Development Of A New Mobile Type Hot-wet Tensile Strength Tester

Hot-wet tensile strength is one of the important indexes to characterize the mechanical properties of moulding sand.In the past research on hot-wet tensile strength equipment,most designers positioned the instrument in the laboratory testing,but ignored the field testing.At the same time,the traditional tester cannot observe the dynamic change of hot and wet tensile strength curve of molding sand in real time and only one strength value can be obtained,which makes the tester unable to accurately control the whole testing process.In view of the above problems,a new mobile type hot-wet tensile strength tester is designed in this paper,which can not only meet the needs of laboratory testing,but also adapt to the detection of moulding sand when there are many interference sources in the production site.This tester is designed on the basis of micro-deformation theory of moulding sand and based on GB/T 2684-2009 Test Method for Sand and Mixture for Foundry.High precision stepper motor is controlled by computer and PLC-224 XP to realize the uniform rise and fall of micro-slip platform,and then the uniform loading of standard sample is realized.It is equipped with tension sensor and temperature sensor to collect the signals of tension and temperature in the whole process.The final data are fed back to the computer for calculation and processing,and the curve is drawn in real time.The overall structure of the tester adopts frame design.The mechanical part is mainly composed of upper beam,tension sensor,universal joint,upper stretching frame,heating block,lower stretching frame,angle iron,micro slip platform,equipment frame,high precision stepping motor,middle partition board,etc.The hardware system is mainly based on Siemens PLC-224 XP and Yanhua USB-4711 A.It also includes tension sensor,temperature sensor,regulated DC power supply,relay and computer.Using object-oriented DELPHI as programming language,the test interface of this tester is designed to establish a good human-computer interaction interface.The functions of real-time data acquisition,processing and preservation in the process of standard sample testing are realized stably,and the real-time curve of hot-wet tensile strength-time-temperature can be drawn.Finally,a new mobile type hot-wet tensile strength tester developed independently was used to test the samples prepared by standard method.The test results show that the error values of hot-wet tensile strength measured by this tester under different environments are relatively small.The tester has strong stability,accuracy and anti-interference ability,and is more convenient to operate.