Fahmi Mubarok, ST. MSc. 1 - 1 |Jurusan Teknik Mesin ITS| Gambar dibawah ini adalah grafik P - ΔL hasil uji tarik suatu batang baja berdiameter 15 mm dan gauge length 200 mm. Reduction of area 10 %. Tentukan : 1. Tensile strength dan offset yield strength 2. Kekakuan baja tersebut... 3. Modulus ketangguhan dan modulus resilience 4. Ductility dalam percentage of elongation 5. Tegangan sebenarnya pada saat patah Pembahasan Pembahasan Tugas Tugas 4 4 Note: - Tugas dikumpulkan minggu depan sebelum perkuliahan dimulai - Tugas dikerjakan di kertas A4
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Fahmi Mubarok, ST. MSc. 1 - 1|Jurusan Teknik Mesin ITS|
Gambar dibawah ini adalah grafik P - ΔL hasil uji tarik suatu batang baja berdiameter 15 mm dan gauge length 200 mm. Reduction of area 10 %.
Symbol TypeHSC C Visual reading typeHSD D Ludicator type
Test MachineHardness Symbol
Tentang Shore Scleroscope
1. The Scleroscope is a very old hardness testing instrument, originating in the early 1900's.
2. It is a dynamic indentation hardness test that drops a diamond-tipped hammer vertically from a fixed height onto the surface of the material under test.
3. The height of the rebound of the hammer is a measure of the hardness of the material
4. The harder the material, the higher the rebound
5. Two different models were produced.6. The C testers used a glass tube
graduated from 0 to 140 to measure the rebound. The operator would observe the height of the rebound on the graduated glass tube.
7. The D model had a 0 to 120 dial gage that would display the rebound height.
Fahmi Mubarok, ST. MSc. 1 - 7|Jurusan Teknik Mesin ITS|
DurometerDurometer TestTest
Definisi
Durometer type
Main spring
Indentor For use on:
A 822 g Frustum coneSoft Rubber,
Elastomers, Waxes, Printing Rollers.
B 822 g Sharp 30o Rubber, Elastomers.
C 10 lb Frustum cone Medium-hard Rubber, Plastics.
D 10 lb Sharp 30o Hard Rubber, Plastics.
D0 10 lb 3/32-in. sphereDense Textile Winding,
Medium Printing Rollers.
0 822 gr 3/32-in. sphere Soft Printing Rollers, Textile Windings.
00 4 oz 3/32-in. sphere Sponge Rubber, Very soft Rubber.
000 4 oz 1/2-in. diam, spherical Very Soft Materials, Open Cell Foam.
Tentang Durometer
Simbol Durometer
4. Pembacaan angka kekerasan secaraotomatis
5. Tipe yang umum digunakan adalah tipeA dan tipe D
6. Tipe A untuk material yang lebih lunak7. Tipe D untuk material yang lebih keras
Pengujian kekerasandengan cara indentasiuntuk material plastik atau karet.
1. Digunakan untuk soft-material sepertiplastik atau karet
2. Pengukuran kekerasan dengan carakedalaman indentasi
3. Semakin dalam indentasi, semakin lunakmaterial
Fahmi Mubarok, ST. MSc. 1 - 8|Jurusan Teknik Mesin ITS|
MesinMesin HardnessHardness
Mesin Hardness disamping digunakanuntuk:
–Rockwell test–Brinell test–Vickers test–Knoop test–Meyer test
Yang membedakan adalah jenisindentor dan bebannya
Fahmi Mubarok, ST. MSc. 1 - 9|Jurusan Teknik Mesin ITS|
Rockwell TestRockwell Test
DefinisiIndentor berbentuk bola atau kerucut ditekanke permukaan benda uji dengan beban minor, sehingga ujung indentor menembuskedalaman hA.Setelah itu penekanan diteruskan denganmemberikan beban mayor selama beberapasaat, sehingga ujung indentor menembuskedalaman hBKemudian beban utama dilepas, hanya tinggalbeban awal, sehingga kedalaman penetrasiujung indentor adalah hC
1. Indentor :Bola baja yang dikeraskan dengandiameter 1/16”, 1/8”, ¼” dan ½”Kerucut intan dengan sudut 120o
2. Untuk Rockwell test beban minor 10 kg, danbeban mayor 60, 100 dan 150 kg
3. Untuk superficial Rockwell test beban minor 3 kg dan beban mayor 15, 30 dan 45 kg
4. Seperficial Rockwell test digunakan untukmaterial yang tipis
5. Range penggunaan skala hardness harussesuai dengan tabel.
6. Permukaan benda uji harus tegak lurusdengan indentor
7. Jarak antar pusat diameter indentasi haruslebih dari 4 d dan jarak antara pusat indentasidengan ujung benda uji harus lebih dari 2.5 d.
8. Selama waktu penekanan, indentor tidakboleh mendapat beban kejut atau getaran danbeban harus diberikan secara perlahan-lahan
Prosedur
Fahmi Mubarok, ST. MSc. 1 - 10|Jurusan Teknik Mesin ITS|
Rockwell TestRockwell Test
Skala Rockwell TestSkala Indentor Beban Mayor Range Material
C 150 10 - 70Hardened steels, cast irons, deep case-hardened
D 100 20 - 80Thin but hard steel, medium depth case-hardened
Contoh75 HBS 10/3000 = kekerasan Brinell 75 dihitung dengan bola baja diameter 10 mm dengan gaya 3000 kg
Fahmi Mubarok, ST. MSc. 1 - 13|Jurusan Teknik Mesin ITS|
Vickers TestVickers Test
DefinisiIndentor berbentuk piramid dengan alas bujur sangkar ditekan ke permukaan bendauji dan diagonal hasil penekanan diukursetelah identor dipindahkan dari benda uji.
Perhitungan
2
854.1d
PVHN=
P = Gaya Tekan (kgf)d = Diagonal tapak tekan (mm)
Prosedur1. Indentor berbentuk piramid intan
beralas bujur sangkar dengan sudutpuncak antara 2 sisi yang berhadapan136o
2. Permukaan benda uji harus tegak lurusdengan indentor
3. Gaya tekan yang bekerja
4. Pembebanan dilakukan berlahan-lahantanpa menimbulkan beban kejut ataugetaran
5. Lama waktu penekanan antar 10 – 15 s6. Jarak antar indentasi harus memenuhi:
Material of test piece Stell, Copper and Copper alloys
Light metal, lead, zinc and their alloys
Distance between the centers of indentations 3 d min. 6 d min.
Fahmi Mubarok, ST. MSc. 1 - 14|Jurusan Teknik Mesin ITS|
Vickers TestVickers Test
7. Pengukuran diagonal indentasi (d)dilakukan 2 kali dan saling tegak luruskemudian dirata-rata
1. Permukaan benda uji harus bersih daribenda lain seperti oli.
2. Permukaan benda uji harus halus3. Ketebalan benda uji minimum harus
1.5 kali diagonal indentasi4. Permukaan benda uji harus datar
640 HV 30 = kekerasan Vickers 640 dengan gayapembebanan 30 kg selama selang waktu 10 –15 s640 HV 30/20 = kekerasan Vickers 640 dengan gayapembebanan 30 kg selama selang waktu 20 s
Benda Uji
Contoh
Tentang Vickers
1. Pengukuran tidak terpengaruh olehbesarnya gaya tekan
2. Hasilnya akan sama walaupun pengukurandilakukan dengan gaya tekan yang berbeda
3. Dapat mengukur kekerasan bahan mulaidari yang sangat lunak sampai yang sangatkeras tanpa perlu mengganti gaya tekan
4. Gaya tekan yang bekerja tergantung padakekerasan atau ketebalan bahan yang diujiagar diperoleh tapak tekan yang mudahdiukur dan tidak ada anvil effect (pada bendayang tipis)
5. Untuk Vickers biasa digunakan gaya tekanantara 1 kg sampai 120 kg
6. Untuk Micro Vikers digunakan gaya tekanantara 0.001 kg sampai 1 kg
Fahmi Mubarok, ST. MSc. 1 - 15|Jurusan Teknik Mesin ITS|
KnoopKnoop TestTest
DefinisiIndentor berbentuk piramid dengan alas belah ketupat ditekan ke permukaan bendauji dan diagonal hasil penekanan diukursetelah identor dipindahkan dari benda uji.
Perhitungan
2
229.14l
PKHN=
P = Gaya Tekan (kgf)l = Diagonal terpanjang
tapak tekan (mm)
Prosedur1. Indentor berbentuk piramid intan
beralas belah ketupat yang perbandingan panjang diagonalnya1 : 7 dengan sudut puncak antara 2 sisiyang berhadapan 172.3o dan 130o
2. Permukaan benda uji harus tegak lurusdengan indentor
3. Gaya tekan yang bekerja
4. Pembebanan dilakukan berlahan-lahantanpa menimbulkan beban kejut ataugetaran
5. Lama waktu penekanan antar 10 – 15 s6. Jarak antar indentasi harus memenuhi:
Fahmi Mubarok, ST. MSc. 1 - 16|Jurusan Teknik Mesin ITS|
KnoopKnoop TestTest
7. Hanya dilakukan pengukuran terhadapdiagonal terpanjang indentasi (l)
1. Permukaan benda uji harus bersih daribenda lain seperti oli.
2. Permukaan benda uji harus halus3. Ketebalan benda uji minimum harus
0.3 kali diagonal terpanjang indentasi4. Permukaan benda uji harus datar
640 HK 0.1 = kekerasan Knoop 640 dengan gayapembebanan 0.1 kg selama selang waktu 10 –15 s640 HK 0.1/20 = kekerasan Knoop 640 dengan gayapembebanan 0.1 kg selama selang waktu 20 s
Benda Uji
Contoh
Tentang Knoop
1. Pengujian Knoop menghasilkan indentasiyang sangat dangkal
2. Cocok untuk pengujian kekerasan padalapisan yang sangat tipis
Fahmi Mubarok, ST. MSc. 1 - 17|Jurusan Teknik Mesin ITS|
Meyer TestMeyer Test
DefinisiIndentor berbentuk bola ditekan kepermukaan benda uji dan diameter hasilpenekanan diukur setelah identordipindahkan dari benda uji.
Perhitungan
2
4
an tapak tekproyeksi Luas tekanGaya
d
P
MHN
π=
=
P = Gaya Tekan (kgf)D = Diameter Indentor (mm)d = Diameter Tapak Tekan (mm)
1. Indentor bola baja yang dikeraskan2. Kekerasan Meyer dihitung berdasarkan luas
proyeksi tapak tekan3. Pengukuran tidak terpengaruh oleh
besarnya gaya tekan4. Hasilnya akan sama walaupun pengukuran
dilakukan dengan gaya tekan yang berbeda5. Pengujian Meyer jarang digunakan
Tentang Meyer
Fahmi Mubarok, ST. MSc. 1 - 18|Jurusan Teknik Mesin ITS|
Accuracy of Any Indentation Hardness TestAccuracy of Any Indentation Hardness Test
Condition of the Indenter• Flattering of a steel-ball indenter will result in errors in the
hardness number• The ball should be checked frequently for permanent
deformation and discarded when such deformation occurs• Diamond indenters should be checked for any sign of
chipping
Accuracy of Load Applied• The tester should apply loads in the stated range with
negligible error• Loads greater than the recommended amount should not be
used for accurate testing
Fahmi Mubarok, ST. MSc. 1 - 19|Jurusan Teknik Mesin ITS|
Accuracy of Any Indentation Hardness TestAccuracy of Any Indentation Hardness Test
Shape of the Specimen• The greatest accuracy is obtained when the test surface is
flat and normal to the vertical axis of the indenter• A long specimen should be properly supported so that it
does not tip• A flat surface should be prepared, if possible, on a
cylindrical shaped specimen, and a V-notch anvil should be used to support the specimen
Fahmi Mubarok, ST. MSc. 1 - 20|Jurusan Teknik Mesin ITS|
Accuracy of Any Indentation Hardness TestAccuracy of Any Indentation Hardness Test
Thickness of Specimen• The specimen should be thick enough so that no bulge
appears on the surface opposite that of the impression• The recommended thickness of the specimen is at least ten
times the depth of the impression
Surface Condition of the Specimen• The surface of the specimen on which the hardness reading
is to be taken should be flat• Any pits, scale, or grease should be removed by grinding
or polishing
Fahmi Mubarok, ST. MSc. 1 - 21|Jurusan Teknik Mesin ITS|
Accuracy of Any Indentation Hardness TestAccuracy of Any Indentation Hardness Test
Location of Impressions• Impressions should be at least 2.5 diameters from the edge
of the specimen and should be at least 4 diameters apart for ball tests
Surface Condition of the Specimen• The surface of the specimen on which the hardness reading
is to be taken should be flat• Any pits, scale, or grease should be removed by grinding
or polishing
Fahmi Mubarok, ST. MSc. 1 - 22|Jurusan Teknik Mesin ITS|
PerbandinganPerbandingan PemakaianPemakaian Hardness TestHardness Test
Brinell Test• Since the Brinell test leaves a relatively large impression, it
is limited to heavy sections• This is an advantage, however, when the material tested is
not homogeneous• The surface of the test piece does not have to be so smooth
as that for smaller impressions• Using a microscope to measure the diameter of the
impression is not so convenient as reading a dial gauge• Because of deformation of the steel ball, the Brinell test is
generally inaccurate above 500 HB• The range may be extended to about 650 HB with a
tungsten carbide ball
Fahmi Mubarok, ST. MSc. 1 - 23|Jurusan Teknik Mesin ITS|
PerbandinganPerbandingan PemakaianPemakaian Hardness TestHardness Test
Brinell Test
Fahmi Mubarok, ST. MSc. 1 - 24|Jurusan Teknik Mesin ITS|
PerbandinganPerbandingan PemakaianPemakaian Hardness TestHardness Test
Rockwell Test• The Rockwell test is rapid and simple in operation• Since the loads and indenters are smaller than those used in
the Brinell test, the Rockwell test may be used on thinner specimens, and the hardest as well as the softest materials can be tested
Fahmi Mubarok, ST. MSc. 1 - 25|Jurusan Teknik Mesin ITS|
PerbandinganPerbandingan PemakaianPemakaian Hardness TestHardness Test
Vickers Test• The Vickers tester is the most sensitive of the production
hardness tester• It has single continuous scale for all materials• Hardness number is virtually independent of load• Because of the possibility of using light loads, it can test
thinner sections than any other production test• The square indentation is the easiest to measure accurately
Fahmi Mubarok, ST. MSc. 1 - 26|Jurusan Teknik Mesin ITS|
PerbandinganPerbandingan PemakaianPemakaian Hardness TestHardness Test
Vickers Test
Fahmi Mubarok, ST. MSc. 1 - 27|Jurusan Teknik Mesin ITS|
PerbandinganPerbandingan PemakaianPemakaian Hardness TestHardness Test
Microhardness Test• The microhardness test is basically a laboratory test• The use of very light loads permits testing of very small
parts and very thin sections• It can be used to determine the hardness of individual
constituents of the microstructure• Since the smaller the indentation, the better the surface
finish must be, a great deal more care is required to prepare the surface for microhardness testing
• The surface is usually prepared by the technique of metallographic polishing
Fahmi Mubarok, ST. MSc. 1 - 28|Jurusan Teknik Mesin ITS|
PerbandinganPerbandingan PemakaianPemakaian Hardness TestHardness Test
Scleroscope Test• The principal advantages of the scleroscope are:
– The small impressions that remain– The rapidity of testing– Portability of the instrument
• However, result tend to be inaccurate unless proper precautions are taken:– The tube must be perpendicular to the test piece– Thin piece must be properly supported and clamped– The surface to be tested must be smoother than for most other
testing methods– The diamond tip should not be chipped or cracked
Fahmi Mubarok, ST. MSc. 1 - 29|Jurusan Teknik Mesin ITS|