Comprehensive Program covering Strain Measuring Systems with a Focus on Plastics and Composites

This program is presented in a format which includes several hands-on laboratory exercises. Liberal use of demonstrations and case studies provides attendees with a first-hand opportunity to learn how to select the procedures and techniques best suited to their strain measurement needs including non-metallic materials.

Beginning with a review of stress analysis principles, the course moves to methods of locating stress concentrations in a complex strain field using modern optical techniques. Performance characteristics of the strain gage (strain gauge) and selection criteria come next, followed by several laboratory projects in which strain gages (strain gauges) are bonded, electrical connections completed, environmental protection applied and installation integrity verified on metals as well as plastic and composite samples. The strain data are then collected with measuring instrumentation and compared to calculated theoretical values. In a more advanced laboratory project, a basic weighing scale is constructed and calibrated. All attendees have an opportunity to use three popular adhesive systems during the construction of the laboratory projects.

Three of the ASTM Standards that are often used with characterizing the properties of plastics and composites including D3039 Poisson.s Ratio, D695 Compression and D5379 Shear Modulus are demonstrated and/or practiced during the class using the appropriate materials.

A thorough review of strain gage (strain gauge) instrumentation is augmented by numerous demonstrations and hands-on experiments which highlight important features of modern strain measuring instruments. The use of strain gages (strain gauge) and related instrumentation in transducer applications is also explored. Special-purpose sensors are reviewed, with emphasis on their application to strain measurements and structural test programs.

Provision is made for attendees to discuss their specific test requirements with members of the Micro-Measurements technical staff.

Topics include: 

Concepts of Stress and Strain

• Uniaxial and Biaxial Strain
• Hooke's Law
• Principal Stresses and Strains
• Superposition Concept

Full-Field Strain Measurements

• Locating Stress Concentrations
• Interpreting the Strain Field
• Selection and Applications of PhotoStress®

Strain Gage (Strain Gauge) Characteristics

• Backings and Sensing Elements
• Performance Characteristics

Gage Installation Techniques

• Bonding Methods
• Leadwire Installation
• Environmental Protection

ASTM Standards

• D3039 Poisson.s Ratio
• D695 Compression Demo
• D5379 Shear Demo

Transducers

• Design Considerations
• Bridge Circuits

Instrumentation Considerations

• Wheatstone Bridge Circuitry
• Bridge Excitation and Thermal Effects
• Leadwire Effects
• Bridge Balance Control
• Shunt Calibration and Calibrators
• Static/Dynamic Strain Measurement
• Switching and Multiplexing
• Electrical Noise Control
• Checkout and Troubleshooting

Case Histories