Jurčiová, Jana

Šarlajová, Martina

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tJ tba, nik V�ec�c��� Vysoké školy báňské- Technické univerzity Ostravačíslo I, rok '.?008, ročník LI, řada hutnická článek č. 1399 QUANTIFICATION OF ADHESION BETWEEN RUBBER AND STEEL CORD BY ULTRASONIC DEFORMATION J. JURČIOYÁ 1 , M. ŠARLAJOVÁ2 1 Facu/ty of industria/ technologies TnUAD; Púchov, Slovakia,jurciova@fpt.tnuni.sk1 Facu/ty ofindustria/ techno/ogies TnUAD; Púchov, S/ovakia, sar/ajova@fpt.tnuni.skABSTRACT: This work deals with problematic of fatigue lifetime of adhesion bond between rubber and steel cord material. Like an experimental material was taléen the part of radia! tire which is the most stressed part under defonnatior1 during lifetime oftire. The main aim·ofwork was detennination of adhesion bond level between steel cords of construction 3x0,20+6x0,35 HT, bead wire with diameter 1,6 mm and two different rubber compounds used in belt and bead �rea of truck tyre. A special attention is paid to development and possibility to apply in practise of new test method, which makes possible to strain test sample by high-frequency ultrasonic oscillation. This non standard method provides many advantages in comparison with other adhesion test method. The results are discussed and compared with the results were obtained by static tensile adhesion T - test and dynamic cycling Henley - test. KEY WORDS: steel cord-rubber adhesion, ultrasonic frequency, tire test method 1. INTRODUCTIONThe performance of all steel-belted radia! tires is, to a large extent, dependent on the strength and durability of the bond fonned during the vulcanization between tne rubber of the tire cord coating stock and the steel reinforcement which is assorted in wire constructions[l].The mechanism ofrubber­brass bond formation and particularly of adhesion degradation is extremely complex and dependent on a large number of variables, which include both cord and compound parameters[2].The mechanical fatigue in the elastomeric materials like rubber is demonstrates progressive drop of their physical properties due to repeated deformation much lower than the· braking strain, resulting in unserviceability of an article during use [3]. It is generally attributed to tne growth of the repeated tearing from tlaws under application of dynamical strain or defonnation in the test piece. This may be accentuated by the rise in temperature due to repeated defonnation and chemical changes. The considerable change is the low-pitched change of stiffness. Prolongation of the static strain can cause the stress relaxation as well as time-dependent cracks propagation of many synthetic rubbers. Bene�cial -effect on the fatigue life of crystallizing rubber occurs, because the crystalline barrier to tearing at-the tips ofthe tlaws will not disappear. According to long-time performance of tires and different service conditions the tire producers making intensive use of a large numbers of tire aging simulation tests [4,5,6] possible degradation phenomena that may occur in the different tire areas, e.g. bead, carcass, shoulder and breaker, a correct simulation ofthe composite sample is necessary. The requirements for adequate adhesion testing include repeatability and reproducibility, sensitivity to interfacial cohesion force measurement, and the possibility of aging. The commonly used test to evaluate steel cord-rubber adhesion is the ASTM D-2229 test, a pull-out test where the force needed to pull a cord out of rubber is described. Simultaneously the coverage of rubber on cord 230 is rated. A large number of investigations also aimed at evaluating the adhesion retention after cyclic loading. For research purposes the Henley test is more suitable and often use [7]. 2. FORMATION' Experimental composites were prepared in the form to simulate the most stressed part under deformation during lifetime of truck tire, the shoulder and the bead area. Ali experiments were realised with two kinds of reinforcement materials: steel cord with construction 3x0,20+6x0,35 HT, bead wire with diameter 1,6 mm. Two of used rubber compounds have different chemical composition and properties. Rubber compound A contains from natural rubber matrix. Compound B has polymer matrix from polybutadien-styren. To investigate the influence of static and dynamic loading combination on adhesive bond of experimental specimens there was a new test method developed, which provide the cyclic deformation of composite with using ultrasonic working frequencies ( f ::::: 20 kHz), means 20 I 00 cycles/sec. a simultaneously the sample was statically loaded with selected weight (221]. Fig. 2 shows schematically of ultrasonic fatigue test machine. The machine is centered around an acoustic amplifying horns, and the tested specimen. The acoustic energy is supplied by a high frequency power supply. An amplitude-measuring <levice and a means of dissipating the heat generated by the deformation process are also necessary. A frequency display, cycle counter and temperature­measuring equipment are used to monitor the test. Ultrasonic (high-frequency) fatigue testing is based on a resonant test approach. The wave is generated by a relatively small periodic stimulus at the same frequency as the natural frequency of the test specimen (8]. To simulate cyclic deformation in the shoulder bead area of the tyre the varying level of dynamic strain amplitude of ultrasonic was applied. The samples with steel cord material shaped In cylinder were deformed with straín amplitude cr in range 2 - 6 MPa a the samples with bead wire shaped in block were deformed with strain amplitude cr in range 6 - 9 MPa. The fatigue limit of high operation frequency for testing of samples was a veÍy Jong fatigue lives (> I 09 cycles). The loud static strain limit of experimental composites was I 0.9 MPa during the whole test tirne. In comparison with threshold tensile deformation applied during the laboratory pull - out T-test (40 MPa) was the load approximately 4-times less. Piemalactric c:onvute:r Hom w.,,. [xporimim.L soecimelll Lood eauinme11t G G S.mor for clofomlillion .moliludo naútcm,-Ultru:,ni: nnez:ator Cluoranoter Fig. 2: Resonance system with load equipment and development of deformation amplitude 231 

Quantification of adhesion between rubber and steel cord by ultrasonic deformation

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Quantification of adhesion between rubber and steel cord by ultrasonic deformation

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