Study Of Fatigue Of Welding Joints Under Ultra-high-cycle Of Loading

With technical development in modern industry, in many applications, the lifetime of the mechanical components have to endure up to 109 cycles of loading without failure or at best. The concept of a fatigue limit has only been applied in conventional fatigue testing. Thus the fatigue property of metallic materials in the UHCF range tends to be an important subject in the mechanical design to ensure the long term safety of the mechanical structures.Since performing experiments of the ultra-high-cycle regime in the range of 107-1010 cycles using a conventional fatigue testing method is very time consuming and expensive, in this paper, a kind of acceleration fatigue test technique, called the ultrasonic fatigue testing, was developed and studied. Thus how apply to ultrasonic fatigue equipment in the ultra-high-cycle fatigue (UHCF) is always important subject as professionals. The ultrasonic fatigue equipment gained perfectly. It increased a lot of function, for example data transmissive equipment of USB2.0; collecting testing data by accessorial computer and tracking.Testing data was collected by 51 Single Chip Micyoco (SCM). Collection and transmission of testing data has been actualized by designing of hardware and software and manipulating interface. Filter circuit was used to filtering before collecting data. On-line testing was qualified.There are four kind of ultrasonic fatigue test samples which be designed according to calculated formula in the theory. Varying-arca column was testing.The performance of ultrasonic fatigue equipment was approved stabilization. 45 steel was designed two kinds of samples including base metal and welding joint. The mentioned above results satisfied require in ultrasonic fatigue testing which collected testing data and transmitted by USB2.0 and SCM. Testing results indicated that testing samples still generated fatigue failure. The fatigue lifetime of welding joints was lower comparatively than which of base metal.