High Temperature Fatigue of Welded Joints: Experimental Investigation and Local Analysis of Butt Welded Flat and Cruciform Specimens

2015 ◽  
Author(s):  
Kay Langschwager ◽  
Jürgen Rudolph ◽  
Alfred Scholz ◽  
Matthias Oechsner
Keyword(s):  
Thermal Loading ◽  
Welded Joint ◽  
Effective Strain ◽  
Mechanical Strain ◽  
Load Condition ◽  
Base Material ◽  
Welding Process ◽  
Image Correlation ◽  
Local Analysis ◽  
Weld Material

Austenitic stainless steel of type X6CrNiNb18-10 exhibits advantageous mechanical and chemical properties and is a common material for numerous applications in the nuclear power plant and chemical industries. Besides the mechanical strain induced by high pressure, the fatigue life in welded pipelines is affected by additional thermomechanical strains due to thermal loading. The welding process mainly determines the geometry and metallurgical constitution of the welded joint. Therefore, the butt welds additionally influence the strain gradient along the component and reduce its lifetime. While the base and weld material are similar, they show different softening and hardening behavior, especially at ambient temperature. Cyclic hardening occurs in the base material, whereas cyclic softening can be observed in the weld material. The hardness distribution along the welded joint reveals no clear differentiation of base material, the heat affected zone and weld material. The attributes of the individual materials cannot be transferred to the welded joint automatically. Thus, the analysis of the interaction between the materials along the welded joint is a main topic of this research. To this end, digital image correlation is used for different kinds of specimens and load conditions. The position along the testing area at which fatigue failure occurs depends on the specimen type and the load condition but not on the temperature. Further, isothermal and anisothermal fatigue tests on welded cruciform specimens are presented. The common practice of the effective strain is discussed for the analyzed conditions.

High Temperature Fatigue of Welded Joints—Experimental Investigation and Local Analysis of Butt Welded Flat and Cruciform Specimens

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Kay Langschwager ◽  
Jürgen Rudolph ◽  
Alfred Scholz ◽  
Matthias Oechsner
Keyword(s):  
Thermal Loading ◽  
Welded Joint ◽  
Effective Strain ◽  
Mechanical Strain ◽  
Load Condition ◽  
Base Material ◽  
Welding Process ◽  
Image Correlation ◽  
Local Analysis ◽  
Weld Material

Austenitic stainless steel of type X6CrNiNb18-10 exhibits advantageous mechanical and chemical properties and is a common material for numerous applications in the nuclear power plant and chemical industries. Besides the mechanical strain induced by high pressure, the fatigue life in welded pipelines is affected by additional thermomechanical strains due to thermal loading. The welding process mainly determines the geometry and metallurgical constitution of the welded joint. Therefore, the butt welds additionally influence the strain gradient along the component and reduce its lifetime. While the base and weld material are similar, they show different softening and hardening behavior, especially at ambient temperature. Cyclic hardening occurs in the base material, whereas cyclic softening can be observed in the weld material. The hardness distribution along the welded joint reveals no clear differentiation of the base material, the heat affected zone, and the weld material. The attributes of the individual materials cannot be transferred to the welded joint automatically. Thus, the analysis of the interaction between the materials along the welded joint is a main topic of this research. To this end, digital image correlation (DIC) is used for different kinds of specimens and load conditions. The position along the testing area at which fatigue failure occurs depends on the specimen type and the load condition but not on the temperature. Further, isothermal and anisothermal fatigue tests on welded cruciform specimens are presented. The common practice of the effective strain is discussed for the analyzed conditions.

scholarly journals About the possibility of application of laser vacuum welding for the integration of elements of heat-protective structures from powder materials

2021 ◽  
pp. 88-99
Author(s):  
Walid Alnusirat ◽  
Alexandr Salenko ◽  
Olga Chencheva ◽  
Sergii Shlyk ◽  
Irina Gusarova ◽  
...  
Keyword(s):  
Thermal Loading ◽  
Welded Joint ◽  
Local Heating ◽  
High Vacuum ◽  
Welding Process ◽  
Honeycomb Structure ◽  
Diffusion Welding ◽  
Powder Materials ◽  
Thin Elements ◽  
Heat Shielding

The results of studying the process of laser vacuum welding of elements of heat-shielding panels made of heat-resistant dispersion-strengthened powder materials Ni-20Cr-6Al-Ti-Y2O3 of increased strength are presented. Such materials can be used to create ultralight heat-shielding panels, which are systems integrated on the surface of aircraft from typical modules of a cellular structure. Technical solutions of heat-insulating modules are considered, which are a cellular (honeycomb) structure consisting of two plates with a thickness of 0.1 to 0.14 mm, inside which there is a thin honeycomb filler. It is shown that the small thickness of the plates and the complexity of integrating the elements into a single system significantly impair the formation of a strong connection of such elements and do not allow the direct use of the known methods of diffusion welding or vacuum brazing. It has been established that laser welding of elements of heat-shielding structures in vacuum provides satisfactory strength of the structure of the heat-shielding element as a whole. Local heating at certain points prevents deformation of the parts to be joined during the welding process. The use of a pulsed Nd:Yag laser with a power of 400–500 W, operating in the frequency range of 50–200 Hz, allows welding with or without a filler powder. It was found that the use of filler additives practically does not affect the mechanical properties of the welded joint, however, it reduces the melt zone, while increasing the density of the welded joint. Based on the results obtained, it was concluded that it is possible to use laser vacuum welding for the integration of thin elements of heat-shielding modules. It is shown that a satisfactory joint strength is achieved by ensuring high cleanliness of the surfaces of elements before welding, maintaining a high vacuum (less than 10–2 Pa) and rational thermal loading of the surfaces of the elements to be integrated. The use of the proposed process makes it possible to obtain a stronger and denser seam in comparison with the known methods of soldering multicomponent powder dispersion-strengthened materials

scholarly journals Evaluation of residual stresses in a tube-to-plate welded joint

2019 ◽  
Vol 300 ◽  
pp. 19005 ◽  
Author(s):  
Andrea Chiocca ◽  
Francesco Frendo ◽  
Leonardo Bertini
Keyword(s):  
Residual Stresses ◽  
Numerical Simulations ◽  
Thermal Cycle ◽  
Transient Analysis ◽  
Welded Joint ◽  
Base Material ◽  
Welding Process ◽  
Deep Understanding ◽  
Experimental Tests ◽  
Temperature Dependent

A deep understanding of the manufacturing process is needed in order to achieve safety and quality requirements for parts and components; to this regard, residual stresses play an important role in welded structures. Residual stresses are mainly caused by the extremely severe thermal cycle to which the welded metal and base material are subjected to during welding process and their knowledge leads to a better static and fatigue assessment of welded joints. This work deals with the study of residual stresses for a tube to plate T-joint, made of S355JR carbon steel. The work was carried out by both numerical simulations and experimental tests. The numerical simulations were performed by Ansys FE code through a structural-thermal full transient analysis to evaluate stress, strain and temperature in each node at each step of the simulation. The “birth and death” method was employed, together with temperature-dependent material properties.A2Danda3D simulation were performed, in order to evaluate possible differences due to the welding process. Numerical results were compared to some preliminary measurements obtained through an incremental cut made on the plate.

scholarly journals Structural analysis of a friction stir-welded small trailer

DYNA ◽  
2015 ◽  
Vol 82 (190) ◽  
pp. 192-197
Author(s):  
Fabio Bermudez Parra ◽  
Fernando Franco Arenas ◽  
Fernando Casanova
Keyword(s):  
Friction Stir Welding ◽  
Structural Analysis ◽  
Welded Joint ◽  
Base Material ◽  
Welding Process ◽  
Field Tests ◽  
Element Model ◽  
Structural Element ◽  
Friction Stir ◽  
The Impact

This paper introduces the analysis of a trailer structure made of 6063-T5 aluminum alloy using the Friction Stir-Welding process. The base material and the welded joint were characterized by tension tests. The loads for the structural analysis were obtained from field tests where stresses were measured on critical points at a 2.73 m long 0.95 m width trailer while it was driven on an unpaved road. The stresses on the whole trailer were found by using a finite element model, where the joint with the maximum stresses was identified. This joint was constructed with a tubular structural element using Friction Stir Welding and was evaluated by bending tests. Using the impact factor obtained from the field test, fatigue analysis was performed on the welded joint. It was found that the strength of the joint was sufficient to carry the loads on the trailer.

scholarly journals Metallurgical Characterization of Welded Joint of Nanostructured Bainite: Regeneration Technique versus Post Welding Heat Treatment

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4841
Author(s):  
Aleksandra Królicka ◽  
Krzysztof Radwański ◽  
Aleksandra Janik ◽  
Paweł Kustroń ◽  
Andrzej Ambroziak
Keyword(s):  
Heat Treatment ◽  
Welded Joint ◽  
Construction Material ◽  
Weld Zone ◽  
Base Material ◽  
Welding Process ◽  
Solidification Structure ◽  
Hardness Distribution ◽  
Diffusion Type

One of the main limitations in application of nanostructured carbide-free bainite as a construction material is the difficulty of joining. This research presents a structural characterization of welded joints of medium carbon 55Si7 grade steel after the welding process with a regeneration technique as well as post welding heat treatment (PWHT). The hardness distribution of the welded joint with regeneration exhibit an overall decrease in hardness when compared to the base material and a significant decrease in hardness was observed in the heat-affected zone (HAZ). Unfavorable hardness distribution was caused by the presence of diffusion-type transformations products (pearlite) in the HAZ and bainite degradation processes. On the other hand, welding with the PWHT promotes the achievement of a comparable level of hardness and structure as in the base material. However, a slight decrease in hardness was observed in the weld zone due to the micro-segregation of the chemical composition caused by the indissoluble solidification structure. Based on the structural analysis, it was found that steel with relatively low hardenability (55Si7) should be welded using PWHT rather than a regeneration technique.

Fatigue Behaviour of Friction Stir Welded Steel Joints

2014 ◽  
Vol 891-892 ◽  
pp. 1488-1493 ◽  
Author(s):  
José Azevedo ◽  
Virgínia Infante ◽  
Luisa Quintino ◽  
Jorge dos Santos
Keyword(s):  
Base Material ◽  
Welding Process ◽  
Steel Structures ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Welded Steel ◽  
Shipbuilding Industry ◽  
Friction Stir ◽  
Steel Joints

The development and application of friction stir welding (FSW) technology in steel structures in the shipbuilding industry provide an effective tool of achieving superior joint integrity especially where reliability and damage tolerance are of major concerns. Since the shipbuilding components are inevitably subjected to dynamic or cyclic stresses in services, the fatigue properties of the friction stir welded joints must be properly evaluated to ensure the safety and longevity. This research intends to fulfill a clear knowledge gap that exists nowadays and, as such, it is dedicated to the study of welded steel shipbuilding joints in GL-A36 steel, with 4 mm thick. The fatigue resistance of base material and four plates in as-welded condition (using several different parameters, tools and pre-welding conditions) were investigated. The joints culminate globally with defect-free welds, from which tensile, microhardness, and fatigue analyses were performed. The fatigue tests were carried out with a constant amplitude loading, a stress ratio of R=0.1 and frequency between 100 and 120 Hz. The experimental results show the quality of the welding process applied to steel GL-A36 which is reflected in the mechanical properties of joints tested.

Experimental Investigations on Aluminium Ultrasonic Welding Parameters

2014 ◽  
Vol 657 ◽  
pp. 306-310
Author(s):  
Lăcrămioara Apetrei ◽  
Vasile Rață ◽  
Ruxandra Rață ◽  
Elena Raluca Bulai
Keyword(s):  
Microstructural Analysis ◽  
Base Material ◽  
Welding Process ◽  
Ultrasonic Welding ◽  
Experimental Investigations ◽  
Welding Parameters ◽  
Material Structure ◽  
Welding Temperature ◽  
Wide Range ◽  
Made In

Research evolution timely tendencies, in the nonconventional technologies field, are: manufacture conditions optimization and complex equipments design. The increasing of ultrasonic machining use, in various technologies is due to the expanding need of a wide range materials and high quality manufacture standards in many activity fields. This paper present a experimental study made in order to analyze the welded zone material structure and welding quality. The effects of aluminium ultrasonic welding parameters such as relative energy, machining time, amplitude and working force were compared through traction tests values and microstructural analysis. Microhardness tests were, also, made in five different points, two in the base material and three in the welded zone, on each welded aluminium sample. The aluminum welding experiments were made at the National Research and Development Institute for Welding and Material Testing (ISIM) Timişoara. The ultrasonic welding temperature is lower than the aluminium melting temperature, that's so our experiments reveal that the aluminium ultrasonic welding process doesn't determine the appearance of moulding structure. In the joint we have only crystalline grains deformation, phase transformation and aluminium diffusion.

scholarly journals Validation of Welding Simulations Using Thermal Strains Measured with DIC

2011 ◽  
Vol 70 ◽  
pp. 129-134 ◽  
Author(s):  
Maarten De Strycker ◽  
Pascal Lava ◽  
Wim Van Paepegem ◽  
Luc Schueremans ◽  
Dimitri Debruyne
Keyword(s):  
Residual Stresses ◽  
Cross Section ◽  
Circular Cross Section ◽  
Welding Process ◽  
Weld Bead ◽  
Image Correlation ◽  
Steel Tubes ◽  
Element Analysis ◽  
Strain Evolution ◽  
The Cross

Residual stresses can affect the performance of steel tubes in many ways and as a result their magnitude and distribution is of particular interest to many applications. Residual stresses in cold-rolled steel tubes mainly originate from the rolling of a flat plate into a circular cross section (involving plastic deformations) and the weld bead that closes the cross section (involving non-uniform heating and cooling). Focus in this contribution is on the longitudinal weld bead that closes the cross section. To reveal the residual stresses in the tubes under consideration, a finite element analysis (FEA) of the welding step in the production process is made. The FEA of the welding process is validated with the temperature evolution of the thermal simulation and the strain evolution for the mechanical part of the analysis. Several methods for measuring the strain evolution are available and in this contribution it is investigated if the Digital Image Correlation (DIC) technique can record the strain evolution during welding. It is shown that the strain evolution obtained with DIC is in agreement with that found by electrical resistance strain gauges. The results of these experimental measuring methods are compared with numerical results from a FEA of the welding process.

Influence of Friction Stir Welding Process on the Weld Formation and Tensile Strength of Titanium and Aluminum Dissimilar Alloys Welded Joint

2011 ◽  
Vol 189-193 ◽  
pp. 3266-3269 ◽  
Author(s):  
Yu Hua Chen ◽  
Peng Wei ◽  
Quan Ni ◽  
Li Ming Ke
Keyword(s):  
Tensile Strength ◽  
Friction Stir Welding ◽  
Cross Section ◽  
Welded Joint ◽  
Welding Process ◽  
Dissimilar Materials ◽  
Influence Of Process Parameters ◽  
Friction Stir ◽  
Dissimilar Alloys ◽  
Titanium Aluminum

Titanium alloy TC1 and Aluminum alloy LF6 were jointed by friction stir welding (FSW), and the influence of process parameters on formation of weld surface, cross-section morphology and tensile strength were studied. The results show that, Titanium and Aluminum dissimilar alloy is difficult to be joined by FSW, and some defects such as cracks and grooves are easy to occur. When the rotational speed of stir head(n) is 750r/min and 950r/min, the welding speed(v) is 118mm/min or 150mm/min, a good formation of weld surface can be obtained, but the bonding of titanium/aluminum interface in the cross-section of weld joint is bad when n is 750r/min which results in a low strength joint. When n is 950r/min and v is 118mm/min，the strength of the FSW joint of Titanium/Aluminum dissimilar materials is 131MPa which is the highest．

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