Research And Implementation Of Thermal Fatigue Test System For Metallic Materials

Thermal fatigue test is an important means to study the thermal fatigue properties of materials.However,the existing thermal fatigue test equipment has certain limitations in practical use.Taking the two typical thermal fatigue test devices as examples:the heating and cooling speed of the environmental chamber test device is slow,resulting in low efficiency of the thermal fatigue test;although the electromagnetic induction test device has high heating efficiency,it cannot guarantee the uniform heating of special-shaped specimens(such as bending specimens).These problems not only affect the effectiveness of the thermal fatigue test,but also hinder the progress of thermal fatigue research to a certain extent.To solve these problems,this project has developed an efficient,low-cost,and especially suitable for special-shaped specimens metal material thermal fatigue test system,and tested and evaluated the performance of the system through specific experiments.Firstly,the following designs were made for the hardware.Direct electric heating was used instead of traditional induction heating,which maintained high efficiency while improving the temperature uniformity of the specimen.Cooling was achieved through air cooling,where compressed air was blown out by a wind knife,effectively amplifying gas flow and greatly enhancing the cooling efficiency of the specimen.Thermocouples were used to measure the specimen temperature,force sensors were used to measure the load,and a vision module was introduced to measure the complex deformation of the specimen.Multiple operating parameters were monitored in real time during system operation to ensure safe and reliable thermal fatigue testing.A multifunctional data acquisition card was used for signal acquisition and output,enabling the system to perform precise acquisition of multiple sensor signals and output control signals.Secondly,in the design and development of the control software,a complete software framework based on the "producer-consumer" model was constructed.The control software was divided and designed into functional modules,and Lab VIEW was used to develop each module.In the design of the temperature control module,a fuzzy control-based state machine was proposed for temperature control.In actual applications,it showed fast response to errors and simple parameter adjustment.Additionally,this project conducted research and design on visual measurement software combined with specific applications.It solved the problem of measuring the angle of bent specimens in thermal fatigue tests and achieved dynamic angle measurement by tracking the ROI through constructing an expansion model.Finally,multiple experiments were conducted using bending specimens to test various performance indicators of the system.The experimental results indicated that the maximum heating temperature of the system can reach 1200℃,and the temperature uniformity of the specimen during operation meets the requirements for most metallic materials in thermal fatigue testing.At the lowest temperature of 100℃,the heating and cooling rates of the system can both reach 15℃/s.During the insulation stage,the relative temperature control accuracy can reach ±0.5%,and the angle measurement accuracy can reach ±0.02°,meeting the requirements for practical use.Additionally,the system exhibited excellent stability during the experiments,ensuring long-term safe and reliable thermal fatigue testing,and demonstrating strong practical engineering value.