Mechanical Strength Of Specimens Research Articles

Microstructure and Mechanical Properties of Sn58Bi Components Prepared by Laser Beam Powder Bed Fusion

As a low melting point alloy, Sn58Bi alloy plays a unique role in many fields. However, the brittleness of Sn58Bi alloy is a limitation that has to be addressed for wider applications. According to previous studies, third element addition is favorable for improved ductility, which is attributable to structure refinement. Therefore, laser beam powder bed fusion technology was adopted to prepare Sn58Bi alloy components. Additionally, the as-printed specimens presented more refined structures compared to the as-cast specimen, so they showed better plasticity. The Sn58Bi alloy showed excellent formability when specimens were prepared by LBPBF between 40–80 W. The density of specimens nearly remained stable above laser power higher than 40 W, and CT scanning could not detect internal defects, so the Sn58Bi alloy specimen was likely to be well fabricated at high laser power. Within the laser power range of 40–80 W, with the variation of laser power or scanning velocity, the laser energy density changed accordingly, and the mechanical strength of specimens was improved with the increase of laser power density. This strength change was probably related to the microstructure evolution and internal residual stress in the printing process.

An Experimental Investigation of Mechanical Properties of Bonded Concrete

This paper presents an experimental study to measure mechanical properties of bonded concrete specimens. The bond between freshly mixed and hardened concrete has been a concern in repair and retrofit projects as well as staged construction of concrete members. This concern has roots in the time-dependent behavior of concrete, beginning with early-age concrete and continuing with long-term performance and durability of concrete. Moreover, environmental conditions generally complicate the behavior of concrete and resulted deformations such as shrinkage and creep. Application of chemical adhesives and epoxies is a common technique to enhance the bond at the interface of old and new concrete elements. The presented methodology includes preparation of bonded specimens with application of grout and adhesive agents. Mechanical strengths of specimens have been reported based on compressive, tensile, flexural, and shear testing. Results indicate that bonding agents are more effective in tensile and shear behavior of bonded samples.

An Experimental Investigation of Mechanical Properties of Bonded Concrete

This paper presents an experimental study to measure mechanical properties of bonded concrete specimens. The bond between freshly mixed and hardened concrete has been a concern in repair and retrofit projects as well as staged construction of concrete members. This concern has roots in the time-dependent behavior of concrete, beginning with early-age concrete and continuing with long-term performance and durability of concrete. Moreover, environmental conditions generally complicate the behavior of concrete and resulted deformations such as shrinkage and creep. Application of chemical adhesives and epoxies is a common technique to enhance the bond at the interface of old and new concrete elements. The presented methodology includes preparation of bonded specimens with application of grout and adhesive agents. Mechanical strengths of specimens have been reported based on compressive, tensile, flexural, and shear testing. Results indicate that bonding agents are more effective in tensile and shear behavior of bonded samples.

Laboratory Evaluation of a Vertical Vibration Testing Method for an SMA-13 Mixture

In order to simulate the on-site compaction conditions of a Stone Matrix Asphalt (SMA) mixture, The Vertical Vibration Testing Method (VVTM), Superpave Gyratory Compactor (SGC), and Marshall method are used to test the SMA-13 mixture, and the physical and mechanical properties of the asphalt mixture designed by these three methods are tested. Subsequently, the influences of the molding method on the mechanical properties are compared. The influence of vibration compaction time on the volume parameters of the SMA mixture is studied. Following the heavy traffic compaction standards, the vibration compaction time of the SMA mixture is determined. The results show that the densities of the heavy Marshall specimen, VVTM specimen, and SGC specimen are 1.018 times, 1.019 times, and 1.015 times greater than that of the standard Marshall specimen, respectively. The passing rate of the 4.75 mm aggregate of the standard Marshall specimen is 29.9%, and that of the VVTM specimen and SGC specimen is 31.1% and 30.5%, respectively, while that of the heavy Marshall specimen is 34.5%. The mechanical strength of the specimen can be greatly improved as the density increases. On the other hand, by the same compaction work, the mechanical strength of the VVTM specimens can be increased by at least 7% compared with the heavy Marshall specimen. The mechanical strength of the VVTM specimen is increased by at least 22% compared with the standard Marshall specimen. The results also show that under the optimal asphalt-aggregate ratio and the same compaction work, the compressive strength and shear strength of the VVTM specimens are increased by at least 6% and 9%, respectively, compared with the Marshall specimens. In summary, the performance of the asphalt mixture designed by the VVTM is superior, providing a wider choice for future asphalt mixture design.

Additional Aging Effect after Carbonation Process of Fly Ash Based Eco-Materials

The purpose of this study is to enhance the mechanical strength of specimens containing fly ash from fluidized bed type boiler, which the recycling rate will be eventually increased. Specimens containing fly ash in a certain portion were made and aged for 3, 14, and 21 days. The carbonation process under the super critical condition was performed to enhance the mechanical property of specimens by filling the voids and cracks existing inside cement specimen with CaCO3 reactants. The additional aging effect after the supercritical carbonation process on mechanical strength of specimens was also investigated by comparing the compressive strength with and without 7 day extra aging. Carbonation under the supercritical condition and additional 7 day aging was very effective for enhancement of mechanical strength and compressive strength increased by 44%, which reached up to 88MPa.

Optimization of injection parameters for mechanical properties of specimens with weld line of polypropylene using Taguchi method

This study optimized effect of injection parameters and weld line on the mechanical properties of polypropylene (PP) moldings. The mold with an insert was designed to create weld line in the experimental specimen. Melt temperature, packing pressure and injection pressure were investigated to study their effects on the mechanical strength of specimens with/without weld lines. Taguchi's L 9 (3 3) orthogonal array design was employed for the experimental plan. Mechanical properties such as maximum tensile load, extension at break and charpy impact strength (notched) of the specimens were measured. Signal to noise ratio for mechanical properties of PP using Taguchi method was calculated and effect of the injection parameters and weld line on mechanical properties was determined using the analysis of variance (ANOVA). Linear models were also created by using regression analysis. The most important parameter affecting the maximum tensile load and the extension at break (for specimen without/with weld line) was injection pressure and melt temperature, and for charpy impact strength (notched) (without/with weld line) was melt temperature and injection pressure, respectively.

A new starch-based binder for metal injection molding

A composition of starch and linear low-density polyethylene (LLDPE) was prepared as the binder and a mixture of this binder with 316L stainless steel powder was used to achieve a feedstock with 57% vol. powder loading. Rheological specifications of the binder and the feedstock were observed by means of capillary rheometery. Pseudo-plastic behavior of the binder and feedstock was investigated as a necessity in metal injection molding (MIM) process by proper flow characterization tests and their viscosity as the most significant flow characteristic was obtained in acceptable ranges. Thermogravimetric analysis (TGA) was carried out on feedstock in order to understand decomposition behavior of the binder components. In the next step, injection molding of the components was successfully conducted. Mechanical properties of compacts were then investigated through the triple point flexure test and the results showed that mechanical strength of specimens are very close to established ranges. The density of green parts was measured to assess the compaction of feedstock and it was achieved within the expected range for ferrous-based feedstocks. Debinding process was accomplished on compacted articles at three different temperature ranges including 70, 80 and 90 °C. Sintering process also was successfully accomplished on samples. For observing microstructures, the surface and cross section of specimens were compared before and after debinding as well as after sintering using scanning electron macrograph (SEM). Generally, this newly developed binder demonstrated a good potential for being utilized in MIM process.

A Study on Reduction of Processing Time and Improvement of Strength by Using Photopolymer Resin in the 3DP Process

3DP(three dimensional printing) technology is one of SFF(solid freeform fabrication) technologies which have recently come into a spotlight due to its adaptability to various applications. This technology has a great advantage in terms of short fabrication time for a prototype at a low cost, especially when it comes with multi-nozzle inkjet printing technology. However, it has also a disadvantage since it requires additional curing time, after jetting a binder material, and post-processing time in order to increase the mechanical strength of a product. In this study, a novel 3DP process is proposed to overcome slow solidification and elaborate post-process by adopting photo curing method into the conventional 3DP process. Mechanical properties, such as tensile and bending strengths, of specimens fabricated with the proposed 3DP process were measured and compared with those fabricated with the conventional 3DP process. As a result, it is found that mechanical strengths of specimens from the proposed novel 3DP process show three times higher than those from the conventional 3DP process. Besides, the overall fabrication time with the proposed novel 3DP process is about two times faster than that with the conventional 3DP process, because it does not need additional curing and post-processing time.

Effects of enzymatic treatments on the biomechanical properties of screws made of bone.

Nowadays, bone tissue employed to manufacture screws used as osteosynthesis material is obtained from organ donors. But in different medical fields there is an increasing need to use xenogenic grafts and implants, which still imply risks of transmission of some diseases and antigenicity. Two different autoclaving programs (A1, A2) and an alternative to reduce the antigenicity of screws made of xenogenic bone based on enzymatic treatment are analyzed from a biomechanical point of view. 128 screws made of bovine femur bone were employed. Some of them were partially demineralized with 0.6 N HCl, enzymatically digested with collagenase (specific) and pepsin (nonspecific) and then autoclaved. The specimens were subjected to tension, shear and screw torque tests and histologically evaluated. Compared to A1, A2 sterilization method (134 degrees C but higher vacuum and longer time) considerably reduced the mechanical strength of specimens. The enzymatic digestion, expected to reduce antigenicity, did not affect the screw superficial structure and would not modify the bone biomechanical properties per se, but maybe because of the association with autoclaving and partial demineralization.

カーボンおよびアラミド繊維クロスを応用した義歯床用レジンの強化に関する研究 第１報 繊維クロスの効果と表面処理について

This study was to investigate the effects of carbon-fiber (CF) or aramid-fiber (AF) cloth application and surface treatment as a means of reinforcing the denture base to the palate of complete upper resin dentures. The CF or AF cloths were incorporated by being sandwiched between the acrylic resin.The mechanical strength of specimens, such as transverse and tensile strengths, were measured and compared with the reinforced specimens and the plain acrylic resin specimens, and the following results were obtained:1. The experiments show clearly that the strength of the reinforced acrylic resin specimens with CF or AF cloth is significantly greater than that of the plain acrylic resin specimens.2. The transverse and tensile strengths of the reinforced acrylic resin containing CF-cloth were improved 11-12 percent and 24-31 percent, respectively, as compared with the plain denture base resin, in the case of the Bis-GMA+3 G or RIPDXY treatment.3. The transverse and tensile strengths of the reinforced acrylic resin containing AF-cloth were improved 12 percent and 33 percent, respectively, as compared with the plain denture base resin, especially in the case of the RIPDXY treatment.

Polymerization of unsaturated novolac ester

THE valuable properties of phenol-formaldehyde resins have been known for a long time and account for their wide application in the various branches of industry. However, certain shortcomings of these resins necessitate their chemical modification and numerous papers deal with this problem (see e.g. [1]). The purpose of this paper was to obtain a modified novolac resin containing double bonds, owing to which the resin should be made capable of hardening during heating without using additives to promote this process. Thus, with resin hardening according to the polymerization mechanism, separation of low-molecular-weight products can be avoided. These form during hardening by the polycondensation mechanism, disturbing the solid structure and reducing the mechanical strength of specimens. I t can be expected at the same time that shrinkage, during polymerization of such modefied resins, will be very low which is characteristic of the polymerization of oligomers [2]. We modified novolae resin by esterification with acid chloride of methacrylic acid (ACMA) of the phenol hydroxyl resin groups according to the scheme: