Materials Test 1

What percentage of US GDP is accounted for by the manufacturing industries?

12%

Manufacturing technologically

the application of physical and chemical processes to alter the geometry, properties, and appearance of a given starting material to make parts or products

Manufacturing economically

The transformation of materials into items of greater value by means of one or more processing and or assembly operations. Manufacturing adds value to material by changing or combining it.

Primary industries

one that cultivates and exploits natural resources, such asSecon agriculture or mining

Secondary industries

takes the outputs of primary industries and converts them to consumer and capital goods like textiles and electronicsT

Tertiary industries

the service sector of economy, like banking and education

Consumer good

product purchased directly by consumer like car, TV, phone

Capital goods

purchased by companies in order to product goods or provide services like computers, trucks, construction equipment

Product variety v production quantity

Production quantity is inversely related to product variety. A factory that produces a large variety of products will produce a smaller quantity of each. A company that products a single product will product a large quantity.

Technological processing capability

available set of manufacturing processes. What distinguishes plants is the processes they can perform. Technological processing capability is not only physical processes but also expertise possessed by plant personnel in these processing technologies.

Four categories of engineering materials in manufacturing

metals, ceramics, polymers, composite materials

Steel

iron-carbon alloy. compositions includes other alloying elements as well to enhance property of metal Typ

Typical applications of steel

construction, transportation, and consumer products

Thermoplastic polymer

can by subjected to multiple heating and cooling cycles without substantially altering the molecular structure of the polymer

thermosetting polymer

chemically transform (cure) into a rigid structure on cooling from a heated plastic condition

Process layout

A process layout is one where the machinery in a plant is arranged based on the type of process it performs. To product a product it must visit the departments in the order of the operations being performed.

Product layout

machinery is arranged based on the general flow of the products that will be produced. Works well when all products tend to follow the same sequence of production

Overhead costs

all the expenses of operating the company other than material, labor, and equipment

Factory overhead

costs of running the factory excluding materials, direct labor, and equipment. Includes plant supervision, maintenance, insurance, heat, lightco

corporate overhead

company expenses not related to the factory, such as sales, marketing, accounting, legal, engineering, health benefits

availability

the proportion uptime of the equipment

Polymer bonding

covalent

If stress values were measured during a tensile test what would have higher value

true stress>engineering stress

Behavior of brittle materials such as ceramics and thermosetting plastics

perfectly elastic

Types of elements

metals, nonmetals, semimetals

Noble metals

copper, silver, gold

Primary bonding

strong bonding between atoms in a material, for example to form a molecule

Secondary bonding

not as strong and is associated with attraction between molecules in the material

Ionic bonding

atoms of one element give up their outermost electrons to the atoms of another element to form complete outer shells

Crystalline structures

located at regular and repeating lattice positions in three dimensions, thus the crystal structure possesses a long range order which allows a high packing density

Noncrystalline structure

atoms are positioned randomly in the material not possessing any repeating, regular pattern

Common point defects in a crystal lattice structure

Vacancy-a missing atom in the lattice structure, Ion-pair vacancy-a missing pair of ions of opposite charge in a compound, interstitially-a distortion in the lattice caused by an extra atom present, Frenkel defect-an ion is removed from a regular position in the lattice and inserted into an interstitial position not normally occupied by such an ion

How do grain boundaries contribute to the strain hardening phenomenon in metals?

Grain boundaries block the continued movement of dislocations in the metal during straining. As more dislocations become blocked, the metal becomes more difficult to deform; in effect it becomes stronger

Materials with crystalline structure

metals, ceramics other than glass, some plastics have a partially crystalline structure

Materials with noncrystalline structure

glass, rubber, certain plastics (thermosetting)

Basic difference in the solidification process between crystalline and noncrystalline structures

crystalline structures undergo an abrupt volumetric change as they transform from liquid to solid state and vice versa. This is accompanied by an amount of energy called the heat of fusion that must be added to the material during melting or released during solidification. Noncrystalline materials melt and solidify without the abrupt volumetric change and heat of fusion.

The thermal expansion properties of polymers

greater than those of metals

Solidus

marks the beginning of melting in the heating of most metal alloys

the mass diffusion rate dm/dt across a boundary between two different metals is a function of

concentration gradient dc/dx

Superconductor

zero resistivity

Tolerance

total permissible variation from a specified dimension

Outside micrometer could measure

shaft diameter

In Go/NO-GO gage, a GO gage

checks maximum material condition

What is the dilemma between design and manufacturing in terms of mechanical properties?

To achieve design function and quality, the material must be strong; for ease of manufacturing, the material should not be strong, in general.

What are the three types of static stresses to which materials are subjected?

Tensile, compressive, and shear. Tensile stresses tend to stretch the material, compressive stresses tend to squeeze it, and shear involves stresses that tend to cause adjacent portions of the material to slide against each other.

Hooke’s Law

Hooke's Law defines the stress strain relationship for an elastic material where E = a constant of proportionality called the modulus of elasticity.

What is the difference between engineering stress and true stress in a tensile test?

Engineering stress divides the load (force) on the test specimen by the original area; whereas true stress divides the load by the instantaneous area which decreases as the specimen stretches.

Define tensile strength of a material.

The tensile strength is the maximum load experienced during the tensile test divided by the original area.

Define yield strength of a material.

The yield strength is the stress at which the material begins to plastically deform. It is usually measured as the 0.2% offset value, which is the point where the stress strain curve for the material intersects a line that is parallel to the straight-line portion of the curve but offset from it by 0.2%.

What is work hardening?

Work hardening, also called strain hardening, is the increase in strength that occurs in metals when they are strained.

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?

In a compression test, the specimen cross sectional area increases as the test progresses; while in a tensile test, the cross sectional area decreases.

Tensile testing is not appropriate for hard brittle materials such as ceramics. What is the test commonly used to determine the strength properties of such materials?

A three point bending test is commonly used to test the strength of brittle materials. The test provides a measure called the transverse rupture strength for these materials.

How is shear strength S related to tensile strength TS, on average?

S = 0.7 TS, on average.

What is hardness, and how is it generally tested?

Hardness is defined as the resistance to indentation of a material. It is tested by pressing a hard object (sphere, diamond point) into the test material and measuring the size (depth, area) of the indentation.

Why are different hardness tests and scales required?

Different hardness tests and scales are required because different materials possess widely differing hardnesses. A test whose measuring range is suited to very hard materials is not sensitive for testing very soft materials.

Define the recrystallization temperature for a metal

The recrystallization temperature is the temperature at which a metal recrystallizes (forms new grains) rather than work hardens when deformed.

Define viscosity of a fluid.

Viscosity is the resistance to flow of a fluid material; the thicker the fluid, the greater the viscosity.

What is the defining characteristic of a Newtonian fluid?

A Newtonian fluid is one for which viscosity is a constant property at a given temperature. Most liquids (water, oils) are Newtonian fluids.

What is viscoelasticity, as a material property?

Viscoelasticity refers to the property most commonly exhibited by polymers that defines the strain of the material as a function of stress and temperature over time. It is a combination of viscosity and elasticity

The manufacturing engineering department in an organization is best described as which one of the following:

technical staff function

Which of the following is NOT a usual responsibility of the manufacturing engineering department?

marketing the product

Which of the following is considered a basic process, as opposed to a secondary process?

impression die forging

Which of the following would be considered a secondary process, as opposed to a basic process?

machining a metal casting

In a make or buy situation, the decision should always be to purchase the component if the vendor ’s quoted price is less than the in-house estimated cost of the component:

False

Which of the following is an operation to enhance physical properties?

annealing

A route sheet is a document whose principal function is which one of the following

specifies the process plan

Which one of the following types of computer-aided process planning relies on parts classification and coding in group technology?

retrieval CAPP

The thermal expansion properties of polymers are generally _____ those of metals.

greater than

In the heating of most metal alloys, melting begins at a certain temperature and concludes at a higher temperature. In these cases, which of the following temperatures marks the beginning of melting:

solidus

Copper is generally considered easy to weld because of its high thermal conductivity:

false

Which of the following pure metals is the best conductor of electricity:

silver

A superconductor is characterized by which of the following :

zero resistivity

A tolerance is which one of the following:

total permissible variation from a specified dimension

An outside micrometer would be appropriate for measuring which of the following?

shaft diameter

Mining is classified in which one of the following industry categories:

primary

Inventions of the Industrial Revolution include which one of the following:

steam engine

High volume production of assembled products is most closely associated with which one of the following layout types?

product

A production planning and control department accomplishes which of the following functions in its role of providing manufacturing support?

schedules the order of products on a machine

Polymers are characterized by which of the following bonding types ?

covalent

If stress values were measured during a tensile test, which of the following would have the higher value:

true stress

Which one of the following types of stress strain relationship best describes the behavior of brittle materials such as ceramics and thermosetting plastics:

perfectly elastic

Which one of the following materials has the highest hardness:

alumina ceramic

Precision

Precision in measurement is the degree to which random errors are minimized.

Accuracy

Accuracy is the degree to which the measured value agrees with the true value of the quantity of interest. It is a measurement procedure that is absent of systematic errors.

What is the difference between a bilateral tolerance and a unilateral tolerance?

A bilateral tolerance allows variation in both positive and negative directions from the nominal dimension, whereas a unilateral tolerance allows the variation from the nominal dimension to be either positive or negative, but not both.

tolerance

A tolerance is defined as the total amount by which a specified dimension is permitted to vary.

Electrolyte

An electrolyte is an ionized solution capable of conducting electric current by movement of the ions.

Why are metals better conductors of electricity than ceramics and polymers?

Metals are better conductors because of metallic bonding, which permits electrons to move easily within the metal. Ceramics and polymers have covalent and ionic bonding, in which the electrons are tightly bound to particular molecules.

What is thermal conductivity as a material property?

Thermal conductivity is the capacity of a material to transfer heat energy through itself by thermal movement only (no mass transfer).

Define specific heat as a material property.

specific heat is defined as the quantity of heat required to raise the temperature of a unit mass of the material by one degree.

Describe the melting characteristics of a noncrystalline material such as glass.

In the heating of a noncrystalline material such as glass, the material begins to soften as temperature increases, finally converting to a liquid at a temperature defined for these materials as the melting point.

What is the difference in melting characteristics between a pure metal element and an alloy metal?

A pure metal element melts at one temperature (the melting point), while an alloy begins melting at a certain temperature called the solidus and finally completes the transformation to the molten state at a higher temperature called the liquidus. Between the solidus and liquidus, the metal is a mixture of solid and liquid.

Density

Density is the weight per unit volume of a material.