Research On Detecting Techniques And Equipment Of Dynamic Parameters Of Stranded Wires Helical Springs

Stranded wires helical springs, also called multi-wire helical springs, are normally made up of several steel wires that are tied up to form a strand with the same direction of spiral, the strand is then twisted to form a helical spring. Compared with single-wire helical springs, stranded wires helical springs exhibit predominant characters such as better stiffness, higher strength, longer fatigue life and more effective shock absorption. Base on that, stranded wires helical spring are often used in the shock absorber of the automobile instruments, the armament blast-off system and aeroplane engine etc. Furthermore, they also have important and potential value in civil use.The displacement and velocity of all spring coils along the axis, when stranded wires helical springs are impacted with a low speed, can be seen as a linear distribution, with both speed and displacement of the active end reaching the highest point while the counterparts of the fixed end being zero. Accordingly, the speed and displacement of any spring coil can be approximately calculated through the rule of linear distribution. Moreover, the precision is pretty high. Yet when stranded-wire helical springs are impacted with a high speed,the movement of every spring coil will become very complicated owing to various factors, such as the mass, inertia and resonance of springs, the internal friction of steel wires, also the relative slipping during different steel wires of stranded-wire helical springs. In this case, it is impossible to calculate precisely the speed and displacement of any spring coil just by use of current measure equipments of springs. Additionally, in order to measure its lifespan of stranded wires helical springs under impact load, live fire can only be adopted, unquestionably which is very expensive and inefficient. Therefore, a fatigue test with low velocity is uesd instead of impact fatigue test so as to calculate its approximate lifespan.To resolve these problems, a set of motion models of various helical springs under vibrational condition are proposed and they can be used to measure the relationships between displacement and time, velocity and time, acceleration and time for every spring coil. Furthermore, we developed the corresponding test equipment that can be used in motion test and impacting fatigue test.This article seeks to design the testing equipment, the study are as follows:Firstly, a set of motion models of various helical springs under vibrational condition are proposed and they can be used to measure the relationships between displacement and time, velocity and time, acceleration and time for every spring coil. This is obviously useful when we try to explore springs'deformation rule.Secondly, according to the motion model mentioned above, we developed corresponding test equipment that mainly includes the design of mechanical structure, data acquisition module and data analysis module, which provides us a good experiment platform in the research of stranded wires helical springs.Thirdly, based on the device we developed, some improvements have been done. Specifically, the PLC is adopted in order to realize the function of continuous impact, which is essential when we do impacting fatigue experiment.Lastly, by use of these devices and take stranded wires helical springs as the research objective, the deformation rule of these springs has been analyzed. In addition, we also analysed the influence of impacting fatigue on stiffness of stranded wires helical springs.