing of wheels; F ( δ) = (2.2) F + f G he secific itical ower: a ϕ ( δ) ( ϕ + f ) s s = s f s δ s = s (2.3) where e s ηtr G = a he link between the ower to the wheel and torsion moment t at the shaft of the engine: = ω ; = F r = F + f G ( s a ) r ω ω = ; (2.4) u where: - the angular seed to the wheel; resectively to the shaft of the engine; u - the nominal transmission ratio. u he transmission factor is i =. r he formula (2.9) becomes: F ω = ( F + f s Ga ) ω = i i or ϕ ω s = i he traction forces to the wheel i ηtr F = r or F r = i ηtr where: t is the torsion itical moment at the shaft of the engine. From the adherence condition of the machine results: ϕ G a =. i η tr he secific ower to the driving wheel is a function of : so [( Ga )( ω ) i ηtr ϕ ] (2.5) he itical ower has the shae: 24 = e tr f δ or: = e Nm tr f δ (2.6) where: m the nominal ower corresonding to the itical moment mechanically transmitted. he second hyothesis. he energetical balance characterizes the functioning of the tractor taking into account the statistical values of owers transmitted at the driving wheel by hel of the hydrotransformer. he working moment of the mechanical transmission is reresented by: ( ω )[ ν ϕ ] (2.7) where: the moment of the transmission; - the frequency of the loading. he characteristic given by the dynamical loading moment at the first shaft of the hydraulic transformer is: ω ν (2.8) ( )[ ] ϕ he sliing of driving wheels ) is given by a statistical function. he secific sliing ower of the tractor is a function of: [ δ ( ϕ ) G ϕ ] δ s a ma ν ϕ (2.9) where: ) and δ s - are resectively the sliing coefficient according to the itical adherence coefficient and secific sliing ower given by the dynamical loading of the machine; G a the weight of the working aggregate. he global static coefficient for rolling friction Ff f s = Ga. he consumed ower for defeating the rolling strength f ϕ v G ϕ.) f [ ( ) ] s m a m he energetic balance of owers is: = e Nm H (2.) where: m - the static and dynamic consumed ower as the characteristic of the engine; H - the ower consumed by the hydrotransformer. tr m f δ

5 HE ANNANALS OF DUNAEA DE JOS UNIVESIY OF GALAI FASCICLE XIV 3. HE ENEGEIC OENIAL ON HE CYCLE OF HE EXLOIAION ECHNOLOGY OF HE INDUSIAL ACO AGGEGAED WIH DIFFEEN EQUIENS It is starting from the roductivity of the equiment [2] : W K c = (3.) e where: W is the volume of the ground rism W = K G K K S in which: K the volume coefficient of the material rism in function of the tractor mass; G the tractor weight; K a coefficient taking into account the shae of the blade; K s coefficient of the digging distance of the ground; K = K K ϕ K K - the correction c mot coefficient on a cycle comosed by the roduct of some coefficients which are taking into account: the ower of the engine (K ); the traction force according to the adherence of the machine (K ); the functioning characteristic of the engine (K mat ); the transformation of the working otential roductivity into the real one (K t ); c the duration of the working cycle secific to the aggregate industrial tractor working equiment. he necessary technological ower deending on the traction itical force (at the hook in the case of eeriments) develoed as well as the working seed during the digging rocess on a cycle is A F V τ (3.2) t = where is the time factor τ = (3.3). c For the working technology of the buldozer the working cycle has the form: S S = (3.4) c + + int = + + int V V where: int are necessary working times for digging without loading or the time of returning; S S working distances for digging transorting and resectively idling. Introducing (3.4) into (3.3) the factor of time is: τ = + V (3.5) int + S S Figure 3 - he characteristic of the tractor with an engine of 585 kw; the sliing factor according to the work [ 2 ] If it is introduced (3.5) into (3.2) the necessary ower on a working technological cycle results according to the digging itical ower: A = (3.6) int + + V V S It is considered the ower according to [2] of a tractor of 58 kw which is working aggregated with a bulldozer - scarificator of t. he working characteristic of the tractor is resented in figure 3. he notations done have the following semnification: A(F ) - the necessary working ower on a technologic cycle; (F ) - the ower characteristic according to the traction itical force at the realzation of digging workings; - the sliing characteristic of wheels. he function A(F ) is corresonding for the working conditions of sliing 3% which assures the itical ower of the tractor at digging. It is determined from the relation (3.6) A(F ) on the basis of the tractor characteristics from figure 3. he traction characteristics F (t) and F (t) are given on the basis of the ower. he relationshi (3.6) is calculated knowing and V according to F (t) when t. he energetic otential at the shaft of the driving wheel as a function of F and V is: 25

6 FASCICLE XIV HE ANNANALS OF DUNAEA DE JOS UNIVESIY OF GALAI = + V where: and V + S int ( F ) f ( F ) ( F ) f ( F ) df ( F ) f ( F ) df V df ( F ) f ( F ) df (3.7) are the distribution of the ower and the seed according to the traction itical force in the digging rocess. he values F and V r from the revious relationshis (including the relationshis (.2)) is determined for each tye of aggregate using the adherent weight of the tractor with the bulldozer bulldozer scarificator and the saer with the graho analytical method and the traction diagram [ 2]. 4. CONCLUSIONS he ower of the machine on a technologic cycle deending on the itical force of the tractor aggregated with different equiments ermits the raising of real loadins for the analysis of the durability usage and the structure. EFEENCES [].AN GH. SÂ BU L. LADIN GH. a ini de trac iune i de ridicat entru construc ia c ilor de comunina ie artea a-3-a I.C.B. Bucure ti 985 ag ; [2]... ENOB A.. e 986 ag 58 59; [3]... D 98 ag 38 44; 26