We consider boundary value problems for 1D autonomous damped and delayed semilinear wave equations of the type $$\begin{aligned} \partial ^2_tu(t,x)- a(x,\lambda )^2\partial _x^2u(t,x)= b(x,\lambda ,u(t,x),u(t-\tau ,x),\partial _tu(t,x),\partial _xu(t,x)), \; x \in (0,1) \end{aligned}$$
∂
t
2
u
(
t
,
x
)
-
a
(
x
,
λ
)
2
∂
x
2
u
(
t
,
x
)
=
b
(
x
,
λ
,
u
(
t
,
x
)
,
u
(
t
-
τ
,
x
)
,
∂
t
u
(
t
,
x
)
,
∂
x
u
(
t
,
x
)
)
,
x
∈
(
0
,
1
)
with smooth coefficient functions a and b such that $$a(x,\lambda )>0$$
a
(
x
,
λ
)
>
0
and $$b(x,\lambda ,0,0,0,0) = 0$$
b
(
x
,
λ
,
0
,
0
,
0
,
0
)
=
0
for all x and $$\lambda $$
λ
. We state conditions ensuring Hopf bifurcation, i.e., existence, local uniqueness (up to time shifts), regularity (with respect to t and x) and smooth dependence (on $$\tau $$
τ
and $$\lambda $$
λ
) of small non-stationary time-periodic solutions, which bifurcate from the stationary solution $$u=0$$
u
=
0
, and we derive a formula which determines the bifurcation direction with respect to the bifurcation parameter $$\tau $$
τ
. To this end, we transform the wave equation into a system of partial integral equations by means of integration along characteristics and then apply a Lyapunov-Schmidt procedure and a generalized implicit function theorem. The main technical difficulties, which have to be managed, are typical for hyperbolic PDEs (with or without delay): small divisors and the “loss of derivatives” property. We do not use any properties of the corresponding initial-boundary value problem. In particular, our results are true also for negative delays $$\tau $$
τ
.