Steels and Cast-Irons of Categories 1, 2, 3, 4, 6, 8, 9, 10, and 11 (See Cam Life Results below)

These categories allow a small amount of surface pitting to occur, at which time the pitting stabilizes. This is called non-progressive pitting.

If you allow up to ~15% pitting, the cam-life is extended.

In mission-critical applications, for example manned flight - you would not Allow Pitting.

Also, if this is a new and important application, then I would not Allow Pitting.

There are 14 Steel/Cast-Iron and Heat-Treatment categories, each with 3 Quality levels (ML,MQ,ME) - identical to the ISO 6336-5 Standard for Gears.

Steels Categories and Heat-Treatment

1.Normalized, Low-Carbon Wrought-Steelsa - St

2.Normalized, Low-Carbon, Cast-Steelsa  - St(cast)

3.Black Malleable Cast-Iron - GTS (perl)

4.Nodular Spheroidal Cast-Iron - GGG ( - see image above )

5.Grey Cast-Iron - GGG

6.Through-Hardened Wrought Carbon-Steelb - V

7.Through-Hardened Wrought Alloy-Steelsb - V

8.Through-Hardened Cast Carbon-Steel - V(cast)

9.Through-Hardened Cast Alloy-Steel - V(cast)

10.Case-Hardened Wrought-Steelsc - Eh

11.Flame or Induction-Hardened Wrought or Cast-Steels (IF)

12.Nitrided Nitriding Wrought-Steelsd - NT(nitr)

13.Through-Hardened Nitrided-Steelb - NV(nitr)

14.Through-Hardened Nitro-Carburized Wrought-Steele - (NV (nitr-car)

a - ISO 4948-2 (ISO10020) Part 2 - Classification of unalloyed and alloy steels according to main quality classes and main property or application

b - ISO 683-1 - Heat-treated Steels, alloy steels and free-cutting steel Part 1 - Quenched and Tempered unalloyed steels

c - ISO 683-11 - Heat-treated Steels, alloy steels and free-cutting steel Part 11 - Wrought Case Hardening steels

d - ISO 683-10 - Heat-treated Steels, alloy steels and free-cutting steel Part 1 - Quenched and tempered unalloyed steels

e - ISO 683-1, ISO683-10, or ISO 683-11

Steel Quality

The Steel Quality Standards are:

ML - Modest demands on the material quality and the heat treatment process

MQ - Material Quality and Heat-Treatment standards met by experienced manufacturer.

ME - High degree of reliability of Material Quality and Heat-Treatment process.

The requirements to be met for different steel qualities include: Chemical Analysis, Melting Practice, Surface Crack Detection after machining, and Hardness must be measured. Sometimes, to confirm the analysis a test piece is prepared and heat-treated together with cam - See ISO 3663-5.

Enter a Hardness value in the HB, HV, or HRC hardness scale - see image above

The default Hardness is the average of the Upper and Lower Hardness Limits

The Hardness you enter must be within the Upper Hardness Limit and Lower Hardness Limit. The limits are specified in ISO 6336-5.

Lower H Limit ≤ Actual Hardness (HB, HV, HRC) ≤ Upper H Limit

In the example above, you can enter a Hardness in the range of 175-300HB, 178-315HV, or 9-32HRC.

When you enter a Hardness value under one of the Hardness Scales, the other two Hardness Scales update automatically.

The Orange Separator indicates the Flank, Steel Category, Steel Quality, Heat-Treatment Type and/or Steel-Type with Steel Acronym are indicated in the separator.

E.G:  Inner Flank: 004 ML Nodular / Ductile / Spherical Cast Iron (GGG) 

Flank : Inner

Steel Category : 004

Steel Quality : ML

Steel Name : Nodular / Ductile / Spherical Cast Iron

Steel Acronym : GGG

The Results are:

Maximum Contact Stress (MPa - Mega-Pascals)

When you select the Follower-Roller - see Roller-Life tab - we can use the combined Geometry and Materials of the Cam and the Follower-Roller to calculate the maximum contact-stress.

Maximum Dynamic Contact-Stress - (MPa - Mega-Pascals)

Maximum Contact-Stress × Safety Factor - see Parameters tab > Enable Lifetime, Edit Safety-Factor

Maximum Allowable Contact Stress

A property of the Steel-Category, Heat-Treatment, and Steel Quality that you select, together with the Surface Hardness that you enter - see above Cam Materials and Hardness

Dynamic / Allowable (-)

Ratio of Maximum Dynamic Contact-Stress : Maximum Allowable Contact Stress.

We apply the ratio to the Y-axis on the plot of Life(X-axis) vs Ratio of Dynamic/Allowable(Y-axis) - see plot below. Each Steel Category has a different plot.

Depth of Max Shear Stress (mm)

The Maximum Shear-Stress is below the surface. The Depth of Maximum Shear-Stress is a function of the size and shape of the contact between the Follower-Roller and Cam-Profile.

Recommended: Minimum Depth of Surface-Hardness > ~2 × Depth of Maximum Shear-Stress.

Maximum Shear Stress

Approximately 0.78 x Maximum Contact-Stress (depending on the contact geometry).

Dynamic Shear-Stress

Maximum Shear-Stress x Safety-Factor - see Parameters tab > Enable Lifetime, Edit Safety-Factor

S-N (Log-Log) Curves for different Steel Categories (based on ISO 6336)
Y-axis = Maximum Dynamic Contact-Stress/Allowable Contact-Stress of Steel, Quality, Hardness
X-axis = Life in Number of Machine-Cycles

Y (in graph below) = Maximum Dynamic Contact Stress Allowable Contact Stress

When Y=1, Cam Lifetime = 1.

1 Life of Steel-Categories 1: 1.0 × 10^9 cycles,

1 Life of Steel-Categories 2: 1.5 × 10^7cycles;

1 Life of Steel Categories 4: 5.0 × 10^6 cycles

1 Life of Steel Categories 4: 5.0 × 10^6 cycles

When Y > 1, Cam Lifetime is reduced.

When Y < 0.85, Cam-Lifetime is infinite (Greater than 10^10 cycles)

When Life < 10^5 cycles, Contact-Stress plays a more important role, also, ratcheting and shakedown stress.

Cam-Life, N (Millions of Cam Rotations)

Millions of Cycles, 99% reliability.

Maximum - 10,000,000,000 (1010 rotations / 10 billion)

Cam-Life, Hrs.

Number of Hours, based on Millions of Cam-Life Rotations and Machine Speed (RPM).

Cam-Life, Yrs.

Number of Years, based on 8760 hours per year.