Research On Tire Curing Characteristics And Influencing Rule

Cure is the final step in the producing process,which determining its physical performance.Because of the complicated curing reactions,distributions of the cure characteristic parameters are obviously non-uniform and time-variable.Factors influencing the process are numerous,leading to aimless design and control of vulcanization process.Therefore,modeling theories of thermal property parameters and cure kinetics were firstly investigated.Numerical model and corresponding experiment for the tire curing process were also presented.Secondly,the change regulations of tire cure characteristics were investigated.And effects of technological and material parameters on the characteristics were proposed.Finally,simulation system was developed for tire curing process.Thermal property parameters such as specific heat capacities and thermal diffusivities were tested by LFA447 Nanoflash equipment at uncured,partially cured and completely cured state.The multi-dimensional models for thermal conductivity and specific heat capacity were presented,based on the differences between common thermal property parameter models and experiment results.Furthermore,mixing rule models for rubber-cord thermal property parameters were built,which contained thermal property parameters of rubber,thermal property parameters of cord,and cord volume fraction.The models were validated using numerical analysis of real structure and equivalent structure.Cure torque verse time cures at three different temperatures were tested by curing kinetics experiments.The induction time verse temperature curves,state-of-cure verse time cures and reaction rate verse state-of-cure cures at different temperatures were inferred using least square method.Induction was described using dimensionless parameter model.The variation of state-of-cure in the heating stage was simulated by K-R model and modified K-S model respectively.The results showed that the two models could not effectively predict rubber curing kinetics.Therefore,hybrid kinetic model was proposed in a form of piecewise function,which covered common kinetic models and was appropriate for numerical simulation.The predicted results of the model agreed well with the experimental results.Multi-field coupling mathematical model,solution strategy and realization method for the tire curing process were presented.Numerical method based on CFD technology and partition method based on feasible direction technology were used to study heat convection between tire and air in the cooling stage,respectively.The results obtained by the two methods were close.However,the numerical method was more practical.Co-simulation of temperature filed and cure field from heating stage to cooling stage was realized using ABAQUS software and its subroutine UMATHT.And the simulating results agreed well with the experimental results.The change regulations of tire cure characteristic parameters were investigated.In the heating stage,temperature on the outer and inner surface of the tire increased firstly.The fastest temperature increasing area was thinner sidewall.The temperature in bead and tread area increased faster as well.The slowest temperature increasing area was shoulder.Inversed trend was found in the cooling stage.Cure reaction on the outer and inner surface of the tire terminated firstly,which contact with the plate vulcanization machine,then the sidewall was next and followed by bead and tread area.The thick shoulder was the finally area where cure reaction terminated.So the engineering vulcanization time at this location could be used as an index to evaluate the whole tire curing performance.In existing curing condition,the curing time for the heating stage could be adjusted to 2907s,which increased productivity by 6.8%.What is more,effects of technological parameters,rubber thermal properties and curing kinetics on tire cure characteristics were analyzed.And matching methods for curing medium temperature was proposed.The results showed that,the engineering vulcanization time with no bladder and bladder with half thickness decreased by 21.9%and 10.8%respectively,compared with original model.The engineering vulcanization time with initial temperature of 50? and 40? decreased by 2.7%and 1.3%respectively,compared with original model.The proposed distributing block method could be used to match steam and water temperature effectively,by building distributing block of tire cure characteristic parameters.Increasing heat conduction of the tread,decreasing specific heat capacity of the tread and activation energy of all rubber components in the shoulder area could decrease the engineering vulcanization time effectively.Curing kinetic characteristics played an important role in tire curing uniformity.Tire vulcanization simulation system was developed using Visual Basic programming language,based on common curing characteristics of radial tire.In the software,multi-field coupling model and its simulation for tire curing process was realized automatically and professionally.The software was combined with the advantages of special program and general finite element program,and researching achievements of this paper.