Piercing of Cylindrical Tubes

1981 ◽  
Vol 103 (3) ◽  
pp. 255-260 ◽  
Author(s):  
W. Johnson ◽  
S. R. Reid ◽  
S. K. Ghosh
Keyword(s):  
High Speed ◽  
Tube Length ◽  
Dynamic Tests ◽  
Central Section ◽  
Penetration Process ◽  
Static Tests ◽  
Modes Of Failure ◽  
Sequence Of Events ◽  
Punch Load ◽  
Cylindrical Tubes

Experiments are described in which cylindrical tubes were perforated normally at their central section. Quasi-static tests were performed using mainly square-section punches possessing pointed pyramidal heads of semi-angle 30 deg, the tubes being supported along their support generator. The dynamic tests comprised high-speed penetration of tubes using conically headed cylindrical projectiles. The equipment and experimental procedures are briefly described and results are presented showing typical punch load-penetration curves, the variation of punch load with tube length and that of a nondimensional characteristic punch load (defined later) with length-to-diameter ratio of the tubes. Typical specimens and the sequence of events during the course of a penetration process are also illustrated. The characteristics of petalling and plugging modes of failure together with those effects which are specifically dynamic in character are reported.

scholarly journals An Automated Real-Time Localization System in Highway and Tunnel Using UWB DL-TDoA Technology

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Long Wen ◽  
Jinkun Han ◽  
Liangliang Song ◽  
Qi Zhang ◽  
Kai Li ◽  
...  
Keyword(s):  
Real Time ◽  
High Speed ◽  
Signal Propagation ◽  
Time Difference ◽  
Base Stations ◽  
Ultra Wideband ◽  
Shielding Effect ◽  
Dynamic Tests ◽  
Static Tests ◽  
Localization System

There exists an electromagnetic shielding effect on radio signals in a tunnel, which results in no satellite positioning signal in the tunnel scenario. Moreover, because vehicles always drive at a high speed on the highway, the real-time localization system (RTLS) has a bottleneck in a highway scenario. Thus, the navigation and positioning service in tunnel and highway is an important technology difficulty in the construction of a smart transportation system. In this paper, a new technology combined downlink time difference of arrival (DL-TDoA) is proposed to realize precise and automated RTLS in tunnel and highway scenarios. The DL-TDoA inherits ultra-wideband (UWB) technology to measure the time difference of radio signal propagation between the location tag and four different location base stations, to obtain the distance differences between the location tag and four groups of location base stations. The proposed solution achieves a higher positioning efficiency and positioning capacity to achieve dynamic RTLS. The DL-TDoA technology based on UWB has several advantages in precise positioning and navigation, such as positioning accuracy, security, anti-interference, and power consumption. In the final experiments on both static and dynamic tests, DL-TDoA represents high accuracy and the mean errors of 11.96 cm, 37.11 cm, 50.06 cm, and 87.03 cm in the scenarios of static tests and 30 km/h, 60 km/h, and 80 km/h in dynamic tests, respectively, which satisfy the requirements of RTLS.

Static and Dynamic Bending Responses of the Human Cervical Spine

1998 ◽  
Vol 120 (6) ◽  
pp. 693-696 ◽  
Author(s):  
L. M. Voo ◽  
F. A. Pintar ◽  
N. Yoganandan ◽  
Y. K. Liu
Keyword(s):  
Cervical Spine ◽  
High Speed ◽  
Dynamic Stiffness ◽  
Bending Moment ◽  
Dynamic Tests ◽  
Validation Data ◽  
Static Tests ◽  
Lumped Parameter ◽  
Lumped Parameter Models ◽  
Dynamic Bending

The quasi-static and dynamic bending responses of the human mid-lower cervical spine were determined using cadaver intervertebral joints fixed at the base to a six-axis load cell. Flexion bending moment was applied to the superior end of the specimen using an electrohydraulic piston. Each specimen was tested under three cycles of quasi-static load-unload and one high-speed dynamic load. A total of five specimens were included in this study. The maximum intervertebral rotation ranged from 11.0 to 15.4 deg for quasi-static tests and from 22.9 to 34.4 deg for dynamic tests. The resulting peak moments at the center of the intervertebral joint ranged from 3.8 to 6.9 Nm for quasi-static tests and from 14.0 to 31.8 Nm for dynamic tests. The quasi-static stiffness ranged from 0.80 to 1.35 Nm/deg with a mean of 1.03 Nm/deg (±0.11 Nm/deg). The dynamic stiffness ranged from 1.08 to 2.00 Nm/deg with a mean of 1.50 Nm/deg (±0.17 Nm/deg). The differences between the two stiffnesses were statistically significant (p < 0.01). Exponential functions were derived to describe the quasi-static and dynamic moment-rotation responses. These results provide input data for lumped-parameter models and validation data for finite element models to better investigate the biomechanics of the human cervical spine.

Dynamic Axial Compression of Square CFRP/Aluminium Tubes

2019 ◽  
Vol 794 ◽  
pp. 202-207
Author(s):  
Rafea Dakhil Hussein ◽  
Dong Ruan ◽  
Guo Xing Lu ◽  
Jeong Whan Yoon ◽  
Zhan Yuan Gao
Keyword(s):  
Energy Absorption ◽  
Specific Energy ◽  
Fibre Composite ◽  
Dynamic Tests ◽  
Carbon Fibre Composite ◽  
Specific Energy Absorption ◽  
Static Tests ◽  
Crushing Force ◽  
Cfrp Tubes ◽  
The Impact

Carbon fibre composite tubes have high strength to weight ratios and outstanding performance under axial crushing. In this paper, square CFRP tubes and aluminium sheet-wrapped CFRP tubes were impacted by a drop mass to investigate the effect of loading velocity on the energy absorption of CFRP/aluminium tubes. A comparison of the quasi-static and dynamic crushing behaviours of tubes was made in terms of deformation mode, peak crushing force, mean crushing force, energy absorption and specific energy absorption. The influence of the number of aluminium layers that wrapped square CFRP tubes on the crushing performance of tubes under axial impact was also examined. Experimental results manifested similar deformation modes of tubes in both quasi-static and dynamic tests. The dynamic peak crushing force was higher than the quasi-static counterpart, while mean crushing force, energy absorption and specific energy absorption were lower in dynamic tests than those in quasi-static tests. The mean crushing force and energy absorption decreased with the crushing velocity and increased with the number of aluminium layers. The impact stroke (when the force starts to drop) decreased with the number of aluminium layers.

Experimental Assessment of the Dynamic Behavior of Polyolefin Thermoplastic Hot Melt Adhesive

2018 ◽  
Author(s):  
Raffaele Ciardiello ◽  
Andrea Tridello ◽  
Luca Goglio ◽  
Giovanni Belingardi
Keyword(s):  
Failure Modes ◽  
Industrial Applications ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Dynamic Tests ◽  
Cohesive Failure ◽  
Static Tests ◽  
Piping Systems ◽  
The Many ◽  
Hot Melt

In the last decades, the use of adhesives has rapidly increased in many industrial fields. Adhesive joints are often preferred to traditional fasteners due to the many advantages that they offer. For instance, adhesive joints show a better stress distribution compared to the traditional fasteners and high mechanical properties under different loading conditions. Furthermore, they are usually preferred for joining components made of different materials. A wide variety of adhesives is currently available: thermoset adhesives are generally employed for structural joints but recently there has been a significant increment in the use of thermoplastic adhesives, in particular of the hot-melt adhesives (HMAs). HMAs permit to bond a large number of materials, including metal and plastics (e.g., polypropylene, PP), which can be hardly bonded with traditional adhesives. Furthermore, HMAs are characterized by a short open time and, therefore, permit for a quick and easy assembly process since they can be easily spread on the adherend surfaces by means of a hot-melt gun and they offer the opportunity of an ease disassembling process for repair and recycle. For all these reasons, HMAs are employed in many industrial applications and are currently used also for bonding polypropylene and polyolefin piping systems. In the present paper, the dynamic response of single lap joints (SLJ) obtained by bonding together with a polyolefin HMA two polypropylene substrates was experimentally assessed. Quasi-static tests and dynamic tests were carried out to investigate the strain rate effect: dynamic tests were carried out with a modified instrumented impact pendulum. Relevant changes in the joint performance have been put in evidence. Failure modes were finally analysed and compared. A change in the failure mode is experimentally found: in quasi-static tests SLJ failed due to a cohesive failure of the adhesive, whereas in dynamic tests the SLJ failed due to an interfacial failure, with a low energy absorption.

Propelling Nozzle Research

1964 ◽  
Vol 68 (647) ◽  
pp. 717-727 ◽  
Author(s):  
W. G. E. Lewis
Keyword(s):  
High Speed ◽  
High Performance ◽  
Research Programme ◽  
Static Tests ◽  
Transport Aircraft ◽  
Supersonic Transport ◽  
Design Behaviour ◽  
Base Bleed ◽  
Critical Phases ◽  
The Ideal

SummaryThe current interest in supersonic transport aircraft makes it appropriate to consider the problems of propulsion nozzle systems for high speed flight. The discussion will be confined mainly to this field of activity.In the absence of external drag and weight factors, the ideal configuration to maintain optimum thrust at all flight speeds would employ a mechanically variable area ratio nozzle. By such means the jet flow could be fully and properly expanded at all times.A practical design to accommodate such variations is inherently complex, and so an alternative solution using aerodynamic techniques has been sought. It is necessary to remember that the success of whatever method is eventually chosen must rest on its ability to combine a high performance at cruise with very small loss during other critical phases of the flight plan.This paper describes some of the results of a nozzle research programme aimed primarily at solving the above problem, with an attempt to explain the philosophy behind the aerodynamic techniques tried. Some discussion is given of the experimental difficulties in establishing a sufficiently accurate standard of measurement for design point performance. In a few chosen configurations experimental results have been extensively backed by theoretical studies.The need to demonstrate off-design behaviour in the presence of an external flow field is stressed, with special reference to the misleading results often obtained from static tests.Finally, some attention is given to the question of base bleed, with its repercussions on the installation of the propulsion nozzle in an aircraft.

Effect of Loading Rate on Tensile Properties of Automotive Steel Sheet

2013 ◽  
Vol 690-693 ◽  
pp. 211-217
Author(s):  
Jin Gui Qin ◽  
Fang Yun Lu ◽  
Yu Liang Lin ◽  
Xue Jun Wen
Keyword(s):  
Strain Rate ◽  
Testing Machine ◽  
Structural Response ◽  
Tensile Tests ◽  
Dynamic Tests ◽  
Static Tests ◽  
Split Hopkinson Tensile Bar ◽  
Axial Tensile ◽  
Static Tensile ◽  
Cook Model

Results of uni-axial tensile loading of three automotive steels at different strain rates (0.0011–3200s-1) are reported here. Quasi-static tensile tests were performed under the strain rate of 1.1×10-3 s-1 using an electromechanical universal testing machine, whereas dynamic tests were carried out under the strain rate in the range of 1100 to 3200 s-1 using a Split Hopkinson Tensile Bar apparatus. Based on the experimental results, the material parameters of widely used Johnson–Cook model which described the strain rate and temperature-dependent of mechanical behaviour were determined. The experiments show that strain-rate hardening is superior to thermal softening: yield stresses, tensile strength, deformation, and energy dissipation increase with the strain rate from quasi-static tests to dynamic tests. The Johnson–Cook model can describe the behaviour of these steels and provides the opportunity to study the material and structural response.

Stress Triaxiality in Chip Segmentation During High Speed Machining of Titanium Alloy

2014 ◽  
Author(s):  
Xueping Zhang ◽  
Rajiv Shivpuri ◽  
Anil K. Srivastava
Keyword(s):  
Titanium Alloy ◽  
High Speed ◽  
Split Hopkinson Pressure Bar ◽  
Shear Bands ◽  
Stress Triaxiality ◽  
Machining Process ◽  
High Speed Machining ◽  
Hopkinson Pressure Bar ◽  
Static Tests ◽  
Pressure Stress

Beside strain intensity, stress triaxiality (pressure-stress states) is the most important factor to control initiation of ductile fracture in chip segmentation through affecting the loading capacity and strain to failure. The effect of stress triaxiality on failure strain is usually assessed by dynamic Split Hopkinson Pressure Bar (SHPB) or quasi-static tests of tension, compression, torsion, and shear. However, the stress triaxialities produced by these tests are considerably different from those in high speed machining of titanium alloys where adiabatic shear bands (ASB) are associated with much higher strains, stresses and temperatures. This aspect of shear localization and fracture are poorly understood in previous research. This paper aims to demonstrate the role of stress triaxiality in chip segmentation during machining titanium alloy using finite element method. This research promotes a fundamental understanding of thermo-mechanics of the high-speed machining process, and provides a logical insight into the fracture mechanism in discontinuous chips.

Experimental investigation of the quasi-static and impact tests on the energy absorption characteristics of coupler rubber buffers used in railway vehicles

2018 ◽  
Vol 233 (9) ◽  
pp. 937-950 ◽  
Author(s):  
Shuguang Yao ◽  
Zhixiang Li ◽  
Wen Ma ◽  
Ping Xu ◽  
Quanwei Che
Keyword(s):  
Energy Absorption ◽  
Impact Velocity ◽  
High Speed ◽  
Compression Tests ◽  
Static Compression ◽  
Static Tests ◽  
Impact Tests ◽  
High Speed Trains ◽  
The Impact ◽  
Absorption Characteristics

Coupler rubber buffers are widely used in high-speed trains, to dissipate the impact energy between vehicles. The rubber buffer consists of two groups of rubbers, which are pre-compressed and then installed into the frame body. This paper specifically focuses on the energy absorption characteristics of the rubber buffers. Firstly, quasi-static compression tests were carried out for one and three pairs of rubber sheets, and the relationship between the energy absorption responses, i.e. Eabn  =  n ×  Eab1, Edissn =  n ×  Ediss1, and Ean =  Ea1, was obtained. Next, a series of quasi-static tests were performed for one pair of rubber sheet to investigate the energy absorption performance with different compression ratios of the rubber buffers. Then, impact tests with five impact velocities were conducted, and the coupler knuckle was destroyed when the impact velocity was 10.807 km/h. The results of the impact tests showed that with the increase of the impact velocity, the Eab, Ediss, and Ea of the rear buffer increased significantly, but the three responses of the front buffer did not increase much. Finally, the results of the impact tests and quasi-static tests were contrastively analyzed, which showed that with the increase of the stroke, the values of Eab, Ediss, and Ea increased. However, the increasing rates of the impact tests were higher than that of the quasi-static tests. The maximum value of Ea was 68.76% in the impact tests, which was relatively a high value for the vehicle coupler buffer. The energy capacity of the rear buffer for dynamic loading was determined as 22.98 kJ.

scholarly journals Study on the Composite Structure of Aluminum Foam-Filled Thin-Walled Metal Tube to Reduce the Charge Overload inside the Projectile during the Penetration Process

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Fudi Liang ◽  
Zengyou Liang ◽  
Dezhi Deng
Keyword(s):  
Reinforced Concrete ◽  
Stress Analysis ◽  
Composite Structure ◽  
High Speed ◽  
Aluminum Foam ◽  
Metal Tube ◽  
Penetration Process ◽  
Mathematical Expressions ◽  
Foam Filled ◽  
Thin Walled

When a projectile penetrates a target at high speed, the charge loaded inside the projectile usually bears a high overload, which will consequently severely affect its performance. In order to reduce the overload of the charge during the penetration process, the structure of the projectile was improved by adding two buffers at both ends of the charge. In this study, the mathematical expressions were first gained about the axial buffering force generated by the thin-walled metal tube, aluminum foam, and the composite structure of aluminum foam-filled thin-walled metal tube when they were impacted by the high-speed mass block through reasonable assumptions and stress analysis. During the experiment on the high-speed projectile penetrating reinforced concrete target, the acceleration curve of the charge and the projectile body were obtained. The results show that the maximum overload that the charge was subjected to during the launch and penetration process was significantly reduced, and the change in overload, which the charge was subjected to during the penetration process, was also less obvious.

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