Showing papers on "Dynamic load testing published in 1971"

Multiple-Wheel Heavy Gear Load Pavement Tests. Volume 1. Basic Report

Abstract: : Flexible and rigid pavements were constructed and tested to obtain data on pavement and soil behavior under large aircraft loadings for use in developing criteria for evaluating and designing airfield pavements subjected to multiple-wheel heavy gear loads (WMHGL). The test sections incorporated instrumentation systems designed to determine the response of the pavement structures to static, dynamic (slowly moving), and vibratory loads and to traffic by full prototype loadings of a 12-wheel assembly (one main gear of a C- 5A aircraft), a twin-tandem assembly (one twin-tandem component of the Boeing 747 assembly), and a single wheel. Analysis of static load response data from the flexible pavement instrumentation program resulted in the establishment of maximum elastic deflection and vertical elastic stress versus depth curves. Comparisons showed that the same relationships were true for static and dynamic load tests, as well as for speed tests. The findings for the rigid pavement test section indicated that the Westergaard algorithm can be used for reasonable predictio of pavement response to test loadings. The data from the instrumentation program and the traffic tests were used in the analysis of the flexible and rigid pavement test sections. The analysis resulted in a modification of the basic flexible pavement CBR design method.

Load Tests Results on Friction Piles in Sand

Abstract: As part of the design of an important pile foundation, an extensive testing program has been carried out in order to determine the type and the necessary characteristics of the pile best suited to the site and the structure to be designed. Three types of piles have been tested, i.e. timber piles, a steel H-pile, and a Herkules precast concrete pile. The Herkules and H-piles were equipped with deformation gauges and driven in 10-ft (3-m) increments to a total length of 70 ft (21 m), a loading test being carried out at the end of each increment. Thus, it was possible to determine the variations of the bearing capacity, the point–resistance, and the skin-friction as functions of the embedded pile length.The aim of this paper is to present the technique used and the results obtained.

Criteria for Externally Suspended Helicopter Loads

Abstract: : The study was conducted to determine the dynamic effects of a helicopter external load combination by simulating flight using a computer. Design criteria for sling members and hard points of the system were also established. A computerized hybrid simulation of the coupled motion of a CH-54 helicopter and selected external loads was conducted in real time with a pilot in the loop on both fixed-base and moving-base simulators. The results of the study indicate that the dynamic load factors produced in sling elements and at hard points during a maneuver often exceed the normal load factor developed by the helicopter. Data is included for the various loads and maneuvers.

Dynamic response of circular plates subjected to transverse impulsive loads

Abstract: The behaviours of dynamical stresses acting in the circular plate subjected to transverse impulsive loads are investigated. The cases are treated where a rigid body with spring collides with the circular plate having a hole at its center along its inner edge. The relationships between dynamic load factors (D.L.F.) with respect to bending moments, solid viscosities and spring are obtained. Experiments are carried out and theoretical results are compared with experimental ones.

Dynamic evaluation of timber posts for highway guardrails

Abstract: AN EXPERIMENTAL PROGRAM WAS PERFORMED ON GUARDRAIL POSTS TO LEARN THE MORE SIGNIFICANT DYNAMIC PROPERTIES. A SPECIAL PENDULUM IMPACT FACILITY WAS USED TO SUBJECT TEST SPECIMENS TO DYNAMIC LOADING THAT SIMULATED A VEHICLE-GUARDRAIL INSTALLATION COLLISION. ONE HUNDRED SPECIMENS OF DOUGLAS FIR, SOUTHERN PINE, RED OAK, AND RED PINE WOOD WERE EVALUATED; FOR COMPARISON 6B8.5 AND 315.7 STEEL MEMBERS WERE TESTED. SIZES OF WOOD POSTS RANGED FROM 4 BY 4 IN. TO 8 BY 8 IN. IN CROSS SECTION. THE POST SPECIMENS WERE RIGIDLY SECURED IN A BASE FIXTURE, AND THE DYNAMIC LOAD WAS APPLIED 24 IN. ABOVE GRADE. BASIC TEST DATA INCLUDE A COMPLETE LOAD RESISTANCE-POST DEFLECTION DETERMINATION FOR EACH SPECIMEN. THE DYNAMIC PROPERTIES OF PEAK RESISTANCE FORCE, AVERAGE RESISTANCE FORCE, AND FRACTURE ENERGY ARE REPORTED FOR WOOD SPECIES AND STEEL MEMBERS. TEST RESULTS SHOW THAT, WHILE DATA SCATTER EXIST WITHIN A WOOD SPECIES AND SIZE TEST GROUP, THE AVERAGE VALUES OF SUCH GROUPS CAN BE PLOTTED IN A MANNER TO GIVE MEANINGFUL TRENDS. PEAK FORCE, AVERAGE FORCE, AND FRACTURE ENERGY ARE SHOWN TO BE A DIRECT AND LINEAR FUNCTION OF MOMENT OF INERTIA. /AUTHOR/

Measured dynamic-load factors of cantilever beams, frame structures and rings subjected to impulsive loads

Abstract: The behavior of dynamical stresses of members and structures subjected to impulsive loads is investigated experimentally. Since it is very difficult to apply step impulsive loads, the statically applied loads are released abruptly and dynamic stresses measured. Experiments are carried out for the cases of cantilever beams, frame structures and rings. From the experimental results, it becomes evident that dynamic-load factors are influenced remarkably by solid viscosities and frequency.

Effect of Vibration on the Performance of Off-Road Vehicles

Abstract: : This paper first describes an experimental study on the effect of vertical vibration on shearing characteristics between vehicle running gear and terrain under simulated operating conditions. It is found that the amplitude of dynamic load and slip velocity have a profound effect on the horizontal shearing force developed on vehicular ground contact areas. In general, the higher the amplitude of dynamic load and the lower the slip velocity, the less the horizontal shearing force will be developed. The second part of the paper is devoted to the examination of the relationship between vehicle vibration and surface irregularity. By integrating the results of the study on vehicle vibration excited by surface roughness with the experimental results concerning the effect of vibration on vehicle-terrain interaction, a general framework correlating vehicle vibration and vehicle performance with terrain conditions is established. (Author)

Gear design--dynamic loads

Abstract: Two distinct components comprise the total load carried by gear teeth. These are the useful or transmitted load, and the other, the dynamic load, is a waste load caused by gear errors. The article presents a reasonably accurate method for determining the dynamic load on a gear for both spur gears and helical gears. The article then gives examples from experience of the advantages of helical gears over spur gears and of the importance of considering the dynamic loading of gears in the design stage. The conclusion is that the method given is a useful design tool which can be used to evaluate the load of any spur or helical gear at both low and high speeds and under different conditions of loading.

Axial Impact of Low Carbon Mild Steel Rod

Abstract: Behavior of viscoplastic material under dynamic load was considered for two cases; that is, a longitudinal impact of a rigid mass on a finite rod and a normal impact of a finite rod on a rigid wall. Constitutive equation of Bingham type was modified by taking strain-hardening effect into account. As governing equations of the problems were of nonlinear type with moving boundaries, the difference method was employed to solve them. Numerical results for distributions of particle velocities and of strains and their variations with respect to time differed even qualitatively from the results obtained by a theory without strain-hardening. Experiments on a soft mild steel containing 0.015% carbon were conducted. It was found that the numerical results and experiments for permanent strain distribution agreed well. Variations of strain distribution with respect to time during impact were observed by a high speed camera and numerical results were found to predict the behavior qualitatively.