Comparison of Theoretical and Experimental Infiltration Heat-loss Results in Two Residential Houses in Brookings, South Dakota

Up to 40% of the heating/cooling energy requirement of a typical home can be attributed to unnecessary air infiltration. To reduce the energy costs of heating/cooling a home, it is therefore essential that every possible measure be taken to reduce the loss of conditioned air through the many leakage paths in a house. In order to accomplish this, it is first necessary to locate these leaks, and to determine their relative importance. Both theoretical and experimental techniques have been developed to accomplish this. This effort compares existing theoretical techniques to new experimental results on two houses of different window construction, since windows are the most important sites of infiltration. First, air filtration was calculated by a theoretical method for Houses No. 1 and No. 2. Then it was measured by an air-test unit designed and built for this purpose. The air-test unit measures the rate of air flow through closed doors and windows resulting from inside/outside air-pressure differences simulated by the unit blower. This simulation recreates the air flow which will occur naturally due to wind action on a building, stack effect in a building, the operation of mechanical ventilation and exhaust systems, or a combination of these factors. These measurements were the main effort of this investigation

Strength Evaluation and Fatigue Prediction of A Pressurized Thick-walled Cylinder

ABSTRACT By design, a large caliber gun barrel routinely operates closer to its fatigue envelope than virtually any other device. The lifetime of a gun barrel is limited by bore damage and by fatigue crack growth, which depends crucially upon near-bore thermal damage arising from initial firing, the thermomechanical basis for early cracking and subsequent loss of liner material. The proper understanding and prediction of the strength and fatigue failure of a pressurized thick cylinder is an important prerequisite for any reliable application. In this paper, an analysis of two-dimensional stresses in a thick walled pressurized cylinder using an analytical method followed by fatigue calculation was performed. The effects of wall thickness and internal firing pressure, considering the material properties, on the stress distribution were investigated. This analytical method of stress analysis can be used as a valuable tool for evaluating strength and predicting failure phenomena of a large caliber gun barrel. INTRODUCTION The typical problems in stress analysis may be obtained by analytical, numerical or experimental methods. Analytical methods contain mechanics of materials and the theory of elasticity. Mechanics of materials is the engineer's way of calculating stresses. The method involves [1] the following steps: (1) Model how the deformations produced by load are distributed over the body; this can be achieved by experiment, intuition or symmetry arguments; (2) Determine how strains are distributed throughout a cross section by analyzing the geometry of deformation; (3) Apply the stress-strain relationship to the strain distribution in order to determine how stresses are distributed over a cross section; (4) Write an equation of static equilibrium by drawing a free body diagram to relate stress to load; (5) Then, one should either integrate the strain distribution in step two or use the energy arguments that relate to work done by applied loads to elastic strain energ

Proceedings of IMECE 2008 ASME 2008 International Mechanical Engineering Congress and Exposition

ABSTRACT Canno

SENSOR TEST PLATFORM FOR RAPID PRESSURE INDICATING SENSORS

ABSTRACT Maximum life cycles for rapidly pressurized cylinders can be obtained by knowing precisely the number and severity of pressurizations of the cylinder through sensor measurement. The development of sensors that are capable of quickly registering pressurizations and stresses in a pressurized cylinder requires a test platform that can rapidly pressurize a cylinder while being able to control speed of pressurization, pressure in cylinder, cyclical timing of pressurization, and the number of pressurizations. In this paper, the test platform is being developed using an impact load to rapidly pressurize the hydraulic fluid in the hydraulic cylinder. The impact pressure is created by a falling mass which strikes the piston of a hydraulic cylinder, which creates an impact pressure from the impact load. Due to the nature of the cylinder, a small amount of air remains in the cylinder; by varying the amount of air in the cylinder the pressurization rate can be controlled. The platform will allow for the gathering of vital information regarding the applications of varying pressurization time and magnitude and the ability of various sensors to register and properly determine the magnitude of the pressurization. Information gathered through the usage of this test platform will be vital to several departmental projects; including the stress assessment and fatigue prediction of thick pressurized cylinders. INTRODUCTION Testing sensors that are designed to detect rapid pressurizations of pressurized cylinders by conventional testing methods are expensive. The sensor test platform was developed to decrease the operating cost of sensor testing, provide a controlled environment for testing, and decrease the time to test a pressurized cylinder sensor. Each of these goals was taken into account in the design and development of the sensor test platform. The primary objective of the sensor test platform was t