Understanding Vibration Transmitted to the Human Finger

Prolonged exposure of the hand to tool-induced vibrations is associated with the occurrence of debilitating conditions such as vibration white finger. The primary aim of this work is to gain a better understanding of the effects of different aspects of exposure to finger transmitted vibration (FTV) related to operators using hand-held vibrating tools. To achieve this, firstly, a new method for measuring finger transmitted vibration was developed and assessed, including a tool vibration test rig and measurement protocol. The effect on FTV measurement of using a small accelerometer attached to the back of the finger was investigated using 2D finite element modelling. Comparisons were also made using a laser vibrometer. Analysis showed that the new test rig is capable of measuring FTV at frequencies ranging from 10 to 400 Hz, under different grip force levels, and that adding a small accelerometer mass (0.3 grams) did not significantly affect measurements. A human participant study then carried out using the new rig. Various characteristic measurements were collected in tandem, including anthropometry, skin characterisation and behaviour under loading to investigate the effect of different factors on FTV. The results showed that FTV varied among individuals and the key finding was that exposure to vibration has a significant effect on finger temperature even for a short period of testing. Anti-vibration (AV) glove materials were investigated using dynamic mechanical analysis (DMA) and tested using human participants. The results showed that the mechanical properties of AV materials change under real world industrial conditions such as excitation frequencies and temperature. Finally, a new artificial test-bed was developed to replicate the transmitted vibration of the index finger. Studies were conducted on a range of 5 test-beds, to allow comparison with the human measurements, including indentation, vibration transmissibility and FE modelling. FE modelling showed that the distribution of dynamic strain was found to be highest in the vasculature region of the finger, indicating that this could be one of the contributing factors of VWF. One of the finger test-bed was selected as best replicating the mechanical properties of the real finger. The artificial test-bed provided better consistency than human participants, for testing parameters, such as grip force, and can be used in future for testing AV gloves with no need for human subjects.ii Further investigations are suggested to be made to enhance the limitations of this project, including material analysis, testing protocol and finite element modelling. Keywords:, hand-arm vibration syndromes, vibration white finger, FTV, transmissibility, resonance frequency, grip force, AV glove, finger mechanical properties, artificial finger, finite element modellin

Understanding Vibration Transmitted to the Human Finger

Prolonged exposure of the hand to tool-induced vibrations is associated with the occurrence of debilitating conditions such as vibration white finger. The primary aim of this work is to gain a better understanding of the effects of different aspects of exposure to finger transmitted vibration (FTV) related to operators using hand-held vibrating tools. To achieve this, firstly, a new method for measuring finger transmitted vibration was developed and assessed, including a tool vibration test rig and measurement protocol. The effect on FTV measurement of using a small accelerometer attached to the back of the finger was investigated using 2D finite element modelling. Comparisons were also made using a laser vibrometer. Analysis showed that the new test rig is capable of measuring FTV at frequencies ranging from 10 to 400 Hz, under different grip force levels, and that adding a small accelerometer mass (0.3 grams) did not significantly affect measurements. A human participant study then carried out using the new rig. Various characteristic measurements were collected in tandem, including anthropometry, skin characterisation and behaviour under loading to investigate the effect of different factors on FTV. The results showed that FTV varied among individuals and the key finding was that exposure to vibration has a significant effect on finger temperature even for a short period of testing. Anti-vibration (AV) glove materials were investigated using dynamic mechanical analysis (DMA) and tested using human participants. The results showed that the mechanical properties of AV materials change under real world industrial conditions such as excitation frequencies and temperature. Finally, a new artificial test-bed was developed to replicate the transmitted vibration of the index finger. Studies were conducted on a range of 5 test-beds, to allow comparison with the human measurements, including indentation, vibration transmissibility and FE modelling. FE modelling showed that the distribution of dynamic strain was found to be highest in the vasculature region of the finger, indicating that this could be one of the contributing factors of VWF. One of the finger test-bed was selected as best replicating the mechanical properties of the real finger. The artificial test-bed provided better consistency than human participants, for testing parameters, such as grip force, and can be used in future for testing AV gloves with no need for human subjects.ii Further investigations are suggested to be made to enhance the limitations of this project, including material analysis, testing protocol and finite element modelling. Keywords:, hand-arm vibration syndromes, vibration white finger, FTV, transmissibility, resonance frequency, grip force, AV glove, finger mechanical properties, artificial finger, finite element modellin

The development of a new artificial model of a finger for assessing transmitted vibrations.

Prolonged exposure of the hand to tool-induced vibrations is associated with the occurrence of conditions such as vibration white finger. This study involves the development of a new artificial model that approximates both loading and vibration behaviour of the human finger. The layered system uses polypropylene "bones", encased in a cylinder of low modulus, room-temperature curing silicone gel (to replicate subcutaneous tissues), with an outer layer of latex (to replicate the dermis and epidermis). A protocol for manufacture was developed and dynamic mechanical analysis was carried out on a range of gels in order to choose a range close to the mechanical properties of the human finger. The load-deflection behaviour under quasi-static loading was obtained using an indenter. The indentation measurements were then compared with a set of validation data obtained from human participant testing under the same conditions. A 2-D FE model of the finger was also used to assess vibration responses using existing parameters for a human finger and those obtained from the tested materials. Vibration analysis was conducted under swept sinusoidal excitations ranging from 10 to 400Hz whilst the FE finger model was pressed 6mm toward the handle. Results were found to compare well. This synthetic test-bed and protocol can now be used in future experiments for assessing finger-transmitted vibrations. For instance, it can aid in assessing anti-vibration glove materials without the need for human subjects and provide consistent control of test parameters such as grip force