پيش بيني شكست مخازن CNG فولادي در پديده با رهيافت مكانيك آسيب

چكيده انگليسي :

Pridiction of All Steel Cylinder Fracture in Impact by Damage Mechanic Approach Mohammad Yazdani Ariatape m yazdaniariatape@me iut ac ir Date of Submission 2011 09 13 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Mohammad Mashayekhi mashayekhi@cc iut ac irAdvisor Saeed Ziaei Rad szrad @cc iut ac irAbstract From economical view natural gas is frugal fuel by low cost and with abundant resources on the otherhand this combustion pollution are lower than other common fossil fuels such as gasoline and diesel Amajor issue of natural gas fuel using in cars is the storing problem Compressed natural gas CNG cylinders are used for storage of fuel in high pressure in cars with CNG These cylinders is divided into fourcategories according to the manufacturer s material that including all metal metal liner hoop wrapped metal liner fully wrapped and all composite All steel cylinders with 91 7 percent usage are the mostcommon type of cylinders and history of these cylinders goes back to 1974 There are three known methodsto produce this type of cylinders so that their difference is in the raw material Safety is one of the importantissues in design and manufacturing of such cylinders All metal cylinders are using more well knowntechnology with respect to the other types of cylinders and therefore have more capability to safeperformance According to the importance of safety and decrease concern of gaslight car s passengers because of incident due to CNG cylinders impact with barriers especially in car accidents it is necessary toinvestigate cylinder impact conditions before use High cost and risk of empirical tests make the use ofnumerical methods inevitable In this thesis damage mechanics approach is used to investigate the effect of crash and damage causedby impact in CNG under pressure steel cylinder The CSA standard in CNG cylinders is used as a damagedetection criterion and cylinders ability to reuse Simulation of cylinder failures caused by car accident anddrop is done by using Johnson Cook damage model which is one of the efficient models in impactproblems Accomplished simulations are carried out in different impact directions and effect of cylinderinternal pressure collision velocity and fall height are analyzed Also failures due to collision for varioussituations are discussed These investigations for different cases including crash and drop tests show that themaximum damage created in case of vertical impact and by changing direction from vertical to horizontalresultant damage will be decreased Also by eliminating failed elements and comparing damage depthcaused by collision with CSA standard it is observed that in most cases of vertical accident and drop tests cylinders have been damaged and lose its ability to use while in horizontal impact cases cylinder is intactor can be reused after repairing The results show that in collision process the cylinder s rear wall and thefront hemisphere of cylinder have more damaged and are the critical areas in the horizontal and verticalcollisions respectively For a specific impact direction in lower cylinder internal pressure higher collisionvelocity and altitude of fall damage will be more The resulted diagrams indicate that damaged area of thecylinders predominately are under compression and endure large plastic deformation The low differencebetween the results by various meshes shows that this solution does not depend on the mesh size Therefore this damage model is insensitive to meshing in the various impact cases Keywords All steel CNG cylinder Damage Mechanics fracture Impact Jahnson Cook model

يزداني آرياتپه، محمد

پيش بيني شكست مخازن CNG فولادي در پديده با رهيافت مكانيك آسيب

مدل جانسون و كوك , برخورد