The hand tool handle grip Finite Element Modeling and Research

 

Jiang Xi University of special equipment manufacturing and advanced processing technology, Ministry of Education / Key Laboratory of Zhejiang Province, Hangzhou 310014)

 

Abstract: The tool handle for hand when the hand gripping surface pressure distribution of the target, the structure and motion of the hand characteristics of the hand gripping the handle situations create gripping criteria established for the hand gripping the handle geometry, By ABAQUS finite element analysis software, meshing, setting gripping process and boundary conditions finite element model, the final analysis the hand gripping the handle virtual simulation case hand pressure distribution, and validated with actual similar catch situation according grip for the hand of a surface pressure measurement seek new virtual measurement channels.

 

Keywords: Handle; grasp; finite element; pressure distribution

 

CLC: TP391.7 Document code: A Article ID :1671-3133Q011) 12-0031-04

 

0 Introduction

 

    Hand in their daily life and work process, is the use of tools, equipment, etc. manipulating the main carrier of a series of social activities, plays a very important role. Because the tool handle design flaws and hand grip on the manipulation of various reasons such as improper operation, will lead to opponents of the injury and accident conditions. It has long been opponents of the anatomy, physiology and sports performance features and tools designed to handle and so were a lot of research. Tool handle gripping the hand gesture shown in Figure 1, the use of hand tools, the hand directly affects the distribution of pressure on the tool to see hand comfort, hand pressure on the location and size of the hand to evaluate the comfort of an important indicator. At present, the opponents of the stress tests are used physical prototype testing method, such as through the strain gauge affixed to implement a data glove. Development and design of the tool handle, using physical prototype testing, requires repeated trial and testing, high cost, low efficiency and the development and design cycle is long.

 

    This article gives the hand surface pressure measurements to find a new test approach, the use of virtual simulation testing technology to get the hand gripping the handle of the hand when the surface pressure distribution as the goal, through the hand grip model and tool handles interactions between models and, ultimately, good experimental results.

 

An analysis tool handle hand grip

 

1.1 Hand structure outlined

 

    Hands are an important part of the body, which constitutes a complex mainly by epithelial tissue, muscle tissue, connective tissue and nervous system, bones, skin, and other components, and circles. Connected by a joint between bones, muscles attached to the bones above the skin and other soft tissue overlying the muscle beyond. Shown in Figure 2, the hand is a multi-joint system of the hand bones skeleton of 27, divided into the carpal, metacarpal and phalangeal three parts. Carpal by the hook, lunate, triangular bone 8 composition. Metacarpal of 5, the thumb "humb) to finger ~ inky) were metacarpal 1 to 5, near termination carpal, remote access phalanx. Phalanx of 14, only two phalanges except the thumb, the other four fingers have three phalanges, respectively, for the past phalanx, middle phalanx and distal phalanx laps. Hand by the wrist, hand, thumb and four fingers of the other adjacent components, which are interconnected by a joint, with the rotation of the joint between the hand posture is changed.

 

1.2 of hand motion constraints

 

    Staff are mainly three kinds of movement forms: flexion, and rotation of the closing show. Hand movement as a whole in the space has six degrees of freedom of the model in the hand movement of the finger, regardless of the movement of the human body when palmistry, the six degrees of freedom may be limited. Shown in Figure 2, the movement of the thumb joint TIJ have a degree of freedom to do flexion movement, TiVIPJ and TM, respectively, two degrees of freedom, doing flexion and extension and outreach campaign; other four fingers movement joints DIJ and PIJ have a degree of freedom to do flexion movement, Mpj has two degrees of freedom, doing flexion and outreach campaign; another four MCJ also have a degree of freedom secluded. Thus, the analysis of the hand grip, the 25 degrees of freedom to consider Pei.

 

    According to the motion characteristics of manpower, the movement of each finger are attached to the palm of your hand, a single finger from the palm refers to the segment in turn attached to the remote closer to the finger away from the palm section of the movement of the finger joints mainly around the rotational movement. Each joint can be created on a local coordinate system, each finger on the local coordinate system of affiliation constitutes a multi-level coordinate system. With the index finger for example, the multi-coordinate system shown in Figure 3. The joint in the axial direction to take the X-axis direction, the connection joint to the next joint direction l, axis, Z-axis direction is determined based on right-hand rule. No external load is applied in the hand and a free state to withstand external loads, the finger motion of each joint has a certain angle range

 

1.3 Guidelines grip

 

    Is the essence of the finger flexion joint rotation, and rotation of the joint turn, cause muscle contraction, the more complex physiological process network. Thus the simulation tool handle grip, the need to simplify this process and reasonably controlled.

 

    1) in the gripping only minor changes in the process of bone fixation. 2-5 metacarpal tiny movements can be regarded as fixed and reducing the four degrees of freedom.

 

    2) the number of joints to rotate only about the X-axis degree of freedom. Gripping process, in a certain initial state, the main job of fingers flexion movement, closing exhibition sport is smaller, locked joints Mpj, TMpj and TM, around l, axis 6 degrees of freedom.

 

    3) Each section refers to the segment around the respective local coordinate system X-axis, the establishment of each finger on the corner of each finger segment d, £ a function of time in order to achieve take off clothes into the handle grip control function: where : Si: the proportional coefficient; ao. Refers to the initial position for the segment angle ;/ = 1,2,3.

 

Wherein the fingers including the thumb scare) rotation of the third joint are not independent, the rotation of the second joint linkage between a certain, substantially as a linear ratio between the negative, namely:

 

a3 = Q / 3) a,

 

    4) during the finger grip tool handle with the handle in contact with the handle curved finger refers to the segment interaction to a certain extent be regarded as gripping success. After the handle grip, hand grip surface bonding surfaces, such as muscle tissue produce some extrusion deformation, the deformation depends on the location and extent of grip styles, handle curved shape, location and energizing force size, the finger will turn the extent refers to the segment by the fingers squeeze the handle force generated between the surfaces to achieve maximum impact.

 

Two hand grip tool handles Finite Element Modeling

 

2.1 simplified hand grip

 

    Does not reduce to the maximum the case of authenticity, the process for the tool handle grips, grip the opponent reasonable simplified.

 

    1) Consider the process of hand grip, the hand force of the opponents of the influence of various parts of the organization, the model is simplified to only include: some of the bones, muscles, and refers to the segment part of the connecting portion between the joints.

 

    2) to establish the initial grip handshake model form for the upcoming grab hold of the handle forms. Opponents grip shape to set the initial model, the initial model of the hand gesture is not in contact with the handle models, but coming to the handle grip, greatly reducing the fingers bent, deformed joints might be too large grasping result affected.

 

    3) simplified joints. Get the handle grip surface pressure distribution, and virtual measuring surface pressure, the connecting joints is not the main surface of the pressed portion, the connection between the bone and bone hinged similar manner, the appearance of the transition segments using two connection means form. In the first finger, the second joint portion, for example, the simplified schematic shown in Figure 4.

 

2.2 Finite element model

 

    Comprehensive analysis of the foregoing, the use of three-dimensional modeling software to build the hand grip model geometry, and then build the geometric model into ABAQUS finite element analysis software, to mesh, material properties and other settings.

 

2.2.1 Meshing

 

    Grasp the handle, both produced by bending the finger hand model large deformation, another hand model and grasping the handle contacts between models, you should select for large strain problems and exposure to structured analysis grid or sweep swept mesh generation Hex element mesh.

 

    However, due to the geometry of the hand grip model is more complex, the overall use of the structure can not be swept Pi grid or mesh, opponents grip model part adopts free meshing technology to generate Tet element mesh. Taken together, the model is part of the use of bones and fingers swept mesh, linear reduced integration unit (C3D8R), palms and the tiger's mouth position using the modified quadratic Tet unit C3DlOM). Different types of grid cells at the junction of the ABAQUS finite element analysis software automatically creates a tie constraint smell. 2.2.2 Material properties settings

 

    Literature D], literature [10], setting bones and muscles as part of the Young's modulus 7300MPa, 50MPa, Poisson's ratio of 0.3, 0.3, refers to the segment joints connecting portion is disposed between the super-elastic material properties and other relevant parameters.

 

    Finite element analysis model hand grip and hand bone model in the model in the hand position shown in Figure 5, Figure 6.

 

2.3 Simulation handle hand grip

 

    In ABAQUS finite element analysis software, has been established in the hand grip model file to import a model tool handles, hand gripping the handle in front of the finite element model shown in Figure 7. After setting the boundary conditions: the hand carpal, metacarpal and handle fixed; hand model and handle the model surface contact friction factor of 0.05; finger grip function of the process of joint rotation, etc.

 

    After setting the hand gripping the handle of the FEM analysis, the hand gripping the handle grip posture post shown in Figure 8, the results show the hand gripping position of the contact stress distribution shown in Figure 9, the front end palm refers to the segment and the various pressures greater maximum stress value is 0. 810 8MPa. Similar to the actual pattern of the hand grip, the hand grip for use of transparent glass, similar to practical hand grip force in the position shown in Figure 10. Through the simulation results with the actual circumstances of the hand grip force the contact area a qualitative comparison, you can get the following conclusions: the hand gripping the handle created through virtual simulation model, the resulting pressure distribution on the surface of the hand position similar to the handle with the actual situation of the hand gripping position substantially in line pressure.

 

3 Conclusion

 

    In this paper, a brief analysis of the structure and motion characteristics of hand, the establishment of hand gripping the handle grip case criteria. On this basis, the establishment of the hand gripping the handle oriented finite element analysis model, the use of virtual simulation test methods, the use of ABAQUS finite element analysis software, through the hand gripping the handle model and the interaction between the models obtained more satisfactory the case of the hand gripping the handle portion of the surface pressure distribution of the hand, the hand unit of a surface pressure measurement seek new virtual measurement channels.