Drum Handling
 Drying Time/Gelation
 Film Flaws
 Film Thickness
 Impact & Flexibility
 Lab Apparatus
 Measuring Instruments
 Optical Instruments
 pH & Conductivity
 Surface Profile
 Surface Tension
Home  >>  Products  >>  Impact/Flexibility  >>  Pentagon Mandrel

Pentagon Mandrel Bend Test

ASTM Method D 522-88, Elongation of Attached Organic Coatings with Cylindrical Mandrel Apparatus. FTMS No. 141, Method 6221, Flexibility. FTMS, Method 6223, “Cold Cracking.”


The Pentagon Mandrel Bend Test Apparatus is made for the evaluation of coating systems. The properties of coating systems measured by the Mandrel Bend Test are rapidly increasing in importance due to the gain in popularity of coil coating where the coated base material is subjected to a forming operation. Most any base material that will later be subjected to a forming operation can be accommodated.

Pentagon Mandrel Bend Test



There are two side plates, each of pentagon shape. Each of the five sides are 6.5 inches long, resulting in a 10.0 inch high assembly. One of the side plates is 1/8 inch thick and has one of the sides rounded to form a high-strength mandrel of this thickness. The other side plate is identical except it has a thickness of 1/4 inch and provides the 1/4 inch mandrel. The side plates are separated by five bars, each secured near the points of the side plates at center to center distance of 5.5 inches. The bars are each 5.5 inches long and have diameters of 3/8, 1/2, 5/8, 3/4 and 1 inch.

  • The Pentagon Mandrel Bend Test Apparatus is constructed of black anodized aluminum.
  • The Pentagon design provides a completely self-contained unit with no loose parts.
  • Paramount importance in the design is the plate backing of the 1/8 and 1/4 inch mandrels which eliminate errors of mandrel flexing.
  • The Pentagon Mandrel Apparatus is ruggedly and attractively constructed. It will accommodate essentially all standard test panels.
  • Mandrel size is etched in the thicker side panel after anodizing for permanence and ease of identification.

Instructions for Use

  1. The preparation of the test specimens must be made with considerable care if good comparative and reproducible results are to be obtained. Improper base cleaning, resulting in poor adhesion, will normally result in a lower tolerated elongation. Coating thickness and uniformity is of paramount importance, not only due to the usual relationship of thickness with most physical characteristics but also due to the direct effect in the mandrel bend test. The test panels should be prepared in a manner and with a coating thickness as near as possible to that which will be encountered by the base - coating system process. Compensate for the direct effect of coating thickness in the Pentagon Mandrel Bend Test by adding the appropriate correction factor for each mil of coating thickness to the base.
  2. Place the test panel with the uncoated side over, and in contact with, the selected mandrel with a minimum of two inches overhang and insure that there is clearance for the other end of the panel to pass the adjacent mandrel.
  3. Using a steady pressure of the fingers, bend the panel approximately 180 degrees around the mandrel in about one second. Remove the panel and examine immediately for cracking of the coating visible to the unaided eye.
  4. If cracking has not occurred, repeat the procedure using successively smaller diameter mandrels until cracking of the coating occurs or until the smallest diameter mandrel has been used. Record the smallest mandrel accommodated by the base-coating system or the total elongation determined.



Pentagon Mandrel Bend Test Theory

It is obvious from the following sketch that Base Length “LC” is greater than Base Length “L”, which is in contact with the Mandrel, and that this difference is a function of the Base Thickness.

It is also obvious that the Coating Length “C” is longer than its length at the interface with the base at “LC” and this difference is proportional to the Coating Thickness.

The theoretical determination of the relative length change of the two surfaces of the base as it is bent around the mandrel is a complex matter. The compression of the surface in contact with the mandrel usually is not as great as the expansion of the opposite surface. Neither is this compression - expansion ratio constant from material to material or with different thicknesses of the same material. The relationship between coating elongation at the interface with the base as a function of mandrel diameter is shown in the graph which has been prepared from data contained in ASTM Method D 522-88.

This graph is representative of a thin coating, one mil or less in thickness, applied to Cold Rolled Steel, SAE No. 1010, dead soft, finish “A” with a thickness of 1/32 inch.

Within limits and with most Base Coating systems, the percent elongation at the interface is proportional to the thickness of the base and can be calculated with a fair degree of accuracy with data from the graph for base thickness other than 1/32 inch.

Pentagon Mandrel Bend Test Charts



Prices subject to change    Prices listed in US dollars for domestic shipments within US, Canada, & Mexico only    Export orders require quotations - click here for a quote     For more info call us 1-800-762-2478 or 954-946-9454.
Item Number Item Prices
MN-GMU Pentagon Mandrel Bend Test Apparatus $436.00


  By Category Email Registry How to Order Contact Info
  By Industry Trade Shows Request Quote History
  New Products Test Lab Info Order Form FAQ's
  Sales/Trade-In Offers Articles/Links Repairs/Service Policies

  © 2020 Paul N. Gardner, a BYK Instruments Company | Contact | Policies Facebook  YouTube  Blogger