Effect Of Electrode Force Research Articles

Empirical Modelling of a Prototype Resistance Spot Welding Machine

Resistance spot welding (RSW) has been extensively used in the automotive and aerospace industries over the years. The weld quality of spot welds is affected by the welding parameters like electrode force, weld time, electrode current and workpiece size/shape parameters like workpiece thickness. This study focuses on the effect of electrode force, weld time and workpiece thickness on the weld quality of mild steel samples where the aim is to correlate the weld strength to welding parameters of a portable RSW machine installed at the Nigerian Liquefied Natural Gas (NLNG) laboratory of the Department of Mechanical Engineering, University of Nigeria, Nsukka. Lap shear weld samples are tested for strength, and the results are used to develop an empirical model. The developed model has a coefficient of determination of 0.6365 and a correlation coefficient of 0.7978. Hypothesis testing at 5% significance level discovered that the most significant predictor is the cross interaction of the workpiece thickness and electrode force with p-value of 0.02367 and that the model is significant with a p-value = 0.0453. The model is validated by further welding operations and tensile shear tests which gave a percentage error not exceeding 12.92% but was as low as 6.35%.

Criterion for predicting expulsion in resistance spot welding of steel sheets

Resistance spot welding (RSW) is frequently accompanied by expulsion, an undesirable event taking place in manufacturing processes, including car body production. Many variables are involved in RSW, all of which can affect expulsion. This investigation aimed at developing an analytical model for predicting expulsion in RSW. Accordingly, based on force and moment balances, a criterion was established. It was proposed that expulsion took place when the molten metal ejected as a result of the pressure inside nugget. The model presented here considered that the pressure inside the nugget was mainly due to melting transformation and liquid thermal expansion. Hence, the model took into account the effects of nugget diameter, electrode force, base material yield stress, sheet thickness, and joint fit-up to predict the occurrence of expulsion. To assess the model, a number of experiments were done, where the effects of welding current, electrode force, sheet thickness, and galvanization coating of the steel were studied. Regarding the effects of electrode force and welding current, the prediction made by the analytical model was consistent with the results obtained from the experiments. However, it was observed that expulsion in the galvanized steel sheets occurred at larger nugget diameters. The macroscopic examination of the welded samples showed that, with galvanization the ability for a better electrode fit-up was increased, and according to the model this could result in thereby increasing the critical nugget size.

Liquid Metal Embrittlement of Resistance Spot Welded 1180 TRIP Steel: Effect of Electrode Force on Cracking Behavior

Liquid metal embrittlement (LME) caused cracking of Galvanized transformation induced plasticity steels was investigated during resistance spot welding (RSW). Effect of electrode force (3–5 kN) for a weld time of 400, and 800 ms on crack resistance of TRIP steel was examined in relation to LME phenomenon. The microstructural characteristics of spot weld joints and LME cracking tendency were investigated using dye penetration tests, optical microscopy, scanning electron microscopy together with energy dispersive X-ray spectroscopy. It was found that as the electrode force increases, the crack size decreases due to a fast increase in crack tip temperature which rises further with more holding time up to 800 ms in high temperature zone. Least amount of crack size was observed at 5 kN electrode force and 400 ms of welding time. Finally, the experimental results have also been simulated by finite element modeling (FEM) to find suitable mechanism of crack formation, and a combination of 4 kN and 400 ms was suggested for the crack free and less thermal deformation in the spot welded TRIP steel.

Prediction of Spot Welding Parameters for Dissimilar Weld Joints

Development of manufacturing systems are needed to invent new kind of methodology for joining process in current research and development. Spot welding technologies are widely applied in non-conventional joining process. In this investigation predicted the mechanical properties like tensile strength and Hardness. The hardness evaluated in different regions of the spot welded Stainless steel sheet and Mild steel sheet joints such as welded zone, heat affected zone and parent material subjected to different Welding Parameters. The Experimental procedures are developed by factorial design and the regression model developed from the experimental results through Response surface methodology. The variable parameters are Electrode force, Weld Current and the Weld time. The measurable parameters are Tensile strength and hardness. The optimization process is carried out by Response surface methodology and the optimized parameters are defined the quality of the welded steel joints. The optimized welded parameters are expressed the effective joining and improve the quality of the welded member. stainless steel .The phase transformation which occur during the weld thermal cycle were analyzed which shows that fusion zone exhibited a carbide precipitates with small amount of martensite the HTHAZ exhibited a martensite, the MTHAZ exhibiting the higher hardness, the LTHAZ exhibited Cr- carbide. The grain growth which occurred in FZ and HTHAZ is a major problem accompanied with fusion welding of FSSs. It shows that the peak load and energy absorption of the welds were improved as the welding current increases due to the formation of larger FZ size at higher heat input. (2) In their research, the effects of electrode force, weld nugget, and hardness of spot welded steel joints are examined based on observed values of the experiment. Mechanical properties and the microstructure of the welded joints are having significant impact on weld nudge. The significant values of difference are identified in the hardness due to the changes presence in weld nudge. The mechanical properties and the microstructure on the heat affected zone is preserve higher value compare with welded zone. (3) Weld nudges and weld time are investigated through Finite element methods by two dimensional models in resistant spot welding. This analysis defined the effect of nugget size and weld time on AISI304L stainless steel sheet.

Study on effect of electrode force on resistance spot welding process

This paper deals with the effect of electrode force on resistance spot welding process. As one of the most important parameters during the process, the electrode force can influence the process in different aspects. Dynamic resistance, which can reflect the internal physical variation of the workpiece, is employed to monitor the characteristic variation of the workpieces. According to theoretical analysis, large electrode force may easily induce surface expulsion. Also, it can decrease the overall dynamic resistance values and postpone the time when first melting point appears, as well as enlarge the duration between times when first melting point and peak value appear. Larger electrode force induces the initial smaller nugget diameter, and then the nugget diameter has a higher growth speed. However, the overall nugget diameter may be smaller and its growth terminates earlier than when smaller electrode force is applied. Final experiments validated all the theoretical analysis.

On the development of nugget growth model for resistance spot welding

In this paper, we developed a general mathematical model to estimate the nugget growth process based on the heat energy delivered into the welds by the resistance spot welding. According to the principles of thermodynamics and heat transfer, and the effect of electrode force during the welding process, the shape of the nugget can be estimated. Then, a mathematical model between heat energy absorbed and nugget diameter can be obtained theoretically. It is shown in this paper that the nugget diameter can be precisely described by piecewise fractal polynomial functions. Experiments were conducted with different welding operation conditions, such as welding currents, workpiece thickness, and widths, to validate the model and the theoretical analysis. All the experiments confirmed that the proposed model can predict the nugget diameters with high accuracy based on the input heat energy to the welds.

EFFECT OF ELECTRODE FORCE ON FRACTURE TYPE OF DQSK STEEL RESISTANCE SPOT WELDS

Failure mode is a qualitative measure of resistance spot weld performance. To ensure reliability of resistance spot welds during vehicle lifetime, process parameters should be adjusted so that the pullout failure mode is guaranteed. In this paper, the effect of electrode force on the failure mode of drawing quality specially killed (DQSK) steel resistance spot welds during the quasistatic tensile-shear test is investigated. Results showed that there is a minimum weld nugget size to ensure pullout failure mode. It was found that increasing electrode force decreases fusion zone size and therefore leads to transition of failure mode from pullout to interfacial mode.

Effects of electrode force on microstructure and mechanical behavior of the resistance spot welded DP600 joint

In this paper, the effects of electrode force on the mechanical properties, weld nugget size, failure mode, microstructure and microhardness of the resistance spot welded dual-phase steel joint were investigated experimentally. The results indicate that different electrode forces generate different weld nugget sizes and there is a critical electrode force with which the weld nugget size and mechanical properties of the welded joint can accomplish their maximum values. The mechanical properties and failure modes of the welded joint are directly associated with the weld nugget size. In addition, the electrode force also alters the microscopic structure and grain size of the welded joint, but has a weak effect on the microhardness and martensite content of the welded joint.

The effects of electrode force, welding current and welding time on the resistance spot weldability of pure titanium

In this study, commercially pure titanium sheets (American Society for Testing and Materials grade 2) were welded by resistance spot welding at various welding parameters. The welded joints were subjected to tensile-shearing tests in order to determine the strength values. In addition, the hardness and microstructural examinations were carried out in order to examine the influence of welding parameters on the welded joints. The experimental results showed that increasing electrode force, welding current and welding time increased the tensile-shearing strength of the welded specimens. Hardness measurement results indicated that welding nugget had the highest hardness and this was followed by the heat-affected zone and the base metal. Microstructural examinations showed the growth of the weld nugget grains with increasing heat input. Besides, due to plastic deformation during the welding process, twins were formed and at the same time twins increased with increasing electrode force, welding current and welding time.

The Effects of Electrode Force on the Mechanical Behaviour of Resistance Spot‐Welded 5083‐O Aluminium Alloy Joints

Abstract: In this study, the effects of electrode force on the static and fatigue strength of spot welded joints of 5083‐O aluminium alloy sheets were investigated. The thickness of the sheet joints was 1.5 mm. Tensile‐shear joints with one spot weld were considered and three different load levels for electrode force were selected as 2500 N, 3000 N and 3500 N while the welding time and electric current were fixed during resistance spot welding process. Also, micro‐structures and micro‐hardness of cross‐sectional area of the test samples were investigated. The results show that increasing the electrode force from 2500 N to 3000 N has no major impact on the nugget size and fatigue strength of the specimens, but increasing the electrode force from 3000 N to 3500 N, despite reducing in the diameter of the nuggets, increases the fatigue life of the joints significantly. The results also indicate that increasing the electrode force increases the life associated with the crack initiation phase of total fatigue lifetime.

Effect of Electrode Force on Tensile Shear and Nugget Size of Austenitic Stainless Steel Grade 304 Welds Using Resistance Spot Welding

This research was to effect of electrode force on the tensile shear and nugget size of the resistance spot welding. The specimen was austenitic stainless steel 304 grade sheet metal 1.2 mm thickness. The electrode force are 1, 1.5, 2.0, 2.5, and 3.0 kN apply to the specimen. The replications in each treatment are 20 follow JIS Z 3136:1999 and JIS Z 3139:1978. Factor control, welding current 7 kA., time current flow 7 cycle and electrode tip diameter 6 mm. The welded specimens were tested by tensile shear testing according to JIS Z 3136: 1999, macro structure testing according to JIS Z 3139: 1978 and analysis results by using One-way ANOVA .The result showed that electrode force had affected on tensile shear and nugget size at 95% confidential (P value > 0.05). The low force induced the gab between specimen increasing then the current flow difficult to pass and both of gab between specimen and nugget seize had increase (Q=I2Rt). When the resistance increased so that fusion zone will have a high heating. It had affected to nugget size, heat affected zone and mechanical properties decreasing. The electrode forces are complete 2.5 kN. tensile shear 9.21 kN and nugget size 5.82 mm. The data can be applied to be used as process monitoring of resistance spot weld quality

Effect of Electrode Force Change on Spot Weld Quality of AHSS Using Servo Gun

Due to bad welds including small button, weld expulsion, and weld whisker etc., it is studied that the effect of constant and variable electrode force with servo gun on the weld quality of high strength steels with different thickness and materials. The results show that the electrode force plays an important role in resistance spot welding of AHSS as well as that of mild steels. Under the same welding current and time, better welds with higher tensile shear strength and larger nugget size can be obtained by optimizing electrode force curve using servo gun. The solutions could supply reference to study the prospect of servo gun in the joining of high strength steels.

Monitoring of Effect of Electrode Force on Resistance Spot Weld Quality Using Electrode Displacement Method

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.

Effects of Electrode Force on the Characteristic of Magnesium Alloy Joint Welded by Resistance Spot Welding with Cover Plates

Magnesium alloy AZ31B sheets were welded using the technique of resistance spot welding with cover plates. The effects of electrode force on the joining performance and pore formation during welding were investigated. The results reveal that the enhanced electrode force is an effective way to inhibit pore formation and improve magnesium alloy resistance spot welding performance.

Numerical study on the effect of electrode force in small-scale resistance spot welding

Since electrode force is an important process parameter in small-scale resistance spot welding (SSRSW), its effects on the electrical, thermal and mechanical behavior of the welding process when using direct current have been studied numerically in the present paper using the finite element method. The variations of contact radius, current density distribution and temperature profile at the sheet/sheet (S/S) and electrode/sheet (E/S) interfaces, the threshold weld times and the maximum diameters of the weld nuggets under three different levels of electrode force are investigated. The calculated results show that increasing electrode force will increase the contact radius at the contact interfaces and decrease the welding current density, and hence delay nugget initiation and growth. Increasing electrode force also decreases the cooling rate at the nugget center after the welding current is turned off.

簿鋼板のマッシュシーム熔接

This is a report on the effects of welding variables in mash seam welding of cold rolled and annealed low carbon rimmed steel sheets of lmm thickness on joint thickness, Erichsen value and tensile elongation along the weld line.Throughout the investigation, welding current and electrode force were varied in the wide range, while the rest of the condition were kept constant as follows:Welding speed 1m/min, weld time and cool time 4 _??_ and 2 _??_, and jointoverlap 1.5mm.The results obtained are as follows:-1. When the welding condition is properly chosen, the Erichsen value of over 10.0 and the tensile elongation of 30% along the weld line are obtained.2. In the range of the condition investigated. The electrode force of 600-700Kg and the welding current of 9000A may be recommended to obtain the best ductility of the weld.3. Ductility of weld decreases with the increase of welding current, and the lower becomes the electrode force, the higher is the decrease rate, but too low current results in the incomplete bond and very poor ductility.4. Joint thickness decreases with the increase of welding current and electrode force, but the effect of electrode force is not so distinct as that of current.5. The microstructure of the weld section at the time when ductility is the best presents recrystalized ferrite grains and small islands of bainite and martensite surrounding cementite, and there is no regions of fine ferrite and pearlite or columnar dendritic nugget which show the temperature has risen above the critical or melting limits.