tailieunhanh - Rough Surfaces Part 2

Tham khảo tài liệu 'rough surfaces part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Relocation 10-20 firn and as the stylus is only 8 fim wide this is sufficient to invalidate the result. The problem was overcome by Williamson and Hunt 1968 who designed what they called a relocation table. The table is bolted to the bed of the stylus instrument and the specimen stage is kinematically located against it at three points and held in position pneumatically. The stage can be lowered and removed an experiment of some kind performed on the specimen and the stage replaced on the table. Relocation of the stylus then occurs to within the width of the original profile Fig. . It is necessary to raise the stylus during the return stroke of the pickup and of course the specimen may not be removed from the stage during the course of the experiment. The original device has been widely copied Grieve et al. 1970 Thomas et al. 1971 Thomas 1972 . Figure shows a succession of relocated profiles of a surface which was initially rough turned Thomas 1972 . After each measurement the stage was transferred to the table of a surface grinder and a slightly deeper cut taken. The progressive disappearance of the peaks and the persistence of the valleys can be followed in great detail. The same relocation table has also been used successfully to study the effect of successive coats of paint on surface topography King Thomas 1978 . Fig. a Relocation table showing stage raised and held in position by pneumatic clamps during measurement. 31 Stylus instruments b Relocation table ready for removal. Fig. lowered Replication Replication will be considered here although it is not strictly speaking itself a technique of measurement but rather a preliminary to other techniques principally optical and stylus methods. Replication is used with some optical methods to provide a transparent specimen see sect. 32 Replication Fig. V_Jocated profiles of an initially rough turned surface. . . It is also used in electron microscopy to provide a conducting specimen