Kekuatan tegangan

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

Kekuatan tegangan ($\sigma_{UTS}$ atau $S_U$ ) 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

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

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		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	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 (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	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.
• 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). 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.

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

• 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

• http://www.albarrie.com/Filtration/fil-basalt.html

Pautan luar

• Stress-strain diagram
• January 2003 sci.physics thread on water tensile strength and trees
• Theory re the discrepancy in static vs dynamic measurements of water's tensile strength
• Engineering Stress-strain Curve
• Systems for measuring tensile strength
• Testing equipment to determine properties of materials including Tensile strength