increases the fatigue strength

decreases the fatigue strength

has no influence on fatigue strength

alone has no influence on fatigue strength

same

higher

lower

depends on other factors

acts when external load is applied

becomes zero when external load is removed

is independent of external loads

is always harmful

best method

extremely hazardous

has no effect as regards fatigue strength

cheapest method

surface

just below the surface

within the core

none of the above.