scholarly journals Tolerance Analysis of Mechanical Parts

2020 ◽  
Vol 14 (3) ◽  
pp. 265-272
Author(s):  
Živko Kondić ◽  
Đuro Tunjić ◽  
Leon Maglić ◽  
Amalija Horvatić Novak
Keyword(s):  
Tolerance Analysis ◽  
Case Method ◽  
Worst Case ◽  
Mechanical Parts ◽  
Assembly Tolerance ◽  
Huge Impact ◽  
Quality Of Products ◽  
The One

The determination of tolerances has a huge impact on the price and quality of products. The objective of tolerance analysis is to provide the widest possible tolerance range of parts, without disturbing the functionality of the assembly. Tolerance analysis should be performed during the design process because then there is still the possibility for change. For the purpose of carrying out the analysis, three methods will be used: Worst Case method, Root Sum Square method and Monte Carlo Simulation. Methods are explained through simple examples and applied on the one-way clutch.

scholarly journals The Effect of Process Parameters in Helical Rolling of Balls on the Quality of Products and the Forming Process

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2125 ◽  
Author(s):  
Janusz Tomczak ◽  
Zbigniew Pater ◽  
Tomasz Bulzak
Keyword(s):  
Metal Flow ◽  
Experimental Tests ◽  
Rolling Process ◽  
Helical Rolling ◽  
Forming Process ◽  
University Of Technology ◽  
Quality Of Products ◽  
Skew Rolling

This paper presents selected numerical and experimental results of a skew rolling process for producing balls using helical tools. The study investigates the effect of the billet’s initial temperature on the quality of produced balls and the rolling process itself. In addition, the effect of billet diameter on the quality of produced balls is investigated. Experimental tests were performed using a helical rolling mill available at the Lublin University of Technology. The experiments consisted of rolling 40 mm diameter balls with the use of two helical tools. To determine optimal rolling parameters ensuring the highest quality of produced balls, numerical modelling was performed using the finite element method in the Forge software. The numerical analysis involved the determination of metal flow kinematics, temperature and damage criterion distributions, as well as the measurement of variations in the force parameters. The results demonstrate that the highest quality balls are produced from billet preheated to approximately 1000 °C.

Process Capability Based Tolerance Allocation in Pneumatic Percussive Riveting

2020 ◽  
Author(s):  
Hua Wang ◽  
Jialei Zhang ◽  
Junyang Yu
Keyword(s):  
High Efficiency ◽  
Load Transfer ◽  
Process Capability ◽  
Tolerance Analysis ◽  
Tolerance Allocation ◽  
Hole Drilling ◽  
Case Method ◽  
Pneumatic Hammer ◽  
Worst Case ◽  
Mating Conditions

Abstract Pneumatic percussive riveting is an important way to join the sheet metals. In order to ensure the load transfer and the fatigue performance of riveted joint, the interference of the rivet/hole is strictly specified. The interference of the rivet/hole is highly correlated with the process capability of the pneumatic hammer and the diameter of the pre-hole. It is a critical step to choose the appropriate pneumatic hammer to ensure the interference requirements. Energy per blow of the pneumatic hammer is a proclaimed parameter from the riveting hammer manufacturer. It is difficult for the designer to choose the riveting hammer in practical riveting scheme based on energy per blow. Tolerance analysis is an efficient way to model the manufacturing variation and implement process control. This paper presents the tolerance allocation of the pneumatic percussive riveting based on the process capability of the pneumatic hammer. In order to obtain the designed interferences of the rivet/hole, a tolerance chain is built with the process capability of the pneumatic hammer, the diameter of the pre-hole and the diameter of the rivet shank. The process capability of the pneumatic hammer is represented with the interferences of the rivet/hole after riveting. It is an intuitive parameter for the designer to choose the riveting hammer in practical riveting scheme. The process capability of the pneumatic hammer is obtained from the designed riveting experiments with the pneumatic percussive riveting platform. The diameter of the pre-hole affects the interference of the rivet/hole also. The tolerance for manual hole-drilling should be determined to assure the interference requirements and high drilling operation efficiency simultaneously. The variation of the pre-hole is obtained from the manual drilling experiments and diameter measurements. Different hole-drilling results in different mating conditions between the pre-hole and the rivet. The fit conditions of different pre-holes are modeled and the final interferences after riveting are analyzed. Worst case method and statistical analysis method are two common methods for tolerance analysis. For the manual hole-drilling and the pneumatic percussive riveting, worst case method is employed to analyze the constructed tolerance chain in order to accomplish the interferences of the rivet/hole. The different analyzed dimensions, rivet-hole clearances and pre-hole drilling variation, are investigated respectively. The reported work enhances the understanding of the tolerance allocation for the pneumatic percussive riveting. The interference based process capability of the pneumatic hammer provides good reference for pneumatic hammer choosing in riveting scheme. The reported tolerance chain of the interference could be used for the tolerance determination of manual hole-drilling with good quality and high efficiency.

Short-term Measurements of Indoor Environmental Quality in Selected Offices – Case Study

2017 ◽  
Author(s):  
Ludmila Meciarova ◽  
Silvia Vilcekova ◽  
Eva Kridlova Burdova ◽  
Ilija Zoran Apostoloski ◽  
Danica Kosicanova
Keyword(s):  
Environmental Quality ◽  
Indoor Air ◽  
Indoor Environmental Quality ◽  
Indoor Climate ◽  
Climate Conditions ◽  
Healthy Environment ◽  
Health And Wellbeing ◽  
The One

Decent quality of indoor air is important for health and wellbeing of building users. We live, work and study in indoors of various types of buildings. Often people are exposed to pollutants at higher concentrations than these that occur out-doors. Continual investigation of indoor air quality is needed for ensuring comfort and healthy environment. Measuring and analysis of occurrence of physical, chemical and biological factors is the first step for suggestion of optimization measures. Inside school buildings there are often inadequate indoor climate conditions such as thermal comfort parame-ters or ventilation. The aim of this study was determination of indoor environmental quality in selected offices in the building of elementary school in Slovakia. The values of operative temperature were not within the optimum range of values for the warm period of the year in one of the monitored offices. The intensity of illumination was lower in the two offices. Low levels of particulate matters were measured except the one office where permissible value was exceeded by 7.6%.

scholarly journals Experimental Testing of Reinforced Concrete Deep Beams Designed by Strut-And-Tie Method

2020 ◽  
Vol 10 (18) ◽  
pp. 6217
Author(s):  
Anka Starčev-Ćurčin ◽  
Andrija Rašeta ◽  
Mirjana Malešev ◽  
Danijel Kukaras ◽  
Vlastimir Radonjanin ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Experimental Testing ◽  
Deep Beams ◽  
Simply Supported ◽  
Strut And Tie ◽  
The Third ◽  
Variation Parameter ◽  
The One

The aim of the research presented in this paper is the experimental confirmation of the numerically defined shapes of the Strut-and-Tie models, designed according to the EN 1992-1-1 recommendations, and obtained from the software “ST method”. Three reinforced concrete deep beams with openings were tested. Each of them had the same dimensions and quality of the material characteristics. The specimens, constructed as simply supported beams, were loaded with two concentrated forces and were tested for bending until failure. Each specimen was reinforced with different reinforcement layout determined by variation parameter β, incorporated in the software “ST method”. For the determination of the Strut-and-Tie models, all of the reinforcement layouts were equally favored in the first specimen (β = 1.0 for 0°, 45°, and 90°), only the horizontal direction was favored in the second (β = 1.0 for 0°), while in the third specimen the one at the angle of 45° (β = 1.0 for 45°). Based on the results of experimental research, it was concluded that the behavior of loaded members was in agreement with the proposed shapes of the Strut-and-Tie models that were used for their design, and it was confirmed that the program “ST method” can be used for obtaining Strut–and-Tie models.

A New Tolerance Analysis Method for Designers and Manufacturers

1987 ◽  
Vol 109 (2) ◽  
pp. 112-116 ◽  
Author(s):  
W. H. Greenwood ◽  
K. W. Chase
Keyword(s):  
Tolerance Analysis ◽  
New Method ◽  
Analysis Method ◽  
Worst Case ◽  
Assembly Tolerance ◽  
Naturally Occurring ◽  
Methods Of Analysis

Even when all manufactured parts for an assembly are produced within limits, these parts still may not assemble properly if the assembly tolerance analysis was inadequately performed. Naturally occurring shifts in a process can produce biased distributions which can result in increased assembly problems and a greater number of rejects than anticipated. The most common methods of analysis of assembly tolerance buildup are worst case and root sum squares. The limitations of each of these methods are discussed and a simple new method is proposed which accounts for expected bias. This new method includes both worst case and root sum squares as extreme cases.

CAD-Based Tolerance Analysis in Preliminary Design Stages Enabling Early Tolerance Evaluation

2018 ◽  
Author(s):  
Stefan Goetz ◽  
Benjamin Schleich ◽  
Sandro Wartzack
Keyword(s):  
Tolerance Analysis ◽  
Design Stage ◽  
Preliminary Design ◽  
Design Changes ◽  
Preliminary Design Stage ◽  
Geometric Deviations ◽  
Set Up ◽  
Quality Of Products ◽  
Analysis Models

Associated with manufacturing and assembly processes, inevitable geometric deviations have a decisive influence on the function and quality of products. Therefore, their consideration and management are important tasks in product development. Moreover, to meet the demand for short development times, the front-loading of design processes is indispensable. This requires early tolerance analyses evaluating the effect of deviations in a design stage, where the product’s geometry has not yet been finally defined. Since such an early tolerance consideration allows quick and economic design changes seeking for robust designs, it is advisable that the design engineer, who is entirely familiar with the design, should take this step. For this purpose, this paper presents an easy-to-use CAD-based tolerance analysis method for skeleton models. The relevant part deviations are represented by varying geometric dimensions with externally driven family tables. The approach comprises the strength of vector-based methods but does not require an expensive set-up of tolerance analysis models. Particularly, the novelty of this method lies in the CAD-internal sampling-based tolerance analysis of simple geometries without the use of expensive CAT software. This enables designers to evaluate the effect of tolerances already at the preliminary design stage. Using a case study, the presented approach is compared with the conventional vector-based tolerance analysis.

The Design and Development of Bamboo-Baking Ovens Appropriate for Handicraft

2014 ◽  
Vol 535 ◽  
pp. 506-510
Author(s):  
Sakchai Sikka
Keyword(s):  
Research And Development ◽  
Current Situation ◽  
Manufacturing Processes ◽  
Design And Development ◽  
Baking Quality ◽  
The One

This is a research in the style of research and development. The researcher conducted fieldwork by collecting data on the current situation of and problems in bamboo-baking in 10 provinces. Then the data were analyzed to find out about the forms of ovens and quality of each type of baking in order to compare the baking quality. Moreover, the data were used in a brainstorm with 12 participators consisting of entrepreneurs and those who are concerned. All the data from the study were used in the determination of the basic requirements for the experiment of designing and creating 4 model ovens. The fourth is the one that has been tested and proved to be suitable for usage in the manufacturing processes of bamboo handicraft, both wickerwork and furniture. In the experiment of preventing the eating of weevils and other insects, it was found that during 6 months, no evidence of such eating was found, which corresponds to the determined standard.

Colour: Physical or Phenomenal?

Philosophy ◽  
1998 ◽  
Vol 73 (2) ◽  
pp. 301-304
Author(s):  
RUSSELL WAHL ◽  
JONATHAN WESTPHAL
Keyword(s):  
Absorption Spectrum ◽  
Absorption Spectra ◽  
The Other ◽  
Psychological State ◽  
Necessary Truths ◽  
The One ◽  
Colour Terms

We wish to defend Jonathan Westphal's view that colour is complex against a recent ‘phenomenological’ criticism of Eric Rubenstein. There is often thought to be a conflict between two kinds of determinants of colour, physical and phenomenal. On the one hand there are the complex physical facts about colour, such as the determination of a surface colour by an absorption spectrum. There is also, however, the fact that the apparently simple phenomenological quality of what is seen is a function of the physiological and psychological state of the viewing subject. Should the physical trump the phenomenal, or is it the other way round?Much of the phenomenal variation of colour, however, is explained by physical facts. There is a physics and a psychophysics of colour. Colours appear, to the colour scientists at least, to be in some sense objective, a sense not explained by the view that they are purely phenomenal. Taking physics and psychophysics into account will mean rejecting the claim that the content of what our concepts of colours are concepts of is exhausted by the purely phenomenal, or that we can determine these concepts simply by gazing at a colour. Taking account of physics will lead, as Westphal argued, instead to a view about white and the other colour terms like Putnam's account of gold. Necessary truths about colours cannot be explained without reference to the logic of the compossibility of what is given in reflection and absorption spectra, the analogue of H2O.

A Novel Model for the Tolerancing of Nonrigid Part Assemblies in Computer Aided Design

2019 ◽  
Vol 19 (4) ◽  
Author(s):  
Mehdi Tlija ◽  
Anis Korbi ◽  
Borhen Louhichi ◽  
Abdelmajid Benamara
Keyword(s):  
Computer Aided Design ◽  
Tolerance Analysis ◽  
Physical Factors ◽  
Worst Case ◽  
Manufacturing Defects ◽  
Computer Aided ◽  
Aided Design ◽  
Novel Model

In the design step, the realistic modeling of the product represents an industrial requirement and a digital muck up (DMU) improvement. Thus, the tolerance integration in the computer aided design (CAD) model with the neglect of important physical factors, such as the components’ deformations during the mounting and assembly operation, causes a deviation between the numerical and the realistic models. In this regard, this paper presents a new model for the tolerance analysis of CAD assemblies based on the consideration of both manufacturing defects and deformations. The dimensional and geometrical tolerances are considered by the determination of assemblies’ configurations with defects based on the worst case tolerancing. The finite elements (FEs) simulation is realized with realistic models. An algorithm for updating the realistic mating constraints, between rigid and nonrigid parts, is developed. The case study of an assembly with planar and cylindrical joints is presented.

Applications of the GapSpace Model for Multidimensional Mechanical Assemblies

2003 ◽  
Vol 3 (1) ◽  
pp. 22-30 ◽  
Author(s):  
Zhihua Zou ◽  
Edward P. Morse
Keyword(s):  
Sufficient Conditions ◽  
Tolerance Analysis ◽  
Necessary And Sufficient Conditions ◽  
Important Task ◽  
Assembly Model ◽  
Worst Case ◽  
Mechanical Assemblies ◽  
Necessary And Sufficient ◽  
The Way

The most fundamental, and perhaps most important, task in the tolerance analysis of assemblies is to test whether or not the components with tolerances are actually able to fit together (called assembleability). Another important task of tolerance analysis is to check how the tolerances affect the quality or functionality of a product when they are assembled together. This paper presents the way the tolerance analyses are implemented by an assembly model, called the GapSpace model. The model can not only capture the necessary and sufficient conditions for assembleability analysis, but also transfers the functionality into the modeling variables (gaps). The assembleability analyses based on the GapSpace model for nominal components and those with worst case or statistical tolerances are introduced through an example. The problems of testing the quality of assemblies and calculating sensitivities are solved quickly and precisely using the model. The GapSpace model is more suitable for certain GD&T tolerancing methods than for parametric plus/minus tolerancing.

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