Improvement in stage measuring technique of the ultrasonic sensor gauge

Bar check is the routine procedure in depth sounding to eliminate temperature influencing effect during the oceanographic surveying. This paper adopted the bar check concept prior to stream stage measuring on-site to improve the measuring accuracy and efficiency with popular ultrasonic sensor gauges. This study also propose both experimental dimensionless curves/corresponding equations and the relative profile of calibrating coefficients and ambient temperature of the specific ultrasonic sensor to accelerate the field calibrating process and for the bar check calibrating procedure being unavailable before the formal stage measuring. Then, field stage measuring data by a float-type gauge with which relative reliable measuring result being identified were compared with the data by an ultrasonic sensor gauge measuring simultaneously at the same location and obtained quite similar results. This advanced and improved stage measuring technique of ultrasonic sensor gauges without sonic conduit has been proved its practical validity in field stage accurate measuring throughout the on-site bar check procedure and introduced the process with dimensionless curves/formulas and relative correlation profile between calibrating coefficients and ambient temperature as well.     

Numerical modeling and experimental study of thermally induced residual stress in the direct diode laser heat treatment of dual-phase 980 steel

The direct diode laser application has been found useful in the localized heat treatment of metal parts because of its wider beam and more uniform energy distribution with respect to other lasers with Gaussian-like energy distribution. In this study, an uncoupled thermomechanical finite element model is developed to study the temperature field and thermally induced stress evolution in high-strength dual phase (DP) 980 steel during its direct diode laser heat treatment. Thermal analysis results are experimentally validated through thermocouples and then input into a mechanical model as transient temperature loading in order to acquire the thermally induced stresses and strains. The effect of martensite phase transformation on residual stress distribution in heat-treated DP980 steel is considered. An X-ray diffraction technique is used to measure the residual stress distribution at the top surface of the heat-treated coupons of DP980 steel. The numerical results show that compressive stresses are located at the laser–material interaction zone. After heat treatment, tensile stresses are retained at the heat-treated DP980 steel coupons. There is qualitative agreement between the numerically predicted and experimentally measured residual stresses. The effect of the overlapping ratio on the residual stress and hardness of the heat-treated DP980 steel is also experimentally and numerically investigated.     

利用蠕变等损伤曲线研究蠕变累积损伤

利用蠕变损伤的剩余寿命定义，构造了蠕变等损伤曲线，并给出蠕变等损伤曲线的近似数学描述。通过蠕变等损伤曲线研究了蠕变累积损伤规律，建立蠕变累积损伤公式。利用该公式估算变载蠕变剩余寿命，仅需要材料的蠕变断裂曲线，十分便利。     

半切顶插齿刀的精确设计和Y7125半切顶角度的调整计算

用平面啮合原理通俗地介绍了目前广泛应用的半切顶插齿刀的设计方法与步骤,导出了半切顶插齿刀主切削刃与半切顶切削刃的交点半径的通用计算公式,从而解决了半切顶插齿刀的精确设计,和半切顶齿形的测量。从Y7125型磨齿机的磨齿原理进行分析,从设计半切顶插齿刀中所获得的两个基圆中,求取磨制半切顶插齿刀的半切顶修整角的调整。     

变速传动轴承内齿圈齿廓方程的分析

根据变速传动轴承中推杆传动装置的相对运动原理及法向等距线的性质,提出了一种通过内外滚子工作角关系求内齿圈齿廓的方法及其适有的计算公式。这种方法比传统的包络法简便,概念清楚,对变速传动轴承内齿圈的廓形加工,具有重要的指导意义。     

K形齿的插齿修形方法

针对插齿加工过程中K形齿的修形问题 ,根据插齿刀的设计原理和基本特点 ,提出了以改变插齿刀的前角和前刀面形状来改变切削刃在其基面上的投影 ,达到在插齿加工中对齿形的修形的目的。推导出了有关公式 ,列举了应用实例。     

Dynamic tensile characteristics of TRIP-type and DP-type steel sheets for an auto-body

This paper is concerned with the dynamic tensile characteristics of transformation-induced plasticity (TRIP)-type and dual phase (DP)-type steel sheets at intermediate strain rates ranging from 0.003 to 200 s⁻¹. The dynamic responses of TRIP600, TRIP800, DP600 and DP800 steel sheets are investigated with the evaluation of stress–strain curves, the strain rate sensitivity, the fracture elongation and the effect of pre-strain. The dynamic responses were acquired from dynamic tensile tests at the intermediate strain rates with a high-speed material testing machine developed. Experiments were carried out with specimens whose dimensions were carefully determined by finite element analyses and experiments to induce uniform deformation in the gauge section at the intermediate strain rates. The tensile tests provide stress–strain curves and the strain rate sensitivity. Experimental results show two important aspects for TRIP-type and DP-type steel sheets quantitatively: The flow stress increases as the strain rate increases and the fracture elongation and the formability of TRIP-type sheets are better than those of DP-type sheets at the intermediate strain rates. The pre-strain effect was also investigated for two types of metals at the intermediate strain rates. TRIP600 and DP600 steel specimens pre-stained by 5% and 10% were elongated at the strain rate of 0.003 s⁻¹ for quasi-static loading, and then tested at strain rates of 0.003, 1, 10 and 100 s⁻¹. The results demonstrate that the mechanical properties of TRIP600 and DP600 steels are noticeably influenced by the pre-strain when the strain rate is over 1 s⁻¹. The ultimate tensile strength as well as the yield stress increases due to the pre-strain.     

Development of radially movable multichannel Reynolds stress probe system for a cylindrical laboratory plasma

A new radially movable multichannel azimuthal probe system has been developed for measuring azimuthal and radial profiles of electrostatic Reynolds stress (RS) per mass density of microscale fluctuations for a cylindrical laboratory plasma. The system is composed of 16 probe units arranged azimuthally. Each probe unit has six electrodes to simultaneously measure azimuthal and radial electric fields for obtaining RS. The advantage of the system is that each probe unit is radially movable to measure azimuthal RS profiles at arbitrary radial locations as well as two-dimensional structures of fluctuations. The first result from temporal observation of fluctuation azimuthal profile presents that a low-frequency fluctuation (1-2 kHz) synchronizes oscillating Reynolds stress. In addition, radial scanning of the probe system simultaneously demonstrates two-dimensional patterns of mode structure and nonlinear forces with frequency f = 1.5 kHz and azimuthal mode number m = 1.     

铁素体晶粒尺寸对铁素体—马氏体双相钢DP980动态变形行为影响

为了研究铁素体晶粒尺寸对铁素体—马氏体冷轧双相钢DP980动态变形行为的影响,通过连续退火试验,得到两组马氏体体积分数相同、而铁素体晶粒尺寸不同的试样。选取应变速度为1×10-4s-1和1×10-2s-1进行准静态拉伸试验;选取应变速度为500 s-1、1 000 s-1和1 750 s-1在分离式霍普金森拉杆(Split Hopkinson tensile bar,SHTB)上进行动态拉伸试验。使用不考虑晶粒尺寸影响的Johnson-Cook(J-C)率相关模型和考虑晶粒尺寸影响的修正的Khan-Huang-Liang(KHL)率相关模型分析双相钢的动态变形行为,并引入可决系数R2来判定试验结果与模型的吻合关系。分析结果得出修正的KHL模型与试验结果吻合较好,其可决系数R2达到了0.998 7,表明修正的KHL模型可以很好地描述DP980材料在低应变速度和高应变速度下的变形行为,能够反映铁素体晶粒尺寸对DP980动态变形行为的影响。     

基于极坐标系的数据插补算法的椭球宏程序的应用

数控机床具有能实现两轴或者多轴联动、极大地减少了工装夹具运用并提高了生产效率与加工精度的特点,但在正常情况下,用数控机床加工除圆弧以外的轮廓线,如圆锥曲线、三角函数曲线等复杂轮廓线,手工编程得到的曲线的拟合精度不满足加工要求。针对这个问题,研究了基于极坐标系的数据插补算法在宏程序加工中的应用,并以椭球的宏程序加工为例,给出了加工步长的算法。通过使用这种数据插补算法,加工效率和精度得到了最大提高,并且对零件改型的适应性也相应增强。     

Field emission from diamond particles studied by scanning field emission microscopy

Field emission properties from diamond particles (DPs) are studied. The DPs with thin chemically vapor deposited (CVD) diamond overcoat, dispersed onto metal substrate, essentially exhibit negative electron affinity (NEA). Field emission, approximately 1mA/cm(2) under a macroscopic electric field of 3.5kV/mm are observed. Microscopic electrical properties were studied by scanning tunneling microscopy/spectroscopy. Most parts of the DP surface exhibit narrow gap and p-type characteristics. The localized regions, which have wide gap like bulk diamond properties, are randomly distributed near the top of DP. The field emission current distribution depicted by scanning field emission microscopy (SFEM) show that the electron emission is originating from a localized region on the selected DPs. We found, through SFEM measurement, some favorable field emission spots ("hot spots") where measured emission current is several orders higher than that of the other DPs ("normal spots"). Field emission spectroscopy (FES) results suggest that a poorly conducting layer is present along the electron path from the metal electrode to vacuum.We propose two models for field emission from "hot spots", which involve two main mechanisms. One is electron injection from the metal substrate to the DP, which is attributed to the electric field enhancement at intrinsic non-doped diamond (i-diamond) layer sandwiched between the metal substrate and the surface conductive layer (p-diamond) of the CVD diamond overcoat on the DP. The other is electron emission at the top site of NEA DP through the local i-diamond region or the depletion region of the p-diamond, which is caused by the applied electric field.     

摆动滚子从动件圆柱凸轮参数化设计

推导了摆动滚子从动件圆柱凸轮廓线、压力角及廓线曲率半径方程,讨论了该种凸轮机构在各种运转情况下与之相适用的方程。并将方程用于凸轮廓线的参数化设计,通过实例验证该方法在实际应用中具有一定的实用价值。     

万向十字轴轴根过渡结构的优化设计和分析

提出变曲率过渡曲线理论,单纯从形状上寻求应力集中系数小的万向十字轴轴根过渡曲线。将双曲率圆弧曲线、椭圆曲线和流线形曲线作为万向十字轴轴根过渡曲线来降低应力集中从而提高万向十字轴的使用寿命;建立了三种过渡曲线的曲线方程,给出双曲率圆弧过渡曲线、椭圆弧过渡曲线及流线形曲线的设计实例,并进行了有限元分析。结果表明提出的三种曲线可以有效降低万向十字轴轴根的应力集中。     

A study of the crushing of tubes by two indenters

The behaviour of mild steel open tubes loaded centrally by two opposed wedge-shaped indenters is examined. The 1.6 mm thick tubes have diameters ranging from 31.75 to 76.2 mm and lengths from 1.6 to 10 diameters. The load-deflection curves have been recorded and simple empirical formulae are obtained for them. The profiles of the deformed top generators for tubes of 10 diameters length are reported and they are found to collapse into a single curve in a suitable dimensionless plot. The observed profile is related to the force by means of a beam-foundation model. Similar empirical formulae are reported for tubes enclosed at both ends with “rigid” plates.     

残余应力对齿轮弯曲疲劳的量化影响研究

随着风电、高铁、掘进等高端装备对齿轮功率密度、服役寿命等要求的提高,齿轮的弯曲疲劳问题日益显著。为提升齿轮弯曲疲劳性能,通过渗碳热处理、喷丸强化等工艺为齿轮引入较高的残余压应力已逐渐成为工业界的标配。为揭示残余应力对齿轮弯曲疲劳性能的量化影响,在最大主应变寿命预测准则中引入残余应力影响项,通过弯曲疲劳试验确定最优残余应力影响系数,进而采用新的试验数据验证模型的准确性。基于工程应用出发,引入修正应力的概念统一不同残余应力状态下的齿轮弯曲应力-寿命(S-N)曲线,研究结果显示,最大主应变准则中,残余应力影响系数取值为0.15时,可实现较高的寿命预测精度,而修正的S-N曲线中,最佳残余应力影响系数为0.25。研究成果可用于工程实际中齿轮弯曲疲劳快速评估。     

渐开线齿轮单齿啮合区的齿形系数

本文对范成法加工的渐开线圆柱齿轮，在单对齿啮合受载时，按轮齿危险截面形状（分平截面法和折截面法）、加工方法（分齿条刀类和插齿刀类），给出四组齿形系数的计算式。此式既可计算标准（或非标准）齿轮齿顶受载时的齿形系数，又可计算标准（或非标准）齿轮齿廓任意点受载时的齿形系数，还可计算具有非标准齿廓参数的渐开线齿轮任意点受载的齿形系数，为精确计算轮齿齿根弯曲强度提供了依据。     

摆线针轮行星传动中摆线轮最佳形量的确定方法

在对摆线针轮行星传动中摆线轮的修形方式进行分析的基础上,提出了最佳修形齿廓的概念,对采用"负移距+正等距"修形方法获得最佳修形齿廓原理进行了探讨, 推导出了摆线轮最佳修形量的计算公式.采用新齿形的样机试验结果也证明了修形理论的正确性.     

Note: A time-resolved Kerr rotation system with a rotatable in-plane magnetic field

A time-resolved Kerr rotation system with a rotatable in-plane magnetic field has been constructed to study anisotropic spin relaxation of electrons in semiconductors. A permanent magnet magic ring is placed on top of a motor-driven rotation stage (RS) to create the rotatable in-plane magnetic field. The RS is placed on a second translation stage to vary the local magnetic field around a sample. The in-plane magnetic field in such a system varies from 0.05 to 0.95 T, with full-round 360° rotatablity, thus offering a convenient and low-cost way to study the anisotropy of spin dynamics in semiconductors. Its performance was demonstrated via measurement of the anisotropy of the spin dephasing time (SDT) of electrons in a two-dimensional electron system embedded in a GaAs/Al(0.35)Ga(0.65)As heterostructure. The SDT with B∥[110] was observed to be 10% larger than that with B∥[110], consistent with the results of others, which was measured via rotating sample.     

蓝牙高级音频分发框架协议的研究与实现

通过对蓝牙高级音频分发框架（A2DP）协议栈进行系统地分析，提出了一种基于消息机制的协议方案，在无A2DP框架的蓝牙1．1协议栈基础上实现了轻型的A2DP应用框架，并且利用嵌入式蓝牙开发平台，实现了基本的点对点蓝牙立体声音频数据的传输。     

A newly developed rotor profile for lobe pumps: Generation and numerical performance assessment

This study develops a new lobe pump rotor profile that significantly improves pump performance. Rotor profiles including two traditional designs and two new designs consist of three segments that are generated by circular or/and epicycloidal curves. This study evaluates the performance of four profiles via volume calculation and flow field analysis, considering to the number of lobes. Results demonstrate that the shapes of rotor surfaces affect pump performance remarkably. An epicycloidal profile provides a much advantage than a circular profile. The new rotor profile with three segments was generated by the curves in order of epicycloidal-circular-epicycloidal (ECE profile) obtained performance of 55% higher than the traditional profiles and the order of circular-epicycloid-circular (CEC profile). The analysis in this study also proves that a multi-lobe design of three or four lobes does not increase pump performance, but provides a more stable output and higher capacity than a two-lobe pump.