Performance Of Welded Joints Research Articles

Evaluation of the performance of an aluminium alloy friction welded joint by image analysis

Summary In making a friction welded joint, it is necessary to produce a flash at the weld during the welding process. In this research, the flash was measured by the image processing method and the joint performance was evaluated by the data from such measurements. The monochrome image of the flash was transformed to binary image data in order to remove noise in the image processing process. Then, the characteristics of the flash were extracted as numerical information on the outline of the welds. The measured features were the height, width, curvature radius of the toe and sectional area of the flash. In this way, an evaluation of friction welded joint performance can be made by recognition of the flash shape.

構造用鋼のエレクトロスラグ溶接金属の靭性向上に関する研究 （第１報） 構造用鋼のエレクトロスラグ溶接金属内における衝撃特性の不均一性に関する研討

The purpose of this paper is to clarify the weld joint performance, especially the impact characteristics of the weld metal produced by electroslag welding (ESW) and submerged arc welding (SAW) by directing our attention to the high heat input welding processes which are usually applied for the manufacture of four side thick plate box column. Two types of SM490A 40 mm thickness have been used in this test. The test results are summarized in the following.(1) As for the impact characteristics of high heat input weld metal, the absorption energy values (vE value) of weld metal made by ESW are generally lower than those by SAW.(2) As for the vE values of various locations in high heat input weld metal by ESW, the vE value in the center of weld metal (Core) is considerably lower than those in peripheral locations of weld metal (Rim).(3) Macrostructure of ESW weld metal suggested that fine crystal grains were generated in the core with coarse crystal grains in the rim.(4) In the weld metal by ESW the impact value of fine grain core area is low and those in the peripheral coarse grain rim area are high on the contrary. This result disagrees with the conventional theory about the general relation between impact value and grain size.(5) It is found that the vE value of weld metal by ESW shows a tendency to decrease according to the increase of welding heat input (Q) and becomes low at the Q of 30.0 kJ/mm (up to 80.0 kJ/mm). Furthermore, the decrease of vE value related to the increase of welding heat input has not be caused by the change of chemistry such as C, Si, Mn, P and S in the weld metal.

Application of AC‐MIG narrow‐gap welding to butt joints in 980 M Pa high‐strength steels (5th report). Development of AC‐MIG welding

Summary Previous papers have shown the high‐current AC‐MIG welding process to be superior to the conventional DC‐MIG process in terms of welding efficiency and welded joint performance. The authors have used the AC‐MIG process to weld heavy‐gauge steel plates at a tensile strength level of 980 MPa. Weld metal with a very low hydrogen content is obtained by the newly developed process, resulting in a reduced preheating temperature during welding of high‐strength steels. The AC‐MIG process also produces an arc climbing effect with electrode negative polarity ‐ a desirable effect in narrow‐gap welding. AC‐MIG weld metal further contains low oxygen, conferring high toughness. As a result, a narrow‐gap AC‐MIG welding process has been developed to ensure high efficiency in processing and metallurgically high‐quality welds in welding of 980 MPa high‐strength steels for penstocks (pressure shafts) in hydroelectric power stations. Welding wires with chemical compositions satisfying suitable strength and toughness ...

Investigation of fusion welded butt joints in structural steels

In the present paper research work is presented combining material related research, weld fabrication related research and research in the field of numerical analysis of welded joint performance. Elements belonging to this extensive combination are mechanical testing, fracture mechanics testing of small scale and full thickness specimens, component testing including engineering defect assessment and numerical modelling using finite element method. Examples are given for each of the above mentioned elements. Mechanische Untersuchungen an schmelzgeschweißten Verbindungen beinhalten einerseits werkstoffbezogene Untersuchungen zur Optimierung der mechanisch-technologischen und bruchmechanischen Eigenschaften schweißbarer Stähle. Außerdem gehört die Prüfung entsprechender Schweißgüter dazu. Beides erfolgt unter Berücksichtigung der schweißtechnischen Fertigungsbedingungen sowie der Randbedingungen der verschiedenen Prüfverfahren. Experimentelle wie auch numerische Untersuchungen führen – unter Berücksichtigung der mechanischen Inhomogenität – zur Optimierung des Beanspruchungsverhaltens von Schweißverbindungen.

A multiple crack model for fatigue in welded joints

Several linear elastic fracture mechanics (LEFM) models have been developed to simulate the fatigue performance of welded joints, particularly for offshore structures. Such models are used to estimate residual life when cracks are discovered in service. These models are also used to interpret available experimental results and may eventually be used in design. A key element to the success of such models is the realistic modelling of fatigue crack shape development. In all fatigue testing of welded T-plate, pipe-plate and tubular joints in the Canadian Offshore Research Programme, care was taken to monitor crack shape development using beach marks and potential-drop techniques. Crack shape development was significantly influenced by specimen thickness, stress distribution and environment. A fatigue model is proposed which explicity models the growth and coalescenceof multiple semi-elliptic fatigue cracks. Such a model has the potential of modelling geometry and environmental effects through their influence on crack shape development. The basics of this model, including coalescencence and the calculation of stress intensity factors, are discussed. Verification studies involving both T-plate and pipe-plate specimen geometries are presented.

Fracture toughness analysis of heat-affected zones in high-strength low-alloy steel welds

This study is concerned with a correlation of fracture toughness with microstructural factors in heat-affected zones (HAZs) of a normalized high-strength low-alloy (HSLA) steel. In order to explain weld joint performance, tensile and plane strain fracture toughness tests were conducted for the simulated coarse-grained HAZ microstructures. The micromechanisms of fracture processes involved in void and microcrack formation are identified byin situ scanning electron microscopy (SEM) fracture observations and void initiation study. The fracture toughness results are also interpreted using simple fracture initiation models founded on the basic assumption that a crack initiates at a certain critical strain or stress developed over some microstructurally significant distance. The calculated KIc values are found to scale roughly with the spacing of the stringer-type martensite islands associated with voids, confirming that martensite islands play an important role in reducing the toughness of the coarse-grained HAZs. These findings suggest that the formation of martensite islands should be prevented by controlling the chemical compositions and by using the proper welding conditions to enhance fracture toughness of the welded joints of the HSLA steel.

The static and fatigue performance of welded joints for offshore platforms: Bramante, M. EUR Report 13636 1992 133 pp (in Italian)

The static and fatigue performance of welded joints for offshore platforms: Bramante, M. EUR Report 13636 1992 133 pp (in Italian)

Performance of welded joints in TMCP steel plates

Performance of welded joints in TMCP steel plates

Numerical Prediction of Welded Joint Performance—Relative Criticality of Weld Defect and Remote Deformation

Abstract Structural integrity problems which deal with welded sections are common in the pressure vessel and piping industry. The current work uses continuum fracture toughness concepts to determine the structural integrity of a butt-welded plate with a lack of penetration defect in the weld material. The difference in weld and base metal properties are explicitly included in the computational simulation. The analysis technique presented does not require the analyst to assume a failure location. The critical strain energy density associated with fracture of a material at the continuum scale is used as the failure criterion.

On the effect of welding condition on joint performance and fatigue strength characteristics of similar austenite stainless steel friction welding joint—study on fatigue strength of friction welding joint: Yamamoto, Y., Sakai, N., Ogawa, K. and Kaga, S. Setsudai Gakujutsu (Sci. Rev. Setsunan Univ.) A Feb. 1989 (8), 17–37 (in Japanese)

Friction stir welding (FSW) is a relatively new solid-state joining process. This joining technique is energy efficient, environment friendly, and versatile. In particular, it can be used to join high-strength aerospace aluminum alloys and other metallic alloys that are hard to weld by conventional fusion welding. FSW is considered to be the most significant development in metal joining in a decade. Recently, friction stir processing (FSP) was developed for microstructural modification of metallic materials. In this review article, the current state of understanding and development of the FSW and FSP are addressed. Particular emphasis has been given to: (a) mechanisms responsible for the formation of welds and microstructural refinement, and (b) effects of FSW/FSP parameters on resultant microstructure and final mechanical properties. While the bulk of the information is related to aluminum alloys, important results are now available for other metals and alloys. At this stage, the technology diffusion has significantly outpaced the fundamental understanding of microstructural evolution and microstructure–property relationships.

高強度鉄筋SD50のガス圧接継手性能

高強度鉄筋SD50のガス圧接継手性能

A Simplified Approach to the Effect of Specimen Size on the Creep Rupture of Cross Weld Samples

Various methods are available to assess the performance of welded joints under creep conditions. One approach uses the creep rupture testing of cross weld geometries in uniaxial tension. This paper examines an idealized model of a cross weld specimen where the weld metal is weaker than the parent material. The analysis, which is developed from published work on brazed and soldered joints, characterizes the limit load of the specimen as a function of the weld thickness:specimen diameter ratio and the yield strengths of both materials. The limit load is then used to define a creep reference stress which may be applied to uniaxial data. The predictions of the failure location and failure time are compared with cross weld creep data generated within the CEGB as no suitable data were found in the general literature. Finally, the model is used to postulate a size or weld thickness:specimen diameter effect on stress rupture testing of cross weld geometries.

極低温用４０％Ｎｉ系溶接金属に関する研究 ＩＩ 突合せ溶接継手の静的引張強さ

The 40 % Ni type weld metal is undermatching for 9 % Ni steel with regard to static tensile strength. In this case, the tensile strength of welded joints is influenced remarkably by strength of weld metal and base metal, and by the welding conditions such as heat input, groove shape and so on. Welded joint performance tests were carried out, in this report, to investigate the static tensile strength of MIG welded joints of 9 % Ni steel with 40 %Ni type weld metal. Main experimental results are summerized as follows:(1) The transverse tensile strength of welded joints increases with decreasing relative thickness (average width of weld metal/plate thickness). Therefore, it is beneficial, both for increasing strength and for improving efficiency, to narrow the groove as far as possible according to the plate thickness.(2) The transverse tensile strength of welded joints decreases with increasing welding heat input; but, in case of vertical position, it is possible to obtain 66.8 kg/mm2 (95 Ksi) or more within heat input of 35 KJ/cm.(3) It may be considered that, in case of multi-pass weld metal, the strength of intermediate pass weld metal has increased due to the precipitation hardening caused by the fine carbides of molybdenum and chromium.(4) It was confirmed by center-notched wide plate tension test that the weld metal and fusion zone possess a satisfactory cryogenic fracture toughness as all the fracture occurred in a high-stress ductile manner with fracture stress equal to the cryogenic strength of the 40 % Ni type weld metal.

Diagram for the prediction of weld heat-affected zone microstructure

The performance of welded joints, both during fabrication and operation, can depend critically upon the microstructure ofthe heat-affected zone, which, in a steel of given composition, is a function of the welding procedure andjoint geometry. The selection of suitable welding conditions which avoid the formation of crack-sensitive structures is clearly desirable. Standard heat-flow equations have been used in conjunction with continuous cooling transformation diagrams, determined using a weld simulation and dilatometric technique, to predict as-welded heat-affected zone microstructures for a wide range ofwelding conditions. A novel microstructure-welding diagram is described in which the variation in heat-affected zone microstructure as a function of process heat input, joint thickness, and preheat temperature is presented in a readily comprehensible form. A 0.5Cr-Mo-V steam-pipe composition is used as a detailed example, but the method is, in principle, applicable to a wide range ofsteel compositions.

Tests of the Resistance to Repeated Pressure of Forged, Riveted, and Welded Boiler Shells

Abstract Data regarding the performance of welded joints in resisting repeated stresses are very important in any consideration of the adoption of welded construction for power boilers, and it is the object of this paper to present such data. Comparative tests were made on (1) a standard A.S.M.E. riveted drum, (2) manganese-steel riveted drum, (3) forged seamless-steel shell, (4) two forge-and-hammer-welded shells, and (5) eight fusion-welded (metallic-arc) shells, each drum or shell being subjected to applications of pressure well above the allowable working pressure. The results indicate that under repeated stress properly made welded joints are stronger than the plates themselves when weakened by “stress raisers” such as small holes or surface defects. The tests also give useful data on the strength of drum heads when subjected to intermittent pressures.