Research On Fracture Splitting Processing Technology And Equipment Of Engine Crankcase Bearing Block

Fracture splitting (FS) is a bran-new technology with the development of automobile industry recent years, which is a grand renovation to the traditional processing technic. Since always, the precise process and assemble of combine face is a difficult problem needed to be resolved for section parts. It is the birth of FS technology that make it possible to precise locate the combine face of section parts. It has many advantages such as fewer procedures and inexpensive equipment investment, good-quality products, lower costs, etc. Therefore, researchers around the world pay a lot attention to it, which has become an important symbol to engine manufacture level of the country. Recent years, with the mature of con-rod FS technology and equipments, FS technology has been applied to the manufacture field of Engine Crankcase Bearing Block (ECBB). Under the foundation of former study on engine con-rod FS technology, Roll Forging Institute of Jilin University has made extensive research on FS Processing Technology and Equipment of ECBB, combining the structure and material characteristic of ECBB, also has made a great progress, which definitely has an important influence to enhance our country's engine manufacture level.This study is supported by a National nature science fund project (No.50375066) named cracking dynamic behavior and FS Processing Technology of section parts and a important science and technology developing project of Jilin province named FS Processing Technology and equipment for ECBB. State patents of FS machine for ECBB(patent No.: 200410010822.4) and laser cutting FS notch machine for ECBB(patent No.: 200710055511.3) were gained in years of 2005 and 2008.The key FS technology of ECBB contains fracture capability of engine material, optimization parameter of starting notch, rational loading speed, automatic assembling bolts with fix torque technology, laser cutting starting notch technology, determine of back pressure and structure design, etc. A lot of theoretical and experimental research has been achieved in this paper, and above mentioned contents have been studied, which has provided theoretic basis for the establishment of FS processing technic parameters and designing FS processing machine of ECBB. The innovational work and achievement are described as follows.1. Study on cracking capability and force of vermicular graphite cast ironFS principle was studied, FS processing belongs to typeⅠfracture. While the object is applying normal stress perpendicular to fracture plane, low stress fracture would occur, and the working stress during FS process is much less than the yield strength of material, therefore plastic deformation is slim. Standard sample mechanical experiment has been carried out on material tester CSS-88300 towards vermicular graphite cast iron RuT380. Base on above theoretical research, software MARC was applied to achieve numerical analysis for FS process of ECBB with material of RuT380, 20 node block same-parameter cell ecdysis constructed oddly cell for simulating oddity of crack tip, curve between fracture force and J integral was gained, basis on the critical J integral of material RuT380, the threshold value of fracture force was determined. Meanwhile FS experiment has been carried out, the errors between simulation value and test value, are 5.6% based on FS experiment. This method is suitable to determine the fracture force for section parts with different structure and materials while FS process. Reliable dates were provided for designing the FS equipment and determining the technic parameters, which established stable theory foundation.2. Optimize geometry parameter of notchOrthogonal experiment method was employed to analyze the effects of geometry parameters of starting notch on separation force. Variance analysis results show that notch depth influences separation force most and curvature radius takes the second place, opening angel influences least. The parameters of starting notch such as notch depth, opening angle and curvature radius, that influent separation force and fracture quality, were analyzed towards ECBB with the material of RuT380. The curves and analytic formulas between notch deep, opening angle, curvature radius and separation force were gained. Taking processing technic into consideration, while the FS process of Jetta ECBB with the material of RuT380, for starting notch machined by broaching, opening angle ranges from 450 to 600, notch depth ranges from 0.5mm to 0.6mm, curvature radius ranges from 0.15mm to 0.2mm are suggested, which can not only prolong the serve life of broach, but also satisfy the requirement of FS processing technic and subsequent finishing machining. For starting notch processed by laser cutting, the rational opening angle is 2α=200.3. Influence of loading speed on fracture force and FS qualityABAQUS/Explicit was applied to study the effects of loading speed on FS processing quality of ECBB, based on the FS characteristic of ECBB and the previous research, this paper used different loading speed range from 0mm/s~70mm/s to carry out dynamic simulation for FS process of ECBB, data of stress and deformation at different loading speed was obtained and validated through test, it is shown that 6.4mm/s is optimum loading speed for FS of Jetta car ECBB with the material of HT150, and better FS effect was gained.4. Design on technology and equipment of laser cutting the FS notchThe laser processing technic of FS notch for ECBB has great merits compared with other methods, and laser notching machine has great meaning for the FS processing of ECBB. Based on laser cutting theory and structure characteristic of ECBB, factors influence the laser cutting were analyzed, and laser cutting FS notch technic procedure was determined. The first domestic automatic laser notching machine for ECBB with fully independent intellectual property was developed including mechanical system, hydraulic system and computer program control system.5. FS processing machine of ECBBBased on structure of ECBB, according to general engine and gantry engine, design on processing technic has been established, and key FS technology has been studied. Special broach was used for machining FS notch, which was in front of FS mechanism. Design ideas of backpressure equipment for ECBB FS processing have been briefly descried, and the backpressure equipment is adaptive for FS processing technic of different types of ECBB. The design principle of FS block and pull key were determined, which could finish FS process for one step towards 4 cylinders engine crankshaft bearing block. The wedge shaped mechanism was designed in this paper towards Jetta car engine with 4 cylinders and 5 crankshaft bearing blocks. According to 6 or above cylinders engine, FS unit needs to be added, which could finish FS process for two steps. Design on automatic assembling bolts system has been achieved, and the pre-tightening force range and fixed torque spanners type were determined. The first domestic automatic FS processing machine for ECBB is being developed including mechanical system, hydraulic system and computer program control system now, this machine is in installation and debugging stages. Research on FS processing principle, FS characteristic of regular material for engine crankcase and FS technic parameters have been carried through, the first domestic automatic laser notching machine for ECBB with fully independent intellectual property and the first domestic automatic FS processing machine for ECBB have been developed. There are some unexhausted works for further researchers: (a). because of big structure and complicated shape of engine crankcase, the positioning of engine crankcase on each work station during the transmission process would be a difficulty. (b). The wedge shaped mechanism of FS machine is so long, no matter which accomplish FS process for one step (towards 4 cylinders engine) or accomplish FS process for two steps (towards 6 or above cylinders engine), that the requirement for strength and precision of FS execution unit are high, and the processing technic of that would be a subject for further study.The FS technology of ECBB is a new processing technic, which has great economic benefits, social effect and application prospect in our country. Research in this paper has important significance for application of FS technology of ECBB and technology renovation of engine industry in China.