Fundamentals of metal forming Flashcards
Name four different ways of classifying a metal forming process
state of stress
type of raw material
forming temperature
method of inducing forcess
name 5 states of stress used in classifying metal forming process
pressure forming tension-compression forming tension forming bend forming shear forming
What two types of raw material are used in classifying a metal forming prcoess
Bulk (3d piece) and sheet (2d piece)
describe the different temperatures used in classifying a metal forming prcoess
Ta<0.75Tm
what two types of force inductions would you use to classify a metal forming process
direct or indirect
Name and briefly describe four types of bulk deformation processes
Rolling: compressive deformation, where thickness of plate reduced through rollers
Forging: work piece is compressed between two imposing dies
Extrusion: workpiece is forced to flow through a die opening
Drawing: the diameter of a bar or wire is reduced by pulling through a die opening
What are desirable properties in a work piece that is to undergo a metal forming process?
high ductility and low yield stress
How does temperature effect important metal forming properties
increased temp increases ductility and decreases yield strength and strain hardening
What is the flow stress of a material?
the instantaneous value of stress required to continue deforming a material
How do you find the average flow stress?
by integrating the flow curve between zero and the final strain value of interest
What are the main advantages (5) and disadvantages of cold working(5)`
better accuracy, better surface finish, strain hardening gives desirable directional properites, no heating required
Dis: higher force and power required, surfaces of starting workpiece must be free of scale and dirt, ductility and strain hardening limits amount of forming that can be done,
additional annealing may be required, some material not capable
Name some advantages (3) and disadvantages (1) of warm working
lower force and power required
more intricate and complex work geometries are possible
need for annealing reduced
dis: investment in furnaces needed
Name adv (6) and disadv (4) of hot working
Adv-work part shape can be significantly altered
-strength properties are generally isentropic
-lower force and power required
-can form materials with low ductility
-no work hardening (no post aneealing)
-no strengthening of part from work hardening (for if part requires subsequent cold working)
DIS:low dimensional accuracy
-high production costs
-poor surface finish
-shorter tool life
What additional material property becomes an issue at high temperatures?
strain rate sensitivity, nelgigable at room temp
How does the strength constant C and strain rate coeff m change with increasing temp
C down, m up
