The aim of the experiment was to determine porosity of the sleeve of a self-lubricating bearing, saturate the sleeve with oil. Beside this we checked the way of mounting the sliding bearing and calculated the change of torque in the first ten minutes of operation of such a bearing.

The measurements of dimensions of sleeves were done carefully, with use of laboratory, analytical balance, calibrating mandrel, inner and outer diameter gauges etc.

Following the instruction, we put the dry, new sleeve inside the vacuum dryer. Simultaneously the other members of group remounted old sleeve and assembled new one, saturated with oil. Then the engine of wearing-in stand was switched on and the measurements were taken.

TABLE 7.1

Measured quantities	[kg]	Calculated quantities			Errors
Q1	0,06452	ρv	5246,855	[kg/m3]	Δρv	2,77E-7
Q2	0,0632	Qol	-0,00132	[kg]	ΔQol	0,014142136
Q3	0,05305	Po	-0,12198		ΔPo	0,0000551
Q4	0,00211	Pc	0,331611		ΔPc	0,000359

mass of dry sleeve (before saturating it with oil)

mass of sleeve after saturating with oil

mass of sleeve saturated with oil, along with the wire, submerged in water

mass of wire whose one end (shaped as loop) is immersed in water

- mass density of sintered material

- oil penetrated into it's pores

- active porosity

- total porosity

V - sleeve volume

volume of open pores

total volume of pores

mass density of the water (takes
)

mass density of oil used to saturate sleeve

- oil density as a function of temperature

mass density of iron (takes
)

TABLE 7.2 (if not marked different, all units in mm)

Measured quantities	The orientation of the measuring device				Average value	RMS Error
		0^o	45^o	90^o			135^o
	Do	35,99	35,99	35,988			35,99	35,9135	0,001446
		35,99	35,988	35,987			35,99
		35,988	35,987	35,986			35,988
Dp	36,06		36,054		36,057	0,0004226
Negative allowance	Dp-Do=	0,1435
dp	25		25		25	0
dc	24,8	24,85	24,9	24,85	24,79583	0,062006
		24,8	24,75	24,8			24,85
		24,8	24,75	24,7			24,7
Clearance	dp-dc=	0,20417

diameter of the holder's seating hole

outer diameter of the sleeve

diameter of sleeve's hole after calibration

diameter of the journal

- root mean square

- avarage value

TABLE 7.3

Rotational velocity ω = 152,1/s					Circumferential speed U =2,66175 m/s
Weight mass Q = 1,13kg					Mean pressure p = 0,105955 N/mm^2
Temperature at the beginning T0 = 23,5°C
No.	Time t [min]	Measured quantities		Calculated values
				G[g]	T[°C]	M [Nm]	M [Nm]			 [MPas] ∙10^-8	
1	0	305	29	0,186	0,004266222	0,133756317	1,62245E-05	1,27414	2,9125E-06
2	2	275	25	0,167	0,004065236	0,120599958	1,46362E-05	1,59714	3,6508E-06
3	4	270	37	0,164	0,004032853	0,118407232	1,43726E-05	0,879334	2,01E-06
4	6	275	40	0,167	0,004065236	0,120599958	1,46362E-05	0,780929	1,7851E-06
5	8	280	42	0,170	0,004097951	0,122792685	1,49001E-05	0,725028	1,6573E-06

- circumferential speed

- mean pressure

- torque of resistance to motion In self lubricating bearing

friction coefficient

Hersey's numer In dimensionless form

- actual load bearing

i =6,95- lever ratio of loading system

mass of holder together with lever system and pan, reduced to bearing axis

d=36mm -nominal diameter of bearing

L=20,2mm - length of sleeve

G - mass indicated by the balance

l - length of lever arm

ERROR ANALYSIS

ρ_wd=0,997 ±0,0003g/cm³

ρ_Fe=7,850 g/cm³±0,003g/cm³

ρ_ol=0,899 g/cm³-0,00075[g/(cm³∙ ^oC)] ∙T[^oC] ± 0,01g/cm³

The measured values are:

T=29 ±0,1 ^oC

Q₁=64,52±0,01g

Q₂=63,2±0,01g

Q₃=53,05±0,01g

Q₄=2,11±0,01g

We assume the certainty level of α_p=0,9973 for all errors (Δ) which is equivalent to the interval [±3σ].

Thus the errors are:

Δρ_v=3∙σ(ρ_v)

ΔQ_ol=3∙σ(Q_ol)

ΔP_o=3∙σ(P_o)

ΔP_c=3∙σ(P_c)

The standard deviations of the respective quantities are expressed as:

The relations between the measured quantities:

Having calculated the partial derivatives, we express the respective standard deviations as:

σ(ρ_wd)=Δρ_wd/3=0,0001g/cm³

σ(ρ_Fe)= Δρ_Fe/3=0,001g/cm³

σ(ρ_ol)= Δρ_ol/3=0,00333g/cm³

σ(Q_i)= σ(Q)= ΔQ_i/3=0,00333g

In the same way we calculate the errors of resistance torque and coefficient of friction:

Variances:

Derivatives:

Standard deviations:

Conclusions

In first part of our experiment, we didn't turn on the outlet from our dryer. By mistake we didn't close the inlet valve, and open the vent valve, so when we start the vacuum pipe, whe didn't have the pressure drop. By that our sleeve wasn't saturated, and the first part of our experiment was failed. In the second part we didn't cool down the sleeve to the ambient temperature, so on the beginning we have higher temperature, and viscosity, that in the next measure, but in the next steps, the results seems like good.

7

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