| Retreaded OTR tires often have exacerbated tread wear, chunking and chipping, tread delamination and even failure modes of compression-induced blowout or puncture-induced blowout during use. Current studies explore solutions to these problems mainly by adopting methods such as improving tread compound formulation and improving the retreadeding process, while there are relatively fewer studies on the comprehensive mechanical properties of retreaded OTR tires. At the time of tire retreadeding, the mechanics, temperature rise characteristics and use conditions of tires are not taken into full consideration, resulting in uneven quality and short service life of retreaded OTR tires. To this end, this paper targets at 26.5R25 steel radial retreaded OTR tires as the basic object of study, constructs a multiple-composite-layer type, mechanical model and material constitutive model of retreaded OTR tires for the purpose of improving performance, carries out finite element numerical simulation and experimental study of the mechanics and temperature rise characteristics of retreaded OTR tires, investigates the performance reinforcement and mechanism of retreaded OTR tires under common failure modes, and employs the life-cycle theory to evaluate and analyze the energy recovery effect and environmental impact of retreaded OTR tires after performance reinforcement.By using the theory of natural equilibrium profile, the paper has analyzed and designed the structural and dimensional requirements for retreaded OTR tires composed of old carcass ply, buffer layer and tread layer; by means of theoretical analysis and experimental testing, constructed the mechanical model and contact model of retreaded OTR tires under multiple-composite-layer type and composite layer structure; and from the perspective of material layers, constructed the constitutive model of each composite layer of retreaded OTR tires and described the stress-strain relationship matrix of each composite layer.On the basis of the theoretical model constructed, the paper has used Pro/E WildFire and ANSYS Workbench software to construct the multiple-composite-layer geometric model and finite element analysis model of retreaded OTR tires; and by means of pilot test and combining with Gough-Tangorra formula and Ekvall formula to obtain the material parameters for finite element analysis, analyzed the deformation characteristics and static grounding characteristics of retreaded OTR tires under free inflation, free rotation and static grounding conditions, and obtained the load-deformation, grounding pressure and contact friction, grounding contact pattern shape, grounding area and other rules of retreaded OTR tires.The paper has obtained the stress-strain and shear stress-shear strain rules of each composite layer of retreaded OTR tires, analyzed the micro-mechanical mechanism of interaction between layers; analyzed the vibration mode of retreaded OTR tires under two different conditions, namely rim constraints and ground contact constraints, and obtained the inherent frequency and vibration mode of the first 20 orders of retreaded OTR tires; and analyzed the distribution rules of steady-state temperature field of each composite layer and between layers of retreaded OTR tires at different speeds, under different tire pressures and at different ambient temperatures, and investigated the temperature rise characteristics of retreaded OTR tires.The paper has constructed a testing system for the deformation characteristics, grounding characteristics, steady-state temperature field and physical and mechanical parameters of tread rubber of retreaded OTR tires, obtained the deformation characteristics, grounding pressure, grounding contact pattern, steady-state temperature field and other distribution rules of retreaded OTR tires, and compared and analyzed them with the simulation results; and obtained the physical and mechanical performance parameters of tread rubber of retreaded OTR tires and performance-reinforced retreaded tires, and evaluated the use performance of retreaded OTR tires.The simulation and experimental results show that the radial deformation and lateral deformation of retreaded ORT tires are smaller than those new tires of the same model under the same working condition and the aging degree of old tires has greater influence on the deformation characteristics of retreaded ORT tires; the carcass ply and belt ply of the retreaded ORT tires are the main bearing layers, whose quality has direct influence on the bearing characteristics of the retreaded ORT tires; there is much greater shear force between the buffer layer and belt ply; and the heat accumulates inside the shoulder of old tires and at the shoulder of retreaded ORT tires, with much higher temperature.The paper has explored three performance reinforcement methods of tread rubber matrix formula reinforcing agents, tread reinforcement and carcass ply reinforcement, and by testing and comparative analysis, evaluated the use performance and reinforcing effect under different reinforcement methods; and combining with the compounding principle and rules, constructed the mechanics model of performance reinforcement, and investigated the mechanism of performance reinforcement of retreaded OTR tires. The research shows that the wear-resisting property of the retreaded ORT tires and the reinforcement effect of the anti-collapse performance are much more ideal when the mass fraction of the carbon black N151 is 40, the mass fraction of the carbon black N330 and white carbon black is 40 and 20 respectively, the fiber length and mass fraction of short cut carbon are 6mm and 7% respectively, and the fiber length and mass fraction of short wire are 5mm and 10%. Meanwhile, the waste radial tire wires are used to reinforce the performance of old tire body and the bearing performance, compression resistance performance and ability to prevent puncture-induced blowout get improved effectively.Based on the basic theory of life cycle, the paper has constructed the energy consumption model and environmental impact model of OTR tires and retreaded OTR tires, compared and analyzed the energy consumption and environmental impact of first retreadeding, retreadeding by the three performance reinforcement methods, second retreadeding, mechanical grinding, cryogenic grinding, burning and decomposition, burning for electricity generation and other treatment methods in the recycling phase of wasted OTR tires, calculated and obtained the energy recovery rate and carbon reduction rate of several treatment methods in the recycling phase, and verified the feasibility of the three performance reinforcement methods studied in this paper from the perspective of life cycle. The studies indicate that the retreaded ORT tires own the best energy recovery effect and carbon reduction effect, which can be used as the future development direction for reuse of waste OTR tires, the reinforced energy recovery effect of the tread reinforcement is the best and the carbon reduction effect of three reinforcement ways differ slightly.The study results of this paper can provide important theoretical reference for performance study of retreaded OTR tires, lay a theoretical foundation for improving the service life of retreaded OTR tires, and generate an enormous driving force for the use of retreaded OTR tires, boasting significant economic benefits arid social benefits. |
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