基于定量失配的弧齿锥齿轮齿面修形设计及实验验证

以弧齿锥齿轮齿面修形设计为研究对象,提出了一种基于定量失配修形的齿面设计方法。揭示了齿面修形量、修形系数与齿面结构参数间的数学关系,在完全共轭齿面的基础上引入2阶修形曲面,建立了以齿面接触性能为导向的目标齿面;建立目标齿面与理论齿面间的齿面偏差修正模型,求解了机床调整加工参数修正量。以一对弧齿锥齿轮副为例进行验证,根据齿面修形量快速计算对应的修形系数,解决了修形系数盲目选取的问题。修形后齿面接触性能得到改善,切齿实验结果与理论分析结果一致。实验验证了提出的基于定量失配修形的弧齿锥齿轮齿面设计方法的有效性,该方法同样适用于其他齿轮齿面的修形设计。

横向厚差与宽厚比对冷轧带钢临界失稳板形的影响

基于秒流量相等的体积不变条件和弹性薄板稳定性理论,推导了理想条件和实际工况下冷轧带钢横向厚差、宽厚比与板形之间的耦合关系,分析各因素对临界失稳板形的综合影响规律。参考理想条件下横向厚差与板形的基本关系,建立实际工况下的影响模型。结果表明,0.3mm以下厚度薄带的横向厚差变化量对板形的影响明显;根据弹性薄板稳定性模型,分析横向厚差和宽厚比对临界失稳板形的影响。结果表明,当冷轧带钢的宽厚比大于3000时,临界失稳应力明显减小。通过实测1450六辊冷轧机的两卷典型带钢横向厚差,得到在生产不同宽厚比的超薄规格带钢时,需要根据入口带钢的横向厚差,调整负载辊缝形状,以保证出口带钢的横向厚差变化量满足板形不失稳条件,从而获得了良好的板形。

圆板液压胀形件失稳变形理论和其顶点极限应变的预测

本文依据最小变形能量原理,分析了板料液压胀形件的失稳变形机制;并在此基础上,提出了圆板液压胀形件顶点的极限应变预测方法。米用作者新近提出的正交异性非二次式屈服函数,对一些正变异性板进行了应用;结果表明,预测结果与试验结果基本一致。

液压胀形中板料失稳胀形高度H_m的研究

根据液压胀形中载荷法判断板料失稳的准则,用不同方法研究了板料失稳胀形高度H_m,导出了相应的失稳公式,并与九种板料的实验值进行了比较,结果表明失稳公式H_m=R_0·(e(N+0.4171)/2-1)^(1/2)和H_m=R_0·((1+2N)/(5-2N))^(1/2)与实验值符合得较好,具有实用价值。

Prediction of stiffener buckling in press bend forming of integral panels

In order to predict the buckling of stiffeners in the press bend forming of the integral panel,a method for solving the critical buckling load of the stiffeners in press bend forming process was proposed based on energy method,elastic-plastic mechanics and numerical analysis.Bend to buckle experiments were carried out on the designed press bend dies.It is found that the predicted results based on the proposed method agree well with the experimental results.With the proposed method,the buckling of the stiffeners in press bend forming of the aluminum alloy integral panels with high-stiffener can be predicted reasonably.

Flow instability criteria in processing map of superalloy GH79

Hot compression tests were conducted on a Gleeble-1500D thermal simulating tester.Based on the deformation behavior and microstructural evolution of superalloy GH79,different types of instability criteria of PRASAD,GEGEL,MALAS,MURTY and SEMIATIN were compared,and the physical significance of parameters was analyzed.Meanwhile,the processing maps with different instability criteria were obtained.It is shown that instability did not occur when average power dissipation rate was larger than 60%in the temperature range of 900-930°C and 960-1080°C,corresponding to the strain rate range of 5×10 -4 -1.8×10 -1 s -1 and 5×10 -4 -1.5×10 -1 s -1 ,respectively.The two domains are appropriate for the processing deformation of superalloy GH79.

Morphological and Anatomical Analyses of a Floral Organ Mutant in Rice

A spontaneously occurred rice ( Oryza sativa L.) mutant characterized by homeotic conversions in glumes and stamens was found in the progeny of a breeding material. The mutant plant shows degenerated glumes and morphological transformation of stamens into pistils. A mutant floret consists of 1 to 3 completely developed pistils and 4 to 6 incomplete pistils with no ovary. Some pistilloid stamens still have filaments but tipped by bulged tissue and 0 to 3 stigmas. Three ovaries in a single floret were observed in its cross and longitudinal sections. When the mutant plants were pollinated with pollens from wild type plants, one or two naked seeds instead of a caryopsis could be produced in a single floret. The mutant is controlled by a single recessive gene since its F 1 hybrid plants were restored to wild type and 3∶1 ratio of wild type to mutant plants were observed in the progeny of heterozygotes. It seems that the mutant phenotype of the homeotic conversions in glumes and stamens is similar to that of the B loss_of_function mutants in Arabidopsis and Antirrhinum .

A method for prediction of unstable deformation in hot forging process by simulation

A method is proposed for prediction of the unstable deformation in hot forging process using both the determined thermomechnical parameter windows of the unstable deformation zones and finite element simulation. Taking Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy as the testing material, the thermomechnical parameter windows of the unstable deformation zones for the Ti-alloy are integrated into a commercial finite element simulation software platform. The distribution and variation of the unstable deformation zones of the alloy in hot compression process are simulated and predicted using the tailor-made finite element codes in the finite element platform. The simulation results tally with the physical experiments and the proposed method for simulation and prediction of the unstable deformation is thus verified and its efficiency is validated.

Correction of buckling distortion by ultrasonic shot peening treatment for 5A06 aluminum alloy welded structure

Ultrasonic shot peening treatment （USPT） was proposed to correct welding buckling distortion. The residual stress distribution along the depth direction of the peened zone was measured by an X-ray diffractometer. The microstructure of the treated specimens was investigated by scanning electron microscopy （SEM）. The Vickers microhardness was measured in different areas of welded joint before USPT and along the depth direction of the weld after USPT. The experimental results indicated that the welding buckling distortion of 5A06 aluminum alloy butt joint can be essentially corrected by USPT; the average correction rate reached 90.8% in this study. Furthermore, USPT enhanced specimens by work hardening. The microstructure of the peened zone was improved; moreover, the distribution of the precipitates and grains presented an apparent orientation.

Driving Behavior Shaping Model in Road Traffic System

In order to give a new way for modeling driving behavior, identifying road traffic accident causation and solving a variety of road traffic safety problems such as driving errors prevention and driving behavior analysis, a new driving behavior shaping model is proposed, which could be used to assess the degree of effect of driving error upon road traffic safety. Driver behavior shaping model based on driving reliability and safety analysis could be used to identify the road traffic accident causation, to supply data for driver's behavior training, to evaluate driving procedures, to human factor design of road traffic system.

Meso-mechanical analyses of shape memory alloy wires reinforced smart structures with damages

The thermo-mechanical behaviors of shape memory alloy (SMA) wires reinforced smart structures with damages are analyzed through variational principle and meso-mechanical method.A governing equation on the structure is derived.Mathematical expressions on meso-displacement field,stress-strain field of typical element with damages are presented.A failure criterion for interface failure between SMA wires and matrix is established under two kinds of actuation which are dead-load and temperature,where the temperature is included in effective free restoring strain.In addition,there are some other composing factors in the failure criterion such as interface properties,thermodynamical properties of SMA,initial debonding length L-l,etc.The results are significant to understand structural strength self-adaptive control and failure mechanism of SMA wires reinforced smart structures with damages,and provide a theoretical foundation for further study on the integrity of SMA smart structures.

Inconel 617 and Stellite 6 alloys for tooling in thixoforming of steels

Thermal fatigue and high temperature wear are the two principle failure mechanisms for thixoforming dies. Samples of Inconel 617 and Stellite 6 alloys were submitted to thermal cycling under conditions which approximate thixoforming of steels and to sliding wear tests at 750 ℃. The experimental results thus obtained were compared with those of the X32CrMoV33 hot work tool steel. The Inconel 617 and Stellite 6 samples are much more resistant to oxidation and to softening than the hot work tool steel, providing a superior resistance to thermal fatigue cracking. The wear resistance of the Inconel 617 and Stellite 6 alloys at 750 ℃ is also markedly superior. The adhesive oxides growing slowly on Inconel 617 and Stellite 6 alloys sustain the wear action without spalling and are claimed to be responsible for the superior wear resistance of these alloys at 750 ℃.

Instability analysis of free deformation zone of cylindrical parts based on hot-granule medium-pressure forming technology

The cylindrical part of sheet metal based on hot-granule medium-pressure forming (HGMF) technology was investigated.The stress functions of the free deformation zone and the fracture instability theory were combined to establish the analytical expression of the critical pressure of punch. The results show that the active friction between the granule medium and the sheet metal, as well as the non-uniform internal pressure presented by the solid granule medium, can obviously improve the forming performance of the sheet metal. The critical pressure of punch increases with the increment of the friction coefficient between the granule medium and sheet metal, as well as the plastic strain ratio, whereas it decreases with the increase of the material-hardening exponent. Furthermore, the impact on the critical pressure from high to low order is the plastic strain ratio, the friction coefficient,and material-hardening exponent. The deep-drawing experiment with HGMF technology on AZ31B magnesium alloy sheet verified the instability theory.Key words: hot-granule

Wear behavior of high strength and high conductivity Cu alloys under dry sliding

In order to study the wear behavior of different kinds of contact wires,the dry sliding wear behaviors of Cu-Sn,Cu-Ag and Cu-Mg alloys prepared by up-drawn continuous casting and followed continuous extrusion were studied.The research was tested on a block-on-ring wear tester.The results indicate that the friction coefficient is remarkably influenced by the formation of a continuous tribofilm,which consists of oxidation film.The abrasion,adhesion,oxidation and plastic deformation are observed.Oxidation and abrasion wear mechanisms dominate at the lower sliding velocity and load.The combination of oxidation and adhesion play leading roles with the increasing load and velocity.Plastic deformation is detected under higher applied load and sliding velocities.

Calibration of split Hopkinson pressure bar system with special shape striker

In order to present basic guidance for system calibration of split Hopkinson pressure bar(SHPB) with the special shape striker,wave characteristics and dynamic responses of SHPB under striker impact were analyzed.Stress generated by the special shape striker tends to have a half-sine waveform and has little wave dispersion during its propagation.Impact velocities of the special shape striker and peak values of generated stress still have linear relation but with a different coefficient from that of cylindrical strikers.From stress histories on the surfaces of the input bar impacted by the special shape striker off-axially and obliquely,it is found that the misalignment impacts usually trigger wave distortion and amplitude decrease,which can be used to identify the poor system adjustment.Finally,the system calibration of SHPB with the special shape striker can be classified into four steps:system adjustment,wave distortion identification,measurement calibration and transmission calibration,where the measurement calibration factor and transmission calibration factor are elaborated and redefined.

Influence of bluff body shape on wall pressure distribution in vortex flowmeter

To investigate the influence of bluff body shape on wall pressure distribution in a vortex flowmeter,experiments were conducted on a specially designed test section in a closed water rig at Reynolds numbers of 6.2×10 4-9.3×10 4.The cross sections of the bluff bodies were semicircular,square,and triangular shaped,and there were totally 21 pressure tappings along the conduit to acquire the wall pressures.It is found that the variation trends of wall pressures are basically identical regardless of the bluff body shapes.The wall pressures begin to diverge from 0.3D(D is the inner diameter of the vortex flowmeter) in front of the bluff body due to the diversity in shape,and all reach the minimum values at 0.3D behind the bluff body.A discrepancy between the triangular or square cylinder and the semicircular cylinder in wall pressure change is observed at 0-0.1D behind the bluff body.It is also found that the wall pressures and irrecoverable pressure loss coefficients increase with flow rates,and the triangular cylinder causes the smallest irrecoverable pressure loss at a fixed flow rate.

Robust Watermarking of Mobile Video Resistant against Barrel Distortion

In head mounted display(HMD),in order to cancel pincushion distortion,the images displayed on the mobile should be prewarped with barrel distortion.The copyright of the mobile video should be verified on both the original view and the pre-warped virtual view.A robust watermarking resistant against barrel distortion for HMDs is proposed in this paper.Watermark mask is embedded into image in consideration of imperceptibility and robustness of watermarking.In order to detect watermark from the pre-warped image with barrel distortion,an estimation method of the barrel distortion is proposed for HMDs.Then,the same warp is enforced on the embedded watermark mask with the estimated parameters of barrel distortion.The correlation between the warped watermark and the pre-warped image is computed to predicate the existence of watermark.As shown in experimental results,watermark of mobile video can be detected not only from the original views,but also from the pre-warped virtual view.It also shows that the proposed scheme is resistant against combined barrel distortion and common post-processing,such as JPEG compression.

Microscale deformation behavior of sandstone mineral particles based on XCT scanning

This work aimed to quantify the physical and mechanical behavior of three-dimensional microstructures in rocks under uniaxial compression.A high-precision in situ XCT(X-ray transmission computed tomography)technology was applied to investigating the behavior of mineral grains in sandstone:the movement,the rotation deformation,and the principal strains between fault zone and non-fault zone.The results indicate that after unloading,the shear strain of mineral grains is periodic in the radial direction,the strain of mineral grains in the fracture zone is about 30 times of the macro strain of the specimen,which is about 5 times in the non-fracture zone,and the shear strain near the fault zone is larger than the compressive strain,and there is the shear stress concentration feature.

Using LBG quantization for particle-based collision detection algorithm

Most collision detection algorithms can be efficiently used only with solid and rigid objects, for instance, Hierarchical methods which must have their bounding representation recalculated every time deformation occurs. An alternative algorithm using particle-based method is then proposed which can detect the collision among non-rigid deformable polygonal models. However, the original particle-based collision detection algorithm might not be sufficient enough in some situations due to the improper particle dispersion. Therefore, this research presents an improved algorithm which provides a particle to detect in each separated area so that particles always covered all over the object. The surface partitioning can be efficiently performed by using LBG quantization since it can classify object vertices into several groups base on a number of factors as required. A particle is then assigned to move between vertices in a group by the attractive forces received from other particles on neighbouring objects. Collision is detected when the distance between a pair of corresponding particles becomes very small. Lastly, the proposed algo- rithm has been implemented to show that collision detection can be conducted in real-time.

On the Estimates of Hyperbolic Area Distortion of Quasiconformal Mappings

The distortion property of hyperbolic area of planar quasiconformal mappings is studied in this paper. In the case of radial quasiconformal mappings and angular deformed quasiconformal mappings their hyperbolic area distortions are estimated quite sharply. The result can be applied to judge whether the hyperbolic area of a planar subset is explodable.