IRstuff, the goal is repeatable positioning after contact. A compliant dampening material could not do this. Obviously stainless steel on aluminum is not ideal but are necessary for the production process used. The rod assembly is guided concentrically to the hole in the aluminum housing. The...
Mechanism: Rod assembly made of 304 stainless with diameter of 4.6mm impacts onto housing of hard anodized 6061 aluminum. The aluminum housing has a hole of 4.1mm concentric to the rod assembly. Thus the annular area of contact is 4.67mm^2 (0.00724in^2). Static stress would be 1472 psi based on...
Customer is changing a pneumatic cylinder out to an electric actuator. Here are the application requirements:
Load: 100 lbf vertical
Speed: move .25" in .25 second
Power: 24 VDC
Power tranmission: any (ballscrew, cam, rack and pinion, etc.)
My company manufacturers their own electric actuators...
A simple slightly destructive test is to take the bolt and carefully touch a grinding wheel in motion. Carbon steel will have a large pattern of fan shaped sparks. Stainless will be much more linear and closer together. The larger the carbon content, the more the sparks will fan out. I have done...
IggyD,
My understanding is that the fretting was due to rotation of the spring and the ground end was fretting the aluminum, not the outside diameter of the spring contacting the housing.
Certainly we are going to do extensive life testing of this spring as we will be using over 30,000 a year. I guess what I need to do is utilize the strongest material (music wire) that is reasonable for fatigue purposes and apply the least stress possible and still obtain required system...
For the tensile strength numbers, Century Spring lists .030 in 302 SST as 282 ksi, .030 in Music Wire 330 ksi. The stress recommendations are out of their book as well.
israelkk, .246 is the correct number. Installed height should be .797. Sorry for the typo.
My understanding of design stress for maximum life of a stainless spring should be <=20% of minimum tensile strength. I show 282 ksi for 302 SST. Therefore maximum stress should be <=28.2 ksi. The applied...
sbozy25,
Is the life calculation you show of 250M with the stainless 302 or changing it to music wire and zinc plating? My understanding is with wire diameters under .040" shot peening may buckle the spring.
Thanks for the reply.
We have a customer requirement for a spring to last 200 million cycles. The current spring chosen by another engineer is Century Spring #70834S. The spring has the following specifications:
OD .300"
ID .240"
Free length .940"
Rate 7.600 lbf/in
Solid height .260"
Wire diamter .030"
Total coils...
