提高化油器压合件精度的一次尝试

本文以ＥＱＨ２０５Ｂ型化油器中小喉管喷咀的压合过程为例，初步探讨了提高化油器压合件相对位置精度的方法。

汽车压合件外板展开尺寸的近似计算

在规划汽车压合件的外板生产工艺时,需要根据压合件总成的制件数模,设计出压合前的外板展开数模。讨论了外板展开尺寸的计算方法,并提出了应用方式,具有理论和实践意义。

Springback analysis of 6016 aluminum alloy sheet in hot V-shape stamping

Springback behavior of 6016 aluminum alloy in hot stamping was investigated by a series of experiments under different conditions using V-shape dies and a finite element model which was validated reliable was used to further elucidate the springback mechanism. The effects of initial blank temperature, blank-holding force, die closing pressure and die corner radius were studied. It is found that springback decreases remarkably as the initial blank temperature rises up to 500 °C. The springback also reduces with the increase of die holding pressure and the decrease of die corner radius. Under different initial temperatures, the influence of blank-holding force is distinct. In addition, the bending and straightening of the side wall during the stamping process is found to interpret the negative springback phenomenon.

Effects of combined addition of Y and Ca on microstructure and mechanical properties of die casting AZ91 alloy

A series of die casting heat-resistant magnesium alloys based on Mg-Al system were developed for automotive application by adding Y and various amounts of Ca. The mechanical properties and microstructures of die casting AZ91 alloy with combined addition of Y and Ca were investigated by optical microscopy, scanning electronic microscopy, X-ray diffractometry and mechanical property test. The results show that the combined addition of Y and Ca can refine the as-die-cast microstructure, result in the formation of Al2Ca phase and Al2Y phase, and inhibit the precipitation of Mg17Al12 phase. The combined addition of Y and small amount of Ca has little influence on the ambient temperature tensile properties, but increasing the content of Ca can improve significantly the tensile strength at both ambient and elevated temperatures. It is found that for AZ91-1Y-xCa alloy, the hardness and the elevated temperature tensile strength increase, while the elongation decreases with increasing the addition of Ca. The mechanism of mechanical properties improvement caused by the combined addition of Y and Ca was also discussed.

Feasibility of semi-solid die casting of ADC12 aluminum alloy

The feasibility of semi-solid die casting of ADC12 aluminum alloy was studied. The effects of plunger speed, gate thickness, and solid fraction of the slurry on the defects were determined. The defects investigated are gas and shrinkage porosity. In the experiments, semi-solid slurry was prepared by the gas-induced semi-solid （GISS） technique. Then, the slurry was transferred to the shot sleeve and injected into the die. The die and shot sleeve temperatures were kept at 180 ℃ and 250 ℃, respectively. The results show that the samples produced by the GISS die casting give little porosity, no blister and uniform microstructure. From all the results, it can be concluded that the GISS process is feasible to apply in the ADC12 aluminum die casting process. In addition, the GISS process can give improved properties such as decreased porosity and increased microstructure uniformity.

Research on an inertial piezoelectric actuator for a micro in-pipe robot

A new kind of inertial piezoelectric actuator for a micro in-pipe robot is proposed and studied. The actuator is composed of a body, corresponding to a mass rod, and four elastic legs. Each leg is a composite piezoelectric bimorph beam, made up of a middle metal element, an upper and lower piezoelectric elements. The mechanism is driven by an asymmetric waveform voltage, such as saw-toothed waveform, and utilizes the dynamic relationship between the maximum static friction force and the inertial force. To study the actuator, firstly, the constituent equation of a composite piezoelectric bimorph under both applied voltage and external force was inferred by thermodynamics. Secondly, the dvnamic model of the actuator was established analyzing the relationship between the locomotive states, viz. displacement and velocity, and design parameters, such as piezoelectric strain constant, elastic modulus,length, width and thickness of the piezoelectric element, actuator mass, and driving vohage. At last, the dynamic equation was solved and the theoretical calculation of the inherent frequency was more consistent with the experimental data, which proved the rationality of the model. All these lay a theoretical foundation of the micro actuator parameter optimization and more research on a micro robot.

Liquid Axial Mixing in Packed Tower at Elevated Pressure

Liquid phase axial mixing was measured with the tracer technique in a packed column with inner diameter of 0.15m, in which the structured packing, Mellapak 350Y, was installed. Tap water as the liquid phase flowed down through the column and stagnant gas was at elevated pressure ranging from atmospheric to 2.0MPa. The model parameters of Bo and 9 were estimated with the least square method in the time domain. As liquid flow rate was increased, the liquid axial mixing decreased. Under our experimental conditions, the effect of pressure on Bo number on single liquid phase was negligible, and eddy diffusion was believed to be the primary cause of axial mixing in liquid phase.

Wrinkling behavior of magnesium alloy tube in warm hydroforming

In tube hydroforming with axial feeding,under the effect of coupled internal pressure and axial stress,wrinkles often occur and affect the forming results.Wrinkling behavior of an AZ31B magnesium alloy tube was experimentally investigated with different loading paths at different temperatures.Features of wrinkles,including shape,radius and width,were acquired from the experiments,as well as the thickness distribution.Numerical simulations were carried out to reveal the stress state during warm hydroforming,and then the strain history of material at the top and bottom of the wrinkles were analyzed according to the stress tracks and yielding ellipse.Finally,effects of loading paths on expansion ratio limit of warm hydroforming were analyzed.It is verified that at a certain temperature,expansion ratio limit can be increased obviously by applying a proper loading path and realizing enough axial feeding.

Heat and Water Vapour Transfer Trough the Envelope of a Cold Chamber

The diffusion of water vapour in the atmospheric air through the elements of the envelope of a cold storage room, caused by the pressure gradient between the external and internal environment is inevitable in most situations. In fact, if the conditions in the interior of an envelope element are such as to enable the vapour freezing of the migrant water, the increase in volume from the formation of ice will causes the deformation of this element with very serious consequences, which can go up to its partial or total destruction. In this scenario, readily note the importance ofvapour barriers associated with a properly designed insulation, tend to not only reduce the amount of water diffused, but also prevent the achievement of the conditions for freeze inside the engaging elements. The purpose of this work is to formulate the procedure for design of vapour barriers connected with the design of optimized thermal insulation, and then apply it to a cold chamber located in Portugal. Vapour barriers and the procedure for its design are both mandatory. The required thickness of the vapour barrier is relatively small, and the most appropriate insolation （maintaining the optimal thickness） is the black cork agglomerate.

Effect of extrusion on properties of Al-based composite

An aluminium alloy and its composite with dispersed SiC particles made by liquid metallurgy route were extruded under optimized conditions.The properties were characterized in terms of microstructure,hardness and sliding wear behaviour and then compared between the extruded and cast alloys and composites,in order to understand the benefits of composite and extrusion on the alloy.It was observed that composites drastically increased the hardness and the extruded composites further increased this value.The advantage of composites was realized in sliding wear tests.

Oxygen sufficiency controls TOP mRNA translation via the TSC-Rheb-mTOR pathway in a 4E-BP-independent manner

Cells encountering hypoxic stress conserve resources and energy by downregulating the protein synthesis. Here we demonstrate that one mechanism in this response is the translational repression of TOP mRNAs that encode components of the translational apparatus. This mode of regulation involves TSC and Rheb, as knockout of TSC1 or TSC2 or overexpression of Rheb rescued TOP mRNA translation in oxygen-deprived celts. Stress-induced translational repression of these mRNAs closely correlates with the hypophosphorylated state of 4E-BP, a translational repressor. However, a series of 4E-BP loss- and gain-of-function experiments disprove a cause-and- effect relationship between the phosphorylation status of 4E-BP and the translational repression of TOP mRNAs under oxygen or growth factor deprivation. Furthermore, the repressive effect of anoxia is similar to that attained by the very efficient inhibition of mTOR activity by Torin 1, but much more pronounced than roptor or rictor knockouL Likewise, deficiency of raptor or rictor, even though it mildly downregulated basal translation efficiency of TOP mRNAs, failed to suppress the oxygen-mediated translational activation of TOP mRNAs. Finally, co-knockdown of TIA-1 and TIAR, two RNA-binding proteins previously implicated in translational repression of TOP mRNAs in amino acid-starved cells, failed to relieve TOP mRNA translation under other stress conditions. Thus, the nature of the proximal translational regulator of TOP m RNAs remains elusive.

Effects of aluminum additive on diamond crystallization in the Fe-Ni-C system under high temperature and high pressure conditions

In this paper, we investigate diamond crystallization in Fe-Ni-C with an aluminum additive and the capability of aluminum for converting graphite to diamond in a series of experiments at 4.9-5.5 GPa and 1240-1500℃. Our experimental results show that the growth habits of diamond crystal have been significantly influenced by the addition of aluminum as a catalyst. The crystal color changes from yellow to nearly colorless. The morphology of the synthesized diamond crystals gradually changes from cubic-octahedron to octahedron in the Fe-Ni-C systems with increasing aluminum additive. The lowest synthesis conditions fell first and then rose with increasing aluminum. We found a suitable addition of aluminum is very effective in lowering the synthesis conditions while an excessive aluminum additive may have a suppressive effect on the diamond nucleation.