Fig。10: Human Model of Grinding Work

Static Strength Analysis

Calculation results of static strength for each grinding posture are shown in Fig。11, which also denotes the percent capable (P。C。) for torque on joints。 In the squat posture (Squat-L, Squat-H, and Squat-U), P。C。 reaches 90% on the knee, however, the postures of Stoop, Standing-H, and Standing-U are 100 %。 On the other hand, P。C。 of the posture of Standing-O reaches 70% on trunk。 Though bending or twisting posture is often seen on-site, it is understood that the Standing-O posture is hard to maintain during continuous work。

Energy Expenditure Analysis

Energy expenditure calculation for grinding work was carried out for three groups;

Squat-L Squat-H Squat-U Stoop Standing-H Standing-U Standing-O

Posture

Fig。11: Results of Static Strength Calculation

Squat Stoop Standing

Fig。12: Calculated Energy Expenditures

Squat posture: Squat-L, Squat-H, and Squat-U Stoop posture: Stoop

Standing posture: Standing-H, Standing-U,

Standing-O

Lifting Work

Static Strength Analysis

The calculation results are shown in  Fig。14。 The percent capable decreases gradually in accordance with increase of hand load。 Knee load is most severe; 50％ for 50kgf hand loads。 Hip and trunk loads are more severe; 70％ for 50kgf hand loads。

For these calculations, 5 minutes are assumed to be one cycle which includes grinding work of 3 minutes and moving time of 2 minutes。 The calculation results are shown in Fig。12。

The energy expenditures calculated are 2。67 kcal/min for squat, 2。63kcal/min for stoop, and 2。49kcal/min for standing。 The allowable values were also calculated as 2。72kcal/min for 8 hours and 3。11kcal/min for 4 hours。 Though the values of squat and stoop are close to the allowable value for 8 hours of 2。72kcal/min, the energy expenditure for all postures was lower than the allowable value for 4 hours。 Hence, there does not seem to accumulate physical fatigue during grinding, if sufficient rest is taken in a half day (for 4 hours)。

Human Model

Though there are many hard physical tasks in shipbuilding such as lifting, carrying, pushing etc。, lifting work was studied here。 The human model is shown in Fig。13 and this posture referred to as squat lifting where the knee is bent during the lift。 Hand loads from 0 to 50 kgf are considered。

10 20 30 40 50 60

Hand load (kg)

Fig。14: Percent Capable of Torque for Lifting

Energy Expenditure Analysis

Calculations of energy expenditure were carried out for

0。1 minutes, lifting from ground level to 800mm height。 Calculation results are shown in Fig。15。 Since the allowable value of energy expenditure was  calculated as 8。245kca/min, 25kgf is taken as the corresponding the hand load。 On the other hand, it is said 5。2 cal/min for continuous work (Garg, 1978)。 Therefore, it is recommended that the allowable lifting weight be 25 kgf for short duration and 10kg for continuous work。

Conclusions

This paper described the importance  of simulation based production as a part of digital  manufacturing after the application of CIM system  in shipbuilding, and introduced some examples of work analysis using a human simulation。