基于模具预先补偿法的大幅面CFRP制件形状精度控制方法

针对控制大幅面CFRP制件成型后的形状精度这一关键技术问题,在剪切层法预测变形的基础上提出了一种改进的剪切层变形模拟方法。改进的方法只需少量制件实验数据,通过计算应变曲线曲率确定剪切层厚度,进而较准确地预测了CFRP制件的翘曲变形。基于变形模拟方法建立了一种大幅面CFRP制件形状精度控制方法,这一方法通过将模拟获得的变形不断补偿于初始模具型面来降低最终制件的变形。通过与实验数据的对比,证明了采用控制方法可以有效提高成型制件的精度,降低变形。     

大直径薄壁件的加工工艺研究

加工大直径特种材料薄壁零件极易产生变形问题,本文研究了一种材料为4J32的低膨胀合金的大直径薄壁零件,分析了薄壁零件加工变形主要是由装夹引起,提出采用端面压紧加工内孔和弹性胀套装夹加工外圆,可以有效地保证该零件的加工精度。最后通过对几批零件的质量跟踪,验证了该方法可有效控制零件的椭圆变形。     

CFRP复合材料孔隙形貌特征的统计分析

采用光学显微镜观察和统计分析的方法研究了孔隙率(P)在0.03%～4.96%范围内的16组碳纤维增强树脂(carbon fiber reinforced polymer,CFRP)复合材料中孔隙的平均长度、平均宽度及平均宽长比等参数的变化规律。结果表明:CFRP复合材料的孔隙形貌在整体上呈现统计特性,当孔隙率0.03%≤P0.5%时,孔隙截面接近圆形,孔隙平均长度和平均宽度分别为10～50μm和10～30μm,平均宽长比为0.5～0.8;当孔隙率0.5%≤P3.0%时,孔隙截面逐渐趋向于椭圆形,孔隙平均长度和平均宽度分别为50～70μm和20～30μm,平均宽长比为0.5～0.6;当孔隙率3.0%≤P≤4.96%时,大多数孔隙截面呈现长条形,孔隙平均长度和平均宽度分别为50～100μm和30～40μm,平均宽长比0.35～0.5;同时,CFRP复合材料的孔隙形貌也具有随机特性,不同孔隙率试样之间和同一试样不同部位之间,其孔隙形状、尺寸及分布都可能存在明显差异。     

论大型薄壁件车加工变形质量控制

以某发动机上的某大型薄壁件为研究对象,在数控立车设备上,通过设计专用车加工夹具控制零件变形、选用专用机夹刀具,编制数控加工程序,选择合理的切削参数,控制零件加工中的变形,保证零件从研制到批产的过渡,稳定了工序加工质量,提高了加工效率,解决大型整体薄壁鼓筒类零件加工瓶颈问题,有效地促进大型钛合金薄壁件加工工艺技术水平的进步和提升。     

薄壁零件加工变形控制方法研究

薄壁件具有重量轻、节约材料、结构紧凑等优点,被广泛应用于航空发动机产品中。但航空发动机类零件主要采用高温合金、钛合金等难加工材料,而薄壁零件刚性差,加工易变形,严重影响零件的尺寸与形位精度。本文主要从毛坯、机加工艺、装夹与支撑方式、检测方法等方面就如何更好地控制薄壁零件加工变形进行了系统研究。     

CFRP复合材料加固钢筋混凝土柱偏心受压性能尺寸效应的试验

碳纤维增强树脂（CFRP）复合材料是一种具有轻质、高强和抗腐蚀等优点的新型高性能材料,为了研究尺寸效应对CFRP复合材料布加固钢筋混凝土柱偏心受压性能的影响,本文进行了相关的试验研究。试验共制作了15根尺寸成比例的钢筋混凝土柱试件,试验考虑了构件尺寸、偏心距和CFRP复合材料布加固层数三种因素的影响。试验结果表明:CFRP复合材料布加固钢筋混凝土柱的破坏形态、相对挠度、CFRP复合材料布峰值应变、钢筋峰值应变都存在明显的尺寸效应; CFRP复合材料布加固钢筋混凝土柱的极限荷载随偏心距的增大而减少,尺寸越大,减小趋势越平缓;在相同偏心距下,随着CFRP复合材料布加固钢筋混凝土柱试件截面尺寸的增加,安全储备系数逐渐减小。      

试析薄壁环形件零件加工变形的解决措施

跑道B是安装在转子上,承受着发动机高速旋转时的动力载荷,同时,还要对载荷轴承提供润滑介质。零件的稳定性、材质的致密度要求非常严格。毛坯由自由锻件加工而成,其材料为40CrNiMoA。跑道B外径尺寸为ф160mm,壁厚为4.5mm的薄壁件,其外圆有30处均布的半圆槽。该零件的尺寸精度、公差要求较高,加工难度很大。材料内应力、切削应力、装夹应力带来的零件变形很难控制。为了在现有生产条件下加工出合格产品,我们攻关小组经过半年多的刻苦专研和摸索,通过增加/调整工序内容、更改/制造工装、选择合理的切削参数,最终顺利攻克这一难题。     

柔性薄板件装配误差分析

为简化柔性薄板件装配分析过程和提高计算效率,在自由回弹的基础上,分析在"N-2-1"定位方式下,柔性薄板件夹具偏差经定位夹紧、自由回弹和焊接后对最终装配偏差的影响,建立柔性薄板件装配偏差模型.同时,分析装配过程中外力力矩作用下的偏转所引起的法向变形.最后,用MATLAB结合有限元软件ANSYS进行仿真,与CATIA TAA按传统装配过程分析的结果进行比对,验证装配偏差模型的有效性.     

超声振动辅助铣磨加工对CFRP切削力和表面质量的影响

为研究超声振动辅助铣磨加工对碳纤维增强树脂基复合材料(CFRP)切削力和表面质量的影响,建立了超声振动辅助铣磨加工的切削力模型,进行了磨粒运动轨迹、刀具锋利化效果及单颗磨粒切厚的理论分析及试验验证。结果表明:超声振动辅助铣磨加工与传统铣磨加工相比切削力更小、加工质量更好。当每齿进给量从4μm/z增加到8μm/z时,超声振动辅助铣磨加工的切削力增加了44.7%,小于传统铣磨加工的84.9%;同样,当切深从200μm增加到400μm时,超声振动辅助铣磨加工的切削力增加了187.8%,小于传统铣磨加工的209%;在相同加工参数下,超声振动辅助铣磨加工的工件表面与传统铣磨加工相比,树脂涂覆、表面凹坑和纤维拔出量明显减少。      

小截面方管结构CFRP复合材料的超声检测方法

新型飞行器已采用小截面碳纤维增强树脂基(Carbon Fiber Reinforce Polymer, CFRP)复合材料方管结构。针对该类复合材料方管的材料组成和结构特点,分析和对比了常用的超声穿透法、超声反射法和整体超声穿透法对复合材料方管内部质量检测的适用性,提出了超声对面内壁反射法。采用超声对面内壁反射法对试块中的人工缺陷和实际产品进行检测。结果表明,采用该检测方法能够全部检出试样中的10 mm×10 mm的人工分层缺陷,且可有效地检测实际产品的分层和孔洞缺陷。     

CAD/CAM技术在零件加工中的应用

为研究和推广CAD/CAM技术在加工中的应用,依据CAD/CAM技术基本原理,分析CAD/CAM对机床数控系统的插补功能、刀具补偿功能等的影响,以底座零件加工为例,通过对底座零件的建模和加工过程的详细描述,阐述CAD/CAM技术在零件加工中的应用过程,说明CAD/CAM技术在零件设计和制造中的先进性和优越性。     

三维曲面零件连续柔性成形技术的理论分析与回弹控制

对三维曲面零件连续柔性成形(CFF)新技术中的成形件形状控制、柔性辊轴线形状描述以及回弹等理论问题进行了研究.基于对连续成形过程中板料纵向与横向变形的分析,建立了成形纵向形状控制的理论与方法;结合多点控制的特点,给出了描述柔性辊辊形的样条插值公式;针对板料连续成形中的回弹补偿问题,基于对材料及变形方面的简化与假设,推导...     

Flexible parts feeding for flexible assembly

A key obstacle to the economic application of flexible automation is parts feeding. Traditionally, dedicated devices such as vibratory bowl feeders have performed parts feeding. Such devices have a high cost, and are dedicated to a single component geometry and, consequently, the number of dedicated feeders required for a planned variety of products is equal to the number of distinct part types. This results in a high capital cost that can only be justified in a dedicated mass production environment, where there are long production runs and few product changes. Dedicated feeding methods are also usually too inflexible for robotic assembly systems where there is a wide range of component types in small batches being produced at lower rates. Flexible feeders capable of feeding many different part types are now commercially available but they are invariably large and costly. This paper describes a compact, low cost belt feeder prototype based on Pherson et al.'s (1983) concept but, which is capable of feeding complex geometries using modern sensor technology for part recognition, a standard non-active orientation blade, and a novel method for handling cylindrical parts.     

Method of calculating multilayer flexible polymeric-metallic parts

A method of calculating the stress-strain state of multilayer flexible polymeric-metallic pipes loaded by internal pressure is set forth; it is based on the nonlinear theory of multilayer anisotropic shells. A comparison is made between computed results obtained with and without allowance for the nonlinearity of multilayer flexible polymeric-metallic pipes of high and low radial stiffness. It is established that for flexible pipes of high radial stiffness, which contain one or several frames, the results of strength calculations for an axisymmetric load in accordance with the linear and nonlinear theories are in virtual agreement. The effect of the structural parameters of the frame and longitudinal-bearing components on the bearing capacity and longitudinal flexibility of multilayer flexible polymeric-metallic pipes is demonstrated.Translated from Problemy Prochnosti, No. 2, pp. 62–66, February, 1991.     

Rotary ultrasonic machining of CFRP/Ti stacks using variable feedrate

Rotary ultrasonic machining (RUM) has been successfully used to drill Ti (titanium and its alloy), CFRP, and CFRP/Ti stacks. In all studies on RUM reported in the literature, feedrate was fixed during each experimental test. It has been shown that low feedrate should be used for RUM of Ti, but RUM of CFRP could be done using feedrate 10 times higher. This paper, for the first time, reports a study on RUM of CFRP/Ti stacks using variable feedrate (high feedrate for CFRP and low feedrate for Ti). It also makes comparisons on RUM of CFRP/Ti stacks using fixed and variable feedrate.     

Setup planning for machining the features of prismatic parts

This paper focus on the development of a formalized procedure for automatic generation of feasible setups and then to select an optimal setup plan for machining the features of a given prismatic part. The proposed work simultaneously considers the basic concepts of setup planning from both machining and fixturing viewpoints in order to formulate feasible setup plans. The tasks that are performed are: (a) identifying groups of features that can be machined in a single setup, (b) determining a suitable work piece orientation, i.e. the suitable datum planes for each setup, (c) determining all the feasible setup plans to machine the given set of features of prismatic parts, and (d) evaluating the feasible setup plans on the basis of technological (available tolerance) and economical conditions (total setup time). For the proposed work the authors have introduced four new concepts namely, ‘surface fit for location’, ‘primary group’ ‘secondary group’, and ‘eligible group’. The first concept plays an important role in the identification of suitable faces of the part for positioning, clamping and supporting. The other three help in clustering of features, which can be converted in to candidate setups.