Auswahl der wissenschaftlichen Literatur zum Thema „Pneumatic fittings testing“

Pneumatic artificial muscles are a class of pneumatically driven actuators that are remarkable for their simplicity, lightweight, and excellent performance. These actuators are essentially a tubular bladder surrounded by a braided sleeve and sealed at both ends. Pressurization of the actuators generates contraction and tensile forces. Pneumatic artificial muscles have traditionally been used for robotics applications, but there has been recent interest in adapting them to a variety of aerospace actuation applications where their large stroke and force, which are realized at minimal weight penalty, create potential performance improvements over traditional technologies. However, an impediment to wide-spread acceptance of pneumatic artificial muscles is the relatively short fatigue lives of the actuators reported in the literature (typically, less than 18,000 actuation cycles before damage occurs). The purpose of this study is to develop a new construction method designed to greatly increase the number of fatigue cycles before damage occurs. The fabrication methodology employs a swaging process to provide smooth and distributed clamping of the bladder and braided sleeve components onto the end fittings. This approach minimizes stress concentrations and provides high mechanical strength, which can be experimentally validated via testing for the ultimate tensile failure load. Finite element analysis was used to refine the design of the swaged end fittings before extensive fatigue testing began. Long-term fatigue testing of the actuators under realistic operating conditions showed a substantial increase in actuator life, from a maximum of less than 18,000 cycles in previous research studies to more than 120,000,000 cycles in this study.

The subject of this diploma thesis is the design of a single-purpose machine for automatic testing of pneumatic fittings. Pneumatic fittings used in brake systems are subject to high technical requirements and 100% tightness control in production. In this case, manual testing is not effective and the goal is to automate the process. The theoretical part presents pneumatic mechanisms, analysis of the tested pneumatic fitting with technical parameters, the possibility of tightness testing, use of sensors, and rotary tables. In the practical part, a systematic analysis of the problem was performed, according to which the overall design proceeded. Subsequently, the design of the complete machine containing individual nodes is processed, supplemented by the necessary calculations. The conclusion of the thesis contains an evaluation of the whole project.

Recently, there have been a few failures with brittle fractures occurring during hydrostatic or pneumatic proof testing in pipe fittings that rekindled the need for paying attention on how to specify the toughness for pipe fittings and other components such as valves. This paper shows how an analysis procedure called the “Master Curve of Fracture Transition Temperatures” can be used to specify a Charpy shear area percent at some target temperature so that ductile initiation behavior occurs for either a surface or through-wall cracks in fittings, components or pipe material at the minimum design temperature. Due to differences in thickness, loading rate, and constraint conditions, the Charpy test transition temperature will not be at the same temperature as the minimum design temperature. In addition to the background and summary of prior efforts, several examples of full-scale pipe and fitting/valve fracture tests on different materials will be presented to show that the methodology works well. It is also possible from this method to specify the Charpy shear area percent at some temperature to ensure that brittle fracture propagation will not occur. There are some limits on this methodology for some newer steels that have very high Charpy energy values, and those conditions are also summarized.

The downhole tool industry commonly conducts tests that require pressurization of a vessel. The most common failure mode is through the launching of end caps, plugs, and fittings as opposed to a catastrophic rupture of the vessel body. This type of vessel failure during high pressure gas testing can produce significant threats to nearby personnel in the form of high energy projectiles and blast waves that must be blocked or dissipated before reaching personnel. Adequately designing a structure to contain this energy depends on how well a worst case scenario event can be modeled. Blast waves ensue from a pneumatic pressure test failure. As a vessel fails, the volume of pressurized gas will expand into the surroundings. A computational fluid dynamics (CFD) model of the pressure vessel and its enclosure will provide an accurate assessment of the blast loads in the environment. This paper describes an experimental test program of a simulated pneumatic pressure vessel failure through the launching of a hypothetical end cap or plug inside an enclosure. The recorded blast loads from three tests at various pressures were compared to simplified two-dimensional CFD model results of the enclosure. Two CFD models were run for each test: the first accounts for the time required for the vessel to open during failure, and the second assumes an instantaneous release of pressurized gas. The CFD results for the first model matched the test results well and provided validation of the modeling approach. The second model indicates the level of conservatism of predicted blast loads when assuming an instantaneous vessel failure. A properly designed pressure testing enclosure can provide a high level of safety in the event of a failure; several types of enclosure designs have proven to be successful, which are discussed in this paper. Equally important is the need to have competent operators with an awareness of the risks involved with pressure testing combined with training and competency programs implemented throughout the industry.

Abstract The work in this paper is a part of the T-shirt cannon automation project. The objective of the project is to develop an autonomous robot carrying cannons to automatically shoot T-shirts during the sports events at the University of Cincinnati (UC). More specifically, the T-shirt cannon will be used and driven by the UC cheerleading team and be able to automatically shoot T-shirts at the audience in the Nippert Stadium and the 5/3 Arena for football and basketball games, respectively. The design and automation of the T-shirt cannon require a significant effort and a multi-disciplinary team to complete. This paper will focus on the process of designing, building, and testing the firing mechanism for the cannon, including the determination of cannon’s firing method, barrel design and assembly, base design and barrel mounting method, pneumatic analysis, and automation and control of the firing of T-shirts. The goal of the firing mechanism is that the cannon would fire off as many T-shirts as possible with the window of a single timeout at the game. The project starts with the preliminary research and the initial testing. During the preliminary research, the relevant safety standards/codes and previous T-shirt cannon designs were reviewed and studied. Especially the possible working with pressurized air, the material used in the design must be rated above the target firing pressure to ensure the cannon itself not explode and the air supply tank and fittings must be in good condition. During the initial testing, the site visits were conducted, the cheerleaders were interviewed, the dimensions of the stadium and the 5/3 arena were measured, and therefore the shooting distance and shooting angles were estimated. After the initial testing and preliminary research, a set of engineering characteristics were established, following by the concept design, in which the barrel assembly, the pneumatics, the firing mechanism, and the mounting method were discussed, analyzed, and determined. The barrels had two major designs, one is using a railing support system with an external tank of air to power and fire the cannon, and another one is using a chamber of air to power and fire the cannon with the barrels surrounding the air chamber itself. Two methods are analyzed and compared. The optimum one, therefore, was determined and developed. For the firing mechanism, two main designs are a spring-loaded firing mechanism that could increase the sealing capabilities of the barrels, and a tight tolerance fit that has less weight. Two designs were tested and analyzed, the optimum one was determined and built, followed by the firing mechanism testing. This paper will describe the process of design, building, and testing the firing mechanisms of this T-shirt cannon at UC. The paper will also discuss the testing results on shooting performance.

Direct push (DP) methods provide a cost-effective alternative to conventional rotary drilling for investigations in unconsolidated formations. DP methods are commonly used for sampling soil gas, soil and groundwater; installing small-diameter monitoring wells; electrical logging; cone penetration testing; and standard penetration tests. Most recently, DP methods and equipment for vertical profiling of formation hydraulic conductivity (K) have been developed. Knowledge of the vertical and lateral variations in K is integral to understanding contaminant migration and, therefore, essential to designing an adequate and effective remediation system. DP-installed groundwater sampling tools may be used to access discrete intervals of the formation to conduct pneumatic slug tests. A small-diameter (38mm OD) single tube protected screen device allows the investigator to access one depth interval per advancement. Alternatively, a larger diameter (54mm OD) dual-tube groundwater profiling system may be used to access the formation at multiple depths during a single advancement. Once the appropriate tool is installed and developed, a pneumatic manifold is installed on the top of the DP rod string. The manifold includes the valving, regulator, and pressure gauge needed for pneumatic slug testing. A small-diameter pressure transducer is inserted via an airtight fitting in the pneumatic manifold, and a data-acquisition device connected to a laptop computer enables the slug test data to be acquired, displayed, and saved for analysis. Conventional data analysis methods can then be used to calculate the K value from the test data. A simple correction for tube diameter has been developed for slug tests in highly permeable aquifers. The pneumatic slug testing technique combined with DP-installed tools provides a cost-effective method for vertical profiling of K. Field comparison of this method to slug tests in conventional monitoring wells verified that this approach provides accurate K values. Use of this new approach can provide data on three-dimensional variations in hydraulic conductivity at a level of detail that has not previously been available. This will improve understanding of contaminant migration and the efficiency and quality of remedial system design, and ultimately, should lead to significant cost reductions.

In this study, the temperature dependent dynamic behavior of a magnetorheological (MR) damper is characterized. Substantial effort has been devoted to developing an understanding of the dynamic behavior of MR dampers with virtually no emphasis on temperature effects. However, MR dampers can experience large variations in temperature during operation as a result of damper self-heating, which may cause significant perturbations to its damping and yield force. Temperature variations also induce stiffness changes in the pneumatic accumulator due to gas law effects. To model temperature dependent effects, an MR damper, which was designed and fabricated for a ground vehicle seat suspension application, was tested over temperatures ranging from 0 °C to 100 °C at a constant frequency of 4 Hz and a constant amplitude of 7.62 mm on an MTS-810 material testing system equipped with a temperature-controlled environmental chamber. To model the MR damper behavior, a parametric algebraic model was used due to its physically motivated, low computational cost and high accuracy. Temperature dependent model parameters are identified from the experimental data by using a curve fitting method. Perturbations in model parameters arising over the tested temperature range indicate that yield force and post-yield viscosity are strongly dependent on temperature. As operating temperature increased from 0°C to 100°C, the controllable yield force decreased by up to 20%, the post-yield damping decreased by over 60%, and the stiffness at high piston velocity also increased significantly.