Alias Mohd Saman

Assessment of muscle fatigue associated with prolonged standing in the workplace.

Objectives The objectives of this study were to determine the psychological fatigue and analyze muscle activity of production workers who are performing processes jobs while standing for prolonged time periods. Methods The psychological fatigue experienced by the workers was obtained through questionnaire surveys. Meanwhile, muscle activity has been analyzed using surface electromyography (sEMG) measurement. Lower extremities muscles include: erector spinae, tibialis anterior, and gastrocnemius were concurrently measured for more than five hours of standing. Twenty male production workers in a metal stamping company participated as subjects in this study. The subjects were required to undergo questionnaire surveys and sEMG measurement. Results Results of the questionnaire surveys found that all subjects experienced psychological fatigue due to prolonged standing jobs. Similarly, muscle fatigue has been identified through sEMG measurement. Based on the non-parametric statistical test using the Spearmans rank order correlation, the left erector spinae obtained a moderate positive correlation and statistically significant (rs = 0.552, p < 0.05) between the results of questionnaire surveys and sEMG measurement. Conclusion Based on this study, the authors concluded that prolonged standing was contributed to psychological fatigue and to muscle fatigue among the production workers.

Analysis of Time-to-Fatigue for Standing Jobs in Metal Stamping Industry

In metal stamping industry, almost all jobs are practically to be performed in standing position. Standing in a long period of time can lead to muscle fatigue. The objective of this study was to determine time-to-fatigue in the erector spinae, tibialis anterior, and gastrocnemius muscles of twenty production workers in a metal stamping company. The muscles activity was concurrently measured using surface electromyography (sEMG) during beginning, mid, and end of working sessions. Results of study found that gastrocnemius muscle fatigued earlier during all working sessions. In addition, working at the end of working session showed earlier fatigue than the beginning and mid of work days. The study concluded that standing in a long period of time is a cause to muscle fatigue experienced by the production workers.

Effects of prosthesis stem tapers on stress distribution of cemented hip arthroplasty

Aseptic loosening effects are critical issues in encouraging long term stability of cemented hip arthroplasty. Stress shielding is believed to be an important factor that contributes to the aseptic loosening problems. The numerous changes in the prosthesis stem design are intended to minimize the stress shielding and aseptic loosening problems and to improve the long term performance of the implants. In this study, the stress distribution in cemented hip arthroplasty is established using finite element method. The taper of the prosthesis is designed to be 3° at anterior/posterior, 3° at medial/lateral and 10° from wide lateral to narrow medial. Major muscle loads and contact forces are simulated for walking (toe‐off phase) and stair climbing load cases. Effects of prosthesis stem tapers on the resulting stress distribution are investigated. Results show that compressive stress dominates in the medial plane while tensile stress in the lateral plane of the femur. The corresponding stress levels of intact fe...

Assimilating Quality Function Deployment (QFD) with QUEST ® analysis for facility layout redesign of Handwork Section

Quality function deployment (QFD) is a powerful customer-oriented tool to facilitate the customer needs. In this paper, an attempt has been made to examine the applicability of Quality Function Deployment (QFD) as a suitable design management tool for improving facility layout design of small and medium manufacturing industries. For this purpose, a simple case study using QFD has been conducted where survey has been done to collect and verify the expectations of the customer/worker profile for designing the facility layout. This paper presents the integration between QFD approaches with simulation modelling within a facility layout of a Handwork Section; Miyazu (M) Sdn Bhd, located in Shah Alam, Selangor. The department is struggling to locate the incoming parts from the depot since the pickup and drop off buffer is not properly placed, which results to untidy appearance. Quest simulation analysis is found to be very powerful tool that can be used in the design phase. Simulation modelling activity is used in this study since it allows verification of the floor design without having to rearrange the actual physical layout. The case study findings demonstrated that QFD approach is possible to prioritize and implement the new layout solutions at the onset of the design stage before the actual layout implementation.

Computer Simulation Opportunity In Plastic Injection Mold Development for Automotive Part

In development of a plastic injection mold, the goal of the designer is to achieve an optimal mold design with minimum material wastage and time per cycle, yet produces the product without defects and blemishes. To design the mold, the designer can vary the mold design by manipulate the shape of the part and also the runner and the gate locations. As a consequences of the cost involved in mold manufacture is very expensive, trial-and-error experimentation in the design of the mold is not economical. To permeate this problem, the used of CAD/CAE application assisted in design and establish the most optimal mold gating system. This research was conducted by implementing the use of CAD/CAE tools to produce an optimal mold gating design using CATIA and MOLDFLOW applications. The application tremendously assist the designer in resolve the mold with best gating location in producing an automotive plastic part with low defects, fast time-cycle and the most important factor is to reduce the manufacturing cost.

Analysis of muscle fatigue associated with prolonged standing tasks in manufacturing industry

In most assembly lines in manufacturing industry and service occupations, employees may experience pain and discomfort associated with long periods of standing. Prolonged standing tasks in manufacturing industry may lead to musculoskeletal disorders including pain, increased fatigue and stiffness in active muscles. The aims of this study are to determine subjective fatigue experienced by male Malaysian operators in metal stamping industry, and assess muscle fatigue in their lower extremities. Ten production operators of the industry participated in the study. Muscle fatigue has been analyzed using surface electromyography (sEMG) whereby six muscles such as left and right erector spinae muscles, left and right tibialis anterior muscles, and left and right gastrocnemius muscles were simultaneously measured. On the other hand, the subjective fatigue was assessed through questionnaire surveys. Results of questionnaire surveys found that all operators involved in the study reported that they experienced muscle fatigue due to prolonged standing tasks. Result obtained from sEMG measurement shows similar trend with the conclusion derived from surveys. Workers who experienced fatigue recorded a decreased average mean.

Effects of Prosthesis Stem Materials on Stress Distribution of Total Hip Replacement

Bone loss and bone thickening phenomenon occurred due to different stiffness of the implant and femur. Implant with stiffer materials than the bone carries majority of the load and it transferred down along the implant till the distal tip of the stem. Both phenomenons contribute to stress shielding and loosening of the prosthesis stem. In this study, the stress distributions in intact femur and THR femur are established using finite element method. The THR femur model consists of cemented hip Ti6Al4V and CoCrMo prosthesis stem implanted inside the femur bone. Effects of different material properties of the prosthesis stem on the resulting stress distributions are investigated. Results shows that the largest discrepancy in stress values between intact and THR femur is predicted along the middle region at both lateral and medial planes. The distal region shows that the calculated stress for both THR femur experienced higher stress magnitude than that of intact femur. The higher stress in THR femur leads to bone thickening at the particular region. The corresponding stress magnitude saturates at 25 MPa for THR femur while intact femur is slightly lower at 22 MPa.

Stress and Strain Distribution in Cemented Total Hip Arthroplasty for Walking Load Case

Aseptic loosening is the critical reason for the failure of the cemented total hip arthroplasty. It occurs due to bone remodeling triggered by stress shielding and cement mantle fracture. In this study, stress shielding and bone thickening phenomenon of the cemented THA femur was analysed using three dimensional finite element method for walking load case. The intact femur is modeled to consist of cortical bone and cancellous bone. The prosthesis stem and bone cement are modeled to be biocompatibility Ti-6Al-4V alloy and polymethyl-methacrylate (PMMA). The maximum principal stress of THA femur is lower than that predicted in intact femur at the middle region which leads to stress shielding problems. While higher stress at the bottom region enhance bone thickening and contribute to prosthesis loosening.