Study On Distributed Strain Test System Of Large Sling Based On Virtual Instrument

Large slings are imporment for the industrial and mining enterprises as heavy-duty machine equipment, by which facilities or products can be installed, overturned, lifted and loaded. In metallurgy, ports, aerospace, construction, transport, machinery and other industries, it has been widely used in the actual production and played a huge role. When lifting heavy objects, large sling will get heavy stress and significant distortion. Therefore, it is concerned that the sling's design is reasonable or not, performed as an adequate strength, stiffness and good stability to achieve safe production by designers and users. Strain measurement technology is an important analysis way of the mechanical structure and strength. In the paper, according to the testing actual situation of the large slings, the distributed strain test systems based on virtual instrument has been studied and designed.For the sling's large scale, strong interference, more scattered measuring points, large-scale test, etc., in order to ensure data reliable collected and transmitted and overcome the adverse effects of the long wire, test systems of distributed structure composed of the host computer, data processing modules and communication networks. Sysrem collects and manages data by network composed of RS485 bus technology. System has simple structure, strong anti-jamming ability, low-cost and it is more suitable for small and medium-sized data acquisition.Data acquisition module contained RM417, sensor (strain gauges), signal processing module (signal conversion, amplification and filtering, etc.) to achieve signal acquisition. RM417 module has high conversion rate and accuracy with RS485 communication interface to support multi-point data communications, the system can be expanded to 16 modules. Its maximum communication distance can be 1200m and 10Mb/s of maximum transmission rate.Each measured point can be connected to the nearest communication module, the wires's length from strain gauge to communication module can be shortened to improve the accuracy of the test.Host computer is responsible for data processing and display.Software based on virtual instrument developed by Labwindos/CVI.Method of modular design achieves that data automatic processing, real-time data display, automatic mapping of stress and sling strain's curve, data storage and automatic generation of test reports.Anti-jamming of software and hardware, analog and digital filtering technology improve the accuracy of the test. Software can get the auto-zero bridge and achieve non-linear compensation of single bridge, which reduces hardware's costs and workload of the test. System is friendly to user, easy to operate, easier to apply.Test results showed that the system achieves data's dispersive collection and centralized processing in large-scale testing of sling and avoids man-made reading error and calculation error. The system has high stability which improves the test's precision and efficiency. Test system can be used in large sling testing, also at work. It can also be applied to other stress-strain test, such as transportation, construction and scientific research or teaching experiments, such as stress testing. The design has good application prospects.