Method and equipment for determining conditions of stiction between a braking element and an element to be braked

Patent metadata

Field	Value
Publication number	US-11280721-B2
Application number	US-201716330364-A
Country	US
Kind code	B2
Filing date	Sep 5, 2017
Priority date	Sep 5, 2016
Publication date	Mar 22, 2022
Grant date	Mar 22, 2022

Abstract

Methods and equipment for determining conditions of adhesion between a first and a second mechanical element are disclosed. The mechanical elements are attached respectively to a first and second support, which are immersed in an electrolyte together with a counter-electrode and a reference electrode to form an electrochemical cell. The second mechanical element is a working electrode being connected to an insulated electric wire that is also connected to the counter-electrode. A first uncovered face of the second element is pressed against the first element. A potential is applied to the second element of at least one predetermined value and/or a predetermined electrical current. The method can include detecting the electrical current that is transmitted through the electrolyte as a function of the potential applied and/or the potential that is established as a function of the predetermined current.

First claim

The invention claimed is:

1. An article of equipment configured to determine conditions of stiction adhesion between two mechanical elements, the equipment comprising:
a stiction cell comprising:
a body made of an electrically non-conductive material and having a first support configured to receive a first of said mechanical elements; and
a slide slidably mounted on the body on a side of the body opposite to the first support, the slide comprising a second support configured to receive a second of said mechanical elements, the second support further comprising an insulated electric wire which is electrically connectable to the second mechanical element;

an electrochemical cell comprising said stiction cell, a counter-electrode, a reference electrode, and a container, the container being configured to hold an electrolyte and to enable said electrodes and said first and second supports provided with the said first and second mechanical elements to be immersed in the electrolyte; and
an electronic instrument to which the reference electrode, the counter-electrode, and the insulated electric wire are electrically connected such that the second mechanical element, when it is electrically connected to said insulated electric wire, comprises a working electrode of the electrochemical cell.

2. The equipment according to claim 1 , wherein the stiction cell further comprises a handling device configured to move the slide along guides of the body, wherein the handling device comprises:
a screw which is mechanically connected to said slide, and
a nut which is engaged by said screw and is mounted to the body.

3. The equipment according to claim 2 , further comprising a torque wrench configured to rotate said screw in such a way as to push the second support towards the first support by applying a predetermined torque to the screw.

4. The equipment according to claim 1 , further comprising a test bench comprising:
a support base configured to receive, in a fixed position, the first and second mechanical elements joined to each other,
a pusher carried by the support base and configured to apply increasing thrust to one of the said first and second mechanical elements, and
a tool configured to measure the thrust applied by the pusher.

5. The equipment according to claim 1 , wherein the slide comprises a metal bar and the second support comprises a block of an epoxy resin.

6. The equipment according to claim 1 , wherein the second support is configured to embed the second mechanical element leaving only one face thereof uncovered and arranged such that the face is flush with a front end of the second support facing the first support.

7. A method of determining conditions of adhesion between a first and a second mechanical element, the method comprising:
coupling the first mechanical element to a first support and the second mechanical element to a second support, the first and second support being positioned opposite one another and being axially movable;
embedding the second mechanical element within the second support, except for a first face of the second mechanical element that is not embedded in the second support and that is arranged flush with a front end of the second support facing towards the first support;
electrically connecting the second mechanical element to an insulated electric wire that protrudes from the second support;
pressing, with a first predetermined force, the first face of the second mechanical element against the first mechanical element;
pushing the second support towards the first support to realize a stiction cell comprising the first and the second mechanical elements and the first and second supports;
immersing, in an electrolyte, said first and second mechanical elements, said first and second supports, a counter-electrode, and a reference electrode in such a way as to form an electrochemical cell of which the second mechanical element comprises a working electrode;
electrically connecting the insulated electric wire, the counter-electrode and the reference electrode to an electrical generator;
carrying out, using the electrical generator, electrochemical tests, wherein the electrochemical tests comprise: applying progressively variable potentials between the working electrode and the reference electrode, or establishing a progressively variable electric current passage between the counter-electrode and the working electrode; and
detecting the electric current that is passed through the electrolyte between the second mechanical element and the counter-electrode.

8. The method according to claim 7 , wherein the electrochemical tests are chosen from the group consisting of:
OCP (“open circuit potential”) measures along time;
potentiostatic or potentiodynamic polarization curves;
chrono-potentiometric measures;
chrono-amperometric measures; and
any combination of the above;
wherein said electrochemical tests cause corrosive phenomena on the second mechanical element which establish chemical-physical conditions for the stiction phenomenon.

9. The method according to claim 7 , further comprising:
applying, in succession and to the second mechanical element, a first predetermined and constant potential for a first period of time and a second predetermined and constant potential for a second period of time; and
detecting the value of the electric current passing between the second mechanical element and the counter-electrode during the application of the first and second predetermined and constant potentials.

10. The method according to claim 7 , further comprising performing a chrono-potentiometric measurement that comprises:
passing a predetermined current between the working electrode and the counter-electrode; and
measuring the potential of the second mechanical element with respect to the reference electrode for a predetermined time.

11. The method of claim 10 , further comprising performing a potentiodynamic measurement from a first predetermined potential to a second predetermined potential using a fixed speed variation of the potential.

12. The method according to claim 7 , further comprising inducing corrosion of the first face of the second mechanical element by anodic dissolution.

13. The method according to claim 7 , wherein:
the first mechanical element comprises a first sample of first dimensions a friction material,
the second mechanical element comprises a second sample of second dimensions;
the first face of the second mechanical element having dimensions that are greater than those of the first mechanical element, a portion of the first face that exceeds the dimensions of the first mechanical element being masked with an electrically non-conductive material.

14. The method according to claim 7 , further comprising:
drying the stiction cell;
cooling the stiction cell at ambient temperature, such that the first face of the second mechanical element adheres to the first mechanical element due to stiction gluing;
mounting the stiction glued first and the second mechanical elements on a test bench;
detaching the second mechanical element from the first mechanical element with a pusher; and
measuring a second force, which is applied by the pusher during said detachment, said second force being an index of the extent of the stiction gluing.

15. The method according to claim 7 , further comprising:
applying the first predetermined force with a screw and a nut; and
applying a predetermined amount of torque to the screw with a torque wrench.

16. The method according to claim 7 , further comprising housing said electrochem

Assignees

• Itt Italia Srl

Inventors

• Sin Xicola Agustin
• Fedrizzi Lorenzo
• Andreatta Francesco
• De Nicolo Alessandro

Classifications

• G01N27/48

  using polarography, i.e. measuring changes in current under a slowly-varying voltage · CPC title

• G01N27/4161

  measuring the voltage and using a constant current supply, e.g. chronopotentiometry · CPC title

• G01N17/02 Primary

  Electrochemical measuring systems for weathering, corrosion or corrosion-protection measurement · CPC title

• G01N19/04 Primary

  Measuring adhesive force between materials, e.g. of sealing tape, of coating · CPC title

• B60T8/172

  Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters {(B60T8/17551 takes precedence)} · CPC title