EXPERIMENT NO.7 ROCKWELL HARDNESS TEST OBJECTIVE To determine the hardness of a material by Rockwell hardness test. DISCUSSION OF PRINCIPLES Rockwell hardness testing is a general method for measuring the bulk hardness of metallic and polymer materials. Although hardness testing does not give a direct measurement of any performance properties, hardness of a material correlates directly with its strength, wear resistance, and other properties. Hardness testing is widely used for material evaluation because of its simplicity and low cost relative to direct measurement of many properties. Specifically, conversion charts from Rockwell hardness to tensile strength are available for some structural alloys, including steel and aluminum. Rockwell hardness testing is an indentation testing method. The indenter is either a conical diamond (brale) or a hard steel ball. Different indenter ball diameters from 1/16 to 1/2 in. are used depending on the test scale. To start the test, the indenter is “set” into the sample at a prescribed minor load. A major load is then applied and held for a set time period. The force on the indenter is then decreased back to the minor load. The Rockwell hardness number is calculated from the depth of permanent deformation of the indenter into the sample, i.e. the difference in indenter position before and after application of the major load. The minor and major loads can be applied using dead weights or springs. The indenter position is measured using an analog dial indicator or an electronic device with digital readout. The various indenter types combined with a range of test loads form a matrix of Rockwell hardness scales that are applicable to a wide variety of materials. Each Rockwell hardness scale is identified by a letter designation indicative of the indenter type and the major and minor loads used for the test. The Rockwell hardness number is expressed as a combination of the measured numerical hardness value and the scale letter preceded by the letters, HR. For example, a hardness value of 80 on the Rockwell A scale is reported as 80 HRA. 1 Student Number Name is also shown in the numbered images below (figure 1). the meter is set to zero. thus. the meter only shows 2 Student Number Name . the penetrator remains in the imprint and all elastic deformations. 3. When the indicator of the meter finally stops moving. which is connected to the penetrator and displays the penetrators shifts on a larger scale. is also included in the figure. 2. This position needs to be kept to reach the final penetration (when testing hard materials the penetration is almost immediate. which is described below. The tested surface is exposed to the penetrator and the first test load Fo (preload) is applied. are eliminated. with soft materials it is necessary to wait for a number of seconds). At this point. Slowly and without shocks the load F1 is applied additionally. the additional load F1 is removed until the preload is applied respectively. This way. The penetration procedure can also be observed on the indicator of the meter. depending on the hardness of the material. With this load the penetrator enters the material more or less deep. The meter. 1. the sequence of the Rockwell method.PROCEDURES For a better understanding. Together with the preload this is defined as total test load F. which were caused by the application of the total test load. A small indentation appears. the remaining penetration depth (as difference between preload and total test load). test loads. and the units are standardised in the Rockwell method and can be divided into two groups: standard Rockwell (method N) and superficial Rockwell (method T). SET-UP OF APPARATUS 3 Student Number Name . preloads. The penetrator. 4 Student Number Name . Engineering Materials and Testing Laboratory Experiment No.83 60. 2015 Section: B3 Group No. Galera Instructor 5 Student Number Name .98 92.70 Mild Steel Ball 70.17 70.5 30.33 94.: 7 ROCKWELL HARDNESS TEST Final Data Sheet Name: Date: June 9.33 High Carbon Diamond 96.50 98.50 Stainless Steel Diamond 34.77 96.25 69.83 Brass Ball 62.53 33.0 76.17 29.: 2 MATERIAL HARDNESS INDENTER GROUP 1 GROUP 2 GROUP 3 GROUP 4 Aluminum Ball 92.83 70.27 107.50 97. Rodriguez ME-UTM Engineer Approved by: Engr.18 74.83 Assisted by: Vergel S. F. 6 Student Number Name . Define Rockwell Hardness number. engineering lettering) 1. 2. Explain the importance of Rockwell Hardness to obtain an approximation of tensile strength. What are the main features of Rockwell Hardness Test? 3.QUESTIONS (use another sheet of paper. 5.4. Under what conditions are most useful in Rockwell Hardness? 7 Student Number Name . Differentiate the Brinell Hardness and Rockwell Hardness tests. engineering lettering) 8 Student Number Name .DISCUSSION (use another sheet of paper. engineering lettering) 9 Student Number Name .CONCLUSION (use another sheet of paper. engineering lettering) 10 Student Number Name .RECOMMENDATION (use another sheet of paper. engineering lettering) 11 Student Number Name .REFERENCES (use another sheet of paper.