Manufacturing Processes and Material Properties Overview

Manufacturing

Organized activity converting raw materials into salable goods; critical to a country's economic welfare and standard of living.

Producer goods

Manufactured for other companies to use in making producer or consumer goods.

Consumer goods

Purchased directly by end users or the general public.

Materials history

Progressed through Stone, Copper/Bronze, Iron, Steel Ages to today's plastics, composites, and exotic alloys.

Manufacturing system

Arrangement of processes and physical elements (machines, tooling, labor, materials) converting inputs into finished or semifinished goods.

Production System

The enterprise-wide network—including manufacturing systems plus design, information, quality control, sales, and distribution functions—that delivers goods and services.

Job

The total sequence of operations a worker performs to make a component.

Station

Location or area where a production worker performs tasks.

Operation

A distinct action (e.g., milling, drilling, heat treating).

Treatment

Continuous process modifying a workpiece without tool contact (e.g., plating, curing).

Hand tools

Saw, hammer, screwdriver.

Cutting tools

Drill bits, reamers, milling cutters.

Noncutting tools

Extrusion dies, molds.

Workholders

Jigs, fixtures, collets for precise tool and part positioning.

Fabricating

Assembling parts/components into a finished product.

Processing

Transforming material continuously (e.g., rolling, casting, molding).

Plane or flat

Surfaces defining shape may be: Plane or flat.

Cylindrical

Surfaces defining shape may be: Cylindrical (external/internal).

Conical

Surfaces defining shape may be: Conical (external/internal).

Irregular

Surfaces defining shape may be: Irregular (external/internal).

Design engineers

Specify function, loads, appearance, and manufacturing methods during design.

Manufacturing engineers

Select and coordinate processes, equipment, and materials to realize the design.

Industrial engineers

Layout factories, optimize workflows, integrate machines and processes.

Lean engineers

Design U‑shaped cells and kanban links for one‑piece flow.

Materials engineers

Specify and develop ideal materials for performance and manufacturability.

Globalization

Parts and assemblies may originate anywhere worldwide; advanced tech (CNC, automation) often sourced externally.

Lean/Toyota Production System

100 % good units, integrated quality control, continuous improvement, on‑time delivery at lowest cost.

Job Shop

Functional layout, low volume, high flexibility; parts routed in batches.

Flow Shop

Product‑oriented line, higher volume, special‑purpose machines, conveyor movement.

Linked‑Cell (L‑CMS)

U‑shaped cells feeding final assembly via kanban for one‑piece flow.

Project Shop

Fixed‑position layout for large, immobile products (e.g., ships, buildings).

Continuous Process

Highly automated, non‑stop production of liquids, gases, powders (e.g., refineries).

Structure-Property-Processing-Performance Relationship

Material properties and performance are direct results of a material's structure and its processing; altering properties requires changing structure.

Levels of structure

Atom → molecule/crystal/amorphous → grain (microstructure); imperfections at any level affect mechanical behavior.

Atom

Composed of a nucleus (protons + neutrons) surrounded by electrons; valence electrons in the outer shell govern chemical bonding and many physical properties.

Electron configuration

Distribution in K, L, M, N shells and subshells (s, p, d, f) determines bonding behavior (e.g., Fe: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s²).

Ionic bond

Electron transfer creates cations/anions held by electrostatic attraction; yields materials with high hardness, brittleness, high melting point, and low conductivity.

Covalent bond

Electron sharing between atoms forms strong directional bonds; produces high melting point, high strength, and typically brittle materials whose conductivity depends on bond character.

Metallic bond

Delocalized valence electrons move freely among positive ion cores, imparting ductility, luster, and high electrical/thermal conductivity; bond strength, melting point, and mechanical strength vary with metal and alloy.

Van der Waals forces

Weak intermolecular attractions arising from temporary dipoles; significant in polymers (e.g., polyethylene, PVC).

Molecular structures

Distinct molecules bound by primary bonds; limited in size (e.g., O₂, H₂O).

Crystalline structures

Periodic lattice of atoms described by a unit cell; characteristic of metals and minerals.

Amorphous structures

Lack long‑range periodicity (e.g., glass).

Unit cell

Smallest repeating building block of a crystal.

Simple cubic (SC)

52 % packing efficiency.

Body-centered cubic (BCC)

68 % packing efficiency.

Face-centered cubic (FCC) & Hexagonal close-packed (HCP)

74 % packing efficiency with close‑packed planes maximizing density.

Nucleation & growth

Solidification begins at nuclei that grow into grains, meeting at grain boundaries.

Grain size control

Faster nucleation → smaller grains; faster growth → larger grains.

Elastic deformation

Reversible lattice distortion under low load; atoms return to original positions upon unloading (Poisson's ratio < 0.5).

Plastic deformation

Permanent slip of atomic planes along slip systems when critical shear stress is exceeded; occurs via dislocation motion on close‑packed planes.

Dislocations

Line defects—edge dislocation (extra half‑plane) and screw dislocation (helical plane)—that enable plasticity.

Point defects

Vacancies, interstitials, substitutionals that impede dislocation motion, thereby strengthening the material.

Strain hardening

Increase in strength and hardness due to dislocation interactions during plastic deformation; ductility decreases as work progresses.

Single crystal

Slip initiates on favorably oriented slip systems, forming surface steps and rotating the crystal lattice.

Polycrystalline metals

Grain boundaries block dislocation motion; Hall-Petch effect—finer grains → higher yield strength.

Anisotropy

Directional dependence of properties arising from elongated grains after deformation; isotropy demands equiaxed grain structures.

Ductile fracture

Significant plastic deformation precedes failure.

Brittle fracture

Failure occurs with minimal or no plastic deformation.

Cold working

Plastic deformation below recrystallization temperature; induces strain hardening and distorted grains, reducing ductility.

Hot working

Deformation above recrystallization temperature; simultaneous recrystallization prevents strain hardening, enabling large shape changes and grain refinement.

Grain growth

Occurs if material is held at/above recrystallization temperature long enough; larger grains reduce mechanical properties—control time/temperature to halt growth.

Insoluble composites

Constituents retain separate identities.

Solid solutions

Substitutional (solute replaces host atoms) or interstitial (solute occupies lattice gaps).

Intermetallic compounds

Defined stoichiometry with ionic/covalent bonds—hard and brittle.

Metals

Conductivity via free electrons; defects and temperature increases reduce conductivity.

Covalent materials

Conductivity depends on bond strength; semiconductors (Si, Ge) are doped to form n‑type or p‑type materials.

Ionic materials

Electron localization makes them insulators when dry; ion movement in solution enables conductivity when wet.

Mechanical properties

Strength, rigidity, fracture resistance, vibration/impact endurance.

Physical characteristics

Weight, electrical/thermal properties, appearance.

Service-environment features

Performance under temperature extremes, corrosion resistance.

Metallic materials

Exhibit luster, high electrical/thermal conductivity, and ductility.

Nonmetallic materials

Generally weaker, less ductile, lower density, and have poor conductivity.

Advanced materials

Engineered plastics, composites, ceramics; selection often driven by cost, product lifetime, environmental impact, energy requirements, and recyclability.

Physical properties

Characteristics that distinguish one material from another (density, melting point, optical, thermal, electrical, magnetic).

Mechanical properties

Define how a material responds to applied loads (strength, ductility, toughness); results depend on testing methodology.

Stress (σ)

Force per unit area (σ=W/A); modes include tensile, compressive, and shear.

Strain (ε)

Deformation relative to original length (ε=ΔL/L).

Loading modes

Tension, compression, shear each produce characteristic deformation patterns.

Static tests

Apply constant loads to characterize material behavior.

Tensile test

Yields stress-strain curve with proportional limit, yield strength, ultimate tensile strength, fracture strength, ductility, toughness.

Compression & bending tests

Determine modulus of elasticity and modulus of rupture.

Hardness tests

Provide relative strength indicators.

Elastic deformation

Reversible lattice distortion up to the elastic (proportional) limit; slope of σ-ε is Young's modulus (E).

Plastic deformation

Permanent slip via dislocation motion once yield stress exceeded; when no clear yield point, 0.2 % offset yield strength defines onset of plasticity.

Yield strength

Stress at onset of plastic flow, defined by upper/lower yield points or offset method.

Ultimate tensile strength (UTS)

Maximum stress before necking.

Fracture strength

Stress at final failure; in ductile materials < UTS (necking), in brittle materials occurs without plasticity.

Ductility

Measured by percent elongation and percent reduction in area.

Toughness

Energy per unit volume absorbed to fracture; area under the entire σ-ε curve.

Engineering stress/strain

Based on original dimensions; shows drop after necking.

True stress/strain

Accounts for instantaneous dimensions; continues to rise post‑necking; true strain is the integral of incremental strains.

Strain hardening

Increase in strength/hardness from dislocation interactions during plastic deformation.

Strain‑hardening exponent (n) and strength coefficient (K)

Quantify material's work‑hardening behavior.

Damping capacity

Ability to convert mechanical vibration energy into heat; measured by area between unloading/reloading loops in the plastic region.

Compression test

Evaluates materials under compressive loads; wide specimens prevent buckling.

Bending tests (three‑ and four‑point)

Determine flexural modulus and flexural strength for brittle materials.

Hardness

Resistance to indentation; correlates with tensile strength (~500× Brinell number).

Brinell test

Steel/carbide ball under 500-3000 kg; BHN from indentation diameter.

Rockwell test

Two‑stage load-depth measurement; Rockwell number from depth increment.