汽车发动机罩压合模设计

介绍了汽车发动机罩压合模的结构设计,对模具中采用的新型预压合机构、压料板支撑结构和挡料装置进行了详细阐述。实践证明,模具结构能很好地满足产品压合后的精度要求,同时极大地提高了生产效率。

皮卡汽车货箱后门压合模设计

本文介绍了某皮卡汽车货箱后门压合模的结构设计，对压合模设计原理及模具中采用的预压合机构、模具的运动过程进行了详细阐述。

压合模设计及应用

本文介绍了日产发动机罩压合模的结构设计,并对模具中的压合机构等进行了详细的阐述。

Application of pre-alloyed powders for diamond tools by ultrahigh pressure water atomization

Copper, iron and cobalt based pre-alloyed powders for diamond tools were prepared by ultrahigh pressure water atomization（UPWA） process. Pre-alloyed powders prepared by different processes including UPWA, conventional water atomization （CWA） and elemental metal mechanical mixing （EMMM） were sintered to segments and then compared in mechanical properties, holding force between matrix and diamond, fracture morphology of blank and sintering diamond section containing matrix. The results showed that the pre-alloyed powder prepared by UPWA exhibits the best mechanical properties including the relative density, the hardness and the bending strength of matrix sinteredsegment. Sintered segments fractography of UPWA pre-alloyed powder indicatesmechanical mosaic strength and chemical bonding force between the pre-alloyed powder and the diamond, leading to the great increase in the holding force between matrix and diamond. The mechanical performance andthe service life of diamond tools were greatly improved by UPWA pre-alloyed powders.

Effects of shot speed and biscuit thickness on externaly solidified crystals of high-pressure diet cast AM60B magnesium alloy

Standard mechanical test bars with a diameter of 6.4 mm and a gauge length of 50 mm were processed, and the microstructures of die cast AM60B alloy under different die casting process parameters were observed. The influences of the slow shot speed, the fast shot speed and the biscuit thickness on the externally solidified crystals （ESCs） were investigated. With the increase of the biscuit thickness, the number of the ESCs in the cast samples decreases. Under a low slow shot speed, larg ESCs are found in the cast structure and a high fast shot speed results in more spherical ESCs. The relationships between ESCs and process parameters were also discussed.

Influence of pre-strain and heat treatment on subsequent deformation behavior of extruded AZ31 Mg alloy

Pre-compression and heat treatment were performed on an extruded AZ31 Mg alloy,and their effects on subsequent deformation behavior were investigated.The results show that at low temperature annealing(170 ℃ for 4 h),the extruded samples with and without annealing exhibit a nearly equivalent yield stress(~148 MPa) because their microstructures are nearly unchanged.However,under the same annealing condition,the yield stress of sample with pre-twinning and subsequent annealing(~225 MPa) is higher than that of the pre-twinned one(~200 MPa).The former sample presents a hardening effect because the solute atoms segregated on twin boundaries lead to a strengthening effect.The pre-twinned sample annealed at 400 ℃ for 1 h shows a higher ultimate elongation(~28%) than the pre-twinned one(~15%),but its yield stress(~125 MPa) is much lower than that of the pre-twinned one(~200 MPa).

Combined effect of isothermal annealing and pre-compression on mechanical properties of Cu_(36)Zr_(48)Al_8Ag_8 bulk metallic glass

The combined effects of isothermal annealing and pre-compression on the mechanical properties of Cu36Zr48Al8Ag8 bulk metallic glass （BMG） were investigated. The as-cast specimens were first annealed at 743 K for 10 min, and then pre-compressed under 800 MPa for 1, 3, 5 and 10 h, respectively. The results indicated that annealing resulted in the formation of nanocrystals with a diameter of -10 nm in the amorphous matrix and a drastic decrease of the free volume, leading to complete loss of the plasticity of the BMG. Applying pre-compression under a stress of 800 MPa for a proper duration （5 h） resumed part of the lost free volume in the BMG matrix and therefore partially recovered the plasticity. A very long period of pre-compression （10 h） decreased the free volume again, which was caused by the excessive crystal growth.

Key technologies of frequency-hopping frequency synthesizer for Bluetooth RF front-end

A scheme of a frequency-hopping frequency-synthesizer applied to a Bluetooth ratio frequency （RF） front-end is presented,and design of a voltage controlled oscillator （VCO） and dual-modulus prescaler are focused on.It is fabricated in a 0.18 μm mixed-signal CMOS （complementary metal-oxide-semiconductor transistor） process.The power dissipation of VCO is low and a stable performance is gained.The measured phase noise of VCO at 2.4 GHz is less than -114.32 dBc/Hz.The structure of the DMP is optimized and a novel D-latch integrated with ＂OR＂ logic gate is used.The measured results show that the chip can work well under a 1.8 V power supply.The power dissipation of the core part in a dual modulus prescaler is only 5.76 mW.An RMS jitter of 2 ps is measured on the output signal at 118.3 MHz.It is less than 0.02% of the clock period.

The Analysis of Seismic Data Structure and Oil and Gas Prediction

In this paper, a new concept called numerical structure of seismic data is introduced and the difference between numerical structure and numerical value of seismic data is explained. Our study shows that the numerical seismic structure is closely related to oil and gas-bearing reservoir, so it is very useful for a geologist or a geophysicist to precisely interpret the oil-bearing layers from the seismic data. This technology can be applied to any exploration or production stage. The new method has been tested on a series of exploratory or development wells and proved to be reliable in China. Hydrocarbon-detection with this new method for 39 exploration wells on 25 structures indi- cates a success ratio of over 80 percent. The new method of hydrocarbon prediction can be applied for: (1) depositional environment of reservoirs with marine fades, delta, or non-marine fades (including fluvial facies, lacustrine fades); (2) sedimentary rocks of reservoirs that are non-marine clastic rocks and carbonate rock; and (3) burial depths range from 300 m to 7000 m, and the minimum thickness of these reservoirs is over 8 m (main frequency is about 50 Hz).

Microstructure and mechanical properties of 6082 aluminum alloy processed by preaging and hot forging

A novel forging process of 6082 aluminum alloy is proposed, which can save time and reduce energy consumption while ensuring mechanical properties. In this process, the billet was preforged at solid solution temperature and then preaged, followed by warm forging at 200 ℃. The flow behavior of the preaged samples during compression and the mechanical properties of the formed samples were investigated by hot compression tests. The differences in the precipitated phases of the samples with different processing parameters were analyzed by scanning electron microscopy(SEM), transmission electron microscopy(TEM), and differential scanning calorimetry(DSC). The best comprehensive performance was obtained after preaging at 120 ℃ for 4 h and holding at 200 ℃ for 10 min, and the Vickers hardness was HV 128, which was higher than that of the traditional process. Precipitation strengthening and dislocation strengthening were improved when the samples were formed at 200 ℃. This forging process shows the advantages of short time consumption and low energy consumption, which can effectively improve the production efficiency while ensuring the strength after forming.

MICROVASCULAR DECOMPRESSION FOR HEMIFACIAL SPASM - TECHNICAL NOTES AND COMPLICATION PREVENTION : EXPERIENCE OF 338 CASES

Objective To summarize our clinical experience of microvascular decompression (MVD)for medically intractable hemifacial spasm(HFS) patients with emphasis on microsurgical manipulation and to improve cure rate and avoid surgical complications. Methods Three hundred and thirty-eight patients with HFS underwent MVD under general anesthesia . With the help of 'zero retraction' technique, prosthesis can be properly inserted between offending vessel loop and affected facial nerve REZ in a 'rolling ball' fashion under operative microscope. Results Surgical intervention achieved high relief rate of 91 .4% and no major complications, with low recurrence rate of only 3.2% after averaging more than two years' follow-up ( M = 32 months). Conclusion It is possible to approach to the facial nerve REZ with 'zero retraction', which is fundamentally important to clear from cranial nerve and cerebellar injury. Skilled microsurgical technique along with correct recognition and mobilization of offending vessels are a must to assure MVD a highly efficacious and low risk treatment of choice for HFS patients.

Preventing Coal and Gas Outburst Using Methane Hydration

According to the characteristics of the methane hydrate condensing and accumulating methane, authors put forward a new technique thought way to prevent the accident of coal and gas outburst by urging the methane in the coal seams to form hydrate. The paper analyzes the feasibility of forming the methane hydrate in the coal seam from the several sides, such as, temperature,pressure, and gas components, and the primary trial results indicate the problems should be settled before the industrialization appliance realized.

Effects of pre-compression on formation of dynamic precipitates and creep anisotropy of hot-extruded AZ91−2Y magnesium alloy

The creep anisotropy behavior under different stresses at 180℃ of hot-extruded AZ91−2Y magnesium alloy with pre-compression(PC)and without pre-compression(NPC)was studied.Microstructure,texture and mechanical properties of the alloy were examined by scanning electron microscopy(SEM),electron backscatter diffraction(EBSD),transmission electron microscopy(TEM)and tensile creep tests.The results revealed that the creep resistance was proportional to the volume fraction of spherical Mg_(17)Al_(12) precipitates.The dynamic precipitation of large volume fraction of lamellar Mg_(17)Al_(12) in NPC samples leads to the basaláañslip as the dominant creep mechanism,and the NPC samples have obvious anisotropy.In the PC samples,dynamic precipitation of large volume fraction of spherical Mg_(17)Al_(12) has inhibitory effect on the basaláañslip.The pyramidalác+añslip and twinning improve the creep anisotropy resistance significantly.

Critical weight on bit of double-driven bottomhole assembly during vertical and fast drilling

It is difficult to determine the optimal weight on bit (WOB) of the double-driven bottomhole assembly (DD-BHA, with double stabilizers and a bent housing positive displacement motor (PDM)) which is employed during vertical and fast drilling. High WOB leads to well deviation out of control, and low WOB leads to low rate of penetration (ROP). So considering the rock physical properties, the anisotropy index function of polycrystalline diamond compact (PDC) bit was derived with the structure and cutting performance parameters of the bit, and the effect of natural hole deviation tendencies on the performance of DD-BHA resisting deviation was represented. The concept of elliptic deformation ratio was used to characterize the performance of DD-BHA resisting deviation. Eventually, a model calculating the critical WOB was established. By comparing the model predictions with the measured hole angle changes in the field, the results show that the model predictions are accurate with error less than 5.8%, which can meet the operational requirements in the projects. Furthermore, the model was adopted to justify and guide the operating conditions and parameters during drilling, which shows that the optimum WOB predicted by the model can not only control deviation but also improve ROP effectively. The model is independent on the formation characteristics of blocks, so it can be expanded widely to other oilfields.

Distributed Adaptive Compressed Video Sensing Using Smoothed Projected Landweber Reconstruction

A novel Compressed-Sensing-based(CS-based)Distributed Video Coding(DVC)system,called Distributed Adaptive Compressed Video Sensing(DISACOS),is proposed in this paper.In this system,the input frames are divided into key frames and non-key frames,which are encoded by block CS sampling.The key frames are encoded as CS measurements at substantially higher rates than the non-key frames and decoded by the Smoothed Projected Landweber(SPL)algorithm using multi-hypothesis predictions.For the non-key frames,a small number of CS measurements are first transmitted to detect blocks having low-quality Side Information(SI)generated by the conventional interpolation or extrapolation at the decoder;then,another group of CS measurements are sampled again upon the decoder’s request.To fully utilise the CS measurements,we adaptively allocate these measurements to each block in terms of different edge features.Finally,the residual frame is reconstructed using the SPL algorithm and the decoded non-key frame is simply determined as the sum of the residual frame and the SI.Experimental results have revealed that our CS-based DVC system yields better rate-distortion performance when compared with other schemes.

A research study on the spallation strength of LY12 aluminum under the pre-compression condition

To pre-compress the disk-shaped LY12 samples along the radial direction can be done with the aid of overstress assembly by heating or by mechanical clamping, which can also generate the deviatoric stress fields under different states. The spallation signals of these pre-compressed samples are measured by VISAR in the light-gas gun shock experiments. The experimental results show that even under the same impact velocity, the pullback amplitudes of the velocity at the free surface of the sam- pies vary significantly. According to the experimental data, we propose a distinct concept that the material spallation strength is closely related to the deviatoric stress fields in the material. Based on the numerical simulation, we develop a damage con- stitutive model, which reveals that the deviatoric stress reduces the tensile threshold of the void growth. The numerical inves- tigations also demonstrate that the spallation strength decreases as pre-compression increases. The experimental idea proposed in this paper can also be used to study the spallation process in other structures.