Upload
saeed
View
275
Download
0
Embed Size (px)
Citation preview
8/16/2019 CHap 2-Tensile Testing
1/27
Chap : 2
Tensile Test
8/16/2019 CHap 2-Tensile Testing
2/27
Introduction
• Tensile properties are used in selecting
materials for various applications.
• Tensile properties are also used inresearch and development to compare
new materials or processes.• tensile stress–strain curves can be used
to predict a
material’s behavior under forms of loading
8/16/2019 CHap 2-Tensile Testing
3/27
Introduction
• Tensile Test permit todetermine
–Strength
–Ductilit
– Toughness
–!lastic "odulus
–Strain#hardening capabilit
8/16/2019 CHap 2-Tensile Testing
4/27
Introduction
• The level of stress that causesappreciable
plastic deformation of a material iscalled its ield stress
• The ma$imum tensile stress that amaterial carries is called its tensilestrength %or ultimate strength orultimate tensile strength&
• Ductilit is a measure of how much
the material can deform before it
8/16/2019 CHap 2-Tensile Testing
5/27
Tensile Specimens
8/16/2019 CHap 2-Tensile Testing
6/27
"echanical Testing "achine
8/16/2019 CHap 2-Tensile Testing
7/27
Stress–Strain Curve
8/16/2019 CHap 2-Tensile Testing
8/27
Stress–Strain Curve
–'inear elastic: elongation in thespecimen that is proportional tothe applied load.
–!ngineering stress: the ratio of theapplied load () to the originalcross#sectional area) *o) of the
specimen.
• !ngineering stress e+uation: , -(*o
• !n ineerin strain e uation: e -
8/16/2019 CHap 2-Tensile Testing
9/27
Stress–Strain Curve
•
/ield Stress: the stress at which permanent%plastic& deformation occurs.
• (ermanent %plastic& deformation: stressand strain are no longer proportional.
• 0ltimate tensile strength %0TS&: thema$imum engineering stress.
• If the specimen is loaded beond its 0TS it
begins to 1nec.3• 4racture stress: the engineering stress at
fracture.
8/16/2019 CHap 2-Tensile Testing
10/27
Stress–Strain Curve
8/16/2019 CHap 2-Tensile Testing
11/27
Stress–Strain Curve
• "odulus of elasticit: ration of stressto strain in the elastic region. – "odulus of elasticit e+uation: ! - ,e
• This linear relationship is nown as5ooe’s 'aw.
• (oisson’s 6atio: the ratio of thelateral strain to the longitudinalstrain.
8/16/2019 CHap 2-Tensile Testing
12/27
True#Stress and True#Strain
• True#stress: ratio of the load) () tothe instantaneous cross#sectionalarea) *) of the specimen.
• True#strain: the sum of all theinstantaneous engineering strains. – True#stress e+uation: , - (*
– True#strain e+uation: e - ln%llo&
8/16/2019 CHap 2-Tensile Testing
13/27
Ductilit
• Ductilit: e$tent of plasticdeformation that the material
undergoes before fracture.• Two measures of ductilit:
– Total elongation: %lf #lo&lo $ 7889
–6eduction of *rea: %*o#*f &*o $7889
8/16/2019 CHap 2-Tensile Testing
14/27
Temperature !ects
*s temperatureincreases:
Ductilit andtoughnessincrease.
/ield stressand themodulus of
elasticit
8/16/2019 CHap 2-Tensile Testing
15/27
!ect of Strain 6ate on0ltimate Tensile Strength
*s the temperature
increases) theslopes of the curvesincrease; thus)strength becomes
more and moresensitive to strainrate astemperatureincreases
8/16/2019 CHap 2-Tensile Testing
16/27
Sample problem 7
8/16/2019 CHap 2-Tensile Testing
17/27
8/16/2019 CHap 2-Tensile Testing
18/27
Sample problem 2
• 4orce and length change data are given intable below for the tension test of *ISI
8/16/2019 CHap 2-Tensile Testing
19/27
solution
8/16/2019 CHap 2-Tensile Testing
20/27
Sample problem A
8/16/2019 CHap 2-Tensile Testing
21/27
8/16/2019 CHap 2-Tensile Testing
22/27
Sample problem B
!ngineering stress–strain data from a tension teston *ISI B7B8 steel tempered at 28BC %B884&are listed in Table below. The diameter beforetesting was ?.>7 mm) and after fracture theminimum diameter in the neced region was ?mm.
Determine the following:
!lastic modulus) 8.29 oset ield strength)ultimate tensile strength) percent elongation)and percent
reduction in area.
8/16/2019 CHap 2-Tensile Testing
23/27
Sample problem B
8/16/2019 CHap 2-Tensile Testing
24/27
Sample problem =
Stress–strain data are plotted in 4ig. below for the initialportion of a tension test on *ISI B7B8 steel temperedat =AC %78884&. Eote that data points * and F arelabeled with their stress–strain coordinates.
)a(Determine the elastic modulus E.)b(If a bar of this material 100mm long is
strained to point A and then unloaded, what isits length at point A and also after unloading
)c(If a sample of this material is strained to point B andthen unloaded, what is the plastic (permanent) strain thatremains after unloading?
8/16/2019 CHap 2-Tensile Testing
25/27
Sample (roblem =
8/16/2019 CHap 2-Tensile Testing
26/27
Sample (roblem >• 4orce and length change data are given in Table
below for the initial portion of a tension test on*ISI B7B8 steel tempered at =AC %78884&.
The diameter before testing was ?.77 mm) andthe gage length 'i for the length change
measurement was =8 mm.(a) Calculate corresponding values of
engineering stress and display thesevalues on a stressstrain plot!
(b) Calculate corresponding values of Truestress and strain!
)c(Determine the yield strength for a plastic strainoset of 0.002, that is, 0.2%, and percent
elongation percent reduction in area.
8/16/2019 CHap 2-Tensile Testing
27/27
Sample (roblem >