Patent Application
20250187292
The present disclosure relates to a method and apparatus for burnishing or compressing a replica tape to represent an original surface of a material. More particularly, the present disclosure relates to a method and apparatus for burnishing such a replica tape by using a consistent pressure.
In the field of Non-Destructive Testing surface analysis, known techniques include visual inspection, liquid penetrant, and magnetic particle inspection. In addition, microscopy techniques, such as confocal, interferometric, and scanning electron microscopy (SEM), and mechanical surface profile instruments, such as one- and two-dimensioned stylus-based instruments, are known techniques to determine a surface profile. Within the class of visual inspection techniques, surface replication may be used to aid in the remote inspection of materials. Known surface replication techniques involve the transfer of a surface profile to a media such as a replica tape for indirect examination using microscopy. Known replica tape uses a cellulose acetate film to transfer surface profiling for imaging microstructures with standard microscopy techniques. However, this technique is not used for surface profiling but rather typically as a means to ascertain image crack formation or creep damage of components.
Other known methods of surface transfer to a replicating media include replication putty, shape memory polymer, as well as casting techniques using two-part silicon rubbers and methacrylate. The resulting replica is analyzed using a number of techniques including interferometric, scanning electron microscopy (SEM), and confocal microscopy. One- or two-dimensional mechanical surface profile instruments can also be used on the replica media, such as a drag stylus or needle-type surface profile gages.
It is known to use replica tape to characterize a surface. Method C of ASTM D4417 describes the process for measuring the peak-to-valley distance of a surface, such as abrasive blasted surfaces on metal bridges and ships, for example. The character of the blasted surface is predictive of paint adherence. If the peak-to-valley distance is too small, the surface lacks sufficient “tooth” to anchor the paint. If the peak-to-valley distance is too large, the high peaks may protrude through the paint to become foci for corrosion.
PRESS-O-FILM®, which is an example of a commercially available replica tape, includes a non-compressible 50 μm (2 mil) polyester backing and a compressible layer of foam. The backing is attached to an adhesive backed paper carrier. The carrier has an approximately 8 mm diameter opening exposing the polyester and foam below. The adhesive backed paper carrier is adhered to the surface being characterized. A burnishing tool is used to “burnish” or compress the replica tape by applying force through the polyester backing to the compressible layer of foam, such that the peaks of the surface profile fully compress the foam, while the valleys of the surface profile partially compress the foam. As the peaks of the surface profile fully compress the foam, they become visible through the polyester backing. Once the peaks are visible consistently across the opening in the adhesive backed paper carrier, the burnishing process is complete.
The conventionally used burnishing tool consists of an acrylic rod with a ˜¼″ diameter spherical tip. The ˜¼″ diameter spherical tip is sized such that, ideally, the pressure applied by a human hand to the acrylic rod imparts sufficient force between the spherical tip and the polyester backing to fully compress the compressible layer of foam, but not so much force that the polyester backing is damaged.
An alternative burnishing tool is specified by the manufacturer, consisting of the ˜¼″ diameter spherical corner of the plastic container used to ship the replica tape prior to use.
After burnishing, the thickness of the replica tape is then measured with a spring-loaded micrometer, and the thickness of the polyester backing is subtracted to indicate the peak-to-valley distance of the original surface. Replica tape provides a permanent record of the surface. Some micrometers can also store the thickness reading of the replica tape to provide a permanent record of the peak-to-valley measurement.
Internal research and practical experience indicate that compressed foam thickness, and therefore the resulting measurement of peak-to-valley distance of the original surface, can be influenced by the pressure applied by the operator on the burnishing tool. It is theorized that there are two primary mechanisms that can lead to error.
The first potential source of error occurs when insufficient burnishing force is used. A characteristic of the compressible layer of foam is that it becomes transparent as it compresses. The operator is instructed to stop the burnishing process when the peaks of the surface profile become visible through the polyester backing, indicating that the foam is fully compressed at the peaks of the surface profile. However, it can be difficult for operators to discern between a replica that is fully compressed and a replica that is mostly, but not completely, compressed. This phenomenon typically manifests when measuring surface profiles with a small peak-to-valley distance that requires a greater degree of compression of the foam. If the foam is not fully compressed, the height of the replica foam as measured by the micrometer will be greater than the actual surface profile, generating error.
The second potential source of error occurs when excessive burnishing force is used. To accurately replicate the surface, the peaks of the surface profile should rest against the polyester backing after burnishing. However, if excessive burnishing force is used, the peaks of the surface profile can penetrate the polyester backing. This phenomenon typically manifests when measuring surface profiles with a large peak-to-valley distances and fewer peaks. When this occurs, the foam no longer replicates the entire peak-to-valley profile; instead, only the part of the profile that does not penetrate the polyester backing is measured. This can yield measurement results that are erroneously low.
Both of these sources of error can be mitigated by using a specific and consistent amount of force to burnish the replica tape. A ‘training tool’ is available with a known peak-to-valley distance, which operators can use to practice their burnishing technique to until they reliably achieve replica tape measurements that match the known peak-to-valley height of the standard. With experience, some operators are capable of minimizing this error.
However, the need for extensive experience and practice to obtain accurate results limits the potential users of the technique. Even more experienced users can find it challenging to consistently use the correct amount of force, increasing the errors associated with the test.
Exemplary embodiments of the present disclosure provide an apparatus and method to burnish replica tape by using a burnishing tool that imparts a consistent pressure on the foam under normal usage.
An exemplary embodiment of the present disclosure provides an apparatus for applying consistent pressure on a flat surface. The apparatus comprises a housing, which comprises an exterior portion and an interior hollow portion, a contact member contained within the interior hollow portion, and a spring arranged in the interior hollow portion and configured so as to apply a biasing force on the contact member so that a portion of the contact member protrudes from the interior hollow portion. The exterior portion comprises a flat portion having an opening therein, such that the contact member protrudes from the interior hollow portion through the opening. The opening comprises a first area and the flat portion comprises a second area, wherein a ratio of the second area over the first area is at least one or two.
According to an exemplary embodiment of the apparatus, the contact member is spherical.
According to an exemplary embodiment of the apparatus, a lip is formed at the portion of the flat portion adjacent the interior hollow portion so as to retain the spherical contact member within the interior hollow portion.
According to an exemplary embodiment of the apparatus, a member is provided between the spring and the spherical contact member to transmit force from the spring to the contact member.
According to an exemplary embodiment of the apparatus, the spring is configured to apply a force of about 450 grams on the contact member.
According to an exemplary embodiment of the apparatus, wherein the ratio of the second area over the first area is at least four.
An exemplary embodiment of the present disclosure provides a method of burnishing a replica tape with consistent pressure with an apparatus having a flat surface with an opening in it, and a spring-loaded contact member protrudes from the opening. The method comprises applying the flat portion of the apparatus on the replica tape and moving the apparatus over the replica tape so that the spring-loaded contact member applies a substantially consistent pressure on the replica tape.
Another exemplary embodiment of the present disclosure provides an apparatus for applying consistent pressure on a flat surface. The apparatus comprises a first elongated portion having a first end and a second, rounded end; a holder; and a flexible cylinder. A first end of the flexible cylinder is attached to the holder and the first end of the first elongated portion is connected to a second end of the flexible cylinder.
According to an exemplary embodiment of the apparatus, the flexible cylinder is a coiled spring.
According to an exemplary embodiment of the method, the method comprises applying the rounded end of the apparatus on the replica tape and applying pressure on the replica tape with the rounded end while holding the holder.
An exemplary embodiment of the present disclosure provides a tool for applying consistent pressure on a flat surface. The tool comprises a long arm having a torsion spring mounted at one end thereof, a short arm having a first end that is rounded and capable of burnishing a replica tape, and a second end of the short arm that includes a protrusion that is configured to engage with the torsion spring such that that the short arm can pivot with respect to the long arm.
Additional refinements, advantages and features of the present disclosure are described in more detail below with reference to exemplary embodiments illustrated in the drawings, in which:
In the drawings, identical or similarly functioning parts are denoted with the same reference symbols, unless otherwise noted. It is to be noted that components illustrated in the drawings are not always shown to scale.
Exemplary embodiments of the present disclosure solve the drawbacks noted above by providing an apparatus which applies consistent pressure when used to burnish a replica tape, as well as a method for burnishing a replica tape with consistent pressure. Exemplary embodiments of the present disclosure provide an apparatus and method which can be used to burnish a replica tape with consistent pressure by using force-limiting means to regulate the pressure applied to the replica tape, mitigating the sources of error that occur when insufficient or excessive burnishing force is applied to a burnishing tool by an operator.
In the following description of exemplary embodiments of the present disclosure, an apparatus and method for burnishing a replica tape with consistent pressure are described. Hereinafter, the term “replica tape” means a medium or film that may be embossed, compressed or cast on a surface of a material in order to replicate that surface. Any medium or film that has a characteristic intensity versus thickness function can be utilized with the features of the present disclosure as described herein and is intended to be encompassed within the definition of a “replica tape” as used herein. For example, a cast methacrylate replica embedded with a pigment can be used. A commonly known example of replica tape includes a polyester backing and a compressible foam surface. This is an example of a replica tape which may be utilized in the present disclosure, and the present disclosure is not limited thereto. For example, a replica tape may be composed of a backing that is made of a material other than polyester (e.g., nylon), and the compressible surface may be constituted by a material other than foam, where such material may be rigid. Alternatively, the replica tape may have only a compressible surface without any backing. For the sake of brevity, the term “replica tape” hereinafter refers to a replica tape which may be embossed, compressed or cast on a surface of a material to replicate that surface, unless otherwise noted.
In accordance with the exemplary embodiment, a contact member 2 is contained within the interior hollow portion 12. In
In accordance with the exemplary embodiment, a spring 3 is arranged in the interior hollow portion 12 and is configured so as to apply a biasing force on the contact member 2 so that a portion of the contact member 2 protrudes from the interior hollow portion 12. In the example of
In accordance with an exemplary embodiment, the spring 3 is configured to apply a force of about 450 grams on the contact member 2. The force which the spring 3 is configured to apply is related to and varies with the diameter of the contact member 2 and the nature of the replica tape. For a contact member 2 with a preferred diameter of about 0.3 in., the spring 3 may be configured to apply a force preferably between 400-500 grams, 425-475 grams, or about 450 grams. The spring 3 may be configured to apply the appropriate force which corresponds to any of the preferable diameters of the contact member 2.
In accordance with the exemplary embodiment, a member 4 is provided between the spring 3 and the contact member 2 to transmit force from the spring 3 to the contact member 2. In
In accordance with the exemplary embodiment, the contact member 2 is free to rotate. However, the contact member 2 may be glued or fixed to the member 4 to prevent rotation. Preventing rotation prevents the gummy, removable adhesive from the edges of the replica tape from migrating into the interior of the burnishing tool, binding it up, and reducing the precision of the force being applied. Second, fixing the contact member 2 may give the user a slightly better feel for when they are at the edge of the hole in the replica tape, and shouldn't burnish any further. The rotating member may roll right over the edge of the hole in the replica tape and away from the area that needed burnishing, without giving the operator much feedback.
In accordance with an exemplary embodiment, the exterior portion 11 comprises a flat portion 13 having an opening 14 therein, such that the contact member 2 protrudes from the interior hollow portion 12 through the opening 14. In
In the example of
In accordance with an exemplary embodiment, the opening 14 comprises a first area. The flat portion 13, minus the first area, comprises a second area. A ratio of the second area over the first area helps to define the relative distribution of the contact between the flat area and the contact member 2. The ratio of the second area over the first area is preferably at least one, at least two, at least three, at least four, or at least five.
However, the actual contact of the contact member 2 with the replica tape is difficult to calculate because of the roundness of the contact member and the compressibility of the replica tape. For success, the flat portion 13 should have a greater contact area than the area of the contact member 2 which contacts the flat surface, which, being a spherical surface, is quite small.
Accordingly, a more important ratio is the ratio of the second area over the area of contact portion of the contact member 2, which should be at least 1.0 or greater, such as 1.5, 2.0, 2.5, 3.0. 3.5 or greater. It is important that there is adequate surface area of the flat portion 13 to contact the flat surface which the apparatus 100 is applying a consistent pressure onto. The flat portion 13 may be composed of a material which makes it easy to contact and move over the flat surface which the apparatus 100 is applying a consistent pressure onto.
In accordance with an exemplary embodiment, a lip 15 is formed at the portion of the flat portion 13 adjacent the interior hollow portion 12 so as to retain the spherical contact member 2 within the interior hollow portion 12. In
The first rounded end 108 has a rounded portion having a diameter in the range of about 0.2 to 1.0 inches, or 0.3 to 0.9 inches, or 0.4 to 0.8 inches, or 0.5 to 0.7 inches.
Other embodiments of the present invention may include a structure such that the holder of the contact member is sufficiently spaced from the contact member such that the holder does not contact the replica tape during burnishing. If the flat portion is sufficiently distant from the contact member such that it always contacts the flat surface at a location away from the replica tape, the area ratio does not matter. Consider an embodiment where the opening comprising a first area is several inches in diameter, with the contact member suspended inside, such that the replica tape always remains inside that first area (and therefore never contacts the second/flat area) during burnishing. The flat portion/second area could be as small as a point, since it would be sitting on the blasted metal, and the force applied by that second surface wouldn't affect the measurement. One could imagine some sort of ‘tripod’-style device, where the contact member is suspended in the middle, such that the contact member is the only part of the apparatus making any contact with the replica tape. The ‘feet’ of the tripod would rest away from the replica tape on the blasted surface (if the contact member was configured to allow some lateral movement versus the ‘tripod’), or those feet could be configured to slide on the blasted surface, such that the contact member moves laterally in concert with the entire tripod.
Yet another embodiment of the invention is illustrated in
One of ordinary skill in the art would be able to determine an appropriate stiffness of the torsion spring appropriate for burnishing a replica tape. For example, the arms and torsion spring of this embodiment are configured to apply a force of between 200-1000 gf, 200-900 gf, 300-800 gf, 400-700 gf, 500-600 gf, or about 450 gf on the burnishing tape.
The disclosed preferred embodiments are representative of the invention, and the claims are not limited to the preferred disclosed embodiments.
The present application claims the benefit of U.S. Provisional Application No. 63/596,489, filed on Nov. 6, 2023. The entire contents of U.S. Provisional Application No. 63/596,489 is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63596489 | Nov 2023 | US |
