Investigation on the Application of Taylor Impact Test to High-G Loading

Taylor impact test is characterized by high impact energy, low cost, and good repeatability, giving it the technical foundation and development potential for application in high-g loading. In this paper, the feasibility of performing high-g load impact testing to a missile-borne recorder by conducting Taylor impact test was studied by combining simulation analyses with experimental verification. Acccording to the actual dimensions of the missile-borne recorder, an experimental piece was designed based on the Taylor impact principle. The impact loading characteristics of the missile-borne recorder were then simulated and analyzed at different impact velocities. In addition, the peak acceleration function and the pulse duration function of the load were fitted to guide the experimental design. A Taylor-Hopkinson impact experiment was also conducted to measure the impact load that was actually experienced by the missile-borne recorder and the results were compared with the results of strain measurements on the Hopkinson incident bar. The results showed that the peak value of impact load, the pulse duration and the waveform of the actual experimental results were in good agreement with the results predicted by the simulations. Additionally, the strain data measured on the incident bar could be used to verify or replace the acceleration testing of the specimen to simplify the experimental process required. Based on the impact velocity, high-g loading impact was achieved with peak values in the 7,000–30,000 g range and durations of 1.3–1 ms, and the waveform generated was a sawtooth wave. The research results provide a new approach for high amplitude and long pulse duration impact loading to large-mass components, and broaden the application field of Taylor impact test.

Load Characteristics in Taylor Impact Test on Projectiles with Various Nose Shapes

This study focused on the impact load produced by a projectile and its potential application in the Taylor impact test. Taylor impact tests were designed and carried out for projectiles with four types of nose shapes, and the impact deformation characteristics and variation of the impact load as a function of the nose shape and impact velocity were studied. The overall high g loading experienced by the projectile body during the impact was discussed, and based on classical Taylor impact theory, impact analysis models for the various nose-shape projectiles were established and the causes of the different impact load pulse shapes were analyzed. This study reveals that the nose shape has a significant effect on the impact load waveform and pulse duration characteristics, while the impact velocity primarily affects the peak value of the impact load. Thus, the loading of specific impact environments could be regulated by the projectile nose shape design and impact velocity control, and the impact load could be simulated. Research results support the assumption that the Taylor impact test can be applied to high g loading test.

Finite element modelling of the Taylor impact test in 3D with the Coupled Eulerian-Lagrangian method

When modelling a cutting operation, the constitutive model of the machined material is one of the key parameters to obtain accurate and realistic results. Up to now, the Johnson-Cook model is still the most used, even if an increasing number of models, such as the Hyperbolic TANgent (TANH) model, were introduced last years to overcome its limitations and come closer to the actual material behaviour. Experimental tests on dedicated equipment are usually required to identify the parameters of the constitutive models. This paper introduces the Coupled Eulerian-Lagrangian (CEL) formalism to model in 3D the Taylor impact test, one of the common tests to perform that parameters identification. Indeed, one identification way involves modelling the test to determine the constitutive model parameters by comparing the experimental and the numerical samples geometries. The developed CEL model is validated against a Lagrangian reference model for a steel alloy and the Johnson-Cook constitutive model. The main goal of using the CEL method is to get rid of the elements distortion due to the high strains and strain rates during the test. Mesh dependence of the results is highlighted and a recommendation is provided on the mesh to adopt for future work. The CEL model of the 3D Taylor impact test is then extended to the use of the TANH model. The results are finally compared with that of the Johnson-Cook constitutive model.

A Study on Measuring Distribution of Temperature for Instrumented Taylor Impact Test

It is a challenge to apply the infrared detector to a test at higher strain rate because lots of articles report that the detector has an extremelyhigh responsiveness. However, all the research works about the measurement of temperature is focused on 103 s-1 of the strain rate achieved by the split Hopkinson pressure bar test. To evaluate the thermo-mechanical behaviour of materials in higher strain rate range, a method for measuring the temperature in Taylor impact test is required to establish. Additionally, a use of the fiber should be considered to protect the detector from any damages by the impact of the specimen and realize the measurement in the point-like area. In this study, an optically-measuring system of temperature with the infrared detector and PIR fiber is designed. Then, the designed system is introduced into the apparatus based on the instrumented Taylor impact test proposed recently. The temperature rise at a local point on the surface of pure aluminium is measured during the test. Then, a calculation for distribution of temperature from a heat conduction equation is proposed.

Finite Element Analysis on a Newly-Modified Method for the Taylor Impact Test to Measure the Stress-Strain Curve by the Only Single Test Using Pure Aluminum

In this study, finite element analyses are performed to obtain a stress-strain curve for ductile materials by a combination between the distributions of axial stress and strain at a certain time as a result of one single Taylor impact test. In the modified Taylor impact test proposed here, a measurement of the external impact force by the Hopkinson pressure bar placed instead of the rigid wall, and an assumption of bi-linear distribution of an axial internal force, are introduced as well as a measurement of deformed profiles at certain time. In order to obtain the realistic results by computations, at first, the parameters in a nonlinear rate sensitive hardening law are identified from the quasi-static and impact tests of pure aluminum at various strain rates and temperature conducted. In the impact test, a miniaturized testing apparatus based on the split Hopkinson pressure bar (SHPB) technique is introduced to achieve a similar level of strain rate as 104 s−1, to the Taylor test. Then, a finite element simulation of the modified test is performed using a commercial software by using the user-subroutine for the hardening law with the identified parameters. By comparing the stress-strain curves obtained by the proposed method and direct calculation of the hardening law, the validity is discussed. Finally, the feasibility of the proposed method is studied.