Design And Experimental Research Of Mechanical Properties Test System For Polymer Materials At Microscale

With the development of society,people are more likely to suffer from cardiovascular disease while vascular stent technology is currently the effective method to treat cardiovascular disease.The traditional metal stent remains in human body after the blood vessel has been remodeled,which can result many complications.Therefore,the polymer degradable stent is now the effective way to replace metal stent.It is widely accepted that mechanical properties of material are the key basis of the stent design.Unlike metal,polymers are susceptible to temperature and deformation rates in terms of the mechanical properties.Considering the fact that stent is applied to human blood vessel which owns small size and works in a high temperature environment,there are rarely material testing equipments capable of testing the mechanical properties of the above-mentioned micro-sized materials in different shapes and different temperatures.In this paper,a test system for polymer materials at microscale is designed and the system is used to conduct experimental research on the stent polymer materials,which finally achieved the following results:(1)The overall design of the test system is proposed based on the test object.According to the working state and the manufacturing process of the stent,the target object to be tested is determined.The test sample is analyzed in detail based on the target object and the overall test plan has been established.For different types of samples,different clamping schemes and detection methods are proposed in view of the overall scheme.(2)Accomplish the construction of mechanical properties test system for polymer materials.The hardware part of the test system is established by using servo motor,PLC,force sensor,industrial camera and combined with designed parts and temperature control device.Based on the data acquisition and processing module,image acquisition and processing module and communication module of Labview,the test and control part of the system is built.(3)The test system's functionality is verified.Firstly,it is proved theoretically that the horizontal installation of the system's mechanical sensor has no influence on the test and then it is verified by the experiment.Secondly,the standard samples are used to test on the test system and commercial equipment separately.By referring to relevant literature data and the data acquired through commercial equipment,it is finally concluded that the function of the designed test system meets the requirement and the test data is ture and reliable.(4)The elastic modulus,yield strength,breaking strength and elongation at break of polylactic acid materials with different shapes under different temperatures and strain rates are tested through designed system.The test results are as follows:The polylactic acid shows different mechanical properties at different temperatures.As the temperature increases,the yield strength of polylactic acid has decreased while the elongation increased.When the strain rate beyonds a certain value,the elastic modulus and the yield strength of the material are increased while the elongation at break is reduced by increasing strain rate.