The Brinell Hardness Test measures the resistance of metals to indentation under specific conditions. BACKGROUND Hardness...

       

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The Brinell Hardness Test measures the resistance of metals to indentation under specific conditions. BACKGROUND Hardness has different arbitrary definitions which form the basis for various hardness tests now in use. These definitions are generally developed with the necessity for requirements under different conditions of service. The definition of indentation hardness according to Brinell is "The resistance to permanent indentation under static or dynamic loads." The static indentation test was first introduced by J.A., Brinell in 1900, and makes use of a steel ball as the indenter. This is pressed smoothly into a well-prepared flat surface of the test metal under a known load, which is maintained for a period of 15 seconds, and then removed. The diameter of the resulting indentation is measured by means of a microscope and hardness is expressed as the load in kilograms divided by the curved area of the indentation in mm². In accordance with the ASTM specifications (ASTM E 10), shown in the following table. Material Hardened Steel, Cast Iron Mild Steel Non-Ferrous Ball Diameter Load Brinell Hardness (HB) Range 160 to 600 48 to 300 16 to 100 [mm] 10 10 10 [kgf] 3000 1500 500 This test should not be used to test extremely hard materials because the ball itself deforms too much. A tungsten carbide indenter can be used for very hard materials. It is not recommended for materials having a HB over 627. Also, it is not adopted for testing case hardened surfaces. because the depth of the indentation may be greater than the thickness of the case and because the yielding of the soft core invalidates the results. Do not use a steel ball on steels having a hardness over 444 HB or with a hardness over 627 HB. It is desirable that the test load be such magnitude that the diameter of the impression be in the range of 2.50 to 6.00 mm. A lower limit in impression diameter is necessary because of the reduction in sensitivity of the test with reduction in impression size. The upper limit is influenced by limitations of travel of the indenter. The minimum thickness requirements for Brinell hardness tests is shown in the following table THEORY Minimum Thickness of Specimen [mm] where P A To calculate Brinell Hardness Number (HB) use the equation: where D t 1.6 3.2 4.8 6.4 8.0 9.6 Minimum Hardness for which the Brinell Test May Safely be Made 1500 kgf where d = Diameter of Indenter [mm] = Depth of Indentation [mm] The depth of indentation (t) is determined by: 3000 kgf 602 301 201 150 120 100 HB = = Applied Load [kg] or Applied Load [N]/9.81 m/s² = Area of the Indentation [mm²] The area of indentation (A) can be determined using the following equation: t= P A A = π-D-t 301 150 100 D-√D²-d² 2 75 60 50 500 kgf 100 50 33 25 20 17 = Mean Diameter of Impression (Horizontal and Vertical Direction) [mm] (2) (3) The hardness number is followed by the letter HB. The number should be written in a more descriptive way as in the following example: which means a Brinell hardness of 85 is measured with a ball of 10 mm diameter and a load of 5 x 10³ N applied for 20 seconds. EQUIPMENT/MATERIAL ● Compression machine ● ● ● Hardness = 85HB 10/5/20 10 mm steel ball indenter Microscope Steel and aluminum flat discs with finished surfaces PROCEDURE 1. Place the sample on the lower adapter as shown in Figure 1, and make contact between the loading ball and the sample. Make sure that the contact point is not too near to the edge of the specimen, to avoid getting an unsymmetrical indentation. 2. Apply the test load "P" for 15 seconds. (P = 10 x 10³ N for steel or P = 5 x 10³ N for aluminum) 3. After removing the load, measure the impression diameter to the nearest 0.1 mm using the microscope as in Figure 4. The diameter is the average of two diameters at right angles to each other. Note: If the two diameters differ by more than 0.1 mm, discard the readings and make a new indentation. 4. Repeat the previous procedure at least two more times with the same load. The distance between the center of the indentation and another indentation or the edge of the sample should be at least two- and one-half times the diameter of the indentation as in Figure 3. RESULTS 1. For each material and trial, calculate and tabulate the following: Mean Diameter of Impression Depth of Indentation Area of Indentation Brinell Hardness ● ● ● 2. What is the average Brinell Hardness for steel and aluminum? DISCUSSION 1. Compare your average Brinell Hardness with published values and comment. Use published values which can be easily found online of 6061 aluminum and mild steel for comparison purposes. 2. Comment on the practical applicability of the hardness test in engineering and list some examples. 3. Describe other hardness tests for metals that are currently used in engineering. 4. Discuss the effects of the following experimental errors on the Brinell hardness number a) indentations were made too close to the edge of the specimen. b) indentations were made too close to each other. 5. Discuss other sources of error in this experiment. EXPERIMENT 1 BRINELL HARDNESS TEST Metal Steel Aluminum Trial 1 2 3 1 2 3 Steel Ball Diameter [mm] 10 DATA SHEET 10 Load [N] 10047 10013 10084 5072 5078 5080 Impression Diameter (x-direction) [mm] 4.1 4.0 4.0 3.5 3.6 3.6 Impression Diameter (y-direction) [mm] 4.2 3.9 4.0 3.6 3.6 3.7 The Brinell Hardness Test measures the resistance of metals to indentation under specific conditions. BACKGROUND Hardness has different arbitrary definitions which form the basis for various hardness tests now in use. These definitions are generally developed with the necessity for requirements under different conditions of service. The definition of indentation hardness according to Brinell is "The resistance to permanent indentation under static or dynamic loads." The static indentation test was first introduced by J.A., Brinell in 1900, and makes use of a steel ball as the indenter. This is pressed smoothly into a well-prepared flat surface of the test metal under a known load, which is maintained for a period of 15 seconds, and then removed. The diameter of the resulting indentation is measured by means of a microscope and hardness is expressed as the load in kilograms divided by the curved area of the indentation in mm². In accordance with the ASTM specifications (ASTM E 10), shown in the following table. Material Hardened Steel, Cast Iron Mild Steel Non-Ferrous Ball Diameter Load Brinell Hardness (HB) Range 160 to 600 48 to 300 16 to 100 [mm] 10 10 10 [kgf] 3000 1500 500 This test should not be used to test extremely hard materials because the ball itself deforms too much. A tungsten carbide indenter can be used for very hard materials. It is not recommended for materials having a HB over 627. Also, it is not adopted for testing case hardened surfaces. because the depth of the indentation may be greater than the thickness of the case and because the yielding of the soft core invalidates the results. Do not use a steel ball on steels having a hardness over 444 HB or with a hardness over 627 HB. It is desirable that the test load be such magnitude that the diameter of the impression be in the range of 2.50 to 6.00 mm. A lower limit in impression diameter is necessary because of the reduction in sensitivity of the test with reduction in impression size. The upper limit is influenced by limitations of travel of the indenter. The minimum thickness requirements for Brinell hardness tests is shown in the following table THEORY Minimum Thickness of Specimen [mm] where P A To calculate Brinell Hardness Number (HB) use the equation: where D t 1.6 3.2 4.8 6.4 8.0 9.6 Minimum Hardness for which the Brinell Test May Safely be Made 1500 kgf where d = Diameter of Indenter [mm] = Depth of Indentation [mm] The depth of indentation (t) is determined by: 3000 kgf 602 301 201 150 120 100 HB = = Applied Load [kg] or Applied Load [N]/9.81 m/s² = Area of the Indentation [mm²] The area of indentation (A) can be determined using the following equation: t= P A A = π-D-t 301 150 100 D-√D²-d² 2 75 60 50 500 kgf 100 50 33 25 20 17 = Mean Diameter of Impression (Horizontal and Vertical Direction) [mm] (2) (3) The hardness number is followed by the letter HB. The number should be written in a more descriptive way as in the following example: which means a Brinell hardness of 85 is measured with a ball of 10 mm diameter and a load of 5 x 10³ N applied for 20 seconds. EQUIPMENT/MATERIAL ● Compression machine ● ● ● Hardness = 85HB 10/5/20 10 mm steel ball indenter Microscope Steel and aluminum flat discs with finished surfaces PROCEDURE 1. Place the sample on the lower adapter as shown in Figure 1, and make contact between the loading ball and the sample. Make sure that the contact point is not too near to the edge of the specimen, to avoid getting an unsymmetrical indentation. 2. Apply the test load "P" for 15 seconds. (P = 10 x 10³ N for steel or P = 5 x 10³ N for aluminum) 3. After removing the load, measure the impression diameter to the nearest 0.1 mm using the microscope as in Figure 4. The diameter is the average of two diameters at right angles to each other. Note: If the two diameters differ by more than 0.1 mm, discard the readings and make a new indentation. 4. Repeat the previous procedure at least two more times with the same load. The distance between the center of the indentation and another indentation or the edge of the sample should be at least two- and one-half times the diameter of the indentation as in Figure 3. RESULTS 1. For each material and trial, calculate and tabulate the following: Mean Diameter of Impression Depth of Indentation Area of Indentation Brinell Hardness ● ● ● 2. What is the average Brinell Hardness for steel and aluminum? DISCUSSION 1. Compare your average Brinell Hardness with published values and comment. Use published values which can be easily found online of 6061 aluminum and mild steel for comparison purposes. 2. Comment on the practical applicability of the hardness test in engineering and list some examples. 3. Describe other hardness tests for metals that are currently used in engineering. 4. Discuss the effects of the following experimental errors on the Brinell hardness number a) indentations were made too close to the edge of the specimen. b) indentations were made too close to each other. 5. Discuss other sources of error in this experiment. EXPERIMENT 1 BRINELL HARDNESS TEST Metal Steel Aluminum Trial 1 2 3 1 2 3 Steel Ball Diameter [mm] 10 DATA SHEET 10 Load [N] 10047 10013 10084 5072 5078 5080 Impression Diameter (x-direction) [mm] 4.1 4.0 4.0 3.5 3.6 3.6 Impression Diameter (y-direction) [mm] 4.2 3.9 4.0 3.6 3.6 3.7

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ANSWER 1 RESULTS Metal Trial Steel Ball Diameter mm Load IN Impression Diameter xdirection mm Impression Diameter ydirection mm 1 37 10138 37 Steel 2 10 10118 36 37 3 10054 36 38 1 5253 38 38 Aluminum ... View the full answer