Beam Micro Research Articles

Sustainable approach for machining of Ti6Al4V using micro-pillar textured turning tool insert

The use of cutting fluids (CF) in metal cutting is questioned due to environmental and biological impacts, encouraging the adoption of dry machining to minimize these effects. However, dry machining accelerates tool wear, particularly in difficult-to-machine materials like Titanium and Nickel alloys. Approaches, such as rake surface texturing, address this challenge and promote sustainability in metal cutting. This study explored the impact of an innovative micro-pillar texture pattern fabricated using a combination of Laser Beam Micro Machining (LBμM) and Reverse Micro Electrical Discharge Machining (RμEDM) for the dry machining of Ti6Al4V. The investigation considers various parameters, including tool wear, contact length, titanium adhesion, cutting forces, cutting temperature, and chip morphology. An indirect approach was adopted to estimate the temperature of the tool tip using the temperature measured at a distant location. Implementing the textured tool with 15 μm deep micro-pillars in the dry machining of Ti6Al4V exhibited the best overall performance for various responses. A notable reduction of more than 40% for both tool-chip contact length and titanium adhesion, compared to a plain tool, indicated a perceptible decrease in the seizure zone at the interface. Moreover, the textured tools demonstrated a remarkable maximum reduction of 56.4% in flank wear, ensuring the prolonged retention of a sharp cutting edge. The responses for contact length, adhesion, and flank wear contributed to an 18.8% decrease in cutting force and a substantial 45.7% reduction in thrust force. Force analysis further confirmed the directional independence of the texture pattern. Under the influence of surface texturing, chip morphology changed to shorter, untangled, and tightly curled, with a 30.8% reduction in curl radius. A theoretical estimation based on the minimum energy approach was also performed to demonstrate an increment in the shear plane angle.

Focused Electron Beam Micro- and Nanopatterning of Thin Films Derived from Sol–Gels Based on TiO2 Precursors for Planar Photonics

Focused Electron Beam Micro- and Nanopatterning of Thin Films Derived from Sol–Gels Based on TiO₂ Precursors for Planar Photonics

Controlling the weld penetration depth of laser beam micro welding by using an iterative learning approach

AbstractIn order to meet the increasing demand for high‐speed joining processes, laser beam micro welding is used to reproducibly weld metallic joining partners such as steel. Long weld seams or high cycle speeds, however, remain a challenge to achieve a constant welding depth throughout the entire welding process without major fluctuations. This paper shows the development and evaluation of a weld penetration depth control system based on interferometric measurement of the depth of the vapor capillary. High path speeds and small weld depths are challenging for real‐time depth control. Therefore, the offline data of the interferometric measurements are used to implement an iterative learning control of the weld penetration depth. The quality of the control is verified by welding with and without spatial power modulation on 1.4301 steel while following a linear and sinusoidal trajectory.

Effect of TaC and graphene nanoplatelets on the microstructure and mechanical properties of ZrB2

In this experiment, in order to investigate the effect of TaC addition on the microstructure, densification and mechanical properties of ZrB2 composites reinforced with graphene nanoplatelets (GNP), three composites were fabricated via spark plasma sintering (SPS) at 1900 °C. Relative density was determined by Archimedes method. The XRD and EDS analyses were used to explore the phase composition and elemental distribution. Also, Field emission scanning electron microscopy (FE-SEM) was employed to characterize the microstructure (grain size and porosity). Flexural strength, fracture toughness and hardness were determined by three-point bending test, single-edge notched beam (SENB) and macro and micro Vickers methods, respectively. The results showed that the presence of the GNP, alone and combined with TaC, increases the relative density sharply to 99.6 %. In addition, full densification occurred by the addition of 10 and 20 vol% TaC compared to the monolithic ZrB2 ceramic with 83 % relative density. Maximum flexural strength and fracture toughness of 580 MPa and 4.5 MPa.m0.5 were obtained, respectively, for ZrB2- GNP and ZrB2- GNP doped with 10 vol% TaC.

High-Precision Adjustment of Welding Depth during Laser Micro Welding of Copper Using Superpositioned Spatial and Temporal Power Modulation

For joining metallic materials for battery applications such as copper and stainless steel, laser beam micro welding with beam sources in the near-infrared range has become established in recent years. In laser beam micro welding, spatial power modulation describes the superposition of the linear feed motion with an oscillating motion. This modulation method serves to widen the cross-section of the weld seam as well as to increase the process stability. Temporal power modulation refers to the controlled modulation of the laser power over time during the welding process. In this paper, the superposition of both temporal and spatial power modulation methods is presented, which enables a variable control of the weld penetration depth. Three weld geometries transverse to the feed direction are part of this investigation: the compensation of the weld penetration depth due to the asymmetric path movement during spatial power modulation only, a W-shaped weld profile, and a V-shaped. The weld geometries are investigated by the bed on plate weld tests with CuSn6. Furthermore, the use of combined power modulation for welding tests in butt joint configuration between CuSn6 and stainless steel 1.4301 with different material properties is investigated. The study shows the possibility of precise control of the welding depth by this methodology. Depending on the material combination, the desired regions with maximum and minimum welding depth can be achieved by the control of local and temporal power modulation on the material surface.

Dual-stage artificial neural network (ANN) model for sequential LBMM-μEDM-based micro-drilling

A sequential process combining laser beam micromachining (LBMM) and micro electro-discharge machining (μEDM) for the micro-drilling purpose was developed to incorporate both methods’ benefits. In this sequential process, a guiding hole is produced through LBMM first, followed by μEDM applied to that same hole for more fine machining. This process facilitates a more stable, efficient machining regime with faster processing (compared to pure μEDM) and a much better hole quality (compared to LBMMed holes). Studies suggest that strong correlations exist between the various input and output parameters of the sequential process. However, a mathematical model that maps and simultaneously predicts all these output parameters from the input parameters is yet to be developed. Our experimental study observed that the μEDM finishing operation’s various output parameters are influenced by the morphological condition of the LBMMed holes. Hence, an artificial neural network (ANN)-based dual-stage modeling method was developed to predict the sequential process’s outputs. The first stage of the dual-stage model was utilized to predict various LBMM process outputs from different laser input parameters. Furthermore, in the second stage, LBMM-predicted outputs (such as pilot hole entry area, exit area, recast layer, and heat-affected zone) were used for the final prediction of the sequential process outputs (i.e., machining time by μEDM, machining stability during μEDM in terms of short circuit/arcing count, and tool wear during μEDM). The model was evaluated based on the average RMSE (root mean square errors) values for the individual output parameters’ complete set data, i.e., μEDM time, short circuit/arcing count, and tool wear. The values of average RMSE for the parameters as mentioned earlier were found to be 0.1272 (87.28% accuracy), 0.1085 (89.15% accuracy), and 0.097 (90.3% accuracy), respectively.

Borate and boric acid supplementation of drinking water alters teeth and bone mineral density and composition differently in rabbits fed a high protein and energy diet

The reported beneficial effects of boron on mineralized tissues in animals and humans vary. Thus, a study was performed to assess whether the variability was the result of different forms of boron supplementation, method of supplementation, and increased adiposity of the rabbit experimental model.Thirty-one female New Zealand White rabbits, (aged 8 months, 2–2.5 kg weight) were fed a grain-based high energy diet containing 11.76 MJ/kg (2850 kcal/kg) and 3.88 mg boron/kg. The rabbits were randomly divided into four treatment groups: Control group was not supplemented with boron (n:7; C), and three groups supplemented with 30 mg boron/L in drinking water in the forms of borax decahydrate (Na2O4B7 10H2O, n:10; BD), borax anhydrous (Na2O4B7, n:7; Bah) or boric acid (H2BO3, n:7; BA). Cone beam micro computed tomographic (micro-CT), histological and elemental analysis was used to evaluate the bones/teeth.Results of the experiments demonstrated that boron supplementation had beneficial effects on mineralized tissue but varied with the type of treatment. Mineral density of the femur was increased by the Bah and BA treatments (p < 0.001), but only BA increased mineral density in the tibia (p = 0.015). In incisor teeth, mineral density of dentin was increased by all boron treatments (p < 0.001), and mineral density of enamel was increased by the BD and Bah treatments. Mineral analysis found that all boron treatments increased the boron concentration in tibia and femur. In the tibia, both the BD and Bah treatments decreased the iron concentration, and the BD treatment decreased the magnesium concentration. Sodium and zinc concentrations in the tibia were decreased by the Bah and BA treatments. The boron treatments did not significantly affect the calcium, copper, molybdenum, potassium phosphorus, and sulfur concentrations.The findings show that boron supplementation can have beneficial effects on mineralized tissues in an animal model with increased adiposity, which is a model of increased inflammatory stress. However, this effect varies with the form of boron supplemented, the method of supplementation, and the mineralized tissue examined.

Auto-calibration of cone beam geometries from arbitrary rotating markers using a vector geometry formulation of projection matrices

An efficient method for the determination of the projection geometry of cone beam micro computed tomography systems based on two or more fiducial markers of unknown position within the field of view is derived. By employing the projection matrix formalism commonly used in computer graphics, a very clear presentation of the resulting self consistent calibration problem can be given relating the sought-for matrix to observable parameters of the markers’ projections. Both an easy to implement solution procedure for both the unknown projection matrix and the marker assembly as well as the mapping from projection matrices to real space positions and orientations of source and detector relative to the rotational axis are provided. The separate treatment of the calibration problem in terms of projection matrices on the one hand and the independent transformation to a more intuitive geometry representation on the other hand proves to be very helpful with respect to the discussion of the ambiguities occurring in reference-free calibration. In particular, a link between methods based on knowledge on the sample and those based on knowledge solely on the detector geometry can be drawn. This further provides another intuitive view on the often reported difficulty in the estimation of the detector tilt towards the rotational axis. A simulation study considering 106 randomly generated cone beam imaging configurations and fiducial marker distributions within a range of typical scenarios is performed in order to assess the stability of the proposed technique. An experimental example supports the simulation results.

Effect of laser parameters on sequential laser beam micromachining and micro electro-discharge machining

Laser beam micromachining (LBMM) and micro electro-discharge machining (μEDM) based sequential micromachining technique, LBMM-μEDM, has drawn significant research attention to utilize the advantages of both methods, i.e., LBMM and μEDM. In this process, a pilot hole is machined by the LBMM, and subsequently finishing operation of the hole is carried out by the μEDM. This paper presents an experimental investigation on the stainless steel (type SS304) to observe the effects of laser input parameters (namely, laser power, scanning speed, and pulse frequency) on the performance of the finishing technique, that is, the μEDM in this case. The scope of the work is limited to 1-D machining, i.e., drilling microholes. It was found that laser input parameters mainly scanning speed and power influenced the output performance of μEDM significantly. Our study suggests that if an increased scanning speed at a lower laser power is used for the pilot hole drilling by the LBMM process, it could result in significantly slower μEDM machining time. On the contrary, if the higher laser power is used with even the highest scanning speed for the pilot hole drilling, then μEDM processing time was faster than the previous case. Similarly, μEDM time was also quicker for LBMMed pilot holes machined at low laser power and slow scanning speed. Our study confirms that LBMM-μEDM-based sequential machining technique reduces the machining time, tool wear, and instability (in terms of short circuit count) by a margin of 2.5 x, 9 x, and 40 x, respectively, in contrast to the pure μEDM process without compromising the quality of the holes.

Electrohydrodynamic emitters of ion beams

We discuss physical processes underlying the generation of ion beams with high emission current density in electrohydrodynamic (EHD) emitters based on liquid metals and alloys and with room temperature ionic liquids. We consider EHD effects that influence the emission of ions (ion production mechanisms) and the kinetics of ion interactions in high-density beams. We analyze the factors determining the emission zone size, sustainability of emission at high and low currents, generation of clusters, increase in energy spread, decrease in brightness, and other features of ion beams. We consider the specific design features of EHD emitters and the problems of practically ensuring their stable operation. Discussed in detail are modern application areas for ion sources with EHD emitters, including technological installations for ion beam lithography, micro- and nanopatterning, ion microscopes and tools for local mass spectrometry of secondary ions, and systems to control and neutralize the potential of spacecraft as well as electrostatic rocket engines (microthrusters). We analyze prospects for further development of EHD emitters themselves and instruments based on them.

A Visual Contrast–Based Fruit Fly Algorithm for Optimizing Conventional and Nonconventional Machining Processes

Swarm intelligence has been extensively adopted to develop and deploy optimization algorithms to almost all branches of science and engineering. In this paper, a visual contrast–based fruit fly algorithm (c-mFOA) is presented to push further the improvement of intelligent optimization when it comes to general engineering problem solving with emphasis to conventional and nonconventional manufacturing processes implemented to modern industry. In this fruit fly algorithmic variant, the natural mechanisms of surging, visual contrast, and casting are incorporated to enhance the algorithm’s exploration and exploitation. The proposed algorithm has been tested to optimize a set of known, widely used benchmark functions and is further implemented to optimize the process parameters of machining processes namely turning; focused ion beam micro milling; laser cutting; wire electrodischarge machining; and microwire electrodischarge machining. The results obtained by examining the multiple solutions, their nonparametric statistical outputs, and hypervolumes of their related Pareto fronts, suggest clear superiority of the c-mFOA against its competing multiobjective optimization algorithms (MOEAs).

Response of a micro-capillary system exposed to a moving mass in magnetic field using nonlocal strain gradient theory

In this study, the dynamic behaviour of the micro dimensional Timoshenko beam (micro capillary system) exposed to a moving mass in a magnetic field is modelled using the non-local strain gradient theory. The motion equations of the Timoshenko micro-beam, which interacts with the moving mass, are obtained by considering the effects of strain gradient elasticity that provides stiffening and non-local elasticity that provide softening. The transverse Lorentz force acting on the beam in the magnetic field is obtained by Maxwell's equations and combined with the motion equations of the beam. These equations are converted into a weak form finite element equation by applying the exact shape functions of the two-node Timoshenko beam element in the Galerkin's method. Along with the effects of the magnetic field, the effects of the amount of different non-local parameters and the mass ratio and speed of the moving mass on the dynamics of the micro beam are presented. Experimental and theoretical studies have shown that the dynamic behaviour of the capillary structural systems is negatively affected by the effect of moving mass except for the non-local properties. Depending on the velocity and quantity of the mass and the nonlocal elasticity, the natural frequencies of the system drop excessively. When the mass ratio (moving mass/mass of the beam) is around 0.5, the frequencies have been observed to drop by as much as 60%, and the non-local elasticity and velocity of the mass are also effective in this. It has been shown that these disadvantages can be eliminated by the effect of the force obtained using the directed magnetic field. In fact, a desired system stiffness can be obtained by adjusting the magnitude of the magnetic field at the level required by the application.

Processing of Keyhole Depth Measurement Data during Laser Beam Micro Welding

Analysing the quality of weld seams is still a challenging task. An optical inspection of the surface is giving limited information about the shape and depth of the weld seam. An application for laser beam welding with high demands regarding the weld depth consistency is the electrical contacting of battery cells. The batteries themselves have a limited terminal or case thickness that must not be penetrated during the welding process to avoid leakage or damage to the cell. That leads to a minimum weld depth to ensure the electrical functionality, and a maximum weld depth indicated by the case thickness. In such applications, a destructive analysis is not suitable which leads to the demand for a non-destructive measurement during the process. Using a coaxial, interferometric measurement setup, the keyhole depth during the deep penetration welding is measureable. For a keyhole with a depth of a couple of millimetres, such a system is commercially available. In micro scale, however, these systems are facing several challenges such as scanning systems, small spot diameters of a few tens of micrometres and narrow keyholes. This study contains an investigation of an interferometric measurement of the keyhole depth and the suitability for laser micro welding. Therefore, the data processing of the achieved measurements is investigated, and the results are compared with the depth measurement of metallographic analysed samples. Stainless steel is used to investigate the behaviour and the stability of developed data processing strategy and the resulting depth values.

Nonlinear damping in suspended beam micro- and nanoresonators due to surface loss

The nonlinear damping resulting from surface energy loss in suspended beam micro and nanoresonators is investigated theoretically. Surface energy loss is known to be a relevant and in some cases a dominant damping mechanism in micro and nanoresonators. So far, it was only investigated in the linear (low amplitude) regime. In this work we consider the beam as made of an anelastic material and introduce the beam stretching effect in the elastic model of transversally vibrating beams clamped at both ends. This model results in a nonlinear contribution to the damping. Analytical expressions for the resulting amplitude dependent quality factor and the nonlinear damping parameter in a reduced order model are derived. Large nonlinear damping is predicted when the amplitude of transversal vibration is comparable to the beam thickness, which can be relevant to the beam dynamics.

Liquid Metal Embrittlement of Copper Brazed Plate Heat Exchangers

Plate heat exchangers are widely used for heating and cooling activities in domestic and industrial applications. The plates of all these components were made of stainless steel (e.g. type X2 CrNiMo 17-12-2) and they were brazed with pure copper. After cutting and metallographic preparation, the samples were investigated by light optical microscopy (LOM) to measure the depth of copper penetration into the plates (liquid metal embrittlement (LME)). For seven heat exchangers the penetration depth was between 25 and 60 μm, but for one the depth was about 150 μm. At the steel-copper interfaces an additional phase was identified as chromium-rich ferrite by electron beam micro analysis (EBMA). To get information about the sensitivity against corrosion electrochemical tests were performed in two electrolytes (HCO3- + SO42- and HCO3- + SO42- + Cl-). It can be summarized that in the Cl- free electrolyte the copper was attacked mainly. In case of the Cl- containing electrolyte beside the copper braze, the LME zones in the steel were corroded additionally.

Prediction of robust chaos in micro and nanoresonators under two-frequency excitation.

Robust chaos in a dynamical system is characterized by the persistence of the chaotic attractor with changes in the system parameters and is generally required in practical applications based upon physical sources of chaos. However, for applications that rely upon continuous time chaotic signals, there are now very few alternatives of dynamical systems with robust chaos that could be used. In this context, it is important to find a new dynamical system and, particularly, new physical systems that present robust chaos. In this work, we show through simulations that a relevant physical system, suspended beam micro and nanoelectromechanical resonators, can present robust chaos when excited by two distinct frequencies. To demonstrate the existence of robust chaos in the system, we perform an extensive numerical analysis, showing that the attractor is unique and changes smoothly in a large region of the relevant physical parameter space. We find that the robustness of the chaotic dynamics depends crucially on the dissipation, which must be sufficiently small. When the dissipation is small, we find a large range of frequencies, frequency ratios, and applied voltages where robust chaos is observed. These findings turn these systems into viable and strong candidates for practical applications since the chaotic dynamics becomes quite insensitive to fabrication tolerances, changes in the physical parameters induced by the environment, and aging.

Laser Beam Micro Drilling – a Review

The recent advances in the manufacturing technology have led to the development of miniature products in the field of automobile, biomedical implants, biomedicine, aerospace and robotics. The literature is filled with work performed by researchers in the field of laser microdrilling. However, as of today, no exclusive review on the state of the art in laser micro drilling is reported. An attempt has been made to summarize the current state of understanding in laser micro drilling. The review begins with the classification of laser micro drilling and development of various modeling approaches. A variety of issues like identification of key process variables, selection of parameter ranges, selection of laser type and work piece combination and cause and effect diagram for various performance parameters are critically analyzed and presented. A statistical analysis of the contribution of various process parameters to the performance variable is reported. An insight into the laser micro drilling and future growth is presented in this article.

In situ investigation of production processes in a large chamber scanning electron microscope

A large-chamber scanning electron microscope (LC-SEM) provides an ideal platform for the installation of large-scale in situ experiments. Our LC-SEM has internal chamber dimensions of 1,2 × 1,3 × 1,4 m3 (W × H × D) (Fig.1) and makes it possible to incorporate novel in situ experimental devices, which are reported on here. The present manuscript describes in detail the development of in situ test equipment for the study of a broad range of processes in production engineering. Direct observation of the materials modification mechanisms provides fundamental insight into the underlying process characteristics. An in situ turning device was developed, tested and used to observe the chip formation on the microstructure scale of a 43CrMo4-sample. Laser beam micro welding was integrated into the LC-SEM to achieve in situ analysis of the welding process on stainless steel 1.4310. A heating module was employed for in situ wetting experiments to observe the formation and solidification of the melt of a tin-copper brazing filler on an aluminium cast alloy.

Effect of stereotactic radiation (SBRT) on survival in a preclinical model of spontaneous pancreatic cancer with induction gemcitabine/nab-paclitaxel.

273 Background: There are no useful preclinical models that resemble relevant fractionated radiation, such as SBRT, with relevant chemotherapy. Most preclinical studies use a single fraction of radiation to large fields, causing significant toxicity and/or insufficient dose which leads to accelerated repopulation and worsened outcomes. Here, we employ mice with spontaneous pancreatic tumors, and treat them in a preclinical trial utilizing gemcitabine/nab-paclitaxel +/-SBRT. Methods: Mice with an activated KRas (G12D) allele and heterozygous for p53 expression only in the pancreas (KPC) were created and spontaneous tumors were diagnosed via weekly palpation and ultrasound. Mice with single tumors that were between 3-7mm at diagnosis were sequentially randomized to received either no treatment, gemcitabine/nab-paclitaxel x 2 weeks, or gemcitabine/nab-paclitaxel x 2 weeks followed by 8Gy x 5 daily fractions of SBRT to the pancreatic tumor. SBRT was delivered using X-RAD 225Cx (Precision X-Ray, Inc) small animal irradiator under image guidance by cone beam micro CT using AP/PA technique with a 10mm collimator. Every mouse was subjected to necropsy and a cause of death assigned. Tumor growth was monitored by small animal ultrasound. Kaplan-Meier survival analysis was performed to assess efficacy of treatments. Results: A total of 40 mice were enrolled with 12 receiving chemotherapy alone, 13 receiving chemotherapy +SBRT and 15 mice had no further treatment. The addition of induction chemotherapy improves lifespan compared to untreated mice. The addition of SBRT further improved survival. Causes of death in untreated animals of the gemcitabine/nab-paclitaxel group were largely from local progression, whereas the addition of SBRT provided local control causing most of the mice in this cohort to die from metastatic progression. Conclusions: SBRT improves survival when added to gem/nab-paclitaxel in a preclinical model, which may reflect favorable biology for this approach. Our novel system employs similar SBRT fields and doses, and may thus be useful for the evaluation of other chemotherapeutic regimens with SBRT.

Experimental Study in Micromilling of Inconel 718 by Fiber Laser Machining

In laser beam micro machining process, the quality of the micro milled component mainly depends on appropriate selection of process parameters. In laser milling technology, the material removal is done by a laser beam through the mechanism of layer by layer ablation. The process is affected by the laser characteristics and the properties of the work material but is mostly influenced by their interaction. The selection of the laser and its parameters significantly affects surface roughness as well as the material removal rate(MRR) of the micropart. In present research, an attempt has been done to study the effect of laser process parameters on the quality of the features obtained by laser machining. In Fiber laser micro milling operation on Inconel 718, scanning speed, frequency, power have most significant effect on all responses.