Charpy impact test 1

Charpy impact testThe Charpy impact test, also known as the Charpy v-notch test, is a standardized high strain-rate test whichdetermines the amount of energy absorbed by a material during fracture. This absorbed energy is a measure of agiven material's toughness and acts as a tool to study temperature-dependent ductile-brittle transition. It is widelyapplied in industry, since it is easy to prepare and conduct and results can be obtained quickly and cheaply. A majordisadvantage is that all results are only comparative.[1]

The test was developed in 1905 by French scientist Georges Charpy. It was pivotal in understanding the fractureproblems of ships during WWII. Today it is used in many industries for testing materials used in the construction ofpressure vessels and bridges and to determine how storms will affect materials used in them.[2]

Definition

A vintage impact test machine.

The apparatus consists of a pendulum axe swinging at a notchedsample of material. The energy transferred to the material can beinferred by comparing the difference in the height of the hammerbefore and after a big fracture.

The notch in the sample affects the results of the impact test,[3]

thus it is necessary for the notch to be of regular dimensions andgeometry. The size of the sample can also affect results, since thedimensions determine whether or not the material is in planestrain. This difference can greatly affect conclusions made.[4]

The "Standard methods for Notched Bar Impact Testing ofMetallic Materials" can be found in ASTM E23[5], ISO 148-1[6] orEN 10045-1[7], where all the aspects of the test and equipmentused are described in detail.

Quantitative results

The quantitative result of the impact tests the energy needed tofracture a material and can be used to measure the toughness of the

material and the yield strength. Also, the strain rate may be studied and analyzed for its effect on fracture.

The ductile-brittle transition temperature (DBTT) may be derived from the temperature where the energy needed tofracture the material drastically changes. However, in practice there is no sharp transition and it is difficult to obtaina precise transition temperature. An exact DBTT may be empirically derived in many ways: a specific absorbedenergy, change in aspect of fracture (such as 50% of the area is cleavage), etc.[1]

Charpy impact test 2

Qualitative resultsThe qualitative results of the impact test can be used to determine the ductility of a material.[8] If the material breakson a flat plane, the fracture was brittle, and if the material breaks with jagged edges or shear lips, then the fracturewas ductile. Usually a material does not break in just one way or the other, and thus comparing the jagged to flatsurface areas of the fracture will give an estimate of the percentage of ductile and brittle fracture.[1]

Sample sizesAccording to ASTM A370,[9] the standard specimen size for Charpy impact testing is 10mm×10mm×55mm. Subsizespecimen sizes are: 10mm×7.5mm×55mm, 10mm×6.7mm×55mm, 10mm×5mm×55mm, 10mm×3.3mm×55mm,10mm×2.5mm×55mm. Details of specimens as per ASTM A370 (Standard Test Method and Definitions forMechanical Testing of Steel Products).According to EN 10045-1,[7] standard specimen sizes are 10mmx10mmx55mm. Subsize specimens are:10mmx7.5mmx55mm and 10mmx5mmx55mm.According to ISO 148,[6] standard specimen sizes are 10mmx10mmx55mm. Subsize specimens are:10mmx7.5mmx55mm, 10mmx5mmx55mm and 10mmx2.5mmx55mm.

Notes[1] Meyers Marc A, Chawla Krishan Kumar (1998). Mechanical Behaviors of Materials. Prentice Hall. ISBN 978-0-13-262817-4.[2] Jacobs James A, Kilduff Thomas F (2005). Engineering Materials Technology (5th ed.). Pearson Prentice Hall. pp. 153–155.

ISBN 978-0-13-048185-6.[3] Kurishita H, Kayano H, Narui M, Yamazaki M, Kano Y, Shibahara I (1993). "Effects of V-notch dimensions on Charpy impact test results

for differently sized miniature specimens of ferritic steel". Materials Transactions - JIM (Japan Institute of Metals) 34 (11): 1042–52.ISSN 0916-1821.

[4] Mills NJ (February 1976). "The mechanism of brittle fracture in notched impact tests on polycarbonate". Journal of Materials Science 11 (2):363–75. Bibcode 1976JMatS..11..363M. doi:10.1007/BF00551448.

[5][5] ASTM E23 Standard Test Methods for Notched Bar Impact Testing of Metallic Materials[6][6] ISO 148-1 Metallic materials - Charpy pendulum impact test - Part 1: Test method[7][7] EN 10045-1 Charpy impact test on metallic materials. Test method (V- and U-notches)[8] Mathurt KK, Needleman A, Tvergaard V (May 1994). "3D analysis of failure modes in the Charpy impact test". Modeling and Simulation in

Materials Science Engineering 2 (3A): 617–35. Bibcode 1994MSMSE...2..617M. doi:10.1088/0965-0393/2/3A/014.[9][9] ASTM A370 Standard Test Methods and Definitions for Mechanical Testing of Steel Products

External links• Charpy Impact Testing module at steeluniversity.org (http:/ / www. steeluniversity. org/ content/ html/ eng/

default. asp?catid=151& pageid=2081271949), including a fully interactive simulation• Online Curvefitting Calculator for Charpy Impact Testing (http:/ / www. novanumeric. com/ samples.

php?CalcName=Charpy)

Article Sources and Contributors 3

Article Sources and ContributorsCharpy impact test  Source: http://en.wikipedia.org/w/index.php?oldid=504697506  Contributors: Ace of Spades, Acussen, Alansohn, Amgreen, Andrejj, Apgestoso, Bluemoose, Bronsonboy,Calmer Waters, Catgut, Causa sui, ChemGardener, Cst17, DO11.10, Davidtphillips, DocWatson42, Dsp13, Durchschnitt, Ebyabe, Flyhighplato, Grim23, Hooperbloob, IntrigueBlue, Inwind,James086, Jillar427, Kjkolb, LeadSongDog, LorenzoB, Materialscientist, Materialtech, Meisam, Mmarre, Mr Stephen, Myofilus, Nguyễn Thanh Quang, Nickboey22305, ObfuscatePenguin, OldMoonraker, Peterlewis, Pj.patches, Retired username, Romary, Rtcoles, Rubber impact bar, Siafu, Tombarnes101, Useight, Verkhovensky, Vrenator, Wizard191, WoodenKopf, Zapvet, Zs, 75anonymous edits

Image Sources, Licenses and ContributorsFile:Kerbschlagbiegeversuch Maschine.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Kerbschlagbiegeversuch_Maschine.jpg  License: GNU Free Documentation License Contributors: Ies, Stahlkocher

LicenseCreative Commons Attribution-Share Alike 3.0 Unported//creativecommons.org/licenses/by-sa/3.0/