Thick Welded Joints Research Articles

厚板溶接継手のクリープ特性の解明と改善 ２ 簡易解析モデルによる厚板溶接継手のクリープ寿命予測

The information of the creep behavior of the thick welded joint is very important to secure the safety of the elevated temperature vessels like the nuclear reactors. The creep behavior of the thick welded joint is very complex, thence it is difficult to practice the experiment or the theoretical analysis.A simple accurate model for theoretical analysis was developed in the first study. The simple model is constructed of several one-dimensional finite elements which can analyze three-dimensional creep behavior under a assumption. The model is easy to treat, and needs only a little labor and computation time to simulate the creep curve and local strain of the thick welded joint.In this second study, the capability of the model is expanded to estimate the creep life of the thick welded joint. New model can easily estimate the time of the rupture of the thick welded joint. It is verified by comparing the result with the experimental one that the model can accurately predict the creep life. The histories of the local strains to the rupture time may be observed in the simulation by using the model. The information will be useful to improve the creep characteristics of the joints.

Influence of residual welding stresses, overload and specimen preparation on fatigue crack growth under axial compression

Double edge notched axial compression specimens taken from thick welded steel joints have been used to grow fatigue craks under pulsating compressive loads at mean stresses up to 50% of that needed for general yielding. The redistribution of residual stresses during specimen preparation and during crack growth influences the nucleation, growth rate and extent of fatigue cracks. Crack growth rates which are comparable to the equivalent tensile situation have been observed in as-welded, welded plus overloaded and stress relieved plus overloaded joints. Multiple nucleation and curved crack profiles have been observed in all cases.

Development of simple model for creep analysis of thick welded joints (1st report): Creep characteristics of thick welded joints and their improvement

Summary To ensure the safety of high‐temperature facilities, such as fast breeder reactors, throughout their service life, it is necessary to be able to predict their creep deformation with sufficient accuracy. The welds produced in the thick plates of these facilities have an extremely complex thermal history and therefore extremely in‐homogeneous characteristics, including creep behaviour. This makes it difficult and laborious to run creep tests on thick welded joints, which require the use of a high‐capacity test machine. Strict theoretical analysis of thick welded joints is also never easy to perform. This paper describes a simple and accurate model for theoretical analysis of thick welded joints. The model is composed of several one‐dimensional finite elements able to analyse three‐dimensional creep behaviour. The model is easy to handle and needs little effort and computer time to predict the creep curves and local strain of thick welded joints. A comparison of the experimental and theoretical resul...

厚板溶接継手のクリープ特性の解明と改善（第１報） 厚板溶接継手の簡易クリープ解析モデルの開発

The information of the creep behavior of the thick welded joint is very important to secure the safety of the elevated temperature vessels like the nuclear reactors. The creep behavior is very complex, thence it is difficult to practice the experiment and the theoretical analysis.A simple accurate model for theoretical analysis was developed in this study. The simple model is constructed of several one-dimensional finite elements which can analyze three-dimensional creep behavior. The model is easy to treat, and needs only a little labor and computation time to predict the creep curve and local strain of the thick welded joint. It was verified by comparing them with experimental results that the model can accurately simulate the creep behavior of the thick welded joint.By using this model, the various important creep behaviors of the thick welded joint will be cleared to improve the creep characteristics of the joint.

Effect of thickness on fatigue behaviour of notched plates

The effect of plate thickness on the fatigue behaviour of V-notched plate specimens, with geometry simulating 19.5 and 39.0 mm thick welded joints, tested in air with constant amplitude loading under four-point bending was investigated. Fatigue crack growth was monitored using a multiple-probe ACPD technique. Test results are discussed in terms of S-N, life-thickness and strength-thickness plots. Crack growth results are evaluated using fracture mechanics. The thickness effect for these specimens without residual stress or welding defects is comparable with results reported in the literature for welded joints. This suggests that the thickness effect for welded joints is primarily due to geometrical factors.

Effect of the degree of compactness of the cross section of soft interlayers

In practice it is often necessary to determine the mechanical properties (OT, aB) of nondetachable joints in the form of composites consisting of a strong metal base T and a soft interlayer M; these composites may have different degree of compactness of the cross section = S/B (e.g,, in laboratory tests of mechanically inhomogeneous welded specimens, specimens cut out of thick welded joints, etc.), Because of the difference in compactness of the section, the results of such tests are mutually not comparable [i]. The use of the dependences obtained in [2, 3] and other works for evaluating the effect of the compactness of the cross section on the mechanical properties of soft interlayers in composites leads to considerable errors, especially when there is only a small difference between the mechanical characteristics of the materials T and H (oTT/OT M, oBT/~I << 2),