内燃机曲轴扭转疲劳强度试验研究与分析

通过对内燃机曲轴进行扭转疲劳试验研究,分析了影响曲轴扭转疲劳强度的因素以及导致曲轴扭转失效的原因,并提出了相应的改进措施。分析指出,随内燃机爆发压力的提高,曲轴所承受的扭矩会相应增大,由此导致的曲轴扭转疲劳失效不断增加。曲轴扭转失效位置主要在连杆颈油孔、曲柄臂和连杆颈下止点,失效原因涉及结构设计、原材料、机加工、热处理等多个因素。连杆颈油孔是扭转疲劳失效最常见部位,裂纹源一般在油孔内壁距轴颈表面约8～10 mm位置,轴颈表面感应淬火对扭转疲劳强度影响较大,表面感应淬火使曲轴的扭转疲劳强度降低约30%,油孔内壁抛磨可使轴颈表面淬火曲轴的扭转疲劳强度提高25%以上。     

Influence of inclined holes in measurement of residual stress by the hole drilling method

The hole drilling method is widely used in measuring residual stress in surfaces. In this method, the inclination of holes is one of the sources of error. This paper presents a finite element analysis of the influence of inclined holes on the uniaxial residual stress field. The error in stress has been found to increase proportionally to the correct inclined angle of the hole. The correction equations by which one may easily obtain the residual stress, taking account of the inclined angle and direction, have been derived. The error of stress due to the inclined hole has been reduced to around 1% using the correction equations.     

基于Faster R-CNN的工件螺纹孔目标检测

为了提高螺纹孔目标检测的准确率,结合双相机视觉系统与Hough变换圆检测算法,提出了一种基于Faster R-CNN的螺纹孔目标检测方法。首先建立了由双相机组成的图像获取系统,通过安置在高处的工业相机采集工件整体图像,利用Hough变换圆检测算法初步筛选出工件上的疑似螺纹孔的位置,并驱动第二个工业相机逐个在近处采集经Hough变换检测出的疑似螺纹孔的局部精确图像。然后,在自建的螺纹孔数据集上训练以ResNet50为基础网络的Faster R-CNN目标检测模型。最后,将螺纹孔处局部图像输入训练好的Faster R-CNN目标检测模型进一步识别并进行定位。实验结果表明,该方法能有效地避免螺纹孔小目标检测,相对于单独使用Hough变换方法或者Faster R-CNN目标检测方法检测螺纹孔,具有更高的识别和定位精度。     

复合管金属增强体结构优化设计

根据应力分析模型并借助于有限元分析，研究了在复合管增强体内表面施加均匀径向载荷后表面的应力分布；对直径为5lmm具有不同孔隙率与排布方式的薄壁钢管中的应力场进行了模拟。结果表明，孔隙率不变的情况下改变增强体上孔排布方式，可以获得均匀分布的的表面应力和应变；在满足强度要求的情况下，孔隙率可以比原设计提高25％。     

Flow and heat transfer measurements of film injectant from a row of holes with compound angle orientations

An experiment has been conducted on the flow and heat transfer characteristics of film coolant injected from a row of five holes with compound angle orientations of 35° inclination angle and 45° orientation angle. The Reynolds number number based on the mainstream velocity and injection hole diameter 3.58 x10⁴. Three-dimensional velocity, film cooling effectiveness and heat transfer coefficient data are presented at three different mass flux ratios of 0.5, 1.0 and 2.0. Flow entrainment has been found between the vortices generated by adjacent injectants. The injectant with compound angle orientation entrains not only the mainstream boundary layer flow but also the adjacent injectant. Because of the flow entrainment, the injectant. With compound angle orientation is characterized by a single vortex while two bound vortices are usually observed in the case of simple angle injection. The strength of the secondary flow depends strongly on the mass flux ratio, which shows significant influence on the film cooling effectiveness and heat transfer coefficient.     

Apparatus to test insertion and removal torque of bone screws

This paper describes affordable equipment for testing bone screw torque, corresponding to ASTM standard F543-00 for testing metallic medical bone screws. Correct testing of thin and long bone screws is essential due to screw failures during insertion and removal of the screws. Furthermore, insertion torque is an important factor in predicting fixation strength, screw pull-out force and effects of surface treatment of screws. The capability of the custom-built tester was determined using polytetrafluoroethylene and wood disc samples and bone screws. Bovine cortical bones allowed testing to the failure limit, i.e. the torque increased in long screws to the fracture limit. For 2.7 and 3.5 mm thick self-tapping cortical bone screws, the failure torques were 30-50 per cent higher than the minimum values required by the standard (1.0 and 2.3 N m respectively). The equipment provided reproducible results and fulfilled the ASTM standard very well. Preliminary testing with amorphous diamond coated bone screws showed good durability of the coating and on average 10-15 per cent lower torque values compared with uncoated screws. The equipment can be used to measure insertion and removal torques as described in the standard. Furthermore, it also allows testing of normal screws and bolts.     

Optimizing the configuration of cement keyholes for acetabular fixation in total hip replacement using Taguchi experimental design

Cement fixation of the acetabular component is increasingly recognized as a common site of loosening when hip replacements fail. Cement keyholes drilled into the acetabulum have been recommended to improve this fixation but little is known of the optimum positions or sizes of these holes. This study investigates the diameter, depth and number of keyholes to be drilled to maximize the failure torque in a model system. A Taguchi experimental design was used to identify the most significant factors and to predict the best configuration of keyholes within the constraints of the experimental test rig. One hole at each of the pubic, iliac and ischial sites, of 12 mm diameter and 6 mm depth, was found to be the optimum configuration. The failure torque was most strongly dependent on the hole diameter in the pubic region, decreased with increasing hole depth and was not sensitive to the number of holes.     

Discharge coefficients of Venturi tubes with standard and non-standard convergent angles

This paper describes twenty one Venturi tubes manufactured in a range of diameter ratios from 0.4 to 0.75. Fifteen of them are standard, with a convergent angle of 21°, manufactured in a range of diameters from 50 mm to 200 mm and of diameter ratios from 0.4 to 0.75. Six are standard except for the convergent angles which are either 10.5° or 31.5°; they are of diameter 100 mm. They have all been calibrated in water and high-pressure gas. For the standard Venturi tubes an equation for the discharge coefficient in water has been obtained with an uncertainty of 0.74 per cent. Work on the physical basis of the equation for the discharge coefficient at high Reynolds number is described, and an equation fitting all the gas data from the standard Venturi tubes with an uncertainty of 1.23 per cent has been derived. It is clear that the data in gas from the Venturi tubes with a convergent angle of 10.5° are much smoother than those from Venturi tubes with the standard or the higher convergent angle: an equation fitting all the gas data from the three Venturi tubes with a convergent angle of 10.5° has been obtained with an uncertainty of 0.71 per cent.     

Analysis of silicon via hole drilling for wafer level chip stacking by UV laser

For stacking wafers/dies, through-silicon-vias (TSVs) need to be created for electrical connection of each wafer/die, which enables better electrical characteristics and less footprints. And for via hole processing, chemical methods such as DRIE (Deep Reactive Ion Etching) are mostly used. These methods suffer the problems of slow processing speed, being environment-unfriendly and damage on the existing electric circuits due to high process temperature. Furthermore, masks are also needed. To find an alternative to the methods, researches on the laser drilling of via holes on silicon wafer are being conducted. This paper investigates the silicon via hole drilling process using laser beam. The percussion drilling method is used for this investigation. It is also examined how the laser parameters- laser power, pulse frequency, the number of laser pulses and the diameter of laser beam- have an influence on the drilling depth, the hole diameter and the quality of via holes. From these results, laser drilling process is optimized. The via hole made by UV laser on the crystal silicon wafer is 100μm deep, has the diameter of 27.2μm on the top, 12.9μm at the bottom. These diameters deviate from the target values by 2.8μm and 0.4μm respectively. These values correspond to the deviation from the target taper angle of the via hole by less than 1°. The processing speed of the laser via hole drilling is 114mm/sec, therefore, etching process can be replaced by this method, if the number of via holes on a wafer is smaller than 470,588. The ablation threshold fluence of silicon is also determined by a FEM model and is verified by experiment.     

Fabrication of stepped hole on zirconia bioceramics by ultrasonic machining

Zirconia (ZrO₂) is a highly biocompatible ceramic material providing fracture strength properties that allow application as dental implants in biomedical engineering. In this present research, experimental analysis has been made for generating stepped hole on zirconia bioceramics with desired quality using ultrasonic machining (USM) process. Four independent controllable input process parameters are abrasive grain diameter, power rating, concentration of abrasive slurry, and tool feed rate. Material removal rate (MRR), overcut of larger diameter (OLD) hole, and overcut of smaller diameter (OSD) hole of stepped hole are considered as the responses. Response surface methodology (RSM) is used for modeling the performance of USM process. Multiobjective optimization has been performed to maximize the MRR and minimize the OLD hole and OSD hole of stepped holes. All the responses are improved at the optimal parametric condition and verified by confirmation test. The present research opens up the application feasibility of USM process for stepped hole generation on bioceramics and its utilization in biomedical field.     

颗粒饲料加工中数控环模阻塞修复系统的设计

环模在颗粒饲料加工机械中是一个容易阻塞的核心部件,为了解决现有人力在清堵环模时存在的修复效率低、修复效果差等问题,设计了一种数控环模阻塞修复系统。该系统以ATmega128L为核心,搭建了小型μC/OS-II操作系统;系统采用电机细分驱动配合霍尔传感器完成模孔的精确识别和定位;通过接近开关完成模孔的换行,采用加减速运动控制步进电机带动钻头完成清堵。经过现场调试及应用表明,数控环模阻塞修复系统模孔的定位误差在0.427 mm以内,且平均每小时修复模孔1 086个,模孔疏通成功率为99.8%,刮伤模孔概率为0.11%。     

Laser Cutting of Holes in Inconel 803 Alloy and Analysis of Thermal Stress Field

Laser circular cutting of Inconel 803 alloy is carried out. Temperature and stress fields are predicted in the cutting section using ABAQUS finite element code mimicking the experimental conditions. To examine the influence of the hole diameter size on the thermal stress field developed in the cutting section, 2?mm and 10?mm hole diameters are considered in the experiments and analysis. Temperature predictions are validated through the thermocouple data. Morphological and elemental changes in the cutting section are examined incorporating the analytical tools. It is found that laser cut holes are free from large size asperities such as cracks and excessive sideways burnings. However, few small dross attachments are observed at the kerf exit for the small diameter (2?mm) hole. The maximum temperature is higher for small diameter hole than that of the large diameter hole (10?mm) prior to cutting ceases, which is attributed to heat transfer rates from kerf site to its neighborhood. von Mises stress remains low in the region where temperature remains high in the cooling period. This is associated with the elastic modulus of the substrate material, which reduces with increasing temperature. von Mises stress becomes almost same for small and large diameter holes after the cooling period ends and it is in the order of 0.45?GPa.     

Development of a laser-guiding-type deep small-sized hole-measurement system: Measurement accuracy

In this study, a system for measuring small-sized holes with a 17–21 mm diameter and 1000 mm length was constructed. The system comprises a laser interferometer to detect hole accuracy, a probe connected to a measurement bar, and an optical apparatus for detecting the probe attitude (position and inclination). The probe was supported by supporting pads. A steel workpiece with 18 -mm diameter and 800 mm length was used for the performance test. During the experiment, errors were found in terms of hole deviation and roundness profile. Further experiments, using new experimental apparatus and analysis, revealed the causes of errors: electrical noise that increased with time, two periodic stylus swings in the longitudinal direction of the hole per rotation of the measurement unit, and the excessive spring force pushing the tip of the stylus, causing a large frictional force with the hole wall, etc. If these errors are corrected, high accuracy in the measurement of hole deviation and roundness can be achieved.     

平板传热对气膜冷却的影响

对不同平板厚度的圆柱孔平板气膜冷却模型进行了数值研究,其中冷却空气入射角均为35°,湍流模型采用Standardk-ε湍流模型。所研究的模型分为单孔模型和排孔模型,板的厚度分为4mm、2mm及0mm。文章的重点在于分析平板的传热对气膜冷却效果的影响,研究结果显示气膜冷却效率沿主流方向逐渐降低,当吹风比为0.8时冷却效率最高,平板内部导热对气膜冷却效率及平面温度分布有较大影响。     

大型箱体特大孔调头镗削工艺技术

采用普通铣镗床TPX6113-2加工大型箱体特大孔的调头镗削工艺综合了普通工艺装备与新技术,采用特殊装夹定位工艺方法,减少了反复装夹次数,保证了工件装夹定位的牢固性。设置辅助工艺基准点、线、面与数字的等量关系,控制等量误差精度,保证大孔调头后孔系加工中的同轴度。用平旋盘大孔镗刀架加工特大孔1 120+0.2+0.1和960+0.15+0.05mm的工艺与实践解决了中小型机床设备加工大型工件时,装夹定位难的问题和调头后定位难保证同轴度的问题。     

Mechanical testing of the wire clamping characteristics of the Fixclip internal fixation system

Stainless steel wires (Kirschner's wires) have been used for over 60 years to fix internally a wide range of osteotomies and fractures in bones. Fixclips (Corifix, Cirencester, UK) shaped like winged washers have been used to clamp pairs of K wires of diameters ranging from 0.8 to 3.0 mm to standard orthopaedic screws and to fix bones internally in more than 400 patients. The system has proved to be biologically and mechanically very effective. This paper describes the design and some biomechanical test results of the Fixclip. Preliminary strength tests conducted using a Hounsfield Tensometer show that the pull-out force, reflecting the grip of the clip on the wire, is dependent on the wire size and, throughout the clinically relevant range, increases linearly with increasing screw torque. Changing the surface finish of the clip did not confer any advantage over the existing polished clip in terms of grip strength.     

一种新型大推力直线压电作动器

设计了一种新型大推力直线压电作动器,采用螺旋箝位的方式实现对压电叠堆微小位移的累积输出,实现了大推力和长行程。对该种作动器的驱动机理和作动器设计过程中的关键技术问题进行了详细的分析,包括力矩电机的转速设计、上下柔性联轴器的扭转刚度设计、螺母和丝杠之间相关机械参数的设计以及对所选压电叠堆进行性能测试并选择其最佳工作频段。原理样机长为140 mm,最大直径为45mm,重量为0.7 kg,行程为40 mm。在力矩电机转速为300 r／min,压电堆驱动频率为100 Hz时,作动器的最大输出力可达130 N。     

Electrochemical Drilling of Inconel Superalloy with Acidified Sodium Chloride Electrolyte

The performance of modern air engine components such as turbine rotor and stator assemblies depends on a very large number of small holes, with diameters and aspect ratios in the range of 1–4 mm and 40–200, respectively. These high-temperature components are made of difficult-to-machine superalloys such as inconel. Shaped tube electrolytic machining (STEM) appears to be the preferred technique for drilling cooling holes in turbine blades. A review of the literature shows that the dynamics of STEM for deep hole drilling have not been sufficiently investigated. Guidelines for the selection of operating parameters such as voltage, electrolyte flowrate, and tool feedrate are not available. The objective of the present investigation has been to optimise the operating parameters of STEM such as voltage and tool feedrate using high-speed steel (HSS). The optimised parameters have then been used for drilling holes in inconel. Experiments show that good holes can be obtained by a combination of low voltage and comparatively high feedrate which results in low values of equilibrium inter-electrode gap. A good, uniform hole with an aspect ratio of 11 was obtained in inconel at voltage and tool feedrate of 17 V and 1.0 mm min _1 , respectively. Results also point to the need for using dummy workpieces above and below the workpiece for obtaining uniform hole diameter, specifically at the ends.     

精密步进滚珠丝杠副的研制

本文主要阐述精密步进滚珠丝杠副的工作原理、结构设计、制造工艺及精度检验.本文阐述的步进滚珠丝杠副已应用于北京质子加速器的束流测量系统中.步距为055mm;步距精度为0.01mm;步进速度为6mm/s.该滚珠丝杠副是双螺母外循环方式的,循环组数为1组2.5圈.丝杠直径为20.5mm;导程为5mm;滚珠直径为3,175mm;定位精度为4.7μm;复位精度为2.0μm.     

某斜盘式柱塞泵柱塞颈部结构参数计算及仿真分析

柱塞颈部断裂是柱塞体主要损坏形式之一,其直径值对柱塞强度和寿命有重要影响。目前柱塞颈部直径主要通过文献中经验公式来确定,通过试验进行检验,若发生故障,则重新修正该尺寸值。以某型号斜盘式液压柱塞泵为例,以不影响滑靴转动角度与保证柱塞强度为目标,对柱塞颈部直径进行计算,得到柱塞颈部最小允许直径与最大允许直径,并通过ANSYS进行仿真分析,得到仿真应力结果,对比后得出,柱塞颈部直径与柱塞体直径的比例值与目前文献中的经验公式并不一致。