Papers by Keyword: Weld Quality

Abstract: Obtaining welded pipes with a superior toughness and plasticity of weld seam is strictly related to the properties of steel utilized in manufacturing welded pipes and firstly to its weldability. As a consequence, experimental research has been focused on obtaining steel with a lower equivalent carbon content but presenting high toughness and plasticity properties. In order to compensate for the decreased mechanical strength of the steel caused by reducing the carbon and manganese contents, in the first stage micro-alloying has been applied with niobium (0.040-0.055 % wt. Nb) to a construction steel, with a reduced content of carbon and manganese. The results of the mechanical characteristics obtained on hot rolled coil were good, but in the cold rolling process of pipes, the toughness characteristics have decreased excessively due to severe cold working characteristics of this steel. The second stage of experimental research has utilized microalloying with titanium (0.015-0.025 % wt. Ti), simultaneously with reducing the niobium content to a maximum level of 0.030% wt. Nb. Also, in order to reduce the cold brittleness of the steel, the maximum phosphorus content has been limited to 0.010 % wt. It was obtained excellent results with respect to the material toughness (evaluated by the impact test on KV specimen), the toughness value going up from 30-40 Joules to 150-180 Joules, while maintaining the excellent results previously obtained for steel weldability as well as the overall mechanical characteristics.

Abstract: Resistance spot welding is used extensively in auto industry. Every commercial vehicle has 4000-5000 spot welds. The weld ability, performance, and reliability are therefore important issues in design. Tensile-shear tests are normally performed to evaluate the weld quality and acquire the mechanical strength of spot welds. However, different industry test standards often specify different dimensions for the tensile-shear specimen. In this work, we investigate the failure load and energy absorption of the spot welds made of Q235 steel using tensile-shear specimens of different dimensions. The objective is (a) to determine a specimen dimension independent geometry for failure strength, and (2) to call attention to the deficiency of some of the test standards.

Abstract: Manufacture of steel pipes micro-alloyed with Ti, V, Nb by high frequency electric resistance welding (HF-ERW) is a modern and efficient method, but requires a good knowledge and adjustment of various parameters influencing the welding process. This study aims to determine the influence of the main process parameters (electrical and mechanical) and establish correlations between them, in order to optimize the welding process. This was possible only by controlling and monitoring the welding parameters used and conducting experiments and tests on welded pipes in different conditions.

Abstract: Friction stir welding process parameters plays an important role in determining the quality of welded joint. The weld quality of the joint can be assessed in terms of properties such as lack of defects, tensile strength, hardness and desired microstructure. The objective of the friction stir welding process is to obtain a good welded joint with the desired strength and microstructure. This intended to present comprehensive review of application of tool geometry, different process setups computing techniques, design of experiment (DOE) and evolutionary algorithms used to obtain the good weld joint with desired weld quality.

Abstract: Determination of the optimal welding parameters to achieve specific weldments on a new material is usually an expensive and time consuming. To determine the welding parameters using Artificial Intelligence (AI) technologies, one must consider many factors including productivity, thermal input, defect formation, and process robustness. Determination of the welding parameters for pipeline welding is based on a skilled welders long-term experience rather than on a theoretical and analytical technique. In this paper, a smart system develops which determines welding parameters and position for each weld pass in pipeline welding based on one database and FEM model, two BP neural network models and a C-NN model. The preliminary test of the system has indicated that the system could determine the welding parameters for pipeline welding quickly, from which good weldments can be produced without experienced welding personnel. Experiments using the predicted welding parameters from the developed system proved the feasibility of interface standards and intelligent control technology to increase productivity, improve quality, and reduce the cost of system integration.

Abstract: In this study, a FE simulation model of the continuous extrusion process with double feedstocks is established. It is aimed to investigate the weld quality of AA6063 aluminium alloy profiles. The results show that with the height of preformed die increasing, the pressure-to-effective stress ratio (K) increases greatly and the welds can be improved. The maximum value of K reaches to 5.5. By observation the microstructure of the welding zone, the extrusion welding line does not extend to the product surface. No defects appeared on the surface of the extruded product. It is proved that the AA6063 product with good welding quality can be obtained by continuous extrusion with double feedstocks. These also provide the theoretical basis for expanding the application of the continuous extrusion process with double feedstocks.

Abstract: Gas metal arc welding is one of the most important arc welding processes used in manufacturing and repair. In this process selecting appropriate values for process variables is essential in order to decide upon metal transfer and subsequently control the heat input into the workpiece from which reliable predictions could be made about the metallurgical, mechanical properties and performance of the welded joints. In this paper, the welding dilution in gas metal arc welding of ST37 steel has been predicted by fuzzy logic. A five level five factor rotatable central composite design was used to collect the welding data and the weld dilution was modeled as a function of wire feed rate, welding voltage, nozzle-to-plate distance, welding speed and gas flow rate.

Abstract: Gas metal arc welding is a fusion welding process which has got wide applications in industry. In order to obtain a good quality weld, it is therefore, necessary to control the input welding parameters. In other words proper selection of input welding parameters in this process contribute to weld productivity. One of the important welding output parameters in this process is weld dilution affecting the quality and productivity of weldment. In this research paper using Taguchi method of design of experiments a mathematical model was developed using parameters such as, wire feed rate (W), welding voltage (V), nozzle-to-plate distance (N), welding speed (S) and gas flow rate (G) on weld dilution. After collecting data, signal-to-noise ratios (S/N) were calculated and used in order to obtain the optimum levels for every input parameter. Subsequently, using analysis of variance the significant coefficients for each input factor on the weld dilution were determined and validated. Finally a mathematical model based on regression analysis for predicting the weld dilution was obtained. Results show that wire feed rate (W),arc voltage (V) have increasing effect while Nozzle-to-plate distance (N) and welding speed (S) have decreasing effect on the dilution whereas gas Flow rate alone has almost no effect on dilution but its interaction with other parameters makes it quite significant in increasing the weld dilution

Abstract: The effect of electrode force on the weld quality of resistance spot welding monitored using electrode displacement was experimentally studied in this article. The electrode displacement was detected by the grating displacement sensor, and the maximal electrode displacement was obtained by the measurement system. The weld quality was evaluated by the tensile-shear strength of spot welds. Groups of spot welding experiments were performed under different electrode pressure, and the relationship of the maximal electrode displacement and tensile-shear strength in weld lobe was analyzed. The results showed that the relationship between electrode displacement and weld quality is not constant when the electrode force changed.

Abstract: The aim of this study is to develop an effective on-line ANN-based approach for quality estimation in resistance spot welding. The proposed approach examines the welding parameters and conditions known to have an influence on weld quality, and builds a quality estimation model step by step. The modeling procedure begins by establishing relationships between welding parameters (welding time, welding current, electrode force and sheet metal thickness), welding conditions represented by typical characteristics of the dynamic resistance curve and welding quality indices (nugget diameter, nugget penetration, and indentation depth), and the sensitivity of these elements to the variation of the process conditions. Using these results and various statistical tools, three estimation models are developed. The first one is based exclusively on welding parameters. The second model is based on characteristics of the dynamic resistance curve. The third estimation model combines welding parameters and characteristics of dynamic resistance curves. In order to carry out the models building procedure, an extensive number of welding experiments are required. For this purpose, Taguchi’s efficient method of experimental planning is adopted. The results demonstrate that the developed models can provide an accurate on-line estimate of the weld quality, under different welding conditions.