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1 - The hydraulic circuit with acceleration deceleration valve is a simple and cost-effective alternative for controlling the acceleration and deceleration of hydraulic actuator while starting and stopping. The circuit can be used for getting a jerk free motion of any hydraulic actuator. Since it is compact and low cost, it finds great application in hydraulic material handling equipment where expensive proportional valves are used just to control the initial acceleration and final deceleration of the actuator.
Engineering - Component Manufacturing, Testing&Technology Transfer, Patankar A.M., p.259
2 - The CDUS carburettor is equipped with a choke disc controlled by a manual choke control, a deceleration valve (overrun braking valve), which reduces exhaust emissions during overrun braking and gear-changing and a device which allows the idling mixture to bypass the throttle.
Technical description of Saab Cars, p.4
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These valves are devısed for external deceleration of slides moving at high speeds with heavy loads to achieve shockless braking and reversal at midstrokes of cylinders. A deceration valve is essentially a lineer type spool valve operated by a cam on the sliding member. As the cam presses the roller, the tapered land on the spool moves along the orifice to cut the flow to the drive. The rate of cut off is dependent both on the shape of the orifice and the cam profile. When the roller on the spool is off the cam, the valve permits free flow.
(Central Machine Tool Institut, Machine Tool Design Handbook,1982,pg 819)
2) Intermittent Transfer: (Group : transfer system)
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In intermittent transfer the workstations’ position is fixed. Parts are moved with an intermittent or discontinuous motion between the stations and then registered at the proper locations for processing. All parts are moved at the same time, hence the term synchronous transfer system which is also used to describe this method of workpiece transport. Examples of intermittent transfer applications can be found in machining operations, pressworking operations and mechanized assembly.
In intermittent transfer the workstations’ position is fixed. Parts are moved with an intermittent or discontinuous motion between the stations and then registered at the proper locations for processing. All parts are moved at the same time, hence the term synchronous transfer system which is also used to describe this method of workpiece transport. Examples of intermittent transfer applications can be found in machining operations, pressworking operations and mechanized assembly.
(Shimon Y., Hans-Jurgen Warnecke, Wilbert E. Wilhelm, Industrial Assembly, p.26)
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In intermittent transfer the work carriers are transferred intermittently and the workheads remains stationary. All the parts are moved at same time, hence the term synchronous transfer system, which is aiso used to describe this method of workpiece transport. For example, intermittent transfer systems are used in machining operations, press-working operations, etc such system is stressful to human workers, but good in automated operations.
In intermittent transfer the work carriers are transferred intermittently and the workheads remains stationary. All the parts are moved at same time, hence the term synchronous transfer system, which is aiso used to describe this method of workpiece transport. For example, intermittent transfer systems are used in machining operations, press-working operations, etc such system is stressful to human workers, but good in automated operations.
(A. K. Gupta,Gupta, Industrial Automation and Robotics,2007,pg238)
3)Fault-Tree Analysis (FTA): (Group : analysis method)
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(1) analyzing system design,
(2) performing tradeoff studies,
(3) analyzing common-cause failures,
(4) demonstrating compliance with safety requirements
(5) justifying system changes and additions
(Standart Handbook of Machine Design, Charles O. Smith, Sc D., RE, p107)
Fault-tree analysis is substantially different from FMEA in that it is deductive rather than inductive. FTA starts with what the user experiences and traces back through the system to determine possible alternative causes. The focus is on the product, system, or subsystem as a complete entity. FTA can provide an objective basis for:
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(1) analyzing system design,
(2) performing tradeoff studies,
(3) analyzing common-cause failures,
(4) demonstrating compliance with safety requirements
(5) justifying system changes and additions
(Standart Handbook of Machine Design, Charles O. Smith, Sc D., RE, p107)
Fault-tree analysis is substantially different from FMEA in that it is deductive rather than inductive. FTA starts with what the user experiences and traces back through the system to determine possible alternative causes. The focus is on the product, system, or subsystem as a complete entity. FTA can provide an objective basis for:
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Fault-tree analysis was first conceived in 1961 by H. A. Walson of Bell Telephone Laboratories in connection with a U.S. Air Force contract to study the Minuteman launch control system. At a safety symposium held in 1965 at the University of Washington, co-sponsored by the Boeing Company, several papers expounded the virtues of fault-tree analysis. These presentations marked the beginning of a widespread interest in using fault-tree analysis as a safety and reliability tool for complex dynamic systems such as nuclear reactors. Since then, fault-tree analysis has been widely used for evaluating the safety and reliability of complex engineering systems. Thus far, the most widespread use of fault trees has been in the nuclear industry beginning with the Reactor Safety Study [U.S. Nuclear Regulatory Commission, 1975] conducted over a two-year period.
One of the leading documents on fault-tree analysis is the Fault Tree Handbook written by the U.S. Nuclear Regulatory Commission [1981 J. This handbook remains the primer for all students of fault trees The following is a succinct description of the fault-tree model [U.S. Nuclear Regulatory Commission, 1981
A fault tree analysis ean be simply described as an analytical technique, whereby an undesired state of the system is specified (usually a state that is critical from a safety standpoint), and the system is then analyzed in the context of its environment and operation to find all credible ways in which the undesired event can occur. The fault tree itself is a graphic model of the various parallel and sequential combinations of faults that will result in the occurrence of the predefined undesired event. The faults can be events that arc associated with component hardware failures, human errors, or any other pertinent events which can lead to the undesired event. A fault tree thus depicts the logical interrelationships of basic events thai lead to the undesired event—which is the top event of the fault tree. It is important to understand that a fault tree is not a model of all possible system failures or all possible causes for system failure. A fault tree is lailored to its top event which corresponds to some particular system failure mode, and the fault tree thus includes only those faults that contribute to Ihis lop event. Moreover, these faults are not exhaustive—they cover only the most credible faults as assessed by the analyst. Fault-tree analysis, which is one of the principal methods for analyzing Systems safety, can be used to identify potential weaknesses in a system, or the most likely causes of a system's failure The method is a detailed deductive analysis that requires considerable system information and can also be a valuable design or diagnostic tool.
In fault-tree analysis, the sequence of events leading to the probable occurrence of a predetermined event is systematically divided into primary events whose failure probabilities ean be estimated. Several methods have been suggested for handling uncertainty in the failure probabilities of the primary event of interest, however, most of them develop merely an interval of uncertainty. Also, most available research results in fault-tree analysis are applicable only to cases with "point probability distributions."
Most current methods for fault-tree analysis do not provide Ihe means to use probability distributions for the primary components. When these methods do use probability distributions, at best they develop an interval of uncertainty for the probability of the undesired event of interest. Also, most current methods use the unconditional expected value as a measure of risk. This chapter introduces a relatively new method that incorporates conditional expectations and multiple objective analysis with fault-tree analysis. It provides managers and decisionmakers with more information about the system rather than merely providing a single point probability for the undesired event.
The conventional approach to fault-tree analysis has been the use of point probabilities for the analysis of the system. The approach is valid when we have accurate data on the component failure rate along with a point distribution. This is, however, practically never the case in most applications. In most cases, the database available for component failure rate is sketchy or has a wide uncertainty interval associated with it. Also, since fault trees deal with rare events, often the failure of some components of the system may not have occurred in the past and thus would not be included in the database.
(Yacov Y. Haimes, Risk Modeling, Assessment, and Management,2009, chapter 13)
4)The Application Enablers: (Group : automation)
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Application programs interact directly with the operating system to perform different tasks such as reading and writing disk storage or sending information over a communications network. The interaction between the operating system and application programs takes place through the Application Programming Interface(API) presented by operating system. Program products, called application enablers, extend the API presented by the operating system. Application enablers add function to the API, thus offering more services to application programs. (As the figure shows) Application enables reside between the operating system and the application program layers of our software model, and they actively communicate with both layers.
Application programs interact directly with the operating system to perform different tasks such as reading and writing disk storage or sending information over a communications network. The interaction between the operating system and application programs takes place through the Application Programming Interface(API) presented by operating system. Program products, called application enablers, extend the API presented by the operating system. Application enablers add function to the API, thus offering more services to application programs. (As the figure shows) Application enables reside between the operating system and the application program layers of our software model, and they actively communicate with both layers.
(Jim Hoskins, Bob Frank, Exploring IBM Eserver Zseries And S/390 Servers, page 193-196)
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Application Enablers—Extending the API
Application programs interact directly with the operating system to perform different tasks such as reading and writing disk storage or sending information over a communications network. The interaction between the operating system and application programs takes place through the Application Programming Interface (API) presented by the operating system (Figure 4.7). Program products , called application enablers, extend the API presented by the operating system. Application enablers add function to the API, thus offering more services toapplication programs. As the figure shows, application enablers reside between the operating system and rhe application program layers of our software model, and they actively communicate with both layers.
Adding additional services to the API makes the job of application program development easier. Because software development companies can more easily develop prewritten application programs, System/390 and zSeries users have more prewritten application programs from which to choose. In rhe same way, the productivity of developing custom application programs is improved because the application enablers provide many functions that would otherwise have to be written from scratch during the custom application development project. The following sections look at categories of application enablers used with System/390 computers: transaction-processing application enablers, database application enablers, including an overview of IBM's database strategy, and special-purpose application enablers.
(Jim Hoskins,Bob Frank, Exploring IBM Eserver Zseries and S/390 Servers: See Why IBM's Redesigned,eight edition,2003 ,page 193-196)
5)Hardcoating (Group : material application)
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Although some types of glass are softer than others, generally they offer sufficient abrasion resistance not to require a hard surface coating.Same special glasses do require a coating because of their tendency to strain, but these are normally high index glasses, which would in any case, usually have a antireflection coating.
Hard coats are made from different materials but there are two main parts. The most common are lecquer hard coats applied by dipping or spinning, less common are the vacuum-deposites hard coats, which are thinner but of a harder material.
(Mo Jalie,Ophthalmic lenses & dispensing, second edition, page 81)
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Hardcoating is quite similar to anodizing but is about ten times as thick and much harder. Both anodizing and hardcoating processes form oxides on the surface of the treated parts. Very often these parts have the oxide covering sealed to prevent the absorption of undesirable liquids such as oil or colors or even perspiration from fingers.
PROCESS OVERVIEW
PROCESS OVERVIEW
Sometimes, when a hardcoated part is submerged in a hot solution (water or chemical) to seal the oxide covering the part, the large difference in heat conductivity between the aluminum matrix and the oxide will cause crazing. That is one reason the room temperature hardcoating method was created.
The conventional method of sealing either anodized or hardcoated aluminum is immersion in distilled or deionizedwater at or near boiling. In the case of dyed films, a bath of nickel acetate, at the same temperature range, is used. In addition to the possibility of causing crazing, sealing can also degrade the abrasion resistance of hardcoating.
Hardcoating gives an aluminum surface the hardness of case-hardened steel (Rc 50-60) while maintaining the light weight of aluminum. Hardcoated surfaces may be found in hospitals, schools, factories, in the home, under the sea, and on the moon.
When a permanent dry lubrication is added to the hardcoated surface, we find many more uses for it A hardcoated aluminum prosthetic arm can have its joints permanently lubricated by this process.
Two types of hardcoats are currently available: the older type is formed at low temperature (32° F) in sulphuric acid; the newer type is formed at room temperature (60-70°F), also in sulphuric acid.
SEALING AND COLORING
Coloring hardcoated surfaces is similar to coloring anodized surfaces. It is done with the same dyes and procedures. The main difference is in the depth of colors. The oxide of anodized parts is much more porous so it absorbs more color.
Recently, products for sealing have come on the market that work at or near room temperature. These products should prevent crazing problems. The subject of sealing and coloring should be discussed and evaluated with the processing company whenever hardcoating is considered because vendors, who have been on the scene for 10-20 years, can give the best advice.
Mote that hardcoated surfaces do not have to be sealed. In fact, there is a military specification covering this.
FINISHING
Sometimes it may be necessary to lightly grind a hardcoated surface to make it flat or parallel. There are many abrasive wheels and compounds suitable for finishing hardcoated surfaces to achieve critical dimensional tolerances or very fine finishes.
For surface grinding, silicon carbide grit, size 80-120, will provide a finish of 8-2 microinch. For cylindrical grinding, a finer grit wheel. Morton 39C120-J8VK, will be free cutting and yet produce a fine finish. For internal grinding, a fine grit wheel, such as Norton 39C100-J8VK, produces the best results. In general, grinding should be done wet using a water coolant and a good soluble oil mixed approximately 100 to 1. For polishing or lapping, a boron carbide abrasive grain mixed with oil will give good results. The range of grit size should be 400-1200 depending on the finish required.
WROUGHT ALLOYS
Hardcoating is recommended for use with virtually all aluminum alloys. It is important to remember that hardcoat thicknesses are 50% penetration and 50% buildup.
1100 Series—The 1100 is very common. Bronze-gray in color at 0.002" thickness. The alloy is difficult to machine and is soft
2000 Series-The 2014, 2017. 2024, and 2618 forgings are very common. Avoid sharp comers. Gray-black in color at 0.002" thickness to blue-gray at 0.004" Good machina-bility. Thickness to 0.006" for salvage, although not as hard as thinner coats.
3000 Series—Most common is 3003. Gray-black in color at 0.002" thickness. Machines easily and is good for dye work.
4000 Series —Not commonly used. 5000 Series-Most common are 5005 and 5052. The 5005 is better for dye work: 5052 accepts only black. Both machine well. The 5052 gets excellent dielectric value when coated 0.004" thick.
6000 Series — The 6061 and 6063 are most common. Almost black at 0.002" thickness. The 6061 forms excellent hardcoat for grinding or lapping. Good dimensional stability. The 6063 is used for extrusions.
7000 Series—Most common is 7075. Blue-gray at 0.002" thickness. High strength alloy. Not good for grinding or lapping. Maximum for salvage is 0.008" thick.
INGOTS
Sandcast Alloys-Most common are 319. 355. and 356 (also 40E. Temalloy. Tenzalloy, and many other proprietary alloys). The 356-T6 is the most popular. Good for grinding and lapping. Hardcoat will not fill in exposed surface porosity which is common with sandcastings. Vacuum impregnation (plastic) will improve the hardcoated finish of a sand-casting.
Diecast Alloys-Most common are 218.360 and 380. Only 218 produces hardcoat comparable to that on wrought or sandcast material. However. 218 is difficult to diecast Maximum thickness is 0.0025". Maximum thickness for 360 and 380 is about 0.001".
The reason for the difference in hardcoating quality is the alloys. Silicon and copper are detrimental to a good hardcoat.
(James A. Brown, Modern manufacturing processes, 1991, page 34-39)
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