Numerical Simulation On Fracture Splitting Of Main Bearing Cap Of Engine Crankcase Bearing Bracket

Fracture splitting technology is a new technique which occurred in 1990's, this technology is first used in auto engine connecting rod. It simplified structural design of bolt hole and whole process technology. The technology has lots of advantages, few working process, small equipment investment, low manufacture cost, good product quality ,high assembly precision, strong carrying capacity and so on.Lots of scholars are studying fracture splitting technology, technique feature, material of the technique, setting of start crack point, processing mode of fracture groove, control of fracture quality, selection of fracture equipment, decision of technology parameter and other correlated questions. Simultaneous, the research field is dilated. Crankshaft bearing caps, Crank shaft flange, Cam disk, Strap, Bearing for printing machine are all produced by fracture splitting technology. The processing of fracture splitting automotive engine crankshaft bearing caps has the same principle of fracture splitting connecting rod. First, designed groove at the propriety place, form centralized stress, Then throw load vertical to predefined rupture face to guide fracture. When stress suffice brittle fracture condition, it will achieve rule fracture at groove without set yielding, then chipless split come ture. The processing of fracture splitting automotive engine crankshaft bearing caps appears all the more complicated than connecting rod, therefore it's very significance to study the processing of fracture splitting automotive engine crankshaft bearing caps. The thesis mostly has finished hereinafter several aspect works:(1)Study on technological parameters of a kind of crankshaft bearing caps groove material called HT150.The geometry figure is an important factor which controlled fracture quality, it can change the fracture stress of model. Therefore, changing reasonable geometry is a pivotal step for fracture splitting processing. The thesis predigest the engine crankshaft bearing bracket and simulation the influence of groove's depth, crack tip opening angle, radius of curvature. Then draw a conclusion that the auto engine crankcase produced by HT150 can adopt groove figure parameter:2α=60,h = 0.4mm,r = 0.1mm.(2)Study on technological parameters of a kind of crankshaft bearing caps groove material called QT500-7.Different material has different notch sensitivity, the parameters which control groove figure has different influence on fracture quality. The auto engine crankcase produced by QT500-7 can adopt groove figure parameter:2α=60,h = 0.7mm,r = 0.1mm.(3)The load speed infection on crank qualityThe fracture toughness of material is sensitive on temperature and load speed .Improving load speed or reducing temperature can make material crank in brittleness and reduce fracture toughness. Lots of study indicate that dynamic fracture toughness is under static fracture toughness obviously. The thesis in the base of characteristic auto engine crankcase bearing bracket fracture and the empirical value of connecting rod fracture choose load speed at 5mm/s~100mm/s as auto engine crankcase bearing bracket fracture speed to simulation and analyse. The thesis draw the curve of load speed influence on stress and strain and draw a conclusion that the JETTA car's engine crankcase bearing bracket fracture speed can choose 6.4mm/s which can achieve good fracture quality .