What Is a Stress Analyzer?
A stress analyzer is an instrument used to determine the type of stress applied to a material.
There are several types of stress-measuring machines, each designed for specific purposes. This section broadly describes stress-measuring machines. Stress can be compressive or tensile. Excessive stress, whether compressive or tensile, can cause component damage. In addition to stresses from external mechanical forces, materials can also experience residual stresses due to processes like heat treatment or film formation.
Reinforcing materials like glass or steel can increase a product’s strength by intentionally creating residual compressive stress on the surface.
Uses of Stress Analyzers
Stress analyzers are employed in various fields, ranging from product development to heat treatment, film deposition, and glass strengthening. In research and development, these analyzers are utilized to assess component strength by determining the stress they endure and to optimize designs by reducing unnecessary material, thereby cutting weight and costs.
In the semiconductor industry, stress measurement is crucial for quality control, as various thin films are deposited on silicon wafers. Excessive stress can lead to film peeling.
Moreover, in glass tempering processes, stress measurement is conducted after the strengthening process to ensure increased compressive stress near the surface, enhancing the glass’s strength.
Principle of Stress Analyzers
The principle of a stress analyzer varies based on the measurement method. However, all analyzers detect the strain in the material under test. Strain refers to the stretching, shrinking, twisting, or deformation of a material under external force.
Stress is defined as force per unit area and is calculated by multiplying the material’s strain by its Young’s modulus. Therefore, stress analyzers indirectly measure stress by capturing the strain caused by external forces on a material and converting this data into stress values using Young’s modulus.
There are various methods for detecting strain, and stress analyzers are developed based on these different principles.
Types of Stress Analyzers
Stress analyzers come in various types, suited to the specific material and stress magnitude to be measured. Here are four typical examples:
1. Strain Gauges
Strain gauges are primarily used to measure stress in structural components. They detect strain through changes in electrical resistance. Strain gauge-based stress measurement is specific to the part where the gauge is attached.
These gauges are often used in conjunction with CAE for structural analysis verification.
2. Infrared Detection
Infrared stress measurement is another method for structural components. Material deformation due to external forces leads to surface temperature changes, a phenomenon known as thermoelastic effects.
This method involves detecting stress from temperature changes on the material’s surface due to strain. Unlike strain gauges, infrared stress measurement can assess a broader area.
3. Laser Beam Reflection
Laser light reflection is used for stress measurement in thin film deposition. Changes in the radius of curvature, due to substrate warping after deposition, are determined by comparing laser light reflection before and after deposition, thereby assessing film stress.
This technique is also used in evaluating semiconductor silicon wafers and tempered glass.
4. X-Ray Diffraction
X-ray diffraction measures residual compressive stress caused by heat or surface treatment of materials like steel. It utilizes the diffraction of X-rays scattered by irradiating materials with X-rays of a wavelength similar to the distance between atoms in a regularly arranged atomic structure.
Beyond stress measurement, X-ray diffraction is also used for material analysis, including qualitative and quantitative analysis, crystal size calculation, and lattice distortion assessment.