8,741 research outputs found
Fatigue evaluation in maintenance and assembly operations by digital human simulation
Virtual human techniques have been used a lot in industrial design in order
to consider human factors and ergonomics as early as possible. The physical
status (the physical capacity of virtual human) has been mostly treated as
invariable in the current available human simulation tools, while indeed the
physical capacity varies along time in an operation and the change of the
physical capacity depends on the history of the work as well. Virtual Human
Status is proposed in this paper in order to assess the difficulty of manual
handling operations, especially from the physical perspective. The decrease of
the physical capacity before and after an operation is used as an index to
indicate the work difficulty. The reduction of physical strength is simulated
in a theoretical approach on the basis of a fatigue model in which fatigue
resistances of different muscle groups were regressed from 24 existing maximum
endurance time (MET) models. A framework based on digital human modeling
technique is established to realize the comparison of physical status. An
assembly case in airplane assembly is simulated and analyzed under the
framework. The endurance time and the decrease of the joint moment strengths
are simulated. The experimental result in simulated operations under laboratory
conditions confirms the feasibility of the theoretical approach
Underreamer mechanics
In the oil and gas industry, an underreamer is a tool used to extend and enlarge the diameter of a previously-drilled bore. The problem proposed to the Study Group is to obtain appropriate mathematical models of underreamer dynamics, in forms that will lead to feasible computation. The modes of dynamics of interest are torsional, lateral and axial.
This report describes some initial models, two of which are developed in more detail: one for the propagation of torsional waves along the drill string and their reflection from contact points with the well bore; and one for the dynamic coupling between the underreamer and the drill bit during drilling
Monitoring of the BTA Deep Hole Drilling Process Using Residual Control Charts
Deep hole drilling methods are used for producing holes with a high lengthto- diameter ratio, good surface finish and straightness. The process is subject to dynamic disturbances usually classified as either chatter vibration or spiralling. In this work, we propose to monitor the BTA drilling process using control charts to detect chatter as early as possible and to secure production with high quality. These control charts use the residuals obtained from a model which describes the variation in the amplitude of the relevant frequencies of the process. The results showed that chatter is detected and some alarm signals are related to changing physical conditions of the process. --
Methodology for qualifying a Friction Stir Welding equipment
The objective of this research work is the industrialization of the friction stir welding process in order to provide tools to industrials to select and qualify a machine for their FSW applications. This paper presents a methodology to determine the Friction Stir Welding equipment adequate to an application. The adequate equipment can be every machine that can perform friction stir welds. This paper presents a short review, based on literature survey, of the existing friction stir welding equipments. Then, the methodology developed is presented. It is based on the studying of the interactions between the tool and the workpiece
Predictive model of the human muscle fatigue: application to repetitive push-pull tasks with light external load
Repetitive tasks in industrial works may contribute to health problems among
operators, such as musculo-skeletal disorders, in part due to insufficient
control of muscle fatigue. In this paper, a predictive model of fatigue is
proposed for repetitive push/pull operations. Assumptions generally accepted in
the literature are first explicitly set in this framework. Then, an earlier
static fatigue model is recalled and extended to quasi-static situations.
Specifically, the maximal torque that can be generated at a joint is not
considered as constant, but instead varies over time accordingly to the
operator's changing posture. The fatigue model is implemented with this new
consideration and evaluated in a simulation of push/pull operation. Reference
to this paper should be made as follows: Sakka, S., Chablat, D., Ma, R. and
Bennis, F. (2015) 'Predictive model of the human muscle fatigue: application to
repetitive push-pull tasks with light external load', Int
Tribological aspect of lubrication in form tapping of high strength steel
Collaboration avec le LTDSThis study aims at analyzing the tribochemical mechanisms of lubrication during the process of form tapping and consequently optimizing the formulation of the lubricant. In order to correlate the tribochemical reactions with the performance of a lubricant, we measure the alteration of tapping torque according to ASTM D5619 standard. The objective of the study also relates to the identification of the additives and the association of their properties to the performance of lubrication. The goal is to characterize the nature of the tribofilm created at the bottom of the threads which is the zone the most severely affected by the working tool. X-ray Photoelectron Spectroscopy (XPS) is used to characterize the surface of formed threads. This study demonstrates a link between the sulphur reactions on the metallic surface and the friction reducing performance of lubricant during form tapping.Thèse CIFRE TOTA
A Similarity-Based Prognostics Approach for Remaining Useful Life Prediction
Physics-based and data-driven models are the two major prognostic approaches in the literature with their own advantages and disadvantages. This paper presents a similarity-based data-driven prognostic methodology and efficiency analysis study on remaining useful life estimation results. A similarity-based prognostic model is modified to employ the most similar training samples for RUL estimations on each time instance. The presented model is tested on; Virkler’s fatigue crack growth dataset, a drilling process degradation dataset, and a sliding chair degradation of a turnout system dataset. Prediction performances are compared utilizing an evaluation metric. Efficiency analysis of optimization results show that the modified similarity-based model performs better than the original definition
The Development of a Technological Processor as a Part of a Workpiece Programming System
The cost of turning on NC-lathes is substantially sensative to cutting conditions. The use of optimum cutting conditions is limited by a large number of constraining factors such as chip disposal, chucking possibility, available power, required accuracy etc. The present way of work preparation, even when using the available workpiece programming systems, does hardly allow of generating acceptable values for the cutting variables. Moreover, the combination of geometrical and a technological processor in one workpiece programming system will save substantial time in work preparation.\ud
Starting from a former reported development, this article deals with the development of a technological processor of improved design and extended possibilities, as for instance the handling of the chucking problem, as a part of a complete workpiece programming system. At choice the output of this processor may be presented in graphes, showing the limited working area and indicating the preferential working point.\ud
Another feature is the possibility of automatic tool selection by comparing the working area of the machine tool with the working areas of the different potential tools.\ud
The overall system design is modular and well structured to further portability and flexibility
Machinery, equipment and tools: A compilation
A selection of new hand tools, modifications of existing tools, and techniques developed in the course of NASA research and development project is presented. The items are presented in two sections: Power Hand Tools and Accessories, and Manual Hand Tools and Accessories
Hand tools: A complization
Technical information is provided for recent developments in hand tools for assembly and disassembly application, for materials finishing, and for inspection, analysis, and testing. Photographs or diagrams accompany each description and patent information is included with several articles
- …