Heat Input Of Welding Process Research Articles

Experimental evaluation of fatigue strength for small diameter socket welded joints under vibration loading condition

To investigate how the fabrication and repair of socket welded joints could be used to enhance fatigue resistance under vibration condition, experimental test data of installation conditions that potentially influence fatigue strength were analyzed with the S–N curve. It was found that the decreasing fatigue strength of stainless steel socket welded joints was attributed to the effect of high heat input of welding process. The effect of welding method, slip-on gap and radial-gap conditions on fatigue strength was insignificant. The test data of repair technique application, 2 × 1 leg length and of socket weld overlay, clearly showed higher fatigue strength but there was a limitation for higher stress region because of the weld toe crack.

Fatigue design of weld part in non-combustible magnesium alloy based on fracture mechanics

Fatigue design of weld part in non-combustible magnesium alloy has been studied. Specimens for fatigue test were produced by TIG welding with different welding conditions. According to result of fatigue strength tests, all weld specimens tested in the present study were broken at the weld prat, and a weld defect was found as a fatigue fracture origin. Fatigue life was well arranged by effective stress intensity factor calculated with a size of weld defect played as a fracture origin and applied stress. Therefore, it is speculated that fatigue strength of weld part is depending on a size of weld defect and threshold stress intensity factor at the weld part. Size of weld defect and value of threshold stress intensity factor possibly changed by welding condition. Therefore, relationship between heat input during welding process and threshold stress intensity factor was studied by conducting fatigue crack growth test at the weld part. The value of threshold stress intensity factor range increased with increase in heat input of welding process. However, values for threshold stress intensity factor range almost coincided when the crack growth curves were arranged by effective stress intensity factor range. Difference in threshold stress intensity factor range due to difference in heat input of welding process was mainly induced by change in crack closure effect. It is proposed that effect of crack closure depending on mechanical property of weld part should be taken into account on fatigue design of weld part in non-combustible magnesium alloy.

Thermal Stability of Fine Grains as a Function of Process Parameters in FSW Butt Joints

Friction Stir Welding process introduces a degree of deformation in the material that is related to process parameters. They directly regulate the heat input of welding process and then the morphology and the microstructure characteristics. In the present work, an investigation was carried out on 6082T6 butt joints obtained by Friction Stir Welding process. The microstructure and mechanical characterizations were performed before and after a post-welding treatment at 535°C for 2 hours and cold deformation. The thermal stability of fine recrystallized grains in the nugget zone depends on process parameters and post-welding heat treatment and it has unusual consequences on mechanical properties. In fact abnormal grain growth, that occurs in the nugget zone, increases ductility of the joints and homogenizes the hardness profile of the whole joint.