Friction Welded Butt Joints Research Articles

Fatigue strength improvement of linear friction welded butt joints of low carbon steel by pressurizing after oscillation

Although linear friction welding (LFW) has received significant attention as an effective solid-state welding method, the fatigue properties of LFW joints have not been fully investigated. In this study, the fatigue strength of the steel joints fabricated using LFW was investigated and improved by increasing the pressure after oscillation. Low-carbon steel SM490A was successfully joined using LFW without unbonded areas or apparent softening in the heat-affected zone (HAZ). The microhardness, microstructure, weld toe shape, and fatigue life were assessed to investigate their relationships with the pressure conditions after oscillation. The results indicated that increasing the pressure after oscillation improved the area fraction of martensite (M) and the hardness of the weld interface center. The weld toe radius (ρ) and weld toe angle (α) also increased regardless of the upset control condition. The increasing of the pressure after oscillation from 50 MPa to 300 MPa increased ρ from 0.4 mm to 2.1 mm and the α increased from 92.7° to 103.4° at the weld center, accompanied by a reduced stress concentration factor (Kt) from 3.0 to 1.7. Under the fatigue test conditions of the stress range of 380 MPa, the fatigue life of the LFW as-welded joints was increased by approximately 31 % when the pressure after oscillation was 250 MPa compared to that of 50 MPa and by 87 % when it was 300 MPa compared to that of 250 MPa. Despite the possibility of fracture initiation at the weld toe at the edge of the LFW joints, the fatigue strength demonstrated a substantially longer fatigue life than the S-N design curve FAT90 recommended by the International Institute of Welding.

Investigation and optimization of friction stir welding process parameters of stir cast AA6082/ZrO2/B4C composites

Abstract In the present investigation, aluminium-based alloy (AA6082) is stir-casted with 3 % ZrO2 and 5 % B4C reinforcement particulates to fabricate Aluminium Metal Matrix Hybrid Composites (AMMHCs) which are further friction-stir welded at different welding conditions to develop a welded joint with optimum ultimate tensile strength (UTS) and microhardness. This newly developed AMMHC will find its specific application as bulkhead partitions in the hull of a ship due to its excellent properties, such as lower weight, higher specific strength, superior resistance to wear, and lower thermal expansion coefficient than that of AA6061 and AA5083 composites. The friction-welded butt joints performance of AA6082/3%ZrO2/5%B4C is generally determined by varying the FSW process parameters such as tool rotational speed (TRS), welding speed (WS), axial load (AL), tool tilt angle (TTA), tool pin profile (TPP), shoulder diameter (SD), etc. In the present work, the empirical relationships are established between parameters highly influencing FSW process (TRS, WS, and AL) and their responses (UTS and weld nugget microhardness (WNH)). The desirability approach is employed for predicting the optimal UTS and WNH. The corresponding values of input process parameters are TRS of 1030.95 rpm, WS of 38.5 mm/min, and AL of 5.88 kN. The calculated UTS and WNH for the present investigation are 239.98 MPa and 94.2 HV, respectively, and these values are consistent with the results of validation experiments.

Evaluation of torsional characteristics of SUS304 stainless steel friction welded butt joints by digital image correlation method

Evaluation of torsional characteristics of SUS304 stainless steel friction welded butt joints by digital image correlation method

Impact performance of friction welded butt joints between 6061-T6 aluminium alloy and type 304 stainless steel

The tensile strength and energy absorption for dissimilar metal friction welds between 6061-T6 Al alloy and type 304 stainless steel at high rates of loading were determined using the split Hopkinson bar. Cylindrical tensile specimens machined from as welded butt joints of 13 mm in diameter were used in both static and impact tests. Friction welding was conducted using a brake type friction welding machine under two different welding conditions. The effects of welding conditions and loading rate on the joint tensile properties were examined. Results show that the joint tensile properties were greatly affected by the welding parameters, and were slightly enhanced with increased loading rate. Scanning electron microscope observations revealed that the tensile fracture modes in the butt joint specimens varied with loading rate and depend on welding conditions. Microhardness profiles across the weld interface were measured to investigate the extent of the heat affected zone. The slight enhancement of the joint tensile properties with increasing loading rate is primarily attributed to the strain rate dependence of the thermally softened 6061-T6 Al alloy base material.

Impact tensile properties of 6061 aluminium alloy to SUS 304 stainless steel friction-welded butt joints

(2003). Impact tensile properties of 6061 aluminium alloy to SUS 304 stainless steel friction-welded butt joints. Welding International: Vol. 17, No. 7, pp. 514-523.

Impact Tensile Properties of Friction Welded Butt Joints between 6061 Aluminum Alloy and Type 304 Stainless Steel

The tensile strength and energy absorption for dissimilar metal friction welds between 6061 Al alloy and Type 304 stainless steel at high rates of loading are determined using the split Hopkinson bar. Cylindrical tensile specimens machined from as-welded butt joints of 13 mm in diameter are used in both static and impact tests. Friction welding is conducted using a brake type friction welding machine under two different welding conditions. The effects of the welding conditions and loading rate on the joint tensile properties are examined. Results show that the joint tensile properties are greatly affected by the welding parameters, and are slightly enhanced with increasing loading rate. Macroscopic observations reveal that the tensile fracture modes in the butt joint specimens vary with loading rate, depending on the welding conditions. Microhardness profiles across the weld interface are measured to investigate the extent of the heat-affected zone (HAZ). The slight enhancement of the joint tensile properties with increasing loading rate is due to the strain-rate dependence of the thermally-softened 6061 Al alloy base material.

Impact tensile properties of 6061 aluminium alloy to SUS 304 stainless steel friction-welded butt joints

Impact tensile properties of 6061 aluminium alloy to SUS 304 stainless steel friction-welded butt joints

Stress‐strain characteristics of S15C carbon steel friction‐welded butt joints under impact tensile loading

Stress-strain characteristics of S15C carbon steel friction welded butt joints under impact tensile loading are evaluated using the split Hopkinson bar. Round tensile specimens machined from as-welded butt joints of 13 mm diameter are used in both static and impact tension tests. Friction welding is carried out using a brake type friction welding machine under fixed welding conditions. The effect of strain rate up to e≅700/s on the tensile stress-strain characteristics of both friction welded butt joints and a base material (S15C carbon steel) is studied. It is shown that the flow stress for friction welded butt joints is always higher than that for the base material at low and high rates of strain, but the former are less sensitive to strain rate than the latter. Microhardness measurements are conducted to examine the extent of the heat-affected zone (HAZ) across the weld interface. Metallographic examination reveals that there are zones of different grain structure through the weld region. The increase in the flow stress for friction welded butt joints is attributed to the presence of a locally-hardened region within the HAZ.

６０６１アルミニウム合金／ＳＵＳ３０４ステンレス鋼摩擦圧接継手の衝撃引張特性

６０６１アルミニウム合金／ＳＵＳ３０４ステンレス鋼摩擦圧接継手の衝撃引張特性

110 Impact Tensile Properties of Friction Welded Butt Joints between 6061 Aluminum Alloy and Type 304 Stainless Steel

The tensile strength and energy absorption of dissimilar metal friction welds between 6061 Al alloy and Type 304 stainless steel at high rates of loading are determined using the split Hopkinson bar. Round tensile specimens machined from as-welded butt joints of 12 mm diameter are used in both static and impact tension tests. Friction welding is conducted using a brake type friction welding machine under two different welding conditions. The effects of welding parameters and loading rate on the tensile properties of friction welded butt joints are investigated. It is demonstrated that the tensile properties are greatly affected by the welding conditions, and are slightly enhanced with increasing loading rate. Macroscopic observations reveal that the tensile fracture mode of friction welded butt joints varies with loading rate, depending on the welding conditions. Microhardness measurements are performed to examine the extent of the heat-affected zone (HAZ) across the weld interface. The slight enhancement in the tensile properties of friction welded butt joints with increasing loading rate is due to the strain rate dependence of the thermally-softened 6061 Al alloy base material.

衝撃引張荷重下におけるＳ１５Ｃ炭素鋼摩擦圧接継手の応力‐ひずみ特性

Stress-strain characteristics of S15C carbon steel friction welded butt joints under impact tensile loading are evaluated using the split Hopkinson bar. Round tensile specimens machined from as-welded butt joints of 13 mm diameter are used in both static and impact tension tests. Friction welding is carried out using a brake type friction welding machine under fixed welding conditions. The effect of strain rate up to e≅700/s on the tensile stress-strain characteristics of both friction welded butt joints and a base material (S15C carbon steel) is studied. It is shown that the flow stress for friction welded butt joints is always higher than that for the base material at low and high rates of strain, but the former are less sensitive to strain rate than the latter. Microhardness measurements are conducted to examine the extent of the heat-affected zone (HAZ) across the weld interface. Metallographic examination reveals that there are zones of different grain structure through the weld region. The increase in the flow stress for friction welded butt joints is attributed to the presence of a locally-hardened region within the HAZ.

６０６１アルミニウム合金／Ｓ４５Ｃ炭素鋼摩擦圧接継手の衝撃引張強さ

The tensile strength of dissimilar friction welds between 6061 aluminum alloy and S45C carbon steel at high rates of loading is evaluated using a tensile version of the split Hopkinson bar. Round tension specimens are machined from 30 mm diameter friction welded butt joints. Friction welding is carried out using a brake type friction welding machine under fixed welding conditions. All quasi-static and impact tests on the as-welded tension specimens having the weld interface in the middle of the gage length are conducted at room temperature. The test results indicate that the joint tensile strength decreases considerably with increasing loading rate. Macroscopic observations of the fracture surfaces of broken tension specimens reveal that the static fracture takes place in the 6061 aluminum alloy region close to the weld interface, while the impact fracture occurs at the weld interface. The microindentation hardness tests are performed across the weld interface in an attempt to investigate the extent of the heat-affected zone (HAZ) due to friction welding. The microstructure and the distributions of aluminum and iron at the weld interface region are examined with the help of a scanning electron microscope and an electron probe micro-analyzer. The decrease in joint tensile strength with increasing loading rate may be attributed to the presence of very thin brittle intermetallic compounds formed at the weld interface during the friction welding operation.

６０６１アルミニウム合金とＳＵＳ３０４ステンレス鋼の異種摩擦圧接継手の疲労強度特性

Friction welded butt joints have come into wider use because of their easiness to fabricate composed shafts such as steering shaft, rear axle shaft and so forth. However, the welding condition optimum to obtain high joint efficiency in terms of fatigue strength has not yet been established because of a scarcity of fatigue strength data. Accordingly, it is indispensable to accumulate fatigue strength data on a variety of joints fabricated under different friction welding conditions. In this study, the rotating bending fatigue behavior of butt joints of aluminum alloy A6061 and austenitic stainless steel SUS304 which were friction welded at three different upset pressures are discussed. The results indicate that the butt joints friction welded at the highest upset pressure give almost the same fatigue strength as that of the aluminum alloy specimen. But the distribution of the fatigue lives of this kind of joint is larger than that of the joint of similar aluminum alloy, presumably depending on the scatter of fatigue crack initiation life.

Impact properties of the weld interface in SCM415/SCM415 friction welded butt joints

Summary Instrumented Charpy impact testing was carried out at various temperatures from −196 °C to 200 °C in order to clarify the absorbed energies, impact values, transition temperatures and fracture behaviour at the weld interface of SCM415/SCM415 friction welded joints; the results were examined and compared with the impact properties of the base metal. The results may be summarised as follows: 1. The impact energy transition curve of the weld interface in the transition region shifted to the lower temperature side in comparison with that of the base metal. 2. The impact energy transition temperature was approximately 30 °C at the weld interface and approximately 57 °C for the base metal; these temperatures were consistent with the temperatures estimated from the impact fracture surface. 3. Resistance to crack initiation at the weld interface in the transition region increased markedly in comparison with that of the base metal. 4. Impact resistance at the weld interface under the friction welding conditions employed in this experiment largely exceeded that of the base metal.

Fatigue fracture characteristics of friction welded butt joints with corrosion pits

Summary Studies on the fatigue behaviour of friction welded butt joints between similar carbon steels in ordinary atmospheric environments have revealed that the fatigue strength of the joint is higher than that of the base metal, but the joint shows the larger scatter in fatigue life. On the other hand, the results of corrosion fatigue tests on the joint carried out in artificial seawater indicated that: (1) the corrosion fatigue strength of the joint was almost the same as that of the base metal in the long life region; (2) the scatter in corrosion fatigue life in the joint became smaller with an increase in fatigue life than that of the base metal specimen; and (3) the above mentioned characteristics were governed by corrosion pits preferentially generated near the weld interface. The main aim of this study is to clarify the cause of the fatigue strength reduction by corrosion pits. For this purpose the joint and base metal specimens were immersed in artificial seawater in a stress free condition to ge...

炭素鋼同種摩擦圧接継手の腐食疲労強度特性の接合方式依存性について

Though friction welded butt joints have come into wider use machine elements and structural members, valid evaluation method of the joint performance, especially under service load conditions, has not been established yet. The reliability of this type of joint has been supported only by empirical knowledge accumulated up to the present. In order to clarify the fatigue behaviors of the joint, we have carried out a series of fatigue tests on several sorts of friction-welded butt joints in ordinaly atmospheric environment, and have revealed that the fatigue strength of the joint is higher than that of the base metal, but the lives show the large scatter. Evaluation of corrosion fatigue behavior of frictionwelded joints is also an urgent issue, because some of the joints are practically used in corrosive environments.The main aim of this study is to reveal the relationship between the fiber flow conditions near the weld interface of the joint and their corrosion fatigue resistance. For this purpose, a series of experiments was carried out on four friction-welded butt joint specimens composed of a similar structural carbon steel fabricated by different friction welding conditions. This study covers following four phases : (1) Dependence of fiber flow conditions on friction welding procedure, (2) corrosion responce of the four joints fabricated by different friction welding procedures, (3) fatigue strength behavior of joints with corrosion pits in ordinaly atmospheric environment, and (4) corrosion fatigue resistance of respective joint.The results of this study revealed that the corrosion fatigue resistance of the joint was well correlated with the fiber flow conditions of the joint; many and deep corrosion pits were generated on the surface area intersecting the fiber flow and the notch effect of the corrosion pits resulted in the reduction of fatigue strength. In other words, joint specimen wishout the surface area intersecting the fiber flow shows excellent corrosion fatigue performance.

腐食ピットを有する摩擦圧接継手の疲労破壊特性

Studies on fatigue behavior of friction welded butt joints composed of similar carbon steel in ordinary atmospheric environment have revealed that the fatigue strength of the joint is higher than that of the base metal, but the joint shows the larger scatter of fatigue lives. On the other hand, results of corrosion fatigue tests on the joint carried out in artificial seawater indicated that, (1) the corrosion fatigue strength of the joint was almost the same as that of the base metal in long life region, (2) scatter of the corrosion fatigue lives of the joint bacame smaller with the increase in fatigue life in comparison with the case of base matal specimen, and (3) above mentioned characteristics were governed by corrosion pits preferentially generated near the weld interface.The main aim of the present study is to clarify the cause of the fatigue strength reduction by corrosion pits. For this purpose the joint and base metal specimens were immersed in artificial seawater at stress free condition to generate corrosion pits, and rotating bending fatigue tests were carried out on the specimens with corrosion pits near weld interface in ordinary atmospheric environment. Reference data were also obtaind by using specimens without corrosion pits. Results of the study clearly indicated that the corrosion pits near the weld interface decreased the fatigue strength of the joint. Fatigue strength reduction due to the corrosion pits was well correlated with the hardness at fracture site. Furthermore, the fatigue strength reduction factor took considerablely high value for the specimen immersed in artificial seawater during long time, which suggests that the other detrimental factor such as grain boundary corrosion gives the effect to decrease the fatigue strength of the joint with corrosion pits. Additionally, effect of corrosion pits on the fatigue strength reduction was discussed by replacing tentatively with the effect of circumferential notch.

Ｓ２５Ｃ炭素鋼同種摩擦圧接継手の人工海水中における腐食挙動

Friction welded butt joints are widely used as machine members and structural elements, but valid evaluation method of the joint performance, especially under service load conditions, has not been established yet. Evaluation of corrosion fatigue behaviors of the joint is one of the important problem, for some joints are used in pollutive environments. In our previous paper, corrosion fatigue behaviors in artificial seawater were investigated on S25C/S25C friction welded butt joints. The results indicated that the S-N curve for corroision fatigue strength of the joint specimen showed steeper slope than that of the base material and the strength of the joint took almost the same value as that of the base material specimen in long life region, and the scatter of fatigue lives became smaller in accordance with the increase in fatigue life contrary to the case of the base material specimen. Detailed observations of corrosion pits and non-propagation cracks of run-out specimens suggested that the above mentioned corrosion fatigue characteristics of the joint was governed by corrosion pits generated preferably on exposure surface of the transitional plane of fiber flow directions developed at the final stage of friction welding process.The present study was carried out to clarify the corrosion behaviors of the joint in more detail. Joint specimens were immersed in artificial seawater at stress free condition during 5 and 10 days. Distribution of corrosion pits near the weld interface and geometrical factors of pits were evaluated precisely, and the difference of corrosion behaviors between the joint and the base material were also discussed. The results of this study gives valid support for the estimation on the corrosion fatigue characteristics of the joint indicated in our previous paper.

炭素鋼同種摩擦圧接継手接合部の疲労き裂進展抵抗について

In order to evaluate the resistance to growth of fatigue cracks propagating along the weld interface of friction welded butt joints composed of carbon steel/carbon steel, a series of fatigue crack growth tests were carried out on S25C/S25C and S45C/S45C joints under three different cyclic load conditions. To investigate the effect of residual stress distribution in the specimen introduced in friction welding process on the crack growth behavior, two types of CCT plate specimens with a thickness of 2mm were prepared for respective carbon steel joints; one was the specimen as welded and another was the residual stress relief treated specimen. And the results of these joint specimens were discussed in comparison with those of the annealed CCT base metal plate specimens. First of all, whole crack growth behavior was investigated under increasing ΔK condition, and then the dependence of crack growth rate on the weld interface location was studied under a constant ΔK condition, and finally the ductility of the weld interface was evaluated indirectly through the observation of crack growth retardation behavior induced by the application of single static over-load during crack growth under constant ΔK. The results indicate that the residual stress does not play an important role on the fatigue crack growth of the joints, and metallurgical feature of the weld interface governs the fatigue crack growth behavior of the joints. And, the decrease in crack growth rate of the joint specimens by the application of the over-load is less than that of respective base metals, which indicates that the ductility of the weld interface of both joints is less than that of respective base metals.

摩擦圧接継手の耐破壊性能について Ｓ４５Ｃの摩擦圧接継手の場合

In order to determine the requisite value of toughness for friction welded joints on the basis of fracture mechanics, Charpy impact test and fracture toughness test were carried out at various temperatures on the friction welded butt joints composed of carbon steel JIS. S45C and the base metal.The experimental results indicated that the Charpy absorbed energy of the friction welded joints was almost equal to that of the base metal in the temperature range below room temperature, while the absorbed energy of the joints was about a half of those for the base metal above room temperature. The fracture toughness of the friction welded joints increased with an increase in temperature, but the toughness was slightly lower than those of the base metal over the whole temperature range. Particularly, in the temperature range above 185K, the value of the net section stress σnet for fracture of the joint was higher than the 0.2% proof stress of the base metal.When the transition temperature for the Charpy absorbed energy was compared with that for the fracture toughness, the former was much higher than the latter. This suggests that the fracture toughness for the joints is high enough, even when the Charpy absorbed energy is low. Furthermore, the usable critical stress for the friction joints with circumferential or penny-shaped cracks was estimated for various kinds of specimen size and temperature based on the experimental results of fracture toughness.