Answer:
B only
Explanation:
Squeeze-type resistance spot welding (STRSW)is a type of electric resistance welding that brings about the weld on interfacing sheet metal pieces through which heat generated from electric resistance bring about fusion and welding of the two pieces together
Therefore, it is not meant for opening but joints but it can be used for making replacement spot welds adjacent to the original spot weld due to the smaller heat affected zone (HAZ) created by the STRSW process.
The answer to this problem is the results of the point A
Answer:
Explanation:
Mean temperature is given by
![T_mean = \frac{T_i + T_ \infinity}{2}\\\\T_mean = \frac{200 + 15}{2}](https://tex.z-dn.net/?f=T_mean%20%3D%20%5Cfrac%7BT_i%20%2B%20T_%20%5Cinfinity%7D%7B2%7D%5C%5C%5C%5CT_mean%20%3D%20%5Cfrac%7B200%20%2B%2015%7D%7B2%7D)
Tmean = (Ti + T∞)/2
![T_mean = 107.5^{0}](https://tex.z-dn.net/?f=T_mean%20%3D%20107.5%5E%7B0%7D)
Tmean = 107.5⁰C
Tmean = 107.5 + 273 = 380.5K
Properties of air at mean temperature
v = 24.2689 × 10⁻⁶m²/s
α = 35.024 × 10⁻⁶m²/s
= 221.6 × 10⁻⁷N.s/m²
= 0.0323 W/m.K
Cp = 1012 J/kg.K
Pr = v/α = 24.2689 × 10⁻⁶/35.024 × 10⁻⁶
= 0.693
Reynold's number, Re
Pv = 4m/πD²
where Re = (Pv * D)/![\mu](https://tex.z-dn.net/?f=%5Cmu)
Substituting for Pv
Re = 4m/(πD
)
= (4 x 0.003)/( π × 6 ×10⁻³ × 221.6 × 10⁻⁷)
= 28728.3
Since Re > 2000, the flow is turbulent
For turbulent flows, Use
Dittus - Doeltr correlation with n = 0.03
Nu = 0.023Re⁰⁸Pr⁰³ = (h₁D)/k
(h₁ × 0.006)/0.0323 = 0.023(28728.3)⁰⁸(0.693)⁰³
(h₁ × 0.006)/0.0323 = 75.962
h₁ = (75.962 × 0.0323)/0.006
h₁ = 408.93 W/m².K