Laboratory Test Method

Abstract: A laboratory test method for evaluating ice adhesion has been developed employing a commercially available instrument normally used for dynamic mechanical analysis (TA RSA-III). This is the first laboratory ice adhesion test that does not require a custom-built apparatus. The upper grip range of ∼10 mm is an enabling feature that is essential for the test. The method involves removal of an ice cylinder from a polymer coating with a probe and the determination of peak removal force (Ps). To validate the test method, the strength of ice adhesion was determined for a prototypical glassy polymer, poly(methyl methacrylate). The distance of the probe from the PMMA surface has been identified as a critical variable for Ps. The new test provides a readily available platform for investigating fundamental surface characteristics affecting ice adhesion. In addition to the ice release test, PMMA coatings were characterized using DSC, DCA, and TM-AFM.

Abstract: A laboratory test method is described for the prediction of moisture damage in dense-graded asphalt concrete mixtures. The method consists of obtaining diametral (or indirect) tensile-strength and modulus ratios of compacted specimens subjected to vacuum saturation with water and to freeze-plus-warm-water-soak accelerated moisture conditioning. Test results for dry specimens are used to form the ratio bases. The ratios are used to predict short-term and long-term field damage. Fatigue curves for two mixtures exposed to the dry, vacuum-saturation, and accelerated moisture conditioning of the test method are presented to show effects of moisture on fatigue life. A tentative relationship shows a correlation between tensile-strength ratios obtained by the test method and pavement fatigue-life ratios. An example of the practical use of the correlation is shown. Results are presented from a five-year field evaluation study conducted by seven highway agencies on eight pavement test sections to determine whether the test method's predictive ratios and stripping tendencies correlate with field results. Short-term ratios from laboratory vacuum saturation were reached at four years of pavement age or before. Long-term ratios from laboratory accelerated moisture conditioning ranged from 0 to 0.80; they were reached at five years for some pavements and probably will be reached in a few more years for the other pavements. This ratio is considered one of maximum moisture damage to minimum moisture damage. Visual stripping in the field cores appears similar to the predicted laboratory stripping. Agency-determined layer coefficients decreased due to the loss of moisture cohesion from the associated stripping observed in the field. (Author)

Abstract: A laboratory test method has been developed which allows the evaluation of diverse properties of tire tread compounds on the same sample. The laboratory test instrument consists of a rotating abrasive disk against which a rubber sample wheel runs under a given load, slip angle and speed. All three force components acting on the wheel during the tests are recorded. By changing the variable values over a wide range practically all severities encountered in tire wear are covered. The well-known fact that compound ratings depend on the road testing conditions is verified. Most compounds are only significantly distinguishable against a control over a limited range of testing conditions. Using a road test simulation computer program based on the laboratory data shows that not only ratings correspond to practical experience but also calculated absolute tire life times do. Tests on surfaces of different coarseness and sharpness indicate that sharp coarse surfaces give the best results with road tests, wh...

Abstract: SUMMARY Intelligent use and interpretation of any test procedure requires having knowledge of the test reliability in specific clinical situations. For laborato- ry tests relating to specific diseases, clinical interpretations are based opti- mally upon positive and negative predictive values, or odds ratios, prede- termined at useful medical decision limits. Due to the many species, mana- gement and disease differences encountered in veterinary medicine, the interpretation of routine laboratory test values is usually made in relation to reference intervals determined for a defined species subset, or to other deci- sion limits dependent upon the experience of the clinician. Introduction of any new procedure, instrument or reagent is based upon several features including anticipated clinical value and efficiency in a dia- gnostic laboratory environment. The procedures for validation of a new test in the laboratory are well described. The reasons for each validation proce- dure and the interpretation as to whether the resulting observations indicate likely ability of the test to meet clinical needs is less well described and understood. If the clinical requirements of a test are the determining criteria validation procedures are much easier to understand and interpret. At pre- sent, most veterinary laboratory tests must refer to the recommended clini- cal requirements for human diagnostic testing. The experimental plan for within-laboratory method validation is presen- ted in four phases including initial familiarization with the method, prelimi- nary and more extensive validation experiments and implementation. Experimental designs are reviewed briefly for linearity studies, recovery studies, interference studies, within-run, between-run and replication stu- dies, comparison of method studies and reference intervals. Data analyses including the requirements for various statistical tests are described. If within-laboratory validation experiments indicate likely acceptable cli- nical performance the test procedure can be implemented for initial clinical use. For tests which relate to a specific disease, prospective studies should be designed, in consultation with clinicians, to evaluate medical decision limits leading to determination of diagnostic sensitivity, specificity and pre- dictive values of positive and negative test values. If clinical interpretation is dependent upon reference intervals, these should be determined according to recommended procedures and the clinicians should be informed as to the source and reliability.