When the material cannot displace under the exogenic action, its geometric shape and size will change, this kind of deformation called strain. When a material deforms, a reaction force of equal magnitude but opposite direction is generated inside to resist the external force. And this reaction force per unit area is defined as stress. Or due to the external factors(force, humidity change,etc.) the object is deformed, the internal forces are generated between the various parts of the object to resist the action of such external factors, and try to restore the object from the deformed position to the before deformed position.The internal force per unit area at a point of the cross section under investigation is called Stress. According to the directional relationship between stress and strain, stress can be divided into normal stress σ and tangential stress τ. The direction of normal stress is parallel to the direction of strain, and the direction of tangential stress is perpendicular to the strain. Besides, according to the different forms of load, stress can be divided into tensile and compressive stress, bending stress and torsional stress.
The stress meter can detect the birefringence of transparent and weakly colored materials, and accurately calculate the value of the birefringence whose optical path error does not exceed 10nm through the Senarmont compensation method. The distribution of birefringence is detected and analyzed by polarized light. The distribution and size of the refractive index directly reflect the distribution and size of the material stress.
The polariscope PSV-413 which provide by PTC Optics has a wide range of applications. The instrument can detect glass and plastic products from a horizontal or vertical angle, and mostly used for quality control. During the measurement process, the observation and measurement are mainly carried out by holding the measured object under polarized light.
The standard configuration of the PSV-413 includes a light source, a quarter wave plate (565nm) and a full wave plate (565nm) were placed between the analyzer and the polarizer. And the axis is 90 degrees to the polarization plane of the polarizer. In addition, there is a measuring device for the rotation angle on the top of the analyzer, where the scale value is 1 degree and the maximum measuring range is 180 degrees.
The stress meter is a machine for non-destructive testing of stress conditions, which is convenient for people to more intuitively distinguish the stress conditions of samples during the production process. At present, this equipment is widely used in the control of transparent plastic and glass products, which is convenient for measuring product stress timely and ensure and improve the product quality.
During the use of the stress meter, be sure to avoid strong light and avoid contact with chemicals.
