Search results

This paper aims to discuss the combination of electrospinning and melt blowing in theory, which may be a good way to produce nanofibers.

In this paper, the electrostatic field and the air flow field were numerical simulated and analyzed, the compound field of which was also discussed.

It is pointed out that the air flow angle will be a key factor to produce nanofibers in the compound process of electrospinning and melt blowing.

The combination of electrostatic force and air drawing force may be a good way to produce nanofibers when the material is high viscosity melt. Air jets with high temperature and high velocity will provide favorable conditions for attenuating the polymer jet. The flow angle of the air jets effect the whole attenuation force exerted to the polymer jet and should be selected properly.

This paper presents a study on implementing design of experiments for optimizing the extrusion blow molding process. The effect of screw speed, melting temperature, cooling time, pressure, mold temperature, and ambient temperatures on the outcome of the process is investigated. The significant factors affecting the volume and mass of the blow molded bottles are identified. The results show that melting temperature, pressure, and ambient temperature have a significant impact on the variation of produced bottle quality. An optimization technique is implemented to identify the best operating conditions to meet the required product output.

Recently, the usage of melt blown products in many areas has increased. In melt blown process, generally polymers have been used. There are a variety of polymers. Characteristics of melt blown nonwovens have changed significantly depending on the polymer type. Also, there are several parameters such as die temperature, die-to-collector distance (DCD), air pressure, etc. that modify the nonwovens in melt blown process. The purpose of this paper is to investigate the effect of these parameters on the characteristics of nonwovens made up of polyethylene (PE).

In the melt blown process, two die temperatures, three different die air pressures and three different DCDs were used. In total, 18 samples were produced. On produced samples, thickness, tear and tensile strengths, fiber diameter, basis weight tests were done. Also SEM observations were obtained.

It was observed that parameters studied have a significant effect on characteristics of the produced nonwoven. Fiber diameter, basis weight and strength decrease by depending on factors. Also, it was observed that temperature has an effect, but slight. This work shows that higher temperatures should be studied. Finer and uniform fiber diameter is obtained with an increase in air pressure.

PE is becoming increasingly important in nonwovens due to its lower melting point for processing and softer feel in nonwoven products.

Although the use of PE in polymer-laid nonwovens, especially as bicomponent fibers, has been growing in recent years, there are limited data on their processability and performance. In this context, with the availability of relatively higher melt flow rate PE, understanding the processability and structure and properties of the melt blown PE is very helpful in designing and developing the right products. This research was conducted to evaluate the processability of the PE resin using a typical PP melt blowing pilot line and to determine the structure and properties of the formed webs.

PE has superior properties such as excellent chemical resistance, good fatigue, wear resistance and higher impact strength. Also, PE provides good resistance to organic solvents, degreasing agents and electrolytic attack. PE has lower working temperatures than polypropylene, is light in weight, resistant to staining and has low moisture absorption rates. Thus, this study provides important contributions to the area since there are no data reported about the effect of various processing parameters on the structure and properties of PE melt blown nonwovens.

This paper aims to address the numerical simulation of additive manufacturing (AM) processes. The numerical results are compared with the experimental campaign carried out at State Key Laboratory of Solidification Processing laboratories, where a laser solid forming machine, also referred to as laser engineered net shaping, is used to fabricate metal parts directly from computer-aided design models. Ti-6Al-4V metal powder is injected into the molten pool created by a focused, high-energy laser beam and a layer of added material is sinterized according to the laser scanning pattern specified by the user.

The numerical model adopts an apropos finite element (FE) activation technology, which reproduces the same scanning pattern set for the numerical control system of the AM machine. This consists of a complex sequence of polylines, used to define the contour of the component, and hatches patterns to fill the inner section. The full sequence is given through the common layer interface format, a standard format for different manufacturing processes such as rapid prototyping, shape metal deposition or machining processes, among others. The result is a layer-by-layer metal deposition which can be used to build-up complex structures for components such as turbine blades, aircraft stiffeners, cooling systems or medical implants, among others.

Ad hoc FE framework for the numerical simulation of the AM process by metal deposition is introduced. Description of the calibration procedure adopted is presented.

The objectives of this paper are twofold: firstly, this work is intended to calibrate the software for the numerical simulation of the AM process, to achieve high accuracy. Secondly, the sensitivity of the numerical model to the process parameters and modeling data is analyzed.

The purpose of this paper is to report the influence of the peak laser power on laser micro sintering 4-μm nickel powder using Q-switched 1064-nm Nd:YAG laser.

Experimental study has been performed. Nickel powder with grain size of 4 μm has been utilized. A Q-switching duration of 20-25 μs and rate of 20-40 kHz have been used.

The peak power intensity is so high that the metal particles and molten pool are blown away, leading to laser micro sintering not being successfully proceeded. The scanning line obtained by continuous-wave (CW) laser looks like a rod owing to balling effect. Using a suitable peak power intensity, a good-shaped sintering line can be obtained because the plasma can protect the molten metal from oxidation, and improve the wettability of the system. In addition, the plasma flattening effect may also contribute to the form of the good-shaped sintering line in pulsed laser sintering regime.

The role of plasma induced by pulsed laser with high peak power intensity has been found during pulsed laser sintering under an ambient environment.

The purpose of this paper is to varify, the air drawing model and the air jet flow field model of dual slot shape die for a polymer in a melt blowing process were established, by the experimental results obtained with experimental equipment.

The air jet flow field model is solved by introducing the finite difference method. The air drawing model of polymers in the melt blowing process was studied with the help of the simulation results of the air jet flow field.

The higher air initial velocity and air initial temperature can all yield finer fibers and causes the fibers to be attenuated to a greater extent.

The predicted fiber diameter agrees well with the experimental result, which verifies the reliability of these models. At the same time, the results also reveal the great potential of this research for the computer-assisted design of melt blowing technology.

Magnesium alloys are becoming prominent as an alternative to the permanent biomedical implants. In present work, electric discharge drilling (EDD) process has been investigated and optimized for ZM21 Mg alloy that can be used for producing perforated bone implants having geometrically precise micro holes.

Planning of experiments has been carried out in accordance to the Taguchi mixed L18 orthogonal array (OA). The hole overcut (HO), circularity at entrance (Cent) and circularity at exit (Cext) of drilled micro holes were measured as response characteristics during experimentation corresponding to different settings of EDD input parameters. For optimizing multiresponse characteristics, the hybrid approach of grey relational analysis, regression analysis and particle swarm optimization has been implemented.

It is found from hybrid approach that brass electrode along with Ip; 3 Amp, Ton; 50 µs and Toff; 52 µs outperformed over all other parametric settings against the collective result of response characteristics. The experimental values of response characteristics at suggested optimized setting are HO: 93.48 µm; Cent: 0.988 and Cext: 0.992, respectively.

The optimization of EDD process for developing perforated Mg alloy bone implants, using hybrid approach is still missing.

This paper aims to work exhibits the temperature distribution over the surface of the workpiece during plasma arc cutting process.

The moving heat source is taken into consideration for calculating the heat created by plasma arc. The heat is generated at the plasma – liquid metal boundary. The heat of fusion is also considered for estimation because of molten layer separates the plasma and solid layer. This causes to hamper the heat transfer towards the melting front. Eliminating the heat resistance may calculation error at high cutting speed. Power required to melt the material depends on the speed of the cut.

Higher cutting speed increases the power required. The temperature drop over the layer of molten front increases as the speed of cut increases at higher Peclet number. Different thickness of the molten layer was taken for calculation i.e. zero thickness, 10 and 20 per cent.

The estimated results are shown in non-dimensional form. So, the method can be applied for any other types of material.

This paper is the second of a series dealing with the blowholing problem on through‐hole plated printed circuit boards. In the previous paper the authors have considered the impact of the problem on the UK electronics assembly industry. Here they consider the nature of the gas causing blowholes and voids, its origin and the kinetics of its generation and evolution. When a printed circuit board with plated‐through‐holes is wave soldered, the thermal spike of the molten solder activates the evolution of gas, sometimes in relatively enormous quantities. The gas is seen bubbling from the surface of the molten solder in the joint. Upon freezing, the solder either traps the gas in a void enclosed within the fillet or, if the gas is escaping from the surface as freezing occurs, forms a blowhole.

Cotton-comfortable multi-ply face mask fabrics have been developed at The University of Tennessee's Textiles and Nonwovens Development Center (TANDEC) which have a repellent finished outer spunbond (SB) polypropylene (PP) layer, a middle layer of electrostatically charged (EC) melt blown (MB) PP, and a face side of a cotton-rich nonwoven. The EC MB PP layer effectively filters out aerosols and particulate containing bacteria and viruses, thereby protecting both the wearer and other personnel in the environment. In addition, a cotton-rich nonwoven layer on the body side provides the aesthetics and comfort of cotton, and also better retains antibacterial finish for neutralizing any microbes that penetrate the EC filter media. Filtration efficiency (FE) against 0.1 μm NaCl particles and the pressure drop were determined at TANDEC. FE to water aerosol containing Staphyloccus aureus bacteria per the In Vitro Bacterial Filtration Efficiency (BFE) test and to virus (φX174) per the In Vitro Viral Filtration Efficiency (VFE) were determined at Nelson Laboratories. The percent reduction of bacteria after the BFE test was also ascertained by Nelson Laboratories by a method adapted from AATCC 100.