scholarly journals Modelling of the Influence of Tensile Test Speed on the Fracture Load

2019 ◽  
Vol 12 ◽  
pp. 1-11
Author(s):  
Gouda Mohamed Mahmoud ◽  
Khaled Mohamed
Keyword(s):  
Statistical Analysis ◽  
Tensile Test ◽  
Fracture Zone ◽  
Fracture Process ◽  
Loading Rate ◽  
Fracture Behaviour ◽  
Fracture Load ◽  
Loading Rates ◽  
Test Speed ◽  
Experimental Characterisation

This investigation focuses on modelling the fracture zone of four materials at different test speeds. The influence of these test speeds on the fracture zone formula was investigated as well. The fracture behaviour of materials is an important parameter which greatly affects the performance of these materials. In this paper, an empirical formula was generated to predict the fracture zone. This formula was produced from experimental characterisation of the fracture process at different loading rates for some engineering materials.  Statistical analysis was done for the results being obtained from the experimental work to verify the accuracy of this formula, and it was found that it can introduce an accurate base for fracture zone prediction and determination. It was noted that at fracture process initiation, there are no significant effects of varying loading rate; this effect is increased with increasing the fracture process propagation.

EFFECT OF LOADING RATE ON FRACTURE BEHAVIOUR OF Mg-Al-Zn ALLOYS

2016 ◽  
Vol 78 (6-9) ◽  
Author(s):  
Noradila Abdul Latif ◽  
Zainuddin Sajuri ◽  
Junaidi Syarif ◽  
Yukio Miyashita
Keyword(s):  
Magnesium Alloys ◽  
Large Scale ◽  
Loading Rate ◽  
Fracture Behaviour ◽  
Maximum Load ◽  
Loading Rates ◽  
Specific Strength ◽  
Scale Yielding ◽  
The Impact ◽  
Zn Alloys

In recent years, magnesium alloys are widely used for automotive applications as structural components due to its lightweight property and high specific strength. In this regards, magnesium alloys are subjected to high velocity and impact loads during accident. Hence, understanding the impact and dynamic behaviours of magnesium alloys are essential. In this study, the effect of loading rates on the fracture behaviour of Mg-Al-Zn alloys was investigated using pre-cracked single-edge notched bending (SENB) specimens. Three-point bending tests were conducted at different loading rates of 5, 50 and 500 mm/min. The Mg-Al-Zn alloys that used in the present study were extruded AZ31 and AZ61 magnesium alloys. From the load-load line displacement results, both alloys exhibited nonlinear fracture behaviour. The maximum load (Pmax) of these two alloys increased with increasing loading rate. Comparing both alloys, AZ61 exhibited higher Pmax than that of AZ31 due to the higher volume of b-phase and smaller grain size in AZ61. Fracture surface observation revealed that both alloys fractured in ductile manner with large scale yielding and high shear lips ratio at all loading rates.

scholarly journals Size of the Fracture Process Zone in High-Strength Concrete at a Wide Range of Loading Rates

2010 ◽  
Vol 24-25 ◽  
pp. 155-160 ◽  
Author(s):  
R.C. Yu ◽  
X.X. Zhang ◽  
Gonzalo Ruiz ◽  
M. Tarifa ◽  
M. Cámara
Keyword(s):  
High Strength Concrete ◽  
Fracture Process ◽  
Fracture Process Zone ◽  
Loading Rate ◽  
Process Zone ◽  
High Strength ◽  
Experimental Program ◽  
Strength Concrete ◽  
Loading Rates ◽  
Wide Range

Compared with the extensive research on properties of the fracture process zone (FPZ) under quasi-static loading conditions, much less information is available on its dynamic characterization, especially for high-strength concrete (HSC). This paper presents the very recent results of an experimental program aimed at disclosing the loading rate effect on the size and velocity of the (FPZ) in HSC. Eighteen three-point bending specimens were conducted under a wide range of loading rates from from 10-4 mm/s to 103 mm/s using either a servo-hydraulic machine or a self-designed drop-weight impact device. Four strain gauges mounted along the ligament of the specimen were used to measure the FPZ size. Surprisingly, the FPZ size remains almost constant (around 20 mm) when the loading rate varies seven orders of magnitude.

Coarse filters for pond effluent polishing: comparison of loading rates and grain sizes

2007 ◽  
Vol 55 (11) ◽  
pp. 121-126 ◽  
Author(s):  
M. von Sperling ◽  
J.G.B. de Andrada ◽  
W.R. de Melo Júnior
Keyword(s):  
Loading Rate ◽  
Uasb Reactor ◽  
E Coli ◽  
Effluent Quality ◽  
Loading Rates ◽  
Hydraulic Loading ◽  
Grain Sizes ◽  
Belo Horizonte ◽  
The City ◽  
Rock Size

A system comprising a UASB reactor, shallow polishing ponds and shallow coarse filters, treating actual wastewater from the city of Belo Horizonte, Brazil, has been evaluated. The main focus of the research was to compare grain sizes and hydraulic loading rates in the coarse filters. Two filters operating in parallel were investigated, with the following grain sizes: Filter 1: 3 to 10 cm; Filter 2: 8 to 20 cm. Two hydraulic loading rates were tested: 0.5 and 1.0 m3/m3.d. The filter with the lower rock size had a better performance than the filter with the larger rock size in the removal of SS and, as a consequence, BOD and COD. A better performance was obtained with the hydraulic loading rate of 0.5 m3/m3.d, as compared to the rate of 1.0 m3/m3.d. The effluent quality during the period with the lower loading rate was very good for discharge into water bodies or for agricultural reuse (median effluent concentrations from Filter 1: BOD: 20 mg/L; COD: 106 mg/L; SS: 28 mg/L; E. coli: 528 MPN/100 mL).

scholarly journals Development of friction-induced triboluminescent sensor for load monitoring

2017 ◽  
Vol 29 (5) ◽  
pp. 883-895 ◽  
Author(s):  
Md Abu S Shohag ◽  
Zhengqian Jiang ◽  
Emily C Hammel ◽  
Lucas Braga Carani ◽  
David O Olawale ◽  
...  
Keyword(s):  
Applied Load ◽  
Loading Rate ◽  
Turbine Blades ◽  
Wind Turbine Blades ◽  
Loading Rates ◽  
Load Monitoring ◽  
The Coefficient Of Friction ◽  
Dynamic Structures ◽  
Sample Configuration

Real-time load monitoring of critical civil and mechanical structures especially dynamic structures such as wind turbine blades is imperative for longer service life. This article proposed a novel sensor system based on the proprietary in situ triboluminescent optical fiber (ITOF) sensor for dynamic load monitoring. The new ITOF sensor patch consists of an ITOF sensor network with micro-exciters integrated within a polymer matrix. The sensor patch was subjected to repeated flexural loading and produced triboluminescent emissions due to the friction between micro-exciters and ITOF sensors corresponding to each loading cycle. The friction-induced triboluminescent intensity directly depends on the loading rate, the coefficient of friction, and the applied load on patch. In general, the triboluminescent intensity increases exponentially with an increase in load. Additionally, the sensor patches comprising the coarser micro-exciters exhibited better results. Similarly, better results were achieved at higher loading rates although a threshold loading rate is required to excite the triboluminescent crystals for this sample configuration. The proposed new sensor has the ability to monitor dynamic continuous applied loads.

Rate dependence of serrated flow in a metallic glass

2003 ◽  
Vol 18 (4) ◽  
pp. 755-757 ◽  
Author(s):  
W. H. Jiang ◽  
M. Atzmon
Keyword(s):  
Plastic Deformation ◽  
Atomic Force Microscopy ◽  
Loading Rate ◽  
Shear Bands ◽  
Shear Band Formation ◽  
Band Formation ◽  
Serrated Flow ◽  
Force Microscopy ◽  
Loading Rates ◽  
Atomic Force

Plastic deformation of amorphous Al90Fe5Gd5 was investigated using nanoindentation and atomic force microscopy. While serrated flow was detected only at high loading rates, shear bands were observed for all loading rates, ranging from 1 to 100 nm/s. However, the details of shear-band formation depend on the loading rate.

scholarly journals Acoustic emission signatures prior to snow failure

2018 ◽  
Vol 64 (246) ◽  
pp. 543-554 ◽  
Author(s):  
ACHILLE CAPELLI ◽  
INGRID REIWEGER ◽  
JÜRG SCHWEIZER
Keyword(s):  
Loading Rate ◽  
Critical Phenomenon ◽  
Acoustic Emissions ◽  
Test Apparatus ◽  
Snow Layer ◽  
Loading Rates ◽  
Damage Process ◽  
Damage Processes ◽  
Increasing Load ◽  
Snow Samples

ABSTRACTSnow slab avalanches are caused by cracks forming and propagating in a weak snow layer below a cohesive slab. The gradual damage process leading to the formation of the initial failure within the weak layer (WL) is still not entirely understood. To this end, we designed a novel test apparatus that allows performing loading experiments with large snow samples (0.25 m2) including a WL at different loading rates and simultaneously monitoring the acoustic emissions (AE) response. By analyzing the AE generated by micro-cracking, we studied the evolution of the damage process preceding snow failure. At fast loading rates, the exponent of the AE energy distribution (b-value) gradually changed, and both the energy rate and the inverse waiting time increased exponentially with increasing load. These changes in AE signature indicate a transition from small to large events and an acceleration of the damage processes leading to brittle failure. For the experiments at slow loading rate, these changes in the AE signature were not or only partially present, even if the sample failed, indicating a different evolution of the damage process. The observed characteristics in AE response provide new insights on how to model snow failure as a critical phenomenon.

Dairy Waste Treatment with Anaerobic Stationary Fixed Film Reactors

1983 ◽  
Vol 15 (8-9) ◽  
pp. 359-368 ◽  
Author(s):  
L van den Berg ◽  
K J Kennedy
Keyword(s):  
Cheese Whey ◽  
Loading Rate ◽  
Cod Removal ◽  
High Loading ◽  
Loading Rates ◽  
Dairy Wastes ◽  
Plant Waste ◽  
Fixed Film ◽  
Dairy Plant ◽  
Removal Efficiencies

Cheese whey and a dilute waste from a cheese factory with a Chemical Oxygen Demand of 66,000 and 4,000 mg (COD)/L respectively, were treated at high loading rates in 0.7 to 1.2 L downflow anaerobic stationary fixed film reactors and an upflow sludge bed reactor. In downflow stationary fixed film reactors treating cheese whey, COD removal efficiencies of 97% were achieved at a loading rate of 5 kg COD/m3/day and 92% at a maximum loading rate of 22 kg COD/m3/day. With dairy plant waste, loading rates of up to 15 kg COD/m3/day were possible with COD removal efficiencies averaging 75%, decreasing slightly with increasing loading rates. In an upflow sludge bed reactor the COD removal efficiency of dairy plant waste, decreased from 87% at 5 kg COD/m3/day to 73% at 15 kg COD/m3/day. A stationary fixed film reactor treating a skim milk powder waste (4,000 ppm) could only be operated at up to 10 kg COD/m3/day with a treatment efficiency of 72%. Methane was produced from all wastes at rates corresponding to 0.32 m3 CH4 (0°C, 1 atm) per kg COD removed. Results show that stationary fixed film reactors are capable of treating dairy wastes at high loading rates and high COD removal efficiencies.

scholarly journals FDEM Modelling of Rock Fracture Process during Three-Point Bending Test under Quasistatic and Dynamic Loading Conditions

2021 ◽  
Vol 2021 ◽  
pp. 1-21
Author(s):  
Huaming An ◽  
Yushan Song ◽  
Hongyuan Liu
Keyword(s):  
Fracture Toughness ◽  
Dynamic Loading ◽  
Fracture Process ◽  
Loading Rate ◽  
Rock Fracture ◽  
Mesh Size ◽  
Bending Test ◽  
Loading Conditions ◽  
Three Point Bending ◽  
Dynamic Loading Conditions

A hybrid finite-discrete element method (FDEM) is proposed to model rock fracture initiation and propagation during a three-point bending test under quasistatic and dynamic loading conditions. Three fracture models have been implemented in the FDEM to model the transition from continuum to discontinuum through fracture and fragmentation. The loading rate effect on rock behaviour has been taken into account by the implementation of the relationship between the static and dynamic rock strengths derived from dynamic rock fracture experiments. The Brazilian tensile strength test has been modelled to calibrate the FDEM. The FDEM can well model the stress and fracture propagation and well show the stress distribution along the vertical diameter of the disc during the Brazilian tensile strength test. Then, FDEM is implemented to study the rock fracture process during three-point bending tests under quasistatic and dynamic loading conditions. The FDEM has well modelled the stress and fracture propagation and can obtain reasonable fracture toughness. After that, the effects of the loading rate on the rock strength and rock fracture toughness are discussed, and the mesh size and mesh orientation on the fracture patterns are also discussed. It is concluded that the FDEM can well model the rock fracture process by the implementation of the three fracture models. The FDEM can capture the loading rate effect on rock strength and rock fracture toughness. The FDEM is a valuable tool for studying the rock behaviour on the dynamic loading although the proposed method is sensitive to the mesh size and mesh orientation.

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