Digital Image Correlation-based Characterisation Of Weighted Wheel Roll Dynamics

The load wheels are the main power transmission and load-bearing component of a tracked vehicle and play a role in shock mitigation,vibration and noise reduction and the transmission of the vehicle’s power.The roll dynamics of the load wheels have an important influence on the high mobility characteristics of their tracked vehicles for complex driving situations such as mud,snow,ice and slippery conditions.Therefore,it is important to study the roll dynamics of load-bearing wheels for the smoothness,driving comfort and dynamics of tracked vehicles.At present,most load wheel constructions consist of a load hub and a thickness of tread rubber material,with the tread rubber being the only part in contact with the track plate.Thus,the roll dynamics of the load bearing wheel is closely related to the roll dynamics of the rubber material.The study of the dynamics of rubber and load-bearing wheel rolls is complicated by the fact that rubber materials exhibit non-linear and complex mechanical properties when in use.Based on this,firstly,a model characterization study of the mechanical properties of the rubber material of the load tire tread was carried out through theoretical analysis,and a fine finite element coupled model of the load wheel structure considering the mechanical properties of the rubber material and the rolling contact relationship was proposed;Secondly,by means of experimental research,a study of the full-field rolling dynamics of tread rubber materials was carried out,revealing the mechanism of rolling deformation of rubber on loadbearing tires,and solving the key rolling dynamics properties of tread rubber materials;Finally,the finite element model of the load wheel structure is validated using single point and full domain test data,and the changes in the load wheel roll dynamics under complex operating conditions are predicted.The main research elements of the thesis are as follows:1.A fine structural coupling model for load wheels that takes into account the nonlinear mechanical properties of the tread rubber material and the rolling contact is proposed.First,the types of hyperelastic and viscoelastic models and the scope of their use,respectively,are described;Secondly,based on the rigid treadband model,a fine-grained model of the load wheel structure consisting of two parts,the rubber material superelastic viscoelastic coupling model and the contact model,was proposed,and the selection scheme of the tread rubber material model and the rolling contact model was developed;Finally,the parameter identification of the coupled model was completed through experiments to provide model support for the prediction of the rolling dynamics of the complex working conditions of the load wheel.2.Developed a full-domain non-contact load-bearing tire tread rubber material rolling dynamics test device to carry out research on the rolling full-domain mechanical properties of load-bearing wheel rubber materials.Firstly,a series of scattered images of the deformation of the tread rubber material during rolling were obtained by means of a test rig;Secondly,by improving the digital image correlation method,the strain rate,stress and trajectory variation patterns of the marked points of the rubber material of the load-bearing tire tread,as well as the distribution patterns of strain and velocity-acceleration images in the whole domain,are solved;Finally,the effects of drying,thin water film,rotational speed,load and carbon black composition on the rolling variation mechanism of load bearing tyre tread rubber materials are revealed,providing massive data support for solving the key rolling dynamics of load bearing tyre tread rubber materials.3.A method for solving the critical rolling dynamics of rubber materials for loadbearing tyre treads is proposed.Firstly,based on the time-domain brush model,a method for representing the dynamic/static rolling friction coefficients of tread rubber materials is proposed,and the friction coefficients of load wheel table rubber under rolling conditions are solved,revealing the mechanism of the rolling friction coefficients with the working conditions,rotational speed,load and carbon black composition.Secondly,based on the Fourier series model,a method is proposed to characterize the rolling non-linear mechanical properties of rubber materials with load-bearing tyre treads,which is used to solve the rolling energy loss and rolling resistance coefficient,and reveal the mechanism of the rolling resistance coefficient in relation to the rolling conditions and contact road surface;Finally,based on the least squares method,the inverse method of the hyperelastic model parameters of the rubber material of the load bearing tyre tread and the inverse method of the dynamic viscoelastic modulus parameters based on the sine series model are proposed,revealing the variation law of the hyperelastic model parameters and the dynamic viscoelastic modulus.4.The finite element model validation of the load wheel structure and the prediction of the roll dynamics of the load wheel under complex working conditions were completed.Firstly,the feasibility,validity and accuracy of the fine model of the load wheel structure,for example,are verified by means of experimental data obtained at different speeds/loads for single point/all-domain strains;Secondly,the model predicts the strain rate distribution characteristics and the longitudinal force and stress-strain variation patterns within the contact marks of the rolling load wheel mark point/full domain under medium/high speed and medium/high load conditions to further reveal the load wheel roll dynamics under the composite ultimate operating conditions.