温度、应力加速试验对螺旋压缩弹簧应力松弛行为的影响

发布时间：2018-04-21 08:57

本文选题：60Si2Mn弹簧 + 应力松弛　；参考：《天津大学》2012年硕士论文

【摘要】：应力松弛是弹簧在服役过程中的主要失效方式之一。它使机器的工作效率,仪器仪表的精度、灵敏度,稳定性和可靠性受到极大影响。因此系统研究弹簧应力松弛问题,探讨松弛机理,并对室温使用的弹簧的服役寿命做出准确预测具有现实和理论意义。本文研究了60Si2Mn淬火回火态弹簧和正火态弹簧在静载荷下的应力松弛性能。分别考察了温度、载荷和试验时间对弹簧应力松弛行为的影响。利用动态弹簧应力松弛试验机对不同温度和不同载荷下弹簧应力松弛数据进行了采集,并基于温度加速应力松弛理论对两种组织弹簧的室温服役寿命进行了预测。借助显微硬度仪、宏观残余应力仪、X射线衍射仪、金相显微镜、扫描电子显微镜和透射电子显微镜研究了不同温度、不同载荷、不同试验时间对淬火回火态和正火态两种组织弹簧的显微硬度、宏观残余应力、点阵畸变以及微观组织的影响,并分析了弹簧应力松弛的微观机理。试验结果表明,弹簧应力松弛曲线分为两个阶段,第一阶段松弛速率快持续时间短;第二阶段松弛速率慢,持续时间长。淬火回火态弹簧和正火态弹簧室温服役10年的负荷损失率预测值分别为0.8%和2.97%,表明淬火回火组织具有较好的抗松弛性能。弹簧显微硬度在低温应力松弛过程中变化不大。宏观残余应力松弛是弹簧应力松弛的原因之一。引起点阵畸变的微应力在整个松弛过程中都不起决定性作用,而是组织内的宏观内应力起作用。微观结构观察和分析表明,淬火回火态弹簧松弛过程中由于位错的运动会有条带组织生成;正火态弹簧在松弛过程中片层结构会有细化、宽化、扭转、碎化等结构变化。随着松弛时间的延长条带结构和片层结构都会消融,组织向均匀化发展。
[Abstract]:Stress relaxation is one of the main failure modes of spring in service. It greatly affects the efficiency of the machine, the precision, sensitivity, stability and reliability of the instrument. Therefore, it is of practical and theoretical significance to study the stress relaxation problem of spring, to discuss the relaxation mechanism, and to predict the service life of spring used at room temperature. In this paper, the stress relaxation properties of 60Si2Mn quenched tempered spring and normalizing spring under static load are studied. The effects of temperature, load and test time on the stress relaxation behavior of spring were investigated. The data of spring stress relaxation under different temperatures and loads were collected by using dynamic spring stress relaxation test machine, and the service life of two tissue springs at room temperature was predicted based on the theory of temperature accelerated stress relaxation. By means of microhardness instrument, macroscopical residual stress analyzer, X-ray diffractometer, metallographic microscope, scanning electron microscope and transmission electron microscope, different temperatures and loads have been studied. The effects of different test time on microhardness, macroscopic residual stress, lattice distortion and microstructure of quenching tempered and normalizing spring are discussed. The microcosmic mechanism of spring stress relaxation is analyzed. The experimental results show that the spring stress relaxation curve can be divided into two stages: the first stage is a short fast relaxation rate and the second stage is a slow relaxation rate with a long duration. The predicted load loss rates of quenched and tempered springs for 10 years at room temperature are 0.8% and 2.97, respectively, indicating that quenched and tempered structures have good relaxation resistance. The microhardness of spring does not change much during low temperature stress relaxation. Macroscopic residual stress relaxation is one of the reasons of spring stress relaxation. The microstress which causes lattice distortion does not play a decisive role in the whole relaxation process, but the macroscopic internal stress in the tissue plays an important role. The microstructure observation and analysis show that during the relaxation process of quenched and tempered spring there will be striped structure due to the movement of dislocation, and the lamellar structure of normalizing spring will change in the process of relaxation, such as thinning, broadening, torsion, fragmentation and so on. With the extension of relaxation time, both the strip structure and lamellar structure will melt, and the tissue will develop homogeneously.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TH135

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