Engine
Tensile Strength of a Material
(Maximum Load experienced during test) / (original area)
Work Hardening
(Strain Hardening) The increase in strength in metals that occurs when they are strained
Accuracy in Measurement
Accuracy is the degree to which the measured value agrees with the true value of the quantity of interest
Complicating factor that occurs in compression test
Barreling of test specimen due to friction caused at the interfaces with the testing machine plates.
shear elasticity G to tensile E
G = 0.4 E on average
State Hooks Law
Hooke's law defines the stress-strain relationship for an elastic material. spiral thing = Ee where E is a constant of proportionality called the modulus of elasticity.
shear S to TS tensile
S = 0.7 TS
Engineering Stress
The engineering stress and strain in a tensile test are defined relative to the original area and length of the test specimen original value onto applied load F/Original
Yield Strength of a Material
The stress at which a material begins to plastically deform. usually measured at 0.2% offset value stress strain curve relationship (right at curve)
True Stress
The true stress and strain in a tensile test defined relative to the instantaneous area and length of the test specimen as it decreases through the duration of the test instantaneous value onto applied load F/Actual
Capital Good
Those purchased by firms to produce goods and services construction equipment
Unilateral Tolerance
Tolerance variation is only permitted in one direction: increasing or decreasing but not both
Bi-Lateral Tolerance
Tolerance variation is permitted in both direction (increasing, decreasing)
A tolerance
Total amount by which a specified dimension is permitted to vary tolerance is total max minus min
Newtonian Fluid
Viscosity is same at given temp water, oil
problems with hardness measurment
different hardness of surfaces very hard cant be used for very soft
Why are surfaces important
aesthetics safety friction and wear/tear effect on mechanic (sliding part) and physical (uneven) properties electrical contacts
manufacturing process with best surface finish
b. grinding
Why cannot a direct conversion be made between the ductility measures of elongation and reduction in area using the assumption of constant volume?
because of necking that occurs in the test specimen.
How does the change in cross-sectional area of a test specimen in a compression test differ from its counterpart in a tensile test specimen?
compression test - cross sectional area increases as test progresses tensile test - cross sectional area decreases as test progresses
Changes / Injuries that occur at or just below the surface of a metal
cracks craters variations in hardness at the surface intergranular attack metallurgical changes resulting from heat
Thermal Energy changes in altered layer
hardness variation, heat affected zone, recrystalization
product variety v product quantity
large variety = small quantity large quantity = small variety
batch production
make group, lots, or batches of a production part before moving onto next assembly step small or medium production might need to change machine set up for next step
manufacturing support departments
manufacturing engineering production planning and control quality control
basic categories of materials
metals ceramics polymers
2 subclasses of assembly processes
permanent joining - welding, adhesive mechanical fastening - nuts, bolts, rivets
primary, secondary, and tertiary industries
primary - exploits natural resources (agriculture, mining) secondary - takes outputs of primary industries and turns them into consumer and capital goods (electronics, textiles) tertiary - service sector (banking , education)
process layout v product layout
process layout it where different production functions are split. more unique and smaller amount of products with increased travel time product layout - reduced travel time, arranged by general production of product makes stuff go faster
viscosity
resistance to flow of a fluid material thicker more viscosity
Hardness
resistance to indentation pressing hard object into surface and measuring indentation
shaping process v surface process
shaping - changes the geometry of the material surface - only alters surface
Surface Roughness
small fine made deviations from the nominal surface (perfect) made by process that created the surface average vertical deviations from nominal surface
nominal surface
surfaces that are geometrically perfect to the specification of an engineering design drawing. perfectly everything (round, straight, etc.)
manufacturing capability
tech process capabilities physical size and weight production capactity technical and physical limitations of firm
recrystallization temperature
temperature at which metal forms new grains (recrystallization) rather than work hardens
What are the three types of static stresses to which materials are subjected?
tensile, compressive, shear
measure for strength of ceramics
three-point bending test. provides the transverse rupture strength
strength coefficient = yield coeffecient
when a material is perfectly plastic and does not strain harden