Patent US3763697A successfully refreshed from Google Patents.
US3763697A
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Method and apparatus for determining stress
Assignee: STURM STRESS Inc
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Filing: 1970-04-15
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Granted: 1973-10-09
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Expires: 1990-04-15
Abstract
Abstract A method and apparatus for non-destructively determining the total stresses in a body wherein an indentation is made in the surface of the solid body and the internal stresses determine the contour of the resulting permanent indentation as opposed to the contour of the indentation that would have remained if there were no stresses in the body. The difference in such coutours is analyzed to determine the amount of stresses and the orientation of such stresses without the physical destruction of the solid body. The material itself will indicate the total stresses (residual plus load) in the surface of the material, by the characteristics of the deformation or flow of the material under a suitable applied pressure substantially normal to the surface. The apparatus includes an indentor having a carriage and a plunger moveably carried by the carriage. The plunger is provided with a prescribed contoured tip; and a prime mover, capable of applying the same force successively to the plunger, is provided to drive the plunger. A profilometer which can be mounted on the carriage for alternate use with the plunger, reads the contour created by the tip and compares the same with similar indentations made in an unstressed sample.
Inventors
- 👤 R Sturm
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 20:21
CPC Classifications
G; G01; G01B; G01B5/00; G01B5/30; G01N; G01N3/00; G01N3/40
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
138 words
In a method of determining the stresses at a selected point in a first solid body existing adjacent the surface of said body, the steps of pressing an instrument inwardly from said surface into said first solid body with sufficient force to deform permanently the solid body and thereby create a first crater in its surface, and thereafter removing the instrument from the deformed portion of said solid body to ascertain the dimensions and orientation of said first crater, creating a second crater under substantially identical conditions in the surface of a second solid body of the same material and same hardness to said first solid body and in which the stresses are known, anD comparing the dimensions of said two craters for ascertaining the magnitude, sense and direction of the principal stresses in said first solid body.
Claim 2
Dependent Claim
138 words
In a method of determining the stresses at a selected point in a first solid body existing adjacent the surface of said body, the steps of pressing an instrument inwardly from said surface into said first solid body with sufficient force to deform permanently the solid body and thereby create a first crater in its surface, and thereafter removing the instrument from the deformed portion of said solid body to ascertain the dimensions and orientation of said first crater, creating a second crater under substantially identical conditions in the surface of a second solid body of the same material and same hardness to said first solid body and in which the stresses are known, anD comparing the dimensions of said two craters for ascertaining the magnitude, sense and direction of the principal stresses in said first solid body.
Claim 3
Dependent Claim
58 words
The method set forth in claim 1 wherein the steps of ascertaining the amount and orientation of the first crater includes photographing both of said craters perpendicular to the axes of both craters and under identical conditions and measuring the differences between the maximum and minimum diameters of the rims of said craters depicted in the resulting photographs.
Claim 4
Dependent Claim
139 words
The method set forth in claim 1 wherein the two principal stresses are compared according to the following formulae: ( sigma 3 - sigma 2)/ Tau 0 M (D/d - 1) ( sigma 3 + sigma 2)/2 Tau 0 3/ Square Root 2 (1 - D02/Dd) - (M2/4 Square Root 2) (D/d - 1)2 where sigma 3 algebraic maximum stress in the surface of the material, in direction of D in the first body sigma 2 stress at right angle to sigma 3 in the surface of the material of the first body D maximum diameter of the rim in the first body D0 diameter of the rim in the second body where stress is known to be zero d minimum diameter of indentation in the first body Tau 0 shear flow strength of material M a calibration consant.
Claim 5
Dependent Claim
22 words
The method set forth in claim 1 wherein said craters are initially conical and have apex angles of from 135* to 160*.
Claim 6
Dependent Claim
24 words
The method set forth in claim 1 wherein the surface of said first solid body is polished in an area of said selected point.
Claim 7
Dependent Claim
15 words
The method set forth in claim 1 wherein said instrument initially creates a circular crater.
Claim 8
Dependent Claim
15 words
The method set forth in claim 1 wherein said instrument initially creates a square crater.
Claim 9
Dependent Claim
15 words
The method set forth in claim 1 wherein said instrument initially creates a hemispherical crater.
Claim 10
Dependent Claim
16 words
The method set forth in claim 1 wherein said instrument initially creates a cone shaped crater.
Claim 11
Dependent Claim
27 words
The method set forth in claim 1 wherein the instrument has a substantially symetrical end for projecting into and creating said first crater in said first body.
Claim 12
Dependent Claim
30 words
The method set forth in claim 10 wherein said surface is substantially flat and said first crater is created by moving the instrument along a path perpendicular to said surface.
Claim 13
Dependent Claim
98 words
An instrument for measuring stress comprising an indentor and a profilometer, said indentor including a base, a frame, a yieldable fulcrum carried by said frame, a plunger carried by said fulcrum in a position normal to the surface of a solid body to be measured, an indicator for detecting the extent of force on said plunger and means for moving said plunger with respect to said base, said indentor and said profilometer being adapted to be carried by said base and being selectively moveable into registry with the same axis normal to the surface of said solid body.
Claim 14
Dependent Claim
98 words
An instrument for measuring stress comprising an indentor and a profilometer, said indentor including a base, a frame, a yieldable fulcrum carried by said frame, a plunger carried by said fulcrum in a position normal to the surface of a solid body to be measured, an indicator for detecting the extent of force on said plunger and means for moving said plunger with respect to said base, said indentor and said profilometer being adapted to be carried by said base and being selectively moveable into registry with the same axis normal to the surface of said solid body.
Claim 15
Dependent Claim
22 words
An instrument as in claim 12 wherein said profilometer includes a microscope and a camera mounted for taking pictures through said microscope.
Claim 16
Dependent Claim
37 words
An instrument as in claim 12 including a dial gage carried by said frame and biasing means for biasing said plunger, said dial gage indicating the amount of force of said plunger with respect to said frame.
Claim 17
Independent Claim
73 words
A method of determining stresses in metals comprising, forming an indentation with a circular indentor in the surface of a first metal specimen having unknown stresses to obtain a first indentation response, indenting, with an identical indentor, a metal specimen having known stresses to obtain a second indentation response, and comparing the length of the maximum and minimum diameters of said first indentation response to the average diameter of the second indentation response.
Claim 18
Independent Claim
73 words
A method of determining stresses in metals comprising, forming an indentation with a circular indentor in the surface of a first metal specimen having unknown stresses to obtain a first indentation response, indenting, with an identical indentor, a metal specimen having known stresses to obtain a second indentation response, and comparing the length of the maximum and minimum diameters of said first indentation response to the average diameter of the second indentation response.
Claim 19
Dependent Claim
144 words
In a method of determining the stresses at a Selected point in a first solid body existing adjacent the the surface of said body, said first solid body having stresses therein, the steps of pressing an instrument inwardly from said surface into said first body after the body has been stressed and with sufficient force to deform permanently the solid body and thereby create a first crater in its surface, and thereafter removing the instrument from the deformed portion of said solid body, creating a second crater under substantially identical conditions in the surface of a second solid body of the same material and hardness to said first solid body and in which the stresses are known, and obtaining the magnitude of the principal stresses in said first solid body by physical measuring and comparing the diameters of the rims of said two craters.
Claim 20
Dependent Claim
144 words
In a method of determining the stresses at a Selected point in a first solid body existing adjacent the the surface of said body, said first solid body having stresses therein, the steps of pressing an instrument inwardly from said surface into said first body after the body has been stressed and with sufficient force to deform permanently the solid body and thereby create a first crater in its surface, and thereafter removing the instrument from the deformed portion of said solid body, creating a second crater under substantially identical conditions in the surface of a second solid body of the same material and hardness to said first solid body and in which the stresses are known, and obtaining the magnitude of the principal stresses in said first solid body by physical measuring and comparing the diameters of the rims of said two craters.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-10-08 | 1977-04-09 | 1977-10-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-10-08 | 1981-04-09 | 1981-10-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-10-08 | 1985-04-09 | 1985-10-09 | $7700.00 | Window Closed / Lapsed |