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Decision Support System for Generating Optimal Sized and Shaped Tool Handles
Published in Vincent G. Duffy, Advances in Applied Human Modeling and Simulation, 2012
Gregor Harih, Bojan DolšAk, Jasmin Kaljun
Since most of the products are designed to be human hand operated, many authors have researched the topic of tool handle design to define the optimal size and shape of a tool handle, since a correctly designed handle can provide safety, comfort and increased performance. Different authors used different criteria to determine optimal cylindrical handle: subjective comfort rating (Yakou et al., 1997, Hall and Bennett, 1956); finger force measurement (Amis, 1987, Chen, 1991); muscle force minimization (Sancho-Bru et al., 2003) and hand anthropometrics (Grant et al., 1992, Oh and Radwin, 1993, Johnson, 1993, Yakou et al., 1997Blackwell et al., 1999, Garneau and Parkinson, 2010, Seo and Armstrong, 2008). Few studies also used two or more criteria: finger force measurement and muscle activity (Ayoub and Presti, 1971, Grant et al., 1992, Blackwell et al., 1999); subjective comfort rating, finger force measurement and electromyographic efficiency of muscle activity (Kong and Lowe, 2005). Since many different user cognitive and bio-mechanical constraints were considered in mentioned papers, therefore also used methods for the determination of optimal cylindrical handle differ very much. Resulting diameters of the cylindrical handles vary from 25mm to 60mm and above.
Hands and Handles
Published in Stephen Pheasant, Christine M. Haslegrave, Bodyspace, 2018
Stephen Pheasant, Christine M. Haslegrave
The purpose of a handle is to facilitate the transmission of force from the musculoskeletal system of the user to the tool or object being used in the performance of a task or for a purpose (see Figure 1.1). As a general rule, we can say that to optimise force transmission is to optimise handle design. The principles of design for a wide variety of tools are discussed by Greenberg and Chaffin (1976) and Freivalds (1987). Freivalds highlighted four main anatomical concerns, in addition to effectiveness of the tool itself; these are the avoidance of static muscle loading, awkward wrist and finger postures, tissue compression and repetitive finger action.
Engineering materials and heat treatment
Published in Roger Timings, Engineering Fundamentals, 2007
This is the ability of a material to conduct heat. Metals are good conductors of heat and non-metals are poor conductors of heat. Figure 4.4(a) shows an electrically heated soldering iron. The bit is made of copper because this is the best of the common metals for conducting heat. It conducts the heat from the heating element to the joint to be soldered. Copper also has an affinity for soft solder so it can be easily ‘tinned’. The handle is made of wood or plastic as these materials are easily shaped and are poor conductors of heat. They are heat-insulating materials. They keep cool and are pleasant to handle.
Effects of handle characteristics of manual hand tools on maximal torque exertions: a literature review
Published in International Journal of Occupational Safety and Ergonomics, 2022
Azam Maleki-Ghahfarokhi, Mahmood-Reza Azghani, Iman Dianat
Based on the mentioned findings, it seems that there is a direct correlation between handle diameter and maximum torque strengths as long as the highest torque measures are reached and, then, there is an inverse correlation between the mentioned variables. In other words, apparently a bell-shaped relationship between handle diameter and maximal torque exertions exists. This means that by increasing the handle diameter, torque strength increases to reach an optimum level and then, as an inverted U-shaped function, decreases with increasing diameter. Based on this review, there is no consensus about the optimal diameter; therefore, those handle diameters that provide a better hand–handle interface for torque strength generation should be examined more closely in future studies. Additionally, due to variations in users’ hand anthropometry, there is not just one optimum handle diameter for all operators. The maximum voluntary finger contraction force depends on diameter, and therefore, based on finger and hand sizes, handle sizes should be varied [38]. Thus, while investigating the optimum handle diameter, hand size should also be considered. Some investigators have also acknowledged that the hand tool handle should fit the user’s hand [47]. Among the reviewed papers, 14 studies reported one or more upper extremity anthropometry dimension, but most of them just reported these data and did not apply the measures when recommending an optimum handle diameter.
Finite element modal analysis and harmonic response analysis of human arm grasping model
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2020
Shuang Liu, Hongmei Xu, Yujun Shang, Wei Jiang, Jiajun Dong
The bones and hard connective tissues in the arm can be considered as linear elastic materials. Soft tissues such as skin and subcutaneous tissues can be considered as superelastic and viscoelastic materials. The superelasticity provides an accurate description of the behavior of the elastomer under large deformation (>1–2%), and is also a commonly used attribute in the modeling of biological soft tissues (Liang et al. 2007; Liu 2012). The handle is the medium through which the operator manipulates the machine or tool. Hence, the design of the handle is directly related to the operator's handling comfort and physical and mental health. Previous studies have shown that the operating comfort and safety are largely dependent on the handle diameter (Imrhan and Farahmand 1999), nature of the surface material (Mårvik et al. 2006), handle shape (Kong et al. 2008), friction coefficient of contact surface (Seo et al. 2008), and stiffness of the contact surface. In this study, the handle was mainly composed of a cylinder and an outer handle sleeve. The cylinder is made of aluminum, and the outer handle sleeve is made of synthetic viscoelastic urethane polymer, with the shore A hardness 70–80 and a friction coefficient of 0.3 on the surface of the hand. For the ligament, since the phalangeal joints are hinged, the parameter setting of the ligament takes the connection characteristics of the structure into account, and the spring stiffness and damping coefficients are given. The stiffness of the rotating spring along the bending and extension direction of the hinge is 0.01 N/m. The damping coefficient is 0.05 (Li et al. 2006). The material parameters of each component of the finite element model are shown in Table 3.
Evaluation of the biodynamic response of the hand–arm system and hand-tool designs: a brief review
Published in International Journal of Occupational Safety and Ergonomics, 2023
Jain A. R. Tony B, M.S. Alphin
The important studies on hand-transmitted vibration exposure and health effects conducted by the researchers were summarized and elaborated in this review, as follows: Sections 1 and 2 reviewed the health effects due to the continuous usage of hand-operating tools, and currently available vibration standards and regulations to be followed while using hand tools were explained in detail. This challenge will be useful for the standardization of evaluating the biodynamic response of the hand–arm system.Sections 3 and 4 focused on the tool handle evaluation methods using objective and subjective measurements. To measure the vibration exposure, objective measurements will give more exact results than the subjective measurements. Objective measurements need more expensive sensory devices to measure the exposure, but the subjective measurements were based on the perception of the subjects. Combining both objective and subjective measurements is very important to estimate and to overcome the vibration exposure.In Section 5, some notable design methods were discussed in order to achieve better tool handles. Considering the shape and size of the tool handle also plays a major role to overcome the vibration exposure. A handle with a grip of the middle fingertip and thumb fingertip overlap for 1 cm gives better grip than the other diameter handles. Section 6 discussed 2D and 3D finger model design and simulation while gripping different shaped handles with different grip force. The section also discusses the behaviour of the bone, nail, skin, tissue and subcutaneous tissue, etc., during the static and dynamic analysis.In our opinion, the field of developing an ergonomic handle is very important to overcome the vibration discomfort. Several studies were made by researchers to improve the handle design to overcome the discomfort. There are still various areas need to be investigated.Future work in handle design could be done by considering the grip force exerted to the handle, hand–handle interface and the contact pressure during different hand postures to reduce the muscle activity.The effect of human hand-based handles during different activities, behaviour of the hand–arm muscles, muscle loading and muscle activity can be estimated further using electromyography (EMG).Numerical analysis (static and dynamic) can be performed to estimate the mechanical behaviour of the hybrid finger model gripping various shapes handles with different grip forces.