Musculoskeletal computational analysis on muscle mechanical characteristics of drivers’ lumbar vertebras and legs in different sitting postures

SUMMARY Using computer-aided engineering (CAE) in the concept design stage of automobiles has become a hotspot in human factor engineering research. Based on human musculoskeletal biomechanical computational software, a seated human-body musculoskeletal model was built to describe the natural sitting posture of a driver. The interaction between the driver and car in various combinations of seat-pan/back-rest inclination angles was analyzed using an inverse-dynamics approach. In order to find out the “most comfortable” driving posture of the seat-pan/back-rest, the effect of seat-pan/back-rest inclination angles on the muscle activity degree, and the intradiscal L4-L5 compression force were investigated. The results showed that a much larger back-rest inclination angle, approximately 15°, and a slight backward seat-pan, about 7°, may relieve muscle fatigue and provide more comfort while driving. Subsequently, according to the findings above, a preliminary driving-comfort function was constructed.

Investigating the influence of seating area design and enclosure on the seat-dip effect using scale model measurements

The low-frequency attenuation in the direct sound due to the concert hall seats, i.e., the seat-dip effect, is studied with the help of a scale model comprising an adjustable seating area and an enclosed box. More particularly, different seat underpass sizes and floor raking angles are studied, and the results are averaged over multiple source positions. With the measurements on the seating area only, the main seat-dip frequency is found to depend on the seat back rest height, and on the degree of obstruction of the seat underpass. The attenuation bandwidth is found to depend mainly on the floor raking. The differences become less clear when seating area is enclosed by concert hall walls and ceiling because the early reflections from the concert hall geometry compensate the low-frequency attenuation in the direct sound. In addition, the low frequencies below the main seat-dip frequency are found to increase in the presence of unobstructed seat underpasses, and such seats are recommended for the maximal bass response in a concert hall.

Effects of sizing and yarn structural properties on the physical properties of combed and carded cotton ring yarns

Warp yarns, prepared as warp beam, are exposed to various forces at weaving loom. Warp yarns are bended on the back rest, subjected to friction from drop wires and healds. They are also exposed to friction and impact at reed and thereby abraded. Yarns are sized in order to increase their resistance to these effects. Sizing agents ensure that warp yarns can be weaved with sizing process. On the other hand, yarn count and yarn type (combed or carded yarn) are the significant yarn structural properties that determine and so affect the physical properties of yarn. The main reason and objective this study is to investigate the effects of yarn structural parameters (yarn count and yarn type) and sizing on the physical properties (breaking strength, elongation at break, hairiness, friction coefficient) of 100% cotton carded and combed ring yarns, sized with four different sizing agents, which were not studied in the references. It is observed that sizing process cause to decrease in the hairiness up to 99% and in friction coefficients of combed and carded yarns whereas to increase in the breaking strengths of combed and carded yarns. And also, the combed yarns had better tensile and frictional properties than carded yarns.

ERGONOMIC IMPROVEMENTS IN THE HANDLING OF FIBRE INSULATOR SHEETS CUTTING

This paper gives emphasis to an ergonomics study conducted in a fibre insulation bay of a medium-sized air handler manufacturing plant. Work-related musculoskeletal disorders and other health problems in the fibre insulator sheets cutting operations were closely looked into. Unstructured interviews were initially conducted to uncover the underlying problems, while Direct Observation (DO) and Participative Assessment (PA) methods were utilized to identify ergonomics risk factors. Ergonomics interventions by means of real life experiments were implemented. These included 1) providing semi leather gloves to replace cotton hand gloves, 2) providing plastic chairs with back rest for occasional sitting, and 3) installing a fiberglass rolling mechanism for fiberglass cutting on table top. Post survey incorporating both DO and PA methods was subsequently conducted to gauge its effectiveness in minimizing work-related musculoskeletal disorders and other health problems. This action-oriented study finally produced fruitful results which includedinsignificant low back pain and legs ache, minimized hand irritation sensations, relieved tiredness of operators, reduced nose irritation, eye itchiness, sore throat and dizziness.

Life Cycle Estimation of an Automotive Seat Recliner with LCF Approach

Automotive Seat Recliner is a mechanism that enables seat back rest to move forward and rearward about the pivot point of seat. An upgraded model of recliner with optimized dimensions is modeled so that the effort applied to unlock the mechanism reduces. The modeled Recliner was analyzed in LS Dyna to obtain the input data for fatigue calculations. Coffin Manson fatigue criterion is used to obtain results, which matches the experimental results undergone in lab.

Carbon Fiber Multilayer Loom Let off the Mathematical Model of Control System

Let-off system application of computer and electronic technology, may at any time adjust the loom is likely to change in the process of weaving yarn tension and density, thus improve the quality of the fabric. In this paper, based on the study of the function of the let-off motion, let-off servo control system is established the mathematical model of the warp beam unwinding; According to the carbon fiber Angle of multilayer union loom warp tension requirement, design a set of tension compensation device,and established the mathematical model of back rest. Easy and convenient, the whole control system has better reliability and real-time performance.

An Experiment Based Reach Model for Fighter Cockpit Design

Reach envelope is one of the design tools to ensure industrial workspace accommodates users. As for fighter pilots, their reach capability must be considered during the design of cockpit. Normally fighter seat back rest angle is between 13°and 30°, and due to the fact that postural change affects the reach capability of the pilot, the reach envelope can be different under different seat backrest angle, which is normally ill considered and thus limits the cockpit design. This research employed a reach envelope transformation model based on the anthropometric measurement approach to transform experiment based reach envelope at 0° of back rest angle to that at other seat back rest angles. 12 male subjects’ Reach data under 4 different seat angles and other anthropometric data were collected using motion capture system with a sample rate of 120Hz. A simplified model of human body was introduced and modified using the captured data from 4 subjects, with which other subject’s reach points at 0° seat backrest angle were transformed to reach points at other seat backrest angles. Comparison between the transformed envelope and measured reach envelope indicated that the average of difference, SD of difference was -5.5 and 42.76(mm) respectively.

Analysis on Warp’s Frictional Movement in the Heald Eye during Weaving Process

Currently the abrasion and breakage of warp during the weaving process have become the key issue in high-speed weaving of non-shuttle looms. According to the experiment, the heald frame is the main zone where warp abrades. With the multiple effects of shedding and beating up, warp will make a frictional movement every time one weft is weaved, no matter which opening mode is used. These frequent frictional movements will cause warp’s surface damage, which leads to breakage. Therefore warp’s frequent frictional movement in the heald eye is the main factor causing warp’s breakage. By theoretically analyzing warp’s front and back elongation and tension while beating up, this paper establishes the formula of warp’s movement in the heald eye, and discusses the effect of weaving parameters on this movement, such as looming tension, warp line, opening time and geometric shedding size. This provides theoretical basis for solving the frictional issue reasonably. According to the result, by forming the shed with big tension, high back-rest, late shedding, long shed, fast opening and slow closing, the frictional movement of warp in the heald eye can be reduced during the weaving process. In this way, warp’s excessive abrasion can be avoided and its breakage will be lowered, so as to improve weaving efficiency.