University Materials Science and Engineering Online Test Two

This document provides the solutions to an online materials science test, covering a wide range of topics in materials science and engineering. The test includes questions on photovoltaic semiconductors, ceramic manufacturing processes, and the properties of various materials such as steel, ceramics, polymers, and composites. Specific concepts addressed include fracture toughness, creep, sintering, porosity, and the effects of different material compositions and structures on their mechanical and electrical properties. The questions explore the applications of these materials in various engineering contexts, including aerospace, hip joint replacements, and cutting tools. The solutions provide detailed answers to multiple-choice questions, offering insights into the correct and incorrect statements related to each concept. This resource can be used by students to prepare for exams, understand key concepts, and improve their knowledge of materials science.

Online Test Two
Q:
Photovoltaic Semi conducting ceramics such as Indium Galium Selinide
A:
Produce energy as part of a p-n junction CORRECT
Q:
How would the strength of a ceramic component be enhanced during manufacture?
A:
Hot isostatic pressing CORRECT
Q:
Solidified steel crystal structure is
A:
body centred cubic or face centred cubic. CORRECT
Q:
Which is the incorrect statement from the following list
A:
Ceramics have poor high temperature properties. CORRECT
Q:
Which is the correct statement from the following list:
Engineers favour the use of composites in aerospace applications because
A:
They have excellent strength to density properties CORRECT
Q:
creep can be defined as;
A:
Increasing strain on a part with constant stress at high Temperatures. CORRECT
Q:
A ceramic material has a fracture toughness value of 4.5MPa m -1/2 and is under a tensile stress of
1000MPa, where Y=1 what is the critical crack dimension before brittle fracture.
A:
20um CORRECT
Q:
Select the correct answer form the following statements; Increasing the initial stress during a creep
test
A:
Lowers the temperature during the testing process WRONG
Q:
Which is the correct statement from the following list
To produce a ceramic the ceramic powder is
A:
mixed with binder and dispersant CORRECT
Q:
From the following list identify the incorrect statement
Ceramic acetabular components used in replacement hip joints must have the following properties

A:
High friction coefficient CORRECT
Q:
The tensile strength of ceramics is approximately related to the porosity by the expression UTS=UTS0e-
nP where P is the volume fraction of pores in the solid, UTS 0 is the tensile strength at zero porosity and
the exponent n=4, UTS0=150Mpa and the porosity is 20%
What is the calculated value of the UTS.
A:
673MPa CORRECT
Q:
From the following statements, select the correct answer;
Side groups on polymer mer units
A:
decreases polymer chain flexibility CORRECT
Q:
Polyethylene thermoplastic polymers is;
A:
always very flexible WRONG
Q:
From the following statements, select the correct answer;
Thermoplastic polymers;
A:
soften when heated CORRECT
Q:
Elastomeric polymers are…
A:
melt when heated WRONG
Q:
Which is the correct statement from the following list
In producing a fully dense ceramic, the sintering process is driven by;
a:
diffusion within powder particles CORRECT
Q:
Select the correct answer from the list
Polymeric materials are;
A:
can be both amorphous and crystalline CORRECT
Q:
Which is the incorrect statement from the following list
A laminar composite is
A:
composed of alternating layers of fibre materials WRONG
Q:
Cermet composites have a better shock resistance when they are used as cutting tools when
A:
the % of matrix decreases WRONG

Q:
Which is the correct statement from the following list
Under tensile loading the bond strength of fibres in a matrix must
A:
be greater than the tensile strength of fibre CORRECT
Q:
Which is the correct statement from the following list
Engineers favour the use of composites in aerospace applications because
A:
They have excellent strength to density properties CORRECT
Q:
Choose the correct answer from the following list.
Dispersion strengthened composites
A:
Have enhanced creep properties CORRECT
Q:
Building Integrated Flexible Photo Voltaic cells are
A:
10-15% efficient at conversion of solar energy into electrical energy CORRECT
Q:
Which factor DOES NOT reduce the fatigue life of a component
A:
carburising the surface CORRECT
Q:
Which statement in the following list is incorrect
The main service requirements of the matrix material in a composite are
A:
should not be strongly bonded to the matrix to allow cracks to propagate CORRECT
Q:
Colours in polymers fillers in polymers are produced by
A:
the addition of pigments and dyes CORRECT
Q:
Tape casting of Al2O3 tiles is used for producing;
A:
IC chips CORRECT
Q:
The largest use of polymers in industry
A:
consumer products WRONG
Q:
Addition reaction used in the polymerisation process
A:
need initiation catalysts CORRECT
Q: A steel component has a hardness of 225HB (Brinell hardness) calculate its approximate ultimate
tensile strength
A:
775MPa CORRECT
EXAM OVER

Q:
The modulus of elasticity of a ceramic is approximately related to the porosity by the expression
E=E0 (1 - 1.9P + 0.9P2) where E0 is the modulus at zero porosity. If a fully dense ceramic has the
properties of and E0=300Gpa what is the resulting modulus at 40% porosity.
A:
115Gpa CORRECT
Q:
A brittle fracture of a test specimen in an impact test is usually characterised by;
A:
A bright sparkling surface CORRECT
Q:
Select the correct answer from the list
Polymeric materials are;
A: Can be both amorphous and crystalline CORRECT
Q:
Which statement in the following list is incorrect
The main service requirements of the matrix material in a composite are
A:
should not be strongly bonded to the matrix to allow cracks to propagate. CORRECT
Q:
Select the correct answer from the list
Polymer crystallinity
A:
does not change the polymer density WRONG
Q:
Which of the following statements is NOT correct
Glass transition temperature is increased by;
A:
Polymer chain cross links CORRECT
Q:
Which is the correct statement from the following list
In producing a fully dense ceramic, the sintering process is driven by;
A:
diffusion within powder particles WRONG

Q:
Which is the incorrect statement from the following list
Sintering can be aided by;
A:
larger powder particles CORRECT
Q:
Tape casting of Al2O3 tiles is used for producing;
A:
IC chips CORRECT
Q:
From the following statements, select the correct answer;
Side groups on polymer mer units
A:
decrease polymer chain flexibility CORRECT
Q:
Elastomeric polymers are;-
A:
are highly flexile thermoplastic polymers WRONG
Q:
Choose the correct answer from the following list.
Dispersion strengthened composites
A:
have enhanced creep properties CORRECT
Q:
Which is the correct statement from the following list
To produce a ceramic the ceramic powder is
A:
mixed with binder and dispersant CORRECT
Q:
Which is the correct statement from the following list
Under tensile loading the bond strength of fibres in a matrix must
A:
be greater than the tensile strength of the fibre CORRECT
Q:
A ceramic material has a fracture toughness value of 4.5MPa m -1/2 and is under a tensile stress of
1000MPa, where Y=1 what is the critical crack dimension before brittle fracture.
A:
20um CORRECT
Q:
From the following statements, select the correct answer;

Thermoplastic polymers;
A:
soften when heated CORRECT
Q:
From the following list identify the incorrect statement
Ceramic acetabular components used in replacement hip joints must have the following properties
A:
high friction coefficient CORRECT
Q:
A thermoplastic material filled with 20% glass fibre would
A:
increase the materials ductility WRONG
Q:
Which of the following statements concerning thermoplastics is incorrect
A:
increasing the temperature increases the ductility CORRECT
Q:
Which statement from the following list is incorrect
A:
Ceramics have excellent thermal conduction properties CORRECT
Q:
Which of the following statements is incorrect
A:
Thermosetting polymers are used in recycling CORRECT
Q:
When measuring fatigue strength of a material the results are represented on a graph where
A:
Stress is plotted against number of stress cycles CORRECT
Q:
The tensile strength of ceramics is approximately related to the porosity by the expression UTS=UTS0e-
nP where P is the volume fraction of pores in the solid, UTS 0 is the tensile strength at zero porosity and
the exponent n=4, UTS0=150Mpa and the porosity is 20%
What is the calculated value of the UTS.
A:
673Mpa CORRECT
Q:
Interstitial solid solution hardening is
A:
not normally employed for hardening metals WRONG

Q:
Select the correct answer form the following statements; Increasing the initial stress during a creep
test
A:
increases the rate of creep WRONG
Q:
Which is the incorrect statement from the following list
A:
ceramics have poor high temperature properties CORRECT
Q:
Which is the incorrect statement from the following list
A laminar composite is
A:
composed of particle reinforced elements CORRECT
Q:
For a specimen under a tensile stress of 100N/m 2 and having a “notch” type flaw whose length is
3mm with a tip radius of 50μm, calculate the stress at the tip of the notch.
A:
1649 Nm2 CORRECT
Q:
From the following list identify the incorrect statement
Ceramic acetabular components used in replacement hip joints must have the following properties
A:
high friction coefficient CORRECT
Q:
The largest use of polymers in industry
A:
packaging CORRECT
EXAM OVER:

Q:
The largest use of polymers in industry
A:
Packaging CORRECT
Q:
From the following statements, select the correct answer;
Thermoplastic polymers;
A:
soften when heated CORRECT
Q:
From the following list identify the incorrect statement
Ceramic acetabular components used in replacement hip joints must have the following properties
A:
HFC CORRECT
Q:
Which is the correct statement from the following list
Engineers favour the use of composites in aerospace applications because
A:
excellent strength to density properties CORRECT
Q:
Elastomeric polymers are;-
A:
thermoplastic polymers with no cross links between chains WRONG
Q:
Select the correct answer from the list:
Vulcanisation is;
A:
making synthetic rubber for road tyres WRONG
Q:
Addition reaction used in the polymerisation process
A:
need initiation catalysts CORRECT
Q:
Which is the incorrect statement from the following list
In terms of electrical properties ceramics can

A:
Can be semi conductors WRONG
Q:
When measuring fatigue strength of a material the results are represented on a
graph where;
A:
stress is plotted against number of stress cycles CORRECT
Q:
Polyethylene thermoplastic polymers is;
A:
sometimes a mixture of amorphous and crystalline zones CORRECT
Q:
A ceramic material has a fracture toughness value of 4.5MPa m -1/2 and is under a tensile stress of
1000MPa, where Y=1 what is the critical crack dimension before brittle fracture.
A:
20um CORRECT
Q:
Creep can be defined as;
A:
increasing stress on a part with constant stress at high temps CORRECT
Q:
A steel component has a hardness of 225HB (Brinell hardness) calculate its approximate ultimate
tensile strength
A:
775 CORRECT
Q:
Which is the correct statement from the following list
To produce a ceramic the is
A:
mixed with binder and dispersant CORRECT
Q:
Select the correct answer form the following statements; Increasing the initial stress during a creep
test
A:
means less cycles are needed for failure WRONG
Q:
From the following statements, select the correct answer;
Side groups on polymer mer units

A:
decreases polymer chain flexibility CORRECT
Q:
Which factor DOES NOT reduce the fatigue life of a component
A:
carburising the surface CORRECT
Q:
A brittle fracture of a test specimen in an impact test is usually characterised by;
A:
bright sparkling surface CORRECT
Q:
Which is the incorrect statement from the following list
A laminar composite is
A:
composed of particle reinforced elements CORRECT
Q:
Cermet composites have a better shock resistance when they are used as cutting tools when
A:
a different particle filler is used WRONG
Q:
For a specimen under a tensile stress of 100N/m 2 and having a “notch” type flaw whose length is
3mm with a tip radius of 50μm, calculate the stress at the tip of the notch.
A:
1649 CORRECT
Q:
Which of the following statements is NOT correct
The polystyrene mer unit contains
A:
the phenyl side group WRONG
Q:
Photovoltaic Semi conducting ceramics such as Indium Galium Selinide
A:
produce energy as part of a p-n junction CORRECT
Q:
Which is the correct statement from the following list
Kevlar develops impact resistance because;
A:
the chain cross links break allowing controlled chain slippage CORRECT
Q:
The tensile strength of ceramics is approximately related to the porosity by the expression UTS=UTS0e-

nP where P is the volume fraction of pores in the solid, UTS 0 is the tensile strength at zero porosity and
the exponent n=4, UTS0=150Mpa and the porosity is 20%
What is the calculated value of the UTS.
A:
673 CORRECT
Q:
Which is the correct statement from the following list
The sintering process proceeds by;
A:
melting and grain formation WRONG
Q:
Select the correct answer from the list
Polymer crystallinity
A:
does not occur with slow cooling of polymer melts WRONG
Q:
For steel, the energy to produce tensile failure is 10 5Jm-2 (i.e. fracture energy), modulus of
elasticity 200 x 109Nm-2. Thus if steel is to have cracks which do not propagate when a stress of 50
x109Nm-2 is applied then what is the maximum crack length allowable
A:
50um CORRECT
Q:
Which of the following statements is incorrect
A:
Thermosetting polymers are used in recycling CORRECT
Q:
Which is the correct statement from the following list
Under tensile loading the bond strength of fibres in a matrix must
A:
be greater than the tensile strength of fibre CORRECT
NEXT EXAM

Q:
From the following statements, select the correct answer;
Thermoplastic polymers;
A:
soften when heated CORRECT
Q:
Which is the incorrect statement from the following list
In terms of electrical properties ceramics can
A:
never conduct electricity CORRECT
Q:
Creep can be defined as;
A:
increasing strain on a part with constant stress at high temperature CORRECT
Q:
Polyethylene thermoplastic polymers is;
A:
sometimes a mixture of amorphous and crystalline zones CORRECT
Q:
Which factor DOES NOT reduce the fatigue life of a component
A:
carburising the surface CORRECT
Q:
A thermoplastic material filled with 20% glass fibre would
A:
Increase the material UTS CORRECT
Q:
Which statement in the following list is incorrect
The main service requirements of the matrix material in a composite are
A:
should not be strongly bonded to the matrix to allow cracks to propagate CORRECT
Q:
Cermet composites have a better shock resistance when they are used as cutting tools when
A:
the % of the matrix increases CORRECT
Q:
Which is the correct statement from the following list
The sintering process proceeds by;
A:
diffusion processes at grain boundaries CORRECT