An efficient means of transport, over short distances and heavy-duty traction on roads maintained or unmaintained field, agricultural land is considered system tractor - trailer. This article presents the results of experimental research on the dynamic behavior of the system tractor - trailer suspension system provided with agricultural roasted. The variety of constructive solutions for hitches with suspension motivated interest in experimental research of the effects caused by the introduction of elastic elements (leaf springs), fried farm semitrailer. They studied three variants of hitches compared with suspension and without suspension version. To highlight how it influenced the dynamic behavior of the studied system, were determined and analyzed for the following parameters: its spectrum of frequencies, maximum amplitude of vertical acceleration root mean square of the accelerations respectively

Ciuperca, R.

Lazar, G.

Nedelcu, A.

Petcu, A.

Popa, L.

Stefan, V.

Zaica, A.

An efficient means of transport, over short distances and heavy-duty traction on roadsÂ maintained or unmaintained field, agricultural land is considered system tractor - trailer. ThisÂ article presents the results of experimental research on the dynamic behavior of the systemÂ tractor - trailer suspension system provided with agricultural roasted. The variety ofÂ constructive solutions for hitches with suspension motivated interest in experimental researchÂ of the effects caused by the introduction of elastic elements (leaf springs), fried farmÂ semitrailer. They studied three variants of hitches compared with suspension and withoutÂ suspension version. To highlight how it influenced the dynamic behavior of the studiedÂ system, were determined and analyzed for the following parameters: its spectrum ofÂ frequencies, maximum amplitude of vertical acceleration root mean square of theÂ accelerations respectively

Annals of the University of Craiova - Agriculture, Montanology, Cadastre Series

Analele Universităţii din Craiova, seria Agricultură – Montanologie – Cadastru (Annals of the University of Craiova - Agriculture,Montanology, Cadastre Series) Vol. XLV 2015137TECHNICAL ASPECTS ON DYNAMIC BEHAVIOR OF THESEMITRAILERS WITH SUSPENSION HITCHNEDELCU A.1), CIUPERCA R.1), POPA L.1), ZAICA A.1), LAZAR G.1)ŞTEFAN V.1), PETCU A.,1)INMA Bucharest;E-mail: nedelcu.ancuta@yahoo.comKeywords: agricultural semitrailers, hitch with suspension, vibration,ABSTRACTAn efficient means of transport, over short distances and heavy-duty traction on roadsmaintained or unmaintained field, agricultural land is considered system tractor - trailer. Thisarticle presents the results of experimental research on the dynamic behavior of the systemtractor - trailer suspension system provided with agricultural roasted. The variety ofconstructive solutions for hitches with suspension motivated interest in experimental researchof the effects caused by the introduction of elastic elements (leaf springs), fried farmsemitrailer. They studied three variants of hitches compared with suspension and withoutsuspension version. To highlight how it influenced the dynamic behavior of the studiedsystem, were determined and analyzed for the following parameters: its spectrum offrequencies, maximum amplitude of vertical acceleration root mean square of theaccelerations respectively.INTRODUCTIONIn agriculture, is transported large quantities of goods and materials. Agriculturaltransport is a main component of the agricultural production process aimed at movingmaterials and products rather than amending their physico-mechanical properties.Transportation equipment used in agriculture as energy source is classified into twocategories: auto propelled transport means (vehicles with own transport platform) andtransport trailed (trailers and semi-trailers). [5, 7].Power increases and the need to manufacture tractors appeared appropriate theirtrailers.In recent years we have seen spectacular diversification in agricultural semi-trailersconstructively and increase transport capacity up to 30 t.This was due, in large part, the advantages that are gained by using semi-trailerscompared with two-axle trailers: tare ratio increased; handling and good ride; simplerconstruction; price lower cost; fuel economy, etc. Also characteristic is that the trailer hitchtransferred by a significant part of its weight and thus traction device of the rear axle of thetractor, increasing its adherent weight, and therefore the traction force.However, because of this link: shock, vibration and dynamic loads resulting, inparticular, due to the action of the vertical force component of interaction between thewheels and the road, which is considered a drawback to be reduced or even removed aretransmitted to the tractor. [3,10]To reduce these drawbacks, especially for the comfort, acted in several directions:improving suspension tractor seat, improved suspension axles on semitrailers, andintroducing a system of suspension with leaf springs fried semitrailer. [1, 2, 6, 8]The diversity of existing constructive solutions for hitch with suspension of high-capacity semi-agricultural, prompted conducting theoretical and experimental research onthe dynamic behavior of the system tractor - trailer equipped with suspension roasted. [4,9].Analele Universităţii din Craiova, seria Agricultură – Montanologie – Cadastru (Annals of the University of Craiova - Agriculture,Montanology, Cadastre Series) Vol. XLV 2015138MATERIAL AND METHODOf the many constructive solutions existing and analized there have been chosenfor the research, those that stood by simple technical solutions, and representative of thattype, and easily assimilated into production series. Thus, they designed, built and tested infour different working conditions hitchs:I - hitch without suspension (rigid drawbar symbolized PR);II - suspension hitch with longitudinally mounted under the frame (symbolized PSLA, fig.1);III - mounted hitch suspension with transverse (symbolized PST, fig. 2);IV - spit with suspension mounted longitudinally in front frame (symbolized PSLR, fig. 3).Fig. 1. Hitch with the suspension longitudinally set under the gripping device (PSLA):1 - hitch; 2 - tow-rope hoop; 3 - leaf type spring; 4 - elements for fixing the chassis spring;5 - spring bolt; 6 - chassis; 7 - hitch support; 8 - elements for fixing the spring to the hitch;Fig. 2 Hitch with the suspension transversally set (PST):1 - hitch; 2 - tow-rope hoop; 3 - leaf type spring; 4 - elements for fixing the chassis spring; 5 -spring bolt; 6 - chassis; 7 - hitch support; 8 - elements for fixing the spring; 9 - supportFig. 3. Hitch with the suspension longitudinally set in front of the gripping device (PSLR):1 - welded hitch; 2 - tow-rope hoop; 3 - leaf type spring;4 - body for connection andadjustment; 5 - spring bolt; 6 - chassis; 7 - hitch support; 8 - wheels;9 - bearing cross rail of the springTo study the effects of vibration occurring in aggregate real working conditions,were carried out tests that required assembly and the necessary equipment. located in thediagram of Figure 4.For conducting experiments worked in the system U 650 wheeled tractor andequipment used technique for performing measurements and special registration: DAPdata acquisition system for 2400, laptop, inductive type accelerometers B12 / 200-Analele Universităţii din Craiova, seria Agricultură – Montanologie – Cadastru (Annals of the University of Craiova - Agriculture,Montanology, Cadastre Series) Vol. XLV 2015139company Hottinger; Analog Devices 3B20-type amplifier-company Hottinger; U650 tractorbeam voltage, cod.DFT-65.0, which are mounted strain gauges; specialized programs forprocessing: MATHCAD; nSOFT, MATLAB.Fig.4. Scheme of the system and placing of the technical device necessary for recording theterrain signals:1 – wheeled tractors U 650 M (power of 65 CP); 2 – semi-trailer (total mass 9300 kg); 3 –acceleration transducers; 4 – acquisition and signal processing device; 5 –transducer formeasuring the traction force.The testing of every type of aggregate tractor-semi-trailer has been carried out undersimilar conditions, upon two types of road (concrete and earth road) with values of the irregularitiesheight h0 and of the irregularities length (step) L within the limits offered in Table 1.Table 1Characteristics of the irregularities of the experimental roadsRoad typeh0 L[mm] [m]Concrete road 10…20 3…5Earth road 20…30 0.15…0.3RESULTS AND DISCUSSIONSIn the framework of the experimental research there have been effected 28experiments during which there have been realized recordings with the samplingfrequency of 500 Hz.The results of the signal processing obtained within the effected tests are centrallypresented in the tables 2 … 5, the significance of the notations being as follows:Żtmax , RMSzt - maximal amplitude of the vertical acceleration, measured at the tractor floorand, respectively, the average square root of these accelerations;Żpmax, RMSzp – maximal amplitude of the vertical acceleration, measured on the hitch and,respectively, the average square root of these accelerations;Żrfmax, RMSzrf – maximal amplitude of the vertical acceleration, measured at the fronttransverse cross bar and, respectively the average square root of these accelerations;Żrsmax, RMSzrs – maximal amplitude of the vertical acceleration, measured at the backtransverse cross bar and, respectively, the average square root of these accelerations;Analele Universităţii din Craiova, seria Agricultură – Montanologie – Cadastru (Annals of the University of Craiova - Agriculture,Montanology, Cadastre Series) Vol. XLV 2015140Table 2Performances of the aggregate tractor + semi-trailer in the PR variantRoad type Speed[km/h]Parametersmaxtzmm/s2RMS ztmm/s2maxpzmm/s2RMSzpmm/smaxrfzmm/s2RMS zrfmm/s2maxrszmm/s2RMSzrsmm/s2Concreteroad11.8 6.16 2.176 4.12 0.996 6.73 1.218 0.93 0.29411.8* 5.08 2.056 3.62 0.895 30.75 1.123 1.03 0,36423.0 7.52 2.386 6.22 1.524 5.78 2.136 0.91 0.34816.9* 5.44 2.045 3.96 1.141 4.6 1.365 1.02 0.327Earth road10.9 6.59 2.037 4.54 0.919 4.57 1.273 1.03 0.3978.5 4.76 1.997 4.7 0.72 4.05 0.876 0.79 0.3267.0 4.31 1.920 2.88 0.688 2.31 0.761 0.75 0.307* brakingTable 3Performances of the aggregate tractor + semi-trailer in the PSLA variantRoad type Speed[km/h]Parametersmaxtzmm/s2RMS ztmm/s2maxpzmm/s2RMSzpmm/smaxrfzmm/s2RMS zrfmm/s2maxrszmm/s2RMSzrsmm/s2Concrete road12.1 6.41 2.187 7.96 2.948 4.89 1.013 0.52 0.3411.7* 4.91 2.087 7.72 3.42 2.79 0.894 0.67 0.22823.3 7.77 2.263 12.98 4.515 5.24 1.456 0.72 0.2417.3* 5.45 2.215 11.06 3.8 3.98 1.365 0.54 0.272Earth road11.3 4.42 1.912 7.96 3.27 2.99 0.937 0.7 0.2238.7 4.88 1.933 9.46 3.469 2.22 0.746 0.64 0.3567.9* 4.15 1.918 8.72 3.69 2.03 0.657 0.93 0.204* brakingTable 4Performances of the aggregate tractor + semi-trailer in the PST variantRoad type Speed[km/h]Parametersmaxtzmm/s2RMS ztmm/s2maxpzmm/s2RMSzpmm/smaxrfzmm/s2RMS zrfmm/s2maxrszmm/s2RMSzrsmm/s2Concreteroad12 6.40 2.285 9.04 3.639 5.6 0.988 0.76 0.28011.9* 4.95 2.175 8.54 3.745 3.12 0.92 1.31 0.82525.0 7.85 2.751 12.14 3.727 5.15 1.809 0.32 0.48216.6* 6.12 2.335 12.22 4.047 4.49 1.553 0.29 0.479Earth road11.5 5.88 2.14 8.88 3.441 3.7 1.103 0.74 0.2989.5 5.12 2.086 7.12 3.336 2.8 0.782 1.02 0.3278.2 4.58 1.978 6.8 3.019 1.84 0.6 0.68 0.185* brakingAnalysis of the dynamic behavior of each type of aggregate was made bycomparing the values obtained for each parameter studied. The procedure consisted ingiving percentage points and dynamic performance achieved, the results were pooled andresults the following ranking: • first prize with 28.79%, + semitrailer tractor hitch unit type PSLA; • Second place with 24.24% + semitrailer tractor hitch unit PST; • Third place with 23.48% aggregates formed by tractor + semitrailer variants rigidhitch PSLR and PR.Analele Universităţii din Craiova, seria Agricultură – Montanologie – Cadastru (Annals of the University of Craiova - Agriculture,Montanology, Cadastre Series) Vol. XLV 2015141Table 5 presented frequency spectrum selected from entries, and assigned to fourexperimental versions :Table 5Own frequency spectrum of the four variants testedVariant hitch Spectrum own experimentallydetermined [Hz]Rigid hitch , PR 1.67; 2.45; 2.9; 5.2Hitch with suspension mounted transverselyPST 1.67; 2.2; 2.8; 5.7Hitch with longitudinally mounted suspensionunder the semi-trailer chassis, type psla 1.63; 2.2; 2.9; 4.35Hitch with suspension mounted longitudinallyin front of the chassis, type DSLR 1.6; 2.6; 2.9; 4.6It has also been found that the spectrum all signals contain high frequencies of 50to 65 Hz, derived from the fluctuations caused by the transmission of the tractor, a packetof frequencies around 33 Hz, the frequency coming from the engine and generally one twofrequencies of 27 Hz around, coming all the organs tractor ride.By comparison with the results of [3], Volume 3, the oscillation of the sprung massof the trailer is properly located somewhere in the range 3 to 5 Hz, the tractor provides boband pitch frequencies somewhere between 2 and 4 Hz. Therefore its spectrum selectedspectra is consistent with the same kind of machinery, published in the literature.Also after [3], the frequencies determined from experimental records fit perfectlywithin corresponding frequency range of agricultural tractors and trucks and thecorresponding frequency range of vehicles with tires earth moving.CONCLUSIONS-Apart from the testing variants on concrete road at high speed moving along (whenthe moving along speed during the tests was characterized by different values), there hasbeen effected a statistic analysis of the performances of the four types of aggregatestractor-semi-trailer which have been experimented (3 aggregates with semi-trailers withelastic hitch, in the mentioned variants, and an aggregate with rigid hitch).-The analysis of the dynamic behavior of each type of aggregate has beenaccomplished by comparing the values obtained for the studied parameters, accordinggrades (points) for the studied dynamic performances. This way, for the aggregate whoseparameter value indicates a disadvantageous situation there has been granted a singlepoint, and for the other aggregates there have been granted, comparatively, up to 4 points.-The statistics resulted from the even-leveled average of all hierarchies hasenhanced that the best performances (that is a better dynamic behavior for mostparameters) have been obtained for the hitch with the suspension longitudinally set underthe chassis of the semi-trailer, type PSLA (fig. 1), followed by the hitch variant with thesuspension transversally set under the chassis of the semi-trailer, type PST (fig. 2). On thelast places there has been classified the hitch with the suspension longitudinally set infront of the gripping device type PSLR (fig. 3) and the rigid hitch (with no suspension).-It is also to be noted that not any chosen elastic connection (setup variant, typeand rigidity of the spring) for the suspension hitch improves the performances of theaggregate, there existing the possibility for the functional characteristics of the system todeteriorate in case of an inadequate choice.-The semitrailers are used in combination with agricultural tractors for transportsystems, due to their smaller constructive weight and total length compared to trailers, andparticularly due to their positive influence on transport and braking dynamics. ThisAnalele Universităţii din Craiova, seria Agricultură – Montanologie – Cadastru (Annals of the University of Craiova - Agriculture,Montanology, Cadastre Series) Vol. XLV 2015142influence is achieved by the contribution to increasing the tractor adhesion load,consequently to the transfer of a part of the semitrailer weight upon the tractor. Thesemitrailer, having only one axle, has as a second supporting point the coupling devices ofthe tractor, located at the inferior part of the tractor rear.-In order to reduce the shortcoming determined by the vibrations and shockstransmitted by semitrailer to tractor it aims at improving the suspension system at tractorseat and trailer’s axles level and in the same time particular constructive solutions forsemitrailers with a suspension system at the hitch.BIBLIOGRAPHY[1] Bodea C., Cândea I., Popescu S., 2008, Studies and Researches Regarding theStreet-Traffic Security of the Tractor-Trailer Aggregate and of The Agricultural Equipments/Scientific Papers INMATEH- Alternative Energies, Mechanizing Technologies and EfficientTechnical Equipment for Agriculture And Food Industry contents no.. 26,p. 72-76, Nr. 3/2008,[2] Cândea I., Bodea C., Bria N., Andrei I., 2008, The Kinematic And Dynamic Analysis OfThe Spheric Couple As Coupling Organ Between The Tractor And The Semitrailer , ScientificPapers INMATEH- Alternative Energies, Mechanizing Technologies and Efficient TechnicalEquipment for Agriculture And Food Industry Contents no.. 26,, p.77-82, ISSN 1583-1019.[3] Cyril M. Harris, Charles E. Crede, 1969, Shocks and vibrations, Technical PublishingHouse, Bucharest[4] Dima I., 2000, Contributions to study of vibrations of subassemblies of agriculturalmachinery, PhD-Thesis, University Politehnica, Bucharest / Romania[5] Dragutan V. Demetrescu I. 1984, Mechanization of transport in agriculture, CeresPublishing House, Bucharest[6] Ionel Andrei, Ioan Cândea, Nicolae Bria , 2009, Kinetic-Dynamic Analysis of the FarmTractor & Twin-Axle Trailer Combination in Various Mechanical States, Scientific PapersINMATEH, Contents no 28, Nr. 2/2009, p. 4-7, ISSN 1583-1019[7] Francisc C. Ciupercă R., 1997, Considerations about modern agricultural transport,Scientific Papers, INMA Bucharest[8]. Mocanu V., Hermenean I., (2010) Experimental Researches Concerning Dynamicsand Energetics of Two-Wheel Tractor - Semitrailer Systems, INMATEH- AgriculturalEngineering, Contents no 32, Nr. 3/2010, p. 59-64, e: ISSN 2068-2239, p ISSN 2068-4215.[9]. Nedelcu A., 2008, Suspension systems for agricultural trailers, Terra NostraPublishing House, ISBN 978-973-8432-93-2.[10]. Şandru A. et all., 1983 „ Exploiting farm machinery” Publisher Didactic andpedagogic, Bucharest.

TECHNICAL ASPECTS ON DYNAMIC BEHAVIOR OF THE SEMITRAILERS WITH SUSPENSION HITCH

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TECHNICAL ASPECTS ON DYNAMIC BEHAVIOR OF THE SEMITRAILERS WITH SUSPENSION HITCH

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Annals of the University of Craiova - Agriculture, Montanology, Cadastre Series