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Title: Notes on proving rings and frames for soil testing equipment
Authors: Hvorslev, Mikael Juul, 1895-
Keywords: Frames
Proving rings
Soil mechanics
Soil testing
Soil tests
Publisher: U.S. Army Engineer Waterways Experiment Station.
Engineer Research and Development Center (U.S.)
Description: Miscellaneous Paper
Abstract: This report presents data on the design, construction, and calibration of various types of proving rings and frames used for determination and direct readout of forces or loads in laboratory and field tests on soils and other relatively weak materials. The first part of the report presents equations and diagrams for determination of deflections and moments in thin circular rings, ring segments with bosses, elliptical rings, flattened rings, rectangular proving frames with thin or thick end sections, and compound cantilevers. Some of these equations can be found in handbooks and textbooks, but other equations are not readily available and were developed by applying standard methods of the theory of elasticity to relatively thin structures. The second part of the report deals with the influence of several secondary factors, such as large deformations which can cause appreciable curvature of the calibration diagrams. Rigorous equations for thick rings yield data on corrections for relatively thick devices. Empirical data on fillets and stress concentrations are presented, and the approximate stiffening effect of fillets is estimated by use of a simplified theory in which only angular deflections caused by moments are considered. The influence of misalignment, creep and hysteresis, and temperature variations is discussed briefly. The last two parts of the report present examples of single and compound proving rings and frames proposed for use or actually used in testing equipment. General design procedures using the basic equations are proposed, and data are presented on suitable materials, including recent alloy steels capable of age or precipitation hardening, which eliminates the distortion often caused by heat treatment and quenching of other steels. The final sections deal with rough calibration before hardening and final machining and corrections of dimensions if needed, which are followed by repetitive loading to slightly above the rated capacity before the final calibration in order to decrease the effects of hysteresis and creep and the possibility of zero shifts.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Miscellaneous Paper

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