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An Effective Bench Test for Hydraulic Fluid Selection

by Dr. R. K. Tessmann and Dr. Ing T. Hong

For a copy of this paper, download the file ttp01.pdf (3306 kb, 10 pages). Click to return to articles index

The selection of a proper fluid to be used in a hydraulic system is an important part of any design effort. The hydraulic fluid must normally transmit, transform, and control the power from the system input to the output. In addition, the fluid is expected to provide lubrication and antiwear protection to many of the other components in the system. Although there are at least 22 parameters which describe a hydraulic fluid, most of these parameters are well defined. However, the antiwear and lubrication properties of a hydraulic fluid deserve more discussion.

There are several test methods which have been developed to assess the antiwear properties of liquids. Most of these procedures are intended to evaluate fluids other than those directed toward use in a hydraulic system. This paper will present a bench type wear test method designed to overcome the recognized problems of other wear test procedures. Developed by the authors at the Fluid Power Research Center, formerly at Oklahoma State University, this bench test method is called the Gamma Wear System. In addition to describing this type of method, the paper will present actual test data obtained from hydraulic fluids.

Extending Component Service Life through Proactive Maintenance

by Dr. E.C. Fitch

For a copy of this paper, download the file ttp02.pdf (1178 kb, 15 pages). Click to return to articles index

Today, the cost of running equipment to breakdown failure is too great in terms of downtime, parts inventory, maintenance personnel, and repair. Fortunately, there is an attractive new alternative known as "proactive maintenance."

This paper presents an overview of proactive maintenance and offers ways of extending the service life of system components. In a nutshell, proactive maintenance is concerned with the detection and correction of aberrant root cause failure conditions. The paper illustrates how such aberrant conditions can be identified and corrected and the penalty that is assessed for ignoring the symptoms of root cause aberrations.

Fluid Power Goals and Trends for the 1990’s

by Dr. E.C. Fitch, Dr. R. K. Tessmann, and Dr. Ing T. Hong

For a copy of this paper, download the file ttp03.pdf (650 kb, 14 pages). Click to return to articles index

Every important activity must have a goal and a stimulus. To be realistic, a goal must be based on achievable endeavors. Thus to formulate an effective plan for coping with problems in the future, fluid power must have rational goals that reflect the available knowledge base, attitude consensus of industry, and the prevailing direction of technology application. Such goals must be natural extensions of industrial trends.

This paper proposes a broad spectrum of goals for fluid power, which if successfully attained, will ensure its continued progress and growth well into the next century. These goals can be categorized in seven activity areas as follows:

Industrial trends reveal not only the industry-wide direction of focus, but also the expressed level of activity being applied. These technological trends provide evidence that specific goals are being pursued. Trends are confirmation of the general consensus of industry and should be reviewed and studied carefully. The technological trends presented in this paper provide a strong basis for assigning research subjects both in academe and industry. The trends also provide unusual insight for industry regarding "what is new" and "what is passe."

A Unified Approach for Design and Analysis of Engineered Systems using HyPneu

by Dr. Ing T. Hong and Dr. R. K. Tessmann

For a copy of this paper, download the file ttp04.pdf (189 kb, 11 pages). Click to return to articles index

The design and analysis of most engineered systems involves many and sometimes diverse technical disciplines. For example, in the design of a fluid power system, the input to the system is usually some type of prime mover. In addition, the output may include gears, linkage, etc. The output may be used in a feedback circuit which will normally encompass instrumentation, logic elements, and controllers. In order to evaluate the total performance of such systems analytically, a software package must be available which can unify the interactions of these diverse components.

This paper will present a new computer program which will unify hydraulic, pneumatic, electronic, and mechanical components permitting the analysis of complete engineered systems on a P.C. Several example systems will be shown which originate in actual machinery designs. These example systems will be simulated and output type information will be presented.

HyPneu—Computerized System Problem Identification and Analysis

by Dr. Ing T. Hong and Ming-Yuan Tsuei of China Steel Co.

For a copy of this paper, download the file ttp05.pdf (147 kb, 10 pages). Click to return to articles index

The design process has changed significantly as the computer age evolved. The days when a design engineer develops a system through trial-and-error are rapidly coming to an end. The one factor which as slowed the evolution of the design process has been the availability of a computer program which can run on a personal computer and analyze a complete engineered system. Many times an engineered system will include hydraulic, pneumatic, electronic, and mechanical components. These components interact to produce the overall system performance. However, software has not been available which can handle such a diverse array of system components. Therefore, problem identification and analysis of systems have evaded the analytical stage of system design to become painfully evident in the hardware stage.

This paper presents a computer program called HyPneu which can analyze a complete system. In addition, HyPneu will permit the engineer to design a system at his desk on his personal computer. Once the program has been explained and described, real world systems with performance problems will be analyzed using HyPneu. The problems will be revealed and possible solutions will be predicted.

Computerized Fluid Power Design of Vehicle Chassis Systems

by Dr. Ing T. Hong and  Dr. E.C. Fitch

For a copy of this paper, download the file ttp06.pdf (160 kb, 10 pages). Click to return to articles index

Fluid power is the backbone of a motor vehicle chassis system. The design of the fluid power system determines whether the ride quality and maneuverability of the vehicle are acceptable. One of the most difficult problems in chassis design analysis is to resolve the interfacing equations between the mechanical structure and the fluid power system. The complexity of the design analysis becomes even greater if there is any chassis control strategy involved.

This paper presents an innovative modeling technique for interfacing the mechanical dynamics of the chassis with the fluid power system. The technique used here is called "Interfacial Modeling" or "Visual Modeling." In this modeling approach, fluid power components and mechanical structural elements are iconized to incorporate the necessary mathematical models needed to represent the system. These character instilled icons become the building blocks to formulate a chassis system. Implementing these icons with the system integrating algorithms results in an effortless analysis and design task. This paper reveals the interfacial modeling principle and illustrates the benefit of this technique with practical design examples related to vehicle chassis systems.

Qualification of Hydraulic Fluid through Pump Testing

by Dr. R. K. Tessmann

For a copy of this paper, download the file ttp07.pdf (169 kb, 10 pages). Click to return to articles index

The life and reliability of the hydraulic system components are dependent upon the characteristics of the fluid circulating in the system. There is no doubt that the hydraulic component which suffers the most when wrong fluid is used in the system is the pump. There are three different types of hydraulic pumps widely used today—vane, gear, and piston pumps. The vane pump was the first to gain popularity. Then the gear pump and finally, today, the variable volume piston pump is rapidly gaining favor. Each of these pumps has its own needs and requirements relative to the hydraulic fluid used in the system. In addition, the pump of a particular manufacturer may possess different requirement than the same type of pump from other manufacturers. Therefore, each pump manufacturer must diligently conduct tests to insure that the fluid which are recommended will, indeed, adequately protect his pump. On the other hand, the fluid manufacturers are hard pressed to conduct several different pump tests on every developmental stage of the fluids research program within his company. Pump tests are time consuming and require expensive equipment to conduct a rigorous test.

This paper presents a brief overview of some of the various pump tests which are used today. In addition, the testing dilemma which confronts both the pump manufacturers and the fluid suppliers as more and different fluid are developed will be discussed.

The Dynamic Analysis of Pneumatic Systems using HyPneu

by Dr. Ing T. Hong and Dr. R. K. Tessmann

For a copy of this paper, download the file ttp08.pdf (183 kb, 10 pages). Click to return to articles index

Pneumatic systems have been used in industrial applications every bit as long as hydraulic systems. In addition, the performance of a pneumatic system is at least as important as any of the other systems currently in use. However, until recently very little help and few tools were available for the designers of pneumatic systems. The compressibility of the pneumatic medium (air) and the change in volume, pressure, and density as a function of system temperature and pressure have made the dynamic analysis of pneumatic systems very difficult to model and simulate with any degree of success. Like hydraulic systems, the pneumatic counter part is extremely non-linear placing even more of a burden on the designers and would-be simulators. In recent years an approach has been developed and coded into a computer-aided tool called HyPneu which realistically models and simulates both pneumatic and hydraulic systems.

This paper presents a method which is shown to be quick, easy to use, and very accurate in modeling and simulating pneumatic systems. This technique permits the system designer to conduct a dynamic analysis on the system prior to procuring components, assembling the system, and performing testing type of evaluations. This concept will not eliminate system testing completely but will turn such efforts from development activities to verification activities.

What Time do you Have?

by Dr. Ing T. Hong and Dr. R. K. Tessmann

For a copy of this paper, download the file ttp09.pdf (153 kb, 10 pages). Click to return to articles index

Hydraulic systems are currently used in a wide variety of industrial applications. In a great number of these cases the response time of the system is a critical parameter. The response time of a hydraulic system is the synergistic results of the response times of all of the components used in the system. Therefore, most component manufacturers will provide information relative to the responsiveness of their components. Unfortunately, this response information is not consistent nor is it compatible from manufacturer to manufacturer. The advent of computer-aided design and analysis software has forced the system designers to be much more aware of the system response characteristics and therefore the component response information. The question "What time do you have?" is directed toward the problems associated with the responsiveness information currently included in many component manufacturers catalog.

Contamination Control of Aircraft Hydraulic Systems

by Dr. R. K. Tessmann and Dr. Ing T. Hong

For a copy of this paper, download the file ttp10.pdf (332 kb, 15 pages). Click to return to articles index

Particulate contamination is the major source of wear and failure in hydraulic systems. Furthermore, an aircraft hydraulic system is a very high performance system with a high risk both in human life and financial cost when failures occur while in flight. One of the most severe problems which must be addressed in designing an aircraft hydraulic system with high reliability is particulate contamination. Therefore, contamination control must be a major concern to the designers and maintenance personnel associated with the hydraulic systems on aircraft. Fortunately, however, contamination induced failures can be avoided or at least minimized if appropriate contamination control strategies are applied in the design and maintenance activities. This paper reveals the modern contamination control theories that allow the engineer to explore practical contamination problems through component sensitivity tests.

Computerized Design Analysis of Machine Tool Hydraulic System Dynamics

by Dr. Ing T. Hong and Dr. R. K. Tessmann

For a copy of this paper, download the file ttp11.pdf (542 kb, 14 pages). Click to return to articles index

The design and analysis of most engineered systems involves many diverse technical disciplines. In the case of hydraulic systems, which are discussed in this paper, the actual input is some kind of prime mover such as an internal combustion engine or an electrical motor. The speed and torque of the prime mover is converted to the hydraulic power parameters at the pump, the directional control of the hydraulic power is provided by a valve, while the output can be the force and velocity of a reciprocating cylinder which may actually connect to the load through linkages and gears. The input to the valves can be electronic, hydraulic, or maybe manual. In addition, the output of the hydraulic system may be used in a feedback circuit which will normally encompass instrumentation, logic elements, and controllers. It is imperative that the design engineer be able in perform some kind of analysis to insure the proper function of diverse systems such as hydraulic systems. Such an analysis can be performed in the laboratory through the use of prototype systems, or it can be performed through computerized simulation. In order to evaluate the total performance, from input to output, of a hydraulic system analytically, a software program must be utilized which can integrate the interactions of the diverse components involved.

This paper will discuss the computerized design analysis of hydraulic systems using a computer program, called HyPneu, which is capable of integrating hydraulic, pneumatic, electronic, and mechanical components thus permitting the design analysis of complete hydraulic systems. The aspects involved in computerized design analysis will be discussed, followed by the illustration of the concepts through the use of example systems. These example systems will be simulated and the output information will be presented.

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