Siddhartha Saha

Bio: Siddhartha Saha is an academic researcher from Baba Banda Singh Bahadur Engineering College. The author has contributed to research in topics: Transmissibility (structural dynamics) & Vibration white finger. The author has an hindex of 1, co-authored 2 publications receiving 3 citations.

A review on hand-arm vibration exposure and vibration transmissibility from power hand tools to hand-arm system

Abstract: In the last few decades, a large number of studies have been carried out on vibration exposure and its transmissibility from the handle of a powered hand tool to the hands of the operator. Vascular, neurological and musculoskeletal disorders which Manifest as hand-arm vibration syndrome are commonly observed amongst workers in MSME sector and, therefore, its study assumes importance. This review article is a compilation of the work done by various researchers in the area of hand-arm vibration exposure. Measurement of vibration exposure along with their limits as given in international standards is reported. Different methods of vibration transmissibility and parameters influencing the same are also presented. A detailed chart is prepared to compare the research work done by different researchers in this field. Gaps in literature are compiled. Variations of grip force, elbow angle, resonance frequency and handle diameter are found to be significant factors when considering transmitted vibration to hand and arm. Further studies towards standardisation of methods and procedures are also suggested.

A cross-sectional survey of hand arm vibration symptoms among angle grinder operators employed in sheet metal work in North India

Abstract: This study investigates the prevalence of hand arm vibration symptoms and musculoskeletal disorders in the hand and arm of the angle grinder operators of sheet metal industries located in Chandigarh and nearby industrial areas in Northern India. Hand-transmitted vibration was measured in 42 sheet metal industries. A total of 83 workers, who were mainly employed for grinding job, were interviewed and vibration characteristics were measured using tri-axial accelerometer. Hand arm vibration symptoms, musculoskeletal complaints in hands and its correlation with tool weight were investigated. Results shown 84% daily vibration exposure measurements exceeded exposure action value (EAV) and 24% measurements exceeded exposure limit value (ELV). Hand arm vibration symptoms were finger numbness (40%), tingling (29%) and vibration white finger (VWF) (13%). Hand arm vibration symptoms in the workers were not significantly associated with tool weight. However, tool weight was significantly associated with musculoskeletal complaints in wrist, forearm and elbow of the workers. Preventive measures to reduce musculoskeletal complaints are proposed.

Acute Vascular Response of Hand to Force and Vibration

Abstract: This study aimed to investigate the acute effect of grip and feed exertions on the vascular system at the fingers during exposure to hand-arm vibration (HAV), and to identify which active hand force situation would have the most effect on finger vascular function. A total of 12 individuals attended the test, and each of them were subjected to eight sets of force-and-vibration situations: four with combinations of forces and vibration, and four control ones with only hand forces applied. The vibration stimulus was applied on the right hand at 2.75 m/s2 with a frequency of 125 Hz for three minutes, during which the application of grip and feed forces were set at either 10 N or 50 N. The weakening of the finger vascular function was reflected by a reduction in the finger blood flow (FBF) and finger skin temperature (FST). They were tested on both hands at fixed intervals before, during and after the exposure for in-time measurement. Hand forces resulted in clear reductions in FBF and FST in exposed right fingers whether the force was exerted solely or combined with vibration. The greater the hand force (especially grip force), the stronger the vascular response, while the additional reductions in FBF and FST from vibration were not significant. In the non-exposed left fingers, no significant changes in finger circulation occurred in response to force or vibration. Generally, vibration-induced acute finger vasoconstriction was affected by the hand forces, in which hand force seemed to play a more important part than vibration. A larger grip force would lead to a greater loss in the digital circulation than feed force. Thus, the level of hand force exerted on the tool handle should be limited to reduce the risk of harm from HAV.

Nonlinear Biodynamic Models of the Hand-arm System and Parameters Identification using the Vibration Transmissibility or the Driving-point Mechanical Impedance

Abstract: This study aims at deriving nonlinear expressions of the transmissibility and the driving-point mechanical impedance (DPMI) of two nonlinear biodynamic hand-arm models having active restoring and dissipative parameters. It aims also in computing explicitly the non-directly measurable stiffness and damping coefficients of the human hand-arm system (HAS). Multivariate Pade approximants are used to express the dependence of the HAS mechanical properties on various influencing factors. The harmonic balance method is used to derive analytical expressions of the transmissibility and the DPMI. Then, the models parameters are identified by minimizing constrained error functions between the theoretical DPMI or transmissibility and the measured data. The developed workflow is applied to three experimental data sets of Z-direction vibrations where the excitation frequency and/or the grip force are varied. Using the ISO-10068 (2012) limit DPMI values versus the excitation frequency, we derived upper and lower limits of the overall stiffness coefficient and damping ratio for the human HAS. Furthermore, the model reproduces with high accuracy experimental measurements of the transmissibility, the DPMI and the vibration power absorption.

Investigating the Relationship between Coupling Forces and Hand-Transmitted Vibration under Varying Excitation Levels

Abstract: In this study, the vibration total value of the acceleration transmitted to the wrist and elbow was measured in the laboratory with a group of 13 male subjects holding a cylindrical handle while modifying the coupling force under varying levels of vibration. The results were used to establish the relationship between hand-transmitted vibration and coupling forces and to compare with the relations proposed as part of an ISO Technical Specification, ISO/TS 15230-2. This was done to determine the suitability of the proposed relationships when variations are introduced on the level of vibration on the handle. While tracing back the origins of the relations proposed in ISO/TS 15230-2, this paper further brings in evidence of the importance of considering the role of coupling forces when evaluating the exposure to hand-transmitted vibration and provides additional evidence to support the relationships which are proposed as part of the ISO Technical Specification. Irrespective of the level of broadband random vibration excitation considered, the agreement with these relationships was found to be best when setting the reference coupling force at 50, 75, 100 and 125 N and whenever the coupling forces applied on the handle were maintained below 150 N.

An Experimental Study on the Vibration Transmission Characteristics of Wrist Exposure to Hand Transmitted Vibration

Abstract: This research intends to further improve the understanding of vibration damage mechanisms in the wrist area and to establish a more effective biodynamic model of the hand-arm system. Scholars have conducted some research work around the influencing factors of vibration response and commonly used vibration transmissibility to characterize the local vibration transmission characteristics of the hand-arm system. In this paper, a hand-transmitted vibration test platform was built according to ISO 10819, and a random combination of four ergonomic factors, namely wrist posture, arm posture, grip force, and thrust force, was used to test the vibration response of six subjects’ wrists; the total vibration transmissibility of the wrist was calculated according to the transmissibility formula. The effect of the four factors on the total vibration transmissibility of the wrist part was comprehensively analyzed, in which the wrist posture was proposed for the first time. The results show that (1) vibration transmissibility of the wrist is not only related to the arm posture, thrust force, and grip force but also related to the wrist posture; (2) the total vibration transmissibility and resonance frequency on the wrist has small correlation with large grip force and thrust force, and the vibration transmissibility of grip force 30 N and 60 N are basically equal in the low-frequency band (from 5–10 Hz to 5–20 Hz); (3) the wrist postures have a significant effect on the total vibration transmissibility at the wrist.