Study On Microscopic Evolution Mechanism Of Flexural Fatigue Damage Of Nature Rubber And Optimal Control

At present,most studies on the fatigue failure performance of rubber materials mainly focus on the tensile fatigue mode,and there are relatively few studies on the flex fatigue mode,while the flex fatigue mode is common in the mechanical deformation of rubber products.For example,Shoulder,rubber soles,plastic deformation of the larger part of the tape.At the same time,in-depth study of rubber material in the process of flex fatigue mechanism and macroscopic properties of the relationship between the flex fatigue structural design and flexion fatigue life prediction model is extremely important.Therefore,the study of flex fatigue of rubber materials has important practical and theoretical value.In this paper,natural rubber as the experimental research object,through the use of different experimental analytical instruments,such as: scanning electron microscope(SEM),dynamic mechanical analysis(DMA),infrared spectroscopy equipment(FT-IR),rubber processing analyzer(RPA200O),Wide-angle X-ray diffraction(XRD),etc.The micro-structures of natural rubber before and after flexing fatigue were analyzed.The flex fatigue failure of natural rubber was analyzed from the microscopic point of view and the chemical reaction level,and the possible mechanism of flex failure process was proposed.At the same time,the experiment also briefly discussed the factors that may affect the flex fatigue of natural rubber.Such as: curing crosslinking network,antioxidant,filling system,etc.The mechanism of the flex fatigue of vulcanize was also discussed.In this study,we tried to establish the evolution mechanism of the flex fatigue failure of rubber from the perspective of the micro-structure and the molecular structure of the rubber by analyzing the fracturemorphology of flex fatigue specimens of natural rubber and combining with the change of molecular structure before and after flex fatigue Model,provides a basic guide to the design of the flex resistance of rubber products.The results show that the flex fatigue failure process of vulcanized rubber samples of natural rubber is the process of mechanical external force initiation,oxide reaction and chemical reaction,and the growth of oxide reaction is mainly the process of destructive growth.There are three obvious stages in the process of flex fatigue.In the first stage,mechanical damage is the main cause and the destruction rate is slower.The second stage of chemical and oxidation damage destroy the destruction rate control,the rate increased sharply.In the third stage,the chemical and oxidation destruction decreased,and the destruction rate decreased.SEM analysis showed that vulcanized natural rubber flex fatigue fracture tip showed obvious ligament network structure and hole structure.Flexion fatigue is a process of uninterrupted,alternating formation and destruction of the ligament network structure and hole structure until the rubber material fails.The flex fatigue resistance of vulcanize is influenced by the cross-linked network density of the vulcanize,the type of cross-linkages and the cross-link bond energy.The results of the samples showed that the highly fatigue-resistant cross-linked network structure corresponded to low cross-link density,high poly-sulfide content and high cross-link energy.SEM analysis showed that when the amount of sulfur is small,the flex fatigue fracture zone has more coarse ligament,and when the amount of sulfur is larger,the flex fatigue tip morphology is relatively flat,showing more fine ligament structure.The carbon-carbon bond is rigid and the bond energy is high,and the flex fatigue fracture section is rough and lame.With the increase of the density of carbon black filled rubber network,the flex fatigue resistance of rubber tends to increase first and then decrease.The uniformity of dispersion of carbon black particles flex fatigue resistance performance can not be ignored.Too high carbon-black filled networks cause increased network defects within the rubber system,potentially resulting in reduced flex fatigue failure of the vulcanize.Antioxidant can rapidly capture the free radicals generated by flexing fatigue of vulcanized rubber,and terminate the activity of free radicals.The possibility of free radical-induced rupture of ligament structure is reduced,and the effect of flexing and flexion prevention of rubber is obvious.With the increase of the dosage of antioxidant,the fine ligaments of flex fatigue section of the vulcanize collapsed and gathered afterfracturing,forming the coarse ligaments with the adjacent rubber ligaments,and the non-uniformity of ligament networks was obvious.The experiment also investigated the flex fatigue resistance of natural rubber by zinc oxide.It was found that the flex fatigue cracking of natural rubber increased with the increase of flexing times.When the amount of zinc oxide exceeds 5 parts,the fatigue crack length of vulcanize changes little with the amount of zinc oxide under the same degree of flex.The increase of the amount of zinc oxide will gather,and the SEM result proves that the agglomeration of zinc oxide can easily lead to the generation of rubber fatigue fracture.Fatigue cracking of materials caused by the use of rubber products under cyclic stress conditions often determines the fatigue life of these products.Under the action of repeated stress,the rubber macro-molecule chains form micro-destructions and generate stress relaxation around them.After a certain period of time,the rubber macro-molecules chains produce micro-destructive expansion starting from the center of destruction.In order to ensure the safety and reliability of rubber products,it is of great significance to study the dynamic fatigue properties of rubber materials.