Effect of welding sequences on residual stresses

Effects of residual S on Kirkendall void formation at Cu/Sn–3.5Ag solder joints

Numerical simulation to study the effect of tack welds and root gap on welding deformations and residual stresses of a pipe-flange joint

The weld quality comprises bead geometry and its microstructure, which influence the mechanical properties of the weld. The coarse-grained weld microstructure, higher heat-affected zone, and lower penetration together with higher reinforcement reduce the weld service life in continuous mode gas metal arc welding (GMAW). Pulsed GMAW (P-GMAW) is an alternative method providing a better way for overcoming these afore mentioned problems. It uses a higher peak current to allow one molten droplet per pulse, and a lower background current to maintain the arc stability. Current pulsing refines the grains in weld fusion zone with increasing depth of penetration due to arc oscillations. Optimum weld joint characteristics can be achieved by controlling the pulse parameters. The process is versatile and easily automated. This brief review illustrates the effect of pulse parameters on weld quality.

Effect of Pulse Parameters on Weld Quality in Pulsed Gas Metal Arc Welding: A Review

A shear mode piezoelectric energy harvester for harnessing energy from pressurized water flow is developed. It converts flow energy into electrical energy by piezoelectric conversion with oscillation of a piezoelectric film. A finite element model is developed in order to estimate the generated voltage of the piezoelectric film subjected to a distributed load. Prototypes of the energy harvester are fabricated and tested. Experimental results show that an open circuit output voltage of 72 mV pp and an instantaneous output power of 0.45 nW are generated when the excitation pressure oscillates with an amplitude of 20.8 kPa and a frequency of about 45 Hz. The solution of the generated voltage based on the finite element model agrees well with the experiments. Based on the finite element model, the effects of the piezoelectric film dimensions, the water pressure and types of piezoelectric films on the output voltage of the harvester can be investigated.

A shear mode piezoelectric energy harvester based on a pressurized water flow

The aim of this study was to investigate the effect of added nitrogen to the argon shielding gas and retained ferrite on the residual stress in austenitic stainless steel weldment by using autogenous gas tungsten arc welding. The base metal of type 316L and 310 stainless steels were used in these experiments. During welding, the thermal cycles of different locations in the weldment were recorded. The residual stresses were determined by using the hole-drilling strain-gage method of ASTM standard E837. The depth-to-width ratio was observed with an optical microscope. A thermomechanical analyzer (TMA) was used to analyze the thermal contraction during the solidification process in investigated materials. A ferrite-scope was used to measure the ferrite number for each weldment. To study the variation of ferrite content from weld metal to heat-affected zone, an electron probe X-ray microanalyzer (EPMA) was employed to analyze the nitrogen content within the weld metal. The experimental results show that the cross-sectional area of weld metal increased with increased nitrogen content in the shielding gas. The 4% nitrogen addition has a minimum depth-to-width ratio value. The low heat input condition has higher retained ferrite content than the high heat input condition when the level of nitrogen in the shielding gas does not exceed 2%. During solidification, the thermal contraction can be moderated by the expansion of δ -ferrite. Therefore, the dual phase structure that δ -ferrite retains within the austenite matrix has lower residual stress in comparison with the single austenite phase matrix.

Effect of nitrogen content and retained ferrite on the residual stress in austenitic stainless steel weldments

Effect of preheating on the residual stress in type 304 stainless steel weldment

Effect of residual stress on thermal fatigue in a type 420 martensitic stainless steel weldment

https://ir.nctu.edu.tw:443/bitstream/11536/2102/1/A1995QJ33500085.pdf

Y.C. Lin

Papers

Effect of nitrogen content and retained ferrite on the residual stress in austenitic stainless steel weldments

Effect of preheating on the residual stress in type 304 stainless steel weldment

Effect of residual stress on thermal fatigue in a type 420 martensitic stainless steel weldment

A new technique for reducing the residual stress induced by welding in type 304 stainless steel

The numerical analysis of strain behavior at the solder joint and interface in a flip chip package