a

contact radius; outer radius in Roca and Mikic mechanical model; heat-flux radius at top of doubler, Gluck and Young (m)

A

area (m ²)

A _b

area of contact region near bolt or screw (m ²)

A _N

area divided by number of bolts or screws (m ²)

b

component radius; doubler radius, Gluck and Young (m)

C

conductance (W/K)

C _b

bolt region conductance (W/K)

CCD

charge-coupled device

CTE

coefficient of thermal expansion (K ¹)

d

height of waviness represented as spherical crown; gas gap between parallel plates; distance between bolt centers (m)

d*

normalized distance between bolt centers, d* = d/(2 r _O)

D _s

bolt-shaft diameter (m)

DLR

Deutsches Zentrum f r Luft-und Raumfahrt e.V. /German Aerospace Center

E

elastic modulus; effective elastic modulus, Roca and Mikic (N/m ²)

E ?

effective elastic modulus (N/m ²),

f

factor from Song representing Integral model of Yovanovich,

F

heat flux (W/m ²)

F _O

average heat flux through doubler, Gluck and Young (W/m ²)

F _S

heat flux over radius, a, at top of doubler, Gluck and Young (W/m ²)

F*

dimensionless heat flux, Ayres et al., F* = ( F ? _ER _E/k _E) ( E _E/H _E) ( ? _i/ ? _o) ³[0.5(1 + P _amb/ P _atm)] ²

G

dimensionless gap resistance, G = k _g