MÜGE BAŞARAN 030090704 , 5 ANSWERS OF 1ST WEEK WORDS

1-    Random sampling (in statistical quality control)/ (Quality Control)

Previous definition:

Taking a sample from a population or lot in which each item has an equal change of being included in the sample. Thus, when taking samples from a large bin, the inspector should not take only those that happen to be within reach.

(Kalpakjian S., Schmid S.R., Manufacturing engineering and technology, Ed. 5th, p. 1121)

Current Definition:

      The units selected for inspection from the lot should be chosen at random, and they should be chosen at random, and they should be representative of all the items in the lot. The random-sampling concept is extremely important in acceptance sampling. Unless random samples are used, bias will be introduced. For example, the vendor may ensure that the units packaged on the top of the lot are of extremely good quality, knowing that the inspector will select the sample from the top layer. ‘’Salting’’ a lot in this manner is not a common practice, but if it occurs and nonrandom-sampling methods are used, the effectiveness of the inspection process is destroyed.

The technique often suggested to draw a random sample is to assign a number to each item in the lot. Then n random numbers are drawn, where the range of these numbers is from 1 to  the maximum number of units in the lot. This sequence of random numbers determines which units in the lot will constitute the sample. Random numbers can be conveniently generated from a computer, from many hand-held calculators, or from tables of random numbers such as in Appendix IX. If products have serial or other code numbers, these numbers can be used to avoid the process of actually assigning numbers to each unit. Another possibility would be use a three-digit random number to represent the length, width, and depth in a container. For example, the random number 482 could represent the unit located on the fourth level, eighth row, and second column of the container.

In situations where we cannot assign a number to each unit, utilize serial or code numbers, or randomly determine the location of the sample unit, some other technique must be employed to ensure that the sample is random or representative. Sometimes the inspector may ‘’stratify’’ the lot. This consists of dividing the lot into strata or layers and then subdividing each strata, into cubes, as shown in Figure 13-1. Units are then selected from within each cube. While this stratification of the lot is usually an imaginary activity performed by inspector and does not necessarily ensure random samples, at least it ensures that units are selected from all locations in the lot.

Introduction to Statistical Quality Control  2nd Edition , Douglas C. Montgomery, Pg. 555

Mustafa İnan Kütüphanesi               TS156 .M66 1991

2-    Scheduling (in flexible manufacturing systems)

Previous definition:

Because FMS involves a major capital investment, efficent machine utilization is essential. Machines must not stand idle. Consequently, proper scheduling and process planning are crucial. Scheduling for FMS is dynamic, unlike that in job shops where a relatively rigid schedule is followed to perform a set of operations. The scheduling system in FMS specifies the types of operations to be performed on each part and identifies the machines or manufacturing cells where these operations are to take place. Dynamic scheduling is capable of responding to quick changes in product type; hence, it is responsive to real - time decisions.

(Kalpakjian S. , Schmid S.R. , Manufacturing Engineering and Technology, p. 1223)

Current Definition:

Scheduling is the process of organizing,  choosing and timing resource usage to carry out all the activities necessary to produce the desired outputs of activities and resources.  In an FMS, the objective of scheduling is to optimise the use of resources so that the overall production goals are met.  A Fuzzy Based Scheduling Model for FMS which is developed here aims at making  real-time control decisions that include dynamic scheduling and variable part routing used to solve scheduling problems in FMS environments.  Attempts will be made to use a an industrial implementation for experimentation.  Otherwise the model will be verified using data from literature.

Process planning and scheduling are important manufacturing planning activities which deal with resource utilization and time span of the manufacturing operations. In order to cope with competitiveness and globalization of today’s business environment, supply chains become more complex, and manufacturing processes have become more advanced, however products have to be manufactured in higher varieties and smaller batches. It is essential to establish effective and efficient process plans and production schedules to cope with the highly dynamic manufacturing requirements. Some automobile manufactures are gradually adopting their production ways to support the diversity of the customer needs and increase the changing speed for the developing the new products [1].

1.    Scheduling of Flexible Manufacturing Systems  Using Fuzzy Logic by Pramot Srinoi

A/Prof. Ebrahim Shayan  Dr. Fatemeh Ghotb, School of Mathematical Sciences      pg. 95

2.    Manufacturing systems and technologies for the new frontier [electronic resource] : the 41st CIRP Conference on Manufacturing Systems, May 26-28, 2008, Tokyo, Japan / Mamoru Mitsuishi, Kanji Ueda, Fumihiko Kimura, editors, pg. 269

3-    Product quality /(Quality Control and Manufacturing)

Previous definition:

       In view of rhe global economy and competition, a major priority in produckt quality is the concept of continuous improvement as ezemplified by japanese term kaizen,meaning never ending improvement.Still the level of quality that a manufacturer chooses for its products depends on the market for whichthe products are intended.Low cost,low quality products have their own market niche,just as there is a market for high quality,expensive products,such as a high precision machine tool, a rolls royce automoile, a private airplane or yacht or sporting equipment.

   

Kalpakjian, S., Schmid, S. R., Manufacturing Engineering and Technology, 5th ed., p. 1242

Current definition:

The collection of features and characteristics of a product that contribute to its ability to meet given requirements. Early work in controlling product quality was on creating standards for producing acceptable products. By the mid-1950s, mature methods had evolved for controlling quality, including statistical quality control and statistical process control, utilizing sequential sampling techniques for tracking the mean and variance in process performance. During the 1960s, these methods and techniques were extended to the service industry. During 1960–1980, there was a major shift in world markets, with the position of the United States declining while Japan and Europe experienced substantial growth in international markets. Consumers became more conscious of the cost and quality of products and services. Firms began to focus on total production systems for achieving quality at minimum cost. This trend has continued, and today the goals of quality control are largely driven by consumer concerns and preferences.

McGraw-Hill Concise Encyclopedia of Engineering. © 2002 by The McGraw-Hill Companies, Inc.,pg. 559

4-    Interpolation /(Manufactoring / automation)

Previous definition is not found on the web page !!

Current definition:

Movement along the path (interpolation) occurs incrementally by one of several basic methods (Fig. 37.11). Examples of actual paths in drilling, boring and milling operations are shown in the  Fig. 37.12.   In all interpolations, the path controlled is that of the center of rotation of the tool. Compensation for different types of tools, for different diameters of tools, or for tool wear during machining can be made in the NC program.

·      In linear interpolation , the tool moves in a straight line from start to end (Fig.37.11a) along two or three axes. Theoretically, all types of profiles can be produced by this method by making the increments between the points small (Fig.37.11b). However , a large amount of data has to be processed in order to do so.

·      In circular interpolation( Fig. 37.11c), the inputs required for the path are the coordinates of the end points, the coordinates of the center of the circle and its radius, and the direction of the tool along the arc.

·      In parabolic interpolation and cubic interpolation, the path is approximated by curves using higher-order mathematical equations. This method is effective in 5-axis machines and is useful in die sinking operations for the sheet- forming of automotive bodies. These interpolations also are used for the movements of industrial robots.

(Manufacturing Engineering and Technology 5^th Edition , Serope Kalpakjian, Steve R. Schmid, Pg. 1158)

5-    Low cycle  Fatigue/ (Material)

Previous definition

The cyclic loads are relatively high, significant amount of plastic strain are induced during each cycle, and short lives or low numbers of cycles to failure are exhibited if these relatively high loads are repeatedly applied. This type of behavior has been commonly called low-cycle fatigue or, more recently, cyclic strain-controlled fatigue. The transition from low-cycle fatigue behavior to high-cycle fatigue behavior generally occurs in the range from about 10^4 to 10^5 cycles, and many investigators now define the low-cycle fatigue range to be failure in 50000 cycles or less.

Failure of Materials In Mechanical Design, Jack A. COLLINS, John Wiley & Sons, 1993, Second Edition, p.393

Current Definition:

      The phenomenon of low cycle fatigue can be in principle described in terms of the theory of plasticity. In fact, low-cycle fatigue is a cyclic elastoplastic deformation occurring until the expenditure of plasticity reserves. The material behavior at unloading and reversed loading, in particular the shape and size of hysteresis loops, is of essential significance in low-cycle fatigue. The relation between maximal stress and strain within a cycle generally differs from that in monotonic quasistatic loading. The cycle-deformation relations depend on the type of loading process. They change whether this process is load- or displacement-controlled loading the maximal cycle stresses grow with the cycle number. Other materials reveal a tendency to cyclic softening. An intermediate place is occupied by the so-called plastically stabilizing materials. Depending on the microstructural state and temperature, the same material may behave in various ways. Typical diagrams of uniaxial tensile/compression deformation σ(ε) are shown in Figure 1.8. They correspond to symmetrical cycle loading with the given strain amplitude  . Figure 1.8a shows the behavior of a cycle-dependent hardening material; Figure 1.8b that of a softening material.

      When the strain level is high, cycle number at fatigue failure is comparatively small, and significant one-sided residual deformations accumulate in the specimen. At a moderate strain level, teat results are convenient to represent with fatigue curves. Compared with high-cycle fatigue curves, low-cycle fatigue curves are usually plotted on the plane of characteristic strain versus cycle number at failure. Standard test in tension or tension/compression are usually performed maintaining a constant range Δε of the nominal (average upon all the working parts of a specimen) strain ε.

   

Mechanics of fatigue / Vladimir V. Bolotin, Boca Raton : CRC Press, c1999 , pg. 9,10,11

Mustafa İnan Kütüphanesi               TA418.38 .B65 1999