System and method for fatigue forecasting and strain measurement using Integral Strain Gauge (ISG)

Abstract

The present invention relates to means, system and method for measurement of stress strain and fatigue forecasting by the means of Integral Strain Gauges (ISGs) capable of recording information from a surface of a tested object, mathematical processor for analysis of the information recorded on the surface of such gauges. Integral Strain Gauges produced from a custom made reaction sensitive materials.

1 . Method of measurement stress-strain and life time prediction within a test object including following elements and procedural steps:
 at least one Integral Strain Gauge (ISG) whereas creation of said gauge chosen to enhance sensitivity of the plain of the said gauge selected based on the mechanical properties of a tested element;   attachment of the said gauge on the surface of the tested element allowing transmission of stress reaction and further recording of said reaction on the surface of the ISG;   calibration tests of an ISG incorporate attachment of the ISG on the surface of a specimen, stress loading of the specimen and the reaction reading for the purpose of creation of calibration dependency in a form of mathematical equation;   creation of a fatigue curve incorporates attachment of an ISG on the surface of the tested element, stress loading of the sample till the point of destruction and the reaction reading for the purpose of creation of fatigue curve in a form of mathematical equation;   life time prediction incorporates attachment of an ISG on the surface of the tested element and reaction reading pertaining the maximum strain level recorded on the surface of the ISG and subsequent calculation of number of cycles prior to part's destruction.   
   
   
       2 . ISG as set forth in  claim 1 , being attached on the surface of a loaded element bearing no external connections to its surface for the reaction reading or fixation purposes. 
   
   
       3 . Calibration tests as set forth in  claim 1 , further comprising a step of recording of sets of relationships γ−N pertaining reaction on a surface of an ISG for each predetermined number of cycles under a strain force applied against the specimen. 
   
   
       4 . Calibration tests as set forth in  claim 3 , having constant amplitude of deformation during the entire calibration stage. 
   
   
       5 . Calibration specimen as set forth in  claim 1 , comprised of an inner elastic rod and an outer working shell of an amorphous material attached firmly to each other. 
   
   
       6 . Calibration dependency as set forth in  claim 1 , described by means of a mathematical equation derived from sets of values of shear deformation and tangential stress computed based on the set of γ−N relationships for a different grade of ISG reaction. 
   
   
       7 . Mathematical equation as set forth in  claim 6  incorporates dependency between variables of:
 N—number of cycles of the corresponding ISG reaction;   τ—amplitude of tangential stress;   D—level of fatigue damage of the sample material
 which corresponds to the ISG reaction R; 
   
     and is explicitly defined in the equation of 
     
       
         
           
             
               N 
               = 
               
                 K 
                 [ 
                 
                   
                     1 
                     
                       τ 
                       - 
                       
                         D 
                         * 
                         C 
                       
                     
                   
                   - 
                   
                     
                       c 
                       1 
                     
                     
                       τ 
                        
                       
                         ( 
                         
                           
                             c 
                             1 
                           
                           - 
                           
                             D 
                              
                             
                                 
                             
                              
                             C 
                           
                         
                         ) 
                       
                     
                   
                 
                 ] 
               
             
             , 
           
         
       
     
     where C, c 1 , K—are constants of the present equation. 
   
   
       8 . Creation of a fatigue curve as set forth in  claim 1 , includes stress loading of elements on multiple levels of strain conducted till the final destruction of elements on each level of said strains where the number of cycles prior to sample destruction and corresponding ISG reaction is recorded for each trial. 
   
   
       9 . Fatigue curve as set forth in  claim 8 , is created based on the computational analysis of the calibration dependency, values of the shear deformation that corresponds to the maximum level of intensity of the reaction recorded on the surface of the ISG. 
   
   
       10 . Fatigue curve as set forth in  claim 8 , is explicitly defined as a dependency having a number of variable parameters including number of cycles prior to parts destruction, maximum magnitude of micro-level strains, constants of the calibration dependency, constants pertaining mechanical properties of the tested element. 
   
   
       11 . Life time prediction stage as set forth in  claim 1  incorporates reading of maximum intensity reaction from the surface of the ISG attached to the surface of a tested sample, recording of the number of cycles preceding said reaction, engagement of a curve of the calibration dependency coordinates corresponding to the said reaction, and subsequent resolution for the finite number of cycles prior to destruction of the tested sample having the sample subjected to a constant level of strain and predetermined number of cycles. 
   
   
       12 . Life time prediction stage as set forth in  claim 1  incorporates reading of maximum intensity reaction from a surface of the ISG attached to a tested sample following block stages, computation of a number of cycles of loading corresponding to a present stage of a block loading, computation of values of a maximum strain and subsequent resolution for the finite number of cycles prior to destruction of a tested sample by substitution to an equation of a fatigue curve having the level of strain changing according to a set block of loads and a predetermined number of blocks phases. 
   
   
       13 . Life time prediction stage as set forth in  claim 1  incorporates reading of maximum intensity reaction from a surface of the ISGs of a variable sensitivity attached to a tested object, recording timings of appearance of reaction of a similar intensity, correlating such timings to a number of cycles of loading, solving the system of equations for a value of a maximum strain and subsequent resolution for the finite number of cycles prior to destruction of a tested element by substitution to an equation of a fatigue curve having the level of strain and the corresponding number of cycles is changing in random.