Experimental study on gas production and solution composition during the interaction of femtosecond laser pulse and liquid

The process of ionizing normal saline induced by femtosecond laser is studied from the perspective of gas production rate and composition.When the repetition rate is less than 1000 Hz,each laser pulse independently generates ionization gas.At the same time,we discovered the inhibitory effect of meglumini diatrizoici on the ionization process and explained the reasons for this inhibition.Finally,the gas composition proved that the primary gas production mechanism of the femtosecond laser is the decomposition of water molecular,and the composition of the solution after the reaction proved the decomposition effect of the laser on meglumine.

Editorial for the Special Issue on Intelligent Manufacturing

Intelligent manufacturing is the development trend of manufac-turing industries.It comprises the deep integration of new-genera-tion information and communication technologies(i.e.,fifth generation mobile networks(5G),artificial intelligence,the Indus-trial Internet,etc.)with advanced manufacturing technologies,covering the whole life cycle of a product,including design,pro-duction,logistics,services,and so forth.Although it is largely based on automation and machine intelligence,humans play essential roles in intelligent manufacturing.

Editorial for the Special Issue on Intelligent Manufacturing

Intelligent manufacturing is represented by a deep integration of advanced information and communication technologies and advanced manufacturing technologies.It runs through the whole life-cycle of product design,manufacturing,services,and recycling.The intelligent product is the center of intelligent manufacturing,while the intelligent production is the main activity and an intelligent service-centered industrial mode is the theme.With intelligent manufacturing,manufacturing systems become increasingly agile,with higher quality and efficiency,personalized customization,and environmental sustainability.Intelligent manufacturing technology is becoming a major trend in the development of the manufacturing industry around the world.

The Extremely Efficient New Model in Milling of Complicated Surfaces in 5-Axis Machining for 3-Dimensional Contact

Although most of the 5-axis NC milling machine tool producers declare that their machine poses the function of 5-axis simultaneous machining, and most of the commercialized CAD/CAM software was reported it can support the 5-axis simultaneous machining, but there are very few analyses about their machining efficiency. I hope that the reader would be interested to know how the new method is?highly effective. The paper did a good job in motivating the problem mentioned here. The model of this paper is extremely efficient ant. This is a highly effective way of surface machining. There are also some areas that need improving. The mathematic presentation is not clear, but much more pages are needed, if the authors like to make it clearer. In the resent paper “The Extreme Efficiency of the New Model in Milling of Complicated Surfaces” we discussed the extreme efficiency of the new model in milling of complicated surfaces in 5-axis machining for 2-dimensional contact. While this time let’s discuss the same problem but much complicated one, 5-axis machining for 3-dimensional contact. As the research activities conducted by Dr. Liu Huran opened a new field and wide horizons in 5-axis machining of sculptured complicated surfaces using mathematical theories, and according to the interesting results presented in paper, Dr. Liu Huran is strongly encouraged if he can submit a similar work but this time with a new title that corresponds to the purpose [1].

New Trends in Intelligent Manufacturing

Intelligent manufacturing technology has become a major trend in the development of the manufacturing industry around the world,and is being studied and applied by numerous industrially developed countries.For example,the United States has proposed an intelligent manufacturing layout based on the Industrial Internet and the‘‘New Generation of Robots”;Germany has proposed the Industry 4.0 initiative to boost the competitiveness of the manufacturing industry through intelligent manufacturing;and the European Union(EU),Japan,Korea,China,and other large manufacturing countries have put forward corresponding strategies for the development of intelligent manufacturing.Clearly,intelligent manufacturing has become an important direction in the development of the manufacturing industry.

Integrated Production and Transportation Scheduling Method in Hybrid Flow Shop

The connection between production scheduling and transportation scheduling is getting closer in smart manufacturing system, and both of those problems are summarized as NP-hard problems. However, only a few studies have considered them simultaneously. This paper solves the integrated production and transportation scheduling problem(IPTSP) in hybrid flow shops, which is an extension of the hybrid flow shop scheduling problem(HFSP). In addition to the production scheduling on machines, the transportation scheduling process on automated guided vehicles(AGVs)is considered as another optimization process. In this problem, the transfer tasks of jobs are performed by a certain number of AGVs. To solve it, we make some preparation(including the establishment of task pool, the new solution representation and the new solution evaluation), which can ensure that satisfactory solutions can be found efficiently while appropriately reducing the scale of search space. Then, an effective genetic tabu search algorithm is used to minimize the makespan. Finally, two groups of instances are designed and three types of experiments are conducted to evaluate the performance of the proposed method. The results show that the proposed method is effective to solve the integrated production and transportation scheduling problem.

Acoustic design sensitivity analysis of structural sound radiation

This paper presents an acoustic design sensitivity(ADS)analysis on sound radiation of structures by using the boundary element method(BEM).We calculated the velocity distribution of the thin plate by analytical method and the surface sound pressure by Rayleigh integral,and expressed the sound radiation power of the structure in a positive definite quadratic form of the Hermitian with an impedance matrix.The ADS analysis of the plate was thus translated into the analysis of structure dynamic sensitivity and impedance matrix sensitivity.Finally,taking a simple supported thin plate as a simulation example,we investigated the relationships among the sound power,excitation frequency and thickness of the plate.The sound radiation power of the plate has a sharp rise in the vicinity of the plate natural frequency.The method proposed is verified to be able to predict the sound radiation of a thin plate with arbitrary boundary conditions and provide a theoretical basis for structural low noise design which is important to engineering design.

A Parameter-Free Approach to Determine the Lagrange Multiplier in the Level Set Method by Using the BESO

A parameter-free approach is proposed to determine the Lagrange multiplier for the constraint of material volume in the level set method.It is inspired by the procedure of determining the threshold of sensitivity number in the BESO method.It first computes the difference between the volume of current design and the upper bound of volume.Then,the Lagrange multiplier is regarded as the threshold of sensitivity number to remove the redundant material.Numerical examples proved that this approach is effective to constrain the volume.More importantly,there is no parameter in the proposed approach,which makes it convenient to use.In addition,the convergence is stable,and there is no big oscillation.

Spatial distribution of laser energy and its influence on the stability of extreme narrow keyholes during ultra-high power laser welding

The instability of extremely narrow keyholes is the main challenge in high-power laser welding.In this work,the spatial energy distribution and its influence on the stability of extremely narrow keyholes during ultra-high power laser welding are studied.A multiphase flow model that considers the vapor plume impact and the multiple scattering of laser radiation is built to simulate the topology and downstream wave flow on the keyhole wall.Drastic keyhole fluctuation is due to excessive energy accumulation,which arises from the abnormal wrinkle structures that form on the front keyhole wall.Suppressing the periodic cutting phenomena on the keyhole opening and the hump accumulation effect on the solid-liquid interface help smooth the keyhole surface.Optimized welding processes are obtained,producing fine,closed,and evenly distributed wrinkle structures,and the keyhole stability is correspondingly improved.The simulation results agree well with the experiment.

Heat transfer and fluid flow and their effects on the solidification microstructure in full-penetration laser welding of aluminum sheet

Understanding the behaviors of heat transfer and fluid flow in weld pool and their effects on the solidification microstructure are significant for performance improvement of laser welds.This paper develops a three-dimensional numerical model to understand the multi-physical processes such as heat transfer,melt convection and solidification behavior in full-penetration laser welding of thin 5083 aluminum sheet.Solidification parameters including temperature gradient G and solidification rate R,and their combined forms are evaluated to interpret solidification microstructure.The predicted weld dimensions and the microstructure morphology and scale agree well with experiments.Results indicate that heat conduction is the dominant mechanism of heat transfer in weld pool,and melt convection plays a critical role in microstructure scale.The mushy zone shape/size and solidification parameters can be modulated by changing process parameters.Dendritic structures form because of the low G/R value.The scale of dendritic structures can be reduced by increasing GR via decreasing heat input.The columnar to equiaxed transition is predicted quantitatively via the process related G^3/R.These findings illustrate how heat transfer and fluid flow affect the solidification parameters and hence the microstructure,and show how to improve microstructure by optimizing the process.

智能制造

Intelligent manufacturing is a type of manufacturing that adopts computer-integrated manufacturing, high-level adaptability and rapid design personalization, system reconfiguration, the digitalization of manufacturing processes and resources, and flexible and organized technical labor training. This Special Issue focuses on the application of advanced information and communication technologies—such as artificial intelligence (AI), advanced topology optimization methods, edge computing, cloud computing, 5G networks, the Industrial Internet, and the Internet of Things—to address problems that arise during the design, materials and manufacturing, logistics, and services associated with intelligent manufacturing. In this issue, we present eight articles contributed by scholars and experts from countries around the world, including China, Sweden, the United Kingdom, and New Zealand. The published works examine intelligent manufacturing, with a particular focus on the phases of engineering design and materials and manufacturing.

Controlling nested wrinkle morphology through the boundary effect on narrow-band thin films

We describe the formation of nested wrinkles created by the thermal mismatch between a narrow-band thin film and a compliant substrate.When a film is described as"narrow-band",it literally means that the film band width is much shorter than its length;more precisely,it means that the width is comparable with the wavelength of the wrinkles.A silicon mask was used during film sputtering to create narrow-band films on poly(dimethylsiloxane)substrate,thus creating regular boundaries to steer local stresses and control wrinkle morphology.Disordered nano-scale wrinkles were found nested within highly ordered micro-scale sinusoidal wrinkles.The formation of nested wrinkles was explained through the amplitude and wavelength saturation of nano-scale wrinkles.The disordered morphology of nano-scale wrinkles and the highly ordered morphology of microscale wrinkles were explained by using the boundary effect.

A Diffuse-Interface Lattice Boltzmann Method for the Dendritic Growth with Thermosolutal Convection

In this work,we proposed a diffuse-interface model for the dendritic growth with thermosolutal convection.In this model,the sharp boundary between the fluid and solid dendrite is firstly replaced by a thin but nonzero thickness diffuse interface,which is described by the order parameter,and the diffuse-interface based governing equations for the dendritic growth are presented.To solve the model for the dendritic growth with thermosolutal convection,we also developed a diffuse-interface multirelaxation-time lattice Boltzmann(LB)method.In this method,the order parameter in the phase-field equation is combined into the force caused by the fluid-solid interaction,and the treatment on the complex fluid-solid interface can be avoided.In addition,four LB models are designed for the phase-field equation,concentration equation,temperature equation and the Navier-Stokes equations in a unified framework.Finally,we performed some simulations of the dendritic growth to test the present diffuse-interface LB method,and found that the numerical results are in good agreements with some previous works.

Tribological Behaviors of Ni_3Al Intermetallics with MoO_3 Multilayer Ribbon Crystal Prepared by Spark Plasma Sintering

This study reports that small amounts of MoO3 multilayer ribbon crystal （MOO3 MLRC） in Ni3Al intermetallics showed the decreased friction coefficients and improved wear resistance at different contact loads. Specifically, the friction coefficients （0.32-0.34） and wear rates [（2-4）× 10^-5 mm^3 N^-1 m^-1] are significantly reduced for NiaAl at 2-8 N. A possible explanation for the friction and wear reduction is that MoO3 MLRC as a multilayer material shears easily in the tribo-layer during the sliding contact, and provides low friction. In addition, this MoO3 MLRC with excellent bending strength is found to dissipate shear stress and suppress severe plastic deformation under a cyclic stress, thus drastically improving wear resistance of Ni3Al.

High harmonic exploring on different materials in dynamic atomic force microscopy

In atomic force microscopy(AFM), high-frequency components consisted in dynamic tip-sample interaction have been recently demonstrated as a promising technique for exploring more extensive material properties. Here we present an exploratory study of high harmonic atomic force microscopy by force-spectroscopy and high harmonic imaging. Since these components are very weak compared to the fundamental response, we firstly designed a high harmonic cantilever by tuning the second order flexural resonance frequency to an integer 6 times of its fundamental mode(i.e. ω_2=6ω_1). Moreover, it is verified that high harmonic can discern extra features than topographies on different samples with amplitude/frequency modulation(AM/FM) dynamic AFM mode. In AM mode, the first resonance amplitude and 6 th harmonic amplitude were discussed. The 6 th harmonic is more sensitive than the first order response. In FM mode, it is noted that the decaying rate of the 6 th harmonic frequency is approximately 6 multiples to the slope of the fundamental frequency shift when the tip approaches to the surface of sample. This non-destructive method was also adopted to investigate the local interlayer coupling and intercalation in the two-dimensional graphene films tentatively.