Fatigue Strength and Damage Mechanisms of Laser Welded Structural Carbon Steel Sheets

2015 ◽  
Vol 662 ◽  
pp. 201-204 ◽  
Author(s):  
Ivo Černý ◽  
Jiří Sís
Keyword(s):  
Laser Welding ◽  
Fatigue Resistance ◽  
Fatigue Tests ◽  
Basic Material ◽  
Welding Parameters ◽  
Damage Mechanisms ◽  
Steel Sheets ◽  
Welding Processes ◽  
Structural Carbon ◽  
Structural Carbon Steel

Laser welding is one of advanced and promising joining technologies of metallic materials, characteristic by numerous advantages in comparison with conventional welding processes. The technology still can be considered as fairly new and so, investigations are needed to reach optimum properties of welds in specific application cases, depending on welding parameters. Certification welding procedures usually require to demonstrate sufficient microstructure, mechanical, impact loading and other characteristics, but not fatigue resistance, which is essential for welded dynamically loaded structures. The paper contains results of fatigue resistance investigation of laser welded 10 mm thick sheets of a carbon structural S 355 steel. High cycle fatigue tests were performed after optimizing laser welding parameters. Resulting endurance limit of the welds and heat affected zone was higher than that of basic material. However, high scatter of results and different damage mechanisms were shown for different load amplitudes. The results are discussed on the basis of fractographical analyses, which provided some quite interesting details about crack initiation mechanisms.

Fatigue Resistance of Laser Welded S355 Steel Sheet

2015 ◽  
Vol 665 ◽  
pp. 69-72 ◽  
Author(s):  
Ivo Černý ◽  
Jiří Sís ◽  
Pavel Zháňal
Keyword(s):  
Fatigue Resistance ◽  
Steel Sheet ◽  
High Cycle Fatigue ◽  
Endurance Limit ◽  
Fatigue Tests ◽  
Basic Material ◽  
Welding Parameters ◽  
Laser Weld ◽  
Cycle Fatigue ◽  
Self Consistent

The paper contains results of fatigue resistance investigation of laser welded 10 mm thick sheets of a carbon structural S355 steel. High cycle fatigue tests were performed to verify fatigue strength of the sheet containing laser weld performed with optimised laser welding parameters. Though the thickness of the sheet was quite big, resulting endurance limit of the welds and heat affected zone was comparable with that of basic material. In addition, some characteristics of the laser weld like hardness were very self-consistent. As expected, fatigue results were characteristic by quite high scatter. Different damage mechanisms were shown. The results are discussed on the basis of fractographical analyses, which provided some quite interesting details about crack initiation mechanisms.

Analysis of Welds Made by Delta Spot Method

2015 ◽  
Vol 818 ◽  
pp. 229-232
Author(s):  
Ján Viňáš ◽  
Luboš Kaščák
Keyword(s):  
Spot Welding ◽  
Welded Joint ◽  
Galvanized Steel ◽  
Metallographic Analysis ◽  
Welding Parameters ◽  
Resistance Spot ◽  
Steel Sheets ◽  
Resistance Spot Welds ◽  
Welding Processes

Resistance spot welding has been widely used in sheet fabrication for several decades. Development of new materials leads to innovation of welding processes. The paper describes the principle of innovative welding method known as Delta Spot and evaluates the properties of Delta Spot joints made by combination of galvanized steel sheets H220PD (a0 = 0.9 mm) and TRIP 40/70+Z100MBO (a0 = 0.77 mm). The quality of welded joints was evaluated by tensile test and metallographic analysis. The influence of the welding parameters on the structure of welded joint was observed too. The properties of Delta Spot joint were compared to the properties of standard resistance spot welds.

scholarly journals A State-of-the-Art Review of Laser Welding of Polymers - Part I: Welding Parameters

2021 ◽  
Vol 100 (7) ◽  
pp. 221-228
Author(s):  
Nitesh Kumar ◽  
◽  
Nikhil Kumar ◽  
Asish Bandyopadhyay
Keyword(s):  
Laser Welding ◽  
Morphological Characteristics ◽  
Scanning Speed ◽  
Processing Parameters ◽  
Welding Parameters ◽  
High Durability ◽  
Transmission Laser Welding ◽  
Automotive Parts ◽  
Important Field ◽  
Welding Processes

Polymers are widely used in automotive parts and fields like mechatronics and biomedical engineering because of their excellent properties, such as high durability and light weight. Welding of polymers has grown to be an important field of research due to its relevance among products of everyday life. Through transmission laser welding (TTLW) has been frequently selected by the contemporary re-searchers in the field of welding as it is relatively modern and more efficient than other welding processes. This pa-per reviews the influence of different processing parameters, including laser power, scanning speed, standoff distance, and clamping pressure. The present article is expected to provide the reader with a comprehensive under-standing of TTLW and research on the aforementioned four welding parameters in TTLW. The significance of finite element modeling, a few simulation studies, different optimization approaches, morphological characteristics, and other behaviors of laser welded polymers will be included in the next part of the review.

An Effect of Surface Laser Hardening on Deformations and Fatigue Properties of 42CrMo4 Steel Specimens

2013 ◽  
Vol 486 ◽  
pp. 54-57
Author(s):  
Ivo Černý ◽  
Jiří Sís
Keyword(s):  
Residual Stresses ◽  
Laser Treatment ◽  
Fatigue Resistance ◽  
Industrial Applications ◽  
Fatigue Tests ◽  
Laser Hardening ◽  
Small Samples ◽  
Fatigue Properties ◽  
Basic Material ◽  
Subsurface Layers

Laser hardening is an advanced method of surface heat treatment with wide possibilities of industrial applications. Considering the fact that this technology is fairly new and is being developed, knowledge about effects on properties of materials treated by this technology are still limited, particularly from the viewpoint of mechanical and particularly fatigue properties. As a dependence of numerous parameters of the treatment, basic material and its state and also size of treated pieces or specimens, not only substantial changes of microstructure in the surface and subsurface layers occur, but also residual stresses and connected deformations. Results of an experimental investigation of effects of laser treatment with selected parameters on deformations and fatigue resistance of relatively small samples of 8 x 8 mm cross section are presented and discussed in this work. Effects of surface speed of the laser beam was evaluated, then effects of fixation of the specimens to rigid supporting steel plate on changes of deflection caused by the laser treatment and eventually, changes of the deformations after releasing the specimens from the supporting plate. Results are in a good agreement with residual stress measurements. Fatigue tests indicated possibilities of favourable effects of laser treatment on fatigue resistance. Results are discussed considering an occurrence of inclusions in the material, residual stresses and fatigue damage mechanisms.

scholarly journals NUMERICAL STUDY OF THE TEMPERATURE FIELD FOR Fe3Al LASER WELDING

2021 ◽  
Vol 55 (3) ◽  
Author(s):  
Josef Bradáč ◽  
Jiří Hozman ◽  
Jan Lamač
Keyword(s):  
Temperature Field ◽  
Laser Welding ◽  
Numerical Scheme ◽  
Numerical Study ◽  
Welding Process ◽  
Beam Power ◽  
Welding Parameters ◽  
Original Experiment ◽  
Butt Weld ◽  
Welding Processes

The main objective of this paper was focused on a numerical study related to a proper evaluation of the temperature field during the laser-welding process. The investigated material used for the experiments was Fe3Al, given its properties and promising application potential. The original experiment was based on a 3D model of a butt weld. However, to reduce the computational complexity, a planar variant of the heat-transfer equation with suitable choices of surface and volumetric heat sources, given by modified Gaussian pulses, is used to model the temperature distribution in the fixed cross cut during the laser welding. Subsequently, the numerical scheme based on the discontinuous Galerkin method was employed to evaluate the temperature field more properly and to identify the main characteristics of the molten zone. Finally, the numerical study was performed for various combinations of the welding parameters, such as laser-beam power and welding speed. The obtained results were in good agreement with the expected behavior, and thus illustrate the optimization potential of the proposed numerical scheme in the similar issues of a laser-welding processes.

scholarly journals MECHANICAL AND OPTICAL INVESTIGATION OF LASER WELDED STRUCTURAL STEEL - POLY(METHYL-METHACRYLATE) HYBRID JOINT STRUCTURES

2019 ◽  
Vol 25 ◽  
pp. 12-16
Author(s):  
Tamás Csizér ◽  
Tamás Temesi ◽  
László Molnár
Keyword(s):  
Laser Welding ◽  
Methyl Methacrylate ◽  
Welding Parameters ◽  
Optical Investigation ◽  
Poly Methyl Methacrylate ◽  
Friction Stir ◽  
Hybrid Joint ◽  
Polymer Hybrid ◽  
Welded Seam ◽  
Welding Processes

Modern welding processes that can easily be automated (such as friction stir welding, laser welding and ultrasonic welding) are gaining popularity in joining metal-polymer hybrid structures. This field of science is intensively studied around the globe, as a dependable, productive joining method that directly produces structurally sound joints between a metal and a polymer structure could unleash unforeseen possibilities in the vehicle industry. In our experiments, we manufactured hybrid steel-poly(methyl-methacrylate) (PMMA) joints with laser welding, using the 2p design of experiment method. We measured the effect of cellulose reinforcing fibres (in varying weight percentages) on the transparency and weldability of the PMMA material and the effect of welding parameters on the mechanical properties of the joints. We also examined the vicinity of the welded seam with scanning electron microscopy.

Evaluation of Fatigue Strength of Heat Treated and Laser Hardened 42CrMo4 Steel Considering Localized Initiation Mechanisms

2014 ◽  
Vol 606 ◽  
pp. 31-34
Author(s):  
Ivo Černý ◽  
Jiří Sís ◽  
Dagmar Mikulová
Keyword(s):  
Fatigue Strength ◽  
Residual Stresses ◽  
Fatigue Resistance ◽  
Fatigue Crack Initiation ◽  
Industrial Applications ◽  
Fatigue Tests ◽  
Laser Hardening ◽  
Basic Material ◽  
Heat Treated ◽  
42Crmo4 Steel

Laser surface hardening is an advanced method of surface treatment of structural steels with a great potential for wide industrial applications. According to the recent literature results and knowledge about laser hardening, fatigue resistance can be either reduced or increased, even considerably, depending on numerous parameters of basic material, the technology parameters etc. This contribution contains results of a partial study of effect of laser hardening of relatively small specimens on fatigue resistance of 42CrMo4 steel. Two different parameters of laser hardening were used, one of them resulted in considerable longitudinal residual stresses surface speed of laser beam 4 mm/s. Results of fatigue tests of basic reference material had a surprisingly high, atypical scatter, particularly in the region near fatigue limit. Fractographical analyses indicated that this scatter was connected with presence of single inclusions, even quite large, which in some cases caused fatigue crack initiation. Compressive residual stresses after the laser treatment improved fatigue strength and reduced the scatter, likely due to short crack retardation in the compressive residuals tress field. Further analyses and discussion are provided using Murakami method of fatigue life evaluation of materials containing defects.

Laser Welding of High-Strength CP Steels: Dissimilar Welds

2015 ◽  
Vol 647 ◽  
pp. 141-146 ◽  
Author(s):  
Jan Kašpar ◽  
Stanislav Němeček
Keyword(s):  
Mechanical Properties ◽  
Laser Welding ◽  
Fatigue Cracks ◽  
High Strength ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Welding Parameters ◽  
Dissimilar Weld ◽  
Tension Tests ◽  
Dissimilar Welds

The paper explores laser welding of high-strength CP-W® 800 steel and forged steel. Dissimilar welds were produced with different welding parameters. Two welding beam diameters were used. The microstructure and mechanical properties of the resulting welds were examined. Metallographic sections were prepared and microhardness and tension tests were carried out. Fatigue tests were conducted on the weld specimens to map the effects of welding parameters on the fatigue behaviour of the dissimilar weld between the CP steel and the forged steel. Greater amount of heat input impairs the strength of the joint but improves its resistance to initiation of fatigue cracks.

Effect of Laser Welding Parameters of DUPLEX 2205 Steel Welds on Fatigue Life

2014 ◽  
Vol 223 ◽  
pp. 11-18 ◽  
Author(s):  
Robert Sołtysiak
Keyword(s):  
Fatigue Life ◽  
Laser Welding ◽  
Welded Joints ◽  
Fatigue Tests ◽  
Parent Material ◽  
Welding Parameters ◽  
Test Results ◽  
Optimum Parameters ◽  
Steel Welds

This paper presents the results of the fatigue tests carried out on laser welded joints of DUPLEX 2205 steel (X2CrNiMoN22-5-3 according to PN-EN 10027-1:2007). The butt-welded joints were made using an Nd-YAG disk laser with no filler for two different welding parameters. The parameters were selected based on previous tests (according to PN-EN ISO 15614-11: 2005) conducted for joints made with more than ten welding parameters.The tests carried out provided a basis for the determination of optimum parameters for laser welding of DUPLEX 2205 steel in terms of fatigue life. Additionally, the fatigue test results were related to the fatigue life of samples taken from the parent material.

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