Indirect Tension Test Analysis

mediate Tension Test AnalysisIDTThe in steer tension trial run involves applying compressive lashings on cylindrical prototype. This would develop uniform tensile stress perp demiseicular style to direction of utilize misdirect as shows in figure1. Resulted swimming and upended tensile aberration is measured using linear variable shift key transducers(LVDTS). The pattern is shoot downed until splitting along axis of applied commit as shows in figure 2 1. Different type of payload style, temperature and device apparatus modification were used to measure various corporeal properties. IDT test have many advantages such as simplicity in accompanying test, and prepaproportionn samples. Specimens failure is started in uniform tensile stress, and it is non affected by come near condition of example make it common test in pavage . 2AC mixture properties obtained by load, shift key time plots at different payload mode and temperature as shows in figures 2. Initially, IDT was used to measure strength of specimen. It was defined as the maximum load on specimen until failure. It is loaded with constant deformation commit at specified temperature until failure. The strength was obtained by dividing peak load of specimen, on it diameter and thickness using u equation 1.The detailed procedure is depict in 4, where it was recommended to test material with 50mm/min laden rate , at 77F comparability 1WhereSt = tensile strength, kPa (psi)P = maximum load, N (lbf)t = specimen height immediately before tensile test, mm(in.),D = specimen diameter, mm (in.)Indirect Tensile Creep TestsIn addition, ITD is used to trade creep conformation test on mixture. These ranges was addressed by Superpave specification to prevent thermal cracking, also, it is one of primary inputs in ASSHTO ME practiceing method. Creep compliance represent ratio mingled with time-dependent (creep) strain to applied stress as function of time. It is reflected the stiffness and tim e-dependence of material .2.. In this test, the specimen is loaded with constant static load, that make Maximum measured swimming strain below 500-10-6 mm. trey measurement is taken at collar different temperature, selected based in PG grading of binder. The creep compliance reckon as function of time using equationS 2,3. The detailed procedure is draw in 5.Equation 2Equation 3WhereD(t) = creep compliance at time t (kPa)GL = gauge distance in meters (0.038 meters for one hundred fifty mm diameter specimens)Davg = average diameter of all specimens typically 3 (ne arest 0.001 meter)bavg = average thickness of all specimens typically 3 (nearest 0.001 meter)Pavg = average creep load (kN)Xtm,t = trimmed mean of the normalized, plane deformations (nearest 0.001meter) of all specimen faces typically 6 at time t(X/Y)absolute value of the ratio of the normalized, trimmed mean of the horizontalAlso, it was used to determine resilient modulus of pavement mixture. Resilient modulus is s tiffness measurement, reflecting material behavior within undamaged loading mode. It was defined as ratio between applied stress to recoverable strain. Within IDT device a cyclic load is applied to bump specimen enough time to recoverable it is strain. Each roll include applying compressive load, followed by rest period. Horizontal and vertical recoverable deformation is record within test as shows in figure 3. It is used to inscribe Passions ratios, to obtain the resilient modulus using equation 2 and 3. both different values of resilient modulus could be obtained, based on measured deformation. instantaneous resilient modulus depends on instantaneous recoverable deformation during unloading of for each one rhythm. bestow resilient modulus is obtained using numerate recoverable deformation including both(prenominal) instantaneous and time-dependent recoverable deformation. Detailed test procedure is described in6. Three specimens with (4 or 6) in diameter, (1.5 or 2) heigh t are well-tried at (772F). Initially, 100 loading cycles are applied, to get five stable cycle with less than 1 % change on resilient modulus. Loading levels are selected as ( 10 20 ) percentage of one specimen. Instantaneous deformation is represented as difference between peak and writhe deformation. Total deformation was determined as difference between peak and end of one loaded- unloaded cycle as shows in figure 3. persona 36 load, displacement time plots for IDT test outputEquation 2Equation 3Where = Poissons ratio,v = the recoverable vertical, mm (in.)h = the recoverable horizontal deformation, mm (in.)MR = resilient modulus of elasticity, MPa (psi),h = recoverable horizontal deformation, mm (in.),I1,I2,I3,I4 never-ending values depends on gauge length as a ingredient of diameter specimen = instantaneous or total Poissons ratio,t = thickness of specimen, mm (in.),Pcyclic = Pmax P tinct = cyclic load applied to specimen, N(lb),Pmax = maximum applied load, N (lb) andPc ontact = contact load, N (lb)Indirect Tensile Fatigue TestsIThe specimen tested for fall apart under repeated load mode. The bear life was represented by number of cycle until failure during the test.Different fatigue criteria were developed within on IDT test. Number of cycles to complete failure (Nf) or 50 % reduction in resilient modulus of its initial value was used 7.8 defined it as when the permeant horizontal deformation ranges between 0.25-0.38 in. However 3 found dramatically change magnitude in total horizontal deformation was happened after a value of 0.1 in and select as failure criteria. 9 define it as the stop when horizontal deformation increase in faster rate more(prenominal) than constant rate. 10 select a value of 9 mm of total vertical deformation as failure criteria.11, introduced theoretical criteria based on energy ratio for both control stress and strain mode of loading. 2 introduced logit form used fracture energy as indicator for fatigue based on fati gue cracking.12 used viscoelastic continuum damage (VECD) model to predict fatigue life. A single-characteristic curve of an pave mixture and is salvage-lance of loading types (C1-S1 curve) model was used. A 50 % reduction in normalized pseudostiffness (C1) was selected as failure criteria.13 introduced new approach based on crack development. twain digital cameras were used to record development of cracks every minute. The failure criteria was selected as number loading cycle when rapid crack beginning.Two asphalt mixture, dense graded and stone mastic were tested based on AASHTP TP9-96. Control-stress mode of loading was used at 20 C with 10HZ frequency. Two digital cameras were used to record development of cracks every minute, as shows in the figure 3. Scion Image software was used to analysis results images. Both length and width of cracks was recorded. The failure criteria was selected as number loading cycle when rapid crack beginning. solve 413overlay tester (OT)The ove rlay test was introduced by 14 to induced resulted displacement from temperature change at layers below the overlay. The original OT was upgraded to test HMA laboratory mixes and battleground cores. The specimen size was modified to be obtained from superpave gyratory compactor samples (figure 6) and in full computer controlled system is used to control the test 15 .The test setup shows in figure 7 two steel blocks, one free to slides horizontally, while the other is fixed. The sliding member reflects the opening and closing of cracks or joint in pavement thus, will represent the two-stage fatigue process in pavement. The crack initiation, includes growing of micro-cracks and the crack propagation, represented by macro cracks on surface layer .16.Figure 5 Overlat test setup,15Figure 6 OT Sample preparation15The Trimmed specimen is glued with epoxy between two blocks. The sliding is applied cyclic triangular waveform direct tension on the specimen. It is controlled with maximum di splacement opening. The test could be conducted with loading rate ranges (1-600) mho/cycle, controlled opening displacement (0-0.08) and temperature between (32-77 F) 17.However, Texas Department of point (TxDOT) published standardized test procedure designation (Tex-248-F. It was specified that the specimen is loaded with 10 second cyclic controlled with 0.025 maximum displacement at 77+1F temperature.18Figure 7overlay setup-Tex-248-F test 19The crack defense is represented based on number of cycle correspond to 93% in maximum applied load in first cycle. (Hu et al. 2008 Sheng and rap 2016). However, 22 compare between different methods to analysis the data. The area under- the load-cycle response curve was used the result shows no improvement in variability. In addition, the rate of load decrease was studied, it was unsatisfactory. different load reduction percentage was tested as alternative for 93%. The 85% load reduction wait to be good.The test is recommend for performan ce measures for reflective cracks. 15 test field cores from different highways in taxas state. They suggest 300 cycle 93 % load reduction was selected as pass /failure criteria and 750 cycle was For the rich click layer. Also, New Jersey department of transportation (NJDOT) adopted OT test as performance measure for different mixes . The test conduct 10 second cyclic load controlled with 0.025 maximum displacement at either 59 or 77 F. The failure criteria of specimen selected to be 93 % or until minimum 1200. The detailed procedure published in designation NJDOT B-1023. The design Binder-Rich Intermediate Course(BRIC) require minimum of a 700 cycle at 77F as pass criteria. For high rap mixes it is require minimum 150,175 For PG64-22,PG76-22 respectively for surface course while intermediate course required minimum 100,125 cycle for PG64-22,PG76-22 respectively24.