Bench-mounted, self-contained unit that allows a practical examination of Hertz’s theories of contact between materials.
Key Features
• Helps engineers to study and predict contact shapes between common machined surfaces and materials
• Compact, self-contained unit - needs no electricity or external services
• Uses fl exible material to produce magnifi ed and easily viewed results
• Controllable hydraulic pressure system with gauge for repeatable results
• Simple design for ease of use • Variable relative contact angles and pressures for a range of experiments
Description
The Hertzian Contact Apparatus is a self-contained and easy-to-use unit that shows the nature of contact between two surfaces. It compares experiment results with predictions based on Hertz’s original theories. This helps engineers to predict contact areas between common machined surfaces and materials, for example diff erent types of bearings.
The apparatus has two pads with curved contact surfaces. The upper pad (made of a transparent plastic material) has a compound radius. The lower pad (made of an opaque fl exible material) has a simple radius. A handoperated hydraulic pump and cylinder force the two pads together. Students may rotate the lower pad, a pointer shows the angle of rotation. This allows a study of the eff ect of diff erent relative curvatures.
A contact shape (or ‘zone’) forms between the pads. The contact zone may be circular or elliptical, depending on the relative angular position of the two pads. Supplied is a transparent scale to measure the contact shape and angle.
Locknuts on the threads of the pump work to limit the maximum pressure, preventing damage to the equipment.
Learning Outcomes
• The eff ect of varied pressure with constant angle
• The eff ect of varied angle (diff erent relative curvature) with constant pressure
