Study On The Weaken Process And Damage Of Soft Seamless Attached Air-bag Car Dashboard

To effectively reduce casualties in car crashes, more and more high-end cars areequipped with a co-pilot airbag. Soft seamlessly attached airbag car dashboards are moreand more widely used, because of its safety, beauty and comfort. In order to airbag expandsuccessfully to protect passenger and avoid dashboards pieces flying out to hurt passenger,need to optimize the weakening process and develop reasonable process parameters. Toaccurately study on the damage of soft seamlessly attached airbag car dashboard, requireto obtain accurate material model, which includes getting the bottom of the plasticmechanism, the damage mechanism, the rheological curve; knowing the weakeningprocess parameters affect on the specimen damage performance; obtaining weakeningdashboard actual damage discipline.In this paper, the mechanical parameters and stress-strain curve obtained byexperiments. The experimental results show that the dashboard commonly used materialPP its plastic mechanism is crazing yield, the damage mechanism id crazing plasticdamage, stress-strain curves show obvious viscoelastic and viscoplastic. I usedelastic viscoplastic constitutive with viscoplastic damage to describe the complexconstitutive behavior of PP and developed the material subroutine. Analysis standardspecimen tensile test call the above material subroutines, simulation results satisfied agreewith the experimental results, the material model is able to describe the material behaviorin this paper.To study the weakening process affect on the specimen damage, analysis the stressdistribution of specimens with a series of holes from the fracture mechanics point of view,and also using finite element analysis weakened specimens. Comparative analyticalsolution of fracture mechanics and finite element numerical solution, finite elementanalysis can reflect the impact of weakening holes on stress distribution of the specimen.Through experimental and simulation study the damage of weakening specimen withdifferent weakening holes parameters and specimen with V-groove. Experiment andsimulation results show that the weakening process cause the elongation of specimen at break decreases sharply, the proportion of damage strength decrease as the ratio of thesection area decrease, the error less5%. The reason cause the above phenomenon was:The weakening micro-structure cause stress concentration the area vicinity the structure,so those area occur plastic deformation an damage in advance, but materials has a greatelongation at break, leading plastic zone extended to the entire cross-section at thespecimen break.To explore the weakening dashboard damage discipline, experiment and simulationstudy the actual damage of different weakening processes dashboard simplified models,weakening processes include weakening holes and V-groove process. Results show that:weakening holes process due to the inadequate weakening, simplified model fracture fromthe constraints; V-groove weakening process fracture from the center of the dashboard;computer simulation and experimental results are in good agreement, the finite elementmethod used in this paper can be used as one of the means of practical dashboard design.