五轴数控加工叶轮轮毂曲面刀位轨迹的规划

对整体叶轮轮毂面的刀位轨迹排布进行了研究.首先运用分层的思想和旋转法得到均布于等长叶片叶轮轮毂面上的刀位轨迹;并在其基础上采用区域划分法对交错叶片叶轮轮毂曲面的刀位进行规划,得到C1连续的刀位轨迹.     

单晶硅超精密磨削过程的分子动力学仿真

对内部无缺陷的单晶硅超精密磨削过程进行了分子动力学仿真,从原子空间角度观察了微量磨削过程,解释了微观材料去除、表面形成和亚表面损伤机理,并分析了磨削过程中的磨削力和磨削能量消耗。研究表明:磨削过程中,在与磨粒接触的硅表面原子受到磨粒的挤压和剪切发生变形,堆积在磨粒的前方,当贮存在变形晶格中的应变能超过一定值时,硅的原子键断裂,即完成了材料的去除;随着磨粒的运动,磨粒前下方的硅晶格在磨粒的压应力作用下晶格被打破,形成了非晶层,非晶层不断向前向深处扩展,造成了单晶硅亚表面的损伤;同时部分非晶层原子在压应力的作用下与已加工表层断裂的原子键结合,重构形成已加工表面变质层。     

A coupled dynamics,multiple degree of freedom process damping model,Part 2: Milling

Self-excited vibration, or chatter, is an important consideration in machining operations due to its direct influence on part quality, tool life, and machining cost. At low machining speeds, a phenomenon referred to as process damping enables stable cutting at higher depths of cut than predicted with traditional analytical models. This paper describes an analytical stability model for milling operations which includes a process damping force that depends on the surface normal velocity, depth of cut, cutting speed, and an empirical process damping coefficient. Model validation is completed using time domain simulation and milling experiments. The results indicate that the multiple degree of freedom model is able to predict the stability boundary using a single process damping coefficient.     

精化齿坯热锻工艺浅析

齿坯闭式模锻锻件分精密级和普通级,但国家标准定义的精密级锻件留有单边加工余量,仍需进行粗车和精车。在精密锻造基础上,研究精化齿坯热锻工艺,以进一步提高锻件精度等级,达到减少单边加工余量,进而使精化齿坯直接用于精车。本文对精化齿坯热锻工艺进行了定义,并明确该工艺单边加工余量的范围。因制坯和预锻是决定精化齿坯热锻工艺质量的关键,因此对其工艺流程和工艺重点进行了分析,同时对满足该工艺的设备和模座进行了论述。     

An experimental investigation on the process parameters influencing machining forces during milling of carbon and glass fiber laminates

Milling is the most feasible machining operation for producing slots and keyways with a well defined and high quality surface. Milling of composite materials is a complex task owing to its heterogeneity and the associated problems such as surface delamination, fiber pullout, burning, fuzzing and surface roughness. The machining process is dependent on the material characteristics and the cutting parameters. An attempt is made in this work to investigate the influencing cutting parameters affecting milling of composite laminates. Carbon and glass fibers were used to fabricate laminates for experimentations. The milling operation was performed with different feed rates, cutting velocity and speed. Numerically controlled vertical machining canter was used to mill slots on the laminates with different cutting speed and feed combinations. A milling tool dynamo meter was used to record the three orthogonal components of the machining force. From the experimental investigations, it was noticed that the machining force increases with increase in speed. For the same feed rate the machining force of GFRP laminates was observed to be very minimal, when compared to machining force of CFRP laminates. It is proposed to perform milling operation with lower feed rate at higher speeds for optimal milling operation.     

An error control approach to tool path adjustment conforming to the deformation of thin-walled workpiece

Producing an accurate part mainly depends on the position and orientation of the cutting tool with respect to the workpiece which is mainly influenced by the rigid body motion of the workpiece and the elastic deformation of workpiece-fixture-cutter system. For the purpose of minimizing the machining error, a new modification strategy of the nominal tool path is not that directly compensate the control commands of the machine tools, but that modify the cutter location source file (CLSF) from the computer aided manufacturing (CAM) system by means of the proposed modification model on the basis of the prediction deviation, namely, the deviation of the cutting tool relative to the workpiece in computer numerical control (CNC) machining operation. Therefore, it is not only simpler, but also easier implemented by common manufacturing engineer. The effectiveness of the proposed strategy is verified by a machining example.     

Investigating the effect of machining processes on the mechanical behavior of composite plates with circular holes

The influence of the machining quality on the mechanical behavior of CFRP composites is yet not fully understood. There are only few works in the literature that have investigated the effect of the machining quality on CFRP. In fact, most of these works focus only on conventional machining such as axial or orbital drilling. The aim of this paper is to examine the influence of two machining processes namely conventional machining (CM) and abrasive water jet machining (AWJM) on the mechanical behavior of composite plates under cyclic loading. For this purpose, an experimental study using several composite plates drilled with a cutting tool and an abrasive water jet machining was carried out. In order to study the impact of the process of machining on the mechanical behavior, thermographic infrared testing and fatigue cyclic tests were performed to assess temperature evolutions, stiffness degradation, and the damage evolution in these plates. Fatigue testing results have shown that the damage accumulation in specimens drilled with CM process was higher than the AWJM specimens. Furthermore, the endurance limit for a composite plate drilled with CM was approximately 10% inferior compared to specimens drilled with AWJM. This difference can be related to the initial surface integrity after machining induced by the difference in the mechanism of material’s removal between the two processes used.     

不同加工材料在线切割加工中对加工质量的影响

就不同材料在线切割加工中对加工质量的影响作了详细地分析和研究,提出了针对加工材料性能来合理选取加工工艺、实施加工方法以及优化加工参数的具体措施,对进一步完善切割工艺,提高加工质量,具有一定的借鉴作用.     

A GENERIC MECHANICS OF CUTTING APPROACH TO PREDICTIVE TECHNOLOGICAL PERFORMANCE MODELING OF THE WIDE SPECTRUM OF MACHINING OPERATIONS

ABSTRACT

The need for quantitatively reliable predictive models for the many technological machining performance measures to optimize the economic performance of machining operations, and to design machine tools and cutting tools that enhance this economic performance, has been highlighted. Also highlighted is the formidable task of establishing the required quantitative technological performance data and equations, and the gap between theory and practice. The development and generic nature of the “unified or generalized mechanics of cutting approach” to technological performance prediction for the wide spectrum of machining operations is presented and discussed in this paper. Suggestions for overcoming some practical difficulties and extending the scope of this predictive modeling approach are also considered.     

新研制塑料模具钢电火花加工机理研究

对一新研制塑料模具钢从切削机理角度，进行电火花加工性能研究，并与同类进口钢进行对比，为新钢种研制提供了支持数据，可直接指导企业生产。