Development Of In-situ Testing Instrument And Experimental Research Of Mechanical Property Close To Service Condition

With the rapid development of industrial technology,material usually works enduring different service conditions of multi loads stress state.Therefore,the testing method for complex loading condition is needed urgently.The material mechanics performance parameters,which is obtain through the mechanical properties test via simulating the stress state and the surrounding physical environment condition of material,will be widely used in advanced preparation processing,mechanical design,electronic information and communication,aerospace and other fields as important as theoretical basis.These data have important scientific significance,and also have a positive impact to the whole country’s social and economic benefits.The working environment of materials in practical use is complicated in the process of serving inevitably because of the variety of external mechanical load(such as tensile,torsional and bending loads).Materials enduring different external loads will express different mechanical properties.At the same time,the specimen is also affected by thermal field,electric field,magnetic field coupling.Physical field coupling effect would induce more material mechanical properties changes and lead to the change of mechanical behavior.So,in the practical engineering application under complex conditions,carrying out the test of material mechanics performance is an important method of quality assurance.However,present commercial testers just realize the integration of different loads simply.They cannot accomplish the combined application of multi loads.In addition,there is no multi physical fields applications as well.So,this kind of tester cannot simulate the real stress state and strain state,and then cannot obtain the accurate experimental data with the multi loads and physical fields applied.The main research point of this paper is the development of an in-situ testing instrument with multi loads and multi physical fields coupling mode.In this paper,focusing on the service performance test for materials in the field of major national demand and international development trends,combining the scientific research status of mechanical properties and testing techniques,the design of instrument for complex service performance and multi physical is put forward,which realizes the tensile-bending-torsional combined loading state and thermal-electric-magnetic field coupled application.The design analysis,the testing analysis,the planning of the trajectory,the theoretical analysis and tests of Cu-Zn-Al have been done by the numbers.The main research work of this paper could be summarized as follows:(1)Based on the theory of parallel loading unit and spacious trajectory design,a novel in-situ testing method for mechanical property is proposed including tension/compression,torsion and cantilever bending loads application.This method accomplishes the multi loads application and control simultaneously and overcomes the influence because of the tandem load application with high accuracy,which enriches the in-situ testing methods.Take the wind driven generator as an example,the stress state analyses of tension-torsion,tension-cantilever bending,torsion-cantilever bending and tension-torsion-cantilever bending have been done.The spacious trajectories of spiral line and cantilever bending are planed in specimen motion space.(2)According to the multi physical field with large amplitude,multi waveform and non-contact application,the in-situ test coupled thermal,electrical and magnetic field is achieved,which establishes the multi physical environments in service condition.The large scale,high accuracy and rapid response measurement is also accomplished.The design of multi physical fields based on needs for mechanical compact structure overcomes the space interference problem.Finally,the multi physical fields can be applied on specimen with high accuracy and provide different waveform applications.(3)A novel in-situ observation method combined DICM with microscope in order to observe the mechanical behavior and surface damage is proposed.Combined with the cylindrical-coordinate positioning method,multithreading and accurate control method,the accurate results of in-situ observation are obtained.The non-contact three-dimensional strain measurement is done,which reduces the cumbersome theoretical modification works because of the contact indirect measurement.This observation method in cylindrical-coordinate system can observation the different surface morphologies of the specimen at one time.(4)On the basis of works above,an in-situ testing instrument for combined loading states with multi physical fields coupled has been developed.Two theories are utilized to analyze the stress state due to the tensile load,torsional load and cantilever bening load.Therefore,the theorical law of mechanical property is obtained.The in-situ tests with combined loads and multi physical applied,which focuses on Cu-Zn-Al alloy,are carried out.And the experimental law of material mechanical property variation is obtained.The mutual verification between the theory and the experimental result is well convincing.