tailieunhanh - Machinability and Surface Integrity Part 1

Tham khảo tài liệu 'machinability and surface integrity part 1', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Machinability and Surface Integrity It is common sense to take a method and try it. If it fails admit it frankly and try another. But above all try something. FRANKLIN DELANO ROOSEVELT 1882 - 1945 32nd President United States of America 270 Chapter 7 Machinability Introduction - an Historical Perspective Today greater emphasis is being placed on a component s machinability but this term is an ambiguous one having a variety of different meanings depending upon the production engineer s requirements. In fact the machinability expression does not have an authoritative definition despite the fact that it has been used for decades. In 1938 Ernst in his book on the Physics of Metal Cutting defined machinability in the following manner As a complex physical property of a metal involving True machinability a function of the tensile strength Finishability or ease of obtaining a good finish Abrasiveness or the abrasion undergone by the tool during cutting. By 1950 Boulger had summarised these criteria more succinctly in his statement From any standpoint the material with the best machinability is the one permitting the fastest removal of chips with satisfactory tool life and surface finish. This Boulger definition leaves some unanswered questions concerning chip-forming factors cutting forces and has little regard for either the physical and mechanical properties of the material nor potential sub-surface damage caused by the cutting edge. By 1989 Smith made the point that in fact machinability had to address these properties and the word metal should be substituted by the expression material in a combined general-purpose definition as follows The totality of all the properties of a work material which affect the cutting process and the relative ease of producing satisfactory products by chip-forming methods Even these definitions still lack sufficient precision to be of much practical use and by 1999 Gorzkowski et al. in their powder metallurgy paper concerning secondary