allowable max bending corrected stress of rectangular spring wire 1

[2yy2]

Hi all,

I'm looking for the tensile strength and the allowable max bending corrected stress (static/fatigue load) for a rectangular spring wire (1.5mm*2.4mm). the wire material is music wire.

Thank you, regards,

12c2yy2

 

[sbozy25]

Tensile: 276-305ksi


Max allowable stress depends on the type of spring you are talking about.

for example, a compression spring maximum allowable stress in most applications is 65% of KW2

 

[2yy2]

sbozy25,
thank you for your quick reply.
regarding to the tensile strength, is there a formula to calculate it for rectangular wire(such as the formula for round wire Sut=A/d^m)?
this is a torsion spring so I would like to know the maximum allowable bending stress for helical torsion spring in static / cyclic application. What do you think, it is correct to use 60% Sut for static application and 50% Sut for cyclic application (1.000.000) as estimated max. values?

Thank you, regards,

12c2yy2

Ps: sorry for my “basic” english..

 

[israelkk]

sbozy25

Where did you get the 276-305ksi value? ASTM A228 is for round wire mainly.

 

[sbozy25]

israelkk

I got the 276-305ksi value off of a spread sheet I used when I worked at a spring compnay.

 

[israelkk]

sbozy25

The 276-305ksi value is the value in ASTM A228 for round wire with a diameter equal to the larger dimension of the rectangular wire but, it doesn't really refer to rectangular wire. Do you know of a spec for rectangular wire of music wire?

 

[sbozy25]

When I worked for the spring company I was given a rule of thumb for calculations. The engineer who taught me this has been in the industry since the late seventies so he knows his stuff.

He told me that to simplify rectangular wire, simply take both flat dimensions and look at what the corresponding round wire tensile would be, then pick the smaller of the two.

Seems to work very well for calculation purposes.

 

[sbozy25]

I suppose I should clarify... We would roll our own wire out to square, so that is kind of how we had to estimate our values.

I just realized my first response kind of came off arrogant without an explenation... lol... sorry...

 

[koza19]

Stress calculations
Wound on Flat
S=6(M)/bt^2 M=Ebt^3T/6.6(Nt)D

Wound on Edge
S=6(M)/tb^2 M=Ebt^3T/6.6(Nt)D

S=bending Stress PSI
M=Moment or Torque lb/in
b=Width,in
t=Thickness, in
E=Modulus of elasticity psi (music wire 30ksi)
T=Deflection, number of turns or revolutions of spring
Nt= Number of coils
D=Mean coil diameter

 

[koza19]

Sorry the Modulus of elasticity is 30 x 10^6 psi

 

[sbozy25]

ckozka

Not to be rude... but... Ummm... What good does that do spitting the formula verbatim from a book? Those formulas really don't tell you what he was looking for. He was looking for tensile strength and maximum allowable stress. You didn't provide any substance to the thread...