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EFFECTS OF PRESSURE SUIT AND RACE ON

FUNCTIONAL REACH, STATIC AND DYNAMIC STRENGTH

A Thesis

Submitted to the Graduate Faculty of the
Louisiana Sate University and
Agricultural and Mechanical College
in partial fulfillment of the
requirements for the degree of
Master of Science in Industrial Engineering

in

The Department of Industrial and Manufacturing Systems Engineering

b y

Nageswara Rao Uppu
B.E. (Mechanical Engineering)
Madras University, India, 2000
December, 2004

pp. i - xi and 1 - 109

ABSTRACT

"In the design of any manual workspace, it is important for the designer to have access to data that can illustrate reach capabilities under real-time work situation. Wearing bulky clothing (pressure suit) and protective restraints (seat or shoulder harness belts) is often mandatory in high acceleration work environments. Clothing and personal equipment worn can influence the functional reach and strength values since they add to the body size. The present study was conducted to investigate the effect of wearing a VKK-6M pressure suit on functional reach limitations and strength values.

The technology of incorporating body dimensions into cockpit design primarily evolved in western countries and therefore the only datasets available is of Caucasians. When designing equipment for populations other than westerners, western anthropometric data is inappropriate. In this thesis a representative sample of Caucasian and Asian Indian population are chosen and their reach envelopes are compared. Subjects reach and strength data are collected with and without-suit and analyzed to see the effect of pressure suit on reach and strength.

The study concludes that wearing pressure suit reduces the average reach significantly (at a = 0.05). The 5th percentile Asian Indian and Caucasian reach envelopes are derived for placement of critical cockpit controls. Race-reach study showed a significant difference in shoulder breadth of Caucasians and Asian Indians (at a = 0.05), but no apparent relationship between bideltoid breadth and thumb tip reach was found. The study on significance of wearing pressure suit on strengths (at a = 0.05) concluded, suit does not affect static or dynamic strength.

INTRODUCTION

[The] Aviation industry, in achieving its aim of optimizing use of space and weight for an aircraft, has the utmost need for applying anthropometric data into design. Functional anthropometric data can be used in improving pilot's performance by minimizing stretching and over extension from the seated position. Care should  be taken to incorporate anthropometric measurements fro a wide variety of users while in the design stage of the equipment. This allows not only an average individual but also the extremes of a population, being able to operate the equipment equally effectively. It is important to realize that there is no average individual and designing for the average user is often seen as bad design, as it only accommodates 50% of a population (Pulat, 1997). An ideal cockpit design controls should be within the reach of the smallest operator while on the other hand, the cockpit should be able to accommodate 95 percentile of headroom for the tallest operator. In some situations, the dimensions of a workspace may become a limiting factor that may restrict its usage. For the aviation industry, this limitation on workspace eliminates a pool of potential recruits based on their stature and eye height, although they have appropriate anthropometric characteristics.

If population differences are not been accounted during the design process, then the selection of users is required. The selection criteria are based on one of the two methods. The first is the trial and error, in which all the users who are unable to perform certain tasks at some point during the training are eliminated. The second approach relies on use of available data sources from various studies on reach demands of users performing different operational tasks (Usher and Aghazadeh, 1988). A person with 5% stature doesn't mean the reach of that person falls in the 5% of population. Hence, before designing a workplace, designers must look into anthropometric and reach data of the people from different age, gender, race and work groups. This process of collecting data deals with physical measurements of a person's size and form for developing engineering drawings and preparing mock-ups. The data thus obtained accounts for the selection criteria based on the reach, clearance and visibility requirements for that particular workplace.

While designing an experimental setup, it is important to simulate the experimental conditions most likely prevailing in the work situations. For example, while studying a pilot flying a high altitude aircraft, an Anti-G suit (Anti Gravity suit) which protects him during rapid accelerations and fast turns, has to be considered. Most of the design data collected on functional reach is gathered under light clothing and under earth's gravitational field which does not affect the reach measurement. The length of functional arm reach is dependent on the kind of task or operation to be performed. As shown in Table 1.1, sustained high-G accelerations can significantly influence the functional reach capability or range of motion of an articulation.

Table 1.1: Influence of high-G accelerations on reach capability


                                                                          Acceleration Level              Reach Motion Restricted To

                                                                          Up to 4 G                                              Arm
                                                                          4 to 5 G                                                 Forearm
                                                                          5 to 8 G                                                 Hand
                                                                          8 to 10 G                                               Fingers

Source: Webb Associates (1978)

Factors affecting reach can broadly be classified as functional requirement, protective equipment worn and race. Functional requirements include wearing protective restraints (e.g. seat or shoulder harness belts) that are often required in vehicles or other work environments where unexpected acceleration or deceleration may occur. Restraints can significantly alter reach measurements. Thus, use of anthropometric datasets developed using similar restraint systems is required. Sustained high-G accelerations can significantly influence the reach capability or range of motion of an articulation (Table 1.1: Webb Associates, 1978). Normal reach tasks that people perform in day to day activity require coordination of multiple body segment rather than maximum effort. A task requiring only a finger grip pressure (push button) can be located at the outer limits of the arm reach, as defined by the finger tip reach would be the maximum functional reach attainable. Where as, other tasks that may include rotation of a control knob between thumb and forefinger which would result in reduction of functional reach. Tasks like full hand grip of a control level would reduce maximum functional reach further. Jobs where precision or continuous operation of an equipment or tool is required, the controls should be located further close to the operator (Pulat, 1997).

When designing reachable controls, one should consider any potential restraint caused by the persons clothing. Clothing and personal equipment worn on the body can influence functional reach measurements significantly. The effect is mostly a decrease in reach, but this decrease has to be considered if clothing or equipment is bulky and cumbersome. This empathize [emphasizes ?] the point that most design data collected on functional reach is gathered under light clothing and under earth's gravitational field which does not affect the reach measurement. One of the neglected areas in equipment and workplace design is optimization of the matching of equipment with the specific characteristics of the operators and users (Lamey, Aghazadeh and Nye, 1991). Hence when designing for a set of users, the anthropometric characteristics of the users has to be considered. Caucasian population generally has wide shoulders and large stature than Asian Indians. When designing equipment for Asian Indians, western anthropometric data is inappropriate and equipments designed considering the anthropometry of western people would not be suitable (Viren et al., 2002).

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