Study On Wear Failure Mechanism Under Multi-cycle Impact And Systemic Test Of Automotive Engine Chain

As automobile demand and its maintain volume are growing rapidly in China, the automotive aftermarket development are sustained and rapid, so the demand for automotive engine and parts is increasing. There are not a competitive national brand vehicles with good quality in the international market over years, while domestic auto-related production plant and engine parts production plants are mostly foreign enterprises, for later beginning of automotive industry in China. Now in the automotive parts industry, the core technologies and products supporting market is a foreign master, and it is not uncommon for being controlled. Therefore, it is an important strategic significance to study automotive parts and accessory systems design and manufacturing technology with Chinese intellectual property rights, and it will also enhance the capability of independent innovation in the field of China.At present, more and more timing chain, oil pump chain and balance shaft chain are widely used at new automotive engines. As high-speed performance of domestic automotive chains is much lower than automotive supply requirements, many automotive manufacture plants are using imported automotive chains. Therefore, it is a very important research work to study the localization of high- speed automotive chain design and manufacturing technology, and it will provide practical technical support for the domestic automotive engine design.This study is funded and supported by the project of"High strength automotive chain"(01C26213300872) that is National Technology Creating Foundation of China for Medium and Small Scientific Enterprise. Some of its research achievements have been successfully applied to automotive engine chain production of two automotive chain enterprises in Zhejiang and Qingdao Province, and that it also created significant economic and social benefits.1.The systematic test study on wear and failure of automotive chainBy the experiment research on road running test of timing bushing chains for automotive engine, the 06CT's wear mechanism and the worn surface of pins and bushings were analyzed. It is pointed out that under the condition of pressure spray oil lubrication, for the wear of the timing bushing chains, fatigue wear is dominating, and grain wear occurs synchronously. It is expounded that wear heat causing displacement stagger density's descend is the main reason that the surface of pins and bushings is soften circularly. At the same time, the test result shows that with the increasing of road test mileage, because of the fretting wear picking up, the combined firm degree of pins and outer link plate bore, bushings and inner link plate bore is declined gradually.Based on the experiments of engine assembly running, the wear mechanism of 06B roller chain was studied, the wear curves in different test condition were draw respectively. The wear surface morphology and roller material microstructure of the pin and bush was analyzed, and the plastic deformation and the cycle characteristics of the main parts wear surface of automotive chain was discussed. The fretting wear between matching parts and its reason were analyzed by pressure out force test of combined firm degree. The results show that the main wear mechanism of the bush surface was fatigue flaw and flake and that of the pin surface was plough ditch and adhesive wear.After 3000 hours high-speed test, plate and roller had rare large plastic deformation, roller wear surface had cycle hardening, and the matching surface had serious fretting wear. The pressure out force of pin - outer plate and bush– inner plate was decline largely, resulting chain almost fatigue.Through application of friction tests, the pressure and friction of 3 kinds (1 kind of rubber material and 2 kinds of nylon material) of wear-resistant surface material of guidance and tension were measured, and the relationship curve, under the condition of the absence of lubrication and oil dropping lubrication, between the friction coefficient and the pressure was drew.The conclusion is that the friction coefficient of rubber material is decreasing but the friction coefficients of 2 kinds of nylon material are increasing with increasing pressure, at room temperature without lubrication, and the friction coefficient of one kind of nylon material is the lowest. At room temperature with oil-dropping lubrication, the friction coefficients of 3 kinds of material are decreasing with increasing pressure, and the friction coefficients of 2 kinds of nylon material are no obvious difference, but the friction coefficient of rubber material is higher than nylon when the pressure is high.2.Theoretical and experimental study on noise of automotive bush chainThe systematic noise test of bush chain has been studied in high speed running state based on the theoretical noise study and considered the running characteristic of the practical application. It came to the following conclusions through test results and data analysis.The noise of 06CT bush chain is increasing and its frequency components is also changing with the changing speed. Test results confirmed the law how the sag of chain affect the noise. The measured noise of 06CT bush chain is changing with the changing sag, and the noise will increase if the sag is very big or very small, but the noise can only reach the minimum when the sag at a reasonable value.According to the noise test data, analysis results and running characteristic of chain transmission, it concluded the main noise mechanism of high-speed automotive bush chain. The impact between bush and sprocket tooth can cause noise, and also the inner plate and sprocket tooth, inner plate and outer plate, bush and pin. Noise can be aroused by polygon effect of the changing speed of chain and sprocket. Cyclical vibration of chain can cause cyclical force, and its stimulation can generate steady vibration and noise, so the noise is steady vibration noise. As well as the stimulation of transmission mechanism can also cause noise.3.Performance enhancements of automotive chainEffective means of performance enhancements, how to improve the resistance of fatigue, wear and multi-cycle impact, were brought forward based on the main wear mechanism of automotive chain, failure mode of multi-cycle impact fatigue and noise mechanism.The material with resistance of fatigue and wear should be selected firstly, and it will have great prospect to apply surface material of new nanotechnology to the components of chain with the development of nanotechnology.Material heat treatment of whole components of chain is absolutely necessary mean of performance enhancement, and the heat treatment process of chain components was enriched by the chemical surface heat treatment, laser surface quencher, surface ion implantation and laser surface cladding coating. Surface hardening treatment means of chain components, such as shot peening, rolling and laser impact technology, can make plastic deformation of the components surface, so it can enhance strength, hardness and improve the surface properties of metallic materials.The improvements of bush, roller and assembly structure can reduce the stress concentration of assembly and high-speed running, and it can enhance the lubrication and cooling function, as well as reduce the wear and noise of chain by effectively reducing the meshing impact in the process of transmission.The optimization of chain manufacturing and assembly process such as cold extrusion of plate hole, bush orientation assembly and the pre-pull process of chain ensures that high level of precision, strength and resistance of high-speed automotive chain which satisfies the demand of fatigue intensity and fatigue life.Especially, the application of auto-reconditioning technology for worn metals in chain transmission can resolve many problems that traditional enhancement means can't overcome. Auto-reconditioning technology for worn metals is great significance for the strategic objective of energy conservation and environment protection for it can realize real-time dynamic process of repairing the wear chain components and effectively reduce maintenance frequency and maintenance cost through the application of auto-reconditioning material in chain transmission. It will generate huge economic and social benefits in automotive chain industry of China with application and spread of auto-reconditioning technology for worn metals in lubrication of automotive chain transmission.