Abstract: Hot-wet tensile strength is one of the important indexes to characterize the mechanical properties of molding sand. In the study of traditional hot-wet tensile strength equipment, most designers design the tester to only be used for laboratory or on the spot, so make it impossible to test both in laboratory and the production site. At the same time, most of the traditional testers cannot observe the dynamic change of the hot-wet tensile strength curve in real time, but can only obtain one strength value, which makes the tester unable to accurately control the whole testing process. Therefore, it is significant to design a new type of mobile hot-wet tensile strength tester, which can not only meet the needs of laboratory testing, but also meet the needs of production site testing, and can observe the dynamic changes of hot-wet tensile strength curve in real time. The tester is designed on the basis of GB/T 2684—2009 Test Methods for Foundry Sands and Molding Mixtures and the theory of molding sand micro deformation. The hardware is designed by PC, PLC, high precision stepping motor, sensor and collector, and the software is designed by DELPHI programming language. The tester can stably realize the functions of real-time data collection, processing and storage in the process of testing standard samples, and draw the curves of hot-wet tensile strength and temperature with time in real time. The overall structure adopts frame type, which can greatly reduce the overall weight while ensuring the stability of the structure, and the bottom of the tester is equipped with universal wheels to facilitate the movement of the tester. Finally, the new type of self-developed mobile hot-wet tensile strength tester is compared with a brand of tester, and the standard method is used for sample preparation. The test results show that the tester has high accuracy and precision, and the operation is more convenient.

Key words: hot-wet tensile strength tester, mobile type, real-time curve, PLC