EML 4930/5930 Advanced Materials Forging EML 4930/5930 Advanced Materials

Classification Of Deformation Processes Based on temperature: Cold Working, Hot Working, Warm Working Cold Working: Work Temp < 30% Melting Point of Material (Absolute Units) Number of dislocations Strain Hardening To relieve stresses annealing is usually done. Can get good surface finish and dimensional tolerance. The practical application of mathematics and science to create, design, test, improve, and develop knowledge, research, money, business, economics, and technology. This is why engineering is such a challenging and demanding field of study: It involves areas of expertise that continue to evolve independently yet are required to perform together as part of the engineering process. Thus, an engineer must be expert in many areas, must know how to communicate knowledge between those areas, and must apply that knowledge to create, design, study, research, and invent all kinds of things. It is not uncommon for engineers to begin their careers as mathematicians, applied scientists, or even economists

Classification Of Deformation Processes Hot Working: Work Temp > 60% Melting Point of Material (Absolute Units) Metal has lower strength Recrystallization and grain growth can have large deformation Poor dimensional control and surface finish The practical application of mathematics and science to create, design, test, improve, and develop knowledge, research, money, business, economics, and technology. This is why engineering is such a challenging and demanding field of study: It involves areas of expertise that continue to evolve independently yet are required to perform together as part of the engineering process. Thus, an engineer must be expert in many areas, must know how to communicate knowledge between those areas, and must apply that knowledge to create, design, study, research, and invent all kinds of things. It is not uncommon for engineers to begin their careers as mathematicians, applied scientists, or even economists

Classification Of Deformation Processes Based on temperature: Warm Working: Work Temp > 30% but < 60% Melting Point of Material (Absolute Units) Forces lower than hot but more than cold Correct choice saves time and energy The practical application of mathematics and science to create, design, test, improve, and develop knowledge, research, money, business, economics, and technology. This is why engineering is such a challenging and demanding field of study: It involves areas of expertise that continue to evolve independently yet are required to perform together as part of the engineering process. Thus, an engineer must be expert in many areas, must know how to communicate knowledge between those areas, and must apply that knowledge to create, design, study, research, and invent all kinds of things. It is not uncommon for engineers to begin their careers as mathematicians, applied scientists, or even economists

Classification Of Deformation Processes Based on Flow behavior: Modeling is based on the type of flow Continuous Flow Forging (Shape remains same in the work region) Quasi-Static Rolling Wire Drawing Extrusion The practical application of mathematics and science to create, design, test, improve, and develop knowledge, research, money, business, economics, and technology. This is why engineering is such a challenging and demanding field of study: It involves areas of expertise that continue to evolve independently yet are required to perform together as part of the engineering process. Thus, an engineer must be expert in many areas, must know how to communicate knowledge between those areas, and must apply that knowledge to create, design, study, research, and invent all kinds of things. It is not uncommon for engineers to begin their careers as mathematicians, applied scientists, or even economists Based on Stress State: Direct Compression (Forging / Extrusion / Rolling) Indirect Compression (Wire Drawing)

Some basic quantities during forming A bar is halved in length; A bar is doubled in length; Engineering Strain True Strain Reduction in area

FORGING Shapes are formed by application of compressive forces in a press (very high tonnage) can be hot or warm forming

Open Vs Closed Die Forging Open die forging is done for general shape whereas closed die forging is meant for close tolerance parts

Process Design The design of bulk forming process involves an understanding of the material properties and forces required to obtain the finished shape. Some important variables are 1) Temperature 2) Strain 3) Strain-rate 4) Stress 5) Friction 6) Yielding and Hardening

Temperature Effect When a material deforms, work is done and is transformed as heat in the body. If we assume adiabatic conditions, then the temperature rises W = Mechanical work / Volume ρ = Density Cp = Heat Capacity

STRAIN Since the strains are large use logarithmic strain For Forging Reduction in area For 3-D state

STRAIN-RATE Strain-rate determines stresses at high temperature an also the ability to fail.

STRESS Stress determines forces needed to form; press tonnage Stress determines how the material responses to failure. Average Pressure pavg = F/A (Compressive) For wire drawing σavg = F/A (Tensile) Effective Stress

FRICTION It is a very important factor, often overlooked, also not easy to measure or control (lubrication). Avoid new surface creation. Coulomb's Law, τF = μp (μ between 0.4 – 0.577) Flow Model,

Forging An important design criteria is to determine the pressure distribution over the die. Using Coulomb's law we can determine Where σ0 is Flow Stress

Types of Friction Sliding Friction Mean forging pressure Total forging load W = Width of the forging (normal to the diagram)

Types of Friction Sticking Friction Pressure distribution Mean forging pressure Total forging load W = Width of the forging (normal to the diagram)

Example Consider a load 1" × 1" × 6" to be pressure between flat dies to 1/4" × 4" × 6". Flow stress = σ0 = 1000 psi. μ = 0.25 Calculate maximum pressure and forging load for (i) Sliding friction (ii) Sticking friction

Example Sliding Friction lb

Example Sticking Friction For simplicity, we calculate the forging load on the assumption that the pressure distribution is based on 100 percent sticking friction.