High-speed Dynamic Test Research Articles

Kinematic characteristics of banana screen surface and operational parameter optimization for coal classification

ABSTRACT Screening is an indispensable unit operation that is used extensively in many industries to separate particulate materials into different size fractions. A banana screen has high screening efficiency and is widely used for coal classification. In this study, the kinematic characteristics and velocity distribution of the banana screen surface during equal-thickness screening were investigated. High-speed dynamic test system results showed that the migration velocity and distance of different screen surface stages increase with running time from point 1 to point 5. Based on the experimental data and Box–Behnken response surface methodology results, the best screening effect occurred when the angle of eccentric blockψ was 100°, the excitation frequency f was 34 Hz and the feed rate Q was 3 kg/s. Furthermore, the sequence of influencing degree of various factors on screening efficiency η followed the order: f > ψ > Q. The actual screening efficiency was 92.993% when the operating conditions wereψ = 103°, f = 32 Hz, and Q = 3.5 kg/s, indicating a satisfactory screening performance of coal using a banana screen.

Quasi-static and dynamic tensile properties of fiberglass/epoxy laminate sheet

Fiberglass/epoxy laminate or structures strengthened by fiberglass/epoxy laminate might be subjected to dynamic loadings such as impact and blast. Understanding the dynamic material properties of the fiberglass/epoxy laminate is important to predict the behavior of fiberglass/epoxy laminate or its strengthened structure against dynamic loading. In this study, unidirectional quasi-static and dynamic tensile tests on fiberglass/epoxy laminate were carried out to investigate its dynamic material properties. The strain rate for quasi-static and low velocity test varied from 2.08E-05 to 1.04E-01s−1. The high speed dynamic tests were conducted by INSTRON® VHS 160/100-20 machine at the strain rate from 2.75 to 115s−1. The strain rate effects on the tensile strength, failure strain and Young’s Modulus of fiberglass/epoxy laminate were investigated. Based on the testing data, empirical formulae were derived to predict the dynamic enhancement of tensile material properties of fiberglass/epoxy laminate as a function of strain rates, which can be used to model the dynamic material properties in the numerical simulation of structural responses.

Studies on the static and dynamic properties of different types of polyester industrial yarns

Four major types of polyester industrial yarns, viz. high tenacity (HT), high modulus low shrinkage (HMLS), low shrinkage (LS) and super low shrinkage (SLS) polyester yarns, were studied for their static and dynamic properties. An attempt has been made to establish a linkage between static and dynamic properties of these yarns with its structure and with its end applications. HMLS and HT polyester yarns have lower tan δ and work loss, which are the desired characteristics required for its end applications which include tire and conveyer belt. Higher overall orientation and higher fraction of tie molecules helped to achieve these properties in HT and HMLS polyester yarns. LS and SLS polyester yarns are mostly used for static applications. Low thermal shrinkage is the key requirement for the downstream processes of these yarns. Lower amorphous orientation in these two yarns is primarily responsible for achieving very low thermal shrinkage. A good co-relation has been established between the peak temperature of work loss (in slow speed hysteresis test) and the peak temperature of tan δ (in high-speed dynamic test).

Dynamic mechanical properties of whisker/PA66 composites at high strain rates

PA66 reinforced with potassium titanate whisker (TKW) treated with silane coupling agent were prepared using a twin-screw extruder. The quasi-static and dynamic mechanical properties were investigated. Addition of 40 wt % TKW to PA66 improves all the investigated properties. The high-speed dynamic tests with TKW/PA66 were carried on split Hopkinson pressure bar (SHPB). The loading pulses in SHPB experiments were precisely controlled to ensure that the composite specimens deformed at a nearly constant strain rate under dynamically equilibrated stress during dynamic compression. The constitutive curves and equations at high strain rates have been obtained. TKW/PA66 composites show 20–100% increase on reference modulus and 20% increase on compression strength.