A PHYSICAL DEMANDS COMPARISON OF THREE DIRECT-CURRENT RIGHT ANGLE POWER TOOL TIGHTENING STRATEGIES

The purpose of this study was to compare the physical demands associated with three direct-current (DC) right angle power tool tightening strategies. Thirty-six participants (x ̅ = 37.14 years ± 12.03) were assigned to one of two experimental groups: 1) Hard joint (30o, n=18), and, 2) Soft joint (540o, n=18). Within each experimental group, participants performed 36 trials, consisting of 3 tightening strategies, 3 target torques and 4 joint locations, in random order. Data from 3Dlinear sensor handle, motion capture markers, and Borg ratings were analyzed. Repeated measures ANOVA with Tukey’s post hoc test were used to determine statistical significance (p\u3c0.05). Participants operating the TurboTight® fastening strategy experienced the least forces at the hand-handle interface, least joint angle displacements (shoulder & elbow angular displacement) as well as reported the lowest ratings of discomfort and strength

Investigation on the Effects of Fastening Parameters on the Handle Displacement of a Pistol Grip Tool

Workers in automotive assembly lines routinely use DC-powered pistol grip tools to install threaded fasteners. While these tools are easy to use and increase production quality, tool operators are subjected to impulsive reaction torques that produce forceful rotary displacement of the tool handle. While operators try to resist this reaction, forces exerted by the forearm muscles are often insufficient, thereby producing eccentric contractions. Repeated exposure to such forces is known to cause tendonitis, fatigue, and physical stress. The objective of this study was to investigate the operational parameters and optimize conditions that minimize the tool handle displacement. A deterministic approach was considered to identify the system parameters. The tool-operator system was mathematically represented using a single degree-of-freedom torsional model. An in-vivo study of 10 experienced workers was conducted to estimate the typical ranges of operator stiffness. Tightening tasks were performed at 3 torques (5, 7.5, 10 Nm), and 4 fastener locations that correspond to varying orientations of the wrist. The mean operator stiffness was found to be 1.11 kN/m. A pistol grip tool simulator was designed and developed to emulate the dynamics of tightening operation without the use of human operators. A slider-crank mechanism was considered to represent the kinematics of the torsional system, and a pneumatic actuator was used to represent individual operator stiffness. A parametric study observed the effects on tool handle response due to varying torque, operator stiffness, spindle speed, fastener material, drive style, and fastener head type. Results showed that an increase in applied torque (5–7.5 Nm) also increased the angular displacement of the tool handle (42.2°–58.5°). Variation in stiffness resulted in an inverse effect on the handle response. At 7.5 Nm, it was observed that wrist ulnar deviation produced the most handle displacement (59.2°), whereas wrist flexion produced the least (57.3°). Variation in the operational speed of tool spindle showed no significant effect on the handle displacement. Three fastener materials, alloy steel, stainless steel, and brass were tested. It was observed that alloy steel resulted in the least displacement (65.4°), whereas brass produced the most (85.7°). Between the two drive styles, it was observed that a Hex drive produced significantly higher response (69.9°) than a Torx Plus drive (63.4°). Button Head fasteners produced significantly higher response (76.2°) compared to Flat Head fasteners (66.9°). Based on this data, it was concluded that the designed pistol grip tool simulator can be used to investigate and optimize the operational parameters such as tool tightening algorithm, fastener types, and task locations, thus minimizing the tool handle displacement and mitigating forearm strain injuries

Relationship Between the Ground Reaction Forces and the Forces Exerted by the Hands During Automotive Tasks.

The purpose of this study was to determine the strength of the relationship between the ground reaction forces (GRF), forces directly recorded at the feet and the force exerted by the hands as measured at the hands, during simulated work-related tasks, in an effort to understand the validity of GRF measurements as an accurate alternative indirect measurement of physical hand efforts. Thirty healthy participants were recruited between the ages of 18-60 years with no history of pain or injury in their upper and lower extremities for the previous six months. A total of seven manual hand exertion tasks were simulated and their associated force efforts were obtained. Six of the seven task efforts was completed with and without the ability of the participants to brace themselves while the last task was only completed without a brace. The brace is an external object that was placed between the participant and the vertical force plate. Root Mean Squared Error (RMSE) was calculated to find the percentage error between forces recorded at the hands and the forces measured at the feet. Results revealed that without Brace tasks often resulted with a significantly lower RMSE compared to Bracing tasks, the Drilling task was found to have the smallest RMSE while the Electrical Connector task showed the highest RMSE, and an increase in RMSE was evident with tasks requiring repetitive/wiggly movements (Hose and Weather-Strip tasks)

Demanufacturing metrics for industrial fasteners and disassembly process

As the society progresses towards ecological maturity, the issue of reducing the environmental burden imposed by used products becomes increasingly important Environmental issues are becoming increasingly relevant for product designers and manufacturers. Public awareness of the value and fragility of an intact ecology is constantly growing, and the traditional assumption that the cost of ecological burdens to be shared by a society, as a whole is no longer accepted. Environmental protection legislation requiring manufacturers to take back and recycle used products will be a commonplace throughout Europe and the U.S. in the near future. Demanufacturing involves separating and disassembling a \u27product\u27 into its smaller \u27subassemblies\u27 and \u27components\u27. Unfastening carries out the physical separation itself and other separation techniques are also used to separate the unfastened component. There are two types of Disassembly methods they are destructive disassembly and non-destructive. The term \u27product\u27 means a complete entity, such as an automobile, a washing machine, etc. \u27Sub-assembly\u27 refers to a product .A \u27component\u27 is a subassembly that cannot be disassembled any further. The principle aims and objectives of this research are to analyze the mechanical aspects of demanufacturing a component with respect to fasteners and disassembly Processes. This research involved developing Disassembly Effort Index Metrics (DEIM) for a wide variety of industrial fasteners, destructive and non destructive disassembly processes. The industrial Fasteners were separated into four categories i.e. One Piece Fasteners, Two Piece Fasteners, Integral Fasteners and Miscellaneous Fasteners. They were analyzed with respect to the accessibility of a fastener with respect to the part, tools necessary to disassemble them, time needed to unfasten them, part hold and fixturing issues ,forces needed to unfasten them and instructions to the dissemblers to dissemble the fastener. A scoring pattern was developed. The Disassembly Processes were categorized into Non-Destructive Disassembly and Destructive Disassembly. The Non-Destructive Disassembly methods like Magnetic Separation, Suction and Drainage, Self Removal, Separation of both Fastened and Unfastened Components, and only two of the Destructive Disassembly methods i.e. Weld Breakage and Impact breakage were analyzed using Disassembly Effort Index Metrics (DEIM) parameters. The DEIM parameters, for the Disassembly Processes are, time needed to disassemble the component, tools needed to separate them, Forces (both human and Machine), Part hold , Process Instructions and Hazard Tools. The scoring pattern was developed

Development and Application of a Portable System to Reliably Measure Grip Forces Using Thin-Film Force Sensors

Accurate tracking of hand grip force is an important consideration needed for a robust understanding in the study of human biomechanics. One aspect where it proves useful is in hand-arm vibration, such as from gripping a power tool. Depending on how firmly the user is gripping the tool, they may change their exposure levels to the tool vibration, which can lead to potential disorders such as Hand-Arm Vibration Syndrome (HAVS). A small, battery powered portable force unit has been developed to supply power to, and condition, the signals from eight thin-film force sensors. This gives a better understanding of the grip force used on many different tool applications that were previously immeasurable. Using this information, knowledge can be gained in determining how much of a role grip force plays in the onset of the aforementioned disease. Using the portable force unit, two different applications are explored. The first uses an instrumented handle in conjunction with thin-film sensors to ascertain how well the thin-film sensors model the overall grip strength recorded by the handle. Using varying numbers of sensors to map the hand, a conversion factor was determined to calculate the actual grip force represented by the waveforms of the thin-film sensors. The observed results of this experiment indicated that the use of eight to four thin-film force sensors yield conversion factors that are similar, therefore using four sensors gives a similar estimated force response, while minimizing sensor bulk. The second application is in field work. Several grip force measurements were made in the field while subjects were using pneumatic power tools. A subject calibration of the thin-film sensors was performed using the same instrumented handle mentioned previously and the unit allowed for the thin-film sensors to be used in the actual tool use measurement. Using the conversion factors from the laboratory on the data collected in the field, a better understanding of grip force was obtained. This understanding is from a real work environment rather than a laboratory tool simulation conducted by lab personnel unfamiliar with the tool, which could bias the results. Applying this method of tracking grip force is expected to provide a better understanding of how grip force plays a role in HAVS and how tool handle designs can be improved

Feasibility of remotely manipulated welding in space. A step in the development of novel joining technologies

In order to establish permanent human presence in space technologies of constructing and repairing space stations and other space structures must be developed. Most construction jobs are performed on earth and the fabricated modules will then be delivered to space by the Space Shuttle. Only limited final assembly jobs, which are primarily mechanical fastening, will be performed on site in space. Such fabrication plans, however, limit the designs of these structures, because each module must fit inside the transport vehicle and must withstand launching stresses which are considerably high. Large-scale utilization of space necessitates more extensive construction work on site. Furthermore, continuous operations of space stations and other structures require maintenance and repairs of structural components as well as of tools and equipment on these space structures. Metal joining technologies, and especially high-quality welding, in space need developing

Preliminary evaluation of joining Al-PEEK via through hole extrusion welding

The guideline for future automotive and structural application is to reduce the weight with high performance in terms of mechanical resistance. In automotive field this has an additional benefit that is related to the environmental issues that are becoming increasingly stricter. The competitiveness in this industrial field will be guaranteed through hybrid solutions which involve lightweight metals and engineering polymers. Different joining techniques between dissimilar materials were already proposed and established, but sometimes these methods are not very effective. The purpose of this work is to introduce a preliminary evaluation of a new approach to join dissimilar materials. THEW (Through Hole Extrusion Welding) is the new tested joining technique for dissimilar materials. The process consists to extrude the viscoplasticised aluminum alloy through an extrusion die to soften, penetrate, and pressurise the polymer component. The aluminum alloy is brought to the condition of viscoplastic through the stirring effect due to the probe used for this technology. At the same time the shoulder guarantees a total closure of the welding surface and a forging action on the welding region. The penetration of the aluminum will cause a pressurisation and a consequent upward flow of the polymer ensuring the formation of the so called “Crab Claw” joint. The most important involved joining mechanisms are mechanical interlocking and adhesive bonding. The material involved for the final version of the THEW joint are AA5754-H111, PEEK and Ti Gr 1 with a respective thickness of 5 mm, 5 mm, and 0.6 mm. To implement this new kind of dissimilar materials joining technique an experimental plan is made involving the design of new tools, process parameters and clamping system. Different set of tools and process parameters are tested on different base materials. After the experimental phase, a best set of preliminary process parameters, tools and base materials are selected. The process is also implemented for non-linear paths and in a double side version. Mechanical, microstructural, and macrostructural tests are used to analyse the joint from different point of views (mechanical, geometric, and microstructural point of view). The results are analysed and commented to do appropriate analyses on the possible impact of this new joining technique

Research on the System Safety Management in Urban Railway

Nowadays, rail transport has become one of the most widely utilised forms of transport thanks to its high safety level, large capacity, and cost-effectiveness. With the railway network's continuous development, including urban rail transit, one of the major areas of increasing attention and demand is ensuring safety or risk management in operation long-term remains for the whole life cycle by scientific tools, management of railway operation (Martani 2017), specifically in developed and developing countries like Vietnam. The situation in Vietnam demonstrates that the national mainline railway network has been built and operated entirely in a single narrow gauge (1000mm) since the previous century, with very few updates of manual operating technology. This significantly highlights that up to now, the conventional technique for managing the safety operation in general, and collision in particular, of the current Vietnamese railway system, including its subsystems, is only accident statistics which is not a scientific-based tool as the others like risk identify and analyse methods, risk mitigation…, that are already available in many countries. Accident management of Vietnam Railways is limited and responsible for accident statistics analysis to avoid and minimise the harm caused by phenomena that occur only after an accident. Statistical analysis of train accident case studies in Vietnam railway demonstrates that, because hazards and failures that could result in serious system occurrences (accidents and incidents) have not been identified, recorded, and evaluated to conduct safety-driven risk analysis using a well-suited assessment methodology, risk prevention and control cannot be achieved. Not only is it hard to forecast and avoid events, but it may also raise the chance and amount of danger, as well as the severity of the later effects. As a result, Vietnam's railway system has a high number of accidents and failure rates. For example, Vietnam Rail-ways' mainline network accounted for approximately 200 railway accidents in 2018, a 3% increase over the previous year, including 163 collisions between trains and road vehicles/persons, resulting in more than 100 fatalities and more than 150 casualties; 16 accidents, including almost derailments, the signal passed at danger… without fatality or casual-ty, but significant damage to rolling stock and track infrastructure (VR 2021). Focusing and developing a new standardised framework for safety management and availability of railway operation in Vietnam is required in view of the rapid development of rail urban transport in the country in recent years (VmoT 2016; VmoT 2018). UMRT Line HN2A in southwest Hanoi is the country's first elevated light rail transit line, which was completed and officially put into revenue service in November 2021. This greatly highlights that up to the current date, the UMRT Line HN2A is the first and only railway line in Vietnam with operational safety assessment launched for the first time and long-term remains for the whole life cycle. The fact that the UMRT Hanoi has a large capacity, more complicated rolling stock and infrastructure equipment, as well as a modern communica-tion-based train control (CBTC) signalling system and automatic train driving without the need for operator intervention (Lindqvist 2006), are all advantages. Developing a compatible and integrated safety management system (SMS) for adaption to the safety operating requirements of this UMRT is an important major point of concern, and this should be proven. In actuality, the system acceptance and safety certification phase for Metro Line HN2A prolonged up to 2.5 years owing to the identification of difficulties with noncompliance to safety requirements resulting from inadequate SMS documents and risk assessment. These faults and hazards have developed during the manufacturing and execution of the project; it is impossible to go back in time to correct them, and it is also impossible to ignore the project without assuming responsibility for its management. At the time of completion, the HN2A metro line will have required an expenditure of up to $868 million, thus it is vital to create measures to prevent system failure and assure passenger safety. This dissertation has reviewed the methods to solve the aforementioned challenges and presented a solution blueprint to attain the European standard level of system safety in three-phase as in the following: • Phase 1: applicable for lines that are currently in operation, such as Metro Line HN2A. Focused on operational and maintenance procedures, as well as a training plan for railway personnel, in order to enhance human performance. Complete and update the risk assessment framework for Metro Line HN2A. The dissertation's findings are described in these applications. • Phase 2: applicable for lines that are currently in construction and manufacturing, such as Metro Line HN3, Line HN2, HCMC Line 1 and Line 2. Continue refining and enhancing engineering management methods introduced during Phase 1. On the basis of the risk assessment by manufacturers (Line HN3, HCMC Line 2 with European manufacturers) and the risk assessment framework described in Chapter 4, a risk management plan for each line will be developed. Building Accident database for risk assessment research and development. • Phase 3: applicable for lines that are currently in planning. Enhance safety requirements and life-cycle management. Building a proactive Safety Culture step by step for the railway industry. This material is implemented gradually throughout all three phases, beginning with the creation of the concept and concluding with an improvement in the attitude of railway personnel on the HN2A line. In addition to this overview, Chapters 4 through Chapter 9 of the dissertation include particular solutions for Risk assessment, Vehicle and Infrastructure Maintenance methods, Inci-dent Management procedures, and Safety Culture installation. This document focuses on constructing a system safety concept for railway personnel, providing stringent and scientific management practises to assure proper engineering conditions, to manage effectively the metro line system, and ensuring passenger safety in Hanoi's metro operatio

Project for the analysis of technology transfer

The special task of preparing technology transfer profiles during the first six months of 1971 produced two major results: refining a new method for identifying and describing technology transfer activities, and generating practical insights into a number of issues associated with transfer programs