Servo-hydraulic Testing Machine Research Articles

MoS2/Ti Co-deposited Coatings and Their Fretting Wear Properties at Elevated Temperatures

Abstract Fretting wear refers to the damage phenomenon experienced by the mechanical components undergoing micro-amplitude relative slip at their contact region due to vibration. Titanium alloys find their extensive application in aerospace industry components such as splines and dovetail joints, where they experience fretting wear phenomenon. This research work investigates the effect of MoS2/Ti co-deposition coatings with varying Ti content, deposited on TC4 titanium alloy substrate using magnetron sputtering. Fretting wear tests were conducted at room temperature, 100 °C, and 200 °C, using a specially designed fretting test fixture with a ball-on-flat contact configuration, mounted on a servo-hydraulic fatigue testing machine. The results indicated that the coating becomes denser with an increase in the Ti content. The coating exhibited the highest hardness and better anti-fretting wear performance at room temperature. However, the effect of Ti content on the fretting wear behaviors changed at elevated temperatures. At the highest Ti content coating, excessive oxide particles were found at the worn surface at elevated temperatures, inducing an abrasive effect and localized cracks. However, coatings with moderate Ti content (9.62 at. %) effectively protected the substrate from significant wear at room temperature and maintained a low coefficient of friction at high temperatures without failure.

Biomechanical Performance of 4-Leg Sustained Dynamic Compression Staples in First Tarsometatarsal Arthrodesis.

This study investigates the biomechanical efficacy of new 4-leg Sustained Dynamic Compression (SDC) NiTiNOL staples, hypothesized to offer superior stability and resilience to loading before fusion completion, compared with conventional hardware. Twenty sawbones left full foot models were divided into 4 treatment groups: (1) 4-leg Inline Staple, (2) 4-leg Inline Staple + 2-leg Staple, (3) 4-leg Inline Staple + Screw, and (4) Plate + Screw. An osteotomy was performed to simulate a Lapidus procedure, and the respective fixation methods were applied. Mechanical testing was conducted using a servo-hydraulic testing machine to evaluate constructs' load, contact force, contact area, and plantar gap. The 4-leg Inline Staple + Screw group demonstrated significantly increased joint contact force, joint contact area, and decreased plantar gap compared with the Plate + Screw group, both before and after cyclic testing. All SDC-containing constructs exhibited post-cyclic joint contact areas that were 2.36×, 3.87×, and 5.49× greater than the post-cyclic plate + screw group. Most notably, the 4-leg Inline Staple + Screw group maintained a plantar gap of less than 3 mm throughout the testing, unlike other groups. The 4-leg Inline SDC Staple, particularly when combined with a static screw, demonstrated biomechanical superiority over traditional plate and screw constructs in Lapidus procedures. These findings suggest a promising avenue for enhanced post-operative stability, which could translate into quicker patient recovery, improved fusion rates, and potentially lower non-union rates. Further clinical trials are warranted to validate these biomechanical advantages in patient outcomes. Therapeutic, Level V: Bench Testing.

Medial open wedge osteotomy yields comparable stability to lateral open wedge procedure on the distal femur.

Supracondylar osteotomies are a frequently and successfully used technique in the treatment of coronal plane deformities and unicompartmental osteoarthritis of the knee. While lateral open wedge techniques are common for valgus deformities, the data about medial open wedge techniques for varus deformities is sparse. The aim of this study was to compare the biomechanical properties of medial and lateral open wedge osteotomies using a locking Tomofix® plate (DePuy Synthes, Oberdorf, Switzerland). Our hypothesis was that there would be no difference regarding biomechanical outcome parameters between these two groups. Medial and lateral open wedge osteotomies were performed in composite bone model as routine. Each experimental group contained 6 constructs. Standardized osteotomy gaps of ten millimeters were performed and Tomofix® plates were fixed to third generation composite bones. The constructs were subsequently mounted into a servohydraulic testing machine. Axial and torsional loadings were applied as described in previous experimental studies. All specimens were subject to a load to failure mode with the mechanism of failure being noted. Both experimental groups showed comparable biomechanical properties under axial and torsional loadings. Mean high force axial stiffness was 3772 N/mm for lateral and 4185 N/mm for the medial construct. Significant differences were noted for torsional stiffness under low- (0 N) and mid-force (150 N) loadings (P = 0.002; P = 0.009), favoring the medial open wedge constructs. Medial open wedge osteotomy yields comparable biomechanical stability to the lateral open wedge procedure on the distal femur in a composite bone model.

Titanium Cable Cerclage Increases the Load to Failure in Plate Osteosynthesis for Distal Femoral Fractures.

Background and Objectives: The reduction of two-part oblique or spiral fractures of the distal femur using steel wire cerclage prior to plate osteosynthesis is a proven procedure. In addition to being useful in fracture reduction, wire cerclage was also shown to increase the stability of osteosynthesis. Nevertheless, metal corrosion and the allergenic potency of steel remain problematic disadvantages of this method. A biomechanical study was carried out to evaluate titanium cable cerclage as an alternative supplement for plate osteosynthesis of a distal femoral two-part fracture. Materials and Methods: An unstable AO/OTA 32-A2.3 fracture was created in eleven pairs of nonosteoporotic human cadaver femora. All the samples were treated with polyaxial angular stable plate osteosynthesis. One femur from each pair was randomly selected for an additional fracture fixation with multifilament titanium cable cerclage. Stepwise cyclic axial loading was applied in a load-to-failure mode using a servohydraulic testing machine. Results: All specimens (mean age: 80 years; range: 57-91 years) withstood a cycling force of at least 1800 N. With a mean load of 2982 N (95% CI: 2629-3335 N), the pressure forces resulting in osteosynthesis failure were significantly higher in specimens with an additional titanium cerclage (Group 1) than in samples that were solely treated with plate osteosynthesis (Group 2) at 2545 N (95% CI: 2257-2834 N) (p = 0.024). In both groups, cutting out the distal screws at the condyle region, resulting in shearing of the distal fragment proximal to the fracture line, was the most frequent cause of construct failure. Among the specimens assigned to Group 1, 36% exhibited a specific fracture pattern, namely, a fracture of the dorsal buttress above the cerclage. Analysis of axial stiffness (p = 0.286) and irreversible deformity of the specimens revealed no differences between the groups (p = 0.374). Conclusion: Titanium cable cerclage application, as a supplement to an angular stable plate, resulted in an increased load to failure. In terms of stability, the use of this adjunct for fracture fixation of supracondylar two-part oblique femoral fractures might, therefore, be an option, especially in patients who are sensitive to nickel.

THE EFFECT OF CEMENTED FEMORAL COMPONENT DESIGN AND PROPHYLACTIC WIRE PLACEMENT AGAINST EARLY PERIPROSTHETIC FEMORAL FRACTURE IN PRIMARY TOTAL HIP ARTHROPLASTY: A BIOMECHANICAL STUDY

Previous studies have highlighted differences in the risk of periprosthetic fracture between tapered slip (TS) and composite beam (CB) stems. This biomechanical study explored periprosthetic fractures around these stems and the effect of adding a 16-gauge calcar or diaphyseal wire to TS stems on their resistance to torque.A power analysis determined a sample size of 7 specimens per group, assuming a standard deviation of 14.8 Nm in peak torque, to provide 90% power to detect a difference of at least 30 Nm between groups. Twenty-one TS stems (eight alone, six with calcar wiring, seven with diaphyseal wiring placed 2 cm distal to the lesser trochanter) and seven CB stems were cemented into standard Sawbones. A servo-hydraulic test machine applied a 1000 N load with a 1-degree rotation per second until failure. The peak torque at failure was measured, and the fracture location recorded. Comparisons were performed using two-sample t-tests.CB stems exhibited a significantly higher peak torque at failure (205.3 Nm) than TS stems (159.5 Nm, p=0.020). Calcar-wire-TS (148.2 Nm, p=0.036) and diaphyseal-wire-TS (164.9 Nm, p=0.036) were both weaker than CB stems. Wired-TS stems showed no significant difference from non-wired-TS stems. Additionally, the study could not conclude that calcar wiring is stronger than diaphyseal wiring. All TS fractures occurred at the mid-stem, simulating a B-type fracture, while the addition of the diaphyseal wire shifted the fracture location more distally in four of seven stems (p=0.0699).This biomechanical study supports the clinical evidence that CB stems have stronger resistance to torque than TS stems and may explain lower risk of periprosthetic fracture. The addition of calcar or diaphyseal wires to TS stems resulted in no significant changes in peak torque to fracture. In patients at high risk of periprosthetic fracture, CB cemented stems should be considered.

Anterior variable angle locking neutralisation plate superiority over traditional tension band wiring for treating transverse patella fractures.

This paper investigates the biomechanical benefits of using hybrid constructs that combine cannulated screws with tension band wiring (TBW) cerclage compared to cannulated screws with anterior Variable Angle locking neutralisation plates (VA LNP). These enhancements can bear heavier loads and maintain the repaired patella's integrity, in contrast to traditional methods. Eighteen fresh-frozen human cadaver patellae were carefully fractured transversely at their midpoints using a saw. They were then divided into two groups of nine for subsequent utilisation. Fixation methods included Cannulated Screw Fixation added with either TBW or VA LNP Fixation Technique. Cyclic loading simulations (500 cycles) were conducted to mimic knee motion, tracking fracture displacement with Optotrak. After that, the constructs were secured over a servo-hydraulic testing machine to determine the load-to-failure on axial mode. The average fracture displacement for the anterior neutralisation plate group was 0.09 ± 0.12 mm, compared to 0.77 ± 0.54 mm for the tension band wiring with cannulated screw group after 500 cyclic loading. This result is statistically significant (p = 0.004). The anterior neutralisation plate group exhibited a mean load-to-failure of 1359 21.53 N, whereas the tension band wiring group showed 780.1 ± 22.62 N, resulting in a significant difference between the groups (p = 0.007). This research highlights the superior biomechanical advantage of VA LNP over TBW for treating simple transverse patella fractures with two cannulated screws. It also highlights how the TBW is still a valuable option considering the load-to-failure limit. Not Applicable.

Modelling of Multi-Bolted Systems at the Pretension Stage – Part 1: Mechanical Characteristics of the Contact between the Joined Elements

The subject of the paper is the modelling of multi-bolted connections that are at the pretensioning stage. Taking a systematic approach to the modelling issue, the connection was treated as a composite of four subsystems: a bolt set, a pair of joined elements and a contact layer between them. The first part of the paper describes experimental studies to determine the contact stiffness of a pair of elements separated from an exemplary asymmetric multi-bolted connection. The normal loading and unloading direction of the contact joint was considered. The tests were performed with the use of an INSTRON 8850 servo-hydraulic testing machine equipped with an extensometer. A normal stiffness characteristic in the form of an exponential function was proposed for the tested contact joint. It will be applied in the second part of the paper, in which finite element modelling of the multi-bolted connection will be presented.

The Effect of Implantoplasty on the Fatigue Behavior and Corrosion Resistance in Titanium Dental Implants.

Implantoplasty is a technique increasingly used to remove the biofilm that causes peri-implantitis on dental implants. This technique of mechanization of the titanium surface makes it possible to eliminate bacterial colonies, but it can generate variations in the properties of the implant. These variations, especially those in fatigue resistance and electrochemical corrosion behavior, have not been studied much. In this work, fatigue tests were performed on 60 dental implants without implantoplasty, namely 30 in air and 30 in Hank's solution at 37 °C, and 60 with implatoplasty, namely 30 in air and 30 in Hank's solution at 37 °C, using triaxial tension-compression and torsion stresses simulating human chewing. Mechanical tests were performed with a Bionix servo-hydraulic testing machine and fracture surfaces were studied by scanning electron microcopyElectrochemical corrosion tests were performed on 20 dental implants to determine the corrosion potentials and corrosion intensity for control implants and implantoplasty implants. Studies of titanium ion release to the physiological medium were carried out for each type of dental implants by Inductively Coupled-Plasma Mass Spectrometry at different immersion times at 37 °C. The results show a loss of fatigue caused by the implantoplasty of 30%, observing that the nucleation points of the cracks are in the areas of high deformation in the areas of the implant neck where the mechanization produced in the treatment of the implantoplasty causes an exaltation of fatigue cracks. It has been observed that tests performed in Hank's solution reduce the fatigue life due to the incorporation of hydrogen in the titanium causing the formation of hydrides that embrittle the dental implant. Likewise, the implantoplasty causes a reduction of the corrosion resistance with some pitting on the machined surface. Ion release analyses are slightly higher in the implantoplasted samples but do not show statistically significant differences. It has been observed that the physiological environment reduces the fatigue life of the implants due to the penetration of hydrogen into the titanium forming titanium hydrides which embrittle the implant. These results should be taken into account by clinicians to determine the convenience of performing a treatment such as implantoplasty that reduces the mechanical behavior and increases the chemical degradation of the titanium dental implant.

Characterization of Magnetorheological Impact Foams in Compression.

This study focuses on the development and compressive characteristics of magnetorheological elastomeric foam (MREF) as an adaptive cushioning material designed to protect payloads from a broader spectrum of impact loads. The MREF exhibits softness and flexibility under light compressive loads and low strains, yet it becomes rigid in response to higher impact loads and elevated strains. The synthesis of MREF involved suspending micron-sized carbonyl Fe particles in an uncured silicone elastomeric foam. A catalyzed addition crosslinking reaction, facilitated by platinum compounds, was employed to create the rapidly setting silicone foam at room temperature, simplifying the synthesis process. Isotropic MREF samples with varying Fe particle volume fractions (0%, 2.5%, 5%, 7.5%, and 10%) were prepared to assess the effect of particle concentrations. Quasi-static and dynamic compressive stress tests on the MREF samples placed between two multipole flexible strip magnets were conducted using an Instron servo-hydraulic test machine. The tests provided measurements of magnetic field-sensitive compressive properties, including compression stress, energy absorption capability, complex modulus, and equivalent viscous damping. Furthermore, the experimental investigation also explored the influence of magnet placement directions (0° and 90°) on the compressive properties of the MREFs.

An innovative approach to planar mixed-mode fatigue crack growth study

Determining fatigue crack growth parameters under mixed-mode loading is crucial for damage tolerance design, particularly in assessing a component's residual life with defects to prevent disasters. This study introduces a novel methodology for determining fatigue crack growth rate. A digital microscope is utilized to track the fatigue crack tip with respect to local coordinate systems established on the specimen surface. A grid is drawn and subdivided into units with proposed nomenclature. Compact Tension and Shear (CTS) specimens, extracted from AA-7085 plates, undergo fatigue loading in a servo-hydraulic universal testing machine. A fixture proposed by Richard et al. induces planar mixed-mode loading cases in the specimen. During experiments, the digital microscope tracks the crack tip using grid unit corners as local origins. The local coordinates of the crack tip are transformed into the crack tip coordinates with respect to the pre-crack tip. Crack evolution data are used to determine the fatigue crack growth rate by analyzing tangents of a three-parameter fitted curve. The equivalent SIF ranges are computed at different crack lengths in an XFEM script written in Ansys. The modified Paris parameters are found and experimentally observed crack deflection angles are compared with the Maximum Tangential stress, Strain energy density, and Richard’s criterion.

Evaluation and Performance Analysis of Liquefied Petroleum Gas Cylinders

This paper presents the experimental results of the tensile, bending, hardness, hydrostatic testing, and microstructural properties of liquefied petroleum gas cylinders from local sources. The burst pressure and fracture sites were also investigated. In addition, know how LPG cylinders are compliant with ISO 4706 requirements as per standard to get approval and acceptance. The tests were performed on three samples (C1, C2, and C3), and all the tests were according to the specification. Tensile testing was carried out at room temperature (23C°) as per ISO 6892-2016. Tensile test specimens with a gauge length of 50 mm were prepared from the sidewall of cylinders. The equipment used is built up around a 250 KN maximum capacity of (Instron Servo-Hydraulic Testing Machine Model 1332). At the same time, micro-hardness testing was carried out as per ASTM A384. Diamond indenter (pyramid) with a face angle of 136° was used. During testing (1kg) load was applied on the sample with a dwell time of 15 seconds. As for bending tests were carried out in accordance with ISO 7438 for all cylinders to evaluate their welding qualities. The results of microstructural characterization show that the carbon content for all samples averaged ~ 0.067 wt.% and manganese ~ 0.46 wt.% and the microstructure was largely ferritic. The tensile strength of the parent metal showed that LPG gas cylinders recorded high tensile strength of ~ 418 MPa on average, yield strength of ~ 291 MPa on average, a % elongation 26.6 (for parent metal), the tensile strength of ~ 449 MPa as average, yield strength of ~ 314 MPa as average, % elongation 32 (for weld metal) and hardness of ~ 143 (kg/mm2) as average by Vickers scale. Moreover, in the hydrostatic pressure test, the computer controlled electro-hydraulic servo pressure test machine was used. The results of the hydrostatic pressure test were as follows, pressure burst (BP) 103 bar, nominal hoop stress 528 MPa, volumetric expansion 25%, hydrostatic extend ratio 3.9%, sites of failure exist out of welding, and finally no fragmentation observed regarding to fracture types. All samples tested exhibited high resilience to crack propagation which showed ductile fracture after burst and tensile tests.

Tensile properties of 3D printed INCONEL 718 cellular specimens

The aim of the presented research by the authors was to compare the behaviour of four types of cellular structures under quasi-static tensile stress, while two samples were formed by mono-structures Gyroid 10 % and Diamond 10 %, and the other two types were bi-structures, which were created by combining two single structures (Gyroid 5 % + Gyroid 5 %) and (Gyroid 5 % + Diamond 5 %). The samples were made of Inconel 718 by Direct Metal Laser Sintering technology on an EOS EOSINT M270 machine, and they were heat treated according to AMS 5664 procedure. Tensile tests were performed on an Instron 8802 servo-hydraulic testing machine with a maximum capacity of 250 kN at ambient temperature. The results showed that the maximum load corresponded to the diamond (D) cellular structure (approximately 48 kN), while the minimum load was observed for the gyroid-gyroid (GG) structure (approximately 32 kN).

Calibration of tensile tests in drop-weight impact machine and implementation in simulation of Charpy impact tests

Material modeling and simulation of deformation under very high loading rate in the dynamic/impact range are applied in crash resistance, ballistic impact analysis, and other time-sensitive phenomena. Servo-hydraulic UTM tensile test data from medium to higher strain rate > (500 s-1) is reliable but expensive and complexity in experiment. Tensile testing at very high strain rate (upto 1500 s-1) can be done in a drop-weight impact testing machine with a special fixture and the impactor velocity controls strain rate. In INSTRON CEAST 9350 drop weight impact testing machine tensile tests are conducted at four velocities for amour steel. A 5MHz data acquisition system (DAQ) measures strain in specimen gauge length mounted with high-elongation strain gauge. An extensometer is used to calibrate the strain gauge in a quasi-static 10-4 s-1 tensile test. Tensile test data from impact machine is compared with stress-strain data from the INSTRON servo-hydraulic testing machine with DIC for different strain rates. Close matching in elastic modulus, yield strength, tensile strength, and elongation are observed. Material parameters of a strain rate-dependent material model (modified J-C model) are extracted from drop weight impact testing machine data clubbed with other tensile test data, used in FE simulation of very high strain rate tensile tests, and validated with experimental results. Later, the same material model and material parameters are used to simulate Charpy impact tests at various velocities and compared with experimental results which also show close matching.

Compression behavior of diamond cellular structure made of Inconel 718

The article aims to investigate compression behaviour of Diamond cellular structure at different cross-head speeds. The samples were made of Inconel 718 alloy by DMLS (Direct Metal Laser Sintering) technology and heat treated according to AMS 5664 procedure. The compression tests were performed according to ASTM E9 international standard at ambient temperature employing a servohydraulic testing machine Instron 8802 with a maximum capacity of 250 kN at three different cross-head speeds v = 1; 10 and 100 mm/min. The results showed that testing speed does not affect significantly the maximum force results, and that the Diamond structure of 20 % volume fraction exceeded the upper load limit of the testing machine, i.e. 250 kN, for all three testing speeds.

Stabilization of Traumatic Iliosacral Instability Using Innovative Implants: A Biomechanical Comparison.

(1) Background: Demographic changes over the past decade have had a significant impact on pelvic ring fractures. They have increased dramatically in the orthogeriatric population. Surgeons are faced with implant fixation issues in the treatment of these fragility fractures. This study compares two innovative implants for stabilizing the iliosacral joint in a biomechanical setting. (2) Methods: An iliosacral screw with a preassembled plate allowing the placement of an additional short, angular stable screw in the ilium and a triangular fixation system consisting of a fenestrated ilium screw and an iliosacral screw quasi-statically inserted through the "fenestra" were instrumented in osteoporotic artificial bone models with a simulated Denis zone 1 fracture. Biomechanical testing was performed on a servo-hydraulic testing machine using increasing, synchronous axial and torsional sinusoidal cyclic loading to failure. (3) Results: The SI-Plate and TriFix showed comparable stiffness values. The values for fracture gap angle and screw tip cutout were significantly lower for the TriFix compared to the SI-Plate. In addition, the number of cycles to failure was significantly higher for the TriFix. (4) Conclusions: Implant anchorage and primary stability can be improved in iliosacral instability using the triangular stabilization system.

Investigation of heat transfer performance of double-walled pipes of heat exchanger for power plant applications

Heat transfer between contacting surfaces, is a key factor affecting the thermal performance of heat exchangers in power plants and other applications. Double-walled pipes, used in the heat exchangers, can significantly improve the safety factor of the system. In this research work, the thermal contact conductions (TCC) at the interfaces of double-walled stainless steel 316 L pipes under various contact pressures were investigated. These pipes were manufactured with the shrink-fitting method using servo-hydraulic universal testing machine. A numerical model, verified by X-ray diffraction analysis, was developed to investigate the contact pressure variation at the interfaces according to loading conditions. The contact pressure between the inner and outer walls was controlled in the range of 22.78 MPa to 25.70 MPa, by varying the tensile loading conditions. A phase-sensitive transient thermal method was developed to measure the thermal conductivity (TC) and TCC of double-walled pipes. TC was observed to be in the range of 15.13 W/mK to 15.84W/mK while TCC at the interface was observed to increase sharply with the contact pressure, reaching 17 × 103W/m2K under 25.70 MPa contact pressure.

Investigations on compression behavior of fused filament fabricated hybrid biomimetic structures

The objective of this study is to design a biomimetic hybrid structure inspired by nacre, and conch shells and compare how the compressive characteristics change when key geometric design parameters are varied. Nacre, also known as mother of pearl, has a host of traits, suitable for survival, like its stiffness and strength. Conch, which is a common name for a number of sea snails, possesses a unique cross-lamellar structure which has a tough outer layer to resist penetration from the sharp-toothed attacks of predators, and a nacreous inner layer which can dissipate energy. A novel nacre–conch–nacre inspired sandwich core structure is designed and fabricated with fuse filament fabrication using acrylonitrile styrene acrylate filament according to the ASTM C365 standard for the flatwise compression test of sandwich core structures. Three key design parameters, namely the wall thickness, the thickness between two nacre walls, and the angle of conch were selected and varied to form nine different iterations of this design. An Abaqus finite element analysis was validated by experimental testing using an Instron 8801 servo-hydraulic universal testing machine. The results showed that conch-inspired structures’ compression properties depend on wall thickness and angle. The sample with 2 mm wall thickness and 45° conch angle had the highest compressive strength of 3.62 MPa, while the sample with 1 mm wall thickness and 50° conch angle had the lowest at 2.09 MPa. These findings suggest this structure could be used in lightweight armor, car, and aerospace parts.

High strain rate mechanical behaviour of uniform and hybrid metallic TPMS cellular structures

Four different geometries of uniform triply periodic minimal surface (TPMS) cellular structures (Diamond, Gyroid, IWP, and Primitive) and a hybrid Gyroid–Diamond TPMS structure were fabricated and experimentally tested under different compressive strain rates ranging from quasi-static (at 0.005 s−1) to very high strain rates (at 11,000 s−1). Three different testing apparatuses were used: a universal servo-hydraulic testing machine, a direct impact Hopkinson bar (DIHB), and a powder gun. Limited strain rate hardening was observed at quasi-static, low- and intermediate-dynamic deformation, while the shock deformation mode showed significant strain rate hardening of all tested structures. The computational models were developed and validated with the experimental results and then used to predict the TPMS structure’s behaviour even at higher strain rates (up to 35,000 s−1), not attainable by used experimental devices. The Diamond and IWP structures exhibited up to five times higher (an increase from 6.9 to 40.8 J/g) specific energy absorption (SEA) during very high strain rate loading than during the quasi-static and lower dynamic testing. The tests of hybrid samples showed that the sample orientation significantly affects the mechanical high strain rate response, which can be either progressive (less stiff structure at sample impact end) or regressive (stiffer structure at sample impact end).

Tensile Strength of Abaca Fiber Reinforced Polymer Composite Fabricated by Press Method: Effect of Fiber Content and Fiber Orientation

The paper reported the study on the tensile strength of polymer composite reinforced with abaca fiber and polyester matrix. The effect of fiber weight content and fiber orientation on the tensile strength of the abaca composite were investigated in the study. The abaca composite panel was fabricated using press method with 3 levels of the fiber weight content (20%, 30% and 40%) and 3 levels of fiber orientation (00, 450 and 900). The tensile specimen was prepared according to ASTM D3039 standard. The tensile test was conducted using MTS Landmark servo hydraulic testing machine with a tensile speed of 2 mm/min. The result of the experiment showed that both of fiber weight content and fiber orientation gave significant effect on the tensile strength of the abaca composite. The highest tensile strength was 61.9 MPa, produced by the abaca composite panel with fiber weight content 30% and fiber orientation 00. According to the standard, the tensile strength has fulfilled the requirements as a non-structural material.

Different post-processing methods to improve fatigue properties of additively built Ti-6Al-4V alloy

The fatigue performance of the Ti-6Al-4V alloy built using the laser-powder bed fusion additive method was investigated in this study. Post-process methods such as heat-treatment (HT), machining (M), hot isostatic pressing (HIP), and different combinations thereof were explored to enhance the mechanical as well as the fatigue properties. Load-controlled uniaxial high-cycle fatigue tests were performed using a servo-hydraulic fatigue testing machine at room temperature. The machining (M) of the as-built samples increased its fatigue properties, irrespective of the HT and HIP conditions. The tensile strength decreased considerably after the HT, HIP, and HT + HIP treatment but with increasing ductility. On the other hand, the fatigue strength improved with the HT condition and was further enhanced by five times after the HT + HIP + M condition, in comparison to that of the as-built alloy. The X-ray computed tomography analysis revealed a drastic reduction in the percentage of internal defects after the HIP treatment, from 0.31% to 0.01%. The fractographic analysis revealed that the cracks were mostly initiated from the defects in the as-built and HT conditions while in the HIP condition, it was from the facets in the α-phase. The reasons for the improvement in fatigue properties after the different post-process treatments were attributed to the induced-microstructural changes, surface finish quality, relaxed or compressive residual stresses, and most importantly, the reduced fraction of the crack-initiating process-inherent defects, which are explained and argued in this article.