Basis of Physical Ergonomics

At its most basic level, PE is concerned with two aspects of physical effort: (1) the physical demands placed on the human and (2) the physical capabilities of the human in the situation where the demands are present. Simply, the goal is to ensure that demands do not exceed capacity, as is typical for the design of any mechanical system.

A major challenge in PE is the measurement of both demands and capacity in the wide variety of circumstances where human physical exertions are performed (or required, as in the occupational context). Physical requirements vary widely and include dimensions such as force, torque, repetition, duration, posture, etc. Similarly, human attributes vary widely across related dimensions (e.g., strength, endurance, mobility).

Along with the measurement problem is the related problem of matching. Given the variability in both demands and capacity, potential mismatches are likely (and prevalent in many cases). Occupationally, poor matching can lead to low productivity and quality, worker dissatisfaction and turnover, and in many cases musculoskeletal illness and injury.

Ongoing research is being widely conducted to address both the measurement and matching problems. In the material presented below, we have given examples of contemporary approaches, but the reader is advised that more advanced methods are currently available and the technology is rapidly advancing.

Maury A. Nussbaum

Industrial and Systems Engineering

Virginia Polytechnic Institute and State University

Blacksburg, Virginia

Jaap H. van Diee¨n

Faculty of Human Movement Sciences

Vrije Universiteit

Amsterdam, The Netherlands

Mechanical Engineers’ Handbook: Materials and Mechanical Design, Volume 1, Third Edition.

Edited by Myer Kutz

Copyright  2006 by John Wiley & Sons, Inc.

WHAT IS PHYSICAL ERGONOMICS?

Definitions and Brief History Ergonomics is derived from the Greek ergon (‘‘work’’) and nomos (‘‘principle’’ or ‘‘law’’). Original attribution is debated but is usually given to the Polish professor Wojciech Jastrzebowski in a treatise published in 1857 and intended to represent the ‘‘science of work.’’ The same term seems to have been reinvented in 1949 by the British professor K. F. H. Murrell with the same general intended meaning. In the past decades ergonomics as a scientific and/ or engineering discipline has seen a dramatic increase in research and application as well as attention from the general public. As such, the original term has, in cases, lost some of its original meaning. Returning to these origins and to provide a focus for this chapter, the following definition does well to encompass the current state of ergonomics as having a theoretical and multidisciplinary basis, being concerned with humans in systems and ultimately driven by real-work application (Ref. 1): Ergonomics produces and integrates knowledge from the human sciences to match jobs, products, and environments to the physical and mental abilities and limitations of people. In doing so it seeks to safeguard safety, health and well being whilst optimising efficiency and performance. As a recognized professional domain, ergonomics is quite young, becoming formalized only after the World War II. Related efforts were certainly conducted much earlier, such as Borelli’s mechanical analysis of physical efforts in the late-seventeenth century and the identification of work-related musculoskeletal illnesses by Ramazzini in the early-eighteenth century. It was only in the 1950s, however, that researchers with expertise in engineering, psychology, and physiology began to come together to realize their common goals and approaches. Ergonomics continues to be an inherently multidisciplinary and interdisciplinary field, which will be evident in the remaining material presented in this chapter. 

Maury A. Nussbaum
Industrial and Systems Engineering
Virginia Polytechnic Institute and State University
Blacksburg, Virginia
Jaap H. van Diee¨n
Faculty of Human Movement Sciences
Vrije Universiteit
Amsterdam, The Netherlands

Mechanical Engineers’ Handbook: Materials and Mechanical Design, Volume 1, Third Edition.
Edited by Myer Kutz

PRODUCT DESIGN ; MACHINING PROSES

Machining is the process of making things work with perautan (remove unwanted material from the workpiece in the form of chips). If the body is metal work, there is often known as metal cutting or metal removal. Chip Formation Process There are 7 basic process of chip formation, namely: Shaping, Turning, Milling, Drilling, Sawing, Broaching, and Grinding (Abrasive Machining). In the process of cutting metal will always be the term: Speed, Feed and Depth of Cut for explaining the problem illustrations will use Turning process. SPEED (V) is the main piece in which movement associated with the workpiece rotational speed of the chisel cut. Unit: Surface Feet Per Minute (SFPM), Inch Per Minute (In / M), Meters Per Minute (M / M). FEED is the amount of material lost per round. In the process of turning movement parallel to the axis of rotation Feed workpiece. Unit: Inch Per Round (In / Rev), Cycle Per Inch, Inch Per Minute, Tooth Per Inch.

PRODUCT DESIGN : Steel

Steel is a compound of iron (Fe) and Carbon (C), which often also added the element chromium (Cr), Nickel (Ni), Vanadium (V), Molybdaen (Mo) and others to get certain properties desired on the application in the field, such as anti-corrosion properties, heat resistance, high temperature resistant. Compared to other types of metals (eg Aluminium, Copper, etc.) then the iron / steel is the material most widely produced in the world today. Statistics show that 92% of the world is the use of metallic iron / steel. In 1998, production Rohstahl / raw steel (raw steel) amounting to 750 million tonnes. Because of the large market share of this steel, the advanced countries in the steel industry are competing to create a new engineering-engineering in the production process. The goal is to get good quality steel with a relatively cheap price. One of the important intermediate product is steel plate (strip, plate, sheet) with a wide variety of thicknesses. Steel plates are widely used as a raw material for production of car body of a car, train, to kitchen utensils. Conventional process of manufacturing steel plates are usually as follows: The first time, liquid steel cast by the method Strangguss / continuous casting. From here the obtained results in the form of steel bars (slabs) with a thickness of 150 to 320 mm. The next process is the thinning of the thickness with a rolling mill in order to obtain a thin slab 2 to 20 mm. One way of simplification of production is to create a continuous casting installation capable of producing steel with a thickness below 150-320 mm. Since 1980, has successfully cast steel bar with a thickness below 25 mm (eg CPR method). Thus could be savings in the process of rolling. Since these fifteen years the Institute for metal forming (IBF), RWTH Aachen University of Technology, Germany in cooperation with Thyssen Krupp Stahl AG (TKS) tried to do a new breakthrough in the production of strips (thin steel plates). This new breakthrough has actually only dream of long ago by Sir Henry Bessemer in 1891. Experts from the British steel has even patented the design and installation of thin steel-making process known as "double-roller process." In this principle, liquid steel cast in between two rollers (cylinders) water-cooled, rotating in opposite directions. The thickness of steel plates produced depends on setting a gap between the two cylinders. Another factor affecting the geometry of the product is spread pressure (pressure) between the slit and also the spread of temperature in the cylinder. The next stage, steel plates passed on cooling (water), then through the cold rolling, and finally rolled up (coiling). With this method, have been successfully cast in steel plates with thickness below 3-4 mm, so only with the process of rolling one step can be obtained steel with thickness as the finished product. The principle of this new double-roller process can be realized in the late 20th century along with the progress of computerization in the field of control and measurement technology. In this world, according to one researcher from TKS AG, this method was developed in Italy, Australia, Japan, and Germany. While the USA would prefer to buy the works from Australia. Until now, each competing with each other, and each other to hide the results have been achieved. TKS AG itself has created an installation in thin strip casting (casting thin steel plates) with a double roller method in one of its factories in the town of Krefeld, Germany. On December 10, 1999 has done a test installation first time, with the result of thick steel plates 3 mm, width 1100 mm, weight 36 ton. The material is cast steel of the type of stainless-steel. Later, Krefeld will produce strip with a thickness of 1.5 to 4.5 mm, width 1050 up to 1350 mm, with a speed of 100 meters per minute