Instrument for detecting the instant at which a crack begins in a mechanical strength test of a ferromagnetic metal
First Claim
1. Instrumentation for detecting the beginning of cracking in a mechanical fracture test of a ferromagnetic material sample, said sample having a notch (10) running across it for providing a preferred orientation for cracking under impact and being held and subjected to impact in an apparatus including an impact member disposed for producing cracks in said orientation at said notch, a start-stop time measuring device and means for starting said time measuring device in response to impingement of said impact member on said sample, comprising means (26) for magnetizing said sample in a manner producing magnetic lines of force in said sample running from one side of said notch to the otherand a magnetic probe (23) adjacent to and spaced from said sample disposed and connected for stopping said time measuring device in response to a magnetic field change produced by the beginning of a crack in said sample.
1 Assignment
0 Petitions
Accused Products
Abstract
The moment of beginning of fracture in breaking strength tests of ferromatic samples (7) is detected by the spreading of a magnetic field out of the incipient crack in the magnetized sample by means of a magnetic probe (23). Until the beginning of the crack, the magnetic field runs through the magnetized sample. The voltage induced in the magnetic probe at the moment the crack starts is used to stop a time measuring counter which was reset and turned on at the beginning of the stressing of the sample.
9 Citations
11 Claims
-
1. Instrumentation for detecting the beginning of cracking in a mechanical fracture test of a ferromagnetic material sample, said sample having a notch (10) running across it for providing a preferred orientation for cracking under impact and being held and subjected to impact in an apparatus including an impact member disposed for producing cracks in said orientation at said notch, a start-stop time measuring device and means for starting said time measuring device in response to impingement of said impact member on said sample, comprising means (26) for magnetizing said sample in a manner producing magnetic lines of force in said sample running from one side of said notch to the other
and a magnetic probe (23) adjacent to and spaced from said sample disposed and connected for stopping said time measuring device in response to a magnetic field change produced by the beginning of a crack in said sample.
Specification