Papers by Keyword: Keyhole

Abstract: Friction stir spot welding as a solid state processing technique is used to join dissimilar and similar metals, composites and polymers. This study illustrates the implementation of friction stir spot welding (FSSW) on additive manufactured nylon-based composites with chopped carbon fibre reinforcements. The purpose of this study is to employ FSSW technique for joining additive manufactured carbon fibre composites. The utilization of pinless tool serves a crucial function in the formation of sound welded joints. The joining process consists of two mechanisms: the piercing and melting of the sheets and the adhesive bonding during the re-solidification. As a result of the FSSW process, the joints indicate a decent mechanical performance with a lap shear failure force (LSFF) of about 250N.

Abstract: Friction stir welding (FSW) consists formation of keyhole at the end phase of the process, which is major defect and needs to be removed. In the present investigation, keyhole of dissimilar friction stir welded Al-Mg joint was repaired by novel technique of pin less tool friction stir repairing. Two different pin less tools having different tool diameters were applied to repair keyhole. Visual inspection, macro structural analysis, microstructure features and mechanical properties are assessed in order to check the successful prevail over of keyhole defect. The results revealed that, keyhole of dissimilar friction stir weld of Al-Mg joint was effectively repaired by pin less tool friction stir repairing. Excellent material mixing was obtained in the repaired area of keyhole. Tensile strength was obtained as 159 MPa that was higher than the dissimilar Al-Mg FSW joint.

Abstract: The paper deals with the comparison of surface hardness and porosity of stainless steel 316L (1.4404) produced by additive technology (SLM) and cold rolled steel. The subject of the paper is a comparison of two sets of samples where the first set of samples was made on a Renishaw AM400 with a laser output of 200 W and 400 W. In each set of samples, were the samples without heat-treated and heat-treated by annealing. Measurement of porosity and surface hardness were performed on all samples. The surface hardness of the material was evaluated by a static test according to Brinell CSN EN 10003-1. The porosity measurement was performed by the optical method. The measured values were compared with the reference material, which was cold-rolled steel, in which both the porosity and the hardness of the surface were measured.

Abstract: The purpose of this investigation is to clarify the behavior of exit keyhole diameter during switch off (cutting arc) period in case of Plasma keyhole arc welding (PKAW). During switch off period, the keyhole and weld pool are visualized from backside via a high speed video camera (HSVC). The result showed that keyhole diameter on the backside is unstable. The keyhole size is much changed in X-axis. Firstly, it is increased and then it is decreased to a stationary value at t = 0.05 s after cutting arc. Meanwhile, the size in Y-axis is not changed approximately from t = 0.01 s after cutting arc. The results can be considered to control this process more efficiency.

Abstract: In this research work, we consider the problem of sensor selection for the system controlling full penetration mode in electron beam welding. For this, we have investigated four signals from the backside of the workpiece: electron current in root plasma, ion current in root plasma, through-thickness electron current and penetrating bremsstrahlung X-ray. After having done the research we have estimated the advisability of two signals: one for cases if requirements for control precision are high and the other for other cases.

Abstract: This essay will find a new way to prevent technical unlocking and violence through the cylinder lock through the narrow cylinder bore for the purpose of improving the performance of the theft. The miniaturization of the keyhole and cylinder locks, it makes the lock cylinder by means of the implementation does not have enough space, greatly limits the unlocking illegal activities. Meanwhile, the new lock cylinder has the advantage of mutual opening rate lower.

Abstract: An observation system is developed with three ordinary industrial CCD cameras to capture the images of the weld pool and the keyhole. Experiments are conducted to evaluate the affecting relationship between welding parameters (welding current and welding speed) and the size of weld pool and keyhole. The observation results lay foundation to understand the weld pool and the keyhole behavior in PAW process and to design the future control system.

Abstract: The simple model to estimate the depth of the keyhole during laser welding is presented. The model is based on the energy balance between the radiation absorbed by the kehole walls and the heat conducted in the horizontal direction. The calculations conducted for the solid and liquid phase give lower and upper estimate of the depth of the keyhole.

Abstract: Porosity is formed because of the keyhole collapse. The porosity formation is associated with the melt pool dynamics, the keyhole collapse and solidification processes. The objective of the paper is t to investigate porosity formation mechanisms and fluid flow in the melt pool using the volume of fluid method. The results indicate that the formation of porosity in continuous wave keyhole mode laser welding is associated to keyhole collapse, backfilling of liquid metal close the gas exit of the laser welding keyhole, surface tension of the gas/liquid interface play an important role in the backfilling downward to the keyhole right after laser beams left.Keywords: porosity; keyhole; collapse; welding; model

Abstract: The paper is focused on the study Influence of parameters of plasma welding on the properties of welded joints of duplex stainless steels in mode with deep remelting. The aim of research is determining a suitable parameters of plasma keyhole welding that will allow the good welding joint, particularly in respect of proper ratio of austenite-ferrite phase without undesirable intermetallic phases.