Technology and Practical Use of Strain Gages

Keil, Stefan

Technology and Practical Use of Strain Gages

With Particular Consideration of Stress Analysis Using Strain Gages

September 2017
  • 512 pages
  • 14 figures
  • 12 tables
  • Hardcover
  • English
ISBN: 978-3-433-03138-4
available, free shipping

Prices incl. VAT

Table of contents

1 Historical Review

2 Fundamentals of strain gage technology

2.1 Measurement principle and structure

2.2 Sensitivity

2.3 Transverse sensitivity

2.4 Temperature effect

2.5 Mechanics of the strain gage

2.6 Influence of pressure

2.7 Dynamic behavior

2.8 Heat dissipation

2.9 Measuring at elevated temperatures

2.10 Stress gages

3 Installation of strain gages

3.1 Preparatory work

3.2 Methods of fastening

3.3 Remarks on some measurement object materials (Glas, enamel, glaced porcelain, Concrete, Wood, Plastics)

3.4 Measurement point protection

3.5 Quality tests of the strain gage installation

4 The Wheatstone bridge circuit

4.1 Circuit principle

4.2 Basic equation of the bridge circuit

4.3 Temperature compensation

4.4 Limit of the bridge signal resolution

4.5 Examples of some elementary bridge circuits

5 Adjustment and compensation circuits

5.1 General

5.2 Compensation of zero shift with temperature change and zero adjustment

5.3 Compensation of temperature effects on the sensitivity and linearization measures

5.4 Adjustment of the characteristic value

5.5 Creep compensation

5.6 Full bridge circuits connected in parallel

6 Cable between strain gage bridge circuit and measuring instrument

6.1 Basics

6.2 Ohmic resistance of the cable

6.3 Influence of cable capacitance

6.4 Full-bridge connection in four-wire technology

6.5 Six-wire circuit

6.6 Dual channel principle

6.7 Connection of half and quarter bridges

6.8 Protection against disturbing influences

7 Signal processing

7.1 Introductory viewing

7.2 Analog instrumentation amplifier

7.3 Digital amplifier concepts

7.4 Compensation method

7.5 Multi-point Measurement

8 Calibration devices for measurements with strain gages

8.1 Introduction

8.2 Measurement chain

8.3 Characteristic and sensitivity

8.4 Calibration of the entire measuring chain as a measuring device

8.5 Compensators

8.6 Transducers

8.7 Calibration measures

8.8 Calibration of measuring arrangements with self-installed strain gages

9 Determination of mechanical stresses from strains measured with strain gages

9.1 Introduction

9.2 Terms of stress and strain

9.3 Elastic deformation and stress of a tensile rod under uniaxial tensile loading

9.4 The biaxial stress state

9.5 Mohr?s Circle

9.6 Deformation circle

9.7 Types of rosettes and grid notation

9.8 Evaluation formulas for 0°/45°/90° strain-gage rosettes

9.9 Evaluation formulas for 0°/60°/120° strain-gage rosettes

10 Application examples of elastic deformation

10.1 Initial considerations

10.2 Principal directions are known

10.3 Stress analysis for unknown principal directions

10.4 Simultaneous measurement of multiple load components

10.5 Diaphragm rosettes

11 Determination of thermal stresses

11.1 Emergence of thermal stresses

11.2 Sensing the prevented thermal expansion at identical temperatures at the compensation gage and the active strain gage

11.3 Determination of the restricted thermal expansion by computational correction of the measured values with previously measured thermal outputs on dummies

11.4 Determination of the restricted thermal expansion by mathematical correction with the thermal outputs determined at the original measurement object

11.5 The ?reversible? strain gage

11.6 Separation of the mechanical strain from the thermal strain

11.7 Compensated half-bridge strain gage with compensating resistor

12 Strain gages as a means for experimental determination of residual stresses

12.1 Preliminary observation

12.2 Cutting down method

12.3 Layer removal method

12.4 Ring-core method

12.5 Hole-drilling method

13 Stress analysis using strain gages in the elasto-plastic deformation range

13.1 Introduction

13.2 Equivalent state with elastic deformation

13.3 Elasto-plastic deformation

13.4 Stress analysis

13.5 Practical Example of application

13.6 Tensorial representation of the elasto-plastic deformation

14 Strength theories

14.1 Preview

14.2 Concept of effective stress

14.3 Experimental results

14.4 Maximum stress theory

14.5 Maximum shear theory

14.6 Extended shear theory

14.7 Plastic potential theory

14.8 Distortion energy theory (shape changing theory)

14.9 Octahedral plane shear stress theory


Subject Index