445 Midterm

Flow Curve

Describes the property of metals known as strain hardening.

What type of stress-strain relationship do room temperature metals expereince?

Elastic and strain hardening relationship.

Inside Micrometer

Used to measure inside dimensions of a part.

Depth Micrometer

Used to measure the depths of holes.

Cutoff Length

A filter that separates waviness from roughness deviations in the measurement of surface roughness.

Static Stress Types

The three basic types are Compression, Shear, and Tensile.

Strength Coefficient and Strain Hardening Exponent

Nearly identical values obtained from tensile and compression tests for a given metal.

Precision

The degree of repeatability in the measurement process.

Graduated Measuring Devices

Measurement instruments such as slide caliper, vernier caliper, and steel rule.

Mold Shift

Not a defect in sand casting caused by sidewise displacement of the core before solidification.

Fluidity factors of molten metal

Pouring temperature above melting point, alloy composition, viscosity, and heat transfer.

Permanent Mold Casting Limitation

The need to open the mold to retrieve the part is a limitation not applicable to expendable mold casting.

Quality Properties of Sand Mold

Includes Strength, Permeability, Thermal Stability, Collapsibility, and Reusability.

Investment Casting Advantages

Provides close dimensional control and allows for casting complex parts.

Expendable Mold Processes

Investment casting and sand casting.

Semicentrifugal Casting Examples

Wheels and pulleys.

Permanent Mold Operations

Include centrifugal casting and slush casting.

Precision-Casting Process Example

Investment casting

Strain Rate Sensitivity Exponent

Does not decrease with increasing temperature.

Lubricants for Hot vs Cold Working

Lubricants used in hot working are not the same as those used in cold working.

When is strain rate sensitivity greatest?

During hot working conditions.

Sticking Friction

Occurs when work surface adheres to tool surface, related to shear flow stress exceeding friction stress.

What is applied force in an extrusion operation based on?

Average flow stress

Warm vs Cold Working Line

Taken at 0.3Tm relative to the melting temperature.

Near Net Shape Processes

Processes that require little or no additional machining to complete the part.

No-Slip Point

In rolling, it's where work velocity equals roll velocity.

Reducing Force in Rolling

Achieved by using hot rolling, reducing draft, and using smaller diameter rolls.

Thread Rolling Advantages

Includes higher production rates, better material utilization, and stronger threads due to work hardening.

Average Flow Stress in Rolling Force

Used in computing rolling force.

Maximum Draft in Rolling Operation

Depends on the coefficient of friction and roll diameter.

Roll Piercing

A specialized hot working process for making seamless thick-walled tubes.

Impression-Die Forging

Requires significantly higher forces compared to open-die forging due to flash formation.

Shape Factor in Extrusion

Ratio of pressure required for a specific shape compared to round cross section.

Centerburst

An internal crack that develops from tensile stresses during extrusion.

Butt in Direct Extrusion

The portion of the billet that remains in the container and cannot be forced through the die.

Greater Extrusion Pressure Shape

A round tube shape with the same cross-sectional area requires more pressure than a round circle.

What does flow stress depend on during hot working?

Strain rate