General Tribology

All of the below functions can be found in the tribology module of the package.

The functions in this module are related to tribology in general.

fball3plates(ax_force, plate_angle=1.5708)

Calculate the normal force per contact in ball-on-3-plates setup.

Parameters:

• ax_force (ndarray, scalar) – The force acting along the rotational axis of the ball (axial force).
• plate_angle (ndarray, scalar, optional) – The plate angle in radians, measured with respect to the rotational axis of the ball. Default value corresponds to 45 degree.

Returns:

The normal force acting in each ball-plate contact.

Return type:

norm_force

ffourball(r_1, r_2, ax_force)

Calculate the normal force per contact in a 4-ball test setup.

Parameters:

• r_1 – The radius of the rotating ball.
• r_2 – The radius of the stationary balls.
• ax_force – The force acting along the rotational axis of the rotating ball.

Returns:

norm_force – The normal force in a single ball-ball contact.

Return type:

ndarray, scalar

gfourball(r_1, r_2)

Geometric parameters of 4-ball setup

Parameters:

• r_1 (scalar) – The radius of the rotating ball.
• r_2 (scalar) – The radius of the (a) stationary ball.

Returns:

• sliding_radius (scalar) – The sliding radius (lever arm) on the rotating ball.
• contact_angle (scalar) – Contact angle between direction of ball normal force and vertical axis.

profball(x_axis, r_ball)

Create a 1D ball profile along a central axis.

Parameters:

• x_axis (ndarray) – The coordinate points for which to calculate profile heights. Minimum and maximum value must be within +/- r_ball.
• r_ball (scalar) – The radius of the ball.

Returns:

prof_heights – The profile heights along the x_axis.

Return type:

ndarray

profrevolve(prof_1d, y_axis, y_diam)

Create a 2D surface (profile heights) by revolving a 1D profile around a central axis.

Parameters:

• prof_1d (ndarray) – The profile heights along the central (x) axis of the surface.
• y_axis (ndarray) – The y-axis of the surface.
• y_diam (scalar) – The maximum diameter of the surface along its y-axis.

Returns:

• prof_2d (ndarray) – The surface heights of the profile. The array size is len(prof_2d) \(\times\) len(y_axis)
• y_profile (ndarray) – The profile heights along the y-direction of the surface at the central element of the x-axis.

profrolleriso(x_axis, diam, length)

Generate a roller profile according to DIN 26281 for rollers with length \(\leq\) 2.5 \(\cdot\) diam.

Parameters:

• x_axis (ndarray) – The x-axis of the roller. The origin of the axis must be at the center of the roller. To obtain sensible results, the axis limits must be within +/- length / 2.
• diam (scalar) – The diameter of the roller.
• length (scalar) – The length of the roller.

Returns:

x_profile – The profile heights of the roller along x_axis.

Return type:

ndarray

radpersec2rpm(vel_rad_per_sec)

Convert velocity from rotations per minute (rpm) to radians per second (rad/s).

Parameters:vel_rad_per_sec (ndarray, scalar) – The velcity in radians per second. Returns:vel_rpm – The velocity in rotations per minute. Return type:ndarray, scalar

rball3plates(r_ball, plate_angle=1.5708)

Calculate the sliding radius (lever arm) for a ball-on-3-plates test setup.

Parameters:

• r_ball (ndarray, scalar) – The radius of the ball.
• plate_angle (ndarray, scalar, optional) – The plate angle in radians, measured with respect to the rotational axis of the ball. Default value corresponds to 45 degree.

Returns:

r_slide – The sliding radius.

Return type:

ndarray, scalar

refix(val, p_in='', p_out='')

Convert between different SI unit prefixes. Available options are:

'T' Terra

'G' Giga

'M' Mega

'k' Kilo

'm' Milli

'mu' Micro

'n' Nano

'p' Pico

Parameters:

• val (scalar) – The value for which to convert the unit prefix.
• p_in (string, any of the above, optional) – The current prefix of val. If p_in is undefined, val has no SI unit prefix.
• p_out (string, any of the above, optional) – The prefix of val_refix after the conversion. If p_in is undefined, val_refix has no SI unit prefix.

Returns:

val_refix – The value in units of prefix p_out.

Return type:

scalar

rpm2radpersec(vel_rpm)

Convert velocity from radians per second (rad/s) to rotations per minute (rpm).

Parameters:vel_rpm (ndarray, scalar) – The velcity in rotations per minute. Returns:vel_rad_per_sec – The velocity in radians per second. Return type:ndarray, scalar

srr(vel_1, vel_2)

Calculate the slide-to-roll ratio (SRR) in a tribological contact based on contact body velocities.

Parameters:

• vel_1 (ndarray, scalar) – The contact velocity of body 1.
• vel_2 (ndarray, scalar) – The contact velocity of body 2

Returns:

srr – The slide-to-roll ratio in the tribological contact.

Return type:

ndarray, scalar

vroll(vel_1, vel_2)

Calculate the rolling speed in a tribological contact based on contact body velocities.

Parameters:

• vel_1 (ndarray, scalar) – The contact velocity of body 1.
• vel_2 (ndarray, scalar) – The contact velocity of body 2

Returns:

vel_roll – The rolling velocity in the tribological contact.

Return type:

ndarray, scalar

vslide(vel_1, vel_2)

Calculate the sliding speed in a tribological contact based on contact body velocities.

Parameters:

• vel_1 (ndarray, scalar) – The contact velocity of body 1.
• vel_2 (ndarray, scalar) – The contact velocity of body 2

Returns:

vel_slide – The sliding velocity in the tribological contact.

Return type:

ndarray, scalar