The direct connection of column splices using partial joint penetration Groove welds with a penetration percentage between 40% - 60% of the thickness of the column section was common until the Northridge and Kobe earthquakes. With the poor performance of beam-to-column Welding connections after the Northridge earthquake and column splice Welding connections after the Kobe earthquake, new design details and executive instructions were added to the regulations and the use of partial joint penetration (PJP) Welding in moment frame structures was prohibited and designers were required to use complete joint penetration (CJP) Welding (AISC 341-10). With experimental and numerical studies conducted on PJP Welding with a higher penetration percentage in I-shaped sections, the possibility of using PJP welds with a penetration percentage of 85% was confirmed in the regulations (AISC 341-16). All previous studies were conducted on the behavior of PJP Groove welds in I-shaped sections. in this study, a 3D finite element numerical model was simulated in Abaqus software in order to investigate the behavior of the column splice and the failure and spread of damage in the Heat Affected Zone (HAZ). By ensuring the proper performance of the finite element model, 33 box-shaped column splices have been modeled, and the effects of parameters such as penetration weld percentage, column thickness and cross-sectional dimensions on the column splice behavior has been evaluated.

In this paper, the effect of high frequency induction Welding parameters on the weld quality of welded pipes is studied. For this purpose, process parameters such as current, frequency and edge shape of the weld connection and their effects on the heat distribution are investigated. Experimental investigation is performed by using tensile test, metallography, and micro hardness. This reveals three regions with different grading and various thermo-mechanical treatments. The results show that the grain size decreases about 27 percents as the edge shape is improved. By conducting thermo-magnetic analysis, different current intensities and frequencies are evaluated in the creation of appropriate temperature distribution. The results show that with increasing the current and frequency, the heat-affected zone is expanded and other areas become smaller. The maximum increase of the average temperature in the weld edge, was about 42 percents from 1250 to 1500 amperes per unit increase of the frequency. Microhardness test is used to detect micro-structural phases of the weld zone.By comparing the results of the metallography and micro-hardness tests, more uniform weld width was observed with modified edge of the in welded samples. The results represent 18 percents of decrease in the weld width of the modified samples in comparison with samples without edge preparation.

Beam-column connection is one of the most important parts of steel ductile flexural frames, as the performance of frame is depending on connection’ s flexibility. The rigid steel connections with cover plate are one of the most common connections in Iran. Due to the importance of seismic resistant design, it is necessary to investigate their seismic performance. In this experimental research, three steel connection specimens with 1/2 scale with introduction of new T-shape plate were built based on Iran steel code to evaluate their seismic performance and the specimens were subjected to cyclic loading. The results indicated that specimen designed based on Iran steel code cannot satisfy all of rigid connection criteria, and also, the strength was increased up to 10% and ductility was decreased up to 18% by adding the plates. Plastic hinges were transmitted to flange of beams, and the collapse mechanism of connections were changed due to deleting Groove Welding, strength and ductility were decreased respectively.

In multi-pass Groove Welding, residual stress distribution, value and associated distortion are dependent on several factors, including the Welding process-dependent parameters, mechanical properties of materials and fixtures. In present study, temperature distribution of three Welding processes with different geometric designs are registered by the K type thermocouple. Each of the samples contains the same stainless steel plate A316 thickness that was welded based on Welding procedure specification with gas tungsten arc Welding method, with Groove corner joints single bevel without gap and bevel face, single and double bevel with gap and bevel face. Created residual stress on a sample was initially measured by nondestructive ultrasonic transverse waves method. After cutting the vertical part (plate without Groove), for hole drilling device installation purposes, the aforementioned stress was measured by the semi-destructive hole drilling method. While for two other geometrical designs only ultrasonic method has been used to prevent parts from being destroyed. All three aformentioned designs were modeled in Simufact. Welding finite element code (FE) and results were compared with experimental temperature and residual stress measurements. The comparison shows that experimental measurements and numerical values match with each other well, highlighting a reasonable validation of finite element models results. Current research results show that changing the geometry of the weld configuration has a significant effect on changes in the distribution and maximum value of transvers residual stress, but negligible influence on maximum longitudinal residual stress.

Surface layer in many engineering applications is strengthened by ceramic grains where the main parts have higher structure toughness than the original material. This paper presents the effect of four process parameters that have been taken into consideration using Taguchi technique based on L9 orthogonal array. These parameters are; 1) transverse speed, 2) type of nano-powders, 3) rotational speed, and 4) Groove’ s depth friction stir Welding T-joints aluminum alloy 6061-T6. This work combines Welding T-joint sections and creating MMNCs in Welding region simultaneously. The predicted optimum parameters and their percentage of contribution are estimated, utilizing the analysis of variance and signal to noise ratio techniques, depending on tensile test in skin and stringers direction, and hardness test of the joint. Optical microscope and scanning electron microscope (SEM) analysis are used to verify the microstructure and dispersion of nano-powders in Welding joint. The best ultimate tensile stress (UTSskin) equal to (177MPa) for the skin welded part was obtained at the optimal conditions of 1550rpm rotational speed, 15mm/min transverse speed, Al2O3 type of powder and 1mm Groove’ s depth. SEM micrographic for metal matrix nanocomposite of all nine experiments revealed that the nano-particles are irregularly dispersed in nugget zone due to one pass. The rotational speeds of 960rpm, the transverse speed of 15mm/min, type of powder TiO2, and Groove’ s depth of 1. 5mm, give the greatest hardness value of 80HV in nugget zone. The analysis of variance shows that the Groove’ s depth is the most significant parameter in this investigation.

Welded tubular joints are widely used in various industry structures for high efficiency subjected to pressure, bending and twisting. Welded structures are the main parts of structures, buildings, bridges, gas pipes, pressure vessels and power transmission equipment in the ship building, construction, oil, gas, petrochemical industries and power plants. A sample of pipe-welded joints is a X-tubular joint that has been investigated in this study. The main objective of the present work is to investigate the heat transfer and residual stress caused by the three-stage Welding process in Xtubular joint made of St52 using Simufact Welding software. The Welding process involves three Welding steps using arc Welding. The finite element model contains the thermal and mechanical properties of base metal and Welding metal as a function of temperature. Also, advanced modeling tools such as mesh adaptation during the process and meshing compatible with the Welding site, the birth and death technique of the element and the source of heat transfer have been used. Welding simulation showed that significant residual stresses were created in the joint after Welding. Comparison of the results shows that the numerical results and empirical measurements are in good agreement with each other and the existing model can provide a good prediction of temperature distribution and stress control in this Welding process.

Preventing brittle fracture in the connection welds of the steel members is one of the most important issues in the performance of steel structures. Bitter experiences of Northridge earthquake in the case of “ demand critical” welds such as complete-joint-penetration (CJP) Groove welds in the connections of steel moment frames forced researchers to conclude that for preventing decrease in ductility and preventing brittle fracture of welds, it should be that impact toughness of welds must be provided at the determined temperature. Seismic Requirements of AISC and following of it the 10 th topic of Iranian national building Requirements for the mentioned Welding recommends Charpy-v-notch toughness at the determined Test temperature. In this research, to ensure impact toughness of preformed welds in the common conditions of Iran, the Charpy Test in the specimens of multiple thicknesses and common electrodes has been done with Shielded Metal Arc Welding (SMAW) and Submerged Arc Welding (SAW) and the conclusions of them compared with the 10 th topic requirements. It has been shown that impact toughness of Groove weld in SMAW process with E6013 electrode and Groove weld in SAW process doesn’ t matched with requirements of present Codes, but for other electrodes there was no contradiction.

Stability of rigid rotor supported on hybrid journal bearing with twin axial Groove has been investigated using stiffness and damping coefficients of the bearings. In this paper the stability analysis of twin axial Groove bearing is determined in different fluid flow regime. Non linear journal centre trajectories are drawn for small amplitude oscillations of the journal centre about its steady state position. It was observed that turbulence decreases 10 to 12 percent the stability margin of twin Grooved journal bearings.