Eneo la mbegu ya mvutano la boliti ni nini?

Eneo la nguvu ya mvutano (As) ni eneo la sehemu ya msalaba inayotumiwa kuhesabu uwezo wa kupiga kwa kuvuta wa kiziba kinachouchimba. Ni ndogo kuliko eneo la shingo la kawaida kwa sababu inahesabu jiometri ya mzizi wa thread. Inafafanuliwa katika ISO 898-1 na inategemea kipenyo cha pitch na kipenyo cha ndogo cha thread.

Je, nguvu ya mvutano ya bolt inakokotolewa vipi?

Bolt ultimate tensile load is calculated as Ft = Rm × As, where Rm is the ultimate tensile strength of the bolt material (determined by property class) and As is the tensile stress area. For example, a class 8.8 bolt has Rm = 800 MPa.

Daraja la mali 8.8 la bolt linamaanisha nini?

The first number (8) represents 1/100th of the minimum ultimate tensile strength in MPa (800 MPa). The second number (8) represents 10× the ratio of yield strength to ultimate tensile strength (0.8). So yield = 800 × 0.8 = 640 MPa.

Je, nguvu ya shear ya bolt inakokotolewa vipi?

ISO 898-1 does not specify shear strength — it covers tensile and proof-load properties only. A common simplified estimate takes shear strength as 60% of tensile strength: Fs = 0.6 × Rm × As, based on the von Mises yield criterion. Design codes such as Eurocode 3 (EN 1993-1-8) apply their own factors (0.6 or 0.5 depending on property class) plus partial safety factors. For single shear, use one stress area; for double shear, multiply by 2.

Kuna tofauti gani kati ya mzigo wa uthibitisho na nguvu ya mvutano?

Mzigo wa uthibitisho ni nguvu ya juu zaidi ambayo bolt inaweza kuvumilia bila upanuzi wa kudumu (kikomo cha elasticity). Nguvu ya mvutano ya kawaida ni nguvu ya juu zaidi kabla ya kuvunjika. Mkazo wa mzigo wa uthibitisho (Sp) ni takriban asilimia 90 ya nguvu ya mavuno kwa darasa la mali nyingi.

Zana ya Uhandisi Isiyolipisha

Kikokotali cha Nguvu ya Mvutano & Shear ya Bolt

Calculate the ultimate tensile load of metric bolts from ISO 898-1 property-class data, plus a simplified shear capacity estimate. Select bolt size and property class.

ISO 898-1 M3 – M64 Daraja 4.6 – 12.9

Bolt Size

Property Class

Shear Planes

Quick presets

Results

Nguvu ya Mvutano wa Mwisho (Ft)

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Shear Capacity (Fs, simplified estimate)

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Eneo la Dhiki ya Mvutano (As)

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Mizigo ya Mavuno (Fy)

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Nguvu ya Mvutano wa Mwisho (Rm)

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Nguvu ya Mvutano wa Mwisho

Nguvu ya mvutano kubwa zaidi ambayo bolt inaweza kusumbuliwa kabla ya kuvunjika:

R_m — nguvu ya mvutano wa mwisho (MPa), kutoka kwa darasa la mali
A_s — eneo la dhiki ya mvutano (mm²), kutoka ISO 898-1 / ISO 261

Shear Capacity (Simplified Estimate)

ISO 898-1 defines the tensile and proof-load properties of bolts — it does not specify shear strength. The value shown here is a widely used simplified engineering estimate that takes shear strength as approximately 60% of tensile strength (based on the von Mises criterion, τ ≈ 0.58 σ):

Kwa kukatia mara mbili, zidisha kwa 2 (nyuso mbili za kukatia).

⚠️ Shear design note: Actual shear capacity depends on whether the shear plane passes through the threads or the unthreaded shank, on joint slip and plate bearing, and on fatigue loading. Design codes define their own values — e.g. Eurocode 3 (EN 1993-1-8) uses F_v = α_v × f_ub × A with α_v = 0.6 for classes 4.6, 5.6 and 8.8 but 0.5 for classes 4.8, 5.8, 6.8 and 10.9, together with partial safety factors. Always verify shear-loaded joints against the applicable structural or mechanical design code, not this simplified estimate alone.

Madarasa ya Mali kwa mujibu wa ISO 898-1

Class	Rm (MPa)	Rp0.2 (MPa)	Typical Use
4.6	400	240	Nguvu ndogo, matumizi ya jumla
5.8	520	420	Muundo, bila upachikaji wa mapema
8.8	800	640	Uendeshaji wa magari, mashine (ya kawaida zaidi)
10.9	1040	940	Muundo wa nguvu ya juu
12.9	1220	1100	Nguvu ya kiwango cha juu (chuma cha aloi)

Mfano wa Vitendo

Mfano — Bolt ya M10 × 8.8

Given: Bolt ya M10, darasa la mali 8.8, kukatia moja

A_s = 58.0 mm², R_m = 800 MPa

F_t = 800 × 58.0 = 46,400 N = 46.4 kN

F_s = 0.6 × 800 × 58.0 = 27,840 N = 27.8 kN

⚠️ Note: Hii ni ujazo wa juu zaidi bila sababu za usalama. Tumia sababu za usalama zinazofaa (kawaida 2–3 kwa tuli, 4–6 kwa fatigue) kwa madhumuni ya muundo.