| With properties like high specific strength and specific modulus, high heat resistance and good erosion resistance, and also mechanical properties of inorganic material as well as processable properties of organic material, Aramid Fiber is the ideal carcass material of rubber based composites of high performance. However, because of the steric effect of benzene ring and lack of active group in its molecular structure and its high crystallinity, the application of Aramid Fiber in ruber composites has been restricted. While, the application of Aramid Fiber as the carcass material in conveyer belt has been valued in the material conveying industry in recent years. Aramid rubber conveyer belt has the advantages of Aramid Fiber, and has superiority under extreme operating conditions of long disitance, large freight volume, high temperature or with flame retardance requirement, but problems like low tenacity retention rate of the splice, poor operational stability and short service time have limited the application and polularization of Aramid rubber conveyer belt. Study of the influencing factors of the strength of the splice and analysis on the mechanical property of the splice provide theoretical support and practical reference for enhancing the strength of the splice of Aramid rubber conveyer belt and making perfect designing schemes.(1) Finite element model is built to model finger shape splice of Aramid rubber conveyer belt. By comparing hyperelastomer continuum mechanics theory constitutive model, this paper selected the Mooney-Rivlin model under 2 parameters to define the mechanical behavior of cover rubber and skim rubber. Based on simplifying assumption, the fabric is regarded as elastic material, and the elasticity modulus E, shear elasticity G and Poisson's ratio ?, in each orientation of the fiber are used to define the mechanical behavior of aramid fabric and EP polyester fabric. The static tensile strength of the splice of Aramid rubber conveyer belt calculated by querying the reaction force at reference note A is 592kN/m, with a random error of 3.1% compared with 574kN/m, the result get from experimental measurement. The reasons for the random error are analysed. The distribution of Mises stess and nominal strain of each material can be visually observed on the field variables cloud picture, which provides reasonable predictions on the falure of splice.(2) This dissertation analysed possible influencing factors of finger shape splice tensile strength of aramid rubber converyer belt and proposed an idea to improve the tensile strength by changing the structural parameters. Under the condition that the length remains unchanged, the influence of different width of finger root on the finger shape tensile strength was compared. By comparing the data of the experiment and based on the calculation by means of finite element method, it turned out that finger root with smaller width can obviousely improve the tensile strength. The shear stress mainly lies in the gap of the fingers. By reducing the width, the shear stress in the gap of the fingers can be decentralized. The influence of skim rubber of different thickness on the tensile strength was compared. The total thickness of the upper and lower skim rubber should be in general accordance with the thickness of the fabric carcass. As such, the volune of the rubber that will be absorbed is secured and meanwhile, good adhesive strength is also secured. Too thick skim rubber will increase the additional shearing torque in the skim rubber and will have an impact on the tensile strength. In addition, practice shows that too thick skim rubber will affect the liquidity of the rubber under co-vulcanization and directly affect the splice tensile strength. The influence of fabric reinforcement layer in different orientation on splice tensile strength. The splice strength of fabric reinforcement layer in warp orientation have advantages over that in other orientations, which reaches 574kN/m, and the retention of the splice strength is 60% of the strength of the sample of conveyer belt. The fabric reinforcement layer in warp orientation can obviously slow down the speed of shear deformation of the cover plastic. The falure of the sample of the splice happened in the rubber at both ends of the reinforcement layer. Reduction of the stress concentration at that part is the key point for improving the splice tensile strength. Gaps between the fingers have disadvantage on improvement of the splice tensile strength. The skim rubber in the gaps first get transformed during stretching. The reserved gaps are also sources of incurring defects such as producing bubbles.(3) Dupont(?) 830D aramid industrial yarn processed with pre-dipping solution was characterized. Trying to analyse that there are chemical components such as methylene, ester group and C-O structures in Dupont pre-dipping solution. By comparing the adhesion property before and after aging, it is concluded that the procession with Dupont pre-dipping solution have an obvious effect on the improvement of the adhesion property and the anti-aging property of aramid fiber/rubber composites. Samples of rubber converyer belt for common use and of heat-resistant were produced by adopting domestic aramid products. The adhesion property, the anti-aging property and the adhesion property under high temperature of the samples were tested by comparing with foreign aramid products of same level. It turned out that the properties of domestic aramid products meet the standard for use of conveyer belt and there are differences only in aspects of surface activation and the process method of pre-dipping solution. By combining experiments and finite element analysis and based on domestic and foreign industrial standards, this paper designed a splice handling methods of DPP3150 flame-retarded aramid conveying belt for PingYao Coal Chemical Group Co.Ltd. The retention of the splice strength has reached or exceeded 80% of the requirement of that project. The projetc is checked and accepted successfully. |
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