Research On Structural Standard Of High Density Polyethylene Ships

Domestic market demand for high density polyethylene(HDPE)ships is growing,However,due to the lack of corresponding structural rules,the work on design,construction and inspection of HDPE shipls are difficult to carry out.The domestic normative basis cannot meet the growing needs of HDPE shipbuilding companies.This paper aims to solve the above contradictions,to determine a routine structural design process and referable formula for the building of HDPE ships.Through the tensile test,taking the measures of control variable method and comparative analysis method,the strain rate correlation of yield strength about HDPE has been determined,that is,the yield strength increases with the increasing of strain rate,but the unit increasing is not higher than 0.05 MPa/(mm/min).Besides,it has been found that the yield strength of HDPE decreases with the increasing of temperature,the unit reduction is not less than 0.262MPa/K,and the maximum can reach 0.487 MPa/K.Based on the above research results,the value of the yield strength of marine HDPE materials is plotted.Combined with the ship construction process,this paper has investigated the influence of welded joints on the yield strength of HDPE.It has been determined that the single-sided welding reduces the yield strength of the material by about 0.15,while the double-sided welding only decreases by about 0.10.Based on the reflection of the domestic HDPE shipbuilding companies and the actual foreign HDPE ship types,this paper has compared the related domestic structural rules of the small high-speed ship.Also,this paper has extracted a common structural design process.Combining with the application characteristics of HDPE,this paper has adjust and made it suitable for the structural design of HDPE ships.Based on the structural design formula of steel and aluminum alloy small-sized high-speed ship,this paper has analyzed the relevant factors which would influence the formula calculation,ans found the core factors which would influence the structure design formulas of HDPE ships,namely the plate and aggregate coefficient.In addition,the paper has proposed a simplified research idea of using stiffened plates to simulate the hull structure,based on it,reasonably derive the plate and aggregate coefficients for HDPE.Then the reliability of the above content has been verified by the finite element strength check of the actual ship.Because the development of HDPE ships in China is late,there is currently no relevant targeted research.Therefore,ths paper is the first domestic systematic study on the structural design rules of HDPE ship,It makes more sense for the work of design,construction and inspection of HDPE ships and similar marine equipments.