STREMA Flashcards

1
Q

Stress

A

σ = P / A

P = tensile or compressive load
A = cross-sectional area,

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2
Q

Doulble shear

A

σ = P / nA

n =2 (clevis)

P = tensile or compressive load
A = cross-sectional area

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3
Q

Punching Shear

A

σ = P / πDt

πDt = punching area

P = tensile or compressive load
A = cross-sectional area,

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4
Q

Thin walled pressured vessel

Tangetial Stress

A

σₜ = PᵢD / 2t = (Pᵢ - Pₒ)D/2t

σt = 2σL

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5
Q

Thin walled pressured vessel

Longitudinal/Spherical Stress

A

σₜ = PᵢD/4t = (Pᵢ - Pₒ)D/2t

σt = 2σL

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6
Q

Hooke’s Law

A

σ = Ε ε

Ε = Young’s Modulus/ Modulus of Elasticity
ε = strain

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7
Q

Factor of Safety

A

FoS = σᵤ/σₐ

σₐ = σt

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8
Q

Elongation

A

δL = PL/EA

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9
Q

Elongation due to its weight

A

δW= ρgL²/2E = mgL/2AE

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10
Q

Total Elongation

A

δT = δL + δW

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11
Q

Shear Modulus

A

G = τ / γ
G= shear stress/ shear strain

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12
Q

Poisson’s Ratio

A

v = - ε lat / ε long
Δd/d / ΔL/L

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13
Q

Modulus of Rigidity

A

G = E / 2(1+ ⱴ)

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14
Q

Bulk Modulus

A

k = E / 3(1-2ⱴ)

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15
Q

Thermal Stess

A

σᴛ = αEΔT

σₐ = σᴛ + σ,yield

α = coefficient of linear expansion

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16
Q

Torsion

Torsional Shearing Stress

A

τ, max = Tr/J

where:
T = torsion
r = radius
J = Polar moment of inertia

17
Q

Torsion

Polar Moment of Inertia

Solid Shaft

A

J = πD⁴/32

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18
Q

Torsion

Polar Moment of Inertia

Hollow Shaft

A

J = π(Dₒ⁴-dᵢ⁴)/32

19
Q

Torsion

Angle of Twist

A

θ = TL/JG x 360°/2π

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20
Q

Torsion

Power through shaft

A

P = 2πƒT

ƒ = Hz, cps, rps

21
Q

Helical Spring

Approximation Method

A

τ, max = 16PR/πD³ · [ 1 + d/4R]

22
Q

Helical Spring

AM Wahl’s Formula
Exact Method

A

τ, max = 16PR/πD³ · [ 4m-1/4m-4 + 0.615/m]

m = 2R/d
R = mean radius

23
Q

Helical Spring

Spring Deflection/Deformation

A

δ = 64PR³n/Gd⁴

where:
n = no. of twists of spring

24
Q

Spring Constant

A

k = Pᴛ/δᴛ

25
# Spring Constant Series
P1 = P2 δᴛ = δ1+δ2 1/k = 1/k1 + 1/k2 + ... + 1/kn
26
# Spring Constant Parallel
Pᴛ = P1 + P2 δ1 = δ2 k = k1 + k2 + ... + kn
27
# Cables: Parabolic Cables Tension at the Supports
T = √(ωL/2)² + H² ## Footnote ω = weigh of horiz. length L = spand of supports Try Willy Wonka's Lollipops Squared Over Two, Whole-Square, Plus Height-Squared
28
# Cables: Parabolic Cables Tension at the lowest point
H = ωL²/8d ## Footnote ω = weigh of horiz. length L = spand of supports d = sag
29
# Cables: Parabolic Cables Approx. Length of Cable
S = L + 8d²/3L - 32d⁴/5L³ ## Footnote L = spand of supports d = sag
30
# Cables: Caternary Cables 1. Half Length 2. Support Weight
1. S = C sinh (x/C) 2. y = C cosh (x/C) y² = S² + C² ## Footnote c = clearance
31
# Cables: Caternary Cables Max Tension
T = ωy ## Footnote y = height
32
# Cables: Caternary Cables Tension at Lowest Point
H = ωC ## Footnote c = clearance
33
# Cables: Caternary Cables W
W = ωS ## Footnote c = clearance