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Internal stress means that when the object is deformed due to external factors (force or humidity, temperature changes, etc.
), the internal force that interacts between the various parts of the object will be generated to resist the effect of such external factors.
The residual stress inside the object is caused by the uneven volume change of the macroscopic or microscopic organization inside the material
.
If the uneven internal stress remains in the glass container, the mechanical strength of the glass will be reduced, and problems such as cracking will easily occur in the production, use and storage of pharmaceutical packaging
.
Usually glass is an isotropic homogeneous material.
When there is internal stress, it will show anisotropy and produce birefringence of light
.
In this method, the birefringence optical path difference is measured by a polarizing stress meter, and the value of the optical path difference per unit thickness is used to represent the internal stress of the product
.
The measurement principle of birefringence optical path difference is that the white light emitted by the light source becomes linearly polarized light after passing through the polarizer.
The direction will be rotated by an angle of 0.
The value of the angle 0 (in degrees) is proportional to the birefringence optical path difference T of the test sample.
The relationship is: T=5650/180=3.
140.
When the stress is applied, this angle can be measured by rotating the analyzer, and the birefringence optical path difference T of the test sample can be measured
.
The measurement of internal stress is mainly used to control the annealing quality of medicinal glass containers
.
The technical requirements that the polarizing stress meter of the instrument device should meet: when using polarized light components and protective parts for observation, the brightness of the edge of the light field should not be less than 120cd/m"; the polarized light components used should ensure the degree of polarization at any point in the bright field.
Not less than 99%; the polarized field is not less than 85mm; a 565nm full-wave plate (sensitive color plate) and a quarter-wave plate can be placed between the polarizer and the analyzer, respectively.
The slow axis of the wave plate is the same as The polarization plane of the polarizer is 90°; the analyzer should be installed to be able to rotate relative to the polarizer and the full-wave plate or quarter-wave plate, and there is a measuring device for the rotation angle
.
The test sample for the determination method should be the product that has not been tested after annealing.
It must be placed in the laboratory for more than 30 minutes under the temperature conditions.
Gloves should be worn during the measurement to avoid direct contact with the test sample with hands
.
1
.
Determination of the colorless test sample Inspection of the bottom of the colorless test sample: Put the quarter-wave plate into the field of view, and adjust the zero point of the polarizing stress meter to make it appear as a dark field of view
.
Put the test product into the field of view, and observe the bottom from the mouth.
At this time, a dark cross will appear in the field of view.
If the stress of the test product is small, the dark cross will be blurred
.
Rotate the analyzer to separate the dark cross into two arcs moving in opposite directions.
As the dark area moves outward, blue-gray appears on the concave side of the arc, and brown appears on the convex side
.
If the stress value of a selected point is to be determined, rotate the analyzer until the blue-gray color at that point is just replaced by brown
.
Rotate the test sample around the axis to find the point of maximum stress, rotate the analyzer until the blue-gray is replaced by brown, record the rotation angle of the analyzer at this time, and measure the thickness of this point
.
Inspection of the side wall of the colorless test article: Put the quarter-wave plate into the field of view, and adjust the zero point of the polarizing stress meter to make it appear as a dark field of view
.
Put the test product into the field of view so that the axis of the test product is at 45° to the polarization plane.
At this time, different bright and dark areas appear on the sugar wall
.
Rotate the analyzer until the dark areas on the side walls converge, just completely replacing the bright areas
.
Rotate the test sample around the axis to determine the area of maximum stress
.
Record the placement angle of the analyzer in the maximum stress area, and measure the thickness of the two side walls respectively (record the sum of the wall thicknesses of the two side walls)
.
2.
Determination of colored test samples The inspection steps are the same as those of colorless test samples.
.
When there is no obvious blue and brown and the glass transmittance is low, it is difficult to determine the rotation end point of the analyzer, and the average method can be used to determine the accurate end point
.
That is to say, it is expressed as the average value of the sum of the rotation angle at which the dark area replaces the bright area and the total rotation angle at which the bright area just reappears
.
Result calculation.
One T/t=3.
148/t where 8 is the internal stress of the test product, nm/mm; T is the optical path difference of the tested part of the test product, nm; t is the tested part of the test product.
The total thickness of the light, mm; 8 is the rotation angle of the analyzer (when the maximum stress is measured); 3.
14 is the constant when using a white light source (effective length is about 565nm), and the analyzer rotates about 1" per 1".
in optical path difference 3.
14nm
.
), the internal force that interacts between the various parts of the object will be generated to resist the effect of such external factors.
The residual stress inside the object is caused by the uneven volume change of the macroscopic or microscopic organization inside the material
.
If the uneven internal stress remains in the glass container, the mechanical strength of the glass will be reduced, and problems such as cracking will easily occur in the production, use and storage of pharmaceutical packaging
.
Usually glass is an isotropic homogeneous material.
When there is internal stress, it will show anisotropy and produce birefringence of light
.
In this method, the birefringence optical path difference is measured by a polarizing stress meter, and the value of the optical path difference per unit thickness is used to represent the internal stress of the product
.
The measurement principle of birefringence optical path difference is that the white light emitted by the light source becomes linearly polarized light after passing through the polarizer.
The direction will be rotated by an angle of 0.
The value of the angle 0 (in degrees) is proportional to the birefringence optical path difference T of the test sample.
The relationship is: T=5650/180=3.
140.
When the stress is applied, this angle can be measured by rotating the analyzer, and the birefringence optical path difference T of the test sample can be measured
.
The measurement of internal stress is mainly used to control the annealing quality of medicinal glass containers
.
The technical requirements that the polarizing stress meter of the instrument device should meet: when using polarized light components and protective parts for observation, the brightness of the edge of the light field should not be less than 120cd/m"; the polarized light components used should ensure the degree of polarization at any point in the bright field.
Not less than 99%; the polarized field is not less than 85mm; a 565nm full-wave plate (sensitive color plate) and a quarter-wave plate can be placed between the polarizer and the analyzer, respectively.
The slow axis of the wave plate is the same as The polarization plane of the polarizer is 90°; the analyzer should be installed to be able to rotate relative to the polarizer and the full-wave plate or quarter-wave plate, and there is a measuring device for the rotation angle
.
The test sample for the determination method should be the product that has not been tested after annealing.
It must be placed in the laboratory for more than 30 minutes under the temperature conditions.
Gloves should be worn during the measurement to avoid direct contact with the test sample with hands
.
1
.
Determination of the colorless test sample Inspection of the bottom of the colorless test sample: Put the quarter-wave plate into the field of view, and adjust the zero point of the polarizing stress meter to make it appear as a dark field of view
.
Put the test product into the field of view, and observe the bottom from the mouth.
At this time, a dark cross will appear in the field of view.
If the stress of the test product is small, the dark cross will be blurred
.
Rotate the analyzer to separate the dark cross into two arcs moving in opposite directions.
As the dark area moves outward, blue-gray appears on the concave side of the arc, and brown appears on the convex side
.
If the stress value of a selected point is to be determined, rotate the analyzer until the blue-gray color at that point is just replaced by brown
.
Rotate the test sample around the axis to find the point of maximum stress, rotate the analyzer until the blue-gray is replaced by brown, record the rotation angle of the analyzer at this time, and measure the thickness of this point
.
Inspection of the side wall of the colorless test article: Put the quarter-wave plate into the field of view, and adjust the zero point of the polarizing stress meter to make it appear as a dark field of view
.
Put the test product into the field of view so that the axis of the test product is at 45° to the polarization plane.
At this time, different bright and dark areas appear on the sugar wall
.
Rotate the analyzer until the dark areas on the side walls converge, just completely replacing the bright areas
.
Rotate the test sample around the axis to determine the area of maximum stress
.
Record the placement angle of the analyzer in the maximum stress area, and measure the thickness of the two side walls respectively (record the sum of the wall thicknesses of the two side walls)
.
2.
Determination of colored test samples The inspection steps are the same as those of colorless test samples.
.
When there is no obvious blue and brown and the glass transmittance is low, it is difficult to determine the rotation end point of the analyzer, and the average method can be used to determine the accurate end point
.
That is to say, it is expressed as the average value of the sum of the rotation angle at which the dark area replaces the bright area and the total rotation angle at which the bright area just reappears
.
Result calculation.
One T/t=3.
148/t where 8 is the internal stress of the test product, nm/mm; T is the optical path difference of the tested part of the test product, nm; t is the tested part of the test product.
The total thickness of the light, mm; 8 is the rotation angle of the analyzer (when the maximum stress is measured); 3.
14 is the constant when using a white light source (effective length is about 565nm), and the analyzer rotates about 1" per 1".
in optical path difference 3.
14nm
.
