Experimental Modal Analysis On Crankcase Cover Of Magnesium Alloy

Oil consumption reduction and performance enhancement have become the development trend of road vehicles, especially of motorcycles. Due to their nature of high-speed motion and rotation, weight reduction is the most efficient way to reduce the oil consumption, to improve the accelerating and braking performance, enhance the riding comfort of a road vehicle. Naturally, the use of light weight materials on the vehicles and motorcycles is the most straight-forward way to achieve the goal. So the material substitution is the research topics which the most researchers focused on.In comparison with most widely used aluminum alloys, magnesium alloys are the lightest commercialized metallic material for structural applications. Magnesium alloys possess the attractive properties desired by motorbikes, such as low density, low cost, higher specific strength, good casting properties, out-standing damping capability. Magnesium alloys are able to reduce mass of the component, to absorb vibration, to damp noise emission, to reduce oil consumption, to enhance acceleration and braking performance and the resultant riding comfort.However, the Magnesium alloys can not be directly used on the commercial components because Magnesium alloys possess material properties considerably differing from those materials, such as steel or aluminum alloys, to which the component is designed for. To ensure the performance and safety, the service condition of the component has to be analyzed and the structure of the Magnesium components have to redesigned to in accordance with the materials properties of Magnesium allow. In order to research the dynamic performance of the crankcase box after the magnesium AZ91D is substitution by the aluminum A380,Finite element modal calculation and experiment modal analysis about the crankcase box of engine LC158FMI was done. Some principle and method of the structural optimization design about the magnesium alloy component are discussed in this paper.To understand the dynamic behavior of crankcase cover after its original aluminum alloy material is replaced by magnesium alloy, experimental modal analysis of crankcase covers respectively using magnesium alloy material as well as aluminum alloy material was done by means of the hammering method. Research shows that similarity on modal parameters of the crankcase covers with the different materials is depended on inherent relationship between the attribute parameters of the two kind materials. However, compared with the counterpart, the magnesium alloy crankcase cover is a little lower in Stiffness, its curve of the Frequency Response Function is somehow little above the counterpart. Therefore it is necessary for the magnesium alloy crankcase cover to optimize its structure and exert the good performance in shock absorption of magnesium alloy material. In general, components of the two kind materials with the same structure shared the similar modal parameters, so it is favor for replacement between the two kind materials in practical engineering.