Papers by Keyword: Ejection

Abstract: This paper investigates the effect of the laser cutting parameters on the heat-affected zone, and on the boundary layer of stainless steel processing. A new analytical resolution based on the boundary layer theory is used to deduce the interaction effects of the cutting parameters on the above zones. The results revealed that, the laminar nitrogen assist gas has a negligible effect on the HAZ depth but it has a remarkable effect on the molten boundary layer. It is also noticed that the pressure gradient remains very small compared to the interface shearing and the conductive heat losses from the cutting zone towards the substrate is dominant compared to the convective heat losses towards the gas.

Abstract: During operation of coal mines, polluted air is emitted from the ventilation shafts, it contains large amount of carbon and rock dust with various physical and mechanical composition. Dust contains freshly formed silicon dioxide and other components of the mineral product that are hazardous to human health, which are scattered in the surface layer of the atmosphere. Mainly fine dust comes from the mine workings, and the release of the total dust mass by 80 – 96 % is due to the operation of the loading and unloading complex. It is established that the level of dustiness decreases mainly due to the settling in the mine workings of the coarsely dispersed dust fraction. The environment receives mainly fine dust with a high content of fine particles, which can be intensively dispersed outside the sanitary protection zone of the mine. A mathematical model is obtained in the form of a differential equation of mass transfer, which takes into account the physic and mechanical composition of the dust emission from the ventilation shaft of the coal mine as a factor of ecological hazard. The obtained results determine the directions of effective struggle against dust emissions of coal mines.

Abstract: Electro Sinter Forging (ESF) is a new sintering process based on Joule heating by high electrical current flowing through compacted metal powder under mechanical pressure. The whole process takes about three seconds and is based on a closed-die setup, where the sample is sintered inside a die. A near-net shape component is therefore manufactured. One of the challenges associated with this process is the ejection of the sample after sintering. Due to powder compaction and axial loading during sintering, a radial pressure is generated at the die/sample interface. Consequently, the ejection can be difficult, and the final quality of the sintered component in terms of roughness and surface defects may be affected. In the present work, four different lubricants and non-lubricated conditions were tested to investigate the effects on the final part quality. The sintered sample is a disc made of commercially pure titanium powder. The force was measured while ejecting the samples by using a speed-controlled press. The surface roughness parameter Sa was measured by using a laser confocal microscope.

Abstract: In order to study the fragmentation of projectile and ejection of debris clouds caused by hypervelocity impacting mesh bumper, simulation of aluminum sphere projectile hypervelocity normal impacting aluminum mesh bumper was practiced with SPH arithmetic of LS-DYNA soft. The diameter of projectile was 4mm. Impact velocities of aluminum spheres were varied between 2.2km/s and 6.2km/s. The impact angle was 0°. The relationship between the debris clouds characteristic of projectile and the impact position on aluminum mesh bumper was studied. The effect on fragmentation of projectile from different combination mode of aluminum mesh bumper was analyzed. The results showed that the morphologies of the debris cloud varied with the impact position when a projectile impacted the mesh bumper. The debris clouds as palpus was found, and some local kinetic energy concentrated appeared in the debris clouds. Debris clouds distribution was more uniform when projectile impacted wire across point on the mesh bumper. Debris clouds had more diffuse area and less residual kinetic energy when mesh bumper was combined with interleaving mode. Mesh bumper combined with interleaving mode was helpful in enhancing the protection performance of shields.

Abstract: A simulation method was used to study the effects of physical parameters, including the contact angle between molten metal and material of orifice, surface tension and viscosity on particle formation of POEM. Droplets can be stably obtained only when the contact angel is at least 90° or larger, as well as the surface tension is adequate. Within a wide range, viscosity has little effect on droplet formation; as the viscosity increases, necking time is postponed and vibration time is shortened.

Abstract: A micropump with the function of ejecting droplet is designed and fabricated. It consists of the three components including the PZT actuator, pump body and nozzle plate. The pump body is made of the silicon while the nozzle plate is formed by nickel electroforming. The nozzle plate with single orifice is assembled to the pump body. The micropump is designed with the rectangular pressure chamber and the diffuser as the dynamic passive valve. It is driven by the PZT actuator which deflects the rectangular diaphragm through a bulge on diaphragm. The design of diaphragm with a bulge makes the assembly of the actuator easier and generates sufficient volume displacement. The volume displacement is not only predicted by ANSYS simulation but also verified by 2-dimensional laser scanning vibrometer. And, the prediction and measurement agree to some extent. The ejected droplets are observed by a visualization setup.