Fiber Laser Processing Research Articles

Improved Adhesion Strength of Metal Textile Composites by Surface Texturing Using TIG Arc or CW Laser Process

Within the framework of the bilateral CORNET projects MeTexCom and MeTexCom2, new approaches were developed and tested to improve the adhesion strength of metal textile composites, with a focus on the targeted roughening of aluminum surfaces and the development of new acoustically insulating nonwovens. The metal textile composites were produced by melting thermoplastic components of the textile composites without a separately applied adhesive.For improved adhesion strength between metal and textile, roughness was generated on the metal surface by means of a novel arc treatment by an anodic polarized TIG process or a cw (continuous wave) fiber laser process. On the one hand, the goal was to produce uniformly rough, untercut surface structures in micro-and nanodimension by means of a highly dynamic arcing process. On the other hand, a similar approach was pursued with the cw laser method by using a single-mode as well as a multi-mode laser.

Formability enhancement of Al 6060 sheets through fiber laser heat treatment

Due to the continuous weight reduction effort in the automotive sector, formability enhancement of aluminum alloys in forming and hydroforming processes is gathering much attention from research institutes and industries. During sheet forming processes, large deformations are desired to obtain complex shapes but these are limited by the appearance of defects such as wrinkling and cracks. To avoid these issues, intermediate annealing heat treatments are often applied as a possible solution. Nevertheless in large components where small details have to be created, local heat treatment through lasers can be cost effective over the furnace treatment of the whole part and it would limit possible geometrical distortion in large components. The following article presents fiber laser process parameters definition on deformed sheets made of Al6060 alloy. Grain structure variation and hardness decrease were studied to correctly select process parameters (laser power, feeding speed and overlapping among subsequent passes) to increase material formability. In addition, a systematic comparison between fiber laser and furnace heat treatment was assessed proving the equivalence of the two methods in terms of achieved mechanical proprieties.

Development of laser beam welding of advanced high-strength steels

Advanced high-strength steels have been extensively used in automobile construction, although a more complete understanding of their weld microstructure and mechanical behavior is needed. This work aims to contribute to the understanding of these basic features as well as propose the fiber laser processing conditions. Similar and dissimilar welds of dual-phase or transformation-induced plasticity (TRIP) steels present similarities in terms of microstructure features with the presence of martensite, proeutectoid ferrite, and bainite in the fusion zone and in the heat-affected zone. However, the more important microconstituent is bainite under regular and coalesced morphologies. The tensile behavior could be considered acceptable as most of the welded coupons broke in the base material and far from the weld. Fatigue curves presented a limit at approximately 350 MPa for dual-phase steels and 450 MPa for the TRIP steel.

A comparison of microstructure and mechanical properties of welded thin Ti6Al4V with three different types of laser

Many items of medical, aeronautical, electronic and military equipment are exposed to corrosive conditions, and it is a common practice to protect these in laser beam welded titanium-alloy micro-packages, which require very small and precise weld zones. A range of laser types has been applied to this task, including Nd:YAG, diode and (more recently) fibre lasers. Compared with other laser beam welding (LBW) processes, fibre lasers are widely recognised to result in lower overall heat input, a narrower weld zone, less distortion and high process efficiency. This paper contrasts the mechanical and metallurgical properties of laser welded titanium alloy (Ti6Al4V) in the form of thin (0·7 mm) sheet, typical of that used in micro-packages. Welds were produced with three different laser types, namely, Nd:YAG, diode and fibre lasers. Despite the widely accepted advantages of fibre laser processing, weld quality following processing with a Nd:YAG laser was found to be higher than that of welds produced with either the fibre laser or diode laser; welds processed with the fibre laser exhibited serious porosity defects because of excessive laser-workpiece traverse speeds, nor large spot diameter and poor beam quality characteristic of diode lasers.

Fundamental study of CO2- and fiber laser cutting of steel plates with high speed visualization technique

Modified trim cut method with low level of invasion into the process is developed for visualization of laser cutting process. The method consists in high speed filming via transparent plate which slides with respect to the metal to allow visual access and simultaneously serves as the second missing wall of the kerf. The method is suitable for visualization in conditions equivalent to industrial cutting process in a wide range of plate thicknesses. High speed recordings are done for cutting of mild steel with oxygen and stainless steel with nitrogen. The effect of radiation wave length on the surface quality is studied by comparison of CO2 and fiber laser processing. The obtained results suggest that in case of oxygen assisted cutting, the combustion effects dominate on the surface quality and the effect of the radiation wavelength is moderate. In contrast, inert-gas-assisted cutting visualization reveals very high sensitivity to hydrodynamics of the melt flow which is strongly dependent on the radiation wavelength.

A study on fiber laser lap welding of thin stainless steel

This study analyzed variations of shear strength that depend on the fiber laser process during lap welding of AISI 304 stainless thin sheets. The experimental plan was based on a Taguchi orthogonal array table. A hybrid method that includes the response surface methodology (RSM) and back-propagation neural network (BPNN) integrated genetic algorithm (GA) are proposed to search for an optimal parameter setting of the lap welding process. The results show that the RSM and BPNN/GA methods are both effective tools for the optimization of lap welding process parameters. At the same time, an analysis of variance (ANOVA) was implemented to identify significant factors influencing the lap welding process parameters. In addition, the micrographs also show that the appropriate setting of the laser power, befitting the penetration depth and welding line length of the fusion zone sections were produced. A confirmation experiment was also conducted in order to validate the optimal welding process parameter values.

A study on fiber laser micro-spot welding of thin stainless steel using response surface methodology and simulated annealing approach

This study analyzed variations of shear strength that depend on the fiber laser process during micro-spot welding of AISI 304 stainless thin sheets. A preliminary study used ANSYS results to obtain initial process conditions. The experimental plan was based on a Taguchi orthogonal array table. A hybrid method that includes the response surface methodology (RSM)- and back propagation neural network (BPNN)- integrated simulated annealing algorithm (SAA) is proposed to search for an optimal parameter setting of the micro-spot welding process. In addition, an analysis of variance was implemented to identify significant factors influencing the micro-spot welding process parameters, which was also used to compare the results of BPNN-integrated SAA with the RSM approach. The results show that the RSM and BPNN/SAA methods are both effective tools for the optimization of micro-spot welding process parameters. A confirmation experiment was also conducted in order to validate the optimal welding process parameter values.

Structure characterisation and mechanical properties of crystalline alumina coatings on stainless steel fabricated via sol–gel technology and fibre laser processing

Abstract The surface modification of stainless steel by coating with alumina (Al 2 O 3 ) was carried out using sol–gel coating technology in combination with laser processing. Alumina coatings have been synthesised via a sol–gel route and deposited on stainless steel substrates by dip coating. The coated substrates were then treated with pulsed ytterbium fibre laser radiation ( λ = 1064 nm) in continuous wave mode with different specific energies. The composition and structure of the coated surfaces after laser processing were characterised by ATR-FTIR, XRD, SEM and contact angle measurements, whilst the mechanical properties of modified surfaces were determined using nano-indentation. The results showed that the alumina xerogel films coated on the substrates are successfully converted into crystalline alumina ceramic coatings by the laser irradiation, the structure of resulting coatings being dependent on the irradiation conditions, with increase of laser specific energy leading to the formation of initially γ-Al 2 O 3 with increasing amounts of α-Al 2 O 3 at higher energy. Nano-indentation results reveal that the laser processing results in significant improvement in hardness and Young's modulus of the alumina-coated surface and, at optimum, can achieve the mechanical properties at the same level as pure α-alumina ceramic, much higher than those of the as-dried xerogel coating.

Coloration of Stainless Steel Utilizing Fiber Laser Oxidation

This paper presents a novel technique for coloring stainless steel utilizing a fiber laser. This study develops a processing technology that uses a fiber laser as a laser marking tool, and varies processing parameters such as pre-surface-processing conditions, stainless steel type, line distance, laser power, engraving speed, and laser pulse frequencies to achieve different results. This study investigates the results of the stainless workpiece coloring using optical microscope (OM). This study shows that polished stainless steel 316 exhibits the best engraving effect. With this material, the line distance, laser power, engraving speed, and pulse frequency of the laser change the oxidation thickness. The color of the processed workpiece also changes as the oxidation thickness changes due to the interference caused by the different thicknesses of the oxidation layers. Results prove that fiber laser processing of stainless steel is a promising and efficient technique for coloring stainless steel.

Mathematical modelling of the fibre laser surface processing of a zirconia engineering ceramic by means of three-dimensional finite-element analysis

The thermal effects of fibre laser surface treatment on a ZrO2 engineering ceramic were studied using a computational finite-element model (FEM). Temperature increases on the surface and the bulk of the ZrO2 during the fibre laser processing were measured using an infra-red thermometer and specifically located thermocouples. The results showed an error of 5 per cent with the surface and 18 per cent within the bulk of the ZrO2 when comparing the experimental readings with those of the FEM. The FEM revealed a relationship between the traverse speed, power density, time, depth, and the temperature during various stages of the fibre laser surface treatment of the ZrO2. By utilizing data obtained from a thermogravimetry-differential scanning calorimetry (TG-DSC), the FEM predictions of the temperature distribution were used to map phase transformations and significant events occurring during the fibre laser surface treatment of the ZrO2. The mapping revealed that the fibre laser surface treatment generally resulted in a phase transformation of the ZrO2 at various temperatures changes as further shown in the article.

Examination of temperature distribution and the thermal effects on Si 3N 4 engineering ceramics during fibre laser surface treatment

The thermal effects of fibre laser surface treatment on a Si 3N 4 engineering ceramic were studied using a computational finite element analysis (FEA). Temperature increases on the surface of the Si 3N 4 during fibre laser processing were measured using an infra-red thermometer; temperature distributions in the bulk were measured with specifically located thermocouples. A computational model by using FEA was then developed to model the flow and the distribution of the radiated heat resulting from the fibre laser treatment of the Si 3N 4 ceramic. By utilising data obtained from a TG-DSC analysis the FEA model predictions of the temperature distribution were used to map phase transformations and significant events occurring during the fibre laser surface treatment of the Si 3N 4. The TG-DSC analysis also indicated that the fibre laser surface treatment generally resulted in a phase transformation of the Si 3N 4 from α-phase to β-phase modification as elongated rod-like grains were found.

ファイバレーザによる 3 次元加工とマイクロシステムの構築

ファイバレーザによる 3 次元加工とマイクロシステムの構築

基于ABB机器人光纤激光加工系统的研究

基于ABB机器人光纤激光加工系统的研究

Preface to Special Issue on Present and Future of Fiber Laser Processing

Preface to Special Issue on Present and Future of Fiber Laser Processing