Transcript surfaceengineering
Chapter 35: Surface Engineering
DeGarmo’s Materials and Processes in Manufacturing
35.1 Introduction
Fatigue Strength as a Function of Finish
FIGURE 35-1
Fatigue strength of Inconel 718 components after surface finishing by grinding or EDM.
(Field and Kahles, 1971).
Surface Profiles
FIGURE 35-2
Machining processes produce surface flaws, waviness, and roughness that can influence the performance of the component.
Machined Surfaces
Machined Surfaces
FIGURE 35-3
(a) Terminology used in specifying and measuring surface quality; (b) symbols used on drawing by part designers, with definitions of symbols; (c) lay symbols; (d) lay symbols applied on drawings.
Surface Measurement
FIGURE 35-4
(a) Schematic of stylus profile device for measuring surface roughness and surface profile with two readout devices shown: a meter for AA or rms values and a strip chart recorder for surface profile. (b) Profile enlarged. (c) Examples of surface profiles.
Surface Finish Measurement
FIGURE 35-5
Typical machined steel surface as created by face milling and examined in the SEM. A micrograph (same magnification) of a 0.00005-in. stylus tip has been superimposed at the top.
SEM Micrograph
FIGURE 35-6
(a) SEM micrograph of a U.S. dime, showing the
S
in the word
TRUST
after the region has been traced by a stylus-type machine.
(b) Topographical map of the
S
region of the word
TRUST
from a U.S. dime [compare to part (a)].
Roughness
FIGURE 35-7
Comparison of surface roughness produced by common production processes.
(Courtesy of
American Machinist
.)
35.2 Mechanical Cleaning and Finishing Blast Cleaning
Finishing Barrel
FIGURE 35-8
Schematic of the blow of material in tumbling or barrel finishing. The parts and media mass typically account for 50 to 60% of capacity.
Synthetic Media Geometry
FIGURE 35-9
Synthetic abrasive media are available in a wide variety of sizes and shapes.
Through proper selection, the media can be tailored to the product being cleaned
Vibration Finishing Tub
FIGURE 35-10
Schematic diagram of a vibratory-finishing tub loaded with parts and media. The single eccentric shaft drive provides maximum motion at the bottom, which decreases as one moves upward. The dualshaft design produces more uniform motion of the tub and reduces processing time
Media to Part Ratio
Part Examples
FIGURE 35-11
A variety of parts before and after barrel finishing with triangular-shaped media.
(Courtesy of Norton Company.)
35.3 Chemical Cleaning
35.4 Coatings
Organic Finishes
Electroplating Processes
FIGURE 35-12
Basic steps in the electrocoating process
Powder Coating
Powder Coating Systems
FIGURE 35-13
A schematic of a powder coating system. The wheels on the color modules permit it to be exchanged with a spare module to obtain the next color.
Electroplating Circuitry
FIGURE 35-14
Basic circuit for an electroplating operation, showing the anode, cathode (workpiece), and electrolyte (conductive solution).
Electroplating Design Recomendations
FIGURE 35-15
Design recommendations for electroplating operations
Anodizing
FIGURE 35-16
The anodizing process has many steps.
Nickel Carbide Plating
FIGURE 35-17
(Left) Photomicrograph of nickel carbide plating produced by electroless deposition. Notice the uniform thickness coating on the irregularly shaped product. (Right) High-magnification cross section through the coating.
(Courtesy of Electro-Coatings Inc.)
35.5 Vaporized Metal Coatings
35.6 Clad Materials
35.7 Textured Surfaces
35.8 Coil-Coated Sheets
35.9 Edge Finishing and Burrs
Burr Formation
FIGURE 35-18
Schematic showing the formation of heavy burrs on the exit side of a milled slot.
(From L. X. Gillespie,
American Machinist,
November 1985.)
Deburring Allowance
35.10 Surface Integrity
Burr Prevention
FIGURE 35-19
Designing extra recesses and grooves into a part may eliminate the need to deburr.
(From L.X. Gillespie,
American Machinist,
November 1985.)
Surface Deformation
FIGURE 35-20
Plastic deformation in the surface layer after cutting.
(B. W. Kruszynski
and
C. W. Cuttervelt,
Advanced Manufacturing Engineering,
Vol
.
1, 1989.)
Shot Peening
FIGURE 35-21
(a) Mechanism for formation of residual compressive stresses in surface by cold plastic deformation (shot peening). (b) Hardness increased in surface due to shot peening.
Surface Damage as a Function of Rake Angle
FIGURE 35-22
The depth of damage to the surface of a machined part increases with decreasing rake angle of the cutting tool.
Surface Stress FIGURE 35-23 (Top) A cantilever-loaded (bent) rotating beam, showing the normal distribution of surface stresses (i.e., tension at the top and compression at the bottom).
(Center)
The residual stresses induced by roller burnishing or shot peening.
(Bottom)
Net stress pattern obtained when loading a surface-treated beam.
The reduced magnitude of the tensile stresses contributes to increased fatigue life.
Fatigue Life with Surface Finish
FIGURE 35-24
Fatigue life of rotating beam 2024-T4 aluminum specimens with a variety of surface-finishing operations. Note the enhanced performance that can be achieved by shot peening and roller burnishing.