Severity Of Test Conditions Research Articles

Flat versus Curved Contact Surfaces Effect on Consumer P-Metric and LT Tire Operating Temperatures

Abstract Rolling stress and resultant operating temperature is critical to the endurance of a tire. There are fundamental differences between the tire stresses when operating on a flat surface, as experienced in normal highway use, and on a cylindrical laboratory test wheel. Even though there are substantially higher tire stresses and temperatures on a curved test wheel, nonetheless, cylindrical road wheels are widely used with the industry for tire endurance testing. Therefore, it is important to consider the severity of test conditions intended for a flat surface and the equivalent severity on the curved surface in order to avoid subjecting the tire to unrealistic stresses and temperatures. In this study, temperature measurements were made at the tire belt edge and centerline, for both flat and curved surfaces, under designed ranges of load, pressure, and speed conditions. Statistical regression models that predict the temperatures at the tire centerline and belt edge locations are developed and discussed. A simple yet consistent conversion from flat to curved conditions is provided so that equivalent tire temperatures are obtained. Flat highway conditions are derived that are temperature equivalent solutions to each of the FMVSS139 step test conditions.

Application of Modified ASTM C1260 Test for Fly Ash-Cement Mixtures

The ASTM C1260 accelerated mortar-bar test is a commonly used method for rapid identification of potential alkali-aggregate reactivity and may also be used for assessing the effectiveness of supplementary cementitious materials in suppressing alkali–silica reactivity (ASR). A general criticism of this test method is the severity of test conditions. It is not uncommon for aggregates with a good field-performance track record and no history of ASR to test reactive by this method. The purpose of this study was to evaluate the effectiveness of fly ash in controlling expansion due to ASR, using a modified ASTM C1260 test. Three different strengths of NaOH solution were used to test reactive, potentially reactive, and nonreactive aggregates in the presence of Class F and Class C fly ash at 20% and 35% replacement by mass of cement. The other variables included high- and low-alkali cement, extended curing time, and a longer testing period of 28 days. A correlation was drawn between additional evaporable water and expansion due to ASR.

Rational system of evaluating fuel and oil service properties

1. A set of standard tests, including both laboratory and engine methods, should be developed and coordinated for the evaluation of service properties of new fuels and oils intended for production-line engines. 2. The following should be done in order to shorten the time consumed in conducting the tests: a) Develop and standardize methods for short-term functional test-stand evaluations in special single-cylinder units and in full-scale engines, keeping in view the fact that the investigation in breadth and depth of all of the service properties of new fuels and oils is carried out during this stage, whereas the subsequent stages evaluate mainly the reliability of engine operation on the fuel or lubricant in question. b) Develop methods for preconditioning full-scale engines prior to test-stand evaluations in such a manner as to provide good precision of results without increasing the test period, achieving this by increasing the severity of test conditions.