Mathematical modeling and vibration simulation of an orbital sander

Numerous epidemiological studies have shown that operators who use hand-held power tools are prone to develop hand-arm vibration syndrome. Therefore, it is necessary to reduce the tool vibrations to protect the worker’s health. This research focuses on the dynamic modeling and the vibration simulation of orbital sanders which are commonly used in industrial sectors. The mathematic model with eighteen degrees-of-freedom (DOF) of this machine is established based upon the Lagrange equation. The experiments are also conducted to test vibrations at the top of the housing where the operators hold the machine. The simulated results are found in good coincidence with the experimental results, and the errors between the experimental results and the simulated values are in acceptable range, which demonstrates the mathematic model in this paper is accurate

Ergonomic Evaluation of Occupational Tasks in a Sofa Making ‎Workshop Based on KIM and Presentation of Corrective Actions

Aims: Manual tasks and load carrying and handling are the most important tasks in a sofa making workshop. Evaluation of these types of tasks is very important for identifying the health risks to which workers are exposed. The aim of this study was the ergonomic evaluation of occupational tasks in a sofa making workshop based on KIM and presentation of corrective actions. Instruments and Methods: The present descriptive cross-sectional study was conducted in a sofa making workshop in Ardabil in 2017. All tasks of the sofa making workers (n=22) were examined, among which 7 main tasks were identified. The identified tasks were analyzed, using KLM-MHO and KLM-LHC methods. Manual tasks and load lifting and carrying tasks were evaluated, scored, and checked out, using EXCELL 2010. Findings: Among the tasks examined, the tasks of woodcarving, preparation for coloring, and sofa dressing showed the highest final score (Risk Grade 4), followed by jointing wood parts with glue and coloring (Risk Grade 3). Most items with high workload were related to grips status, repetitive movement in the hand-finger area, position and repetitive movements of the joints at the end of motion range, and curved forward trunk posture. Conclusion: In carving, preparation for coloring, and dressing tasks, the amount of workload is high. In jointing wood parts with glue and coloring tasks, the amount of workload increases dramatically. And, in designing layout on wood and cutting tasks, the amount of load increases

Stretching exercise to reduce musculoskeletal pain among x bakery’s workers

X bakery has 51 workers and produces approximately 60.000 pieces of bread in a day for nine working hours. Most of the production activities are manually handled and only. The low-level musculoskeletal pain reported by 92% of packaging workers. This study aims to analyze the effectiveness and ideal duration of stretching exercise in reducing musculoskeletal disorders (MSDs) among workers. Using quasi-experimental design, 51 workers involved as respondents who were asked to do a simple stretching exercise in specific duration, five days a week in at least 4 weeks. The MSDs score were measured using the nordic body map (NBM) questionnaire. Intervention divided into 4 categories based on the duration. There is lower level of musculoskeletal pain among all exercise group in average, but comparison test doesn’t show a significant difference compared to control group (p-value=0.232). The group with 15 minutes exercise is the only group that significantly difference compared with the control group (p-value=0.020). The workers with 15 minutes stretching exercise, five days a week tend to have 5.16 % lower level of musculoskeletal pain compared to the control group. Another type of exercise and various durations might be needed as comparison to obtain more representative result

VIBRATION DOSAGE FOR HANDHELD POWER TOOLS BASED ON EXPOSURE-RESPONSE RELATIONSHIP FOR WHITE FINGER DISEASE

Power-tool vibrations can cause a variety of health disorders, ranging from inconsequential to disastrous. These vibrations may not be harmful when received in small doses but can cause vasospastic disorders, such as vibration-induced white finger disease (VWF), with frequent use or accumulated over time. Existing occupational guidance does not adequately describe the health risks associated with power-tool vibrations. In the current study, vibration levels for major brands of reciprocating saws and impact drivers were measured under typical use conditions, along with user comfort levels after different usage times. Results are provided in terms of acceleration and comfort levels as a function of usage time, varied grip-force conditions, and with or without use of gloves. Based on the VWF-incidence data from prior occupational studies, guidance on restrictions on usage of power tools is provided. It is found that existing ISO guidance for Europe overestimates allowable times, compared to those determined here

Estudo do comportamento dinâmico de pratos de lixagem

Mestrado em Engenharia MecânicaO fenómeno de vibrações está intimamente presente no nosso dia-a-dia. Um fenómeno que se revela importante, seja ao pegar num instrumento musical, ao ligar uma coluna de som ou até ao utilizar um telemóvel. No entanto, estas também são responsáveis por efeitos indesejados, especialmente em dispositivos mecânicos manobrados por um utilizador, cujo corpo absorve estas vibrações, podendo vir a conduzir a lesões ou patologias graves. Nesta dissertação, o objetivo passa por estudar o comportamento din âmico de pratos de lixagem, um constituinte muito relevante no que toca a operações de lixagem recorrendo a lixadoras orbitais. Para isso, recorreu-se a uma análise modal de dois pratos, de forma a poder comparar o seu comportamento. A análise modal descreve essencialmente o comportamento dinâmico de um sistema a partir dos seus modos de vibração e das suas frequências naturais. Estes foram obtidos a partir de uma abordagem experimental e também utilizando simulações numéricas que recorrem ao método de elementos nitos. Tendo em conta toda a vertente de escoamento presente nestes pratos e, de forma a complementar o estudo dinâmico, simulações numéricas do escoamento foram também efetuadas de forma a descrever o comportamento destes em termos globais de forma o mais completa possível. Para a análise modal numérica é utilizado o Femap em conjunto com o seu processador Nastran, sendo esta complementada com uma análise experimental recorrendo a um vibrómetro laser e um excitador eletromecânico. Para o estudo do escoamento, é utilizado o módulo CFD do Autodesk.The phenomenon of vibrations is intimately present in our day-to-day life. A phenomenon that proves to be important, whether when picking up a musical instrument, connecting a speaker, or even using a mobile phone. However, vibrations are also responsable for unwanted e ects, especially in mechanical devices operated by a user, whose body absorbs these unwanted vibrations, which can lead to enjuries or serious pathologies. In this dissertation, the main objective is to study the dynamic behavior of sanding pads, a very relevant component in sanding operations using orbital sanders. To achieve this, a modal analysis of two pad models was conducted, with the goal of comparing their behavior. The modal analysis essentially describes the dynamic behavior of a system from its modes of vibration and its natural frequencies. These were obtained not only from an experimental approach but also using numerical simulations, which use the nite element method. Taking into account the internal ow present in these pads and, in order to complete the dynamic study, numerical simulations of the internal ow were also carried out in order to describe the behavior of these pads in the most complete way as possible. For the numerical modal analysis, Femap is used and its Nastran processor, which is complemented with an experimental analysis using a laser vibrometer and an electrodynamic shaker. For the ow study, the Autodesk CFD module is used

Dual-Use Space Technology Transfer Conference and Exhibition

This document contains papers presented at the Dual-Use Space Technology Transfer Conference and Exhibition held at the Johnson Space Center February 1-3, 1994. Possible technology transfers covered during the conference were in the areas of information access; innovative microwave and optical applications; materials and structures; marketing and barriers; intelligent systems; human factors and habitation; communications and data systems; business process and technology transfer; software engineering; biotechnology and advanced bioinstrumentation; communications signal processing and analysis; new ways of doing business; medical care; applications derived from control center data systems; human performance evaluation; technology transfer methods; mathematics, modeling, and simulation; propulsion; software analysis and decision tools systems/processes in human support technology; networks, control centers, and distributed systems; power; rapid development perception and vision technologies; integrated vehicle health management; automation technologies; advanced avionics; ans robotics technologies. More than 77 papers, 20 presentations, and 20 exhibits covering various disciplines were presented b experts from NASA, universities, and industry

Advances on Mechanics, Design Engineering and Manufacturing III

This open access book gathers contributions presented at the International Joint Conference on Mechanics, Design Engineering and Advanced Manufacturing (JCM 2020), held as a web conference on June 2–4, 2020. It reports on cutting-edge topics in product design and manufacturing, such as industrial methods for integrated product and process design; innovative design; and computer-aided design. Further topics covered include virtual simulation and reverse engineering; additive manufacturing; product manufacturing; engineering methods in medicine and education; representation techniques; and nautical, aeronautics and aerospace design and modeling. The book is organized into four main parts, reflecting the focus and primary themes of the conference. The contributions presented here not only provide researchers, engineers and experts in a range of industrial engineering subfields with extensive information to support their daily work; they are also intended to stimulate new research directions, advanced applications of the methods discussed and future interdisciplinary collaborations

Defense Technical Information Center thesaurus

This DTIC Thesaurus provides a basic multidisciplinary subject term vocabulary used by DTIC to index and retrieve scientific and technical information from its various data bases and to aid DTIC`s users in their information storage and retrieval operations. It includes an alphabetical posting term display, a hierarchy display, and a Keywork Out of Context (KWOC) display

Graduate course catalog (Florida International University). [2016-2017]

This catalog contains a description of the various policies, graduate programs, degree requirements, and course offerings at Florida International University during the 2016-2017 academic year.https://digitalcommons.fiu.edu/catalogs/1072/thumbnail.jp