34 research outputs found
A dynamic model and performance analysis of a stepped rotary flow control valve
The hydraulic independent metering (IM) is an advanced actuator driving technique
that allows the implementation of advanced control algorithms or methods. The
main concept of IM is to control hydraulic actuators ports, which are the meterin and meter-out, separately. In this paper, a novel stepped rotary type valve
has been developed for embedding in hydraulic independent metering systems,
instead of conventional types such as poppet and spool. The insertion leads to
developing different and novel control techniques, which require a software in loop
and hardware in loop simulation of the proposed system. The paper explores the
dynamic representation of this valve and defines its own performance limitations.
This includes the development of a linear model comprising its two main sub-parts
which are the stepper motor and the rotary orifice. Consequently, the linear timeinvariant methods are used to explore the performance of the valve by considering
the effect of different parameters namely the pressure drop, friction coefficient,
damping coefficient and bristle coefficient
Fatigue and fracture analysis of a sevenâwire stainless steel strand under axial and bending loads
Fatigue failure of cables and strands is a common and complex problem. Failure is typically caused by different combinations of timeâvariable bending and axial forces. In addition to these loads, contact stresses between wires may play an important role in the fatigue failure of cables. The present work aims to provide deep insight into the fatigue failure of a sevenâwire stainless steel strand subjected to a combination of variable axial and bending loads. To avoid side effects in the analysis, fatigue failure of the strand close to the clamps is prevented. Several tests were performed with a new device specifically designed to avoid failure near the clamps. Thus, failure is always produced at the middle length of the specimen. Test simulations were performed by employing the finite element method. The numerical results were validated via comparisons with experimental data. Finally, life prediction curves were obtained.The authors wish to express their gratitude to the Ministry of Economy and Competitiveness for funding the research of the DPI2014â59160âP project