Chapter 7 Qualities of Machined Surface
The basic knowledge covered and required in this chapter •Basic concepts related to machined surface qualities
•Factors influencing the machined surface qualities
•Methods to improve the machined surface qualities
Some questions related to surface quality
(1) According to your experience, how to judge the surface quality is good or
not? what are the main functions of surface?
(2) Is there any relationship between machining accuracy and surface
quality
(3)How to obtain good surface quality?
7.1Definition of the machined surface quality
7. 2 Influence of the machined surface qualities on part performances 7. 3 Factors affecting the machined surface qualities
7.3Technical approach of controlling the machined surface quality 7.4Vibration and chatter（振颤）in machining operations
7.1 Definition of machined surface quality
•Machined surface quality involves two aspects,
(1) Geometrical shape of the surface layer（几何形状）
(2) Physical and mechanical properties of surface layer, it can be further divided into
the following three forms,
(a) Work-hardening(冷作硬化）: In machining, the metal surface layer of the
workpiece will suffer intensive cold plastic deformation, which will increa its
strength and hardness .
(b)Metallurgical structure change（金相组织变化）:Cutting heat will make the
temperature of workpiece surface increa so that the metallurgical structure of the surface layer changes.
(c)Residual stress（残余应力）:D ue to the influence of cutting deformation and
cutting heat,residual stress will occur on the surface layer of the workpiece.
