Impact Fatigue Strength Research Articles

The effect of recycled date palm tree fibers on the impact fatigue and residual static strength of adhesively bonded joints

The role of natural fibers on the impact fatigue strength of bonded single lap joints (SLJs) has been experimentally investigated. The use of natural fiber offers several advantages, including the potential to recycle natural resources and the utilization of sustainable materials. Four types of natural date palm tree fibers (DPTFs) including Rachis, Petiole, Bunch, and Mesh were used to improve the impact fatigue life and the residual static strength of joints after enduring repetitive low energy impacts. The fibers were treated by 6 wt% of NaOH solution and cut manually to short size (0.5–2 mm) and were used by weight ratios of 2 and 5 %. The results show that the addition of DPTFs to the adhesive layer significantly improves the impact fatigue strength of the reinforced joints compared to neat adhesive SLJs. The joints reinforced by 5 wt% and 2 wt% of Mesh improved the impact fatigue life of the joints by 197 % and 87 %, respectively. The impact fatigue life of the joints modified by 5 wt% of fibers was more than the joints reinforced by 2 wt%. Fractography analysis also showed that DPTFs make the crack propagation more stable and increase the strength of the tested joints on different conditions.

On the combined effects of surface quality and pore size on the fatigue life of Al–7Si–3Cu–Mg alloy castings

This study has aimed to determine the effects of surface quality and pore size, obtained by different levels of hydrogen content of the liquid metal, on the fatigue behavior of an Al–7%Si–3%Cu–Mg casting alloy. Three surface conditions have been studied: as-cast rough, as-cast smooth, and standard machined and polished surface. The S–N curves have shown that surface roughness and hydrogen content individually impact fatigue strength. Surprisingly, the fatigue strength of machined and polished samples, which aligns with standard testing practices, is significantly reduced, compared to other conditions. Fatigue cracks have been observed to initiate at the pores just below the as-cast surface or on the machined surfaces. In all cases, pores have been observed to be surrounded by bifilms. Moreover, hydrogen content and roughness of the as-cast surface have been found to interact to determine the fatigue performance. These findings necessitate a re-evaluation of fatigue testing procedures for cast aluminum components.

Effect of microstructural heterogeneity on fatigue strength predicted by reinforcement machine learning

AbstractThe posterior statistical distributions of fatigue strength are determined using Bayesian inferential statistics and the Metropolis Monte Carlo method. This study explores how structural heterogeneity affects ultrahigh cycle fatigue strength in additive manufacturing. Monte Carlo methods and procedures may assist estimate fatigue strength posteriors and scatter. The acceptable probability in Metropolis Monte Carlo relies on the Markov chain's random microstructure state. In addition to commonly studied variables, the proportion of chemical composition was demonstrated to substantially impact fatigue strength if fatigue lifetime in crack propagation did not prevail due to high threshold internal notches. The study utilizes an algorithm typically used for quantum mechanics to solve the complicated multifactorial fatigue problem. The inputs and outputs are modified by fitting the microstructural heterogeneities into the Metropolis Monte Carlo algorithm. The main advantage here is applying a general‐purpose nonphenomenological model that can be applied to multiple influencing factors without high numerical penalty.

М. В. Тофик, А. Лёф, К. Миллуoрд, З. Гюнтер. Испытания и расчет ударной усталостной прочности клапанных сталей марок Flap-X и SS 716 = Tofique M. W., Löf A., Millward C., Günther Z. Testing and calculation of impact fatigue strength of Flap-X and SS 716 flapper valve steel grades / пер. с англ. М. А. Федоровой

During the operation of reciprocating compressors, the flapper valve opens and closes under fluid pressure and flow. As it closes, it strikes against the valve seat, generating stresses and noise. This cycle of loading produces bending and impact fatigue stresses in the reed. This load pattern is repeated billions of times during the service life of a compressor and it defines the service life and reliability. The goal of this study was to calculate the impact fatigue strength of the Flap-X and the SS 716 grades and, to provide the compressor manufacturers with the information they can use to specify a steel grade to be used in their compressors, for reliable service. Impact fatigue tests were conducted on a custom-built impact fatigue test rig that used air pulses to produce movement of the reed valves manufactured by a major European compressor manufacturer Nidec Global appliance GmbH, at a frequency of 315 Hz and pulse width of 2,2 milliseconds. The testing was conducted according to the staircase test method detailed in the International Standard SS-ISO 12107:2012. The impact fatigue strength of the Flap-X and SS 716 steel valves was calculated in terms of the impact velocity according to the modified staircase test method in the standard. The test results and their statistical analysis showed that the impact fatigue strength of the Flap-X grade was higher compared to the SS 716 grade. The calculation and testing of the impact fatigue strength of the flapper valve steel grades could help the compressor designers to select the optimum material for their compressor designs, to provide reliable service. The higher impact fatigue strength of the Flap-X grade, lower failure rate and longer impact fatigue life will allow the compressor manufacturers to design thinner valves, as Flap-X can sustain higher impact fatigue stresses reliably for longer time and, at the same time help reduce noise, as thinner valves produce less noise for a given pressure and frequency.

Testing and calculation of impact fatigue strength of Flap-X and SS 716 flapper valve steel grades

During the operation of reciprocating compressors, the flapper valve opens and closes under fluid pressure and flow. As it closes, it strikes against the valve seat, generating stresses and noise. This cycle of loading produces bending and impact fatigue stresses in the reed. This load pattern is repeated billions of times during the service life of a compressor and it defines the service life and reliability. The goal of this study was to calculate the impact fatigue strength of the Flap-X and the SS 716 grades and, to provide the compressor manufacturers with the information they can use to specify a steel grade to be used in their compressors, for reliable service. Impact fatigue tests were conducted on a custom-built impact fatigue test rig that used air pulses to produce movement of the reed valves manufactured by a major European compressor manufacturer Nidec Global appliance GmbH, at a frequency of 315 Hz and pulse width of 2.2 milliseconds. The testing was conducted according to the staircase test method detailed in the International Standard SS-ISO 12107:2012. The impact fatigue strength of the Flap-X and SS 716 steel valves was calculated in terms of the impact velocity according to the modified staircase test method in the standard. The test results and their statistical analysis showed that the impact fatigue strength of the Flap-X grade was higher compared to the SS 716 grade. The calculation and testing of the impact fatigue strength of the flapper valve steel grades could help the compressor designers to select the optimum material for their compressor designs, to provide reliable service. The higher impact fatigue strength of the Flap-X grade, lower failure rate and longer impact fatigue life will allow the compressor manufacturers to design thinner valves, as Flap-X can sustain higher impact fatigue stresses reliably for longer time and, at the same time help reduce noise, as thinner valves produce less noise for a given pressure and frequency.

Study on High-Frequency Fatigue Properties of PVD AlTiN Coating of Cutting Tool

Based on ultrasonic vibration-assisted mode, high-frequency impacting tests with diamond indenter at different amplitudes on AlTiN coating of cutting tool are carried out. The microstructure and morphology are obtained by scanning electron microscopy (SEM) and 3D profiler. The failure mechanism of coating under impact is analyzed. The high frequency fatigue property of the coating is analyzed. The results show that: lateral crack could be seen under impact test; the maximum tensile stress occurs close the edge of the contact zone of impact center; AlTiN coating is easy to emerge the fatigue damage under the high-frequency impact loading, and the adhesion strength of the coating and substrate interface affects the impact fatigue strength of cutting tool coating.

Effect of the electric current on the impact fatigue strength of CFRP composites

The present study intends to analyse and quantify the effect of the electric exposure on the impact fatigue strength of carbon/epoxy laminates subject to a DC electric current flowing through-thickness at the impact point. For this purpose several laminates were tested with different stacking sequences: [0]16 and [0i,90i]S, i=2, 3, 4, 5. The samples were submitted to a DC electric current of 1A, corresponding to an electric current density of 0.142(A/mm2). The unidirectional samples were exposed over 2h, 4h and 8h, and the cross-ply ones to 8h. The tests were carried out using a drop weight-testing machine and a 10mm diameter impactor. It was possible to conclude that the exposure to the electric current decreases the impact fatigue life, but the unidirectional laminates show to be much more sensible than the cross-ply ones as consequence of the higher pre-damages induced. Thicker samples are also minus sensible to the effects promoted by the electric current and, consequently, the impact fatigue life is less affected.

Effects of external patch configuration on repaired composite laminates subjected to multi-impacts

This work intends to study the impact performance of repaired composites by the overlap patch technique and, for this purpose, experimental tests were carried out on single and double-patch specimens. In order to evaluate the impact fatigue strength, both configurations were submitted to multi-impacts, until the full perforation occurs. It was possible to conclude that the double-patch geometry supports higher maximum loads, lower displacements and promotes higher elastic energies. Relatively to the impact energy of 6J, for example, the maximum load and the elastic energy is 97.1% and 51.2% higher, respectively, but the maximum displacement is about 50% lower than the values obtained with the single-patch geometry. Higher impact fatigue life was also observed, as consequence of its higher stiffness. The impact bending stiffness confirms the difference of stiffness between them, and shows to be a parameter able to monitor the damage progression.

Effect of distance between impact point and hole position on the impact fatigue strength of composite laminates

An impact fatigue study was performed to evaluate the effect of the distance between the impact point and the hole on the fatigue life of glass fibre/epoxy laminates. For this purpose, experimental tests were carried out in square plates and for the distances of 0, 5, 10 and 20mm, from the impact point. The results were compared with the ones obtained in plates without hole. It was possible to conclude that the fatigue life decreased, comparatively to the control samples, about 10.9%, 40%, 63.6% and 69.1% for the distances of 20mm, 10mm, 5mm and 0mm, respectively. Higher distances promote higher maximum loads and elastic restitution, but an opposite trend in terms of maximum displacement. For example, it was found for 20mm a maximum load around 5.54kN, a displacement of about 4.4mm and an elastic energy of 59.2%, while for 0mm these values were about 4.59kN, 5.7mm and 40.4%, respectively. In terms of multi-impacts, the damage severity is also very influenced by the distance. For small distances the damage progresses quickly, while three stages can be found for the control samples and for the distance of 20mm.

Investigation of Mechanical Properties and Impact Strength Depending on the Number of Fiber Layers in Glass Fiber- reinforced Polyester Matrix Composite Materials

Abstract In this study, glass fiber-reinforced composite materials were produced by hand lay-up with different number of layers of glass fiber, and tensile, flexural and impact fatigue strength of composite materials were investigated. The samples were also metallographically characterized. Depending on the number of fiber layers of samples mechanical properties and impact fatigue strength were examined. Due to the increase in the number of fiber layers, the mechanical properties of the samples were found to be improved.

Effect of the intermediate layer on the properties of a coating of 50KhFA steel produced by electrical resistance welding

The results of investigations of deposition of a coating of 50KhFA steel (0.46–0.54% C, 0.80–1.10% Cr, and 0.15% V) on shafts of steel 45 through an intermediate layer produced from a powder material and an amorphous strip brazing alloy are presented. It is shown that at the optimum combination of the parameters of electric resistance surfacing the bonding strength of the coating with the component is identical with that of the parent metal, the microhardness of the coating equals 6900–8100 MPa, the length of the zone of the thermomechanical effect does not exceed 0.35–0.6 mm, and the impact toughness and fatigue strength decrease by no more than 10% in comparison with steel 45 in the initial condition.

Tribological and impact fatigue behaviors of pure titanium treated by plasma Ni alloying

Ni modified layer is prepared on the surface of pure titanium by plasma surface alloying technique. Surface appearance, micro-structure morphology, composition distribution, phase structure and microhardness of Ni modified layer are analyzed. Tribological performance and fatigue behaviors of Ni modified layer of pure titanium are observed using Pin-on-disc tribometer and repeated impact test. The results indicate that the surface mean Ni concentration of Ni modified layer is nearly 18% which is composed of TiNi, Ti2Ni and Ti phase. The maximum surface microhardness of Ni modified layer is approximately 580 HV which is almost two-fold of the hardness of the substrate. The wear resistance of Ni modified layer is improved obviously. The wear mechanism of Ni modified layer shows slight abrasion wearing, while pure titanium is abrasion and adhesion wearing. Ni modified layer presents better impact fatigue strength.

601 鋼製平滑材及び切欠材の低サイクル衝撃疲労強度(GS-3 衝撃,疲労,疲労設計)

601 鋼製平滑材及び切欠材の低サイクル衝撃疲労強度(GS-3 衝撃,疲労,疲労設計)

浸炭材の低サイクル衝撃疲労特性に及ぼす表層炭素濃度と硫黄含有量の影響

Effect of surface carbon and sulfur on the low cycle impact fatigue properties in carburized steels were studied by using gear impact testing machine and strain gauge. The results obtained are summarized as follows: The low cycle impact fatigue strength was especially improved by decreasing content of the surface carbon and content of sulfur. It was found that increasing the crack initiation life by decreasing content of the surface carbon, and the initial crack length shorten. Furthermore, It was explained that the crack propagation speed decreased with decreasing sulfide. The method for estimating the crack initiation life from tensile properties of carburized layer is proposed by modifying Manson's Universal Slope Method.

Fatigue behavior of surface modified Ti-6Al-4V alloy by double glow discharge plasma alloying

The Mo–N, Mo–C, Mo–Cr modified layers on Ti-6Al-4V alloy were prepared using a double glow discharge plasma alloying technology. Repeated impact tests were performed to evaluate the fatigue behavior of the plasma modified Ti-6Al-4V alloys. Results show that the three surface modified layers exhibited a different depth distribution in microhardness and different failure mode in repeated impact tests. Among the three modified layers the Mo–N has the best matching of impact fatigue strength with hardness.

620 アクリル系接着剤の繰り返し衝撃負荷に対する引張強度

The impact fatigue strength of the acrylic adhesive under impact tensile loading was evaluated by adding impact cyclic loads to a tubular butt joint. The material of adherends was aluminium alloy A5052-H34,and the acrylic adhesive Hardloc M-372-20 was used. First, the combined loading test was performed in order to evaluate the static strength of the adhesive. As a result, the value of fracture stress under shear load is stronger than the value of fracture stress under tensile load. As the adhesive layer thickness become thick, the value of fracture stress become low. In the impact fatigue test, the thickness of the adhesive layer was 0.1mm. As a result, the maximum incidence stress becomes low, the number of impact loads to a fracture will increase. In cace the insident stress is 9MPa, the specimen did't fracture even if it was subjected to the impact loads 1 million times. It was considered that the fatigue limit is 9MPa.

高Ｃｒ白鋳鉄溶湯によるサーメット鋳ぐるみ材料の高温圧縮衝撃疲労特性

In order to improve the high-temperature wear resistance of white cast iron, a cermet powder layer mixed with Ni and/or Cr powder was inserted by molten 27 mass% Cr white cast iron. The microstructures of surface and vertical cross-section of the inserted layer were examined to investigate castability of the molten cast iron. High-temperature wear resistance of the inserted layer was examined by means of a high-temperature compressive impact fatigue test. The results obtained are as follows. (1) The inserted layer with 50 vol. % Ni powder or 25 vol. % Ni and 25 vol. % Cr powder shows satisfactory metallographic structure, though the inserted layer with 50 vol. % Cr powder includes some micro pores and voids. (2) The wear resistance decreases with increasing temperature for whole the inserted layers. The impact fatigue strength of the layer with 50 vol. % Cr powder is highest in whole the inserted layers at higher temperature side. (3) However, the inserted layer with 50 vol. % Cr powder shows many cracks connecting with the micro pores and voids after the impact fatigue test. Therefore, it is important to make an inserted layer without any micro pores and voids by using smaller sized cermet powder.

510 CFRP積層板の衝撃疲れ強さについて : 隅肉形状が層間剥離に及ぼす影響(疲労)

510 CFRP積層板の衝撃疲れ強さについて : 隅肉形状が層間剥離に及ぼす影響(疲労)

Effect of calcium on mechanical properties of recycled aluminiumcasting alloys

The effect of the addition of calcium on tensile properties, fracture toughness, and fatigue characteristics was investigated in JIS AC4C-T6, JIS AC2B-T6, and JIS AC4D–T6 aluminium casting alloys with various iron contents. The number of coarse platelike Al-Fe based intermetallic compounds increased with increasing iron content. The modification of the eutectic silicon morphology is successfully achieved by the addition of 40 ppm calcium. The addition of calcium makes the shape of the intermetallic compound, as well as the eutectic silicon, finer and round, and this seems to contribute to the improvement of mechanical properties, i.e. elongation, Charpy absorbed energy, both impact and conventional fatigue strengths, dynamic fracture toughness, and impact fatigue fracture toughness. Impact fatigue strength, especially in the high cycle region, increases with the addition of calcium. In the lower stress high cycle fatigue region, a higher fatigue strength with increasing iron content is observed owing to the deflected crack path along Al-Fe based intermetallic compounds.

Effect of calcium on mechanical properties of recycled aluminiumcasting alloys

The effect of the addition of calcium on tensile properties, fracture toughness, and fatigue characteristics was investigated in JIS AC4C-T6, JIS AC2B-T6, and JIS AC4D–T6 aluminium casting alloys with various iron contents. The number of coarse platelike Al-Fe based intermetallic compounds increased with increasing iron content. The modification of the eutectic silicon morphology is successfully achieved by the addition of 40 ppm calcium. The addition of calcium makes the shape of the intermetallic compound, as well as the eutectic silicon, finer and round, and this seems to contribute to the improvement of mechanical properties, i.e. elongation, Charpy absorbed energy, both impact and conventional fatigue strengths, dynamic fracture toughness, and impact fatigue fracture toughness. Impact fatigue strength, especially in the high cycle region, increases with the addition of calcium. In the lower stress high cycle fatigue region, a higher fatigue strength with increasing iron content is observed owing to the deflected crack path along Al-Fe based intermetallic compounds.