Significant Loss Of Strength Research Articles

Relationship between the microstructure and mechanical properties of an equiatomic AlCoCrFeNi high-entropy alloy fabricated by selective electron beam melting

Because of their superior properties, high-entropy alloys (HEAs) are considered promising novel structural materials that can substitute conventional alloys. From the viewpoint of future applications, it is important to explore methods for producing complex shaped products with HEAs. In this study, selective electron beam melting (SEBM) was employed for fabricating equiatomic AlCoCrFeNi HEA specimens, and their microstructures and mechanical properties were evaluated by comparing them with those of a conventionally cast specimen. Both cast and SEBM specimens dominantly consisted of a nano-lamellar mixture of disordered body-centered-cubic (BCC) and B2 (ordered BCC) phases. The face-centered cubic (FCC) phase was also precipitated at the grain boundaries of the B2/BCC mixture phases on the SEBM specimens. The fraction of the FCC phase at the bottom part of the SEBM specimen was higher than that at the top part. The preheating procedure—a process unique to SEBM—is responsible for the precipitation of the FCC phase, because of the long-term exposure at sufficiently high temperatures. As a result, the hardness of the SEBM specimens gradually decreased as we approached the bottom part of the specimens due to the increased fraction of the FCC phase, which had lower hardness than the B2/BCC phases. Further, the SEBM specimen exhibited much higher plastic deformability than the cast specimen, without significant loss of strength.

Shoulder Strength Changes One Year After Axillary Lymph Node Dissection or Sentinel Lymph Node Biopsy in Patients With Breast Cancer

ObjectivesTo assess the changes in shoulder strength of patients with breast cancer during the first year after surgery; and to compare the effect of sentinel lymph node biopsy (SLNB) and axillary lymph node dissection (ALND) on shoulder strength. DesignProspective longitudinal observational study from presurgery to 1 year after. SettingTertiary hospital. ParticipantsOf 129 consecutive patients examined for eligibility, a sample of women (N=112) with breast cancer were included (44 underwent ALND, and 68 underwent SLNB). InterventionsNot applicable. Main Outcomes MeasuresDifference between the affected and unaffected arm in strength of shoulder external rotators, internal rotators, abductors, and serratus anterior, measured by dynamometry. Evaluations were performed prior to surgery and at 1, 6, and 12 months after surgery. ResultsAfter breast cancer ALND surgery, strength decreased significantly at the first month for internal rotators, without having recovered presurgery values after 1 year of follow-up, with a mean difference of 2.26kg (P=.011). There was no significant loss of strength for patients treated with SLNB. The loss of shoulder range of motion was only significant the first month for the ALND group. The factors identified as associated with strength loss in the general estimating equation models were the ALND surgery and having received physical/occupational therapy during follow-up. ConclusionsOne year after breast cancer surgery, patients treated with ALND had not recovered their previous shoulder internal rotators strength, whereas those who underwent SLNB presented no significant loss of strength. This provides important information for designing rehabilitation programs targeted specifically at the affected muscle group after nodal surgical approach.

Using of Wastewater Dry and Wet Sludge In Concrete Mix

wastewater treatment plants in Egypt, since the amount of sludge produced every year in Egypt are about “4 Million ton “, this amount of sludge is considered a big/dangerous problem which facing Egypt today. Thus, all over the world the researchers are trying to explore a new and suitable way to solve the sludge huge amount which produced from the WWTPs. One track of these solutions is to use sewage sludge in Construction field” concrete mixtures and in manufacturing interlock brick samples’’, evaluated the reuse of sewage sludge from urban wastewater treatment plants in a mixture with cement and to develop new construction materials. According to results findings, no significant strength loss was observed when using the dry or wet sludge with different percentages from the cement weight, in which the strength loss was increased to 63.7% after 7-days and 61.6% after 28-day for dry and for wet 73.4% after 7-days and 68.5% after 28-days when 20% of wet and dry sludge pellets by cement weight was added to concrete mixture. The results showed that the wet sludge retarded the strength development and has more adverse effect on compressive strength than the other dry sludge for the same percentage as the average strength loss after 28-days for wet percentages approximate about 13.76% and for dry sludge approximate about 7.73%. Finally the study concluded that the dry and wet sludge can be used in as an additive to concrete mixtures till 15% form cement weight as one of the available disposal options for Egypt sludge. The study recommended that more researches are needed to evaluate the durability of sludge concrete and the behavior of reinforced sludge concrete.

Interactions of hydrogen with the iron and iron carbide interfaces: a ReaxFF molecular dynamics study.

Hydrogen embrittlement (HE) is a well-known material phenomenon that causes significant loss in the mechanical strength of structural iron and often leads to catastrophic failures. In order to provide a detailed atomistic description of HE we have used a reactive bond order potential to adequately describe the diffusion of hydrogen as well as its chemical interaction with other hydrogen atoms, defects, and the host metal. The currently published ReaxFF force field for Fe/C/H systems was originally developed to describe Fischer-Tropsch (FT) catalysis [C. Zou, A. C. T. van Duin and D. C. Sorescu, Top. Catal., 2012, 55, 391-401], and especially had been trained for surface formation energies, binding energies of small hydrocarbon radicals on different surfaces of iron and the barrier heights of surface reactions. We merged this force field with the latest ReaxFF carbon parameters [S. Goverapet Srinivasan, A. C. T. van Duin and P. Ganesh, J. Phys. Chem. A, 2015, 119, 1089-5639] and used the same training data set to refit the Fe/C interaction parameters. The present work is focused on evaluating the applicability of this reactive force field to describe material characteristics and study the role of defects and impurities in the bulk and at the precipitator interfaces. We study the interactions of hydrogen with pure and defective α-iron (ferrite), Fe3C (cementite), and ferrite-cementite interfaces with a vacancy cluster. We also investigate the growth of nanovoids in α-iron using a grand canonical Monte Carlo (GCMC) scheme. The calculated hydrogen diffusion coefficients for both ferrite and cementite phases predict a decrease in the work of separation with increasing hydrogen concentration at the ferrite-cementite interface, suggesting a hydrogen-induced decohesion behavior. Hydrogen accumulation at the interface was observed during molecular dynamics (MD) simulations, which is consistent with experimental findings. These results demonstrate the ability of the ReaxFF potential to elucidate various aspects of hydrogen embrittlement in α-iron and hydrogen interactions at a more complex metal/metal carbide interface.

Investigation of Limit States Specified for Reinforced Concrete Column Members in TEC–2007

In this study, the deformation based limit states stipulated for reinforced concrete members in the Turkish Earthquake Code (TEC) were experimentally investigated. Thus four RC cantilever columns which have low concrete compressive strengths and have not adequate confinement, were subjected to constant axial load and cyclic lateral load history. In the study, firstly, the strain values representing the damage limits were converted to top of the column lateral displacements by using fundamentals of structural mechanics. Subsequently the column damages corresponding to the displacement demands were observed, hence limit states were evaluated. After conducting all column tests, it was noted that no column damage was observed for the immediate occupancy (IO) performance level defined in the code. For the life safety (LS) and collapse prevention (CP) performance levels, though somewhat residual deformations occurred on the critical regions, the column members can pretty much sustain their lateral load capacities. It was also observed for all columns that significant damages and strength losses occurred beyond the collapse prevention level. The results of experimental study indicate that the evaluation procedure in the TEC is still in good relationship with the limit states even if the columns have not adequate compressive strength and confinement.

EFFECT OF CURING METHODS ON STRENGTH PROPERTIES OF SELF COMPACTING CONCRETE INCORPORATED WITH METAKAOLIN AS SUPPLEMENTARY CEMENTING MATERIAL

The manufacturing of Self Compacting Concrete needs both chemical and mineral admixtures. The method of curing plays a vital role on strength and setting characteristics of SCC. Hence, this paper presents the results of an investigation dealing with the effects of curing methods on the compressive strength of SCC incorporating Metakaolin as supplementary cementing material. The SCC was prepared using 53grade OPC with and without Metakaolin as SCM. The Grades of concretes made were Standard concretes of M50 and High strength concretes of M80 grades. The compressive strength of the concrete was determined at 7 and 28days. The Curing methods adopted were the conventional method of water pond as reference and the Wax based Liquid membrane curing compound for research. The superplasticiser based on a polycarboxylic ether polymer with long lateral chains, is used to reduce water cement ratio and to improve the flow ability and filling ability of SCC. The ratio of water to binder is maintained at 0.4. It is observed that a significant loss in strength for High strength concretes of M80, around 25%, at 28 days of Wax based liquid membrane curing to that of Water curing. There is no significant change in compressive strength for the standard concretes of M50 grade using only 53grade OPC at 7 days of membrane curing to that of Water curing, but there is a loss in strength of around 8% at 28 days of membrane curing to that of Water curing. The incorporation of Metakaolin in high strength concretes reduced the percentage loss in strength because of reduced porosity.

Temperature-induced phase and microstructural transformations in a synthesized iron carbonate (siderite) complex

The influence of exposure to high temperatures on the phase transformation, microstructural features, and the resultant mechanical properties of a binder based on carbonation of metallic iron powder is reported. The extent of thermal decomposition of the binder at different temperatures is quantified using thermogravimetric analysis (TGA), whereas Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) are used for the identification of transformed phases. High temperature exposure is observed to result in stable phases, which results in the material retaining structural integrity even when exposed to 800°C, contrary to ordinary Portland cement (OPC) pastes that degrade completely at such temperatures. Significant pore size refinement and a small reduction in porosity are noted when the pastes are exposed to high temperatures. Even though there is a significant strength loss when the iron carbonates decompose (around ~300°C), the strengths are much higher than those of OPC pastes at higher temperatures. This provides an option for chemistry-based design of high-temperature resistant composites as well as develop structural envelope materials especially when prolonged resistance to more than 600°C is desired.

Effect of alkali content of cement on properties of high performance cementitious mortar

The use of very low water-to-binder ratio (w/b) in high-performance cementitious mixtures (HPCM) such as ultra-high performance concrete (UHPC) is gaining popularity. Typically these mixtures consist of Portland cement, pozzolans, water, aggregate, chemical admixtures and steel fiber. The properties of such mixtures including workability, strength, dimensional stability and durability are sensitive to the quality and the proportions of the materials used. In particular, due to high cementitious materials content and low w/b ratio of these mixtures, the alkali content of Portland cement can have a significant effect on the fresh and hardened properties. However, there is limited information available in the literature on the influence of cement alkalinity on the properties of these mixtures. In order to have a closer examination of the influence of alkali content of cement on the properties of such mixtures, a series of Portland cement mortars having a w/c ratio of 0.20 and a range of cement alkali contents were evaluated in this study. The workability, setting time, compressive strength, drying shrinkage, rapid chloride ion penetration, volume of permeable voids and alkali–silica reaction potential of HPCM using reactive aggregate were studied as a function of the alkali content of cement ranging from 0.49% to 0.88% Na2Oeq. The test results showed that when the alkali content of cement was higher than 0.70%, the workability of HPCMs decreased significantly as the alkali content increased. An increase in the alkali content of cement delayed the time of final setting, reduced the compressive strength, and increased the rapid chloride ion permeability, drying shrinkage and volume of permeable voids of HPCM. As the alkali content of cement increased, rapid and significant expansion due to ASR was observed in HPCM, along with significant loss in flexural strength of test specimens, even though the w/c was maintained at 0.20. Identical set of tests were conducted on parallel HPCM specimens containing Class F fly ash as a cement replacement material, and significant differences in results were observed when compared with pure Portland cement mixtures.

The effect of simulated flooding on the structural performance of light frame timber shear walls – An experimental approach

This paper presents the results of a series of tests on timber shear walls exposed to simulated flooding and drying. Load tests were conducted on three wall types; control, wet and restored. The mechanical properties of each of these wall types were compared. It was found that there were significant losses in mechanical strength for the wet and restored walls tested. For wet walls, ultimate strength was reduced by 20% and for the restored walls ultimate strength was reduced by 25%. The restored walls were observed to fail due to sheathing buckling caused by swelling of the OSB during simulated flooding. This failure mode following flooding and restoration is one that is not currently accounted for by design codes or designers.

The role of the P2X7 receptor on bone loss in a mouse model of inflammation-mediated osteoporosis

In inflammatory autoimmune diseases, bone loss is frequent. In most cases, secondary osteoporosis is caused by treatment with systemic glucocorticoid. However, the pathogenesis behind the bone loss is presumed multifactorial.We aimed to elucidate the role of the P2X7 receptor on bone mineral density (BMD), microarchitecture, and bone strength in a standardized mouse model of inflammation-mediated osteoporosis (IMO).In total 146 mice completed our protocol, 70 wild type (WT) mice and 76 P2X7−/− (knockout, KO). BMD at the femur and spine decreased significantly from baseline to day 20 in the WT IMO mice (p<0.01). In the WT vehicle, KO vehicle and KO IMO, no significant BMD changes were found.Bone strength showed a lower mid-shaft max strength (p=0.038) and also a non-significant trend towards lower strength at the femoral neck of the WT IMO group. Trabecular bone volume fraction (BV/TV) and connectivity density (CD) after 20days were significantly decreased in the WT IMO group (p=0.001). In contrast, the WT vehicle and KO vehicle, BV/TV and CD did no change at 20days. Cortical bone revealed no significant microarchitectural changes after 20days in the WT IMO group, whereas the total cortical area increased significantly in WT vehicle and KO IMO after 20days (5.2% and 8.8%, respectively).In conclusion, the P2X7 receptor KO mice did not respond to inflammation with loss of BMD whereas the WT mice had a significant loss of BMD, bone strength and trabecular microarchitecture, demonstrating a role for the P2X7 receptor in inflammatory bone loss.

Distal biceps tendon rupture – Is surgical reconstruction really always necessary?

Summary Background Rupture oft the distal biceps tendon is a rare injury which leads to a considerable loss of supination and flexion strength. A deficit of 40% of flexion and more than 50% of supination strength is reported in the literature. Therefore, surgical reconstruction of the distal tendon is the method of choice. However, some patients opt for non-operative management and a small number of patients are not fit for surgery. The purpose of this retrospective study was to assess the results of non-operative treatment using objective muscle strength testing and evaluation of the subjective satisfaction. Patients and method Between 1999 and 2010, 206 patients had suffered from a distal biceps tendon rupture after trauma. Clinical examination, sonography and MRI confirmed the diagnosis. Most of these patients (85,4%, N - 176) underwent surgical intervention by refixation. 30 patients were treated non-operatively. All these patients were treated with a short-term cast-fixation followed by physiotherapy. The screened patients underwent clinical assessment using a modified Mayo Clinic Performance Index. The supination and flexion strength was measured with an isometric strength test, taking muscle dominance into account. Visual Analogue Scale (VAS) was used for the evaluation of the subjective satisfaction. Results Of the 30 patients who were treated non-operatively 24 (80%) underwent follow-up examination. The mean time between trauma and follow-up was 80 months (18-138 months). A deficit of ROM was only found in one patient. The loss of supination strength was 26,6%, compared to the other arm. Loss of flexion strength was 16,1% -18,1% depending on whether the forearm was in pronation, neutral position or supination. The overall subjective satisfaction for non-operative management was 8,9 for the VAS (10 max). The modified Mayo elbow performing score was 81,05 (90 max). Conclusion In the literature, a significant loss of strength is reported in case of distal biceps tendon rupture. However the evidence for this is sparse. We evaluated more than 20 patients and we found that the loss of supination and flexion strength was not as severe as reported. A high patient satisfaction was found in this study as well. Taking further into consideration the loss of strength after surgical repair with the risk of nerve lesions, non-operative treatment seems to be an acceptable alternative option.

The Hemi-Castaing ligamentoplasty for chronic lateral ankle instability does not modify proprioceptive, muscular and posturographic parameters.

The Hemi-Castaing ligamentoplasty uses a powerful dynamic stabilizer of the ankle which is the peroneus brevis tendon. To our knowledge, there is no study available evaluating the effects of this type of surgery on proprioceptive, muscular and posturographic parameters. This case-control study included 39 subjects divided into two groups: the operated (n = 24) and the control group (n = 15). All subjects underwent a clinical, proprioceptive and isokinetic assessment using a CON-TREX dynamometer, and a postural evaluation using the Win-Posturo force platform. At a mean period of 23 (SD 5.4) post-operative months, the Karlsson ankle functional score was 84.2 (SD 23.8) and the AOFAS score was 88.1 (SD 16.2). The mean ankle joint position error for operated ankles was from 1.9° (SD 0.9) at 10° of inversion range of motion to 2.5° (SD 1.7) at 20°. It was similar to that achieved in the control group ranging from 2.2° (SD 1) at 10° to 2.3° (SD 1.3) at 20°. No significant loss of ankle eversion strength could be observed after ligamentoplasty. Ankle eversion/inversion ratio when tested under all velocities and contraction modes failed to reveal any statistical difference between the operated and healthy ankles in the patient group, neither between the patient and control groups. This surgical technique achieved excellent functional outcomes. It did not impair the agonist/antagonist balance of ankle muscles, and use of half the peroneus brevis tendon did not lessen the eversion strength. Case-control study, Level III.

Swelling of semi-crystalline PVDF by a PMMA-based nanostructured diblock copolymer: Morphology and mechanical properties

The influence of a self-organizing diblock copolymer on the morphology, crystallinity and mechanical properties of a high molecular weight polyvinylidene fluoride (PVDF) is investigated. A spherically organized nanostructured diblock copolymer containing 25 wt% of soft acrylate block and 75 wt% of rigid polymethylmethacrylate (PMMA) is incorporated in PVDF in proportions varying between 12.5 and 70 wt% copolymer. DSC and DMA experiments prove the miscibility of the glassy PMMA block with the amorphous fraction of PVDF, whereas the soft block is fully segregated, preserving the nanostructuration of the diblock copolymer in the blend. Transmission electron microscopy and SAXS experiments show that the copolymer is confined into the inter-lamellar gallery of PVDF, giving rise to a swelling of the crystalline/amorphous lamellar morphology. The long period Lp varies from 120 Å in pure PVDF to 200 Å in the presence of 25 wt% copolymer. WAXS experiments and ATR spectroscopy show that the polar β polymorph is favored in the blends and that the PVDF crystallinity is preserved. Tensile tests demonstrate a large improvement of the elongation at break, without significant loss of strength for samples containing lower amounts of copolymer.

Characterisation of an under-cured epoxy adhesive for use on the riv-bonded Bloodhound SSC lower chassis

Bloodhound SSC is a vehicle that aims to raise the World Land Speed Record to over 1000 mile/h in Hakskeen Pan, South Africa. Its lower chassis is a riv-bonded fabrication made using steel sheet for skins and aluminium alloy machinings for bulkheads. Fasteners alone were enough to satisfy the lower chassis structural requirements; however, Redux 312/5 epoxy adhesive was used to increase the stiffness of the structure and limit potential corrosion due to water and soil ingress. The use of dissimilar metals in the chassis could lead to panel buckling during elevated cure temperatures, meaning a low adhesive cure temperature of 80–90 ℃ was required to minimise this risk. As the cure pressure for the lower chassis adhesive was achieved using only rivets, the variation of cure pressure was experimentally investigated and found to be within the manufacturer’s recommendations for large sections of the lower chassis. Tensile testing indicated the chassis could be cured at 80 ℃ instead of the optimum 121 ℃, without significant loss of mechanical strength. A thermal characterisation of the adhesive was conducted using dynamic mechanical analysis and differential scanning calorimetry. A variety of cure profiles was investigated and resulted in a cure profile that maximised the glass transition temperature ( Tg). An increase in cure duration to 8 h was recommended, which resulted in an increase in Tg by 15–24 ℃ to 83–92 ℃.

Accelerated sulfate attack on mortars using electrical pulse

In this study, the sulfate attack on mortars was accelerated using electrical pulse as an external electrical field. Meanwhile, the specimens with the same mix proportions were immersed in sulfate solution as comparison. The sulfate concentration and mechanical properties, including flexural and compressive strengths, were measured to evaluate the effects of sulfate attack. In addition, the transformation of microstructural nature and phase of the specimens were evaluated by scanning electron microscope and X-ray diffraction. The results showed that electrical pulse greatly accelerated the penetration of sulfate ions into the mortars and resulted in more ettringite and gypsum formed, leading to a greater depth of sulfate reaction. In electrical pulse test, the sulfate content in MgSO4 solution was greater than that in Na2SO4 solution, which was the opposite case in immersion test. Moreover, the electrical pulse resulted in significant mechanical strength losses in a much shorter period as compared with those in immersion test. These findings indicated that the electrical pulse accelerated sulfate attack could be a new acceleration test for evaluating the sulfate resistance of cement-based materials.

Optimization of Pultrusion Process Parameters via Design of Experiments and Response Surface

Experimental designs were implemented to investigate the effects of mold temperature and pulling speed on the tensile strength of cylindrical cables produced by pultrusion. A two‐level factorial design with a central point revealed that the linear model is not applicable for describing the influence of the process parameters on the tensile strength. Additional experiments were performed to investigate the contribution of quadratic terms. A three‐level factorial design revealed that only the linear and the quadratic‐linear interactions can be discarded from the complete quadratic model. In the investigated range of the parameters, the tensile strength always increases with the mold temperature and decreases with the pulling speed. Thus, cables produced at the highest temperature and the lowest speed are the most resistant. Compared with the mold temperature, the pulling speed has a minor influence on the tensile strength. Based on these findings, during periods of higher demand, the pulling speed can be increased without significant loss in tensile strength. For the cases where the tensile strength is critical, the rise in speed can be compensated by a mild increase in temperature. This way, the gain in quality, translated into cables with better resistance, highly compensates for the additional energy consumption. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Bond behaviour of reinforcing bars in cracked concrete

Due to the relatively low tensile strength of concrete, cracks are inherent in reinforced concrete structures. A common cause of cracking is the corrosion of internal steel reinforcement, a deterioration process that can affect the bond behaviour and anchorage capacity of reinforcing bars. Corrosion leads to a reduction of the reinforcing bar diameter, the formation of a weak layer of corrosion products around the bar and expansive forces on the surrounding concrete (that can lead to cracking). In the past, the impact of corrosion on bond has been investigated by means of accelerated corrosion tests. However, the more fundamental impact of cracking as distinct from corrosion products on the bond reduction is still not fully understood.This study applies a novel test method to investigate the bond behaviour of reinforcing bars in cylindrical cracked reinforced concrete specimens. The influence of the number of cracks, crack orientation, confinement and concrete cover are investigated.The results indicate a significant loss of bond strength for single cracked specimens. This reduction becomes as high as 65% for double cracked specimens in the absence of confinement. It is shown that the crack orientation with respect to the rib pattern is of minor influence, but the concrete cover and confinement play a significant role in the obtained bond characteristics.

Strength and Stiffness Degradation of Carbon Fiber Reinforced Plastic under Cyclic Loading under Membran-, Shear- and Bending Loading

In order to meet the increasing lightweight requirements, the application of fiber reinforced plastics is indispensable. To ensure the structural durability of the car or machine under operational conditions, it is essential to know the long term behavior of carbon fiber reinforced plastic material (CFRP) under the numerous influencing factors under fatigue loading. For a reliable safety assessment of the car structure under operational conditions, the degradation of the stiffness and of the static strength after a certain damage due to cyclic loading is of particular importance. The paper covers the loss of stiffness and remaining strength as a function of fatigue damage for specimen and components under membrane, shear and bending loading. The tests are done using different layer set-ups (unidirectional, angle ply, quasiisotropic) and various loading conditions (membrane, shear and bending loading). In order to account for the transferability, the tests are carried out using specimen and components (hat sections). Both specimen and components show a significant loss in strength and stiffness.

Investigation and evaluation of a novel technique on CFRT column connection

This study investigated the effect of an innovative technique, heat treatment, on Q345B steel, which is generally used in China, and the application potential of this technique for H-beam moment connections to concrete filled rectangular steel tube (CFRT) column. A heat-treating process with ultra-high temperature heating and subsequent controlled slow cooling could have a weakening effect on steel strength. The effect of this heat-treating process on steel was investigated through a series of material tests on Q345B steel (Chinese standard). The Chaboche hysteresis material model was selected and calibrated to better describe the strength behavior under cyclic loading, and was then used for subsequent seismic simulations. This technique can be utilized to improve the seismic performance of connections by locally heat-treating the beam section (HBS), and then inducing the plastic hinge away from the critical region. The effect of HBS was investigated on two common CFRT column connections in China, namely, through-diaphragm and internal-diaphragm CFRT column connections. Results showed that the novel heat-treating process also had a significant weakening effect on Chinese Q345B steel. The hysteresis behavior of steel was different from the monotonic performance. The Chaboche model can effectively describe the hysteresis properties. The application of HBS succeeded in inducing plastic strain developed in the heat-treated region, and can reduce strain concentrations without significant connection moment strength loss.

Fracture Analysis of Porous P/M Iron Based Materials&lt;sup&gt;&lt;/sup&gt;

Using powder metallurgy techniques new porous materials for self-lubricating bearings were developed. These materials are characterized by total porosity, which represents their major advantage for tribological applications, acting like their own oil reservoir. Sometimes the presence of pores can be also detrimental to the part performance. Among the causes of the bearings failure is their increased porosity for improving the lubricant retention capacity. Consequently, this can lead to a significant loss in strength. In the present work tensile test specimens based on Fe-Cu/brass-Sn-Pb powders were prepared in order to investigate the morphology of the fracture surfaces and to analyze the effect of pores on the failure process of these materials subjected to tensile loads. Distinct morphologies of the pores area were revealed by SEM images of the fracture surfaces.