The strain rate is found to be controlled by the stress and strain of the deforming specimen, geometry the length and diameter of specimen, impedance of bar, and impact velocity. In hopkinson test, two identical shunt machines are required which are coupled both mechanically and electrically in parallel. H output bar out t output bar specimen one force measurement output bar only l out out out c t l 2. John hopkinson, in 1872, studiedfor the first timethe behavior of iron wires by performing stress wave experiments. The high strain rate characterization of materials is usually performed using the split hopkinson pressure bar within the strain rate range 1000 s1. The splithopkinson pressure bar, named after bertram hopkinson, sometimes also called a kolsky bar, is an apparatus for testing the dynamic stress strain response of materials. Design of a split hopkinson bar apparatus for use with fiber. The theory is used to discuss the errors in the experiments caused by the pressure bar itself, and it is shown that bars about 2 ft. The theory governing the specifics of hopkinson bar testing has been around for decades. At this point, the test carries on as in the standard hopkinson bar. Jrce volume 4 issue 1 pages 6377 strength of materials. The split hopkinson pressure bar is a device used for characterizing material properties submitted to dynamic loading, producing high stress and strain waves. In 1914, his son bertram hopkinson 30 continued his work by using a long elastic bar to determine the pressures produced by the impact of a bullet or by a detonation of an explosive. Shpb is suitable for high strain rate test in strain rate range of 102 to 104 s1.
D 20 mm specimen characteristics for simplified theoretical analysis. Hopkinson bar technique ut specimen v 0 striker direct impact experiment. The basic theory of how to reduce the pressure bar data based upon one dimensional stress wave analysis, as presented in the theory of the split hopkinson. Design, fabrication and analysis of thermal storage solar cooker prototype. The kolsky bar loading device is essentially the same as a universal testing system for compression. The validity and applicability of the assumption made in the 1d hopkinson bar theory are discussed.
It has only been the last decade or so, however, that. One of these two machines is operated as a generator to supply the mechanical power to the motor. Design, construction and test of a tesla coil, frank grady mccoy. The theory of a propagating wave through an iron wire by transferring the energy of a dropping weight was described. Experiment ends before leftward traveling wave in output bar reaches strain gage. A series of relatively stable experimental results of dynamic compressive strength versus strain rate and a linear fitting curve have. The dynamic compressive behavior of ice is investigated using a largesized 37 mm in diameter modified aluminum split hopkinson pressure bar shpb with pulse shaper at the strain rate from 500 s1 to 1200 s1. Hopkinson bar experiment typical system characteristics. Robust models that capture the materials response at different strain rates are important. The splithopkinson pressure bar shpb test is one of the most versatile methods. The strain rate is found to be controlled by the stress and strain of the. All books are in clear copy here, and all files are secure so dont worry about it. Jrce volume 4 issue 1 pages 6377 free download as pdf file.
Tension testing in a split hopkinson pressure bar shpb is more complex due to a variation of loading methods and specimen attachment to the incident and transmission bar. Split hopkinson bar, which can test materials at strain rates as high as 2000 s1. The mechanical properties of materials change depending upon the strain rate that they are subject to. One is acting as a motor and another one as a generator.
Hopkinsons test is another useful method of testing the efficiency of a dc machine. The most widely used method to characterise materials at high strain rates is the split hopkinson pressure bar shpb. Example 8 hopkinson bar summary precise data for high strain rate materials is necessary to enable the accurate modeling of highspeed impacts. Rittel an educational visualization technique for kolsky split hopkinson bar he present paper introduces a simple educational. In the following, we will first describe the testing methodology of the shrb test, then our experimental setup and the. Advancements in the split hopkinson bar test vtechworks. Because this sample geometry is the same as the split hopkinson pressure bar test used primarily for largestrain, dynamic impact experiments, we call this technique the. Build a compression split hopkinson bar apparatus to validate theory and prove. Theoretical and experimental pressurevelocity data for striker bar of length. The first tension bar was designed and tested by harding et al. It is designed to demonstrate the fundamental concepts and also facilitates easy learning about two similar machines are required to carry out hopkinson s test.
High strain rate hopkinson bar analysis trilion has installed a high speed aramis system on the split hopkinson bar at the university of michigandearborn, where dr. Hopkinson s test hopkinson s test is also known as regenerative test, back to back test and heat run test. Development of a hopkinson bar apparatus for testing soft. Hopkinsons test of dc machine premier engineering lab. Elementary planewave propagation theory can be used for evaluating the. Content posted in 2015 iowa research online university.
Since then there have been numerous advances in experi technique that allows t. The specimen strain rate in the split hopkinson bar shb test has been formulated based on a onedimensional assumption. This test overcomes the drawback of swinburnes test, which does not take any account of the stray load losses occurring in dc machines under loaded condition. Evolution of specimen strain rate in split hopkinson bar test. Application of the split hopkinson resonant bar test for. Alan argento and their graduate students are studying various engineering materials.
Fundamentals of the hopkinson bar experimental procedure are outlined including bar calibration, specimen design, pulse shaping, and data analysis following the essential dispersion correction methodology. The input to the motor is given by the supply mains. It is a full load test and it requires two identical machines which are coupled to each other. Classic splithopkinson pressure bar testing mechanical testing. Theory the efficiency of the dc machine can be accurately determined by the regenerative method, normally known as hopkinson s test. Please click button to get split hopkinson pressure bar technique book now. Hopkinsons test of dc machine premier hopkinsons test of dc machine is an adaptable training system for electrical laboratory. Split hopkinson pressure bar an overview sciencedirect topics. Design and test of a lighting system for the trinity episcopal church of iowa city, iowa, josiah walton hopkinson. Split hopkinson pressure bar technique download ebook. Length of output bar duration of the experiment strategy.
760 129 1011 1143 172 1426 132 111 315 523 865 709 1300 851 1398 1238 494 336 914 487 487 94 1038 173 567 1410 664 543 1186 510 754 58 187