Influence of handle shape and size to reduce the hand-arm vibration discomfort

Abstract

Background:
Non-automated tool handles transmit a large magnitude of vibration to operators' hands, causing discomfort and pain. Therefore, the need for a better handle design is a matter of prime concern to overcome musculoskeletal disorders such as hand-arm vibration syndrome.

Objective:
This study aimed to examine the influence of handle shapes in reducing the transmission of hand-arm vibration.

Methods:
Seven different handles were designed and fabricated using 3D printing technology at the SSN College of Engineering, with consideration for the anatomical shape of the hand. The frequency-weighted Root Mean Square (RMS) values of the vibration levels transmitted were recorded at the wrist of twelve subjects, unaffected by musculoskeletal disorders. Subjective ratings of vibration and comfort perception were measured using the Borg Scale of Perceived Exertion.

Results:
The total vibration value (ahv) of each of the six novel prototype handles (B-G) was compared to that of the reference handle denoted handle-A. The vibration reductions for handles B to G respectively were 0.542 m/s2 (14.59%), 0.481 m/s2 (12.95%), 0.351 m/s2 (9.45%), 0.270 m/s2 (7.27%), 0.407 m/s2 (10.96%) and 0.192 m/s2 (5.17%).

Conclusions:
A significant level of vibration reduction was achieved by the prototype handles. Qualitative feedback from the study subjects suggests that they were not aware of the levels of vibration being transmitted to the hand with each handle.

Full text

Work xx (20xx) x–xx
DOI:10.3233/WOR-192948
IOS Press
1
Influence of handle shape and size to reduce
the hand-arm vibration discomfort
B. Jain A.R. Tony, M.S. Alphin∗and D. Velmurugan
Department of Mechanical Engineering, SSN College of Engineering, Chennai, India
Received 26 November 2017
Accepted 8 September 2018
Abstract.
BACKGROUND: Non-automated tool handles transmit a large magnitude of vibration to operators’ hands, causing dis-
comfort and pain. Therefore, the need for a better handle design is a matter of prime concern to overcome musculoskeletal
disorders such as hand-arm vibration syndrome.
OBJECTIVE: This study aimed to examine the influence of handle shapes in reducing the transmission of hand-arm vibration.
METHODS: Seven different handles were designed and fabricated using 3D printing technology at the SSN College of
Engineering, with consideration for the anatomical shape of the hand. The frequency-weighted Root Mean Square (RMS)
values of the vibration levels transmitted were recorded at the wrist of twelve subjects, unaffected by musculoskeletal
disorders. Subjective ratings of vibration and comfort perception were measured using the Borg Scale of Perceived Exertion.
RESULTS: The total vibration value (ahv) of each of the six novel prototype handles (B-G) was compared to that of the
reference handle denoted handle-A. The vibration reductions for handles B to G respectively were 0.542 m/s2(14.59%),
0.481 m/s2(12.95%), 0.351 m/s2(9.45%), 0.270 m/s2(7.27%), 0.407 m/s2(10.96%) and 0.192 m/s2(5.17%).
CONCLUSIONS: A significant level of vibration reduction was achieved by the prototype handles. Qualitative feedback
from the study subjects suggests that they were not aware of the levels of vibration being transmitted to the hand with each
handle.
Keywords: Hand-arm vibration syndrome, musculoskeletal disorders, hand-transmitted vibration, handle diameter, vibration
reduction, occupational ergonomics
1. Introduction
Hand-operated and semi-automated tools are
widely used in manufacturing industries. The hand-
arm vibration transmitted from vibrating tool handles
and equipment can cause workers to experience
discomfort and pain in the upper extremities [1]. Con-
tinuous, long-term occupational exposure can cause
workers to develop hand-arm vibration syndrome
(HAVS) and cumulative trauma disorders (CTDs)
associated with neurological, muscular, circulatory,
bone and joint consequences [2–4]. Vibration injury
∗Address for correspondence: M.S. Alphin, Department of
Mechanical Engineering, SSN College of Engineering, Chennai,
603 110, India. Tel.: +91 9884216480; E-mail: alphin@aol.in.
is a multidimensional problem that can affect every
aspect of an individual’s life (e.g. vibration white
finger, cumulative trauma disorders, etc.) [5]. The
European Union (2005) has characterized the expo-
sure limit value of 5.0 m/s2and exposure action value
of 2.5 m/s2for 8 hour working days.
Poor tool handle design can cause discomfort to
workers’ and result in early fatigue. Over time, this
may contribute to the development of physiolog-
ical and physical disorders [4]. Improved handle
design is essential to prevent unnecessarily grip
force, improper hand posture and fatigue. A maxi-
mum torque condition, the diameters of the handles
37–44 mm and 41–48 mm (23.3% of the user’s hand
length) have been recommended for females and
males respectively [6]. Shape [8], handle size [9],
1051-9815/19/$35.00 © 2019 – IOS Press and the authors. All rights reserved
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2B.J.A.R. Tony et al. / Influence of handle shape and size to reduce the vibration
texture [10] and surface type [11] are some fac-
tors to be considered for designing improved tool
handles. Handle size to maximize grip strength and
prevent stress on the tendons [12]. In order to reduce
the discomfort and pain associated with hand tool
use, optimum handle size and shape should be taken
into consideration for tool design [13]. An accurately
designed handle can improve workers’ safety, com-
fort and performance during work whilst preventing
the development of disorders [7]. Thus, designing
vibrating handles that can reduce vibration transmis-
sion is of interest.
Ergonomic analysis should be included in the
design phase because the main function of the product
and the form of the product are firmly interconnected
[15, 16]. Improved performance and reduced user
discomfort were found in studies where ergonomic
principles were considered at the industrial prod-
uct phase [14]. Tool-handle based Digital Human
Hand Model (DHHM) is a production technique that
accounts for the optimal-power grasp posture, in
order to mitigate the risk of cumulative trauma dis-
orders (CTD) and improve subjective comfort-rating
[17].
From a biomechanic perspective, the hand is very
complicated and flexible in structure [18]. Therefore,
it is important to understand the hand-arm response
to vibration during hand-tool design. The level of
vibration transmitted from a hand-tool to the opera-
tor’s arm is influenced by the operator’s posture, grip
force, push force and the bio-dynamic responses of
their fingers, hands and arms [19]. The bio-dynamic
response of the fingers to hand-arm vibration differs
from that dispersed to the palm of the hand [18]. Sev-
eral researchers have analyzed vibration transmitted
along the dominant direction (Zh-direction the mag-
nitude of vibration level found maximum) [20–23],
whereas experimental investigations have been con-
ducted to evaluate the magnitude of vibration total
values (ahv). Duration of vibration exposure has also
been considered by the researchers estimating the
vibration total values [24–26].
The acceleration peaks generated by vibrating
hand-tools are a contributing factor to the harmful
effects of vibration exposure. The vibration transmit-
ted to the upper extremities can be reduced with the
proper utilization of anti-vibration gloves [27–29] or
isolators (vibration damping isolators inserted at the
handle-machine interface) [30, 31]. The use of an air-
bladder glove or foam-padded glove can significantly
attenuate the hand-arm transmitted vibration, com-
pared to the individual’s bare hands [32]. In a study
of six anti-vibration interventions (five glove types
and a visco-elastic tool wrap), sheet assembly work-
ers’ that used the glove or wrap perceived a reduction
in vibration transmission compared to that perceived
by workers working bare-handed [33]. However, anti-
vibration gloves have been found to be less effective
for people with sizable hands (i.e. hand size in the
90th to 95th percentiles) exposed to vibration in the
frequency range of 50–100 Hz [18].
Another study, examined the effectiveness of
vibration isolators in the engine and the handle of
a tractor. Frequency-weighted Root Mean Square
(RMS) acceleration was reduced by 29.8% and the
subjective rating of arm soreness was reduced by
32%–61% when the vibration isolators were used
[31]. While anti-vibration gloves and isolators can
reduce vibration transmission and prevent hand-arm
vibration syndrome, their efficacies are limited by the
magnitude of vibration and frequency [34–37].
According to the hierarchy of controls, control-
ling vibration at the source by improving tool handle
design is optimal. The majority of the literature
focuses on the cylindrical and elliptical shape of tool
handles. However, the anatomical shape of the hand
has not been considered in tool handle designs. The
objectives of the present study are to (1) develop
ergonomic tool handles by considering the anatomi-
cal shape of the hand; (2) quantify hand-arm vibration
transmission from the prototype handles; and (3)
examine users’ perception of vibration and comfort
with the prototype.
2. Material and methods
2.1. Recruitment
Twelve males, 21 to 40 years of age, from the
SSN College of Engineering in Chennai, India, vol-
unteered to participate in this study. All subjects were
right-hand dominant, unaffected by musculoskeletal
conditions and had no remarkable medical history.
Each subject was provided a brief description of the
study procedure. Table 1 shows anthropometric mea-
surements of the study participants.
2.2. Reference handle diameter
The mathematical relationship between anthropo-
metric parameters such as grip force, handle diameter,
hand size and contact area were investigated [38].
Optimal tool handle diameter was achieved when the
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B.J.A.R. Tony et al. / Influence of handle shape and size to reduce the vibration 3
Table 1
Anthropometric characteristics of study participants
Characteristics Mean Standard deviation Range
Age (years) 31 6.78 22–40
Height (cm) 166 4.92 159–172
Weight (kg) 73 5.89 65–81
Middle finger length (mm) 190 4.86 180–194
Thumb finger length (mm) 112 4.66 106–120
Grip diameter∗(mm) 53 3.65 48–55
∗The diameter grip (Dgrip) is the maximum diameter that can be grasped by a subject
when the middle finger and the thumb finger are in contact.
middle fingertip and the thumb fingertip aligned par-
allel. The reference handle diameter was calculated
as 44 mm on the basis of the anthropometric grip
diameter (Dgrip) using Equation (1).
Dopt =Dgrip ×π(LF,2+LT)
2
π(1)
LF,2=0.14Lmiddle
LT=0.26Lthumb
where, Dgrip denotes grip diameter, Lmiddle denotes
wrist to middle fingertip length, Lthumb denotes
wrist to thumb fingertip length, LF,2 denotes the
middle fingertip length and LTdenotes thumb tip
length.
2.3. Mold preparation and 3D laser scanning
Considering the calculated optimal diameter of 44
mm and length of 120 mm, six different shaped molds
were designed using modeling software SOLID-
WORKS 2016®(Fig. 1). The design patterns were
made from polypropylene material and manufactured
by the Computer Numerical Control (CNC) milling
machine. Alginate impression material was used to
obtain the shape of the molds. One subject was asked
to hold the alginate impression material in order to
examine the anatomical shape of their hand while the
middle of the middle fingertip and thumb fingertip lay
along a line parallel to the longitudinal axis (Fig. 2).
Three Dimensional (3D) laser scanning was used to
produce 3D models for each of the six alginate models
with hand impressions (Fig. 3).
2.4. Segmentation and 3D construction
The images obtained from the 3D laser scanner
were imported to the modeling software SOLID-
WORKS 2016®for further segmentation and
Fig. 1. Top view of six different shape molds for handles B–G.
Fig. 2. Alginate impression material used to consider the anatom-
ical shape of the hand.
construction. Feature recognition technique was used
to identify small inclusions, segmentation errors,
holes and ribs. Surface smoothening was performed
using 3D reconstruction technique (Fig. 4).
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4B.J.A.R. Tony et al. / Influence of handle shape and size to reduce the vibration
Fig. 3. 3D scanned image of the alginate impression model in
STereoLithography (STL) format.
Fig. 4. Smooth 3D representation of handle in STereoLithography
(STL) format.
2.5. Tool handles prototyping
Tool handle prototypes were made out of white
Acrylonitrile Butadiene Styrene (ABS) plastic with a
smooth surface finish, using a 3D printer (Fig. 5).
A detailed description of the prototype handles is
provided in Table 2. A cylinder-shaped handle (the
reference handle) was manufactured by the same pro-
cess but without consideration of hand impression
(diameter of 44 mm and length of 120 mm). Vibration
transmission and comfort were compared between
this handle and the prototype handles.
2.6. Hand-arm vibration measurements
Hand-arm vibration was measured using a tri-
axial accelerometer (Kistler, 8763), electrodynamic
exciter (Dongling, ESD045) and data acquisition sys-
tem (DAQ with dynamic analyzer, 9234) through a
NI USB-9234 card to Lenovo laptop (Core 2 duo Pro-
cessor based). Vibration levels were analyzed in all
directions (Xh,Y
hand Zh) with a sampling rate
of 2048 frames per second using DEWESOFT soft-
ware (Version X2). The coordinate axes used were
in accordance with ISO 5349-1086. The NIOSH
(1989) [40] recommendation is that the weight of the
accelerometer be less than 5 g and the total weight
of the accelerometer and adapter be less than 20 g
[39, 40]. The accelerometer used in the present study
weighed 2.4 g and was attached to subjects’ wrists
using a light-weight strip in compliance with ISO
5349-2 (Fig. 6). Further details of the experimen-
tal setup and measurement process are, re-described
in Fig. 6.
2.7. Experimental procedure
Vibration transmitted from the tool handle to the
operator’s wrist, positioned upright, with the elbow
bent at 90◦angle, was measured. The fixture used
to attach the handles to the vibration exciter was
designed to eliminate any interruption (disturbance
from the base of the shaker). The exciter was set
to the frequency range of 0–1000 Hz. Subjects were
instructed to grip the handle with constant force. The
experiment was initiated once the subject attained
the correct posture. The accelerometer was calibrated
according to the ISO 16063-21, 2003 and ISO 5347-
14, 1993.
2.8. Data analysis
Results were uploaded to a spreadsheet and pro-
cessed using the IBM SPSS Statistics 20 software®
package. The data was analyzed for vibration accel-
eration in RMS at 1/3 octave band frequency in the
range of 4–1000 Hz for each trial, in accordance
with the ISO 5349-2 (2001), and Frequency-weighted
RMS acceleration (ahwx,a
hwy and ahwz) was calcu-
lated for each axis. For each subject, the average
of two trials was calculated. The vibration total
value (ahv) was evaluated for each subject using
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B.J.A.R. Tony et al. / Influence of handle shape and size to reduce the vibration 5
Fig. 5. Different types of prototype handle attached with the fixture.
Table 2
Types of handle designs
Handle name Shape Description
Handle A Cylindrical Without considering anatomical shape of hand
Handle B Cylindrical Considering anatomical shape of hand
Handle C Elliptical Considering anatomical shape of hand
Handle D Hexagonal Considering anatomical shape of hand
Handle E Pentagonal Considering anatomical shape of hand
Handle F Semi-triangular Considering anatomical shape of hand
Handle G Triangular Considering anatomical shape of hand
the frequency-weighted RMS vibration accelera-
tion of the axes. The average vibration acceleration
across all subjects was calculated. The average vibra-
tion total value (ahv) of each individual prototype
handle was subtracted from the ahv of the refer-
ence handle to determine the reduction in vibration
achieved.
Subjects rested their arms for a period of time (15
minutes) between the trails. During the rest period,
the subjects were asked to rate the handle based
on their perception of comfort, specifically, ease of
holding the tool, and vibration. Subjective scores
were computed using the Borg Scale of Perceived
Exertion (CR-10) [41]. The CR-10 scale assessed
the perception of intensity as a 10-point linear-scale
from 0 (very comfortable to hold/no vibration) to
10 (very uncomfortable to hold/maximum vibra-
tion). The difference in frequency-weighted RMS
acceleration and vibration of each prototype han-
dle compared to handle A, was calculated using
a one-way analysis of variance (ANOVA) and
t-test.
3. Results and discussion
The vibration transmitted to the subjects’ wrists
was recorded in the Xh,Y
hand Zhdirections at a
frequency 0–1000 Hz and a sample rate of 2048 per
second (Figs. 7-8). Figure 7 shows the relationship
Fig. 6. Experimental setup for vibration measurements at the wrist
of the participant.
between time and amplitude and Fig. 8 shows the
relationship between frequency and acceleration.
3.1. Frequency un-weighted analysis
The vibration RMS acceleration without frequency
weighting, measured for each handle in the Xh,Y
h,
and Zh-axes, is reported in Fig. 9. Figure 9a–9c
shows that all the handles’ vibration responses follow
identical patterns. Their resonance frequencies were
10 Hz, 20 Hz and 31.5 Hz. In the Xh-axis (Fig. 9a), the
peak accelerations, at a frequency of 10 Hz, for han-
dles A–E respectively were: 26.02 m/s2, 13.26 m/s2,
16.68 m/s2, 23.42 m/s2, 30.54 m/s2, and 22.94 m/s2
for handles F and G. The peak acceleration was at a
maximum for handle E and minimum for handle B.
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6B.J.A.R. Tony et al. / Influence of handle shape and size to reduce the vibration
Fig. 7. Sample graph between amplitude and time.
In the Yh-axis the peak vibration acceleration
was observed at a frequency of 10 Hz for all
the handles, with the exception of handle B, that
was31.5 Hz (Fig. 9b). The peak accelerations for han-
dles A-G respectively were: 14.03 m/s2, 11.98 m/s2,
12.45 m/s2, 23.04 m/s2, 13.42 m/s2, 17.91 m/s2and
17.48 m/s2.
Figure 9c shows the peak vibration acceleration for
all handles in the Zh-axis at a frequency of 10 Hz.
The peak accelerations for handles A–G respec-
tively were: 34.68 m/s2, 29.28 m/s2, 30.36 m/s2,
27.22 m/s2, 26.66 m/s2, 29.98 m/s2and 33.18 m/s2.
Dewagan KN (2009) studied the relationship
between un-weighted vibration acceleration and fre-
quency in the Xh,Y
hand Zh-axes in different
hand-tractor transporting conditions [42]. The reso-
nance frequencies of un-weighted RMS accelerations
were found to be 10 Hz, 20 Hz and 31.5 Hz in all the
three axes, similar to the findings from the present
study. In a study of grass trimmer prototype handles,
the frequency of un-weighted RMS peak acceleration
was observed at 80 Hz, because the hand grip was not
considered [43].
3.2. Frequency-weighted analysis
In order to identify the frequencies associated
with injury to the hand-arm system, the frequency
weighted RMS acceleration (ahwx,a
hwy and ahwz)
was calculated for the handles using the filter recom-
mended by the ISO 5349-2 (2001). The frequency
weighted RMS acceleration observed in the Xh,Y
h,
and Zh-axes was 10 Hz (Fig. 10).
In the Xh-axis the peak accelerations for handles
A-G respectively were: 24.70 m/s2, 12.62 m/s2,
15.94 m/s2, 22.32 m/s2, 29 m/s2, 21.80 m/s2and
21.84 m/s2(Fig. 10a). In the Yh-axis, the peak
accelerations for handles A–G respectively were:
13.37 m/s2, 11.43 m/s2, 11.88 m/s2, 22 m/s2,
12.74 m/s2, 17.02 m/s2and 16.66 m/s2(Fig. 10b).
In the Zh-axis (Fig. 10c), the peak accelerations
for handles A–G respectively were: 33.06 m/s2,
27.98 m/s2, 28.94 m/s2, 25.92 m/s2, 25.36 m/s2,
28.52 m/s2and 31.6 m/s2.
The maximum frequency-weighted vibration
acceleration was observed in the Zh-axis, the dom-
inant direction, followed by the Xhand Yh-axes.
The results from studies on the use of coating over
drilling machine handles also found the dominant
direction to be the Zh-axis followed by Xhand Yh-
axes [23]. Figure 10 demonstrates how handles had a
higher magnitude of vibration acceleration at lower
frequency. A similar response was obtained across
tractor handle and grass trimmer handles studies
where higher magnitudes of vibration acceleration
were observed at lower frequencies and lower mag-
nitudes of vibration at higher frequencies [42, 43].
3.3. Vibration total value (ahv) analysis
The vibration total value ahv, being the amalga-
mation of vibration in all three translational axes,
was determined according to ISO 5349-2, 2001, [44,
45]. The mean and standard deviation of frequency-
weighted RMS acceleration is presented in Table 3.
The average acceleration for handle A in the Zh-axis
was 16.6%; this was 37.4% higher than the Xhand
Yh-axes. Similarly, the average acceleration for han-
dle B in the Zh-axis was 24%, 28.6% higher than
the Xhand Yh-axes. The average accelerations in the
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B.J.A.R. Tony et al. / Influence of handle shape and size to reduce the vibration 7
Fig. 8. Sample frequency spectra measured in the Xh,Y
hand Zh
axes at the wrist of the subject.
Zh-axis for handles C-G respectively were: 32.2%,
40% 27.7%, 58.2%, 7.6%, and 3.2%. The vibration
acceleration across the Xh,Y
h,Z
haxes was sig-
nificant at the 1% level for handle A. Of all the
prototypes, handle B produced the lowest vibration
total value, followed by C, F, D, E and G.
3.4. Vibration reduction analysis
Reduction in vibration was calculated as the
difference between the vibration total value of han-
dle A and the vibration total values of handles
B through G. Vibration total value was signifi-
cantly reduced (p< 0.01) for all 6 prototype handles
(Table 4). Table 5 shows the percentage of vibra-
tion acceleration reduced by the prototype handles,
in the Xh,X
hand Zh-axes. The reduced vibration
total value for handles B through G respectively
were: 0.542 m/s2(14.59%), 0.481 m/s2(12.95%),
0.351 m/s2(9.45%), 0.270 m/s2(7.27%), 0.407 m/s2
(10.96%) and 0.192 m/s2(5.17%) (Table 5).
3.5. Subjective rating
The subjective rating of comfort and perception
of vibration were measured using the Borg Scale of
Perceived Exertion (Table 6) [46]. The perception of
comfort was highest for handle A followed by han-
dle D, B, C, E, F and G (Table 6). There was no
correlation between the comfort ratings and levels of
vibration measured (Table 3). Vibration perception
was highest (3.4), for the handle perceived as most
comfortable, handle A. The subjective comfort rating
reflected grip-diameter size.
The vibration perception for handle C, D and F
respectively, was 3.2, 3.0, and 2.4. While handle G
had the highest vibration total value (ahv), it was
perceived to have the lowest vibration. The data elu-
cidates operators’ lack of awareness to the levels of
hand-arm vibration being transmitted to their upper-
extremity; this is consistent with the literature [43,
47].
3.6. Study limitations
This study did have certain limitations. The pro-
totype handle shapes can be effectively influenced
in the bare hand operations. However, the shapes of
the handles can’t be influenced in gloved hand opera-
tions. The prototype handles were fabricated for 50th
percentile people though it is not suitable for 5th per-
centile and 95th percentile people because of hand
size variations. The contribution of finger force were
not considered in this study and the future studies
should examine the finger forces using the prototype
handles developed in this study.
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8B.J.A.R. Tony et al. / Influence of handle shape and size to reduce the vibration
Fig. 9. Frequency un-weighted vibration acceleration (RMS) for seven different types of handle design in different axes: (a) Xh-axis, (b)
Yh-axis, (c) Zh-axis.
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B.J.A.R. Tony et al. / Influence of handle shape and size to reduce the vibration 9
Fig. 10. Frequency weighted vibration acceleration (RMS) for seven different type handle design in different axes: (a) Xh-axis, (b) Yh-axis,
(c) Zh-axis.
4. Conclusions
Tool handle design influences factors including the
shape, size, and perceived comfort by the tool oper-
ator, as well as the amount of vibration transmitted
to the hand. Improvements in tool comfort can be
achieved by considering the anatomy of the hand
during handle development. Our prototype Handle
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10 B.J.A.R. Tony et al. / Influence of handle shape and size to reduce the vibration
Fig. 11. Vibration acceleration reduction for each axis and vibration total value (ahv) compared with reference handle A.
Table 3
Weighted vibration acceleration (RMS) by axis (ahwx,a
hwy and ahwz), vibration total value (ahv ) and ANOVA analysis for handles A–G
Handle Vibration acceleration (RMS), m/s2a
hv (mean ANOVA Values
(mean standard deviation) standard
Xh-axis Yh-axis Zh-axis deviation) XhVs YhXhVs ZhYhVs Zh
A 2.101 (0.550) 1.576 (0.080) 2.519 (0.609) 3.713 (0.824) 0.525∗–0.418∗–0.943∗
B 1.604 (0.495) 1.507 (0.188) 2.113 (0.365) 3.171 (0.643) 0.097 –0.509 –0.606
C 1.691 (0.308) 1.017 (0.069) 2.495 (0.286) 3.232 (0.425) 0.674 –0.804 –1.478
D 2.015 (0.345) 1.604 (0.118) 2.115 (0.362) 3.362 (0.513) 0.411 –0.1 –0.511
E 1.893 (0.264) 1.094 (0.288) 2.620 (0.207) 3.443 (0.442) 0.799 –0.727 –1.526
F 2.002 (0.451) 1.426 (0.113) 2.168 (0.479) 3.306 (0.667) 0.576∗–0.166∗–0.742
G 2.190 (0.621) 1.396 (0.215) 2.263 (0.598) 3.521 (0.888) 0.794 –0.073 –0.867
∗Significant (p< 0.01).
Table 4
T-test values associated with the difference in vibration acceleration
between handle A and prototype handles B–G
Combined differences t-values
between handles Xh-axis Yh-axis Zh-axis ahv
A-B 1.325∗0.478∗1.676∗1.300∗
A–C 1.482 3.083 0.130 1.504
A–D 0.563∗–0.223∗1.563 1.611∗
A–E 2.628 3.279 –1.860 1.972
A–F 1.233∗0.926 1.944 2.297
A–G –1.037 1.011 2.622 1.538
∗Significant (p< 0.01).
Table 5
Percentage of vibration acceleration reduction between handle A and prototype handles B–G
Handle Xh-axis Yh-axis Zh-axis ahv
B 0.497 (23.7%) 0.069 (4.37%) 0.406 (16.12%) 0.542 (14.59%)
C 0.410 (19.51%) 0.559 (35.46%) 0.024 (0.95%) 0.481 (12.95%)
D 0.086 (4.09%) –0.028 (–1.77%) 0.044 (16.03%) 0.351 (9.45%)
E 0.208 (9.90%) 0.482 (30.58%) –0.101 (–4.01%) 0.270 (7.27%)
F 0.099 (4.71%) 0.150 (9.51%) 0.351 (10.96%) 0.407 (10.96%)
G –0.089 (–4.23%) 0.180 (11.42%) 0.256 (10.16%) 0.192 (5.17%)
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B.J.A.R. Tony et al. / Influence of handle shape and size to reduce the vibration 11
Table 6
Subjective ratings of comfort perception and
vibration perception
Handle Borg’s Scale of Perceived Exertion
(Standard Deviation)
Comfort Vibration
perception perception
A 5.6 (1.342) 3.4 (0.548)
B 3.8 (0.837) 2.8 (1.304)
C 3.6 (1.342) 3.2 (0.837)
D 4.2 (0.837) 3.0 (0.707)
E 2.8 (0.837) 2.8 (0.837)
F 1.6 (0.548) 2.4 (1.140)
G 1.0 (0.612) 1.5 (1.000)
B, was found to have transmitted the lowest vibra-
tion total value (ahv) of all the prototype handles.
Improved vibration control at the tool level would
be useful for the prevention of hand-arm vibration
syndrome seeing as tool operators are unable to per-
ceive the relative level of vibration being transmitted
to their hands.
Acknowledgments
The authors wish to extend sincere thanks to all
the subjects who have participated in this research.
This research work was supported by the grant of
Department of Science and Technology (DST, India)
Reference No. YSS/2014/000715.
Conflict of interest
None to report.
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Corrected Proof