Fixture Unit Research Articles

FIS-based approach to estimate probable flows for sizing pipes in building water supply systems

ABSTRACT The paper presents Fuzzy Inference System (FIS) -based approach to estimating probable flows for sizing building water supply pipes. Instead of calculating the design flow by estimating the number of fixtures operating simultaneously using probabilistic or deterministic approach utilizing a large amount of high-resolution field data, the proposed methodology uses Fuzzy logic to estimate demand characteristics of fixtures, unlike conventional fixture unit method. The developed methodology is based on FISs derived from users’ socio-demographic characteristics, their diurnal activities and water use habits. A MATLAB program was developed to estimate the probable flows through the pipe using inputs-type of accommodation, connected fixture types and fixture flow rates. An imaginary 7-storey residential building with a gravity tank system was considered for pipe sizing. The design flows obtained by the proposed methodology were 50–70% of the those produced by the fixture unit approach leading to smaller pipe sizes.

Residential water demand modelling and hydraulic reliability in design of building water supply systems: a review

Abstract The building water supply system is a fundamental unit in water supply systems as it is directly associated with end users. However, the studies available on its efficient design are limited. Water demand estimation continues to be an important issue in water supply systems' design because of its multifaceted nature. Hunter's curve, or Fixture Unit method, is widely used for estimating the load on plumbing. Regardless of its popularity, it has a few drawbacks and is arbitrarily modified in some plumbing codes. Fixture-use probability, a basic entity in the Fixture Unit and some other methods, is a difficult parameter to estimate. Commonly, high-resolution field data is used for stochastic modelling of residential water demand which may not be always available. The paper reviews important residential water demand models in view of their applicability in building water supply system design. The irregular nature of water demand in buildings is due to uncertainty in water-use behaviour of users at fixture level. Use of soft-computing techniques can provide an advantage over the other methods in modelling such behaviour. The paper also discusses reliability of building water supply systems and applicability of some common indices for estimating reliability of building water supply systems.

最新型大・小便器への器具給水負荷単位の適用の検討(第2報)提案器具給水負荷単位による給水負荷の算定値と実測値の比較

最新型大・小便器への器具給水負荷単位の適用の検討(第2報)提案器具給水負荷単位による給水負荷の算定値と実測値の比較

The Role of Lightweight Design Method in Flexible Fixture Design

To reduce the processing cycle and cost of sheet metal parts, a flexible fixture is designed by light weight method. First, the finite element analysis techniques adopted are summarized. Second, the static and modal analysis of the flexible fixture unit is carried out to obtain the design structure that meets the strength and rigidity requirements. Third, the lightweight design of the base of the positioning clamping unit is carried out after the analysis of the design structure of the positioning clamping unit. The modal analysis results of the positioning clamping unit show that at the operating frequency of 50Hz, the positioning clamping unit designed in this research would not resonate. Lightweight design results obtain the optimal section design parameters, achieve the purpose of reducing the weight of the flexible fixture base structure, and save the cost. Therefore, the results of this study provide a good idea for flexible fixture to adapt to the diversity of mechanical products.

Estimating peak water demand: Literature review of current standing and research challenges

Abstract Since the 1940s, the models used to estimate peak water demand has been based largely upon variations and refinements of the probabilistic ‘fixture unit’ model. An approach originally advanced by Hunter (1940) in the United States of America (USA). Seeking an improved approach to the 'fixture unit' model, now widely recognised as outdated, is the key driving force behind the current work. Boosted by the development of computing power, the plumbing industry, researchers, and academics have, over the last decade, developed computational models as a means of estimating peak water demand. This paper builds on computational models embracing the estimation of peak water demand. A brief outline of the fixture unit and its limitations is provided with key developments in computational modeling comprising current developments from the USA and UK. A brief outline of computational models is presented: Modified Wistort Method (MWM); the Exhaustive Enumeration Method (EEM), and the Water Demand Calculator (WDC). Also presented, from the UK, is the Loading Unit Normalisation Assessment method (LUNA) aimed at an improved model to size domestic hot and cold-water systems. The analysis of the computational models suggests the WDC model is conceivably the most compatible with that of the plumbing industry's design requirements. Suggesting this model could easily be adapted to meet the requirements across international borders. Challenges for the international acceptance of the WDC are the field study requirements to determine p (probability of use) and q (fixture flow rate) values for all types of buildings.

Computer simulation-based analysis of wind load effect on structural capacity of skywalk between Hyatt Regency hotel and multipurpose building complex Iset Tower in Ekaterinburg

This article contains a computer - aided analysis of bearing capacity under wind load for a standard attachment fixture which one is most frequently used for mounting transparent structures. The analysis results of peak positive and negative wind loads acting on the enveloping structure are presented. The stress-strain state of the skywalk facade fixture unit in the elastic strain stage is analyzed. Maximal values of force influence on the plastic deformation of the fixture unit components arise. They are determined on the basis of a nonlinear analysis. The object of the research is a skywalk between the Hyatt Regency hotel building and the Iset Tower high-rise building in Ekaterinburg that is being designed currently. Simulation models and computational experiments were made in ANSYS CFX software complex.

器具給水負荷単位の適用の検討 （第1報）節水型大・小便器への器具給水負荷単位の適用

器具給水負荷単位の適用の検討 （第1報）節水型大・小便器への器具給水負荷単位の適用

A case-based reasoning approach for design of machining fixture

Appropriate fixture design could lower process time, lower cost, and improve the quality of products. This paper proposes a case-based reasoning (CBR) method, with improved indexing and retrieving approaches which are critical issues in machining fixture design systems. A case storage for fixture design case indexing approach is developed so that the database is constructed into two levels—to manage and categorize numerous related fixture designs. The data includes existing workpieces and associated fixture planning and unit depository as solutions. Based on this approach, a CBR method with a two-step case retrieval is presented. The objective is to improve searching results in database for machining fixture design. In this CBR-based fixture design method, the appropriate workpiece in the first level of database by using design requirement is found. Then, the proper conceptual fixture design can be achieved by retrieving related fixture case from the second level. This method facilitates the fixture designing by means of referencing past design cases to generate a conceptual fixture design quickly and easily. It also helps in the finishing design by suggesting some alternative fixture cases. Finally, several case studies are used to validate and present the applicability and usability of the proposed approach.

An intelligent fixture design method based on smart modular fixture unit

Fixture is an important assisting resource for manufacturing. Its design is under the combined influence of workpiece, machining methods, material performances, etc. and demands rich experience of the designer, which leads to significant increase in design cycle and costs. This paper researches on a new automatic fixture design methodology based on inheriting and reusing design knowledge. Traditional fixture model is changed to smart fixture model, which is not only a geometric model but also appending geometric knowledge, process planning knowledge, and performance knowledge. On the other hand, the ontology of workpiece’s machining requirement is established for driving smart fixture automatically. Based on the above ontology, the self-selection reasoning method is proposed, for machining planner, which can push unit selection scope and drive its size actively. To drive fixture unit assembly automatically, the self-assembly reasoning method is proposed according to typical feature’s assembly mode. By these ways, the geometric consistency among units as well as unit/workpiece is maintained. In the end, design efficiency and quality is expected to be improved more automatically.

FINITE ELEMENT MODELLING AND ANALYSIS OF WORKPIECE-FIXTURE SYSTEM

The fixture design and analysis lead-time is always a major influencing factor for the bottleneck between product design and manufacturing. With advent analysis and simulation tools, there is a lot of potential to expand the scope of optimization of fixture elements to achieve the objectives such as ‘maximizing rigidity’ and ‘minimizing weight’ of a fixture assembly. There are many sources which affect the rigidity of fixture assembly. The rigidity of fixture assembly mainly depends upon various factors such as material properties, geometry of individual components, stability against thermal distortions, clearances or plays on fixture elements (to facilitate loading and unloading of workpiece), contact deformations at contacting surfaces, etc. Among these, contact deformations at contact interface are one of the important sources of errors in precision fixture design. These contact deformations are measure of contact stiffness and therefore needed to be studied in accordance with workpiece-fixture contact. In this paper, a numerical model of fixture unit assembly is presented using the FEA tool ANSYS. ANSYS contact elements CONTA175 (8 node element) and TARGE170 (8 node quadrilateral element) are utilized to represent contact stiffness at contact interface. This model simulates the behavior of contacting surfaces of fixture assembly for different values of surface roughness, coefficient of friction (μ) and contact stiffness with very little modelling or computational efforts and time. This work establishes the FEA model of fixture unit assembly to predict fixture unit stiffness and FEA model of rough surface contact to predict contact stiffness. Based on this study, the database of fixture stiffness and contact stiffness is built up and further can be used in computer aided fixture design (CAFixD).

The study of fixture stiffness part I: a finite element analysis for stiffness of fixture units

This paper presents a systematic finite element model to predict the fixture unit stiffness by introducing nonlinear contact elements on the contact surface between fixture components. The contact element includes three independent springs: two in tangential directions and one in the normal direction of the contact surface. Strong nonlinearity is caused by possible separation and sliding between two fixture components. The problem is formulated by the penalty function method and is solved by the modified Newton--Raphson procedure. The model was validated by two cases of analysis of a linear cantilever beam and a simple fixture unit with two components. Results are in agreement with the corresponding analytical solution of beams and the previous experiment results for fixture in the literature.

A Finite Element Analysis For Stiffness of Fixture Units

This paper presents a systematic finite element model to predict the fixture unit stiffness by introducing nonlinear contact elements on the contact surface between fixture components. The contact element includes three independent springs: two in tangential directions and one in the normal direction of the contact surface. Strong nonlinearity is caused by possible separation and sliding between two fixture components. The problem is formulated by the penalty function method and is solved by the Newton-Raphson procedure. The model was validated by two cases of analysis of a linear cantilever beam and a simple fixture unit with two components. The results are in agreement with the corresponding analytical solution of beams and the previous experimental results for fixture in the literature.

Design of test fixtures for electron‐beam tree experiments

Abstract In this paper, we discuss the experimental problems and radiation noise sources associated with flash X-ray machine (FXR) and linear accelerator (LINAC) electron-beam TREE experiments. Special testing techniques and test fixture design guidelines are presented. Wiring diagrams for a properly designed general-purpose electron-beam test fixture and control unit are shown, in addition to photographs which illustrate the geometry-dependent shielding and noise reduction techniques. Techniques for improving both electron radiation shielding and RF shielding efficiencies are represented.