METHOD AND APPARATUS FOR MEASUREMENT OF INTERNAL FRICTION OF A MATERIAL

TECHNICAL FIELD
[0001] The present disclosure relates to the measurement of internal friction of a material, specifically for a steel strip.
[0002] In particular, the present disclosure relates to a method for measurement of internal friction of a material and to an internal friction measurement apparatus.

BACKGROUND
[0003] Background description includes information that may be useful in understanding the present subject matter. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed subject matter, or that any publication.
[0004] Internal friction as a measure of detection of microscopic motion of interstitial elements present in metal has been widely used in the industry. The internal friction is generally defined as dissipation of mechanical energy inside a solid material. In the solid material exposed to time-dependent load within an elastic deformation range, the internal friction usually means dissipation of the applied mechanical energy which leads to damping. This internal friction is necessary for the damping of the vibrations of the solids even though there is no support to damp the vibrations. This internal friction effect is believed to be caused by the jump processes of interstitial solute atoms in the vicinity of substitutional atoms, which is generally called a Snoek mechanism.
[0005] The measurement of a Snoek peak relaxation is a unique and powerful technique allowing quantitative examination on the behavior of interstitial solutes in body centered cubic (BCC) metals and has been applied to the determination of solubility and diffusivity of carbon and nitrogen in alpha-iron. The internal friction is one of the property which is due to the interaction of interstitial solute atoms and substitutional alloying elements. Thus, an internal friction measurement is one of the best methods to estimate the amount of solute carbon accurately. With the internal friction measurement, an accuracy of 1 ppm can be obtained.
[0006] The measurement of the Sonek peak is done by precision measurement apparatus by twisting a sample and measuring its damping in an oscillating amplitude of the sample at different temperatures. This type of measurement apparatus is very complex and, in general, difficult to maintain and is available at a very high cost.
[0007] Accordingly, there is a need in the art to provide a simplified approach and apparatus for measurement of the internal friction.

OBJECTS OF THE DISCLOSURE
[0008] Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed hereinbelow.
[0009] A general object of the present disclosure is to determine internal friction of a steel sample for estimating the presence of solute carbon (C) and Nitrogen (N) in the steel sample. In case of the steel sample, the condition of the appearance of stretcher stain marks (Luders Band) and shelf life of bake hardenable and dual phase steels need to be investigated for improving the properties of steel by optimizing its chemical composition and process parameters.
[0010] It is an object of the present disclosure is to measure the internal friction by measurement of linear damping distance of oscillating samples actuated by small bending (within the elastic limit).
[0011] These and other objects and advantages of the present disclosure will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present disclosure is illustrated.

SUMMARY
[0012] This summary is provided to introduce concepts related to the measurement of internal friction of a material, specifically for a steel strip. The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[0013] The present disclosure relates to a method for measurement of internal friction of a material. The method includes holding a sample on a sample holder in such a way that one end of the sample is rigidly held and other end is allowed to oscillate freely; heating the sample with a hollow cylindrical heater at defined temperature intervals; after each defined temperature interval, striking the other end, which is allowed to oscillate freely, with an electromagnetic actuator; measuring a linear distance of the other end by a proximity distance sensor; transforming the measured distance data in the form of sinusoidal function; and calculating damping in amplitude of the sinusoidal function due to an average internal friction of the sample for instantaneous temperature, for calculating the average internal friction of the sample at that instantaneous temperature.
[0014] In an aspect, the calculating of damping in the amplitude of the sinusoidal function includes:
logarithmic decrementing of the amplitude, d, which is defined as:

where Ai= Amplitude at ith cycle, and
Ai+n = amplitude at i+nth cycle; and
calculating average internal friction (IF) as:
.

[0015] In an aspect, the method further comprising plotting the internal friction data against the instantaneous temperature to build a Snoek peak, wherein Snoek peak is a characteristic measurement of the presence of solute elements in the material.
[0016] In an aspect, the capturing of linear distance of the other end by the proximity distance sensor is performed at megahertz frequency.
[0017] In an aspect, the method includes controlling power supply to the hollow cylindrical heater by an electronic controller based on a temperature of a thermocouple which is placed over the sample held in the sample holder.
[0018] In an aspect, the method includes controlling a vacuum of a sample chamber and an initial temperature by putting a chilling circuit inside the sample chamber, wherein the sample is partially held inside the sample chamber.
[0019] The present disclosure relates to an internal friction measurement apparatus. The internal friction measurement apparatus includes a sample holder for holding a sample in such a way that one end of the sample is rigidly held and other end is allowed to oscillate freely; a hollow cylindrical heater for heating the sample in a sample chamber at defined temperature intervals, wherein the sample is held by the sample holder inside the sample chamber; an electromagnetic actuator for striking the other end, which is allowed to oscillate freely, after each defined temperature interval; a proximity distance sensor positioned near the other end of the sample so as to measure a linear distance of the other end during oscillation; and a microcontroller. The microcontroller is to: receive measured distance data from the proximity distance sensor, transform the measured distance data in the form of sinusoidal function, and calculate damping in amplitude of the sinusoidal function due to an average internal friction of the sample for instantaneous temperature, for calculating the average internal friction of the sample at that instantaneous temperature.
[0020] In an aspect, the microcontroller is for:
logarithmic decrementing of the amplitude, d, which is defined as:

where Ai= Amplitude at ith cycle, and
Ai+n = amplitude at i+nth cycle; and
calculating average internal friction (IF) as:
.
[0021] In an aspect, the internal friction measurement apparatus includes a heater socket for controlling power supply to the hollow cylindrical heater based on a temperature of a thermocouple which is placed over the sample held in the sample holder.
[0022] In an aspect, the hollow cylindrical heater comprising glass wool surrounding the sample so as to maintain the temperature of the sample during measurement.
[0023] These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and methods that are consistent with the subject matter as claimed herein, wherein:
[0025] FIG. 1 illustrates a schematic diagram of an internal friction measurement apparatus, in accordance with an embodiment of the present disclosure; and
[0026] FIG. 2 illustrates the dimension of a steel sample for internal friction measurement, in accordance with an embodiment of the present disclosure;
[0027] FIG. 3 illustrates an electric circuit diagram of the internal friction measurement apparatus, in accordance with an embodiment of the present disclosure;
[0028] FIG. 4 illustrates a graph illustrating damping (decay in the amplitude) of the sample with respect to time due to the internal friction of the sample, in accordance with an embodiment of the present disclosure;
[0029] FIG. 5 illustrates a graph illustrating the determination of Snoek peak from the internal friction measurement data plotted against the different defined temperatures, in accordance with an embodiment of the present disclosure;
[0030]

DETAILED DESCRIPTION
[0031] The detailed description of various exemplary embodiments of the disclosure is described herein with reference to the accompanying drawings. It should be noted that the embodiments are described herein in such details as to clearly communicate the disclosure. However, the amount of details provided herein is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.

[0032] It is also to be understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and embodiments of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof.
[0033] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.
[0034] It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may, in fact, be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
[0035] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
[0036] Embodiments and/or implementations of the present disclosure described herein relate to the measurement of internal friction of material, specifically a steel strip. The present disclosure further relates to an internal friction measurement apparatus for measuring the internal friction, which is also referred to as ‘loss-angle’ of the steel strip. From the measurement of internal friction of the steel, the amount of solute interstitial particles like Carbon (C) and Nitrogen (N) can be estimated to the extent of reliable accuracy.
[0037] As mentioned above, the internal friction effect is believed to be caused by the jump processes of interstitial solute atoms in the vicinity of substitutional atoms, which is generally called a Snoek mechanism. In the Snoek mechanism, the measurement of Snoek picks is performed by measuring a linear distance of a free end oscillation of a sample at variable temperatures. Thus, in the present disclosure, the precision is avoided in torsional sample preparation as well as a simplified setup to lower the cost of internal friction measurement apparatus.
[0038] There are various ways to find out the damping (loss angle) caused due to the internal friction to find out the Snoek peak. The loss angle, Q-1, is generally denoted by:
Q-1 = ?W/2 pWF = tanF
where F = phase lag between stress and strain, and
?W/W = energy loss per cycle.

[0039] The measurement of loss of energy (?W/W) is done from the linear difference of its amplitude per cycle. The direct determination of ?W and W ratio can be done by careful measurement of the relative magnitudes of the input and output signals of the vibration from an induction type distance sensor.
[0040] To this, the present disclosure provides an internal friction measurement apparatus 100 as shown in FIG. 1. The internal friction measurement apparatus 100 includes a rigid machine base 102 onto which all the components of the internal friction measurement apparatus 100 are mounted and/or supported. The internal friction measurement apparatus 100 further includes side walls, a bottom wall having a pressure lock 104, and a top wall having an opening for sample holder 106 beneath a removable front cover 108.
[0041] The sample holder 106 is for holding a sample 110, say, steel strip as shown in FIG. 2, in such a way that one end of sample 110 is rigidly held and other end is allowed to oscillate freely. Further, as shown in FIG. 2, the sample 110 may be having two holes 202, 204 at the end which would be rigidly held in the sample holder 106. Although the sample is shown with 202 mm length, 22 mm width, 9 mm distance of the first hole 202 from the top, 25 mm gap distance between the holes 202 and 204, and 6 mm diameter of both the holes 202, 204, these dimensions are exemplary and should not be construed as a limitation to the scope of the present disclosure.
[0042] The one fixed end of sample 110 is held by the sample holder 106 inside a hollow cylindrical heater 112 for heating and the other free end of the sample 110 is positioned in a sample chamber. Further, a vacuum and an initial temperature of the sample chamber is controlled by putting a chilling circuit inside the sample chamber, as shown in FIG. 3.
[0043] In an aspect, a power supply to the hollow cylindrical heater 112 is controlled by a heater socket (electronic controller) 114 based on a temperature of a thermocouple 116, 116A which is placed over the sample 110 held in the sample holder 106. Further, the hollow cylindrical heater 112 includes glass wool 118 surrounding the sample 110 so as to maintain the temperature of the sample 110 during the measurement of the internal friction.
[0044] Further, the sample chamber, having the other free end of the sample 110, includes an electromagnetic actuator (solenoid actuator) 120 for striking the other free end of the sample 110 after each defined temperature interval. The sample chamber further a proximity distance sensor 122 positioned near the other free end of the sample 110 so as to measure a linear distance of the other end during oscillation.
[0045] The internal friction measurement apparatus 100 further includes a microcontroller (not shown in figures) to: receive measured distance data from the proximity distance sensor 122, transform the measured distance data in the form of sinusoidal function, and calculate damping in the amplitude of the sinusoidal function (FIG. 4) by:
logarithmic decrementing of the amplitude, d, which is defined as:

where Ai= Amplitude at ith cycle, and
Ai+n = amplitude at i+nth cycle; and
calculating average internal friction (IF) as:
.
[0046] Based on the average damping of the amplitude which is proportional to the damping energy, ‘loss angle’ values are plotted for different increasing temperatures to find out the Snoek peak as shown in FIG. 5.
[0047] From the obtained Snoek peak height, based on the free energy calculation of the sample 110 (steel strip), an amount of solute, such as Carbon (C) and Nitrogen (N) present in the sample 110 can be estimated.
[0048] FIG. 6 shows a method 600 for measurement of internal friction of a material, in accordance with an embodiment of the present disclosure. The order in which the method 600 is described is not intended to be construed as a limitation, and any number of the described method blocks may be combined in any order to implement the method 600, or an alternative method.
[0049] At block 602, the method 600 includes holding a sample 110 on a sample holder 106 in such a way that one end of the sample 110 is rigidly held and other end is allowed to oscillate freely.
[0050] At block 604, the method 600 includes heating the sample 110 with a hollow cylindrical heater 112 at defined temperature intervals.
[0051] At block 606, the method 600 includes, after each defined temperature interval, striking the other end, which is allowed to oscillate freely, with the electromagnetic actuator 120.
[0052] At block 608, the method 600 includes measuring a linear distance of the other end of the sample 100 by a proximity distance sensor 122.
[0053] At block 610, the method 600 includes transforming the measured distance data in the form of sinusoidal function (FIG. 4).
[0054] At block 612, the method 600 includes calculating the average internal friction of the sample 110 at an instantaneous temperature by:
(i) logarithmic decrementing of the amplitude, d, which is defined as:

where Ai= Amplitude at ith cycle, and
Ai+n = amplitude at i+nth cycle; and
(ii) calculating average internal friction (IF) as:
.
[0055] Further, in an aspect, ultimate tensile strength (UTS) of the ultra-high-strength steel is 1900-2300 MPa.
[0056] In an aspect, the method 600 further comprising plotting the internal friction data against the instantaneous temperature to build a Snoek peak, wherein Snoek peak is a characteristic measurement of the presence of solute elements in the sample 110. This Snoek peak is the characteristic measurement of the presence of solute elements in the metal. Based on thermodynamic free energy calculation the quantitative measurement of different solute elements is done. Using the amount of solute elements present on the sample, a further design of chemistry and process parameters of the product (different grade of BH and DP steels) is done for obtaining desired bake hardenability and shelf life and other critical mechanical properties.
[0057] In an aspect, the capturing of linear distance of the other end by the proximity distance sensor 122 is performed at the mega-hertz frequency.
[0058] In an aspect, the method 600 includes controlling power supply to the hollow cylindrical heater 112 by a heater socket 114 based on a temperature of a thermocouple 116, 116A which is placed over the sample 110 held in the sample holder 106.
[0059] In an aspect, the method 600 includes controlling a vacuum of a sample chamber and an initial temperature by putting a chilling circuit (FIG. 3) inside the sample chamber, wherein the sample 110 is partially held inside the sample chamber.
[0060] Thus, the present disclosure provides a unique and simple method for measuring solute elements in steel sample 110.
[0061] Furthermore, although the method and apparatus described herein are for measurement of the loss angle for the estimation of interstitial elements like Carbon and Nitrogen present in the steel solution, the same method and apparatus can be used for measuring internal friction of other materials for estimating different solute elements like Hydrogen, Boron, Oxygen, and the like, from their characterised Snoek peak at different temperature.
[0062] Similarly, although the method and apparatus described herein are for determination of Snoek peak height for estimation of the solutes in the development of bake hearable steel for improving its shelf life and bake hardenable properties for different grades of BH steels (of tensile strength from 160 MPa to 440 MPa), the same method and apparatus can be used for improving bake hardenable properties for DP (Duel Phase), TRIP and CP ( complex phase) steels of different strength level 390 MPa to 1200 MPa.
[0063] Further, the method and apparatus described herein allows the measurement of the temperature of the sample by placing the thermocouple placed near the sample for accurate and measurement of the sample without touching the sample. The same thermocouple can be used for the temperature controller of the heater.
[0064] Also, there is an option for measuring loss angle at sub-zero temperature by fitting an addition chiller unit in the apparatus described herein.
[0065] In the apparatus described herein, the range of temperate applicable for our loss angle measurement equipment is - 40 degrees Celsius to 600 degrees Celsius.
TECHNICAL ADVANTAGES
[0066] The present disclosure provides a low-cost internal friction measurement method and apparatus.
[0067] The present disclosure provides an easy to maintain internal friction measurement apparatus.
[0068] The present disclosure provides an easy to operate internal friction measurement apparatus.
[0069] The present disclosure provides an easy to sample preparation internal friction measurement method.
[0070] The present disclosure provides an internal friction measurement method and apparatus, the results of which are repeatable and accurate.
[0071] The present disclosure provides an internal friction measurement method and apparatus, which can be used for research purposes as well as for regular industrial production and quality control.
[0072] Furthermore, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.
[0073] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.
[0074] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

We claim:

1. A method for measurement of internal friction of a material, the method comprising:
holding a sample (110) on a sample holder (106) in such a way that one end of the sample (110) is rigidly held and other end is allowed to oscillate freely;
heating the sample (110) with a hollow cylindrical heater (112) at defined temperature intervals;
after each defined temperature interval, striking the other end, which is allowed to oscillate freely, with an electromagnetic actuator (120);
measuring a linear distance of the other end by a proximity distance sensor (122);
transforming the measured distance data in the form of sinusoidal function; and
calculating damping in the amplitude of the sinusoidal function due to average internal friction of the sample (110) for instantaneous temperature, for calculating the average internal friction of the sample (110) at that instantaneous temperature.

2. The method as claimed in claim 1, wherein calculating damping in the amplitude of the sinusoidal function, comprising
logarithmic decrementing of the amplitude, d, which is defined as:

where Ai= Amplitude at ith cycle, and
Ai+n = amplitude at i+nth cycle; and
calculating average internal friction (IF) of the sample (110) as:
.

3. The method as claimed in claim 1, further comprising plotting the internal friction data against the instantaneous temperature to build a Snoek peak, wherein Snoek peak is a characteristic measurement of the presence of solute elements in the material of the sample (110).

4. The method as claimed in claim 1, wherein capturing a linear distance of the other end by the proximity distance sensor (122) is performed at megahertz frequency.

5. The method as claimed in claim 1, wherein controlling power supply to the hollow cylindrical heater (112) by a heater socket (114) based on a temperature of a thermocouple (116, 116A) which is placed over the sample (110) held in the sample holder (106).

6. The method as claimed in claim 1, comprising controlling a vacuum of a sample chamber and an initial temperature by putting a chilling circuit inside the sample chamber, wherein the sample (110) is partially held inside the sample chamber.

7. An internal friction measurement apparatus (100) comprising:
a sample holder (106) for holding a sample (110) in such a way that one end of the sample is rigidly held and other end is allowed to oscillate freely;
a hollow cylindrical heater (112) for heating the sample (110) in a sample chamber at defined temperature intervals, wherein the sample (110) is held by the sample holder (106) inside the sample chamber;
an electromagnetic actuator (120) for striking the other end, which is allowed to oscillate freely, after each defined temperature interval;
a proximity distance sensor (122) positioned near the other end of the sample (11) so as to measure a linear distance of the other end during oscillation; and
a microcontroller to:
receive measured distance data from the proximity distance sensor (122),
transform the measured distance data in the form of sinusoidal function, and
calculate damping in the amplitude of the sinusoidal function due to average internal friction of the sample for instantaneous temperature, for calculating the average internal friction of the sample at that instantaneous temperature.

8. The internal friction measurement apparatus (100) as claimed in claim 7, wherein microcontroller is for:
logarithmic decrementing of the amplitude, d, which is defined as:

where Ai= Amplitude at ith cycle, and
Ai+n = amplitude at i+nth cycle; and
calculating average internal friction (IF) of the sample (110) as:
.

9. The internal friction measurement apparatus (100) as claimed in claim 7, comprising a heater socket (114) for controlling power supply to the hollow cylindrical heater (112) based on a temperature of a thermocouple (116, 116A) which is placed over the sample (110) held in the sample holder (106).
10. The internal friction measurement apparatus (100) as claimed in claim 1, wherein the hollow cylindrical heater (112) comprising glass wool (118) surrounding the sample (110) so as to maintain the ,