Project #47876 - materials and hardware engineering

Assessment Title and Tasks: Determination of the Hardness Numbers for a Range of Metallic Alloy & their Subsequent Correlation to Mechanical Strength

 

Assessment Task:

 

Materials & Hardware – NG2S402

 

Determination of the Hardness Numbers for a Range of Metallic Alloy & their Subsequent Correlation to Mechanical Strength

1. Introduction

Hardness testing can be used to identify the mechanical properties of engineering materials, and unlike tensile testing which requires specific dimensions on its test specimens, it relies on pushing a hard indenter with a known force into the surface of the materials in question [4, 5, 6]. As such it is a quicker test to perform on engineering materials/ products in a number of applications (such as quality check on the surface of a case-hardened specimen, or products having following a specific heat treatment procedure) and its results can be co-related to strength values (e.g. the UTS) of the tested materials. There are primarily 3 types of hardness tester namely the Brinell, Vickers and Rockwell, which the University of South Wales has in its Materials Laboratory in G118 which are calibrated annually to ensure their proper functioning according to their respective British Standards [1, 2, 3]. The hardness number for both the Brinell and Vickers tests can be derived by dividing the indentation force (in kgf) with the resulting surface area of their indents/ impression on the surface of the tested specimen. The Rockwell’s number however is identified by subtracting the depth of penetration from a known constant. Please note that the unit of the hardness number has NO direct correlation to strength. Hardness numbers can be use as a relative indication of material strength but does NOT replace tensile test results. Therefore:

 

(i)            The Aims of the laboratory session is to (a) establish the hardness number for a range of carbon steels using standard hardness tester in accordance to the relevant British Standard; (b) develop an understanding of the relationship between material’s strength with the said parameters.

(ii)          The Objectives are: (a) conduct hardness tests in accordance to the relevant British Standards on a range of materials namely low carbon steel, medium carbon steel, and high carbon steel; (b) gather the test results, produce the necessary hardness numbers and discuss the results; (c) produce a report on the assignment which should also include some application examples of the technique and also the tested materials in industry. An example outline of the report has been provided here.

 

2. Laboratory Set-Up & Method

 

        i)      You will be provided with 3 steel specimens of varying carbon content, namely: low carbon steel, medium carbon steel, and high carbon steel. Place the specimens one at a time on the test platform of the hardness tester and carry out the test procedure according to the relevant British Standard.

      ii)      Derive or read in the case of Rockwell Hardness tester, the Hardness value from the relevant table. You should carry out a number of tests on a specimen in order to obtain a representative average hardness reading. You will need to specific the type of hardness tester used, and also the condition of the test (type of indenter, load).

    iii)      Repeat with the remaining test specimens. You are expected to present the results from two test methods (e.g. Vickers and Rockwell).

    iv)      If in doubt please ask the lab technician or the academic supervising the session.

 

3. Test Results & Discussion

 

        i)      Tabulate the results, and arrange the information in ascending order – softest to strongest. Validate your findings against published data, and identify/ correlate where possible the strength values for the tested materials. You MUST reference your findings.

      ii)      Show that the Vicker’s hardness number can be calculated by dividing the applied indentation force by the surface area of the inverse pyramid crater.

    iii)      Compare the mechanical properties of the various materials, and in particular comment on the effect of increasing the carbon content in steel.

    iv)      Compare your empirical results with published data and comment on them. Identify the example applications which each type of steel specimen can used in.


4. Conclusions – Briefly summarise your findings.

 

5. References (http://lcss.glam.ac.uk/lrc/guides/citing/)

 

  1. BS EN ISO 6506-1:2005, Metallic materials. Brinell hardness test
  2. BS EN ISO 6507-1:2005, Metallic materials. Vickers hardness test. Test method 
  3. BS EN ISO 6508-1:2005, Metallic materials.  Rockwell hardness test. Test method (scales A, B, C, D, E, F, G, H, K, N, T)
  4. R.A. Higgins, 2006 “Materials for Engineers & Technicians”, 4th Edition, Elsevier – Chapter 3 on Mechanical Testing pgs 27 – 33.
  5. Callister, W.D., 2006, Materials Science & Engineering – An Introduction, 7th Edition, John Wiley & Sons.
  6. Askeland, D.R., 1996, The Science & Engineering of Materials, 3rd Edition, Chapman & Hall.  – Chapter 6 on Mechanical Testing & Properties, pgs 140 – 149. 

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Due By (Pacific Time) 11/20/2014 12:00 pm
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