Kekuatan tegangan

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Ujian tegangan yang dijalankan ke atas komposit sabut kelapa. Saiz spesimen tidak mengikut piawai.

Kekuatan tegangan ( atau  ) ditentukan oleh maksima dan minima dari lengkuk tegangan-terikan (stress-strain curve) dan secara umum, menunjukkan bila kegentingan berlaku. Oleh keran ia merupakan ciri sifat intensif, nilainya tidak bergantung kepada saiz contoh ujian. Ia bagaimanapun bergantung kepada penyediaan contoh dan suhu persekitaran dan bahan ujikaji.

Kekuatan tensil, bersama dengan modulus kekenyalan dan ketahanan hakisan, merupakan tatarajah penting bagi bahan kejuruteraan yang digunakan dalam struktur dan peranti mekanikal. Ia khusus bagi bahan seperti aloi, bahan sebatian, seramik, plastik dan kayu.

Penjelasan[sunting | sunting sumber]

Terdapat tiga takrifan kekuatan tegangan:

Kekuatan alah
Tegangan yang mana terikan bahan berubah daripada ubah bentuk kenyal kepada ubah bentuk plastik, menyebabkannya berubah secara kekal.
Kekuatan muktamad
Kekuatan tegangan maksimum yang boleh ditampung oleh sesuatu bahan apabila dikenakan tegangan, mampatan ataupun ricihan. Ia merupakan kekuatan tegangan maksimum pada lengkuk tegangan-terikan.
Kekuatan putus
Koordinat tegangan pada lengkuk tegangan-terikan pada titik putus atau gagal.


Kekuatan tegangan biasa[sunting | sunting sumber]

Sesetengah kekuatan tegangan biasa bagi sesetengah bahan:

Bahan Kekuatan alah
(MPa)
Kekuatan muktamad
(MPa)
Ketumpatan
(g/cm³)
Tali nanotiub karbon ? 3,600 1.3
Keluli ASTM struktur A36 steel 250 400 7.8
Keluli, API 5L X65 (Fikret Mert Veral) 448 531 7.8
Keluli, aloi kekuatan tinggi ASTM A514 690 760 7.8
Keluli, untaian pretekanan (prestress) 1,650 1,860 7.8
Wayar Keluli     7.8
Keluli (AISI 1,060 0.6% carbon) Piano wire 2,200-2,482[1]   7.8
High density polyethylene (HDPE) 26-33 37 0.95
Polypropylene 12-43 19.7-80 0.91
Keluli tanah karat (Stainless steel) AISI 302 - Cold-rolled 520 860 8.19
Besi tuang 4.5% C, ASTM A-48 130 200  
Aloi titanium (6% Al, 4% V) 830 900 4.51
Aloi Aluminium 2014-T6[perlu rujukan] 400 455 2.7
TembagaCopper 99.9% Cu 70 220 8.92
Cupronickel 10% Ni, 1.6% Fe, 1% Mn, balance Cu 130 350 8.94
Brass 200+ 550 5.3
Tungsten   1,510 19.25
Glass   50 (in compression) 2.53
E-Glass N/A 3,450 2.57
S-Glass N/A 4,710 2.48
Basalt fiber N/A 4,840 2.7
Marble N/A 15  
Concrete N/A 3  
Carbon Fiber N/A 5,650 1.75
Human hair   380  
Spider silk (See note below) 1,000  
Silkworm silk 500    
Aramid (Kevlar or Twaron) 3,620   1.44
UHMWPE 23 46 0.97
UHMWPE fibers[2][3] (Dyneema or Spectra) 2,300-3,500 0.97
Vectran   2,850-3,340  
Polybenzoxazole (Zylon)   5,800  
Pine Wood (parallel to grain)   40  
Bone (limb) 104-121 130 1.6
Nylon, type 6/6 45 75 1.15
Getah - 15  
Boron N/A 3,100 2.46
Silikon, monocrystalline (m-Si) N/A 7,000 2.33
Silikon karbide (SiC) N/A 3,440  
Sapphire (Al2O3) N/A 1,900 3.9-4.1
Tiubnano karbon (see note below) N/A 62,000 1.34
Tiubnano karbon sebatian N/A 1,200[4] N/A
  • Note: Multiwalled carbon nanotubes have the highest tensile strength of any material yet measured, with labs producing them at a tensile strength of 63 GPa, still well below their theoretical limit of 300 GPa. The first nanotube ropes (20 mm long) whose tensile strength was published (in 2000) had a strength of 3.6 GPa, still well below their theoretical limit.[5]
  • Note: many of the values depend on manufacturing process and purity/composition.
  • Note: human hair strength varies by ethnicity and chemical treatments.
  • Note on spider silk strength: The strength of spider silk is highly variable. It depends on many factors including type of silk (every spider can produce several different types for different purposes), the particular species, the age of the silk, the temperature, the humidity, the rate that the stress is applied at during testing, the length of time the stress is applied and the way the silk is collected (forced silking or natural spinning)[6]. The value shown in the table, 1000Mpa, is roughly representative of the results from a few studies involving several different species of spider however specific results varied greatly.[7]
Elements in the annealed state Young's Modulus
(GPa)
Proof or yield stress
(MPa)
Ultimate strength
(MPa)
Aluminium 70 15-20 40-50
Tembaga 130 33 210
Emas 79   100
Besi 211 80-100 350
Lead 16   12
Nikel 170 14-35 140-195
Silikon 107 5,000-9,000  
Perak 83   170
Tantalum 186 180 200
Timah 47 9-14 15-200
Titanium 120 100-225 240-370
Tungsten 411 550 550-620
Zink (wrought) 105   110-200

(Source: A.M. Howatson, P.G. Lund and J.D. Todd, "Engineering Tables and Data" p41)


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Sumber[sunting | sunting sumber]

  • A.M. Howatson, P.G. Lund and J.D. Todd, "Engineering Tables and Data"
  • Giancoli, Douglas. Physics for Scientists & Engineers Third Edition. Upper Saddle River: Prentice Hall, 2000.
  • Köhler, T. and F. Vollrath. 1995. Thread biomechanics in the two orb-weaving spiders Araneus diadematus (Araneae, Araneidae) and Uloboris walckenaerius (Araneae, Uloboridae). Journal of Experimental Zoology 271:1-17.
  • Edwards, Bradly C. "The Space Elevator: A Brief Overview" http://www.liftport.com/files/521Edwards.pdf
  • T Follett "Life without metals"
  • Min-Feng Yu et al. (2000), Strength and Breaking Mechanism of Multiwalled Carbon Nanotubes Under Tensile Load, Science 287, 637-640
  • George E. Dieter. Mechanical Metallurgy. McGraw-Hill (UK), 1988

Rujukan[sunting | sunting sumber]

  1. ^ Don Stackhouse @ DJ Aerotech
  2. ^ Tensile and creep properties of ultra high molecular weight PE fibres
  3. ^ Mechanical Properties Data
  4. ^ http://www.iop.org/EJ/abstract/-search=56864390.1/0957-4484/18/45/455709 Z. Wang, P. Ciselli and T. Peijs, Nanotechnology 18, 455709, 2007.
  5. ^ "Tensile strength of single-walled carbon nanotubes directly measured from their macroscopic ropes" by F. Li, H. M. Cheng, S. Bai, G. Su, and M. S. Dresselhaus. DOI:10.1063/1.1324984
  6. ^ Elices; dll. "Finding Inspiration in Argiope Trifasciata Spider Silk Fibers". JOM. Dicapai 2009-01-23. 
  7. ^ Blackledge; dll. "Quasistatic and continuous dynamic characterization of the mechanical properties of silk from the cobweb of the black widow spider Latrodectus hesperus". The Company of Biologists. Dicapai 2009-01-23. 

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